K. "Ogura

T." Shimozuma

National Institute for Fusion Science (NIFS-Repository)

i) ObjectivesIn LHD experiments, a Mega-Watt millimeter wavesystem is used for strong electron heating. In thesedays, millimeter wave and Tera-Hertz wave oscillatorsand some components have been progressively devel-oped and applied to material and medical sciences. Par-ticularly, electron beam devices realize not only highpower and/or steady-state output, eg. gyrotrons andfree-electron lasers, but Tera-Hertz output using high-harmonic operation. Besides, a new high-power andhigh-frequency oscillator using a high-current electronbeam is extensively studied.The objective of this workshop is to encourage theexchange of the state-of-the art informations among theresearchers of MM & Tera-Hertz waves and microwavetechnologies, for the improvement in each ﬁeld and thedevelopment of combined research ﬁelds.ii) Activities in FY2010In this ﬁscal year, we intended to make intensivediscussion of the latest research results and the new re-search trend of the generation, detection and applicationof MM & Tera-Hertz waves.We had a workshop on plasma heating and diag-nostics in February 22nd, 2011 under the keywords of ?High power millimeter and Tera-Hertz wave source us-ing a intense electron beam?. The workshop is organizedby three topical lectures and three reports as listed be-low. The participants distributed over wide area relatedto the millimeter wave technology. About 22 membersjoined the workshop. The viewgraphs of each presenta-tions were summarized in the CD-ROM for convenience.Presentations: Lectures1. ?For Development of a Tera-Hertz Gyrotron?byProf. Weihua Jiang, Extreme Energy-Density Re-search Institute (EDI), Nagaoka University of Tech-nologyFor the purpose of Tera-Hertz generation and itsapplication, the development of a Large Orbit Gy-rotron (LOG) using a relativistic electron beam ispromoted under a collaboration between EDI of Na-gaoka Univ. of Tech. and FIR Center of Univ. ofFukui. In the experiment, a pulsed electron beamwith the energy of 400 keV was generated by apulsed power generator ”ETICO-IV” and injectedinto a cavity with a magnetic ﬁeld up to 8 T, beingcontrolled the beam shape and the pitch factor. Agenerated electromagnetic wave had a frequency of130-140 GHz and over 1 MW output power. Simu-lation results by 3 dimensional PIC code indicatedpossible oscillation mode of TE14 and TE46.2. ?Coherent Monochromatic Cherenkov RadiationGeneration in THz Range by Femtosecond ElectronBunches in Impurity-Doped Semiconductor Tube?by Dr. A. Ogata, Institute of Scientiﬁc and Indus-trial Research, Osaka UniversityA Cherenkov radiation can be generated when anelectron beam passes through a dielectric-coatedmetal cylinder. When three lengths, that are theplasma wavelength of the dielectric, the radius ofthe tube and the bunch length of the electron beam,synchronize each other around a Tera-Hertz wave-length, a strong THz radiation can be resonantlygenerated, and its frequency becomes discrete. Ifthe bunch length is shorter than that of the radi-ated wave, the radiation becomes coherent and theintensity is proportional to N2, where N is the num-ber of electrons included in the bunch. It is possibleto obtain a quasi-coherent radiation by selecting pa-rameters so that only the lowest component may bedominant.3. ?Generation of a Quasi-Coherent THz Wave by Co-herent Cherenkov Radiation?by Dr. K. Kan, In-stitute of Scientiﬁc and Industrial Research, OsakaUniversityCoherent Cherenkov Radiation (CCR) is a methodin which a Cherenkov radiation generated by a elec-tron beam is conﬁned in the dielectric material anda strong coherent THz wave can be generated. Thecoherent THz wave could be applied to the sourcefor material probing and imaging. On the other side,the technology of short pulse electron beams is alsoapplied to the strong electromagnetic wave gener-ation and the femto-second pulse radiolysis. Theyintroduced their S-band linac with a photo-cathodeRF electron-gun and the generation of femto-secondelectron beams. A THz wave generation using ultra-short pulse bunched electron beams was also re-ported.Presentations: Reports1. ?Development of a High Power Sub-Tera HertzPulsed Gyrotron” by Dr. T. Saito, Research Centerof FIR, Univ. Fukui.2. ?Eﬃcient Electro-Optic Sampling Detection ofTera-Hertz Radiation via Cherenkov Phase Match-ing?by Dr. M. Tani, Research Center of FIR, Univ.Fukui.3. ?Electron Bernstein Wave Heating in the MicrowaveSpherical Tokamak, LATE?, by Dr. M. Uchida,Kyoto Univ.183§26. High Power Millimeter and Tera-Hertz Wave Source Using an Intense Electron BeamOgura, K. (Univ. Niigata), Shimozuma, T.

High Power Millimeter and Tera-Hertz Wave Source Using an Intense Electron Beam

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