Probing the fields of an LWFA in blowout regime using a relativistic electron beam

The large stable bubbles created by a sub-ps, long-wave infrared laser in low density ~10¹⁶ cm^-3) plasma provide ideal conditions for accelerating electrons with low emittance and energy spread [1]. Variation and evolution of the fields inside such a structure may be examined using a relativistic electron beam as a probe. Direct interaction of a particle beam with the fields, rather than the index of refraction in the case of a laser probe, enables the examination of low-density wakefield details with high sensitivity. Here, we explore the interaction of a relativistic beam with a plasma bubble using the analytical expressions for the fields in the blowout regime. This theoretical exploration will be focused on two limits: first, where the electron beam traverses the fields at a grazing incident angle and second, where the beam’s momentum is primarily transverse to the wakefield propagation. Application of the resulting expressions to the simulated fields of an LWFA in a blowout regime, particularly targeting the conditions that will be available at the Accelerator Test Facility (ATF) of Brookhaven National Laboratory (BNL) will be presented. 

[1] P. Kumar et al., Phys. Plasmas 28, 013102 (2020)