Enhancement of electron-bunch quality in bubble domain utilizing plasma ramp profile with various density-hill widths in laser wakefield acceleration

The laser wakefield acceleration (LWFA) scheme is now a superb and potent instrument for industry, medicine, fusion, and other uses. With the aid of this technique, high-quality electron beams can be generated, which might eventually be employed to create small, portable X-ray sources. Using a linearly polarized Gaussian laser pulse, the present work focuses on examining electron acceleration in an under-dense plasma having a ramp profile with different density-hill widths. Two-dimensional Fourier–Bessel Particle-In-Cell simulation (2D-FBPIC) code shows that optimizing the laser parameters and plasma density profile maximizes the energy gain and minimizes the normalized rms emittance in the x, y directions inside the plasma bubble. For 10 and 90 \({\upmu\text{m}}\) density-hill widths, respectively, the optimal emittance value is reported to be \({\epsilon }_{x}\sim 3.10\) mm.mrad in the x-direction and \({\epsilon }_{y}\sim 2.63\) mm.mrad in the y-direction. At a density-hill width of 90 \({\upmu\text{m}}\), it is also observed that the charge trapped inside the bubble is 44.91 pC. With this density-hill width and a plasma channel length of 3.84 mm, our simulation findings show an energy gain of 0.38 GeV to the electron-bunch accelerated inside the bubble.