The Project of High Power Submillimetr-Wavelength Free Electron Laser

(TU-4-05)

V.P.Bolotin, N.G. Gavrilov, D.A. Kairan, M.A. Kholopov, E.I. Kolobanov, V.V. Kubarev, G.N. Kulipanov, S.V. Miginskiy,  

L.A. Mironenko, A.D. Oreshkov, M.V. Popik, T.V. Shaftan, M.A. Sheglov, O.A. Shevchenko, A.N. Skrinskiy, N.A. Vinokurov,P.D. Vobly.

A 100-MeV 8-turns accelerator-recuperator intended to drive a high-power infrared FEL is under construction in Novosibirsk now. The first stage of the machine includes an one turn accelerator-recuperator, that contains full RF-system, but reduced number of turns.

RF wavelength, m 1.66
Number of RF cavities 16
Amplitude of accelerating voltage at one cavity, MV 0.8
Injection energy, MeV 2
Final electron energy, MeV 14
Bunch repetition frequency, MHz 2 - 22.5
Average current, mA 4 - 50
Final electron energy dispersion, % 0.2
Final electron bunch length, ns 0.02 - 0.1
Final peak electron current, A 50 - 10

The FEL structure on the single backward turn of the accelerator-recuperator consists of two undulators, a buncher, two mirrors of optical resonator, and an outcoupler. Both undulators are identical. They are electro-magnetic planar ones, of length 4 m, period 120 mm, gap 80 mm, and K up to 0.8. One can use one or both undulators with or without the buncher. Both mirrors are identical, spherical, made of polished copper, and water cooled. The outcoupler contains two or four adjustable planar copper mirrors. These mirrors scrape radiation inside the optical resonator and redirect small part of it to the consumer. This scheme preserves the main mode of optical resonator well and reduces amplification of higher modes effectively. The buncher is simply a three-pole electro-magnetic wiggler.

Then one should expect the following parameters of the FEL radiation:

Wavelength., mm 0.1...0.2
Pulse length, ns 0.02...0.1
Peak power, MW 1...7
Average power, kW 0.6...7