Collimated gamma photon emission driven by PW laser pulse in a plasma density channel

We use three-dimensional particle-in-cell simulations to demonstrate that a plasma density channel can stably guide the petawatt laser pulse in near critical plasmas. In this regime, a directed, collimated, and micro-sized gamma photon beam is emitted by the direct-laser accelerated electrons along the channel axis. While in the case without the plasma density channel, the laser tilting behavior leads to the generation of randomly deflected gamma photon beams with a large divergence angle and transverse source size. In addition, in the plasma density channels, the divergence angle of the gamma photon beams can be much reduced by using a smaller value of n(0)/a(0)n(c). The energy conversion efficiency can also be improved by increasing the laser power or the plasma density. This regime provides an efficient and compact approach for the production of high quality gamma photon beams. Published by AIP Publishing.