Ionization injection effects in x-ray spectra generated by betatron oscillations in a laser wakefield accelerator

K T Behm,J M Cole,K Krushelnick,J Nees,J C Wood,A G R Thomas,S P D Mangles,V Yanovsky,A Maksimchuk,T Z Zhao

doi:10.1088/0741-3335/58/5/055012

Abstract

Single photon counting techniques were used with an x-ray CCD camera to measure features of synchrotron-like x-ray spectra generated by betatron oscillations of electrons in a laser wakefield accelerator (LWFA) with different injection techniques. Measurements were made using the Hercules laser system at the University of Michigan. With a single stage gas cell, we demonstrate that pure helium gas in our wakefield accelerator will produce spectra with higher critical energies than when helium mixed with nitrogen is used. This result was not evident when a two stage gas cell was used.

Highlights

Advances in laser technology have led to the use of high powered lasers to accelerate electrons to relativistic energies
The x-rays produced from a laser wakefield accelerator are the result of betatron oscillations carried out by electrons within the ion bubble that forms behind the laser pulse
The two different types of injection mechanisms that are present in these experiments are ionization injection and self injection

Summary

Introduction

Advances in laser technology have led to the use of high powered lasers to accelerate electrons to relativistic energies. These tunable ‘table-top’ accelerators produce quasimonoenergetic beams of electrons [1,2,3] but are excellent sources of synchrotron radiation [4,5,6,7,8,9,10,11,12]. The x-rays produced from a laser wakefield accelerator are the result of betatron oscillations carried out by electrons within the ion bubble that forms behind the laser pulse.

Methods

Discussion

Conclusion