NEWSLETTERof the International Consortium“Development of High-Power Terahertz
Science & Technology”
February 2020

№ 14

CONTENT Editorial(Page 1)

How to contribute to the Newsletter Invited paper(Pages 2)
A.P. Fokin, A.I. Tsvetkov, V.N. Manuilov, A.S. Sedov, and M.Yu. Glyavin, “Control of sub-terahertz
gyrotron frequency by modulation of the anode voltage”
 Upcoming events (conferences and workshops)(Page 6)
 Personalia: Professor M. Glyavin(Page 7)
 List of selected recent publications, patents, and new books(Page 8)
 News from the Net (our broader horizons)(Page 18)

EDITORIAL: HOW TO CONTRIBUTE TO THE NEWSLETER
Dear Reader,
We are inviting contributions to the following rubrics:• Research highlights (annotations) presenting the projects pursued by the members of the Consortium.
• Short regular and invited papers.
• Proposals for collaborative research work.
• News from the participating institutions.
• Information about conferences, symposia, workshops, seminars.
• Programs and frameworks for an exchange of visits and mobility of researchers. Job opportunities(especially for young researchers, e.g. postdoctoral positions, specializations, internships).
• Annotations of books, conference proceedings, software and internet resources. Additions to the list of
the recent scientific publications and conference reports at the website of the Consortium(http://fir.ufukui.ac.jp/Website_Consortium/publist.html ).
• Information and announcements about awards and nominations.
• Short presentations of laboratories and research groups belonging to the participating institutions.
Please submit your contributions to the Newsletter as well as requests for information to:Professor Masahiko Tani
Director of FIR UF – Facilitator of
the International Consortium
FIR UFtani@fir.u-fukui.ac.jp

Dr. Svilen Sabchevski
Editor of the website and the Newsletter
Institute of Electronics of the Bulgarian
Academy of Sciencessabch@ie.bas.bg

SHORT INVITED PAPER
Control of sub-terahertz gyrotron frequency by modulation of the anode voltage
A.P. Fokin, A.I. Tsvetkov, V.N. Manuilov, A.S. Sedov, and M.Yu. Glyavin
Institute of Applied Physics of the Russian Academy of Sciences, N. Novgorod, Russia

Gyrotrons are well known as the powerful radiation sources in sub-THz and THz frequency ranges.
Together with power and efficiency, for some applications, for instance, those associated with spectroscopy anddiagnostics of various media, a CW oscillation regime with narrow radiation spectrum and smooth wideband
oscillation frequency tuning are highly sought for. In this case, the gyrotron output power would still be several
orders higher than the power of classical BWOs and solid-state oscillators thus uncovering brand new
possibilities for research. Thus, in order to satisfy the growing demands of modern applications, it is necessary
to pay more attention to the methods of frequency control in gyrotrons.
The active methods of frequency control include several relatively slow methods like variation of magnetic
field, cavity temperature, and cavity radii as well as faster methods of voltage variation on the electrodes theelectron-optic system, namely accelerating voltage, cavity voltage (in the gyrotrons with electron energy
recovery) or modulation-anode voltage in triode-type magnetron injection guns. The latter seems to be most
reasonable since the voltage is varied at the isolated electrode, the capacitance of which is relatively small withrespect to other electrodes of the electron-optical system and is usually about tens of picofarad. Moreover, themod-anode current is low and so the corresponding power supply can be small, simple and cheap. A number ofexperiments (including FIR UF and IAP RAS groups) with gyrotrons of different frequencies demonstrated its
simplicity, reliability, modulation frequency up to hundreds of kHz and paved the way for record frequency
stability of the gyrotron. The objective of this report is to compare theoretical calculations with experimental
results in order to draw a conclusion about the existence of a theory that can accurately describe the process of
frequency control by variation of modulation-anode voltage.
The theory of frequency pulling in gyrotrons is based on the basic theory developed by L. A. Weinstein with
V. A. Solntsev, who considered the excitation of oscillations in a resonator excited by an electron beam with



the current density j  t   Re j   eit

 and introduced the complex power of beam-wave interaction

P  Pact  iPim . In terms of components of such complex power, equations describing the stationary oscillationsin any resonator can be reduced to the equation describing the balance of active powers and the equation
describing the reactive power. The first one determines the amplitude of oscillations excited by an electron
beam in a resonator with a given Q-factor; the second one (describing the balance of reactive powers)
determines the shift of the oscillation frequency with respect to the real part of the complex eigenfrequency of a

cold cavity s  s  is / 2Qs ( s is the mode index), i.e. the frequency pulling effect. In notations adopted in
the gyrotron theory, the same effects can be described by using the susceptibility of an electron beam to theelectromagnetic field of a resonator      i   . The relation between this susceptibility and the complex
power can be given as:

I 

iQ
P
sW

(1)

In (1), I is the normalized beam current parameter, W is the microwave energy stored in a resonator. In thenotations adopted in the gyrotron theory, corresponding balance equations can be given as:I    1(2)

  s I  s / 2Qs

(3)

Note that in the framework of this theory the susceptibility  depends on three dimensionless parameters only:
the cyclotron resonance mismatch  , the normalized length of the interaction space  and the normalized
amplitude of oscillations in the resonator F ; the latter, in accordance with Eq. (2) depends, in turn, on the
beam current parameter I . For our treatment, it is important that all three parameters depend on thecomponents (orbital and axial) of the electron velocity. In particular, and possibly the most important, is thedependence in the transit angle     s0  L / vz  , which is the product of the mismatch and the normalizedinteraction length    . Therefore, the variation in the modulation-anode voltage, which is considered below,
causes the variation in the transit angle that has a strong effect on the electron bunching and resulting gyrotron
output frequency and power.
For the method of modulation-anode voltage control, the electron energy, which is determined by theaccelerating voltage (cathode-cavity potential), remains constant, and a change of the mod-anode potential
affects only on an electrons pitch-factor g (relation between orbital and axial velocities of electrons). Therefore,
in order to calculate the frequency shift, it is important to know the components of electron velocity with highenough accuracy and utilize the adequate model of beam-wave interaction (the one that takes into account thegreatest number of effects and at the same time with reasonable calculation time). The authors use a "classical"
approach – divide the problem into two sub-problems that can be solved independently using relatively simple
models for which the computation time is orders of magnitude less than for the packages described above. The
first problem is the calculation of the parameters of the electron beam formed in the axially symmetricmagnetron-injection gun with a varying mod-anode voltage and the second is the calculation of the interactionof the resulting electron beam with the electromagnetic field in the gyrotron cavity in a self-consistent model ofa gyrotron with non-fixed field structure. The numerical simulation and subsequent comparison with theexperiment was made for a real tube with a frequency of 263 GHz and an output power of 1 kW, which wasdeveloped at IAP RAS.

The calculation of electron-wave interaction was made by using the self-consistent steady-state single-mode
equations. The model with a non-fixed longitudinal RF-field structure f(z) takes into account the electron
velocity and guiding center spread, non-uniform magnetic field and the real resonator profile. The transverse
drift of electron orbit centers, RF space charge and re-radiation of the operating mode into modes with different
radial indexes were not taken into account since at optimal gyrotron parameters their influence is negligibly
small. The calculated value of the pitch-factor is substituted into the energy conservation law and thecorresponding values of electrons oscillatory p  p0 and longitudinal pz  p z 0 momentums at the entrance ofthe cavity were obtained. These values are then used as initial ones for microwave field calculation in thepresence of electron beam. As a result, the generation frequency and total gyrotron efficiency for a set of
considered values U a and magnetic fields were found. The calculated dependencies of the operating gyrotron
frequency and efficiency on the mod-anode voltage variation and magnetic field in the cavity region (cyclotron
resonance mismatch) are shown in Fig.1, 2.

Fig. 1 and 2 Calculated dependencies of the gyrotron operating frequency (left) and gyrotron
efficiency (right) on the magnetic field and anode voltage.
It should be noted that for regimes with high interaction efficiency (in Fig.2 this region corresponds to B
close to 9.6 T) the influence of beam pitch factor on the frequency of microwave radiation is rather low( f U a = 1.3 MHz/kV), while the overall efficiency of the gyrotron varies quite a lot (  U a  5.1 %/kV).
The highest sensitivity of frequency to the variation of mod-anode potential f U a = 30 MHz/kV is
predicted at high magnetic fields (in Fig. 1 this region corresponds to B close to 9.7 T), for regimes with low
interaction efficiency. As it follows from numerical simulation, the optimal regime for spectroscopic gyrotron
would be not the maximum efficiency point, but the middle of the generation zone, since it offers greater
frequency tuning and less output power modulation, as well as a reasonable level of output power about 100
watts.
To verify the obtained results, measurements of the radiation frequency versus modulation-anode voltage
were performed. Keysight N9010A spectrum analyzer with a harmonic mixer in the range 230-320 GHz(produced in Research Institute of Semiconductor Devices) was used (Fig. 3). The experiments were performedat the accelerating voltage of 15 kV and a beam current of 0.1 A to comply with the numerical simulation
conditions. The experiment confirmed the dependence of frequency sweep bandwidth on the operating regime

of the gyrotron with experimentally measured sensitivity of the frequency to the modulation-anode potential
variation ranging from 5 to 30 MHz/kV for minimal and maximal operating magnetic fields. Acquired
dependencies of gyrotron frequency on the mod-anode voltage are in a good agreement with the results of thenumerical simulation. A comparison of the obtained experimental dependency with numerical calculations for a
fixed magnetic field equal to 9.68 T is presented in Fig. 4. The observed discrepancy between theoreticalpredictions and experiment   values is about 3 10 5 , which is an order of magnitude smaller than inprevious work (I.Antakov, et al., Int. J. Infrared Millimeter Waves, 14, 5, 1001–1015, 1993).

Fig.3 Scheme of the gyrotron, power supply connections and measurement system

Fig.4. Comparison of the theoretical and experimental results for frequency shift caused by the anode voltage
variation for a fixed magnetic field (initial value of mod-anode voltage Ua = 13 kV, B = 9.68 T).
The results of numerical simulation of the gyrotron frequency and efficiency in the simple two-step scheme
are in agreement with the experimentally observed dependencies of the frequency shift on the modulationanode voltage variation and the generation regime. Observed discrepancy between theoretical predictions andexperimental results is significantly smaller than in earlier works. It proves the credibility of the simple
theoretical approach to calculation of the gyrotron frequency and power as functions of technical parameters,especially anode voltage, and allows the use of the described method for the development of frequency control
systems for modern high-frequency gyrotrons.
More detail: A.P. Fokin, at al. Rev. Sci. Instrum. 90, 124705 (2019); https://doi.org/10.1063/1.5132831.

FORTHCOMING EVENTSThe Institute of Applied Physics of Russian Academy of Sciences announces that the 11th International
Workshop “Strong Microwaves and Terahertz Waves: Sources and Applications” will be held on July 5–10,
2020 on a river cruise starting and ending in Nizhny Novgorod, Russia.

The side events at the workshop include the 32nd Joint Russian-German Meeting on ECRH and Gyrotrons anda school on high power microwave vacuum electronics for young scientists and PhD students. Traditionally, theworkshop is held aboard a comfortable cruise riverboat. This provides a unique opportunity for the participants
to take a closer look at Russian history and culture. A sightseeing program on the route, a special program foraccompanying persons, and a set of social events are scheduled.
For more detail visit the website of the Workshop.
For more conferences to be held in 2020 visit the preceding issue Newsletter #13.

PERSONALIA
Happy 55th Birthday to Professor Mikhail Glyavin

M. Glyavin was born in Nizhny Novgorod, Russia, on 14 February 1965. He received the Ph.D. degree and Dr.
Sci. degree in physics from the Institute of Applied Physics, Russian Academy of Sciences, in 1999 and 2009,
respectively. After graduation of the Politechnical Institute, Gorky, USSR, in 1988, he joined the Institute ofApplied Physics of the Russian Academy of Sciences (IAP-RAS, where he is engaged in the development ofhigh-power gyrotrons for nuclear fusion and other applications. His dissertation was focused on studies ofgyrotrons, development of gyrotron based systems for technological applications and more specifically on
methods for increasing the gyrotron efficiency and mastering of THz band. From 1999 up to now, at intervals,
he was a Visiting Professor at the FIR FU Center, Fukui, Japan. Currently, he is a Deputy Director of Researchat IAP-RAS, an Associate Professor with Nizhny Novgorod State University, Nizhny Novgorod, Russia, and a
Head of the Laboratory of microwave treatment of materials at IAP-RAS.
M. Glyavin is a leading specialist and worldwide renowned scientist in the fields of radiophysics and physicalelectronics. His research interests are in the field of the theoretical and experimental investigations of various
gyro-devices, including gyrotrons and their application to materials processing and diagnostic of various media.
Among his remarkable results are the following: a study of the processes of interaction of helical electron flows
with eigenmodes of various electrodynamic systems and the proposal of new principles and design of various

gyro-devices; development of a series of technological complexes for microwave processing of materials withincreased efficiency and functionality; the formation of the foundations of a new promising direction - powerfulsources of radiation in the terahertz frequency range. Under his leadership and with his direct participation,
record-breaking frequencies, powers and spectral characteristics of the radiation of gyro devices were achieved
both in pulsed and continuous modes of generation; pioneering work on initiating a localized gas discharge,
experiments on gas spectroscopy with record sensitivity were performed.
M. Glyavin conducts teaching work, supervising graduate students and students, and lecturing at the Universityof Nizhniy Novgorod N.I. Lobachevsky. He manages the collaborative research with the Research Center for
development of the Far-Infrared Region at the University of Fukui (FIR UF) in Japan (FIR FU, Fukui, Japan),and the University of Maryland in the US. He is an active contributor to the research carried out in theframework of the International Consortium for Development of High-Power THz Science and Technology.

LIST OF SELECTED RECENT PUBLICATIONS
Bibliography and links to selected recent publications on topics related to the research field of theInternational Consortium and published after October 2019, i.e. after issuing the previous Newsletter#13. This cumulative list is in chronological order as collected from various bibliographical and alert
services
A. Publications by authors from the institutions participating in the International Consortium
Sidorov A., Razin S., Veselov,A., Vodopyanov A., Morozkin M., Glyavin M., "Breakdown of the heavy noble
gases in a focused beam of powerful sub-THz gyrotron, "Physics of Plasmas, vol. 26,n.8(2019) 083510.
DOI:10.1063/1.5109526.
https://aip.scitation.org/doi/10.1063/1.5109526
Kawasaki T., Izumi Y., Ohori G., H. Kitahara T. Furuya, K., Yamamoto, K. Matsuo, M. Tani, K. Tsukiyama,“Study on Irradiation Effect of Mid-Infrared Free Electron Laser on Hen Egg-White Lysozyme by Using
Terahertz-Time Domain Spectroscopy and Synchrotron-Radiation Vacuum-Ultraviolet Circular-Dichroism
Spectroscopy,” J Infrared, Millimeter, and Terahertz Waves, vol. 40, n. 10 (2019) 998–1009 .
DOI:10.1007/s10762-019-00626-9.
https://link.springer.com/article/10.1007%2Fs10762-019-00626-9
Skalyga V.A., Golubev S.V., Izotov I.V., Lapina R.L., Razina S.V., Sidorova A.V., Shaposhnikova R.A.,“High-Current Pulsed ECR Ion Sources,” Plasma Phys. Rep., vol. 45 (2019) 984.
DOI:10.1134/S1063780X19080087.
https://link.springer.com/article/10.1134/S1063780X19080087
S. Mitsudo, M. Glyavin, E. Khutoryan, I. Bandurkin, T. Saito, Y. Ishikawa, V. Manuilov, I. Zotova, A. Fedotov,
A. Kuleshov, S. Sabchevski1, Y. Tatematsu, V. Zaslavsky, T. Idehara, “An Experimental Investigation of a 0.8
THz Double-Beam Gyrotron,” Journal of Infrared, Millimeter, and Terahertz Waves, vol.40, n. 11–12 (2019)
1114–1128. DOI:10.1007/s10762-019-00629-6.
https://link.springer.com/article/10.1007%2Fs10762-019-00629-6
T. Nawate, Y. Yamamoto, Y. Kanie, S. Mitsudo, Y. Fujii, T. Sakurai, “Electromagnetic-wave sintering ofalumina ceramics from nano-sized particles: possible material for high-pressure cell for millimeter-wave
electron spin resonance,” IOP Conference Series: Materials Science and Engineering, vol. 550 (2019) 012032.
DOI: 10.1088/1757-899X/550/1/012032.
https://iopscience.iop.org/article/10.1088/1757-899X/550/1/012032

V.I. Shcherbinin, V.I. Tkachenko, K.A. Avramidis, J. Jelonnek, "Coaxial Cavity With Stepped Inner Conductor
for a Sub-Terahertz Second-Harmonic Gyrotron With Broadband Continuous Frequency Tuning," in IEEE
Transactions on Electron Devices, vol. 66, 12 (2019) 5313-5320. DOI:10.1109/TED.2019.2944647.
https://ieeexplore.ieee.org/document/8886706
Nowak K., Plinski E., Wieckowski T., Dumbrajs, O., “The gyrotron startup scenario in the single mode timedependent approach,” Mathematical Modelling and Analysis, vol. 24, no. 4 (2019) 494-506.
DOI:10.3846/mma.2019.030.
https://journals.vgtu.lt/index.php/MMA/article/view/7440
Oparina Yu.S., Peskov N.Yu., Savilov A.V., "Electron RF Oscillator Based on Self-Excitation of a Talbot-Type
Supermode in an Oversized Cavity," Phys. Rev. Applied, vol. 12, n. 4 (2019) 044070.
DOI:10.1103/PhysRevApplied.12.044070.
https://journals.aps.org/prapplied/abstract/10.1103/PhysRevApplied.12.044070
Zuev A.S., Zapevalov V.E., Plankin O.P., Semenov E. S., “Optimization of a High-Power Subterahertz
Gyrotron Tunable in a Wide Frequency Range Allowing for the Limitations Imposed by the Magnetic System,”Radiophysics Quantum Electronics, vol. 62, n.4 (2019) 277–285. DOI: 10.1007/s11141-019-09976-9.
https://link.springer.com/article/10.1007/s11141-019-09976-9
Tsvetkov A.I., Vodopyanov A.V., Mansfeld D.A., Fokin A.P., “The Temperature Behavior of Microwave
Absorption of Metal Oxide Powders When Heated by a 263-GHz Gyrotron Radiation,” J Infrared, Millimeter,
and Terahertz Waves, vol. 40, n. 10 (2019) 991. DOI:10.1007/s10762-019-00622-z.
https://link.springer.com/content/pdf/10.1007%2Fs10762-019-00622-z.pdf
Ell B., Pagonakis I.Gr., Wu C., Thumm M., Jelonnek J., "Coaxial multistage depressed collector design for highpower gyrotrons based on ExB concept," Physics of Plasmas, vol. 26, n. 11 (2019)113107.
DOI:10.1063/1.5118338.
https://aip.scitation.org/doi/10.1063/1.5118338
Afalla J., Catindig G., De Los Reyes A., Prieto E., Faustino M.A., Vistro V.D., Gonzales K.C., Bardolaza H.,
Mag-usara V.K., Husay H.A., Muldera, J., “Ultrafast carrier dynamics and THz conductivity in epitaxial grown
LT-GaAs on Silicon for development of THz photoconductive antenna detectors,” Journal of Physics D:
Applied Physics, vol. 53, n. 9 (2019) 095105. DOI: 10.1088/1361-6463/ab5aa7.
https://iopscience.iop.org/article/10.1088/1361-6463/ab5aa7
Chernov V.V., Gorbachev A.M., “Maintenance of Plasma Layer in Intersected Microwave Beams in the Rangeof Frequency from 10 to 60 GHz: Analysis and Simulation Plasma,” Chem. Plasma Process, vol. 40, n. 1 (2019)
221–233. DOI:10.1007/s11090-019-10051-4.
https://link.springer.com/article/10.1007/s11090-019-10051-4
Fukunari M., Tanaka S., Shinbayashi R., Yamaguchi Y., TatematsuY., Saito T., “Observation of a comb-shaped
filamentary plasma array under subcritical condition in 303-GHz millimetre-wave air discharge,” Sci. Rep., vol.
9 (2019) 17972. DOI:10.1038/s41598-019-54333-5.
https://www.nature.com/articles/s41598-019-54333-5
Proyavin M., Dumbrajs O., Nusinovich G., Glyavin M., “To the Theory of Gyrotrons with Wide Emitters,” J
Infrared, Millimeter, and Terahz Waves, vol. 41, n. 2 (2019) 141–151|. DOI:10.1007/s10762-019-00646-5.
https://link.springer.com/article/10.1007/s10762-019-00646-5
Bakunin V.L., Denisov G.G., Novozhilova Yu.V., “Nonlinear dynamics of multimode gyrotron under the
influence of external quasi-monochromatic signal,” Zhurnal Radioelektroniki - Journal of Radio Electronics.
2019. No. 12. DOI:10.30898/1684-1719.2019.12.1
http://jre.cplire.ru/jre/dec19/1/text.pdf

Girka I.O., Girka O.I., Thumm M., “Electromagnetic energy rotation along plasma-dielectric interface causedby azimuthal surface waves in isotropic cylindrical metallic waveguide,” Physics of Plasmas, vol. 26, n. 12(2019) 122104. DOI: 10.1063/1.5123378.
https://aip.scitation.org/doi/full/10.1063/1.5123378
Glyavin M.Y., Zaslavsky V.Y., Zotova I.V. et al. “Energy Spectra of Electron Beams and the Possibility of
Double-Stage Energy Recuperation in a Double-Beam Terahertz Gyrotron,” Radiophys Quantum Electronics,
vol. 62, n. 5 (2019) 342–347. DOI:10.1007/s11141-019-09981-y.
https://link.springer.com/article/10.1007%2Fs11141-019-09981-y
R.A. Shaposhnikov, S.V. Golubev, V.A. Skalyga, I.V. Izotov, S.V. Razin, A.V. Sidirov, R.L. Lapin, S.S. Vybin,
M.Yu. Kazakov, A.F. Bokhanov, “Point-like” neutron source based on D-D fusion reaction,” Journal of
Physics: Conference Series, vol. 1370 (2019) 012008. DOI:10.1088/1742-6596/1370/1/012008.
https://iopscience.iop.org/article/10.1088/1742-6596/1370/1/012008
SV Egorov et al, “Additive Manufacturing of Ceramic Products Based on Millimeter-Wave Heating,” IOP Conf.
Ser.:Mater. Sci. Eng., vol. 678 (2019) 012022.
https://iopscience.iop.org/article/10.1088/1757-899X/678/1/012022
Sidorov A.V., Glyavin M.Y., Golubev S.V., Razin S.V., Sintsov S.V., Veselov A.P., Vodopyanov A.V.,“Applications of the gas discharge sustained by the powerful radiation of THz gyrotrons,” Journal of Physics:
Conference Series, vol. 1400, n. 7 (2019) 077032). DOI:10.1088/1742-6596/1400/7/077032.
https://iopscience.iop.org/article/10.1088/1742-6596/1400/7/077032
Fokin A.P., Tsvetkov A.I., Manuilov V.N., Sedov A.S., Bozhkov V.G., Genneberg V.A., Movshevich B.Z.,
Glyavin M.Yu., "Control of sub-terahertz gyrotron frequency by modulation-anode voltage: Comparison oftheoretical and experimental results," Review of Scientific Instruments, vol. 90, n. 12 (2019) 124705.
DOI:10.1063/1.5132831.
https://aip.scitation.org/doi/10.1063/1.5132831
C. Tsai, T. Chang, Y. Yamaguchi, T. Idehara, "Nonadiabatic Effects on Beam-Quality Parameters forFrequency-Tunable Gyrotrons," IEEE Transactions on Electron Devices, vol. 67, n. 1 (2019) 341-346.
DOI:10.1109/TED.2019.2954362.
https://ieeexplore.ieee.org/document/8933343
Stephens J.C., Rosenzweig G., Shapiro M.A., Temkin R.J., Tucek J.C., Kreischer K.E., “Subterahertz Photonic
Crystal Klystron Amplifier,” Phys. Rev. Lett., vol. 123, n. 24 (2019) 244801. DOI:10.1103/PhysRevLett.
123.244801.
https://link.aps.org/doi/10.1103/PhysRevLett.123.244801
Bogdashov A.A., Fokin A.P., Glyavin M.Y., Novozhilova Y.V., Sedov A.S., “Experimental Study of the
Influence of Reflections from a Non-resonant Load on the Gyrotron Operation Regime,” Journal of Infrared,
Millimeter, and Terahertz Waves, vol. 41, n. 2 (2019) 164–170|. DOI: 10.1007/s10762-019-00655-4.
https://link.springer.com/article/10.1007/s10762-019-00655-4
Skalyga V.A., ABokhanov A.F., Golubev S.V., Izotov I.V., Kazakov M.Yu., Kiseleva E.M., Lapin R.L., Razin
S.V., Shaposhnikov R.A., Vybin S.S., "Status of the gasdynamic ion source for multipurpose operation(GISMO) development at IAP RAS," Review of Scientific Instruments, vol. 90, n.12 (2019) 123308.
DOI:10.1063/1.5128489.
https://aip.scitation.org/doi/abs/10.1063/1.5128489%40rsi.2020.ICIS18.issue-1
Yurovskiy L.A., Ginzburg N.S., Zotova I.V., Vilkov M.N., Samsonov S.V., Sergeev A.S. “Frequency
modulation, amplification and compression of microwave pulses in a system with helically corrugatedwaveguides as a dispersive elements,” Journal of Physics: Conference Series, vol. 1400, n. 4 (2019) 044006.
DOI: 0.1088/1742-6596/1400/4/044006.
https://iopscience.iop.org/article/10.1088/1742-6596/1400/4/044006
A. Kuleshov et al., "Low-Voltage Operation of the Double-Beam Gyrotron at 400 GHz," IEEE Transactions on
Electron Devices, vol. 67, n.2 (2019) 673-676. DOI:10.1109/TED.2019.2957873.
https://ieeexplore.ieee.org/document/8946900
S.K. Jawla, R.G. Griffin, I.A. Mastovsky, M.A. Shapiro, R.J. Temkin, "Second Harmonic 527-GHz Gyrotron
for DNP-NMR: Design and Experimental Results," IEEE Transactions on Electron Devices, vol. 67, n. 1
(2020) 328-334. DOI:10.1109/TED.2019.2953658.
https://ieeexplore.ieee.org/document/8930631
Zotova I.V., Ginzburg N.S., Malkin A.M., V.Yu Zaslavsky, I.V. Zheleznov, A.S. Sergeev, M.Yu Glyavin, S.
Mitsudo, Y. Tatemasu, T. Idehara, “Terahertz-Range High-Order Cyclotron Harmonic Planar Gyrotrons withTransverse Energy Extraction,” J Infrared Millimeter, and Terahertz Waves, vol. 41, n. 2 (2020) 152–163.
DOI:10.1007/s10762-019-00661-6.
https://link.springer.com/article/10.1007%2Fs10762-019-00661-6
Nishiura M., Tanaka K., Kubo S., Saito T., Kenmochi N., Nuga H., Seki R., Shimozuma T., Yoshimura Y.,
Igami H., Takahashi H., Tsujimura T., Yanai R., Tatematsu Y.,"Collective Thomson scattering with 77, 154,
and 300 GHz sources in LHD," Journal of Instrumentation, vol. 15 (2020) C01002-C01002. DOI:
10.1088/1748-0221/15/01/C01002.
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System and method for launching guided electromagnetic waves with impedance matching
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Charged particle beam device, multi-beam blanker for a charged particle beam device, and method for
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NEWS FROM THE NET (OUR BROADER HORIZONS)Powerful CW Sub-THz Large Orbit Gyrotron (LOG) for NMR spectroscopy
On 23 January 2020, the site Scientific Russia published an article that describes a new Large Orbit Gyrotron(LOG) developed at the Institute of Applied Physics of the Russian Academy of Sciences (IAP-RAS). This
device has demonstrated a stable generation in a CW regime at frequencies of 0.39 and 0.26 THz and output
powers of 0.4 and 0.9 kW, respectively. The well-known advantages of the LOG are high mode selectivity(since only cavity modes with an azimuthal index that is equal to the harmonic number of the cyclotron
resonance can be excited effectively) and an inherent high-harmonic operation that reduces the necessary
intensity of the magnetic field inversely proportionally to the harmonic number. In contrast to the conventional
gyrotrons that utilize magnetron injection guns (MIG) that form helical electron beams (in which the individual
electron orbits are helices following the magnetic field lines), the LOGs utilize electron-optical systems (EOS)that produce axis-encircling (aka uni-axial) electron beams. In the latter case, the electrons gyrate around theaxis of symmetry on circles with larger Larmor radius (comparable to the radius of the resonant cavity) andhence the name – Large Orbit Gyrotron. These two configurations are illustrated in Fig. 1.

Fig. 1 Resonant structure of LOG with axis-encircling electron beam (a) and a conventional gyrotron with polyaxial (helical) electron beam (b). Image courtesy Scientific Russia.
Currently, most of the DNMR-DNP spectrometers utilize radiation sources operating at frequencies of 0.263,
0.395 and 0.527 THz. Such are, for example, the devices developed by Bruker BioSpin company incollaboration with CPI (USA). Wave beams with the mentioned frequencies are delivered by gyrotrons
operating at second harmonics of the cyclotron resonance and having superconducting magnets with maximum
intensities of 5, 7, and 10 T, respectively. The concept of LOG allows to produce radiation at these threefrequencies using the same EOS and collector and changing only the cavity (and therefore the operating mode)and the output system, while the electron-optical system and the collector remain the same. The new LOG
developed at IAP-RAS is built using one 5 T cryomagnet and can operate selectively at the 2nd, 3rd and 4th
cyclotron harmonics. For the first time in the world, CW operation of LOG has been demonstrated at afrequency of 0.394 THz at the 3rd harmonic of the cyclotron frequency (Fig. 2) operating at relatively low
electron energy (30 keV) and a weak magnetic field (about 5 T).

Fig. 2 Photo of the CW LOG (left panel), oscillograms of the signals observed at the moment of the startup andduring the first one and a half minutes of operation (upper right panel), and comparison of calculated andmeasured intensities of the output beam (lower right panel). Image courtesy Scientific Russia.
For more details see the original paper: Yu.K. Kalynov, V.N. Manuilov, A.Sh. Fiks, and N. A. Zavolskiy,“Powerful continuous-wave sub-terahertz electron maser operating at the 3rd cyclotron harmonic,” Appl. Phys.
Lett., vol. 114 (2019) 213502. DOI:10.1063/1.5094875. (link)

A new approach for injecting powerful microwaves into fusion plasma
Powerful microwave radiation produced by gyrotrons is used for electron cyclotron resonance heating (ECRH)
and current drive (ECCD) of magnetically confined plasma in fusion reactors (e.g. tokamaks). For the first timein DIII-D tokamak, the researchers from the National Fusion Facility in San Diego have measured significantly
higher off-axis ECCD efficiency (more than twice higher than that obtained previously) using a novel top
launch geometry. It is expected that such a breakthrough will facilitate the development of more efficient andcompact fusion power plants.
For more detail please visit the following sources:
1. Higher Off-Axis Electron Cyclotron Current Drive Via 'Top Launch (link)
2. Taking new angle to enable more efficient, compact fusion power plants (link)
3. Top launch ECCD enabling higher off-axis current drive for steady-state operation of burning plasma
tokamaks (link)

World record acceleration: Zero to 7.8 billion electron volts in 8 inches
An article published on 21 October 2019 in PhysOrg of the American Physical Society reports that a team at
Berkeley Lab's BELLA Center doubled the previous world record for energy produced by laser plasma
accelerators, generating electron beams with energies up to 7.8 billion electron volts (GeV) in an 8-inch-longplasma (20 cm). This would require about 300 feet (91 m) using conventional technology. For more detail see
the original paper: J. Gonsalves et al, “Petawatt Laser Guiding and Electron Beam Acceleration to 8 GeV in a

Laser-Heated Capillary Discharge Waveguide,”10.1103/PhysRevLett.122.084801. (link)

Phys.

Rev.

Lett.

122,

084801(2019).

DOI:

A new way for detection of terahertz electromagnetic waves
A team of physicists at the University of California has discovered an electrical detection method for terahertz
electromagnetic waves, which could help miniaturize the detection equipment on microchips and enhancesensitivity according to a paper published in Nature (Li J., Wilson C.B., Cheng R. et al. “Spin current from subterahertz-generated antiferromagnetic magnons, Nature (2020). DOI:10.1038/s41586-020-1950-4. link). The
new method is based on a magnetic resonance phenomenon in antiferromagnetic materials that are ubiquitousand more abundant than ferromagnets. Moreover, many ferromagnets (e.g. iron and cobalt) become
antiferromagnetic when oxidized. Such materials are considered very promising for the development of various
spin-based nanoscale device applications. In their experiments, the researchers have generated a spin current inan antiferromagnet and detected it electrically by pumping up a magnetic resonance in heterostructures of auniaxial antiferromagnetic Cr2O3 crystal and a heavy metal (Pt or Ta in its β phase) using terahertz radiation
with a frequency of 0.24 THz. According to the authors, their findings reveal the unique characteristics ofmagnon excitations in antiferromagnets and their distinctive roles in spin–charge conversion in the highfrequency regime.
A popular description of this new method and its implications for the electronics is given in an article publishedin SciTech Daily and another one in Nano Werk.

Breakthrough in terahertz waves
Hamamatsu Photonics has succeeded in producing terahertz waves at a wavelength of 450 μm, which is theworld’s longest wavelength available from a single semiconductor laser operating at room temperature. To
achieve this breakthrough, the firm has developed long-wavelength mid-infrared quantum cascade laser, inwhich it designed the laser structure based on research and analysis results of the terahertz wave generation
principle. Results from this research will be useful in applications such as quality testing and non-destructive
inspection of drugs and foods containing components that absorb electromagnetic waves in the sub-terahertz
range as well as submillimeter astronomy and high-speed and high-capacity communication over shortdistances. For more detail visit the article presented at the site of Hamamatsu Photonics following the link.

Researchers generate terahertz laser with nitrous oxide (laughing gas)
An article in the MIT News reports that researchers from MIT, Harvard University, and the U.S. Army havebuilt a compact device, the size of a shoebox that produces a terahertz laser whose frequency they can tune overa wide range. The device is built from commercial, off-the-shelf parts and is designed to generate terahertz
waves by spinning up the energy of molecules in nitrous oxide, or, as it's more commonly known, laughing gas.
Nitrous oxide is used to illustrate the broad tunability over 37 lines spanning 0.251 to 0.955 terahertz, each withkilohertz linewidths. The analysis of the researchers shows that laser lines spanning more than 1 terahertz withpowers greater than 1 mW are possible from many molecular gases pumped by quantum cascade lasers. For
more information see the original paper (Paul Chevalier, et al “Widely tunable compact terahertz gas lasers,”
Science, vol. 366, Issue 6467 (2019) 856-860. DOI:10.1126/science.aay8683) published in the journal Science.