NEWSLETTERof the International Consortium“Development of High-Power Terahertz
Science & Technology”
June 2022№ 21

CONTENT Editorial(Page 1)

How to contribute to the Newsletter Invited paper M.M. Melnikova and N.M. Ryskin, “Influence of reflections on mode-competition processes in a highpower multimode gyrotron”(Page 2)
 Announcement of the International Collaborative Research Program 2022
(Page 5)
 In memoriam: Professor Toshitaka Idehara (1940-2022)(Page 6)
 List of selected recent publications and new books(Page 7)
 News from the Net(Page 13)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

INVITED PAPER
Influence of reflections on mode-competition processes in a high-power multimodegyrotron
M.M. Melnikova1,* and N.M. Ryskin1,2
1Saratov Branch, Kotelnikov Institute of Radio Engineering and Electronics RAS,
38 Zelenaya st., 410019 Saratov, Russia
2Saratov State University, 83 Astrakhanskaya st., 410012 Saratov, Russia*

Corresponding author: marymchumakova@gmail.com

Gyrotrons provide highest power in sub-THz and THz frequency bands. However, one of themost problems is ensuring of high-stable single-mode generation. Modern gyrotrons mostly operate atvery high-order transverse modes, for which the mode spectrum is very dense and self-excitation
conditions are fulfilled simultaneously for several modes with close frequencies. Thus, mode
competition processes may strongly affect the gyrotron operation.
The effect of partial reflection from a remote load on gyrotron power and oscillation frequency
has been studied in many works since 1990-ies and possibilities of control of the gyrotron radiation byreflection are now a subject of active studies. Тhe delayed reflection can increase frequency stability
and expand frequency tuning range due to excitation of high-order axial modes.
In this study, we consider interaction of several modes with neighboring azimuthal indexes, equalradial indexes, and equidistant spectrum of eigenfrequencies. We use the nonlinear time-domain theory
with fixed profile of the RF field [0]. The fixed field profile approximation is known to be valid when
the diffractive Q-factor of the cavity is much higher than its minimum value Qmin  4  L   ( L and are the cavity length and the wavelength, respectively) and the cavity filling time for eachinteracting mode Qs s ( Qs and s are Q-factor and the eigenfrequency of s-th mode, respectively)
is much longer than the electron transit time.
In modern high-power gyrotrons self-excitation conditions can be fulfilled simultaneously forseveral modes with neighboring azimuthal indexes ms , s  0, 1, 2, , and their frequency spectrum
is nearly equidistant. Hereinafter s  0 corresponds to the operating mode. Since the frequencies sand azimuthal indexes ms satisfy the resonance conditions [0]2 s   s  20  0 Q0 ,2m0  m s  m s ,,(1)a parametric coupling of the spurious sideband modes may occur and cause the instability of theoperating mode.
We use the equations of electrons’ motion with the standard initial conditions. Since we consider
the competition of modes with high azimuthal indexes, we can assume the axial structure f s    ofdifferent modes approximately the same.

Let us choose the Gaussian profile of the RF field. We study the mode competition scenarios in a
multimode gyrotron without the reflection. Consider the high-power 170-GHz fusion gyrotron with
TE28.12 operating mode developed in IAP RAS [0].
In Fig. 1 we plot the oscillation zones in the case of zero reflections. We simulate nonlinear
multimode dynamics in the cases of three and five competing modes and plot the stability domain of
the operating mode. Outside the stability domain, these perturbations start to grow, and we observe
spurious excitation of the sidebands. Note that in the domain of hard excitation, A0 should be large
enough to ensure oscillation build-up.

FIG. 1. Domain of stability of the operating mode on the  H – I 0 plane (shaded) in the case of zeroreflections. The stability boundaries calculated for three and five competing modes are shown withlight and dark circles, respectively. Start-oscillation currents for the modes with s  2 (magenta), +1(blue), 0 (green), –1 (orange), and–2 (red) are also shown. The green dashed line shows the boundaryof the hard excitation of the operating mode. The red star shows the point of maximal efficiency.
The simulations reveal different mechanisms of instability and a complicated shape of thestability domain. The point of maximal efficiency is marked by the red star in Fig. 1. It is located in thedomain of hard excitation of the operating mode and soft-excitation of the s  1 and s  2
sideband modes. The simulation shows that the five-mode oscillation regime establishes where theamplitude of the operating mode is much larger than that of the sidebands. In this regime, theefficiency is   0.55 . This regime remains stable until the hard transition to single-mode oscillationof the s  1 mode takes place. The efficiency drops to   0.3 in that case. Thus, the operating mode
oscillation regime at the point of maximal efficiency is unstable.
Let us investigate the influence of the reflected signal on the mode competition scenarios. To
suppress the spurious modes, the reflection should decrease the Q-factors of the sideband modes and,accordingly, increase their starting currents. This takes place when the phases of the reflected signals
are  1,2   2n  1  [0]. These phases are determined by the location of the reflector. Assuming thatthe frequencies of the modes are f s  f 0  sf with f  3 GHz, this condition is satisfied, forinstance, when the reflected signal passes the distance of l  0.292 m. The corresponding value of thenormalized delay time is d  0.5 .
In Fig. 2, the domain of stability of the operating mode is presented for zero reflections on theoperating mode (  0  0 ) and for strong reflections on the neighboring modes (  1  0.55 and 2  0.8 , respectively). Compared with the case of zero reflections (dotted line), it expands
significantly towards the large values of  H and encloses the point of maximal efficiency. In thedomain of high currents, the left-hand stability boundary has a complicated shape, which requires anadditional study. However, that domain is not of particular interest due to the rather low efficiency,
 ~ 0.3 .

One can see the loops appearing on the I r   H  curves, which indicate the multistability
emerging due to the “long-line” effect (see [0] for details).

FIG. 2. Domain of stability of the operating mode on the  H – I 0 plane (shaded area) in the case of in
the case of strong reflections at the parasitic modes:  1  0.55 ,  2  0.80 , d  0.5 ,  1,2   . Startoscillation currents for the modes with s  2 (magenta), +1 (blue), 0 (green), –1 (orange), and –2 (red)are also shown. The green dashed line shows the boundary of the hard excitation of the operating
mode. The red star shows the point of maximal efficiency. The domain of stability without thereflections is shown with the dotted line.
Fig. 3 displays the mode dynamics at the point of the maximum efficiency. Without thereflections, the operating mode is unstable and is suppressed by the –1-th mode during the modecompetition process. Accordingly, the efficiency drops from   0.7 to   0.3 (Fig. 3(b)). However,
the reflections stabilize the operating mode oscillation with high efficiency and all the sidebands aretotally suppressed as is shown in Fig. 3(a). In this figure, the initial values of the sideband amplitudes
are increased substantially to clearly illustrate their decay.

abFIG. 3. (a) Mode-competition scenario at the point of the maximum efficiency ( I s  0.06 ,  H  0.53 , 1  0.55 ,  2  0.8 ,  1,2   , d  0.5 ). (b) Orbital efficiency versus time with (blue) and without(red) the reflections.
The injection of the reflected signal leads to expansion of the domain of stability of the operating
mode. When the reflection of the sideband modes is strong enough, it completely suppresses the
spurious modes and provides stable single frequency oscillation with maximal efficiency.

References[1] G.S. Nusinovich, Introduction to the Physics of Gyrotrons (Johns Hopkins University Press,
Baltimore, 2004).
[2] A.G. Litvak, G.G. Denisov, V.E. Myasnikov, E.M. Tai, E.A. Azizov, V.I. Ilin, “Development in
Russia of megawatt power gyrotrons for fusion,” J. Infrared Millim. Terahertz Waves 32, 337–
342, 2011. DOI: 10.1007/s10762-010-9743-8.
[3] M.M. Melnikova, A.V. Tyshkun, and N.M. Ryskin, “Theoretical analysis of frequency
stabilization and pulling effects in a gyrotron with delayed reflection,” J. Infrared Millim.
Terahertz Waves 42, 446–461, 2021. DOI: 10.1007/s10762-021-00768-9.
For more detail, please see the original paper:
M.M. Melnikova and N.M. Ryskin, "Influence of reflections on mode-competition
processes in a high-power multimode gyrotron", Physics of Plasmas, vol. 29 (2022)
013104. https://doi.org/10.1063/5.0071210

INTERNATIONAL COLLABORATIVE RESEARCH PROGRAM 2022
Announcement of International Collaborative Research Program 2022
The Research Center for Development of Far-Infrared Region, University of Fukui (FIR UF), has started theInternational Collaborative Research Program from FY2017. This program aims to support the development of
the far-infrared region research through the international personnel exchanges and studies, being conducted at
the FIR UF in a wide array of fields, including the development of light sources, applied research, and researchand development of new technologies. FIR UF are now accepting proposals for the FY 2022 (August 2022 –March 2023).
How to apply
Please send an application form (Form 1) through the members of the FIR UF faculty after setting a research
theme and organizing a research team. The deadline for applications is June 17, 2022.
Procedures
Term: Within one year (from the date of the acceptance notice to March 31, 2023). In principle, collaborative
research shall be performed approximately for two weeks at the FIR UF.
Venue: Research Center for Development of Far-Infrared Region, University of Fukui (FIR-UF).
Financial Support: Expenses will be available until the end of January 2023.
Report: Recipients are expected to submit a one-page research report in A4 sheet on or before the set deadline(March 31, 2023).
The number of recipients is limited. Notice of the selection will be by the end of July, 2022.
Application to be sent to:International Collaboration Office, FIR UF
e-mail: int-office＠fir.u-fukui.ac.jp

The list of the previous recipients in the period 2017-2020 is available here.

Masahiko Tani
Director
FIR-UF,
University of Fukui

MEMORIAM
IN MEMORIAM
Professor Toshitaka Idehara(1940-2022)

Professor Toshitaka Idehara, the founder and first director of the FIR Research Center, Professor
emeritus at the University of Fukui, Editor-in-chief of the Journal of Infrared, Millimeter, and Terahertz Waves
passed away on 18 March 2022 at the age of 81.
Professor Toshitaka Idehara was born in Ibara Japan, on April 15, 1940. He received the B.S. degree inmathematics and the M.S. and D.S. degrees in physics from Kyoto University, Kyoto, Japan, in 1963, 1965, and1968, respectively. After graduating from Kyoto University, he joined the University of Fukui, Fukui, Japan,
and was a Lecturer from 1968 to 1970 and an Associate Professor from 1970 to 1990. During this term, heworked on fundamental plasma physics. After 1979, his interest was directed toward the development of highfrequency gyrotrons. From 1990 to 1999, he was a Professor in the Applied Physics Department, Fukui
University, and from 1992 to 1999, he was the Head of the Laboratory for Application of Superconducting
Magnet, Fukui University. Since 1999, he was a Professor and a founding Director of the Research Center for
Development of Far-Infrared Region, University of Fukui (FIR UF). Since 2007 he was also a Supervisor of theresearch at FIR UF. From June 2004 to December 2010 he was an Editor in Chief of the International Journalof Infrared and Millimeter Waves and later Journal of Infrared, Millimeter, and Terahertz Waves. In 2009, he
won the Prize for Science and Technology, The Commendation for Science and Technology by the Minister of
Education, Culture, Sports, Science and Technology of Japan, for Study on High Power THz Radiation SourcesHigh Harmonic Gyrotrons. In 2011, he was awarded the Prize for Science and Technology from Fukui
Prefectural Governor for Development of high power THz radiation sources Gyrotrons, and application to THztechnologies. In 2016 he was awarded the Kenneth J. Button Prize for outstanding contributions to thedevelopment of high power THz radiation sources (harmonic gyrotrons) and their applications to high powerTHz spectroscopy. His current research interests include development of frequency tunable, sub-THz and THz
gyrotrons and their applications to high-power THz technologies, novel spectroscopic techniques (NMR-DNP,
ESR), and advanced technologies.
Professor Idehara was an organizer and facilitator of the first International Consortium for Developmentof High-Power Terahertz Science and Technology established in 2015. He has an active international
collaboration with a great number of institutions and researchers around the world. Professor Idehara isrecognized worldwide as a brilliant scientist, devoted teacher, and leader in the field of development andapplications of gyrotrons. His remarkable achievements in advancing the operation of gyrotrons towards theTHz region is an epochal contribution, which is an inspiration for the new generation of younger researchers aswell as for all his colleagues and collaborators.
We pray that the soul of our beloved teacher, colleague, and friend Professor Idehara may rest inpeace.
We will always keep nice memory of him as a great scientist and a man of vision who bequeath us
to continuing his great mission.

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 February 2022, i.e. after issuing the previous Newsletter#20. 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., “Terahertz gas discharge: current progress and possible applications,” Journal of Physics D:
Applied Physics, (2022). DOI:10.1088/1361-6463/ac5556.
https://iopscience.iop.org/article/10.1088/1361-6463/ac5556/meta
T. Rzesnicki et al., "Experimental Testing of the European TH1509U 170-GHz 1-MW CW Industrial Gyrotron– Long Pulse Operation," in IEEE Electron Device Letters, (2022). DOI:10.1109/LED.2022.3152184.
https://ieeexplore.ieee.org/document/9718585
Adilova, Asel B., and Nikita M. Ryskin, "Theory of Peer-to-Peer Locking of High-Power Gyrotron Oscillators
Coupled with Delay," Electronics, vol. 11, n. 5 (2022) 811. DOI:10.3390/electronics11050811.
https://www.mdpi.com/2079-9292/11/5/811
Golubev, S.V., Skalyga, V.A., Izotov, I.V. et al. ECR Discharge Sustained by Millimeter Waves as a Source ofDense Plasma Flux. Plasma Phys. Rep., vol. 48 (2022) 200–204. DOI:10.1134/S1063780X22020088.
https://link.springer.com/article/10.1134/S1063780X22020088
Sabchevski S.P., Glyavin M.Y., Nusinovich G.S., “The Progress in the Studies of Mode Interaction in
Gyrotrons,” J Infrared, Millimeter, and Terahertz Waves, (2022). DOI:10.1007/s10762-022-00845-7.
https://link.springer.com/article/10.1007/s10762-022-00845-7
Y. M. Guznov, A. N. Leontyev, R. M. Rozental, A. S. Sergeev, I. V. Zotova and N. S. Ginzburg, "Tunable
Multi-Frequency Radiation Source based on Gyrotron with Pre-Modulated Beam," in IEEE Electron Device
Letters, (2022). DOI:10.1109/LED.2022.3163153.

https://ieeexplore.ieee.org/abstract/document/9744112
T. Barmashova et al., "Study of THz gas discharge spatial dynamic in Argon," in IEEE Transactions on
Terahertz Science and Technology, (2022). DOI:10.1109/TTHZ.2022.3164546.
https://ieeexplore.ieee.org/document/9748981
O. Louksha, Trofimov P., Manuilov V., Glyavin M., “Trajectory Analysis in a Collector with Multistage
Energy Recovery for a DEMO Prototype Gyrotron. Part II. Toroidal Magnetic Field,” Technical Physics (2022).
DOI:10.1134/S1063784221070082.
https://link.springer.com/article/10.1134/S1063784221070082
Ananichev A.A., Sedov A.S., Tsvetkov A.I. et al., “The Use of Simultaneous Tuning of Several Control
Parameters to Stabilize the Radiation Power of a Subterahertz Gyrotron when Tuning the Generation
Frequency,” Instrum Exp Tech, vol. 65 (2022) 262–266 (2022). DOI:10.1134/S0020441222020099.
https://link.springer.com/article/10.1134/S0020441222020099
V.I. Shcherbinin, K.A. Avramidis, M. Thumm and J. Jelonnek, "Design of a High-Q Diamond-Loaded Cavity
for a Third-Harmonic Subterahertz Gyrotron Driven by a Low-Power Electron Beam," in IEEE Transactions on
Electron Devices, (2022). DOI:10.1109/TED.2022.3166125.
https://ieeexplore.ieee.org/abstract/document/9760289
Nishiura Masaki, Adachi Shunm, Tanaka Kenji, Kubo Shin, Kenmochi Naoki, Shimozuma Takashi, Yanai
Ryoma, Saito Teruo, Nuga Hideo, Seki Ryosuke, “Collective Thomson scattering diagnostic with in situ
calibration system for velocity space analysis in large helical device,” Review of Scientific Instruments, vol. 93(2022) 053501. DOI:10.1063/5.0079296.
https://aip.scitation.org/doi/10.1063/5.0079296
A.S. Sergeev, L.A. Yurovskiy, N.S. Ginzburg, I.V. Zotova, I.V. Zheleznov, R.M. Rozental, A.A. Rostuntsova,
and N. M. Ryskin, “Entrainment, stopping, and transmission of microwave solitons of self-induced
transparency in counter-propagating magnetized electron beam,” Chaos vol. 32 (2022) 053123.
DOI:10.1063/5.0087408.
https://aip.scitation.org/doi/10.1063/5.0087408
Tsvetkov, A., Vodopyanov, A., Mansfeld, D., Orlovskiy, et al. “Production of highly dispersed powders ofmetal-oxides by evaporation-condensation technique when heated by focused radiation of terahertz-range
gyrotron setup,” Journal of Physics: Conference Series, vol. 2256, n. 1 (2022) 012030. DOI: 10.1088/17426596/2256/1/012030.
https://iopscience.iop.org/article/10.1088/1742-6596/2256/1/012030/meta
Tsvetkov A., Vodopyanov A., Mansfeld D., Orlovskiy A., Kamenskiy M., Samokhin A., Alexeev N., Sinayskiy
M., Sedov A., “Production of highly dispersed powders of metal-oxides by evaporation-condensation techniquewhen heated by focused radiation of terahertz-range gyrotron setup. InJournal of Physics: Conference Series
vol. 2256, n. 1, (2022) 012030. DOI:10.1088/1742-6596/2256/1/012030.
https://iopscience.iop.org/article/10.1088/1742-6596/2256/1/012030/meta
Girka, I., Thumm, M., “Excitation of Surface Flute Waves in Electron Cyclotron Frequency Range byRelativistic Electron Beam Gyrating Along Large Larmor Orbits. In: Surface Flute Waves in Plasmas,”
Springer Series on Atomic, Optical, and Plasma Physics, vol 120. Springer, Cham. DOI:10.1007/978-3-03098210-2_7.
https://link.springer.com/chapter/10.1007/978-3-030-98210-2_7
V.S. Vysotsky, V. Zubko, S. Fetisov, M. Glyavin and M. Proyavin, "Possible designs of mobile cryomagnets
for novel microwave technologies," in IEEE Transactions on Applied Superconductivity, (2022). DOI:
10.1109/TASC.2022.3174182.
https://ieeexplore.ieee.org/abstract/document/9772319

E.M. Khutoryan, A.N. Kuleshov, S.S. Ponomarenko, K.A. Lukin, Y. Tatematsu and M. Tani, "Hybrid BulkSurface Modes Excited by a Sheet Electron Beam in THz Cherenkov Oscillator," in IEEE Transactions on
Electron Devices, vol. 69, n. 6 (2022) 3407-3412. DOI:10.1109/TED.2022.3168526.
https://ieeexplore.ieee.org/document/9765648
Picard J., Mastovsky I., Shapiro M., Temkin R.J., et all. “Generation of 565 MW of $X$-band power using ametamaterial power extractor for structure-based wakefield acceleration,” Phys. Rev. Accel. Beams, vol. 25. N.
5 (2022) 051301. DOI:10.1103/PhysRevAccelBeams.25.051301.
https://link.aps.org/doi/10.1103/PhysRevAccelBeams.25.051301
M. Hosseini, A. Kaasinen, G. Link, M.A. Shoorehdeli, T. Lahivaara, M. Vauhkonen, “Tomography-assisted
control for the microwave drying process of polymer foams,” Journal of Process Control, vol. 114 (2022).
DOI:10.1016/j.jprocont.2022.03.011.
https://www.sciencedirect.com/science/article/pii/S095915242200049X
Ruess T., Gantenbein G., Jin J., Marek A., et al. “Verification of the 170/204 GHz Quasi-Optical Output
Coupler of the 2 MW Coaxial-Cavity Gyrotron using a Mode Generator Setup,” Vortrag gehalten auf 14th
German Microwave Conference (GeMiC 2022), Ulm, Deutschland, 16.–18. Mai 2022.
https://publikationen.bibliothek.kit.edu/1000146721
Kamenskiy, M.V., Koshelev, M.A., Orlovsky, A.A. et al. “Development and Testing of a Device for Regulationand Stabilization of Powerful Millimeter Radiation,” Instrum Exp Tech, vol. 65 (2022) 393–397.
DOI:10.1134/S0020441222030083.
https://link.springer.com/article/10.1134/S0020441222030083
Balega Y, Bubnov G, Glyavin M, Gunbina A, Danilevsky D, Denisov G, Khudchenko A, Lesnov I, Marukhno
A, Mineev K, Samsonov S, Shanin G, Vdovin V., “Atmospheric Propagation Studies and Development of New
Instrumentation for Astronomy, Radar, and Telecommunication Applications in the Subterahertz Frequency
Range,” Applied Sciences, vol. 12, n.11 (2022). DOI:10.3390/app12115670.
https://www.mdpi.com/2076-3417/12/11/5670
Sabchevski S., Di Palma E., Spassovsky I., Dattoli G., “Gyrotrons as High-Frequency Drivers for Undulatorsand High-Gradient Accelerators,” Appl. Sci., vol. 12 (2022) 6101. DOI:10.3390/app12126101.
https://www.mdpi.com/2076-3417/12/12/6101
B. Publications by other authors worldwide
Y. Song, H. Zheng, M. Liu, H. Xiao, X. Han and L. Li, "Globally Optimal Algorithm of Superconducting
Magnet Design for Gyrotrons," in IEEE Transactions on Applied Superconductivity, (2022). DOI:
10.1109/TASC.2022.3152103.
https://ieeexplore.ieee.org/abstract/document/9714801
Gelfusa, Michela, et al. "Proposal of a Testing Procedure to Qualify Iter Window Assemblies Exposed to HighMicrowave Stray Radiation." Electronic copy available at: https://ssrn.com/abstract=4043601.
https://papers.ssrn.com/sol3/papers.cfm?abstract_id=4043601
Y. Song, H. Zheng, M. Liu, H. Xiao, X. Han and L. Li, "Globally Optimal Algorithm of Superconducting
Magnet Design for Gyrotrons," in IEEE Transactions on Applied Superconductivity, (2022).
DOI:10.1109/TASC.2022.3152103.
https://ieeexplore.ieee.org/abstract/document/9714801

Voronova, E.V., Knyazev, A.V., Letunov, A.A. et al. “Temperature of the Surface of Powders in Experimentswith Chain Plasma-Chemical Reactions Initiated by the Radiation of a Gyrotron in Pd + Al2O3 Mixtures,”Phys. Atom. Nuclei, Vol. 84 (2021) 1761–1764. DOI:10.1134/S1063778821090374.
https://link.springer.com/article/10.1134/S1063778821090374
M. K. Alaria, N. Singh and A. Bera, "RF characterization of Cavity and Window for Gyro-devices," 2021 IEEE
MTT-S
International
Microwave
andRF
Conference(IMARC),
2021,
pp.
1-3.
DOI:10.1109/IMaRC49196.2021.9714614.
https://ieeexplore.ieee.org/abstract/document/9714614
Z. -C. Gao et al., "Design of a 330-GHz Frequency-Tunable Gyrotron With a Prebunched Circuit," in IEEE
Transactions on Electron Devices, (2022). DOI: 10.1109/TED.2022.3152461.
https://ieeexplore.ieee.org/abstract/document/9728759
I. Chelis, D. Peponis, and A. Zelkas, "Self-consistent modeling of the electron–cyclotron maser interaction inlossy structures based on a full-wave Green's function approach," Physics of Plasmas, vol. 29 (2022) 033103.
DOI:10.1063/5.0079969.
https://aip.scitation.org/doi/full/10.1063/5.0079969
M. Jin, X. Li, D. Xia, Y. Zhang, Y. Zhu and M. Bai, "Compact Dual-Mirror Design of Quasi-Optical Mode
Converter with First Mirror Optimization," in IEEE Antennas and Wireless Propagation Letters, (2022).
DOI:10.1109/LAWP.2022.3155789.
https://ieeexplore.ieee.org/abstract/document/9726870
I. Pimenov, et al. "HF-launcher system of the gyrotron set-up of the T-15MD tokamak on the first stage
operation." Applied Physics (2022). DOI: 10.51368/1996-0948-2022-1-5-11.
https://sciprofiles.com/publication/view/df03f649dbf8047d86f749e3233faef1
Benedikt Hermann, Urs Haeusler, Gyanendra Yadav, Adrian Kirchner, Thomas Feurer, Carsten Welsch, Peter
Hommelhoff, Rasmus Ischebeck, “Inverse-Designed Narrowband THz Radiator for Ultrarelativistic
Electrons,”ACS Photonics, (2022). DOI: 10.1021/acsphotonics.1c01932.
https://pubs.acs.org/doi/10.1021/acsphotonics.1c01932
Ali A., Mitra A., Aïssa B., “Metamaterials and Metasurfaces: A Review from the Perspectives of Materials,
Mechanisms and Advanced Metadevices,” Nanomaterials, vol. 12 (2022) 1027. DOI:10.3390/nano12061027.
https://www.mdpi.com/2079-4991/12/6/1027
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Review," in IEEE Sensors Journal, (2022). DOI:10.1109/JSEN.2022.3161013.
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NEW BOOKSMikhail Glyavin (Ed.) “Design, Technologies and Applications of High Power Vacuum Electronic Devices
from Microwave to THz Band,” (MPDI Books, 2021). ISBN 978-3-0365-2242-5 (Hbk); ISBN 978-3-03652241-8 (PDF). DOI:10.3390/books978-3-0365-2241-8. (Open Access)https://www.mdpi.com/books/pdfview/book/4790

NEWS FROM THE NET (OUR BROADER HORIZONS)
Researchers have discovered a new effect in two-dimensional conductive systems thatpromises improved performance of terahertz detectors
A post published in in PHYSORG on 23 May 2022 reports that researchers at the Cavendish Laboratory,
together with colleagues at the Universities of Augsburg (Germany) and Lancaster have found that a new typeof THz detector that they were developing is demonstrating better performance since it provides stronger signal
than should be theoretically expected. This motivated them to seek for a new explanation. Furthermore, theyfound a new physical effect when two-dimensional electron systems are exposed to terahertz waves. The
quantitative theory of the effect was developed by a researcher from the University of Augsburg, Germany, andthe international team of researchers published their findings in the journal Science Advances.
For more detail, please seem the original publication:

“An in-plane photoelectric effect in two-dimensional electron systems for terahertz detection” by Wladislaw
Michailow, Peter Spencer, Nikita W. Almond, Stephen J. Kindness, Robert Wallis, Thomas A. Mitchell,
Riccardo Degl’Innocenti, Sergey A. Mikhailov, Harvey E. Beere and David A. Ritchie, 15 April 2022, Science
Advances. DOI: 10.1126/sciadv.abi8398.

Kyoto Fusioneering closed 150M JPY loan granted by Japan Finance Corporation
According to the news, released by Kyoto Fusioneering Ltd (KF) on 12 April 2022, (KF), this fusion
technology company, based in Japan, closed a long-term loan agreement with the Japan Finance Corporation
for a total of JPY 150 million, for a period of 10 years aiming to develop further advanced technologies forfusion reactors. Kyoto Fusioneering, a spin-off of Kyoto University, is pioneering in advancement ofgyrotron systems, tritium fuel cycle technologies, and breeding blankets for tritium production andpower generation.
The fund supports KF´s work towards establishing a supply chain of key technologies for the deployment offusion energy. In addition, it enables the company to accelerate its recruitment effort and its go-to-market team.
In 2021, Kyoto Fusioneering was awarded a contract by the UK Atomic Energy Authority to provide dual
frequency microwave heating sources (gyrotrons) for MAST Upgrade (Mega Amp Spherical Tokamak),based at Culham, near Oxford, UK. Use of these gyrotrons on MAST Upgrade is also relevant to UKAEA’s
STEP (Spherical Tokamak for Energy Production) initiative – the UK’s flagship programme to design andbuild a prototype fusion power plant. Furthermore, the company is working with several private developers, inthe U.S. and Europe, to solve reactor engineering challenges for more novel routes to fusion energy.
This support reflects progress during the years and a recognition of the role of Kyoto Fusioneering in driving a
new energy industry and building a neutral carbon society.
For more detail about KF Ltd please visit their site and follow them on Twitter. The Newsletter of KF isavailable at the following link.

ITER maintains neutrality and continues the continuation of the planned tasks
Russia takes part in the development and production of 25 diagnostic, vacuum, electromagnetic and othersystems. Some of them are indispensable for launching the reactor. “Russia will continue to fulfill all of its
obligations. We have already shipped some of the critical systems and components. Other essential shipments
are scheduled for later this year, and we keep working on the systems we have undertaken to produce,” said
Alexander Petrov, the press secretary of ITER Center (Russian office of the ITER project). ITER firmly
maintains political neutrality and, despite political and economic headwinds, does not refuse to cooperate with
Russia. “There are no marked changes in the team’s attitude. ITER has long been positioning itself as afundamentally neutral project. In early March, we received a confirmation of this principle and assurances thatany signs of disrespect in the team, particularly those related to the crisis, would be addressed immediately. The
objectives of ITER cannot be achieved without Russia’s contribution, and everyone understands it. According
to the information I have, Director-General of the ITER Organization Bernard Bigot has repeatedly assured that
he will do his best to tackle any problems with contracts, customs clearance, bank payments, etc.,” Vitaly
Krasilnikov, a supervisor of Neutron Diagnostics at the ITER Organization (France), shares his opinion.
By the end of 2022 Q2, Russia will ship a poloidal field coil PF1 to France, where ITER is constructed. It will
be placed outside the ITER toroidal magnet system and generate a poloidal magnetic field to produce plasma,
control its position and shape and maintain electric current in it. There will be six poloidal field coils. One ofthem will be supplied by China; another four are made right on the site – so big they are – the Russianproduced coil is 9 meters in diameter and weighs 200 tons.
Each of 16 coil cables is made of niobium-titanium (NbTi) superconductors manufactured at the production
facilities of Rosatom’s fuel division and the Russian Research Institute for the Cable Industry. Theirsuperconducting properties manifest themselves at the temperature of about 4ºК. The work on the coil started in
2014. Technology and equipment were developed at Rosatom, while manufacturing takes place at SredneNevsky Shipbuilding Plant in Saint Petersburg.
In September, ITER expects to receive gyrotrons – vacuum devices generating high-power, high-frequency
radiation that overheat electrons in plasma – made in Russia. More important is that they cause breakdown andplasma initiation. Output power of each gyrotron is 1 MW and radiation frequency is 170 GHz. ITER needs 24
gyrotrons in total, and Russia will supply eight of them. Six devices are ready; five of them have already passed
acceptance tests.
The gyrotrons will be placed in a detached building since they are susceptible to external electromagnetic fields
that are present in abundance in the tokamak, ITER’s core functional component. The engineering process issupervised by the Institute of Applied Physics of the Russian Academy of Sciences; manufacturing takes place
at Gycom in Nizhny Novgorod.
Shipment of pedestals for blanket module connectors is scheduled for November–December 2022. The
pedestals will be mounted by welding on the reactor’s vacuum chamber. They are designed to hold electricalconnectors that complete a path for currents induced in the blanket modules at the time of plasma disruption.
The connectors were manufactured at the Research and Development Institute of Power Engineering (NIKIET,
part of Rosatom). The manufacturing process took about three years and a half. The pedestals are made of twomaterials, a chromium zirconium copper alloy and stainless steel.
By the end of 2022, Russian companies will produce port plugs and test stands for them. Port plugs are modules
that enable the installation of plasma diagnostic systems inside the reactor. They protect the systems against
neutron flux and mitigate the effects of ionizing radiation in the areas accessible by personnel. There will be a
total of 40 port plugs installed along the perimeter of the tokamak vacuum chamber, and four of them will bemade in Russia. It will also supply four stands for pre-operational vacuum, thermal and functional testing of theport plugs. The test stands will be pre-assembled at the factory and then assembled on the site in a Lego-likemanner. Each port plug will be tested for about five months, this is why several stands are needed. If there werea single test stand, it would take more than 16 years to test all the devices. The first shipment of the stands isscheduled for next year. The last stand will be delivered in 2026. The port plugs will be manufactured at theInstitute of Nuclear Physics of the Russian Academy of Sciences Siberian Branch, and test stands at GKMP
Research and Production Company in Bryansk.
The above information has been abridged from the following post. Please access the original for more detail.

Fusion reactors could generate more power thanks to a reworking of Greenwald's Law.
In a report by Tom Metcalfe, published at Space.com, it has been announced that physicists just rewrote afoundational rule for nuclear fusion reactors that could unleash twice the power. As a result, the future fusion
reactions inside tokamaks could produce much more energy than previously thought, thanks to groundbreaking
new research that found a foundational law for such reactors was wrong. The nuclear fusion research, led byphysicists from the Swiss Plasma Center at École Polytechnique Fédérale de Lausanne (EFPL), has determinedthat the maximum hydrogen fuel density is about twice the "Greenwald Limit" — an estimate derived fromexperiments more than 30 years ago. The discovery that fusion reactors can actually work with hydrogenplasma densities that are much higher than the Greenwald Limit they are built for will influence the operationof the massive ITER tokamak being built in southern France, and greatly affect the designs of ITER's
successors, called the Demonstration power plant (DEMO) fusion reactors, said physicist Paolo Ricci at the
Swiss Plasma Center. "The exact value depends on the power," Ricci told Live Science. "But as a roughestimate, the increase is on the order of a factor of two in ITER."
The original research paper by Giacomin et al. demonstrates that a first-principles scaling law, based on
turbulent transport considerations, and a multimachine database of density limit discharges from the ASDEX
Upgrade, JET, and TCV tokamaks, show that the increase of the boundary turbulent transport with the plasma

collisionality sets the maximum density achievable in tokamaks. This scaling law shows a strong dependence
on the heating power, therefore predicting for ITER a significantly larger safety margin than the Greenwald
empirical scaling [Greenwald et al., Nucl. Fusion, 28, 2199 (1988)] in case of unintentional high-to-low
confinement transition.
Journal reference:
M. Giacomin et al. First-Principles Density Limit Scaling in Tokamaks Based on Edge Turbulent Transport andImplications for ITER. Physical Review Letters 128, 185003. DOI:10.1103/PhysRevLett.128.185003.