(Invited Paper) Generation of High Power THz Waves in Relativistic Electron Beam Plasma and Two-Sheet-Beam FEM

M.K.A. Thumm ^{1*, 5*}, A. V. Arzhannikov ^{1, 2}, V.T. Astrelin ^{1, 2}, A.V. Burdakov ^1-3, N.S. Ginzburg ⁴, I.A. Ivanov ^{1, 2}, P.V. Kalinin ^{1, 2}, S. A. Kuznetsov ^{1, 2}, M.A. Makarov ², K. I. Mekler ², A.G. Paulish ¹, N. Yu. Peskov ⁴, S. V. Polosatkin ^{1, 2}, S.A. Popov ², V. V. Postupaev ^{1, 2}, A. F. Rovenskikh ², A.S. Sergeev ⁴, S. L. Sinitsky ^{1, 2}, V. F. Sklyarov ^{2, 3}, V.D. Stepanov ^{1, 2}, L. N. Vyacheslavov ^{1, 2}, V. Yu. Zaslavsky ^4
1 Novosibirsk State University (NSU), Novosibirsk, Russia
² Budker Institute of Nuclear Physics (BINP) SB RAS, Novosibirsk, Russia
³ Novosibirsk State Technical University (NSTU), Novosibirsk, Russia
⁴ Institute of Applied Physics (IAP) RAS, Nizhny Novgorod, Russia
⁵ Karlsruhe Institute of Technology (KIT), IHM, Karlsruhe, Germany
^*1 Email: thumm@nsm.nsu.ru; ^*5 Email: manfred.thumm@kit.edu

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Abstract: Sub-mm wave and THz radiation can be generated by the process of transformation of plasma waves into electromagnetic (EM) radiation at strong Langmuir (LT) turbulence via a two-stream instability induced by a propagating high current relativistic electron beam (REB). Plasmon scattering on plasma density fluctuations yields EM emission at the plasma frequency w_p ("w_p?process"). Nonlinear plasmon-plasmon merging results in the generation of photons nearby the 2^nd harmonic of the plasma frequency 2w_p ("2w_p?process"). For plasma densities 10¹⁴-10¹⁵ cm^-3, corresponding radiation frequencies are located in the range of sub-mm waves: 180-566 GHz. The power density of LT-induced sub-mm-wave emission from plasmas in the multi-mirror trap GOL-3 (BINP) during injection of a 10-ms-REB at plasma densities n_e » 5?10¹⁴ cm^-3 , electron temperatures T_e » 1.5 keV and magnetic field B » 4 T was measured to be up to 5-10 kW/cm³ in the frequency band above 100 GHz.

Former experiments on the ELMI device (BINP) demonstrated the operation of an mm-wave single channel free electron maser (FEM) with planar cavity geometry and 2D distributed feedback. Measurements have shown single mode single-frequency generation (75 GHz) with about 300 ns pulse duration at the power level of 20-40 MW. In the case of two parallel sheet electron beams in two slit channels, we plan to investigate an inter-cavity scattering scheme for two-stage generation of sub-mm wave radiation. As a first step we have studied simultaneous generation and transport of two intense sheet electron beams in two FEM slit channels. The REB parameters were the following: electron energy 0.8 MeV, total current of each beam 3 kA, cross section 0.4 cm x 7 cm and pulse duration 3 ms. The measurements of the energy of the mm-wave radiation pulse for frequencies higher than 70 GHz gave a value of 4-6 J and the average power of 20-40 MW from each of the two FEM channels.

Both the GOL-3 and FEM experiments need components and systems for spectral diagnostics of sub-mm wave radiation. Novel micro-structured quasi-optical elements have been developed where amplitude, phase and polarization responses are controlled by frequency selective surface (FSS) topologies, manufactured by photolithography and electroforming. Bandpass filters (70 mm aperture diameter) with center frequency (CF) from 112 to 376 GHz show > 90% transmission and have a FWHM bandwidth of ~ 12%. Meta-material absorbers for real-time THz imaging (CF from 310 to 370 GHz) have an absorption of > 90% and excellent thermal insulation.

Keywords:Terahertz generation and spectroscopy, Electron beam plasma, Free electron maser, Frequency selective surfaces.

Received: 2011-12-23

Published: 2012-3-31

Acknowledgments: Herewith we gratefully acknowledge the support of this research by the Russian Federation Government Grants No. 11.G34.31.0033 and NSh 7792.2010.2, by the Contract #16.740.11.03.77 of the Ministry Education and Science of the Russian Federation, by the contract 16.740.11.0377 of the Federal Target Program, and by the Program 30 of Russian Academy of Sciences. We also acknowledge A.V. Gelfand, Dr. M. A. Dem'yanenko and M.A. Astafyev for technological support in manufacturing FSS structures and in THz measurements

Cite this article:
M.K.A. Thumm, A. V. Arzhannikov, V.T. Astrelin, A.V. Burdakov, N.S. Ginzburg, I.A. Ivanov, P.V. Kalinin, S. A. Kuznetsov, M.A. Makarov, K. I. Mekler, A.G. Paulish, N. Yu. Peskov, S. V. Polosatkin, S.A. Popov, V. V. Postupaev, A. F. Rovenskikh, A.S. Sergeev, S. L. Sinitsky, V. F. Sklyarov, V.D. Stepanov, L. N. Vyacheslavov, V. Yu. Zaslavsky. (Invited Paper) Generation of High Power THz Waves in Relativistic Electron Beam Plasma and Two-Sheet-Beam FEM[J]. International Journal of Terahertz Science and Technology, 2012, Vol.5, No.1: 18-39.  DOI:10.11906/TST.018-039.2012.03.03

URL: http://www.tstnetwork.org/10.11906/TST.018-039.2012.03.03