Distributional Effects in Pair Plasmas in the Pair Reflection Regime*

The slowing down of pair particles has been shown to greatly magnify the frequency shift which occurs in an electromagnetic wave driving a QED cascade [1].

This frequency shift is a useful tool for observing collective pair plasma effects in laboratory plasma. 

It is thus significant that the stopping and reflection of pair particles can further increase the frequency shift. 

Previous work bounded the minimum laser intensity and laser pulse duration that would be sufficient for the radiation reaction to slow down particles to energies at which the frequency shift could be large [2].

This arose primarily from considerations of the mean behavior of pair particles, but it is known that significant changes in the distribution of particles can occur due to the radiation reaction [3].

We will discuss the consequences of these distributional changes and their interplay with the Lorentz force in the pair reflection regime.

[1] Qu, Kenan, Sebastian Meuren, and Nathaniel J. Fisch. "Collective plasma effects of electron–positron pairs in beam-driven QED cascades." Physics of Plasmas 29.4 (2022): 042117.

[2] Griffith, Alec, Kenan Qu, and Nathaniel J. Fisch. "Particle deceleration for collective QED signatures." Physics of Plasmas 29.7 (2022).

[3] Neitz, Norman, and Antonino Di Piazza. "Stochasticity effects in quantum radiation reaction." Physical Review Letters 111.5 (2013): 054802.