First microwave generation in the FOM free-electron maser

TitleFirst microwave generation in the FOM free-electron maser
Publication TypeJournal Article
Year of Publication1998
AuthorsA.GA Verhoeven, W.A Bongers, V.L Bratman, M. Caplan, G.G Denisov, C.AJ van der Geer, P. Manintveld, A.J Poelman, J. Pluygers, M.Y Shmelyov, P.HM Smeets, A.B Sterk, W.H Urbanus
JournalPlasma Physics and Controlled Fusion
Date PublishedAug
ISBN Number0741-3335

A free-electron maser (FEM) has been built as a pilot experiment for a millimetre-wave source for applications on future fusion research devices such as ITER, the International Tokamak Experimental Reactor. A unique feature of the Dutch fusion FEM is the possibility to tune the frequency over the entire range from 130 to 260 GHz at an output power exceeding 1 MW. In the first phase of the project, the so-called inverse set-up is used. The electron gun is mounted inside the high-voltage terminal. The entire beam line was tested successfully with extremely low loss current, lower than 0.05%. The first generation of millimetre waves was achieved in October 1997. The highest peak power measured so far is 700 kW at 200 GHz. This was achieved with a beam current of 8 A and an acceleration voltage of 1.77 MV. The output power, start-up time and frequency correspond well with the simulation results. The parameter scans for the longitudinal undulator gap. acceleration voltage and reflection coefficient have given a wide range of interesting data of which a few highlights are given.



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