FIRST OPERATION OF THE NEW THz SOURCE "FEL-CATS"

The members of the ENEA team, A.Doria, G.P. Gallerano, E.Giovenale, G. Messina, C. Ronsivalle, I Spassovsky, are pleased to announce tunable operation of a new Free-Electron THz source in the spectral region between 0.3 and 0.7 THz (wavelength from 1 mm to 400 micrometers) with a relative linewidth of 10% FWHM.

Peak power in the 100 kW range has been estimated in 3 ps pulses spaced at a repetition frequency of 3 GHz. A 5 microsecond long train of such pulses (macropulse) is generated and repeated at a rate of 1 Hz. The measured power in the macropulse is around 1 kW. The rep rate is presently limited by the power supply of the electron gun.

The principle of operation of the source is based on the coherent spontaneous emission from short bunches of relativistic electrons. The FEL source utilizes a 3 MeV RF linac to generate the electron beam, which is injected into a magnetic undulator composed of 16 periods, each 2.5 cm long. A second RF structure, called Phase Matching Device (PMD), is inserted between the linac and the undulator and is controlled in phase and amplitude to correlate the electron distribution in energy as a function of time in the bunch. In this way the contributions to the total radiated field by individual electrons in the bunch are added in phase, leading to a manyfold enhancement of the coherent emission.

We have named the new source FEL-CATS (Compact Advanced THz Source). It is a laboratory scale device, which fits into an area of 1m x 2m. Starting early Spring 2003 it will be used in addition to the existing Compact FEL for the study of the interaction of THz radiation with biological systems in the frame of the THz-BRIDGE project.

With best wishes from the ENEA team.