Design and construction of a far-infrared free-electron laser driven by a microtron

Abstract

A far-infrared free-electron laser driven by a microtron has been developed. The free-electron laser system is continuously tunable in the wavelength range from 30 to 50 mu m. The energy of the electron beam is 7.5 MeV at maximum. The pulse duration and the repetition rate of the macropulses are 5 mu s and 10 Hz, respectively. The average current in a macropulse is 50 mA. In order to get high enough gain of the free electron laser, we developed a long electromagnetic undulator with high magnetic field strength. The period of the undulator is 12.5 mm and the number of the periods is 160. The peak magnetic field of the undulator is tunable from 4 to 6 kG at a fixed gap distance of 5 mm by changing the current through the electromagnet. More than 99% of the electron beam passed through the undulator. The results of numerical simulation show that the measured parameters of electron beam are good enough for lasing. Critical issues in lasing of the free-electron laser are discussed. (C) 1998 Elsevier Science B.V. All rights reserved.