DESIGN AND CONSTRUCTION OF A FAR-INFRARED FREE-ELECTRON LASER-DRIVEN BY A MICROTRON

A far-infrared free-electron laser driven by a microtron has been deve loped. The free-electron laser system is continuously tunable in the w avelength 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 i n a macropulse is 50 mA. In order to get high enough gain of the free electron laser, we developed a long electromagnetic undulator with hig h 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 undul ator is tunable from 4 to 6 kG at a fixed gap distance of 5 mm by chan ging the current through the electromagnet. More than 99% of the elect ron beam passed through the undulator. The results of numerical simula tion show that the measured parameters of electron beam are good enoug h for lasing. Critical issues in lasing of the free-electron laser are discussed. (C) 1998 Elsevier Science B.V. All rights reserved.