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SCIENTIA SINICA Informationis, Volume 47 , Issue 12 : 1741-1751(2017) https://doi.org/10.1360/N112016-00223

Terahertz broadband tunable pulse gyrotron

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  • ReceivedNov 23, 2016
  • AcceptedMar 2, 2017
  • PublishedAug 14, 2017

Abstract

Based on the principle of a relativistic electron cyclotron maser, gyrotrons can generate high-power coherent radiation in the millimeter-terahertz (THz) waveband. A pulse magnet can generate an ultra-high field strength, and simultaneously reduces the volume by several times compared with a conventional superconducting magnet, which promotes a THz gyrotron to break the 1 THz barrier. However, only an extremely short duration around the peak field of the pulse magnet can be used for a conventional open-cavity gyrotron fixed-frequency operation. In this letter, a novel gyrotron interaction scheme is proposed to excite the broadband THz radiation by integrating a broadband pre-bunched interaction circuit with a pulse magnet, which is a promising way to expand the frequency tuning bandwidth, enlarge the magnetic field by utilizing the range of the pulse magnet, extend the operating pulse duration of a gyrotron, and realize the quasi-continuous operation of a pulse magnet gyrotron. After an investigation into the frequency and time domains, a broadband pulse gyrotron driven by a 20 kV low-voltage electron beam is predicted to generate radiation with a frequency of between 0.328 and 0.338 THz, with a peak power of 2.1 kW in a 6 ms pulse duration.


Funded by

国家自然科学基金(61531002,61522101,61471007)

北京市科技新星计划(Z161100004916057)

华中科技大学脉冲强磁场实验装置开放课题(2015KF13)


Acknowledgment

感谢俄罗斯科学院应用物理所Michael I. Petelin教授以及Andrey V. Savilov教授给予的有益讨论.


References

[1] Chu K R. The electron cyclotron maser. Rev Mod Phys, 2004, 76: 489--540. Google Scholar

[2] Nusinovich G S, Thumm M K A, Petelin M I. The gyrotron at 50: historical overview. J Infr Millim Terahertz Waves, 2014, 35: 325--381. Google Scholar

[3] Sakamoto K, Kasugai A, Takahashi K, et al. Achievement of robust high-efficiency 1 MW oscillation in the hard-self-excitation region by a 170 GHz continuous-wave gyrotron. Nature Phys, 2007, 3: 411--414. Google Scholar

[4] Notake T, Saito T, Tatematsu Y, et al. Development of a novel high power sub-THz second harmonic gyrotron. Phys Rev Lett, 2009, 103: 225002. Google Scholar

[5] Saito T, Nakano T, Hoshizuki H, et al. Performance test of CW 300 GHz gyrotron FUCWI. Int J Infrared Millime Waves, 2007, 28: 1063--1078. Google Scholar

[6] Saito T, Tatematsu Y, Yamaguchi Y, et al. Observation of dynamic interactions between fundamental and second-harmonic modes in a high-power sub-terahertz gyrotron operating in regimes of soft and hard self-excitation. Phys Rev Lett, 2012, 109: 155001. Google Scholar

[7] He W, Donaldson C R, Zhang L, et al. High power wideband gyrotron backward wave oscillator operating towards the terahertz region. Phys Rev Lett, 2013, 110: 165101. Google Scholar

[8] Nanni E A, Barnes A B, Griffin R G, et al. Thz dynamic nuclear polarization NMR. IEEE Trans Terahertz Sci Tech, 2011, 1: 145--163. Google Scholar

[9] Thumm M. High power gyro-devices for plasma heating and other applications. Int J Infrared Millim, 2005, 26: 483--503. Google Scholar

[10] Sims J R, Rickel D G, Swenson C A, et al. Assembly, commissioning and operation of the NHMFL 100 Tesla multi-pulse magnet system. IEEE Trans Appl Supercon, 2008, 18: 587--591. Google Scholar

[11] Idehara T, Tsuchiya H, Watanabe O, et al. The first experiment of a THz gyrotron with a pulse magnet. Int J Infrared Millim, 2006, 27: 319--331. Google Scholar

[12] Idehara T, Saito T, Mori H, et al. Long pulse operation of the THz gyrotron with a pulse magnet. Int J Infrared Millim, 2008, 29: 131--141. Google Scholar

[13] Glyavin M Y, Luchinin A G. A Terahertz gyrotron with pulsed magnetic field. Radiophys Quantum Electron, 2007, 50: 755--761. Google Scholar

[14] Glyavin M Y, Luchinin A G, Golubiatnikov G Y. Generation of 1.5-kW, 1-THz coherent radiation from a gyrotron with a pulsed magnetic field. Phys Rev Lett, 2008, 100: 015101. Google Scholar

[15] Glyavin M Y, Luchinin A G, Nusinovich G S, et al. A 670 GHz gyrotron with record power and efficiency. Appl Phys Lett, 2012, 101: 153503. Google Scholar

[16] Glyavin M Y, Luchinin A G, Bogdashov A A, et al. Experimental study of the pulsed Terahertz gyrotron with record-breaking power and efficiency parameters. Radiophys Quantum Electron, 2014, 56: 497--507. Google Scholar

[17] He W, Cross A W, Phelps A D R, et al. Theory and simulations of a gyrotron backward wave oscillator using a helical interaction waveguide. Appl Phys Lett, 2006, 89: 091504. Google Scholar

[18] Chang T H, Fan C T, Pao K F, et al. Stability and tunability of the gyrotron backward-wave oscillator. Appl Phys Lett, 2007, 90: 191501. Google Scholar

[19] Chen N C, Yu C F, Yuan C P, et al. A mode-selective circuit for TE01 gyrotron backward-wave oscillator with wide-tuning range. Appl Phys Lett, 2009, 94: 101501. Google Scholar

[20] Kou C S, Chen C H, Wu T J. Mechanisms of efficiency enhancement by a tapered waveguide in gyrotron backward wave oscillators. Phys Rev E, 1998, 57: 7162--7168. Google Scholar

[21] Chen N C, Chang T H, Yuan C P, et al. Theoretical investigation of a high efficiency and broadband subterahertz gyrotron. Appl Phys Lett, 2010, 96: 161501. Google Scholar

[22] Qi X B, Du C H, Liu P K. Broadband continuous frequency tuning in a Terahertz gyrotron with tapered cavity. IEEE Trans Electron Devices, 2015, 62: 4272--4278. Google Scholar

[23] Du C H, Qi X B, Kong L B, et al. Broadband tunable pre-bunched electron cyclotron maser for Terahertz application. IEEE Trans Terahertz Sci Tech, 2015, 5: 236--243. Google Scholar

[24] Nusinovich G S, Pu R F, Granatstein V L. Suppression and nonlinear excitation of parasitic modes in second harmonic gyrotrons operating in a very high order mode. Appl Phys Lett, 2015, 107: 013501. Google Scholar

[25] Du C H, Liu P K. Beam-wave coupling strength analysis in a gyrotron traveling-wave amplifier. J Infr Millim Terahertz Waves, 2010, 31: 714--723. Google Scholar

[26] Qi X B, Du C H, Liu P K. High-efficiency excitation of a third-harmonic gyrotron. IEEE Trans Electron Devices, 2015, 62: 3399--3405. Google Scholar

[27] Du C H, Qi X B, Luo L, et al. Development of a 0.33 THz pulse gyrotron. In: Proceedings of IEEE International Vacuum Electronics Conference, Beijing, 2015. 1--2. Google Scholar

[28] Du C H, Qi X B, Liu P K. Broadband THz gyrotron based on a pulse magnet. In: Proceedings of the 40th International Conference on Infrared, Millimeter, and Terahertz Waves, Hong Kong, 2015. 1--2. Google Scholar

[29] Du C H, Qi X B, Liu P K. Theoretical study of broadband quasi-optical mode converter for pulse gyrotron devices. IEEE Trans Plasma Sci, 2016, 10: 2348--2355. Google Scholar

[30] Bandurkin I V, Kalynov Y K, Savilov A V. Experimental study of a gyrotron with a sectioned klystron-type cavity operated at higher cyclotron harmonics. Radiophys Quantum Electron, 2016, 58, 694--700. Google Scholar

[31] Flyagin V A, Gaponov A V, Petelin M I, et al. The gyrotron. IEEE Trans Microw Theory Tech, 1977, 25: 514--521. Google Scholar

[32] Kou C S, Wu M H, Tseng F. Nonlinear analysis of a multi-cavity gyro-twystron. Int J Infrared Millim Waves, 1997, 78: 1857--1883. Google Scholar

  • Figure 1

    (Color online) (a) Circuit profiles of pre-bunched circuit andopen-cavity circuit with axial magnetic field distribution, where line 1indicates the pre-bunched circuit profile, line 2 indicates the open-cavitycircuit profile, $f_~-$ indicates backward wave, and $~f_~+~$ indicatesforward wave; (b) axial interaction efficiencies $\eta~$ in different circuitswhen the gyrotron operates in backward interaction region at 330.1 GHz; (c)and (d) are axial field profile $f_{\rm~total}$, forward wave $f_+~$ and backwardwave $f_-$ in open-cavity circuit and pre-bunched circuit, respectively,when the gyrotron operates in backward interaction region at 330.1 GHz

  • Figure 2

    (Color online) Axial field profile $f_{\rm~total}$, forward wave $f_~+~$ andbackward wave $f_~-~$ in pre-bunched circuit when the TE$_{62~+~}$ modegyrotron operates at different magnetic fields (a) $B_0~=~12.0$ Tcorresponding to frequency $f$ = 328 GHz, (b) $B_0~=~12.4$ T corresponding tofrequency $f$ = 330 GHz, (c) $B_0~=~12.9$ T corresponding to frequency $f$ = 337GHz

  • Figure 3

    (Color online) Interaction efficiency and the continuous frequency tuningband of the TE$_{6,2~+~}$ mode gyrotron with electron beam voltage $V_b~=20$ kV and current $I_b~=~0.5$ A, assuming pitch factor $\alpha~=~{v_t~}/{v_z~}=~1.5$, guiding center $r_c~=~0.905$ mm,and guiding center spread ${\Delta~r_c~}/{r_c~}=~5%$ duringthe magnetic field tuning

  • Figure 4

    (Color online) Beam-wave coupling impedances of the potential oscillatingmodes

  • Figure 5

    (Color online) Measured half-sinusoidal distribution time-varyingmagnetic field strength generated by the pulse magnet, where the pulseduration is about 24 ms, and about 6 ms could be utilized for gyrotronoperating (blue region), while an extremely short duration could be used forconventional gyrotron operating (orange region)

  • Figure 6

    (Color online) Frequency spectrum of multimode simulation withtime-varying magnetic field and changing electron beam parameters. Pitchfactor varies between $\alpha~=~{v_t~}/~{v_z~}=~1.75~\sim~1.1$, velocityspread ranges between ${\Delta~v_z~}/~{v_z~}=~8%~\sim~5.5%~$, andconstant guiding center $r_c~=~0.905$ mm$_{~}$and guiding center spread${\Delta~r_c~}/~{r_c~}=~5%$ during the magnetic fieldtuning

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