X-ray Emission in Laser-plasma Interactions with Orbital Angular Momentum

X-ray emission during laser-plasma interactions (LPI) is determined by the motion of high energy electrons. In this work, we use the x-ray emission spectrum to study the behavior of electrons under the influence of a laser pulse possessing orbital angular momentum (OAM). We have extended the fully relativistic, particle-in-cell code EPOCH to calculate the high-frequency radiation emitted during LPI. We use this module to simulate the x-ray emission when an ultrahigh intensity, short pulse laser (I₀ > 10²⁰ W/cm², τ ≈ 30 fs) with OAM is incident on a near-critical density (n_e ≈ 10²¹ cm^-3) plasma. We compare the results to similar simulations using Gaussian (l = 0) laser pulses keeping the intensity or energy constant. We also discuss the design for an experiment to measure the x-ray emission from thin targets using an l = 1 OAM beam in order to better understand the effect of OAM on electron motion during LPI.