Effect of nitrogen gas concentration on the laser wakefield accelerated electron beams
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Date
2021
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UMT, Lahore
Abstract
The concept behind the laser-plasma accelerators was first presented in 1979 by Tajima and Dawson. Such accelerators have a great potential to replace the conventional accelerators. They are low-cost, having compact setup and higher acceleration gradient. The acceleration rate is limited in the conventional accelerators by the maximum power of radio-frequency source which eventually causes the electrical breakdown at the metal boundary walls of the accelerators. This can also be overcome by the Laser wakefield accelerators LWFA. When an ultrashort, high intensity, high power laser pulse interacts with the plasma, there arises wake potential until it steepens and breaks. Those electrons which get caught and trapped cause deformation of the wake and stops the further injection of the electrons into the wake. The electrons which surf the wake become accelerated. The quality of the electrons beam accelerated by laser wakefield acceleration is strongly depends on the fact that when and where the injection of the electrons happens in the wake. Several injection techniques have been developed and experimentally demonstrated to control the injection of electrons in the wake and to improve the electron beam quality. One recent method is self-truncated ionization injection which was the most successful to creating low energy spread electron beams has shown encouraging outcomes. The dependence of electron beam quality on the different doping amount of trace gas i.e. different extents of the N2 doping in He gas has been studied in this dissertation. Two dimensional particle-in-cell simulations were performed to get the microscopic view of the distinct phenomena resulting in different beam qualities for different doping of N2. PIC simulations also provided the time resolve evolution of the accelerating structures for different N2 doping. The effect of trace gas doping extent on the self-modulation of the laser pulse is also shown.