Coherent radiation from kinetic instabilities in radiation reaction dominated domain

Coherent radiation emission can be prompted by the presence of unstable distributions under the appropriate plasma conditions. Unstable ring momentum distributions have been proposed as seeds for the electron cyclotron maser instability [1] and the Ion-channel laser [2] mechanisms. Expanding on recent work [2], we show that radiation reaction cooling can reshape the momentum distribution of relativistic beams into a ring distribution. This is due to the differential radiation cooling the beam particles experience in the presence of intense fields, in particular in ion channels [3]. Our analytical model is compared with Particle-in-cell simulations, using OSIRIS [4,5], and we determine the properties of the subsequent radiation emission.

[1] Cairns, R. A., et. al. Phys. Rev. Lett. 101.21 215003 (2008)

[2] Davoine, X., et al. JPP 84.3 (2018).

[3] Bilbao, P. J., Silva, L. O. to be submitted to PRL

[4] Fonseca R. A., et. al. Lect. Notes. Comput. Sc. 2331 342–51 (2002)

[5] Vranic M., et. al. Comput. Phys. Commun. 204 141-151 (2016)