Improvements to laser wakefield accelerated electron beam stability, divergence, and energy spread using three-dimensional printed two-stage gas cell targets

Abstract

High intensity, short pulse lasers can be used to accelerate electrons to ultra-relativistic energies via laser wakefield acceleration (LWFA) [T. Tajima and J. M. Dawson, Phys. Rev. Lett. 43, 267 (1979)]. Recently, it was shown that separating the injection and acceleration processes into two distinct stages could prove beneficial in obtaining stable, high energy electron beams [Gonsalves et al., Nat. Phys. 7, 862 (2011); Liu et al., Phys. Rev. Lett. 107, 035001 (2011); Pollock et al., Phys. Rev. Lett. 107, 045001 (2011)]. Here, we use a stereolithography based 3D printer to produce two-stage gas targets for LWFA experiments on the HERCULES laser system at the University of Michigan. We demonstrate substantial improvements to the divergence, pointing stability, and energy spread of a laser wakefield accelerated electron beam compared with a single-stage gas cell or gas jet target.

Experimental Signatures of the Quantum Nature of Radiation Reaction in the Field of an Ultraintense Laser

“…Measurements of the pointing fluctuation of the laser-driven electron beam indicate, as an average over 100 consecutive shots, an approximately Gaussian distribution (confidence of 95% from the Kolmogorov-Smirnov test) centered on the laser propagation axis with a standard deviation of ð3.2 AE 0.8Þ mrad [30]. The use of a gas-cell target, instead of a gas jet reported elsewhere [28] for similar experimental conditions, results in better shot-to-shot stability in the electron spectrum [31,32], with the maximum energy of the electrons closely related to the energy of the drive laser, as discussed in the next section. Moreover, it allowed much higher electron energies to be reached and, therefore, a much higher fraction of the Schwinger field in the electron rest frame.…”

Radiation reaction studies in an all-optical set-up: experimental limitations

“…For reference, different studies on shot-to-shot pointing stability have been reported in the literature (see, for instance, Ref. [38]). It is also possible that the electron beam might present a solid offset from the driving laser (non-zero mean in the Gaussian distribution discussed above).…”

“…However, a trade-off has to be found since it is desirable to prevent the scattering laser from damaging the gaseous target rig, especially if gas-cells are used [38,39]. For typical experiments, a minimum distance of the order of a few mm between the gaseous target and the high-intensity laser focus is thus recommended, leading to electron beam diameter at the interaction point exceeding 10 microns.…”

Optically Controlled Laser-Plasma Electron Acceleration for Compact γ-Ray Sources

“…Regardless of the time delay, very quiet injection keeps the e-beam brightness above 4 Â 10 16 A/m 2 , favoring the use of these beams in Thomson sources [76]. In the case of a time-delayed stack, extracting the e-beam before dephasing (using, for instance, a gas cell target of variable length [81]), thus changing the e-beam energy in the interval 400À900 MeV, preserves its 10 17 A/m 2 brightness.…”