Commissioning and validation of the injector and electron beam transport systems for the IR-FEL at RRCAT

Abstract

The first observation of lasing in an infra-red free electron laser (IR-FEL) at the Raja Ramanna Centre for Advanced Technology has been reported recently with a measured power output, i.e. $${\sim }10^{5}$$ times higher than the expected spontaneous radiation power for the electron beam parameters used in the experiment. IR-FEL design simulations, however, estimate a power gain of $$10^{7}$$ which is three orders of magnitude higher than the experimentally achieved value. To understand this difference between the measured and the expected power output from the IR-FEL, the electron beam used in the experiments has been characterised and FEL simulations have been repeated after considering the measured electron beam parameters. A reasonably good agreement is obtained between the measured results and those predicted by FEL simulations. Experiments have also been performed to study the expected variation in electron beam properties over a macropulse, which should be minimum for an oscillator FEL like the IR-FEL. This paper reports the results from the experiments for characterisation of the electron beam in the IR-FEL set-up and the results from FEL simulations, considering these measured electron beam parameters.