Simulation of predicted performance and interpretation of radiation measurements on the Israeli tandem free-electron laser

The experimental results of radiated power and its spectral parameters as measured on the Israeli electrostatic accelerator tandem FEL (EA-FEL) are interpreted and numerically simulated. Two complementary simulation codes, FEL3D and MALT1D show good agreement with experimental results. The FEL3D code (a non-linear three-dimensional ‘amplifier’ code, based on a coupled-mode approach), was employed for calculation of the small-signal gain, extraction efficiency and saturation power. This code (FEL3D) allows one to simulate FEL operation of multiple transverse modes at a single frequency taking into account space-charge effects. Multi-frequency simulation of the mode competition process was carried out using the MALT1D code based on a space–time multi-longitudinal mode simulation of a FEL oscillator.