Optimizing the interaction geometry of inverse Compton scattering x-ray sources

TL;DR

This paper develops a theoretical framework to optimize the geometry of inverse Compton scattering x-ray sources, focusing on maximizing brilliance for different interaction angles and geometries.

Contribution

It introduces an analytic method to optimize x-ray brilliance by adjusting interaction geometries in inverse Compton scattering setups.

Findings

Head-on scattering with a focused laser maximizes brilliance.

Grazing angle geometry with elliptical focus benefits soft x-ray generation.

Optimization strategies depend on the specific x-ray application.

Abstract

Inverse Compton scattering (ICS) is a promising method for generating coherent and tunable x-rays in a compact setup. In this paper, we present a theoretical framework describing the output of an ICS x-ray source for arbitrary interaction angles between pulsed electron and laser beams. This allows for analytic optimization of the x-ray beam properties by varying the parameters defining the geometry. In general, different x-ray applications require optimization of different x-ray beam properties, such as energy spread for x-ray spectroscopy and angular spread for x-ray scattering measurements. In this paper, we restrict ourselves to optimization of the x-ray brilliance, which is a comprehensive figure of merit for x-ray beam quality. We investigate two specific ICS interaction geometries in particular: head-on scattering of a laser beam off an electron beam; and scattering of a laser beam off an electron beam in a co-propagating geometry, interacting under a grazing angle. For head-on scattering we show that a tightly focused, cylindrically symmetric laser pulse, which balances laser intensity and interaction time, optimizes the x-ray brilliance. For a co-propagating, grazing angle geometry, an elliptical focus of the laser pulse is required to mitigate the effect of a reduced interaction time. We find that the latter geometry is especially useful for soft x-ray generation.