Self Injection Ionization - Poster

2017-07-17T10:03:01Z (GMT) by Alberto Marocchino
The characteristic of self-injected electron beams in Plasma Acceleration strongly and nonlinearly depend on both the driver (Laser, electron or positron beam) and the plasma wake properties. Several schemes have been proposed [1,2,3] in order to reduce the number of independent variables and therefore to improve the control on the self-injected beam quality. In the novel approach called beam driven Wakefield Ionization Injection [4], the ionization contribute of the driver is neglected via the choice of a dopant gas with high ionization potential, confined in a small region of a pre-ionized background plasma. It is assumed, however, that the driver current is high enough to induce the full blowout of electrons in its wake, i.e. the “bubble regime” [5,6]. The high ionization potential of the dopant gas ensures that it does not get ionized by the radial field of the driver, but only by the much more intense (~ 100 times) fields in the wake; besides, the ionized electrons are trapped in the accelerating and focusing phase of the plasma wave, yielding high brightness electron beams. In this work we studied the ionization-injected beam characteristics via a series of PIC sim- ulations, performed with the full open source 3D PIC code ALaDyn [8,9]. The effect of the dopant gas density distribution and volume have been studied systematically. We focused our interest on the ionization, the injection and then on the beginning of transport, for a total propagation of a few hundreds. We used a high brightness, high current electron beam driver (10 kA, 1GeV, ~ 20 fs duration). The results have been compared for different dopant gases (N, Ar, Ne), as the initial condition of the ionization- injected beam strongly depend on the ionization rate.