|Measurement of the Output Power in Millimeter Wave Free Electron Laser using the Electro Optic Sampling Method
Funding: this work funded in part by Israel Minstry of Defence
In this experimental work an electro optic (EO) sampling method was demonstrated as a method to measure the output power of an Electrostatic Accelerator Free Electron Laser (EA-FEL). This 1.4 MeV EA-FEL was designed to operate at the millimeter wavelengths and it utilizes a corrugated waveguide and two Talbot effect quasi-optical reflectors with internal losses of ~30%. Millimeter wave radiation pulses of 10 μs at a frequency of about 100 GHz with peak power values of 1-2 kW were measured using conventional methods with an RF diode. Here we show the employment of an electro-optic sampling method using a ZnTe nonlinear crystal. A special quasi optical design directs the EA-FEL power towards the ZnTe nonlinear crystal, placed in the middle of a cross polarized configuration, coaxially with a polarized HeNe laser beam. The differences in the ZnTe optical axis due to the EA-FEL power affects the power levels of the HeNe laser transmission. This was measured using a polarizer and a balanced amplifier detector. We succeeded in obtaining a signal which corresponds to the theoretical calculation.
|Narrow Linewidth, Chirp-Control and Radiation Extraction Optimization in an Electrostatic Accelerator FEL Oscillator
|In recent years the electrostatic accelerator FEL based in Ariel has undergone many upgrades. By varying the accelerating potential the resonator allows lasing between 95-110 GHz. It is now possible to remotely control the output reflectivity of the resonator and thereby vary both the power built up in the resonator and that emitted. This has allowed fine control over the power for different user experiments. A voltage ramping device has been installed at the resonator/wiggler to correct drops in voltage which occur due to electrons striking the walls of the beam line. This has allowed stable pulses of just over 50 μs with a chirp rate of ~80 kHz/μs.