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## Inhaltsverzeichnis

### 1. Uber den raumladungsbegrenzten Influenzstrom in einer ebenen Diode bei grossen Signalen und langen Elektronenlaufzeitwinkeln unter Berücksichtigung von Sekundaremission der Elektronen

Bei der theoretischen Untersuchung des elektronischen Verhaltens von Senderöhren vom Typ Triode resp. Tetrode bei langen Elektronenlaufzeitwinkeln kann man den Gitter-Katodenraum dieser Röhren als Diode betrachten, welche unter raum1adungsbegrenzten Bedingungen arbeitet. Wir wollen im Folgenden über eine theoretische Arbeit berichten, welche sich mit einer derartigen Diode beschäftigt. Die untersuchten Betriebszustände (C-, B- und j4B-Einstel 1 ung) sind entsprechend den gebrauchlichen Einstellungen von Senderohren gewählt. Die gewonnenen Resultate können den Ausgangspunkt zur Berechnung des el ektronischen Verhaltens von Trioden und Tetrodenhi1den.

K. W. Hinkel

### 2. A quarter-wave coupled three Esaki diodes microwave amplifier

There are many reports on the anplifier using Esaki diodes which is a well known high frequency low noise device. The anplifier nay be classified into two types, one is a reflection type and the other is transnission type. The latter has a nerit of operation without a circulator.

Yasuharu Sueraatsu, Takuo Muratani

### 1. The influence of space-charge and geometry on the efficiency of a two-cavity-klystron oscillator

Since the invention of the klystron generator by Arsenjewa-Heil and Heil [l] in 1935 there appeared many papers on the theory of this device. Nonlinear analyses were limited to models with zero space-charge forces 2, 3, 5, 11 or to one-diraensional models 5, 11. In the two-dimensional klystron theories of Webber [10] and Paschke [8] feedback was not treated. In the one-dimensional model, however, the range of the space-charge force is unlimited for the electric field of an infinitely broad bunch does not decay in axial distance from the bunch. In practice, the range of the space-charge force is limited because of the finite 1 ateral dimension of beam and drift tube. At small signals there is, except for the existence of higher order modes in finite beams, only a quantitative but not a qualitative difference between the con-vection-current distributions of finite and infinitely broad beams; the reduction of the range of the space-charge force is associated with a reduction in plasma frequency. At large signals, however, there is also a qualitative difference which is evidenced by the experiments of Mihran [6], [7]. The physical reason for this difference is due to the dispersion of the space-charge waves. In a one-dimensional beam the plasma frequencies corresponding to fundamental and harmonic signal frequencies are identical. For this reason mixing can produce only mul tipies of the plasma frequency. Thus the periodicity of the convection-current distribution found at small signals is maintained up to large signal levels. In a finite beam the plasma frequencies corresponding to the harmonics differ from the plasma frequency corresponding to the fundamental signal frequency; furthermore, the ratios of these plasma frequencies are, in general, irrational numbers. At large signals the convection current therefore becomes a non-periodic function of distance.

F. Paschke

### 2. Parallel operation of pulsed broadband klystron amplifiers

The operation of two or more amplifiers in parallel withacommon driving source can be used to increase the power output available from a single valve, or to maintain transmission at a reduced level in the event of a valve failure. Paralleling at a single frequency is straightforward, requiring one phase adjustment to optimise the power into the aerial arm of the combining device.

N. E. Dixon, P. S. Matthews

### 3. Perfectionnements aux amplificateurs de puissance à klystron

L’emploi de la modulation d’amplitude dans les systèmes de transmission fonctionnant en ultra-haute-fréquence se heurte souvent à des difficultés dues à l’introduction des distorsions non-linéaires par l’étage de puissance de l’emetteur. C’est le cas, par exemple si l’on veut transmettre en bande latérale unique, ou en bande latérale double avec onde porteuse supprimée, un signal multiplex à répartition de fréquence. Certains procédés de linéarisation de la caractéristique du gain des amplificateurs de puissance à klystron ont été étudié à cet effet. Ils sont basés sur l’utilisation de dispositifs a contre-reaction d’enveloppe de types particuliers.

R. Astor, J. Cayzac

### 4. An electrostatically focused klystron amplifier

The role which the klystron amplifier is playing in the field of radar, communications and other systems such as linear accelerators has proven this device to be invaluable. Because a klystron is a device employing a long and slender electron beam, a means of focussing this beam becomes necessary. In practice, this focussing is accomplished with either permanent magnets or electromagnets. Both have their disadvantages. Magnets are not only heavy, bulky and have stray magnetic fields, but also add to the initial cost of a system. The electromagnet, in addition, requires a power supply which reduces the overall efficiency of the system and is also inherently heavy and bulky. The use of aluminum wire and foil for the electromagnet winding has not significantly reduced the weight and size. The elimination of focussing magnets would, therefore, be highly desirable. This is especially true, if not mandatory, in mobile, airborne and space systems where space and available power are at a premium and weight must be kept at an absolute minimum.

J. R. Hechtel, A. Mizuhara

### 5. Multipactor motions in Microwave tubes

Secondary electron resonance, or multipactor, has been studied in many places during the last 20 years as a laboratory phenomenon but little has been published, and less has been said in meetings such as this one, about multipactor in tubes.

Donald H. Preist

### 6. Stabilized high-power klystron oscillator

Multicavity high power klystrons are widely used as amplifiers today. We have found it possible to operate a klystron as a stable self oscillator tube, at high efficiency when

Y. Yoshida, Y. Watanabe

### 7. A high-power floating-drift-tube klystron

At the present time, engineering interest is not very active in po wer-oscil lator klystrons. A few years ago, however, considerable work was done on the klystron oscillator, and the tube I shall describe, represents, I think, the highest power klystron deliberately designed to oscillate.

R. B. Nelson

### 8. Hollow-beam klystron with modulating anode

Klystron amplifiers have proven to be readily adapted to long pulse operation by means of a modulating anode. Several tube designs have been developed in the past which incorporated guns of the modified Pierce type wherein the anode is isolated from the body of the tube and designed such that it selves as a control electrode to switch the beam current on and off. Generally speaking these tube designs have proven successful. Modulating anode-type tubes can be built which minimize the intercepted current on the isolated anode thereby reducing the amount of power required for the pulser or modulator.

James N. Lind

### 9. A broadband megawatt hollow beam multicavity klystron

In recent years there has been a great interest in incorporating a hollow beam in high power klystron devices. This interest is based on the fact that with the higher perveance achievable with a hollow beam, lower operating voltages would be necessary and a, larger bandwidth could be achieved.

Lindsey B. Anderson, Abraham Bers

### 1. A 2-kilowatt CW travelling-wave tube for C-band communications

Satellite communications systems have recently provided an application for high-power CW travelling-wave tubes. In this paper we describe the transmitter power amplifier tubes now operating in the American and French ground stations which are in communication via American Telephone and Telegraph Company’s Telstar satellite. The tube has been designed for a reasonably broad bandwidth of ~13% centered at 6100 Mc/s. The output power is in excess of 2000 watts and the high-level gain is better than 27 dB over this band.

R. J. Collier, G. D. Helm

### 2. A high-power travelling-wave tube for the frequency range:5,9 to 6,7 KMC/S

The object of this paper is to describe some particular features of a developmental O-type travelling wave tube for 6 kmc/s links. The tube is calculated to give a small signal gain of about 30 dB at a c.w. output power of 2 kW.

R. Liebscher, E. Mayerhofer, P. Meyerer, R. Stock, A. Kraus

### 3. A high-power travelling-wave tube for C-band

It is our purpose in this pape:r to describe succinctly the design, construction and performances of a high-power travelling wave tube for C-band.

G. Dube, P. Palluel

### 4. The design of a 100 MW. 400 MC/S pulsed travelling-wave tube

It has been predicted (Rowe 1962) that the efficiency of a Travel1ing-Wave Tube should increase rapidly as the velocity of the beam-wave interaction approaches the velocity of light. For example at a velocity of 0.8 c, which is equivalent to a beam voltage of 370 kVf an efficiency of 70% should be obtainable. Fig. 1 shows a section of the pulsed travelling wave tube being built at S.E.R.L. which it is hoped will test this prediction.

A. J. Monk

### 5. The design of a 250 KW 400 MC/S travelling wave tube

This account concerns the development of a travelling-wave tube which is unusual in a number of respects.

C. H. Dix, T. J. Lane

### 6. Some experiments on the effect of a circuit sever on high-power travelling-wave tube efficiency

In order to avoid an excessive amount of feedback in a high gain travelling wave amplifier, caused by internal reflections, sone form of r.f. isolation in the slow-wave structure is needed. In high power tubes such isolation is usually provided by introducing one or more breaks, or severs, in the structure. At these severs any circuit power is dissipated in resistive loads and the signal is propagated solely as current and velocity modulations on the electron beam.

M. O. Bryant

### 7. Resonant circuit oscillations in travelling-wave tubes

Stability remains one of the most difficult problems in the design of high power travelling-wave tubes. Stability problems are also encountered in the design of low power tubes, but it is usually possible to predict the instabilities and obtain a stable design without seriously compromising gain and efficiency. However, in high power tube designs, instability can result in a limited active circuit length, thereby limiting each individual circuit gain to a value seriously affecting tube efficiency [1]. Obviously, the stability factor can limit the number of applications for high power travelling-wave tubes.

J. A. Ruetz

### 8. High-power, CW millimeter-wave amplifiers and oscillators

About two and one-half years ago a programme was initiated in our Laboratories to devise efficient high-power millimeter-wave generators. It was believed that ultimate practical utilization of these devices dictated the use of low voltage and made achievement of maximum efficiency and minimum weight of prime concern. Air cooling was also specified for the same reason. Cw operation was chosen because it was believed that the problems in this mode were more severe than those in pulsed devices and also that many of the early applications of millimeter waves might be in cw communications systems. Although some consideration was given toother approaches, it was decided very early that the linear beam or O-type of distributed interaction tubes offered the most promise of realizing our obj ecti ves.

D. C. Forster, J. E. Nevins, M. R. Currie

### 9. A low-noise travelling-wave tube for 26.000 -40.000 MC/S

The mechanical problems associated with the design of travel 1 ing-wave tubes becom.e more acute as the frequency increases. This is because the small clearance between the beam and slow-wave structure implies that the mechanical straightness of both the travelling-wave tube and the focusing magnetic field must be unusually good at high frequencies, and also because where dielectric materials are associated with transmission lines they must be reduced to very fragile dimensions, in particular the relatively simple glass envelope construction of lower frequency helix travel1ing-wave tubes becomes difficult in Q-band because the glass envelope is either so thin that it will not maintain straightness and resist air pressure, or so thick that wave-guide modes are able to occur either in the interaction region or near the waveguide-to-helix couplings.

J. M. Winwood

### 10. Un tube à onde progressive à faible facteur de bruit dans la bande de 85 GHz

Un tube amplificateur à onde progressive à faible facteur de bruit fonctionnant autour de 85 GHz est actuellement en cours d’étude à la CSF.

P. Delphin

### 11. AM-to-PM conversion and AM-compression of travelling-wave-tube amplifiers

It is well-known that if an amplitude modulated signal is applied to the input of a TWT amplifier, the output signal will show also phase modulation. The ratio of the output signal phase modulation to the input signal amplitude modulation is called AM-to-PM conversion. Another important characteristic of the TWT amplifier is the AM compression, giving the ratio of the output to the input signal amplitude modulations. The determination of these two parameters by measurements is of great importance if the TWT amplifier is applied in a long-distance multichannel microwave link.

T. Berceli, T. Sárkány

### 12. Calculations concerning the properties of E-type travelling-wave amplifiers with arbitrary signal level

This paper will report on some results concerning E-type amplifiers. In these amplifiers the electrons travel along helical paths and interact with a helically oropagating slow wave (Fig. 1). Neglecting space charge, the distance r_ from the axis ann the d.c. velocity of the equilibrium path, r_Θ_, are determined by the radii and the potentials of the inner ana outer electrodes. For a high efficiency, the inner electrode is to be utilized as the slow-wave structure, not the outer electrode as formerly [l] suggested. The outer electrode is at cathode-or at a negative potential, similar to the sole in M-type tubes.

K. Poschl, H. J. Linn

### 13. The travelling-wave amplification as a parametric process

The Manley-Rowe relations [1] were originally developed in an analysis of a circuit containing nonlinear reactive elements. Since the original discovery of this important formula, it has been found that there are a number of other physical systems that obey the Manley-Rowe relations. Penfield [2] and Sturrock [3] have shown that any physical system that can be described by energy-state functions obeys the Manley-Rowe relations. Jaynes [4], Weiss [5] and others pointed out the similarity between the Manley-Rowe relations and the well known quantum mechanical expression W = ħω, and noted that the Manley-Rowe formula is indeed equivalent to the conservation of quanta. On this basis, Jaynes [4] was able to establish the similarity between masers and parametric amplifiers.

S. F. Paik

### 1. Spurious phenomena in “M” type tubes

Most if not all spurious phenomena taking place in ‘M’ type tubes: parasitic oscillations, frequency jumps in ‘M’ type carcinotrons, excess noise, seem to originate from two sources: The excess noise created in the gun region.The modulation of the beam in the gun region by the r. f. field radiated from the delay structure, mainly at the ends of it.

J. Arnaud, F. Diamand, B. Epsztein

### 2. Sur trois modèles de carcinotrons “M” de grande puissance

Le tube fonctionne aux alentours de 0,60 mètres, les performances demandées sont: 25 kW entre 390 et 560 Mc/s.

G. Mourier, J. Nalot, W. Sobotka

### 3. High-power T. P.O. M. amplifiers

The TPOM, which is a forward wave crossed field amplifier, is characterised by a wide bandwidth, a relatively high gain and a notable efficiency. The pulsed tube is! suitable for obtaining peak powers of several megawatts and average powers of several tens of kilowatts. It works at low voltage and high current if compared to solid beam klystrons or travelling wave tubes, has a good phase stability, and satisfies the following features: the current is obtained from an injection gun; the non-reentrant beam needs the use of a col lector; the delay structure which has good, thermal dissipation properties is, for some tubes, even cooled by means of a liquid; but in fact in the pulsed TPOM’s developed for ‘L’ and ‘S’ bands the limits of the performance charts come from two factors which are the low beam impedance and the r. f. power of slow or fast waves existing in all the parts of the tube where an electric field is applied: namely the gun, the sole to line gap, the collector. This appears as oscillations, noise and voltage breakdowns, and limits the gain, the bandwidth and the maximum peak power.

G. Kantorowicz, J. Nalot, P. Vial

### 4. Experiments with a pulsed L-band coaxial M-carcinotron with azimuthal magnetic field

Fig. 1 gives a somewhat simplified presentation of the construction of the tube used in the experiments.

### 5. The coaxial crossed field tube

In the coaxial crossed field tube**the magnetic field is not uniform but created by a large current flowing in a cylindrical rod; the delay line and the sole are also coaxial cylinders. Two possibilities exist: the delay line may be the inner or the outer conductor; in the ‘L’ band and at higher frequencies the size of an inner delay structure would involve too large a current; this solution would be interesting only for lower frequencies. The tube which will be described here is an experimental pulsed forward wave amplifier operating in the ‘L’ band; it is designed to give an output power of 0,6 MW; the beam impedance is very low, the cathode current being 53 A for a cathode vol tage of 28 kV; it results from this, that the delay ratio is unusually high for this peak power: it is 13 in the middle of the band. The copper stub in which the current flows constitutes also the sole the diameter of which is 14 mm. The line diameter is 32 mm and its length is 64 cm or 39 delayed wavelengths.

J. Arnaud

### 6. Backward-wave tube feedback oscillators

The backward-wave oscillator which has been used mainly for test equipment and radar use, is considered inferior to the klystron for communication use, because of its instability.

K. Kakizaki

### 7. Studies on C.W.-magnetron amplifiers with continuous cathode and re-entrant beam

Magnetron amplifiers with cylindrical cathode and re-entrant beam form a new class of power amplifiers, which is not very well explored as yet. Their simple construction and high efficiency, however, make them appear very attractive from a technical viewpoint.

H. Steyskal

### 8. Large signal calculation of amplitron performance

A space charge analysis of the Amplitron is considerably more difficult than that of the magnetron because a frame of reference cannot be found which renders the flow time-independent. Moreover, while considerable progress has been reported at this Congress regarding tne use of high speed computers in the self-consistent field method of electron gun analysis, even after a major effort this method has not given a solution to the space-charge-Iimited magnetron. In view of these obstacles the analysis of the Amplitron has been performed in a much less rigorous manner.

G. E. Dombrowski, T. E. Ruden

### 9. The S-F-D crossed-field amplifier

Continuous cathode crossed-field amplifiers with re-entrant electron clouds have in the past been restricted to a relatively small number of resonator cells. This has been due to the requirement that the phase of the signal fed back from output to input via the circulating space charge be within about ± 90° of positive feedback. As a result the maximum allowable number of cells for a given percentage bandwidth was given by NΔθ = 180°; where Δθ is the variation in phase shift per cell across the band and N is the number of cells. Thus for Δθ = 10°, a typical value for a 10%, bandwidth tube, the maximum number of resonator cells is 18.

H. L. McDowell, J. Feinstein

### 10. Recent advances in non re-entrant crossed-field forward-wave amplifiers

Since the late 1940’s when the first significant work was done on crossed-field amplifiers [l], they have generally had the reputation of being relatively low gain devices. Until recently, most of the work or this type of device has been done on tubes of circular format which suffer from problems of gain stability because of the many modes of electromagnetic and electronic feedback from output to input. Recent work on the linear form of the injected-beam forward-wave crossed-field amplifier has greatly reduced the problem and promises to put this device into the high gain class along with klystrons and traveling-wave tubes. Noise on the beam will be the chief limiting factor in the gain attainable in crossed-field amplifiers. Recent tests have shown that at least 40 dB gain can be achieved before such effects become notice-abl e.

J. F. Hull, G. E. Pokorny, G. P. Kooyers, P. N. Hess, E. K. Shaw

### 11. An empirical solution to the steady state magnetron space charge distribution

The space charge distribution in the steady state magnetron is an old problem. Many solutions have been proposed since its invention although none of them is entirely satisfactory. A reasonable description of the magnetron space charge cloud, we believe, must at least satisfy two conditions. First, it must be consistent with the fact that electrons can reach the anode when the anode voltage is below cut-off. Second, the drift velocity of the electron cloud must agree with the well-known starting condition. The second condition, which is often overlooked, will be explained in slide 1.

S. P. Yu

### 12. Pulsed magnetrons for 4 and 2.5 MM wavelength

In the Philips Laboratory a range of pulsed magnetrons [l] has been developed chiefly with the aim to attain the shortest possible operating wavelength with the aid of these conventional tubes. The tube with the shortest wavelength in this range is a magnetron for 2.5 mm wave-length. In this paper we shall give the most significant data of this 2.5 mm tube and those of its predecessor, a magnetron for 4 mm wave-length. One particular aspect of this development will be considered in more detail.

G. H. Plantinga

### 1. Non-degenerate electron-beam parametric amplifiers

Ever since the Electron Beam Parametric Amplifier (EBPA) first became known, there has been substantial interest in the development of a nondegenerate version. The low-noise EBPA’ s now in use are degenerate or near-degenerate amplifiers;. the pump frequency which they employ is very nearly twice the signal frequency, with the resul t that an idler near the signal frequency is generated. In some situations this is harmless, but generally it represents a handicap. Solid-state diode amplifiers are usually nondegenerate, with a pump frequency many times higher than the signal frequency; an electron beam device employing such a frequency combination would have obvious advantages over its degenerate counterpart.

### 2. On the excess noise in Adler tubes

This paper describes an experimental investigation into the causes of excess noise in the quadrupole electron beam parametric amplifier, the so-called Adler tube [l].

G. O. Chalk, A. Frohlich

### 3. Interception, scattering and multivelocity effects in a transverse-wave electron beam

Partial interception of the electron beam and some scattering associated with this interception occurs frequently in transverse-wave tubes. In many cases the electron beam employed is a low voltage beam, which means that the spread in axial velocity is not always negligible. There appears to be quite a degree of similarity between the ultimate effects caused by interception, scattering and multivelocity effects despite their different physical sources. Frequently they also occur simultaneously.

P. A. H. Hart

### 4. Etude d’un tube paramétrique à faisceau

Le but de cette étude est la réalisation d’un tube paramétrique a faisceau utilisant les ondes cyclotrons. Ce tube pour son principe est identique aux tubes d’Adler et de Bridges et Askin; il n’ en diffère que par la fréquence d’utilisation, ce qui a entraîné une construction différente des coupleurs d’entrée et de sortie.

Martinot Lagarde

### 5. Parametric refregeration discussion and experimental verification of the removal of slow-wave noise

It was for some time believed that it is impossible to remove noise from the slow waves of an electron beam [1]. Since the operation of a large class of microwave amplifiers depends on the coupling of the negative energy slow wave to a circuit, this belief led to the statement of various minimum noise figure theorems [2]. As a result of these theorems, much effort has been expended on the development of amplifiers which use the fast beam waves [3]; these waves may, in principle, be stripped of all emission excited noise.

P. A. Sturrock, G. C. van Hoven, A. Karp

### 6. The parametric reduction of the amplitude of slow space-charge waves in an experimental device

At the 1960 International Congress on Microwave tubes held in Munich, Sturrock [l] proposed a scheme for using the principle of parametric pumping to reduce the slow wave noise in an electron beam. This mechanism could be used, for example, as the basis of a low noise travelling wave amplifier. Since the slow wave is a negative a. c. power carrier, the slow wave noise cannot be removed from the beam by direct coupling to a matched resistance.

M. C. Davies, K. T. W. Milne

### 7. Quantum statistical properties of ideal phase sensitive receivers

There has been a great deal of work done in the past on, the quantum statistical properties of noise in linear amplifiers and attenuators. However, a complete statistical description of these devices for an input consisting of a signal plus Gaussian noise does not seem to be contained in the earlier work.

W. H. Louisell, L. R. Walker, J. P. Gordon

### 8. D.C. -pumped cyclotron-beam tubes using quadrifiliar helix

This paper deals with the operating characteristics evaluation of two types of d.c.-pumped cyclotron beam tubes, LD-511D and LD-511E, which are developed for a high gain tube. In these tubes quadrifilar helix is used as an amplifying element.

Shigebumi Saito, Masamichi Kenmoku, Toru Matsuoka

### 9. Theoretical and experimental investigation of D. C.-pumped cyclotron-wave amplifiers

During the past two years d.c. pumped cyclotron wave amplifiers have been studied extensively. In these tubes amplification takes place by coupling positive and negative energy cyclotron beam waves in a spatially periodic transverse field electrostatic or magnetic structure.

J. C. Bass, D. C. Rickard, M. G. F. Wilson

### 10. A D.C. -pumped coupled mode parametric amplifier with depressed collector

It was suggested by Gould and Johnson [1] that an interesting amplifier would result from the coupling of the fast cyclotron wave with the slow synchronous wave by means of an axially symmetric electrostatic pump field. After removing the fast cyclotron wave at the output coupler, the spent beam would consist of the slow synchronous wave which would have uniform axial velocity and no rotational velocity. Thus, a depressed collector could be effectively employed and very high values of efficiency would result. Their work was based on a filamentary electron beam and a linear approximation of the electric field which is valid near, the axis.

James E. Dalley, C. C. Johnson

### 11. Cyclotron wave amplification using simultaneous R. F. -coupling and D. C. -pumping

Parametric amplification using an electron beam as a parametric medium was studied by many researchers in the past years. Both longitudinal beam waves and transverse beam waves have been utilized, but only the fast transverse cyclotron wave provides good performance. The fast cyclotron wave was successfully used by Adler, Hrbek and Wade [1], [2] with r.f. pumping. The signal mode is a fast cyclotron wave which is actively coupled to an idler mode (also a fast cyclotron wave) by the pumping action of a high frequency transverse electric quadrupole field oscillating at twice the cyclotron frequency. Cyclotron waves can also be amplified by d. c. field pumping as pointed out by Gordon and others [3], [4]. A wave analysis showing clearly the‘processes occurring in these devices was introduced by Siegman [5], [6]. The signal mode is also a fast cyclotron wave as in the Adler-Wade tube. But the signal mode is now actively coupled to a slow cyclotron idler mode by the pumping action of a d.c. transverse electric quadrupole field. Later Wessel-Berg and BlQtekjaer studied the coupling between cyclotron waves and synchronous waves by axial symmetric and spatially periodic electrostatic or magnetostatic fields, and the coupling between two synchronous waves by d.c. electric field of straight quadrupoles [7]. [8].

S. Mao, A. E. Siegman

### 12. Minimum noise temperature of transverse-wave D.C. -pumped electron-beam amplifiers

The low noise temperature of the cyclotron wave amplifier, often referred to as the Adler tube [l], is achieved by means of parametric amplification of the fast cyclotron wave which can be cooled prior to the amplification. This is done in the input coupler which serves the double purpose of stripping the positive noise power associated with the fast cyclotron wave off the beam and that of coupling the signal on to the beam.

T. Wessel-Berg, K. Bløftekjaer

### 13. Amplification of the tranverse waves of an electron beam in space -periodic magnetic-field jumps

In recent years electron beams with transverse modul ation have been appl ied for the amplification of microwave power. In a special variety of these amplifiers the electron beam passes a spatially variable static electric or magnetic field [l], [2], [3], [4], [9]. Transverse waves which propagate on an electron beam can be assumed to be independent of the space charge for beam deflections that are small with respect to the wavelength. Thus the model concept of a filamentary beam suffices for a description of such waves. The electron beam is here thought of as composed of disks without longitudinal coupling that have a diameter which is small compared to the wavelength. The center-of-mass trajectories of these disks behave just like the trajectories of individual electrons and suffice for a presentation of the waves [l].

Horst Seunik

### 14. An experimental investigation of transverse-wave interaction in periodic magnetostatic fields

Interaction between transverse electron beam waves in so-called pump structures has been studied theoretically by several authors. Analysis has shown that there exists a number of interaction schemes involving the cyclotron waves and synchronous waves. The nature, of the interaction depends on the details of the pump field. Although the theory is far from complete, it describes the fundamental properties of the various interaction schemes. However, the theoretical work has not been followed up by experiments. The quadrupole structure used in the Adler tube is the only pump which has been thoroughly investigated experimentally [1], [2], [3]. Some electrostatic and magnetostatic pump structures have been shown to operate, but no systematic investigation of their performance under various operating conditions has been carried out [4], [5], [6], [7]. The possible advantages of transverse modulation as compared to longitudinal modulation is far from being utilized in practical devices.

K. Bløtekjaer, B. Malsnes, A. Nordbotten

### 15. Improvement of the stability of parametric amplifiers

There are not a few problems on the practical applications of cavity type parametric amplifiers, but improving their performance reliability may be one of the most important. Especially needed is a much better stabilization of gain performance.

Takashi Kitsuregawa, Kiyoshi Shirahata

### 16. Etude et réalisation d’ un amplificateur paramétrique à ferrite

Il est maintenant bien connu cine la précession uni forme de l’ aimantation M soumise à l’ action combinée d’un champ continue Hc et d’un champ alternatif de haute fréquence h peut constituer la genèse de différents types d’ amplificateurs à condition que des phenoménès de non-linéarité accompagnent cette précession unifome de M.

H. Le Gall, A. J. Berteaud

### 1. A study of the plasma travelling-wave amplifier

Slow space charge waves can propagate in a magneto-plasma contained within a waveguide envelope. Preliminary results have already been reported showing that microwave amplification is possible when an electron beam interacts with such a system [1]. In these experiments the plasma was produced by the electron beam itself ionizing a low pressure filling of hydrogen in a waveguide of circular cross section which, when empty, was cut off to the applied signals. The present paper is a brief report of quantitative measurements made on the amplifier and their relation with some new expressions for the performance of the device. A fuller account will be published elsewhere.

P. B. Curtis, R. L. Ferrari

### 2. Some aspects of the interaction of an electron beam and a plasma

In recent years much attention has been paid to the interaction of an electron beam andaplasma. Due to this interaction amplifying waves and non-convective instabilities can occur [1] -[4]. This provides a possible method of heating a plasma by converting d.c. energy of a beam into thermal energy of a plasma [5].

M. T. Vlaardingerbroek, K. R. U. Weimer

### 3. Electron beam-plasma interaction

The first conclusive experiments demonstrating microwave amplification when an electron beam is passed through a plasma were carried out in 1957 by Boyd, Gould and Field [1]. These authors demonstrated that there is gain below the plasma frequency, reaching a maximum at the plasma frequency. The theory they used predicted extremely high values of gain, much higher than were observed experimentally, the maximum value of gain being limited only by thermal effects and collisions of the electrons with neutrals and ions.

M. A. Allen, G. S. Kino, J. Spalter, H. L. Stover

### 4. Normal mode theory for electron-beam plasma amplification

When an electron beam is passed through a plasma and modulated by a high frequency signal, there will be modes of propagation along the beam plasma system which have large growth rates. This phenomenon was first demonstrated by Boyd, Field, and Gould [1]. Since that time, the modes of a finite beam passing through a finite plasma column in the presence of a finite magnetic field have been analysed by Bogdanov et al [2] and Allen et al [3, 4].

M. Chodorow, J. C. Eidson, G. S. Kino

### 5. Millimetre wave harmonics from a gas discharge

Earlier work at several laboratories has shown that in the centimetre wave band a microwave gas discharge is a fairly efficient and prolific harmonic generator [1], [2], [3], [4], but that at millimetre wavelengths the efficiency is very small [5], [6].

D. J. Knight, D. Walsh

### 1. Generation of millimeter-waves by means of electron beam cyclotron resonance

We had already held an experiment of the millimeter wave oscillation using the interaction between an M type cyclotron fast wave in an electron beam and a TEM wave on a strip line with a demountable device. The oscillation wavelength was varied in stepwise from 8.9 to 6.4 mm by changing the magnetic field and the output power was 50 mW at λ = 8.4 mm and 35 mW at λ = 6. 4 mm [1]. The interaction process had been investigated analytically and experimentally [2].

Y. Suematsu, H. Isobe, A. Azumi

### 2. A fast oscillator using cyclotron resonance

The use of the cyclotron motion of free electrons inamagnetic field as a source of high frequency oscillations has been discussed for many years, and some experimental success has been achieved [1] [2] [3]. The present paper follows two previous ones, the first of which [4] gave a ballistic theory for the interaction between the electron motion and an r. f. electric field for a number of geometries while the second [5] described an experiment in the two centimetre wavelength region using a crossed field geometry. This experiment showed that the expected oscillation mechanism existed, but that the cathode emission had to be temperature limited and that the power outputs obtainable were only milliwatts. We shall now discuss the reason for this behaviour and describe an electron beam injection system which enables stable space charge limited operation to be achieved, giving an output of tens of watts and making possible more detailed comparison with the theory.

D. M. Stevenson, A. Reddish

### 3. Cyclotron fast-wave tube using spatial harmonic interaction — the travelling wave peniotron

This is one of travel ling-wave tubes having no slow wave circuit.

Shoichi Ono, Kazuhiko Yamanouchi, Yukio Shibata, Yujiro Koike

### 4. A cyclotron resonance frequency multiplier

A cyclotron multiplier was first proposed by Cuccia in 1949. The principle on which such a device depends can be seen in Pig. 1.

J. Dain, R. R. Thompson

### 5. Theoretically predicted characteristics of the “EAL” or electromagnetic amplifying lens

The ‘EAL’, or Electromagnetic Amplifying Lens [1], is a new member of the magnetron family. It is mechanically long in the axial direction, giving higher power capability than the conventional magnetron. It is at the same time electrically long resulting in axial gain. The EAL may be classed as a crossed-fiel d waveguide amplifier. It may also be thought of as a locked oscillator having its output at one end of the waveguide, being controlled by a small signal applied at the other. Part of the significance of the EAL lies in the design of the r.f. pa.th through the device. As in Pig. 1, the input coupling is treated as a metallic lens; the interaction circuit and output coupling are considered extensions of this lens. Application to millimeter wavelengths thus becomes attractive.

George E. Dombrowski

### 6. TheUbitron as a high-power millimeter wave amplifier

The Ubitron is a traveling-wave amplifier based on the interaction between a 1arge-diameter magnetically undulated electron beam and the TE01 mode in circular waveguide. The interaction, is of the periodic beam type, which is sometimes referred to as ‘fast wave’ because the coupling of the beam and r. f.-wave can be obtain ed without slowing the phase velocity of the wave to less than-the velocity of light. The simplicity and large physical size of the r.f.-circuit used in the Ubitron and the large diameter of the beam make the tube extremely attractive for high pulsed power at millimeter and sub-millimeter wavelengths. The circuit diameter is an order of magnitude greater than that of the conventional traveling-wave tube (ka is about 4 compared with 0.4 for conventional tubes). With this size advantage one can expect to obtain the same order of magnitude of power at 100 Gc/s from a Ubitron as one would obtain at 10 Gc/s from a conventional TWT. Experimental results obtained at K -band lend credence to this comparison.

R. M. Phillips

### 7. Production of a highly bunched electron-beam for a submillimetre wave undulator

In order to generate sub-millimeter waves in a magnetic undulator more efficiently than has been possible hitherto, an electron linac has been proposed which will provide a 2-MeV beam of tightly bunched electrons for injection into the undulator.

A. J. Lichtenberg, M. E. B. Moffat, H. Motz

### 8. Coherent Cerenkov radiation produced by a bunched electron beam traversing a plasma and ferrite medium

A somewhat surprising feature [1] of past work on the Cerenkov effect is that it is almost all theoretical with a restricted amount of numerical analysis. The limited experimental work has undoubtedly contributed to the belief that the Cerenkov interaction is weak and hence a high efficiency device could not be achieved using this effect.

Paul D. Coleman

### 9. A new type Cerenkov generator theory and experiment

Recent technological advances, particularly those in space, are taxing the ingenuity of scientists for the development of r. f. generators with large power outputs and high efficiency. Certain aspects of Cerenkov radiation, heretofore unexplored, seem to offer attractive possibilities for satisfying both of these demands.

J. M. Brumbaugh, L. J. Nicastro, J. Vollmer, L. W. Zelby

### 10. A rigorous large-signal analysis on harmonic generation using parametric diodes

The nonlinear interaction of parametric diodes with circuits for harmonic generation has been analyzed by approximation [1] based on a small-signal theory. However, this interaction has not been fully explored under large-signal conditions which are in practice for many recent high-power applications.

K. K. N. Chang, P. E. Chase

### 11. The backward-wave converter

This paper describes the development of a backward-wave converter which is a hybrid device that combines the essential elements of an electronically swept receiver in a single vacuum envelope.

Robert W. Wilmarth, Ronald J. Blanchard

### 1. A wide-band travelling-wave maser

The bandwidth of a Travelling Wave Maser (T.W.M.) is limited primarily by the width of the resonance line employed at the signal frequency. If neither the orientation of the paramagnetic crystal with respect to the external magnetic field nor the magnitude of the field vary along the length of the T.W.M. then it is found [l] that the bandwidth to half power points is 1<math display='block'> <mrow> <mi>B</mi><mo>=</mo><mfrac> <mn>1</mn> <mrow> <mi>&#x03C0;</mi><msub> <mi>T</mi> <mn>2</mn> </msub> </mrow> </mfrac> <msqrt> <mrow> <mfrac> <mn>3</mn> <mrow> <msub> <mi>G</mi> <mi>o</mi> </msub> <mo>&#x22C5;</mo><mn>3</mn> </mrow> </mfrac> </mrow> </msqrt> </mrow> [/itex]$$B = \frac{1}{{\pi {T_2}}}\sqrt {\frac{3}{{{G_o} \cdot 3}}}$$

J. C. Walling, D. H. J. Body

### 2. Travelling-wave maser with tuning range from 4 to 6 MM.

During recent years the operation of maser amplifiers has been extended far into the millimeter-wave range [1], [2], [3], [4]. This has been achieved through the use of new maser materials, very high pump frequencies and sophisticated pumping methods. These advances, obtained almost exclusively with experimental cavity-type masers, have paved the way for the development of more advanced maser amplifiers utilizing trav el in g-wave interaction. As is well known, traveling-wave masers are eminently suited to the incorporation of unilateral gain characteristics. The vastly improved device performance, such as larger gain-bandwidth products and unconditional amplifier stability, is well wortn the additional complexity of design.

G. E. Weibel

### 3. The effects of temperature on the output of a pulsed ruby laser

The output pulse of a laser depends upon certain properties and, it is the intention here to discuss the change in these properties as a function of temperature. The particular parameters of interest are the time taken for population inversion i.e. the time delay between the application of the pulse and the start of laser action, and the pulse length.

A. K. Kamal, S. D. Sims

### 4. Messungen am Reflexionmaser und Bestimmung der klompexen Suszeptibilität von Chromkaliumcyanid bei der Temperatur des flüssigen Heliums

Wenn auch in den letzten Jahren eine grosse Zahl von Mikrowel1en-Masern in Betrieb genommen und untersucht worden ist, so liegen doch bisher nur wenige genaue Messungen der komplexen Suszeptibilität von Maser-Materialien im Betriebszustand, d.h. bei negativen Spin-Temperaturen, vor. An einem Maser mit Chrom-Kalium-Cyanid bei der Signalfrequenz 2,8 GHz/s und der Pumpfrequenz 9,2 GHz/s wurden im Institut für Hochfrequenztechnik und Hochfrequenzphysik der Technischen Hochschule Karlsruhe solche Messungen von Reeh [5] aus geführt.

Horst Rothe

### 5. Generation of submillimeter radiation by mixing of optical wavelengths

One approach to the problem of generating signals in the submillimeter range is to start from the large outputs available both at centimeter wavelengths or below one micron wavelength, and synthesize them by using non-linear media. The first alternative involves harmonic generation of microwave fundamental frequencies, and experience has shown that it is very difficult to obtain acceptable conversion efficiency above doubling or tripling. The second approach has become possible since the advent of high power masers in the optical and near infrared regions of the spectrum. These signal generators are capable of pulsed outputs of many kilowatts, and their frequency stabil ity is quite sufficient to provide monochromatic beat notes at wavelengths thousands of times larger.

M. Di Domenico, J. R. Fontana, R. H. Pantell, O. Svelto, J. Weaver

### 6. Broadband detectors for microwave modulated light

In order to take advantage of the extremely large information rates that are potentially available with optical masers, one must be atrle to modulate light at high modulation frequencies and over very large modulation bandwidths. Conventional photoelectric and photoconductor devices have found wide use aslight demodulators; however their modulation frequencies are generally limited to a few hundred megacycles. In this paper we describe devices which are capable of demodulating light which has been modulated at microwave frequency rates and over microwave modulation bandwidths. Such a device, which we call a microwave phototube [1] -[5], is shown schematically in Fig. 1. It consists of a conventional microwave tube in which the normal thermionic cathode has been replaced by a photocathode. In this case, the microwave-modulated light strikes the cathode producing a microwave-modulated or ‘pre-bunched’ electron beam. This beam then interacts with the microwave tube circuit and the modulation is obtained at the output of the tube. Slow-wave circuits such as the helix used in conventional TWT’s are ideally suited to the larger bandwidths desirable for microwave phototubes. In fact, a number of experiments have been performed using such a traveling-wave microwave phototube [3], [5].

B. J. McMurtry, J. B. Gaenzle, A. E. Siegman

### 6. An efficient optical maser modulation scheme

One of the great attractions of optical masers is that they can provide us with a communication carrier at light frequencies. In the present day shortage of communication channels this is a great asset. When we consider the output of a ruby optical maser, we find that it corresponds to a carrier whose frequency is given by v = = c/λ = 4. 3 x 1014 cycles per second. With a 0,1% modulation bandwidth, we could then obtain a 400 Gc/s wide modulation channel. For practical reasons we could only consider, at present, a modulation channel of some 4 Gc/s, i.e., in the microwave range of frequencies, but even that is exceptionally large by ordinary communication standards. An excellent review of the use of optical masers in the field of communications is given in reference [1].

P. A. Lindsay, M. Ciftan, S. Koozekanani

### 8. Possibilité d’action laser dans 1’infra-rouge lointain

Les lasers utilisent une résonnance atomique en présence d’une inversion de population des niveaux atomiques.

P. Laurès

### 9. Transient processes in beam masers

The steady state oscillation in the beam maser was investigated by many authors [1], [2], [6]. Now it is necessary to have information about a transient process in the masers, e.g. to investigate the approach of the amplitude and phase of the oscillation in the maser to the steady state starting from the moment when the high stress is applied to the focussing system. In the papers [3], [4], [5] the equations describing diverse processes in the beam maser were obtained. These equations are valid for the time t >> τ, (τ-is the mean time of the particle interaction with el ectromagnetic field in the cavity). However, this is not the case, we consider the situation when in the first moment there are no active molecules in the cavity. In this work the processes of the approach of the amplitude and phase to the steady state starting from the moment of molecules entering in the cavity are investigated.

A. S. Grassjuk, A. N. Oraevskij

### 1. Progress in low-noise travelling-wave tube development

Low-noise traveling-wave tubes have been in existence about fifteen years, but only during half this time have they been in production. In fact, it is only during the last few years that they have been turned out in sufficient quantity to merit the term ‘production’. Although in principle and in general appearance present-day low-noise tubes bear a strong resemblance to the original tubes, recent improvements of their electrical and mechanical characteristics and reproducibility of those characteristics are very impressive.

B. P. Israelsen, R. W. Peter

### 2. Investigations on very-low-noise travelling-wave tubes

It is now almost five years ago since Siegman and co-workers [1] drew attention to the importance of the multivelocity region of an electron beam for the reduction of the beam noisiness.

B. G. Bosch, K. B. Niclas, H. Thienel

### 3. The redaction of noise temperature in electron beams

This paper concerns the possibilities of cathode noise source reduction in longitudinal interaction (E type) microwave devices of the slow wave variety.

N. W. M. SMith

### 4. Non-linear theory of the propagation of signal and noise along an electron beam

Linear theories play an important role in the analysis of electron beam devices. The associated wave picture not only facilitates the understanding of the basic physical phenomena but can also lead to useful design formulae. At low levels of operation the linear approach has been very successful anditwas only for the determination of saturation power and harmonic content that non-linear theories were needed.

L. Solymar

### 5. Noise in Backward-wave amplifiers, a large QC theory and a proposed experiment for the measurement of noise parameters using a moving gun technique

It is well known that the best obtainable noise figure for the travelling wave tube (TWT) and the backward wave amplifier (BWA) is set by the inherent noisiness of the electron beam caused by shot and velocity fluctuations at the cathode. These fluctuations set up a standing wave of noise current on the beam and introduce noise into the amplifier output by interaction with the slow wave structure (helix).

A. J. Fox, D. T. A. Blair

### 6. Analysis of the noise spectra of a drifting multi-velocity beam

The minimum noise factor of beam-type microwave amplifiers is determined by the manner in which noise waves propagate in the low velocity region adjacent to the cathode. This multivelocity region has been analysed hitherto by means of machine integrations of the Boltzmann transport equation. In contrast, the present paper presents an analytical solution which provides closed-form expressions for the noise pow3 (r spectra (S, π, Φ) along the beam. In particular, a final steady state, that exists far downstream and in which the noise waves are washed out, is described.

S. Bloom, B. Vural

### 7. Artificial high temperature sources for noise modeling studies

Al though much progress has been made in the understanding of the high-frequency noise behaviour of electron streams [1], many problems remain, especially in the correlation of theory with experiment in the low-velocity region. Perhaps the major difficulty results from the fact that most experiments must be made in the high-velocity region through the determination of induced noise current, noise figure, or correlation coefficients in the accelerated beam. Deductions may then be made concerning conditions in the low-velocity region, but often the deductions are not unique.

J. R. Whinnery, M. A. Pollack

### 8. A method of noise reduction for linear beam microwave devices of medium power

The minimum noise figure of a 1ongitudinal-beam amplifier utilizing velocity modulation is limited by the uncorrelated noise power in the slow space-charge waves [1] (p.148) because these are the active modes of a beam; that is, they have the properties of negative resistances. Beam noisiness constitutes the main contribution to the noise output of a similar

W. R. Curtice

### 9. Photon noise

Two types of noise are discussed that may become important when light frequencies are used for communication purposes. At such high frequencies a quantum of energy is not negligible compared to the total transmitted energies (low number of quanta!). The fluctuations caused by the nonzero size of a quantum of energy will predominate over thermal noise, and the usual amplifier noise encountered at microwave (and lower) frequencies. The two types of processes producing quantum noise that we intend to discuss are shown in Pig. 1. They are:1.The radiative attenuation noise introduced when a signal, phase-and amplitude-control1ed at the high-power transmitter end, is highly attenuated through the inverse square law radiative attenuation. Such a process would take place in the use of optical frequencies for energy transmission over large distances.2.The noise introduced in linear amplification.Theobjective of this paper is to show how these forms of noise can be analyzed using simple statistics and classical electromagnetic theory with the aid of only a few quantum-theoretical results that have a simple physical meaning.

H. A. Haus, J. A. Mullen

### 10. On the problem of reducing the noise figure of medium-power travelling-wave amplifiers

By the expression ‘medium-power travel ling-wave amplifier’ we shall mean a broadband electron tube capable of amplifying an input signal by many dB, say 30 dB or more, to a CW output power level between one watt and twenty watts.

W. E. Waters, J. R. Largent

### 11. Noise in the saturation region of a travelling-wave amplifier

A 6000 Me relay system which has been developed in our laboratory, consists of all-travelling-wave-tube-type through-repeaters. This system has been confirmed to have the capabilities of transmitting more than 1800 telephone channels, the qual ity of which meets the CCIR specifications for transmission quality.

M. Kamihara, Y. Uji, F. Kawashima

### 12. Noise in a hollow beam injection gun for “O” type tubes

Some first experiments on the noise of magnetron injection guns will be reported. The injection gun may be considered as a smooth anode magnetron, one cathode hat being removed so that a part of the rotating beam escapes from the crossed field region to follow the magnetic field lines.

J. Arnaud, G. Wendt, J. Lind

### 13. Crossed-field noise in the low-velocity region

The unsolved problem of high crossed-field noise has long been of interest to investigators. Experiments have shown that noise currents very much in excess of full shot noise [1] and temperatures well above cathode temperature [2] can be found in crossed-field electron streams. There is evidence that the noise growth appears in the gun region of crossed-field devices, and is greater for space-charge-limited operat ion than for temperature-limited operation [1], the reverse of the situation found in ‘0’ -type beams.

M. A. Pollack

### 14. Noise figure calculation and measurement for low-power crossed-field amplifiers

Some measurements that have been made in our laboratory indicate that it is possible to make crossed-field amplifiers with moderately low noise figures without any special noise-reduction transducers [1]. This can be compared with the situation in an O-type tube where again no effort has been made to make an especially low-noise tube. In both cases the noise figures which would be obtained are of the order of 25 dB. The measurements we have made lead us to believe that the crossed-field amplifier is not necessarily noisy and also have led us into considering possibilities of making ultra-low-noise amplifiers. This paper contains more of our measurements and also some theoretical work in which we have investigated the effect of changing the drift space between the gun and the interaction region.

T. Van Duzer

### 15. A proposed large signal noise mechanism in crossed-field devices based on quasi-analogous hydrodynamic experiments

Observations of the manner in which a modulated vertically falling jet of water breaks up (Fig. 1 and 2) have shown that a backward directed force appears at the point where the drops leave the continuous portion of the jet. This force excites towards the orifice propagating backward waves, which under certain conditions may reach the orifice and cause a sudden transfer of the breakup point to the orifice. This is a well known phenomenon generally observed when a watertap is carefully opened or closed.

### 1. New numerical methods in electron dynamics

The calculation of the motion of charged particles in electrostatic and magnetostatic fields is a problem which has existed in many branches of physics for a long time. Its importance is reflected by the great number of methods which have been developed to solve it. These methods can be compared and assessed from various points of view, such as accuracy, speed, equipment or versatility.

J. R. Hecntel, D. F. Brauch, A. Mizuhara

### 2. Analysis of non-laminar space-charge flow

The growing trend toward the generation of millimeter wavelengths and of megawatts of c. w. power at centimeter wavelengths has made the problem of forming and controlling precise dense electron beams one of the most important encountered by microwave tube engineers. The central problem, that of predicting analytically the curvilinear behavior of electrons when space-charge effects are gross, is subject to attack from two differing viewpoints:1.Synthesis. -Treating an initial value problem, one can seek space-charge flow solutions possessing properties suitable for the application in mind (e.g., laminarity and high convergence, in the case of electron gun design). Then, using such flow solutions, one determines the necessary shapes of electrodes surrounding the beam to sustain such space-charge flow. This approach, which will be recognized as the basis for Pierce [1] gun design, has been extensively explored, for cases involving curvilinear space-charge flows, by Kirstein [2], [4], Kirstein and Kino [5], Kino and Taylor[s], Dryden [7], [8], and others. The problem of determining electrode shapes has been explored by Kirstein[2], Lomax [9],[l0], Picquendar, et al. [11], and Harker [12], [13]. The most general treatment appears to be that of Dryden [8], who, collaborating with Harker, has programmed the three-dimensional, axially-symmetric, curvilinear flow problem for solution by means of high speed digital computers.

E. E. Erickson, A. D. Sutherland

### 3. Electron trajectory tracer associated with resistance network analogs

For the design of the electronic apparatus which makes use of electron beam, it is essential to know electron trajectories in its electron optical system. This problem includes two sub-j ects; the first is to know the electric and magnetic field distributions in a given elec-trode-and magnetic pole-system, and the second to determine electron paths with the knowledge of the fields. The electron trajectory tracer described in this paper has two resistance networks for solution of electric and magnetic fields, and analog computers for the determination of electron paths. Some tracers using a resistance network analog for solving electric field were already reported [1], [2]. Ours is, however, distinguished from them in two points: the first is that a resistance network analog for magnetic field is added to that for electric field and the second that, for integration of the equation of motion, analog computers are used. Accordingly, the first advantage of our tracer consists in the capability of dealing with the problems involving magnetic field. It possesses, moreover, several other advantages due to the use of analog computers, such as the ease of handling and the direct visualization of electron motion.

### 4. Design criteria for high-density hollow-beam electron guns

Over the past few years there has been an ever increasing interest in microwave tubes of higher average power capability. At an average power level of roughly 5 to 10 kW (at X-band), even a well -focused, solid electron beam becomes of marginal utility for use in a traveling-wave tube because of the problem of circuit heating due to electron interception. Above this level of power, therefore, we must consider either a multiplicity of solid beams of preferably a large hollow beam. Despite the increased interest in high power, and therefore in hollow beams, there appears to have been relatively little work done on the design of electron guns which are suitable for generating high-density, hollow electron beams, at least in comparison with the effort which has been expended in research and development of guns for solid beams.

E. G. Todd, N. B. Kramer, G. R. Brewer

### 5. Analyseur de densité de courant dans un faisceau électronique

Un grand nombre de tubes hyperfréquences appelés tubes ‘0’ utilisent des faisceaux cylindriques pleins. Depuis plusieurs années, on cherche a accroître la pervéance et 1 a convergence des canons tout en limitant le plus possible, les aberrations qui tendent à augmenter en même temps que ces performances. La principale est l’aberration sphérique qui provoque une inhomogénéité du faisceau, et sa non laminarite.

M. Arnaud

### 6. Limiting currents and neutralization in cylindrical electron beams

The present work concerns the behaviour of a cylindrical electron beam of very high perveance in an electrically ‘field-free’ drift tube with a strong longitudinal magnetic field. Space charge limited flow and the effect of neutralization by positive ions have been studied for electron energies up to 100 volts.

H. H. Atkinson

### 7. Crossed-field electron guns with tapered gaps

It has been shown previously [1] that a crossed-field electron gun consisting of plane-paral1 el cathode and plate gives a space-charge limited current which is independent of cathode length (along the direction in which the beam emerges) over a very wide range. The value of the current may be predicted by the assumption of laminar ( ‘Brillouin*) flow; the emission from the cathode is highly non-uniform. When such guns are used in crossed-field backward wave oscillators, their performance is critically dependent on cathode temperature, being best near temperature limitation, when the emission ismostnearly uniform. A simple extension of the laminar flow result which ensures uniform emission under space charge limited conditions, leads to a theoretical taper for the cathode.-plate space. When such guns are used in backward wave oscillators, their performance is improved, and is no longer critically dependent on cathode temperature once space charge limitation is established. The gun taper derived may be shown to be similar to that obtained by Kino [2] by somewhat different reasoning.

A. Reddish, G. Smol

### 8. The numerical analysis of curvilinear electrode systems with an emitting surface

In most procedures for analyzing specific electrode systems in which a beam comes from a cathode, the same basic methods are used. First in the given ele.ctrode system, without space-charee, or with an assumed space-charge distribution, Poisson’ s equation is solved. Then, trajectories are traced and, by use of the continuity of charge equation, a new set of space-charge source terms are evaluated. Poisson’ s equation is then solved again and the process continued. In the past the solution of Poisson’ s equation has usually been performed on an analogue device [1], [2], while the trajectory tracing has either been performed numerically or by an analogue or digital computer attached to the analogue device. Relaxation methods have long been used to solve Poisson’ s equation, and it is clearly more convenient if the whole cycle of computation can be performed automatically on a digital computer [6]. Unfortunately, such computations for practical problems require a computer with a large fast memory. The present programme was written for an IBM 709 computer with a fast memory of 32,000 words. A typical problem took about 20–25 minutes to solve on this computer.

P. T. Kirstein, J. S. Hornsby

### 9. New method for the design of high perveance guns

In this paper we describe new methods for the design of electron and ion guns. The designer of these guns has always been limited in the past in his choice of gun designs to meet particular specifications, and considerable effort has been made over the years to make gun design methods more versatile. It is our purpose in this paper to describe two new methods which should increase this versatility. Before discussing these methods in detail, it would be well to put them in proper perspective.

D. S. Colburn, K. J. Harker, G. S. Kino

### 10. Magnetron injection guns derived from theorectical space-charge flow solutions

During the past three years we have had occasion to design and build magnetron-injection guns for producing hollow beams. These guns have been designed both from a planar space-charge flow which has been described by Kino and Taylor [1] and more recently from one of the axially-symmetric flows described by Kirstein [2]. Though these flows may be a gross simplification of what might actually occur in a crossed-field gun of this type wehave found that they enbale us to predict perveance and cathode current-density distribution to a most useful degree of accuracy.

N. J. Taylor

### 11. Space charge flow in spherical coordinates with applications to magnetron injection guns

In a recent publication, Kirstein [1] called attention to the possibility of calculating space charge flow by separation of variables in spherical coordinates (r, θ, φ). To be of practical value, detailed information about the solutions must be obtained. It appears that closed form solutions for the equations of motion are not practical even if they are possible, since one needs the numerical data for the solutions. It is usually more convenient to have a computer solve the differential equations than to evaluate a closed form solution of the differential equations. All of the equations for computations will be written as first order differential equations with respect to time as the independent variable. This makes each of the necessary differential equations well behaved at the cathode and allows

V. W. Dryden

### 12. Design of a high-perveance magnetron injection gun and some applications

This paper will be concerned with a method of designing magnetron injection guns which are capable of launching, high-perveance hollow.beams. Test results obtained from such guns together with several applications of these guns will also be discussed.

B. Arfin

### 13. An experimental study of magnetron electron guns

Before describing the results it is wise to make clear one important difference between the cylindrical gun and the guns used in linear crossed field devices, a difference which is partially removed by coning the cathode. Over most of the cylindrical region the electric field is purely radial.BQis purely longitudinal so the magnetic force has no component in the z direction. In the linear magnetron gun there is a strong z directed magnetic force, while in the conical cathode magnetron the coning introduces a z directed component of the electric field. Thus, in both the latter cases there are first order forces pulling the electrons into the flow. For the cylinder, there is a region at the end of the cathode where the discontinuity gives rise toEzand apart from that forces due to longitudinal variations of space-charge density exist. The field at the discontinuity will cause a z-directed electron flow; this in turn destroys the space-charge limited flow results. It is our purpose to examine this flow and to compare it with theory, although in this paper we confine ourselvces to the experimental results.

A. H. W. Beck, H. L. Nattrass

### 14. Non-uniformities in a P. P.M. focusing circuit

The theory and design of a periodic permanent magnet (P.P.M.) focusing circuit are based on the assumption that both the period and peak magnetic field are constant. This ideal, however, is never attained in a practical circuit. Non-uniformi ti es in the period or magnetic field may be due to various tolerances or mechanical design of the circuit. On the whole, undesirable variations tend to increase the beam ripple which, in the case of the travel-ling-wave tube, may lead to loss of gain, increased frequency sensitivity and high intercepted current.

B. Minakovic

### 15. Axially-symmetric space-charge flow in a decelerating space

To the extent that an electron beam of finite cross-section in a decelerating space can be considered as a one-diraensional problem, the theory presented by Pay, Samuel and Shockley [l] and by others [5], [6], [7] provides an adequate description of the beam at currents less than that of limiting perveance. If the current exceeds that corresponding to limiting perveance, it has been shown that the device does not select one of the static modes, but chooses a time-varying solution to the problem [2], [3]. Below limiting perveance the static theory is correct. The results of this static theory may be summarized as follows. Electrons are injected into the space between two. parallel planes at a velocity corresponding to the potential of the first plane with a current density J. The spacing between planes is d and the second plane is at potential V2 The solution of Poisson’ s equation in one dimension yields the form of the potential V(z)between the values V1 and V2 at z = 0 and z = das a function of the injected current density J.

D. A. Dunn, R. P. Borghi, R. C. Morwood

### 16. On the effect of thermal velozities in two-dimensional and axially symmetric beams

The estimation of thermal velocities in cathode ray tubes and travelling wave tubes has long been of great importance. Recently, devices have been proposed, such as ion propulsion devices, which have acceleration-deceleration systems; in these the consideration of thermal velocities, and the consideration of space-charge effects are often dif ficul t to treat independently. Pierce [1] has given a general treatment of the effects of thermal velocities. Cutl.er and Hines [2] have considered a specific case, round beams with a constant current density at the cathode, in a linear manner. Danielson [3] extended this linear treatment by considering the effect on a typical particle of the nonlinear fields which might be present and then assumed that the mean effects on any other particle will be the same as that on this typical particle.

Peter T. Kirstein

### 17. The use of a staggered meander line in an electrostatically focused forward-wave amplifier

In the search for improved microwave communications systems, the electron beam devices which at present form the heart of such complexes are called upon to perform in more and more rigorous environmental conditions. There is a continuing demand for small er, lighter, more rugged packages. One aspect of this trend is the desire for a beam focussing means which does not inhibit the inherent ruggedness of the device. In this respect, electrostatic focussing offers some considerable advantages over the presently available magnetic systems in terms of mechanical and temperature stability.

P. J. Newl

### 18. Wanderfeldföbren mit einem Elektrostatisch in ein Zylinderfeld eingeschlossenen Strahl hoher Kompression

Wanderfeldröhren mit einem Elektro statisch in ein Zylinderfeld eingeschlossenen Strahl hoher Kompression

Herbert Schnitger

### 19. A mathematical model which describes the high-perveance instabilities of long drifting electron beams

It has been recognized for more than twenty years that space-charge effects set a definite limit on the stable electron beam current that can be injected into a given conducting enclosure at a particular energy, If this value of ‘limiting current’ or ‘critical perveance’ is exceeded, the beam becomes unstable. Haeff [1], Pierce [2], Smith and Hartman [3], and Fay et al [4], many years ago derived the expressions predicting these critical perveance magnitudes for the most likely enclosure and beam configurations. More recently, the actual dynamic behaviour in this range of operation beyond critical perveance has come under investigation by Birdsall and Bridges [5], Buneman [6], Lomax [7], Lauer and Twombly [8], and others.

J. C. Twombly, J. E. Lauer

### 20. Efficiency enhancement by phase focusing and collector depression

Nonlinear calculations [1], [2], [3] of the el ectron-wave interaction process in TWA’ s, klystrons and BWo’ S have permitted the calculation of interaction efficiencies along with information about the energy state of the spent beam. These calculations have been primarily concerned with the r. f. interaction process and have not considered the effects of collector depression on the overall efficiency of the particular device. In this paper the effect of collector depression on device efficiency is studied theoretically and calculations are presented for the TWA and the BWO under a variety of operating conditions.

Joseph E. Rowe

### 1. Wave types in vortical and in irrotational electron beams

The theory of wave propagation on electron beams focused by a finite magnetic field -though frequently treated in literature -is still unsatisfactory:1)On Brillouin beams waves with radial periodicity are thought to be physically nonexistent [l], [2] while experimental results show the existence of higher ranking waves of this type [3]. No attempt has been made to calculate the excitation of Brillouin beams by gridded gaps since this is impossible if waves with radial periodicity are excluded.2)The influence of the magnetic flux threading the cathode and thus the basic dynamical difference between vortical (cathode flux) and irrotational (no cathode flux) beams is not understood. It is unknown which modes carry the vortical part of the noise on an irrotational beam which is excited by initial thermal velocities at the cathode.3)Transverse waves propagating the center-of-gravity motion of the beam have not been shown to appear in the set of modes resulting from a general first order theory.

H. Pötzl

### 2. A thick beam analysis of transverse-wave propagation on electron beams

This paper presents some results from an analysis of transverse-wave propagation on electron beams of finite diameter and space-charge. The analysis shows that the simple filamentary beam model is inadequate in several respects. It does not give correctly the details of the electron motion within the beam, and does not predict all the transverse waves that can propagate on a beam of finite diameter and space-charge. In particular, it does not give higher order transverse waves, that is, waves with more than one variation around the circumference.

T. Wessel-Berg

### 3. Space charge waves in finite magnetic fields

The space-charge waves predicted by small-signal theory for the customary limiting conditions of ‘confined-flo w’ electron beams [1] and Brillouin electron beams [2], [3] are well known. Since practical linear beam microwave tubes do not operate in the limiting region of either of these beams, it is of interest to consider the space-charge waves present for intermediate values of the d.c. focussing magnetic field or the finite magnetic field region. It is the purpose of this paper to examine the nature of these space charge waves, and especially to see how these are related to the usual waves attributed to the two limiting conditions of beam flow. To facilitate this qualitative examination, the space-charge waves will only be considered in a ‘classical’ sense, i.e., a quasi-static solution will be found. In addition some preliminary results on the effect of d.c. scalloping of the electron beam are presented.

L. A. MacKenzie

### 4. Experimental investigation ot non-linear phenomena in electron beams at fundamental and harmonic frequencies

A knowledge of the behaviour of electron beams under large signal conditions is basic to any attempt to improve the efficiency of high power klystrons, and also tb the design of frequency multipliers. The latter are of considerable interest for millimeter wave generation. It is a remarkable fact that in spite of the tremendous scale of activity in the high power klystron field, the 1iterature reveals very few experimental investigations of large signal beam modulation which are’fully quantitative. An increase of say 10% in the efficiency of a high power klystron is of great technical importance. It is clear therefore that if an experimental investigation of large signal behaviour is to make a practical contribution to the design of high power tubes, the relevant quantities must be measured with a very considerable accuracy, — of the order of a few percent. Although the need for very accurate knowledge of the harmonic content of the beam is less acute, the comparison of the results with theory represents a useful and critical test of the latter.

G. King, L. Solymar, E. A. Ash

### 5. The current and velozity distributions in a velocity modulated, brillouin-focused electron beam

In recentyears, many experimental and theoretical studies have been made of the current distribution in velocity-modulated electron beams. The major drawback of the experimental investigations has been that no careful examination was made of the state of the direct-current beam before modulation. A knowledge of the state of the unperturbed beam is important, because most theories that describe the r.f. behavior of a beam are based on an ideal beam; i.e., one that is laminar, free from scalloping or other variations in the axial direction, and having a charge density that is constant in the radial and angular directions. Since the major purpose of this study was to compare theoretical predictions with the actual beam behavior, it was necessary to produce a beam that approximated the ideal beam as closely as possible. Moreover, it was desirable to produce a beam similar to those used in commercial linear-beam tubes, so that any results obtained would have a direct bearing on the design and operation of commercial tubes.

A. S. Gilmour, G. C. Dalman, L. F. Eastman

### 6. Propagation of space charge waves and electron bunching in rotating electron-flows focused by centrifugal-electrostatic method

An el ectrodynamic waveguide model (a metal delay system dielectric) interacting with the electron waveguide (electron current) can be used for studying various phenomena in modern microwave devices.

Z. S. Tshernov, G. A. Bernashevsky

### 1. Aspects of slow wave structure synthesis

This lecture will first outline a method of programming computers to calculate the dispersion curves and impedances of slow wave structures used in microwave work. I believe the time has come to analyze and tabulate slow wave structure characteristics once and for all. We have not yet begun this programme at the University of California but I have no doubt it can be carried out successfully. After outlining to you the steps in the computer analysis I shall quote a variational expression for frequency at a given propagation constant which I have found to be a tight upperbound to dispersion curves of certain helices. Prom this expression we can obtain a perturbation formula for a general helix which is the analog of Slater’s perturb- ation formula for a resonant cavity. Last of all, I shall describe a rather well-known method of shaping the dispersion curve of a narrowband cavity chain by resonant-slot or resonant-loop coupling.

R. M. Bevensee

### 2. Über eine wendelformige Verzögerungsleitung für Wanderfeldröhren hoher Leistung

Der Dispersionsverlauf und der Kopplungswiderstand einer einfachen Rundwende] ist auch bei Strahlgeschwindigkeiten zwischen 10 und 20 kV bekanntlich noch recht gut. Aus diesem Grunde wird man jede Verbesserungg der thermischen 3e- lastbarkeit der Wendel begriissen, welche ihre elektrischen Eigenschaften nicht wesentlich verschlechtert.

R. Liebscher, E. Mayerhofer

### 3. Design and fabrication of a two-mile disk-loaded linear electron accelerator

A two-mile electron linear accelerator designed to produce an electron beam of high intensity in the energy range of 10 to 40 Bev for purposes of physics research is now being constructed on a site near the Stanford University campus. Stanford is carrying out this work under a prime contract with the U.S. Atomic Energy commission. The estimated total construction cost of this accelerator is \$114 million. The construction schedule calls for completion by July 1st, 1966. A general view of the accelerat or and the experimental area is shown in Pig. 1.

A. L. El. dredge, G. A. Loew, R. B. Neal

### 4. New types of severed circuits to increase the gain and bandwidth of magnetron amplifiers

Previous progress on injected-beam, non reentrant crossed-field forward-wave amplifiers has resulted in tubes capable of large bandwidth, high power, good efficiency but capable of only moderate gain. Until recently, most of the work on this type of device has been done on tubes of circular format. The circular format amplifier is limited to moderate gain because of the many possible modes of r.f. feedback from output to input. Recent work on the linear form of the injected-beam crossed-field amplifier has greatly reuucea the feedback problem and, coupled with severed circuit techniques, has put the crossed-field amplifier in the same high gain class as the conventional O-type traveling-wave tube and the multiple-cavity klystron.

G. P. Kooyers, P. N. Hess, E. K. Shaw, G. E. Pokorny, A. E. Kuschnick

### 1. Development of Miniaturized travelling wave tubes

The increasing need for developing highly complex compact, and efficient microwave systems has created the need for microwave tubes that have greatly reduced size and weight, which also have high overall efficiency, and which operate at reasonable voltages. One finds, however, that the important parameters for making an ideal tube are not the same for different power levels and frequencies. As an example, in a recent survey of the problem at X-band it became evident that at output powers above 100 watts c. w., the important design parameters were those associated with heat flow from the interaction circuit to the outside, and those associated with electronic and circuit efficiency. However, at powers less than 10 watts, it became clear that the heater power became the chief problem. If one is attempting to design an optimum high power pulsed tube, other problems come to the fore, such as beam focussing with a gridded gun, electronic efficiency, and, again, the heater power.

D. C. Buck

### 2. The generation of submillimeter waves

The operation of the conventional tubes has generally been thought to be limited to wav elengths larger than a few millimeters. To solve the problem of producing coherent energy at one millimeter and in the near submillime ter region, great expectations have been put in radiating electron devices using Cherenkov effect or the emission of accelerated electrons. Nevertheless while we may expect some progress in this field, the reported measured efficiencies of these deuices remain vanishingly low.

Guy Convert, Yeou Ta, Paul C. Moutou

### 3. Problèmes métallurgiques dans la technologie des tubes hyperfrequences

Les problèmes métallurgiques dans la technologie des tubes hyperfréquences sont de deux ordres:fournir des matériaux qui conviennent le mieux aux applications électroniquesmettre en oeuvre correctement ces matériaux. Les résolutions de ces problèmes ont pour but premier de donner un rendement maximal de fabrication des tubes et pour but final d’assurer la ‘fiabilité’ ou sécurité de fonctionnement de ces tubes.

P. Dumon

### 4. Dissipation calorifique dans les tubes en impulsion

D’après la théorie classique, si l’on applique à une paroi d’épaisseur infinie une puissance unitaire calorifique constante, la température de la paroi croit selon la racine carrée du temps. L’ application de cette loi à des tubes fonctionnant en impulsions avec des charges thermiques importantes conduit à des résultats incompatibles avec un fonctionnement correct du tube. Une puissance de 4 MW/cm2 appliquée pendant 5 μs conduirait à une température de 3000° C. On est alors obligé pour obtenir des résul tats cohérents de tenir compte de la pénétration du faisceau électronique dans la paroi et de considérer que l’apport d’énergie n’a pas lieu seulement en surface mais qu-e le faisceau perd progressivement son énergie à mesure qu’il pénètre dans la paroi.

G. Boucher

### 5. Dielectric tuning of klystron cavities

The introduction of a high permittivity, low-loss, dielectric material into a klystron cavity provides a means of obtaining large tuning ranges with low power loss. Furthermore, no contact is required between the dielectric tuner and the cavity wall. This eliminates spring-finger contact problems associated with inductive-slug tuners. Dielectric tuners affo-rd a means of obtaining tuning ranges comparable to gap tuning without the attendant environmental difficulties.

Walter R. Day

### 6. Acoustic detection of electron impact in electron tubes

It has been found experimentally that when a pulsed electron beam strikes the surface of a solid body in a vacuum it produces elastic waves in the body. This process has been identified experimentally as a thermal effect of generally higher efficiency than would result from direct momentum transfer. This thermal effect permits detection of electron impact in pulsed evacuated devices such as microwave tubes by the use of simple elastic wave sensors outside the tubes. In pulsed electron tubes it is thus possible to detect and locate electron interception, the distribution of electron impact in a collector, and a number of other characteristics relating to electron flow.

R. M. White

### 7. Mechanisms in high power windows

This paper describes further work on the study of the electron bombardment mechanisms in cone shaped windows.

M J. Smith

### 8. A new design of a high-power ceramic window

This paper describes an output window designed for a high power c.w. valve in the 3 cm band. It will pass over 5 kw uncoo led, has a bandwidth of 12%, and in addition has been operated successfully at 1.3 mw peak, 1 kw mean.

P. H. Cross

### 9. Scanning electron microscope studies of thermionic emission from dispenser cathodes

Several different types of cathode are known as dispenser cathodes. They are of interest to the microwave valve designer because they offer various advantages over the oxide cathode, chiefly that of-higher current density. The processes that activate the surfaces of these cathodes and the mechanism of electron emission are described in this paper.

H. Ahmed, A. H. W. Beck

### 10. The series resistance and emission from several types of dispenser cathodes

The impedance associated with oxide cathodes under active conditions is well known. Values as high as 100 Ω/cm2are reported. The impedance usually consists of the direct resistance of the oxide layer and a contribution from the interface and its capacity. The impedance is known to change with time, particularly when the valve is operated in the cut-off state. In this paper the resistance of dispenser cathodes is measured.

H. Ahmed, A. H. W. Beck

### 11. Cathodes thermoélectriques pour tubes hyperfréquences

On sait que les performances des tubes hyperfréquences sont etroitement liées a la densite fie courant que fournit la cathode [1]. La densité du courant de saturation d’une cathode thermoélectronique est une fonction exponentielle du rapport entre le travail de sortie et la température (loi de Richardson Dushman). Pour augmenter cette densité de courant, on peuth priori augmenter la temperature ou diminuer le travail de sortie, Or, pour un matériau donne, la température de regime ne peut pas être augmentée indéfiniment [2], car la vitesse d’évaporation du matériau de cathode croit aussi d’une manière exponentielle, ce qui diminue la durée de la cathode et risque de produire des courts-circuits entre les électrodes du tube. D’où 1’intérêt de choisir des matériaux réalisant un compromis entre l’émission thermoélectronique et la vitesse d’évaporation. On connait surtout deux familles de cathodes techniques réalisant un tel compromis: les cathodes à oxydes alcalino-terreux et les cathodes à réservoir de baryum. Comme l’on sait, le travail de sortie de ces cathodes varie avec les conditions de préparation, les conditions de fonctionnement (régime continu ou puisé) et les conditions d’ambiance (gaz rési-duels) [3], [4]. On se propose ici d’examiner le comportement de certaines cathodes de ces deux familles, dans des conditions de fonctionnement voisines de celles des tubes hyperfréquences, dans le but d’obtenir des densites de courant aussi élevées que possibles.

J. P. Freytag

### 12. Cathode à grande densité de courant sous forme d’un capillaire chaud à ionisation de surface

L’augmentation de la densité de courant des cathodes ayant ete enoncee comme un des leitmotivs pour améliorer les performances des tubes hyperfréquences [1], on a réalisé dans ce laboratoire des cathodes thermoélectroniques fournissant 10 A.cm-2 en regime continu avec une durée de vie supérieure à 1000 h, et plus de 100 A.cm-2 en régime pu 1sé. [2]. Or, pour obtenir des densités de courant encore plus grandes plusieurs possibilités sont suscept-tiblesd*etre intéressantes pour les tubes hyperfréquences, en particulier la cathode creuse qui a donné beaucoup d’ espoir. Mais, il s1est avéré que la charge d’espace électronique a l’intérieur de la cavité présente un facteur limitatif physique ne permettant guere des densités de courant supérieures a 10 A.cm-2.

H. Huber, R. Le Bihan, et J. Bensimon

### 13. Novel approaches to low-noise beam generation

Thermionic cathodes are presently used in all low-noise microwave tubes. These cathodes will serve as a standard of comparison in describing the noise performance of three new types of cathodes discussed in this paper. We will consider here the noise temperature associated with space-charge wave interaction involving the longitudinal motion of the electrons. This noise temperature is meaningful in terms of. the conventional traveling-wave tu.be and the klystron, but not in terms of the electron beam parametric amplifier which uses cyclotron waves involving the transverse motion of the beam electrons.

### 14. l’Usinage par électroérosion appliqué à la réalisation des tubes hyperfréquences

Les caractéristiques de plus en plus poussées exigées des tubes hyperfréquences actuellement en cours de développement ont amené les ingénieurs du laboratoire à concevoir des circuits de forme de plus en plus complexe dont les tolérances d’usinage sont depuis quelques années déjà aussi sévères que celles que l’on peut rencontrer en mécanique de précision.

H. Weill

### 15. Sur quelques travaux concernant les sources froides d’électrons

Les cathodes thermoélectroniques nécessitant un moyen de chauffage, et l’évaporation thermique de la matiere emissive étant une limite a leur utilisation, le leitmotiv des recherches de ces dernieres années a été l’étude de sources froides d’electrons. Parmi les phenomenes exploitables on trouve d’une part l’émission de champ et d’autre part l’émission dite autoentretenue. Les tubes électroniques équipés avec de telles cathode? pourraient constituer une nouvelle catégorie de dispositifs électroniques susceptibles de compléter les transistors dans le domaine de la puissance et dans le domaine ou l’on doit utiliser une intér-action é1ectrons-champ dans le vide.

A. M. Shroff

### 16. Basic and applied studies of field emission at microwave frequencies

The unique properties of field emission, as predicted by the Fowler-Nordheim theory [1], [2], have stimulated interest in the development of practical field emission cathodes. Recent work has yielded a more complete verification of the theory: pulsed emission densities above 108amp/cm2 [3], [4] agd d.c. emission densities above 107 amp/cm2 [5] have been, achieved and, with allowance made for space charge effects, found to be in accord with theory; also, recent careful measurements have reduced the observed energy spread of the field emitted electrons and brought it in excellent agreement with theory [6], indicating a beam noise temperature comparable to that of thermionic beams in the absence of beam area compression.

F. M. Charbonnier, J. P. Barbour, L. F. Garrett, W. P. Dyke
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