Improving performance of inverse Compton sources through laser chirping

¹ Department of Physics, Center for Accelerator Science, Old Dominion University - Norfolk, VA 23529, USA
² INFN- Milan - via Celoria 16, 20133 Milano, Italy
³ Thomas Jefferson National Accelerator Facility - Newport News, VA 23606, USA
⁴ Università degli Studi di Milano - via Celoria 16, 20133 Milano, Italy
⁵ Università di Roma La Sapienza - P.le A. Moro 5, 00185 Roma, Italy

Received: 4 February 2019
Accepted: 17 April 2019

Abstract

We present a new method for computation of radiation spectra in the non-linear regime of operation of inverse Compton sources characterized by high laser intensities. The resulting simulations agree well with the experiments. Increasing the laser intensity changes the longitudinal velocity of the electrons during their collision, leading to considerable non-linear broadening in the scattered radiation spectra. The effects of such ponderomotive broadening are so deleterious that most inverse Compton sources either remain at low laser intensities or pay a steep price to operate at a small fraction of the physically possible peak spectral output. This ponderomotive broadening can be reduced by a suitable frequency modulation (also referred to as “chirping”, which is not necessarily linear) of the incident laser pulse, thereby drastically increasing the peak spectral density. This frequency modulation, included in the new code as an optional functionality, is used in simulations to motivate the experimental implementation of this transformative technique.