Transformer Ratio Dependence on Bunch Length at Non-Linear Wakefield Excitation in Plasma by Electron Bunch With Gaussian Charge Distribution

Abstract

Using 2d3v code LCODE, the numerical simulation of nonlinear wakefield excitation in plasma by shaped relativistic electron bunch with charge distribution, which increases according to Gaussian charge distribution up to the maximum value, and then decreases sharply to zero, has been performed. Transformer ratio, as the ratio of the maximum accelerating field to the maximum decelerating field inside the bunch, and accelerating the wakefield have been investigated taking into account nonlinearity of the wakefield. The dependence of the transformer ratio and the maximum accelerating field on the length of the bunch was investigated with a constant charge of the bunch. It was taken into account that the length of the nonlinear wakefield increases with increasing length of the bunch. It is shown that the transformer ratio reaches its maximum value for a certain length of the bunch. The maximum value of the transformer ratio reaches six as due to the profiling of the bunch, and due to the non-linearity of the wakefield.The accelerating gradients in conventional linear accelerators are limited to 100 MV/m [1], partly due to breakdown. Plasma-based accelerators have the ability to sustain accelerating gradients which are several orders of magnitude greater than that obtained in conventional accelerators [1,2]. As plasma in experiment is inhomogeneous and nonstationary and properties of wakefield changes at increase of its amplitude it is difficult to excite wakefield resonantly by a long sequence of electron bunches (see [3,4]), to focus sequence (see [5][6][7][8][9][10]), to prepare sequence from long beam (see [11][12][13]) and to provide large transformer ratio (see [14][15][16][17][18][19][20]). Providing a large transformer ratio is also being studied in dielectric accelerators (see [21][22][23][24][25][26]). In [4] the mechanism has been found and in [27][28][29][30][31] investigated of resonant plasma wakefield excitation by a nonresonant sequence of short electron bunches. Due to the rapid development of laser technology and physics [1,2,[32][33][34][35][36][37][38][39] laser-plasma-based accelerators are of great interest now. Over the past decade, successful experiments on laser wakefield acceleration of charged particles in the plasma in blowout regime have confirmed the relevance of this acceleration [30][31][32][33]40]. Evidently, the large accelerating gradients in the plasma accelerators in blowout regime allow to reduce the size and to cut the cost of accelerators. Another important advantage of the plasma accelerators in blowout regime is that they can produce short electron bunches with high energy [32]. The formation of electron bunches with small energy spread was demonstrated at intense laser-plasma interactions [41]. Electron self-injection in blowout regime has been studied by numerical simulations (see [37]). Processes of a self-injection of electrons and their acceleration have been experimentally studied in a plasma accelerator [42].The problem at laser wakefield acceleration is that laser pulse...

Improvement of Properties of Self-Injected and Accelerated Electron Bunch by Laser Pulse in Plasma, Using Pulse Precursor

“…At the laser acceleration of self-injected electron bunch by plasma wakefield the accelerating gradient about 50 GV/m has been obtained in experiments [23]. In numerical simulation [28], performed according to idea of Prof. T. Tajima [25,29], on wakefield excitation by a X-ray laser pulse in a metallic-density electron plasma the accelerating gradient of several TV/m has been obtained. To solve the problem of laser pulse expansion, one can use a capillary discharge.…”

“…Plasma can provide much more accelerating electric field which is approximately in 10 3 times larger than possible in metal cavities of conventional accelerators [1]. As plasma in experiment is inhomogeneous and nonstationary and properties of wakefield changes at increase of its amplitude it is difficult to excite wakefield resonantly by a long sequence of electron bunches [2,3], to focus sequence [4][5][6][7][8], to prepare sequence from long beam [9][10][11] and to provide large transformer ratio [13][14][15][16][17][18]. In [4] the mechanism has been found and in [19][20][21][22] investigated of resonant plasma wakefield excitation by a nonresonant sequence of short electron bunches.…”

“…In [24,[26][27][28] it has shown that at certain conditions the laser wakefield acceleration is added by a beam-plasma wakefield acceleration.…”

Homogeneous Focusing Field for Short Relativistic Electron Bunches in Plasma

“…As plasma in experiment is inhomogeneous and nonstationary and properties of wakefield changes at increase of its amplitude it is difficult to excite wakefield resonantly by a long sequence of electron bunches (see [1,2]), to focus sequence (see [3][4][5][6][7][8]), to prepare sequence from long beam (see [9][10][11]) and to provide large transformer ratio (see [12][13][14][15][16][17][18]). Providing a large transformer ratio is also being studied in dielectric accelerators (see [19][20][21][22][23][24]).…”

Uniform Focusing of Sequence of Relativistic Positron Bunches in Plasma

“…Accelerating wakefield can be excited by single electron bunch [4,5]. As plasma is inhomogeneous and nonstationary it is difficult to excite wakefield resonantly by a long sequence of electron bunches [6,7], to focus sequence [8][9][10][11][12], to prepare sequence from long beam [13][14][15] and to provide large transformer ratio [16][17][18][19][20][21][22]. In [7] the mechanism has been found and in [23][24][25][26] investigated of resonant plasma wakefield excitation by a nonresonant sequence of short electron bunches.…”