NEWSLETTERof the International Consortium“Development of High-Power Terahertz
Science & Technology”
October 2019

№ 13

CONTENT Editorial(Page 1)
How to contribute to the Newsletter Invited papers(Pages 2,6)
• V.V. Rumyantsev, K.V. Maremyanin, A.P. Fokin, A.A. Dubinov, V.V. Utochkin, M.Yu. Glyavin, M. Tani,
T. Furuya, J. Afalla, N.N. Mikhailov, S.A. Dvoretskii, V.I. Gavrilenko and S.V. Morozov, “SecondHarmonic Generation of Sub-Terahertz Gyrotron Rdiation by Frequency Doubling in InP:Fe and its
Application for Magnetospectroscopy of Semiconductor Structures.”• I.V. Bandurkin, M.Yu. Glyavin, S.V. Kuzikov, P.B. Makhalov, I.V. Osharin, and A.V. Savilov, “Methodsof Enhancing the Gyrotron Operation Selectivity and Efficiency Using Special Corrugations of the Cavity
Wall.” News from the members of the International Consortium(Page 12)
 Upcoming events (conferences and workshops)(Page 15)
 List of selected recent publications, patents, and new books(Page 21)
 News from the Net (our broader horizons)(Page 27)

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 PAPERS
Second-Harmonic Generation of Sub-Terahertz Gyrotron Radiation by Frequency
Doubling in InP:Fe and its Application for Magnetospectroscopyof Semiconductor Structures
V.V. Rumyantsev1, K.V. Maremyanin1, A.P. Fokin2, A.A. Dubinov1, V.V. Utochkin1, M.Yu. Glyavin2,
M.Tani3, T. Furuya3, J. Afalla3, N.N. Mikhailov4, S.A. Dvoretskii4, V.I. Gavrilenko1, and S.V. Morozov1,3,*
1Institute for Physics of Microstructures of Russian Academy of Sciences, N. Novgorod, Russia
2

Institute of Applied Physics of the Russian Academy of Sciences, N. Novgorod, Russia

3

University of Fukui, Research Center for Development of Far-Infrared Region, Fukui, Japan

4

Institute for Semiconductor Physics, Siberian Branch, Russian Academy of Sciences, Novosibirsk, Russia*Corresponding author: more@ipm.sci-nnov.ru

In recent decades, an unprecedented increase in activity in the terahertz (THz) range of the electromagnetic
spectrum has been observed around the world. The giant spread of studies into the possibility of using THz
radiation in a variety of very important applications suggests that today this range proves to be at the forefront ofinvestigations and developments.
The difficulty in creating efficient terahertz sources is related to the fact that, in the terahertz range, welldeveloped methods for generating optical and microwave radiation are poorly applicable. Powerful sources ofterahertz radiation are synchrotrons and free-electron lasers; however, a high cost and large sizes prevent theirwide use even for purely scientific applications. The classical devices of vacuum electronics barely achieve thefrequency limit of 1 THz, and their radiation power in this range does not exceed 1 mW. The difficulties inincreasing the operating frequency of such vacuum sources are associated with those in manufacturing a smallscale deceleration system. In gyro-devices, the radiation frequency is limited by the magnetic field strength andby the necessity of selection when working at gyrofrequency harmonics, which usually requires complex
technical solutions. On the other hand, since the equivalent temperature of 1 THz radiation is only 47.6 K, thethermal relaxation of levels at room temperature leads to the rapid destruction of inversion in lasers. Thus,
quantum-cascade lasers, which occupy the leading positions among compact semiconductor sources in the midinfrared range, operate at terahertz frequencies only under conditions of cryogenic cooling.
The main methods for generating terahertz radiation in semiconductor structures are reduced to the opticalrectification of short-wavelength radiation pulses, the generation of a difference frequency when using parametriclight generators as a pump, and also the initiation of fast transient processes upon the excitation of asemiconductor in lasers with a short optical pulse. Sources of terahertz radiation based on femtosecond lasers
have an extremely wide emission spectrum (~1 THz), which is not always acceptable. In addition, the output

power in all the above methods is low. At the moment, for the generation of terahertz radiation by the opticalrectification method, as a rule, ZnTe, GaP, and LiNbO3 crystals are used. For all of them, fairly large losses inthe terahertz range are characteristic.
One of the ways of obtaining intense terahertz radiation is by multiplying the radiation frequency due to various
types of nonlinearity in semiconductor structures. As is known, generation of the second harmonic due to secondorder lattice nonlinearity is possible only in crystals in which there is no center of inversion. The latticenonlinearity was studied in gallium arsenide: a CH3F gas laser with frequencies in the range of 0.6–1.7 THz anda free-electron laser were used as the radiation source. It should be noted that the nonlinear properties of III–V
materials are studied very poorly in the far-IR region, where the frequency dispersion of the nonlinear secondorder coefficient is significant. According to our information, there is only one theoretical study devoted to these
problems, and there are several experimental studies.
The development of gyrotrons with an operating frequency in the terahertz range is carried out in almost all
research centers around the world specializing in vacuum electronics. At present, subterahertz gyrotrons operatingwith sufficiently high power in both the pulsed and continuous-wave modes have already appeared. The doublingof the radiation frequency of such lamps makes it possible to obtain narrow-band (several MHz) radiation in therange of 0.5–1.1 THz with the ability to tune the radiation frequency within 1 GHz and, in the future, achieving
a frequency of 2– 2.5 THz. In this case, a high pump-radiation power makes it possible to rely on obtaining ahigh radiation power at the second harmonic even at room temperature.
In this study, we investigated the possibility of doubling the radiation frequency of a gyrotron operating at thefundamental cyclotron harmonic with the generation of a frequency of 0.263 THz. As already mentioned, thegeneration of the second harmonic due to the second-order lattice nonlinearity is possible only in crystals in which
there is no center of inversion. Despite relatively high values of the second-order nonlinear susceptibility, theacquisition of a low residual concentration of free carriers is a difficult technological problem for many common
semiconductors. Among the materials for which this problem was successfully solved, indium phosphide should
be noted, in which, in addition, the magnitude of the nonlinear susceptibility is more than six times higher than
the second-order nonlinear susceptibility in the GaAs semiconductor, which is the best studied in this respect.
One of the factors complicating the experimental study of gyrotron-frequency doubling in semiconductor
structures is the presence of harmonic components of the cyclotron frequency in the emission spectrum of
gyrotrons due to the nonlinearity of the electron beam in the strong signal mode. To compare the evaluation of
the frequency-doubling efficiency with the intensity of gyrotron self-radiation at the second harmonic, thegyrotron emission spectrum was experimentally investigated using notch filters based on the cyclotron resonancein semiconductor structures. For this purpose, ~10% of the gyrotron radiation was diverted to the measuring pathconsisting of an oversized waveguide coupled with a Michelson or Mach– Zehnder interferometer, at the output
of which a supercritical waveguide was mounted, which cut off the fundamental harmonic at 263 GHz andtransmitted the radiation at a doubled frequency of 526 GHz.

Further, the radiation was introduced through a waveguide insert into an STG-40 Dewar transport vessel, in
the lower part of which a superconducting magnet was located, which enables us to obtain a magnetic field of up
to 3 T when cooling with liquid helium. As a notch filter, a structure with a HgTe/Cd0.65Hg0.35Te quantum well
20 nm wide grown by molecular-beam epitaxy on a GaAs substrate and doped with indium to concentrations of~1017 cm–3 in barriers was located inside the magnet. Due to the small effective masses of electrons in such
structures, the cyclotron resonance at a frequency of 0.263 THz is observed in relatively low magnetic fields of~0.3 T. When a field corresponding to cyclotron resonance was achieved, the transmission of the structure sharply
decreased, which led to a drop in the signal at the InSb-based photoelectric receiver located at the end of the
waveguide insert behind the magnet. Thus, the described measuring setup made it possible to perform express
analysis of the spectral composition of the radiation. The magnitude of signal suppression at the fundamental
harmonic in the supercritical waveguide and the modulation depth in the used interferometers were measured
individually in the range of linearity of the InSb-receiver response, and the possibility of continuously varying
the gyrotron radiation power from 1 W to 1 kW was applied. The combination of the interferometer and thesupercritical waveguide enabled us to attenuate the intensity of the first harmonic by about three orders ofmagnitude.
Dependingmagnitude

at

the

on

the

receiver-signal

path

difference

in

the

spectrometer arms, we found weak peaks locatedbetween the principal ones in addition to themcorresponding to radiation at the fundamental
harmonic. The nature of the observed interference
pattern is shown schematically in the inset to Fig.
1, which also shows the magnetic-transmission
spectra obtained with a gyrotron radiation powerof 80 W. It can be seen that, in the position of theinterferometer corresponding to the transmission
Fig. 1. Spectra of magnetic transmission of a sample
based on HgCdTe at different values of the path
difference (marked by an arrow on the interference
patterns - see insets below) in a Michelsoninterferometer used as a second harmonic filter.

minimum, the magnetic-transmission spectrum
contains a single line of cyclotron resonancecorresponding to a gyrotron emission frequency of
0.263 THz.

When the interferometer is in the position corresponding to an “additional” peak, a second line appears in themagneto- transmission spectrum, the peak of which corresponds to a magnetic field twice as high, i.e., to thesecond harmonic. Measurements at other gyrotron powers showed that the average ratio of the intensity of thesecond harmonic to the first one lies in the range of 0.001–0.005.

Depending on the receiver-signal magnitude at the path difference in the spectrometer arms, we found weak
peaks located between the principal ones in addition to them corresponding to radiation at the fundamental
harmonic. The nature of the observed interference pattern is shown schematically in the inset to Fig. 1, which
also shows the magnetic-transmission spectra obtained with a gyrotron radiation power of 80 W. It can be seen
that, in the position of the interferometer corresponding to the transmission minimum, the magnetic-transmission
spectrum contains a single line of cyclotron resonance corresponding to a gyrotron emission frequency of 0.263
THz. When the interferometer is in the position corresponding to an “additional” peak, a second line appears in
the magneto- transmission spectrum, the peak of which corresponds to a magnetic field twice as high, i.e., to thesecond harmonic. Measurements at other gyrotron powers showed that the average ratio of the intensity of thesecond harmonic to the first one lies in the range of 0.001–0.005.
It is easy to estimate that, for a radiation intensity of 8 kW/cm2 at the principal harmonic discussed above,
doubling at a crystal with a length of ~7 cm gives a comparable intensity of radiation at the second harmonic.
However, in the case of pulsed gyrotrons, higher radiation intensities are available, which can significantly
increase the conversion efficiency. It should be noted that an increase in the efficiency with frequency iscompensated by the increasing dispersion of refraction and absorption in InP:Fe; however, we can expect toobtain a radiation intensity an order of magnitude larger at the doubled frequency than the intrinsic radiation of
the gyrotron at the second harmonic.
To cut off radiation at the fundamental harmonic of 263 GHz and transmit radiation at a double frequency of
526 GHz, as well as focus the radiation into a spot with a diameter of 2.5 mm, to provide a power density of about
15 kW/cm2 at 263 GHz, a shielded case was specially designed. The shielded box is equipped with water coolingover the entire surface. A photograph demonstrating the general view of the box is shown in Fig.2.
We conclude that employing high-resistivity
InP:Fe crystals is a promising route to obtain THz
radiation by doubling the frequency of intense
gyrotron radiation. For realistic gyrotrons, at least
1% conversion efficiency is achievable in InP
wafers, corresponding to the second harmonic
power of 60100 W/cm2 in 0.51.2 THz frequency
range. According to studies of the gyrotron
radiation, this is an order of magnitude higher than
the intensity of the second harmonic available from
Fig. 2. Shielded box design for focusing the radiationon the fundamental frequency (gyrotron part on theleft side).

the gyrotron. The possibility of using secondharmonic radiation for the magnetospectroscopy ofsemiconductor structures is shown.

For more detail: V.V. Rumyantsev, at al. Semiconductors 53, 1217–1221 (2019).

Methods of Enhancing the Gyrotron Operation Selectivity and Efficiency
Using Special Corrugations of the Cavity Wall
I.V. Bandurkin1,2,*, M.Yu. Glyavin1, S.V. Kuzikov1, P.B. Makhalov1, I.V. Osharin1, and A.V. Savilov1
1

Institute of Applied Physics of the Russian Academy of Sciences (IAP RAS),
Nizhny Novgorod, 603950, Russia
2
University of Fukui, Research Center for Development of Far-Infrared Region, Fukui, Japan*Corresponding author: iluy@appl.sci-nnov.ru
Recently, two novel methods of improving the gyrotron operation have been proposed [1-3]. Both of them arebased on a certain deformation of the gyrotron cavity walls and have been confirmed by comprehensive numericalsimulations. Here we briefly summarize the essence of these methods and corresponding numerical results.
Decreasing the Ohmic losses in long cavities
The first method may be useful when one has to use a very long cavity to provide the gyrotron excitation. This
is often the case for weakly-relativistic tubes operating at high cyclotron harmonics, where the long cavity isnecessary to compensate for the weak electron-wave coupling. In conventional cylindrical cavity, and especiallyin the THz frequency range, this leads to a very high ratio of the diffraction and Ohmic quality factors, so thatthe share of Ohmic losses may exceed 90%. To decrease the diffraction Q-factor, the operation at higher axial
modes can be used, since the efficiency of the radiated power extraction increases with the operating wave groupvelocity. Unfortunately, the efficiency of the radiation itself rapidly decreases for higher axial modes mainly due
to increasing sensitivity of the operation to the velocity spread in the electron beam. In its turn, such sensitivity
is a consequence of the cyclotron resonance condition, which includes depending on the electron velocity Dopplerterm:𝜔 ≈ 𝑛Ω𝑐 ± (𝑙𝜋/𝐿)𝑣∥ ,(1)

where 𝜔 and Ω𝑐 are the operating and electron cyclotron frequencies, 𝑛 is the cyclotron harmonic number, 𝐿 isthe cavity length, 𝑙 is the axial mode index, 𝑣∥ is the axial electron velocity, and +/- sign depends on which oneof the forward and backward partial waves of the mode interacts with the electron beam. This Doppler term arises
from the requirement that the electron stays in phase with the propagating partial wave as it moves along thecavity. In the case of the fundamental axial mode excitation, the electrons interact with both partial waves, so thatthe condition (1) does not contain electron velocity, and the operation becomes almost insensitive to the velocity
spread:𝜔 ≈ 𝑛Ω𝑐 .

(2)

To overcome the described problem we proposed to use several short widenings of the cavity wall placed near
the field zeroes of the desired high axial mode. These irregularities act as phase correctors, adding an extra 𝜋shift to the wave phase. As a result, instead of changing its sign in points along the cavity axis, the operating

mode becomes almost unipolar (Fig. 1) and, consequently, well couples with the electron beam in the regime ofgyrotron resonance (2). Besides, the phase correctors affect also the axial structure of the fundamental gyrotron
mode, which now acquires (𝑙 − 1)close-to- phase shifts along the axis leading to the corresponding

dependency of the excitation efficiency on the velocity spread.
The proposed scheme was simulated using two independent methods. It should be noted, that the natural desire
when designing the cavity is to make the total length of the phase correctors as small as possible so that theirinfluence on the electron-wave interaction be minimized. This does not allow one to use a common for theslightly-irregular cavities approach based on non-uniform string equation for the operating mode since theassumption of slow cavity radius change necessary for such an approximation is often violated near the phasecorrectors. Instead, one has to take into account possible transformations of the operating mode into other radialmodes. Therefore, the first method we used is based on the coupling waves approximations, when the cavity fieldin every cross-section is treated as a sum of mutually-scattering waveguide modes, propagating in a waveguideof the same cross-section. In order to illustrate the method, we designed a cavity with TE4,8 operating mode andtwo phase correctors. The correctors have a form of a triangle with the base length of ~4𝜆, for which thecondition of non-uniform string approximation applicability is essentially violated, and the single-mode
approximation should be inadequate.

Fig. 1. Schematics of the conventional gyrotron cavity (a) and the cavity with phase correctors (b).
Transformations of the fundamental axial mode and of the mode with three axial variations are shown.
Fig. 2a,b shows the results of the cavity spectrum analysis, which include the resonance response of thecavity when it is fed from the collector side as a function of feeding signal frequency, as well as the cavity
eigenmode profiles. The eigenmodes are obtained as the solution of the eigenvalue problem with radiation
boundary conditions. Fig. 2a shows these characteristics obtained in a single-mode approximation, and Fig. 2btakes into account modes conversion. It is evident, that the simple explanation of the scheme (Fig. 1) is adequate
in common and predicts the transformation of the conventional cavity modes in a right way. At the same time,
considering the scattering is essential for correct describing the modes profiles and, especially, Q-factors. It may
be seen, that both the frequency and the Q-factor of the operating TE4,8,3 mode are very weakly sensitive to cavity
wall corrugation, as well as to the modes scattering. Mainly, this is because the correctors are positioned near thezeroes of the mode. On the contrary, the other modes, and especially the fundamental near-to-cutoff mode, aresubstantially distorted by the phase correctors, which also demonstrates the high selective properties of the
proposed scheme.

Fig. 2. Results of 1-D (a,b) and Finite Element Method (c,d) simulations. (a,b) : Response of the cavity when it
is fed from the collector end, taken in various axial points, and profiles of the eigenmodes field amplitudes withcorrespondent diffractive quality factors in single-mode (a) and multimode (b) approximations. In (a), the dashedcurve is the response of the conventional regular cavity, and gray curves in the profiles are the real parts of thecomplex amplitudes. (c,d) : Eigenmodes field patterns and diffractive Q-factors obtained by the finite element
method, as well as comparison of the axial field profiles obtained by this method (gray curves) and by the 1-D
approach (black dotted curves). The results correspondent to cases of l = 2 (a) and l = 3 (b) are shown.
The 1-D approach based on coupling waves is very convenient for applying it in “hot” gyrotron simulations
since it allows explicit introducing of the amplitude of the resonant (in sense of the condition (2)) radial mode in
the equations of electron motion. Nevertheless, to be sure that the obtained numerical results are correct, we havemade additional simulations of the “cold” scheme on the basis of more straightforward approach of solving theMaxwell equations by the finite element method. The patterns of the azimuthal electric field amplitude, as wellas the comparison of the axial modes profiles obtained by the two approaches, are shown in Fig. 2c,d. Evidently,
the results of different simulations are in good agreement, which validates our conclusions.
The designed cavity was then used for numerical simulations of the fourth-cyclotron-harmonic 30 kV Large
Orbit Gyrotron, where it demonstrated a possibility to decrease the share of Ohmic losses from 95% predicted
for the conventional cylindrical cavity down to 60%, which not only increases the output efficiency but alsosignificantly decreases the cavity heating during the CW operation.

Increasing the high-harmonic operation selectivity of an oversized cavity
Another method based on the cavity deformation allows essential discrimination of the parasitic lowfrequency excitations in a high-cyclotron-harmonic gyrotron even when operating in a quite overmoded cavity.
In a certain sense, this method originates from the one described in the previous section and further develops its
selective properties. The main idea is to make a short deformation of the cavity wall which has minimal effect on
the operating mode, but dramatically affects all the parasitic modes. It turns out that a possible solution is
introducing a rectangular groove with very special, resonant dimensions. The effect of these resonant dimensions
is a complete “invisibility” of the groove for the operating mode so that the field profile in the electron beam
position and the quality factor remain the same as in the original regular cavity. On the parasitic modes, on thecontrary, this groove has a strong scattering effect, which decreases their Q-factors and spoils the axial field
profiles, thus significantly increasing their starting currents.
To demonstrate the method, we simulated a modification of the cavity of a 670 GHz gyrotron operating at
the fundamental cyclotron resonance at the TE31,8 mode [4]. An analysis of the eigenmodes spectrum of thiscavity shows (Fig. 3a,b) that in the operating range of magnetic fields, the resonance is possible at the second
cyclotron harmonic at the TE63,15 mode at 1.34 THz. Nevertheless, in the traditional cylindrical system, thestarting current of this mode is slightly higher than the starting current of the low-frequency modes TE30,8 andTE31,8 excited at the fundamental cyclotron resonance (Fig. 4a). To discriminate these modes, we proposed toapply a groove with a depth of about 0.12 mm to the cavity wall having a radius of 4.54 mm. With this depth, theradius of the resonator inside the groove approximately corresponds to the critical radius for the TE 63,16 mode.
The longitudinal position of the groove along the axis of the resonator divides its length in the ratio 1 to 3 (Fig. 5),
which makes it possible to discriminate not only the fundamental but also higher axial parasitic modes with two
variations of the field.

Fig. 3. Eigenmodes spectrum of the regular 670 GHz gyrotron cavity in the vicinity of the first (a) and second (b)cyclotron harmonics. The relative heights of the bars correspond to the modes coupling strength for a given
electron beam radius of 2.3 mm. Only modes with strongest coupling are labeled.

Fig. 4. Starting currents of the fundamental and second cyclotron harmonic oscillations in the regular (a) andmodified (b) gyrotron cavity.

Fig. 5. Results of electrodynamic cavity simulations. A two-dimensional (r-z) pattern of the azimuthal electricfield of the TE63,15 mode in the presence of the groove (a) and comparison of the axial profiles of the TE63,15 (b),TE30,8 (c) and TE31,8 (d) modes in the vicinity of the electron beam for the regular and modified cavity. In themodified cavity, two modes with approximately equal low Q-factors appear in the last two cases, which are
actually the descendants of the two lowest axial modes of the regular cavity.

The eigenmodes of the modified resonator were again calculated by the Finite Element Method for the
Maxwell equations. By choosing the geometric dimensions of the groove, we managed to achieve its almost
complete “transparency” for the TE63,15 mode, keeping both the quality factor of this mode and the longitudinal
field profile in the position of the electron beam unchanged (Fig. 5a,b). The latter is an important feature that
distinguishes this method from the one described in the previous section. Namely, in this case, the field profile
remains unchanged even inside the groove, whereas the region located inside the phase corrector drops out of theelectron-wave interaction. Calculation of the eigenmodes of the modified resonator near the resonance at the first
cyclotron harmonic, as expected, demonstrated a strong distortion of the longitudinal profiles of these modes withrespect to the unperturbed system and a significant decrease in their Q-factors (Fig. 5c,d).
Calculation of the starting currents confirmed the effectiveness of discrimination of parasitic modes in the
proposed resonator (Fig. 4b). The deformation of the low-frequency modes turned out to be so strong that theirstarting currents became several times greater than the practically unchanged starting current of the operating
mode at the second cyclotron harmonic.

Conclusion
Comprehensive numerical simulations prove the capability of the proposed methods to essentially decrease
the share of Ohmic losses and to increase the operation selectivity. These methods may be especially useful whenapplied in high-harmonic gyrotrons operating in the THz frequency range.

References[1] Yu. K. Kalynov, I. V. Osharin, and A. V. Savilov, “A method for suppression of spurious fundamentalharmonic waves in gyrotrons operating at the second cyclotron harmonic,” Phys. Plasm., vol. 23, no. 5, p. 053116,
2016.
[2] I. V. Bandurkin, Yu. K. Kalynov, P. B. Makhalov, I. V. Osharin, A. V. Savilov, and I. V. Zheleznov,“Simulations of sectioned cavity for high-harmonic gyrotron,” IEEE Trans. Electron Devices, vol. 64, no. 1, pp.
300–305, 2017.
[3] I. V. Bandurkin, M. Yu. Glyavin, S. V. Kuzikov, P. B. Makhalov, I. V. Osharin, and A.V. Savilov, “Method ofproviding the high cyclotron harmonic operation selectivity in a gyrotron with a spatially developed operating
mode,” IEEE Trans. Electron Devices, vol. 64, no. 9, pp. 3893–3897, 2017.
[4] M. Yu. Glyavin, A. G. Luchinin, G. S. Nusinovich, J. Rodgers, D. G. Kashyn, C. A. Romero-Talamas, and R.
Pu, “A 670 ghz gyrotron with record power and efficiency,” Appl. Phys. Lett., vol. 101, no. 15, p. 153503, 2012.

NEWS FROM THE MEMBERS OF THE CONSORTIUM
150th Anniversary of the Bulgarian Academy of Sciences

Established on 12 October 1869, the Bulgarian Academy of Sciences (BAS) is the oldest institution in modern
Bulgaria. It carries out scientific work in accordance with the universal values, national traditions, and interests.
The Bulgarian Academy of Sciences is the leading scientific, spiritual and expert center of Bulgaria. It conducts
research, training, and activities of national and international importance and solves problems related to thedevelopment of Bulgarian society and state.
Today, BAS comprises 42 scientific institutes and 8 specialized units. One of them is the Institute ofElectronics, which is a longstanding collaborator to FIR UF and a member of the International Consortium
on the Development of the High-Power Terahertz Science and Technology. The Academy employs about
3,000 scientists, accounting for about 15% of those engaged with science in Bulgaria. BAS produces about halfof the scientific output in the country. The main divisions in which the institutes of the Academy conduct
fundamental and applied studies and training are:
 Information and Communication Sciences and Technologies







Institute of Mathematics and Informatics
Institute of Mechanics
Institute of Robotics
Institute of Information and Communication Technologies
National Laboratory of Computer Virology
Laboratory of Telematics

 Energy Resources and Energy Efficiency
Institute of Nuclear Research and Nuclear Energy
Institute of Electrochemistry and Energy Systems
Institute of Chemical Engineering
Central Laboratory of Solar Energy and New Energy Sources Nanosciences, New Materials, and Technologies












Institute of Solid State Physics “Academician Georgi Nadjakov”
Institute of Electronics “Acad. Emil Djakov”
Institute of Optical Materials and Technologies “Academician Jordan Malinowski”
Institute of Mineralogy and Crystallography “Academician Ivan Kostov”
Institute of Metal Science, Equipment and Technologies with Hydro- and Aerodynamics Centre “Acad. Angel
Balevski”
Institute of General and Inorganic Chemistry
Institute of Organic Chemistry with Center of Phytochemistry
Institute of Physical Chemistry “Academician Rostislaw Kaischew”
Institute of Polymers
Institute of Catalysis
Central Laboratory of Applied Physics – Plovdiv

 Biomedicine and Quality of Life

Institute of Molecular Biology “Acad. Roumen Tsanev”
Institute of Neurobiology
Institute of Microbiology “Stephan Angeloff”
Institute of Biophysics and Biomedical EngineeringInstitute of Biology and Immunology of Reproduction “Acad. Kiril Bratanov”
Institute of Experimental Morphology, Pathology and Anthropology with Museum
 Biodiversity, Bioresources and Ecology






Institute of Biodiversity and Ecosystem Research
Forest Research Institute
Institute of Plant Physiology and Genetics
National Museum of Natural History
Botanical Garden of BAS

 Climate Change, Hazards and Natural ResourcesGeological Institute “Strashimir Dimitrov”
National Institute of Geophysics, Geodesy and Geography
Climate, Atmosphere and Water Research Institute
Institute of Oceanology “Fridtjof Nansen”

 Astronomy, Space Research, and TechnologiesInstitute of Astronomy and National Astronomical Observatory
Space Research and Technologies Institute Cultural-historical Heritage and National Identity








Institute for Bulgarian Language “Prof. Lyubomir Andreychin”
Institute for Literature
Institute of Balkan Studies and Center of Thracology “Prof. Alexander Fol”
Institute for Historical Studies
Institute of Ethnology and Folklore Studies with Ethnographic Museum
Institute of Art Studies
National Archaeological Institute with Museum
Cyrillo-Methodian Research Centre Man and SocietyEconomic Research InstituteInstitute for the State and the Law
Institute for Population and Human Studies
Institute for the Study of Societies and Knowledge
The 150th Anniversary of the Academy has been marked by a commemorative post stamp, a silver coin, and many celebrations. For
more information please visit the website of the BAS.

Researchers from IAP-RAS won young scientists grant
A project led by Dr. Andrey Fokin in collaboration with Dr. Ilya Bandurkin and Dr. Ivan Osharin from IAPRAS has won a grant from the Russian Science Foundation in the framework of the presidential program forsupport of projects conducted by leading scientists including young researchers. The title of the projects is:“Terahertz gyrotrons operating at high cyclotron harmonics with super-selective resonators.”

A. Fokin and I. Bandurkin – researchers from IAP-RAS and collaborators of FIR-UF
The project aims to develop compact sources of intense (tens of watts) narrow-band terahertz radiation in thefrequency range 0.5 - 1.5 THz, which is demanded by many novel applications in various fields of the high-power
Terahertz science and technologies such as for example terahertz vision, selective effects on cancer cells
treatment and high resolution tomography. The problem of creating relatively intense (with a power of at least
tens of watts) and, at the same time, commercially available to a wide range of consumers (in terms of bothcompactness and cost) radiation sources with a frequency of about 1 THz and above is still not resolved. At
present, the need for sources of terahertz radiation is dictated by such relevant applications as spectroscopy anddiagnostics of various media, terahertz vision, and remote sensing of hazardous substances, biophysical andbiochemical studies, etc. The main objective of the project will be the search and demonstration of ways to pusha very advanced class of sources of coherent electromagnetic radiation - electron cyclotron masers (gyrotrons) –forward into the area of parameters not yet mastered by these generators, but very important for applications. The
uniqueness of the developed sources is determined by a combination of several factors at once: radiation
frequency above 1 THz, relatively low magnetic fields due to operation at high cyclotron harmonics, output powerat the level of tens of Watts and above, operation in continuous generation regime. Moreover, the use of low
operating magnetic fields, as well as electron beams with relatively low energy, should ensure the compactnessof such sources and, accordingly, their availability to a wide range of consumers. The project will include thedevelopment and creation of compact gyrotrons with moderate energetics of working electron beams (particle
energy – tens of keV, current – several A), in which the selectivity of the excitation of oscillations at highharmonics of the cyclotron frequency will be achieved through the use of new electrodynamic systems with

discrimination of parasitic oscillations at low cyclotron harmonics. The efficiency of the approaches proposed by
the authors will be tested in a number of demonstration experiments both in the millimeter and in the sub-mm
wavelength range. Within the framework of this project, in order to increase the selectivity of generation in
gyrotrons, it is planned to explore the original approach, developed with the direct participation of the projectauthors, and based on the modification of the gyrotron resonator by applying scattering elements (rectangulargrooves) to the side wall. As shown in the previous theoretical works of the authors of the project, such selection
elements can have a significant destructive effect on the parasitic low-frequency oscillations, almost without
effect on the operating mode. In the course of the project, an experimental verification of this possibility isplanned.
The uniqueness of such radiation source, in addition to the record high frequency for this class of devices, isdetermined by a combination of several other factors important for the users, namely, the relatively highgeneration power when operating in continuous-wave regime and compactness of the device. Currently, there are
no analogs of such systems in the world. Undoubtedly, generators of this type will be in demand for a number ofimportant problems arising in such fundamental applications as spectroscopy and diagnostics of various media,
technical applications in the field of security control and countering terrorism, biophysical and biochemical
studies, etc.
Source: IAP-RAS

FORTHCOMING EVENTSAnnouncement of TERA-2020 in Tomsk (*.PPTX)
Pre-registration
Contacts: Yury Kistenev, yv.kistenev@gmail.com
Last Event: TERA-2018

The 13th German Microwave Conference 2020, March 09–11, will be hosted by Brandenburg University ofTechnology Cottbus-Senftenberg in cooperation with IMA e.V. and VDE/ITG. GeMiC 2020 provides aunique platform to exchange with experts and to meet colleagues from industry, research institutes, anduniversities.
Download Call for Papers
Website of the conference

For more details follow the link.

For more details follow the link.

For more details follow the link.

For more details follow the link.

For more details follow the link.

For more details follow the link.

For more details follow the link.

For more details follow the link.

For more details follow the link.

For more details follow the link.

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 June 2019, i.e. after issuing the previous Newsletter #12.
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
T. Saito, S. Tanaka, R. Shinbayashi, Y. Tatematsu, Y. Yamaguchi, M. Fukunari, S. Kubo, T. Shimozuma, K.
Tanaka, M. Nishiura, “Oscillation Characteristics of a High Power 300 GHz Band Pulsed Gyrotron for Use inCollective Thomson Scattering Diagnostics,” Plasma and Fusion Research, vol. 14 (2019) 1406104. DOI:
10.1585/pfr.14.1406104.
http://www.jspf.or.jp/PFR/PFR_articles/pfr2019/pfr2019_14-1406104.html
Rozental R.M., Fedotov A.E., Ginzburg N.S. et al,” Experimental Observation of Chaotic Generation at 1.5%
Spectral Width in a Gyrotron under Large Supercriticality Conditions,” Tech. Phys. Lett. vol.45 (2019) 511.
DOI:10.1134/S1063785019050304.
https://link.springer.com/article/10.1134/S1063785019050304
F. Wilde, S. Marsen, T. Stange, D. Moseev, J.W. Oosterbeek, H.P. Laqua, R.C. Wolf, K. Avramidis, G.
Gantenbein, I.Gr. Pagonakis, S. Illy, J. Jelonnek, M.K. Thumm, “Automated mode recovery for gyrotrons
demonstrated at Wendelstein 7-X,” Fusion Engineering and Design, vol. 148 (2019) 111258.
DOI:10.1016/j.fusengdes.2019.111258.
http://www.sciencedirect.com/science/article/pii/S0920379619307367
Y. Yamamoto, T. Nawate, S. Mitsudo “Extraction of essential oils from leaves of the Japanese Lindera umbellata
Thunb. by using microwave heating distillation method,” IOP Conf. Ser.: Mater. Sci. Eng. vol. 550 (2019) 012033.
DOI: 10.1088/1757-899X/550/1/012033.
https://iopscience.iop.org/article/10.1088/1757-899X/550/1/012033
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 Conf. Ser.: Mater. Sci. Eng., vol. 550 (2019) 012032. DOI: 10.1088/1757899X/550/1/012032.
https://iopscience.iop.org/article/10.1088/1757-899X/550/1/012032
V.V. Rumyantsev, K.V. Maremyanin, A.P. Fokin, A.A. Dubinov, V.V. Utochkin, M.Yu. Glyavin, N.N.
Mikhailov, S.A. Dvoretskii, S.V. Morozov, V.I. Gavrilenko, “Second-Harmonic Generation of Subterahertz
Gyrotron Radiation by Frequency Doubling in InP:Fe and Its Application for Magnetospectroscopy of
Semiconductor Structures,” Semiconductors, vol. 53, n. 9 (2019) 1217–1221. DOI:10.1134/S1063782619090185.
https://link.springer.com/article/10.1134%2FS1063782619090185
F. Wilde, S. Marsen, T. Stange, D. Moseev, J.W. Oosterbeek, H.P. Laqua, R.C. Wolf, K. Avramidis, G.
Gantenbein, I.Gr. Pagonakis, S. Illy, J. Jelonnek, M.K. Thumm, W7-X team, “Automated mode recovery for
gyrotrons demonstrated at Wendelstein 7-X,” Fusion Engineering and Design, vol. 148 (2019) 111258.
DOI:10.1016/j.fusengdes.2019.111258.
http://www.sciencedirect.com/science/article/pii/S0920379619307367
P.C. Kalaria, M. George, S. Illy, K. A. Avramidis, G. Gantenbein, S. Ruess, M. Thumm, J. Jelonnek,"Multiphysics Modeling of Insert Cooling System for a 170-GHz, 2-MW Long-Pulse Coaxial-Cavity Gyrotron,"
IEEE Transactions on Electron Devices, vol. 66, n. 9 (2019) 4008-4015. DOI:10.1109/TED.2019.2928222.
https://ieeexplore.ieee.org/abstract/document/8779590

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/abs/10.1063/1.5109526
S.V. Egorov, A.G. Eremeev, V.V. Kholoptsev, I.V. Plotnikov, K.I. Rybakov, A.A. Sorokin, Yu.V. Bykov, “On
the correlation between the thermal instability onset and the flash sintering event,” Scripta Materialia, vol. 174(2020) 68-71. DOI:10.1016/j.scriptamat.2019.08.032.
http://www.sciencedirect.com/science/article/pii/S1359646219305123
Tsvetkov A.I., Vodopyanov A.V., Mansfeld D.A., A.P. Fokin, “The Temperature Behavior of Microwave
Absorption of Metal Oxide Powders When Heated by a 263-GHz Gyrotron Radiation,” J Infrared Milli Terahz
Waves (2019). DOI:10.1007/s10762-019-00622-z.
https://link.springer.com/article/10.1007%2Fs10762-019-00622-z
Tsvetkov A.I., Vodopyanov A.V., Mansfeld D.A., Fokin A., “The Temperature Behavior of Microwave
Absorption of Metal Oxide Powders When Heated by a 263-GHz Gyrotron Radiation,” J Infrared Milli Terahz
Waves (2019).DOI:10.1007/s10762-019-00622-z.
https://link.springer.com/article/10.1007%2Fs10762-019-00622-z
Aiello G., Scherer T., Avramidis K., et all, "Diamond Window Technology for Electron Cyclotron Heating andCurrent Drive: State of the Art,"Fusion Science and Technology, vol. 75, n. 7 (2019) 719-729.
DOI:10.1080/15361055.2019.1643690.
https://www.tandfonline.com/doi/abs/10.1080/15361055.2019.1643690?journalCode=ufst20
Bratman V., Lurie Y., Oparina Y., Savilov A., "Capabilities of Terahertz Cyclotron and Undulator Radiation
from
Short
Ultrarelativistic
Electron
Bunches,"
Instruments,
vol.
3,
n.
4
(2019).
DOI:10.3390/instruments3040055.
https://www.mdpi.com/2410-390X/3/4/55/htm
B. Publications by other authors worldwide
Shao Wei, Xu Duo, Wang Zhanliang, Gong Huarong, et al, "Stacked dual beam electron optical system for THz
integrated wideband traveling wave tube," Physics of Plasmas, vol. 26, n. 6 (2019) 063106.
DOI:10.1063/1.5096331.
https://aip.scitation.org/doi/abs/10.1063/1.5096331
R. Yan, D. Wang, H. Li, M. Mu, Y. Lian and Y. Luo, "Design of Collectors for High Average/Continuous-Wave
Power Gyro-Devices," in IEEE Transactions on Electron Devices, vol. 66, n. 3 (2019) 1512-1518. DOI:
10.1109/TED.2018.2889722.
https://ieeexplore.ieee.org/abstract/document/8613878
C. Xu et al., "Analysis of Dual-Frequency Radiation From a G-Band Extended Interaction Oscillator With Double
Sheet Beam," IEEE Transactions on Electron Devices, vol. 66, n. 7 (2019) 3184-3189.
DOI:10.1109/TED.2019.2918191.
https://ieeexplore.ieee.org/abstract/document/8731970
Nusinovich G.S., "To the theory of gyrotrons with confocal resonators," Physics of Plasmas, vol. 26, n. 5
(2019)053107. DOI:10.1063/1.5099909.
https://aip.scitation.org/doi/10.1063/1.5099909
R. K. Singh, M. Thottappan, "Simulation Investigations and Optimization of a Millimeter-Wave Gyrotron for Its
Tunability Using Magnetic and Thermal Tuning Schemes," IEEE Transactions on Electron Devices, (2019).

DOI:10.1109/TED.2019.2921680.
https://ieeexplore.ieee.org/document/8748219
S. Karmakar, R. Sudhakar, J. C. Mudiganti, R. Seshadri and M. V. Kartikeyan, "Electrical and Thermal Designof a W -Band Gyrotron Interaction Cavity," in IEEE Transactions on Plasma Science, vol. 47, no. 7 (2019) 31553159. DOI:10.1109/TPS.2019.2918138.
https://ieeexplore.ieee.org/abstract/document/8730430
Trofimov P.A., Louksha O.I., "Development of the gyrotron collector system with multistage energy
recovery,"Journal of Physics: Conference Series, vol. 1236 (2019) 012047. DOI:10.1088/17426596/1236/1/012047.
https://iopscience.iop.org/article/10.1088/1742-6596/1236/1/012047
Singh S., Kartikeyan, M.V., “Full-wave Analysis of Plasma-Loaded Coaxial Cavity with Wedge-Shaped
Corrugations on the Insert,” J Infrared Milli Terahz Waves (2019). DOI:10.1007/s10762-019-00611-2.
https://link.springer.com/article/10.1007/s10762-019-00611-2
Kaltenecker K.J., Kelleher E.J.R., Zhou B., et al., “Attenuation of THz Beams: A “How to” Tutorial,” J Infrared
Milli Terahz Waves (2019). DOI:10.1007/s10762-019-00608-x.
https://link.springer.com/article/10.1007/s10762-019-00608-x
You X., Ako R. T., Lee W. S. L., Low M. X., Bhaskaran M., Sriram S., Fumeaux C., Withayachumnankul W.,“Terahertz Reflectarray with Enhanced Bandwidth,” Adv. Optical Mater. 2019, 1900791.
DOI:10.1002/adom.201900791.
https://onlinelibrary.wiley.com/doi/abs/10.1002/adom.201900791
S. Yuvaraj, D. A. Jose, S. Singh, M.V. Kartikeyan, "Effect of Insert Misalignment on a Triangular CorrugatedCoaxial Cavity Gyrotron," IEEE Transactions on Electron Devices, (2019). DOI:10.1109/TED.2019.2925914.
https://ieeexplore.ieee.org/document/8765396
A. Mishra, A. K. Sinha, A. Bera, "Tapered Cavity Measurement for 42-GHz, 200-kW Gyrotron," IEEE
Transactions on Plasma Science, vol. 47, n. 7 (2019) 3148-3154. DOI:10.1109/TPS.2019.2921614.
https://ieeexplore.ieee.org/document/8746807
C. An, D. Zhang, J. Zhang and H. Zhong, "Theoretical Analysis and PIC Simulation of a 220-GHz SecondHarmonic Confocal Waveguide Gyro-TWT Amplifier," IEEE Transactions on Electron Devices, (2019). DOI:
10.1109/TED.2019.2925895.
https://ieeexplore.ieee.org/abstract/document/8766862
K. K. O et al., "Opening Terahertz for Everyday Applications," IEEE Communications Magazine, vol. 57, n. 8
(2019) 70-76. DOI:10.1109/MCOM.2019.1800909.
https://ieeexplore.ieee.org/abstract/document/8808165
J. Zhu, C. Du, F. Li, L. Bao and P. Liu, "Free-Electron-Driven Multi-Frequency Terahertz Radiation on a SuperGrating Structure," in IEEE Access. DOI: 10.1109/ACCESS.2019.2938270.
https://ieeexplore.ieee.org/document/8819920
Rybakov K., Egorov S., Eremeev A., Kholoptsev V., Plotnikov I., Sorokin, “Ultra-rapid microwave sintering
employing thermal instability and resonant absorption,” Journal of Materials Research, vol. 34, n. 15 (2019)2620-2634. DOI:10.1557/jmr.2019.232.
https://www.cambridge.org/core/journals/journal-of-materials-research/article/ultrarapid-microwave-sinteringemploying-thermal-instability-and-resonant-absorption/CDA7D3ED0CC1032B58C27CEFC1ECCBB7

Z. Hajijamali-Arani, B. Jazi, "About Azimuthal Acceleration of the Electrons by Azimuthal Surface Waves in a
Dielectric-Lined Circular Waveguide With Two Thin Annular Rotating Electron Beams," IEEE Transactions on
Plasma Science, vol. 47, n. 8 (2019) 4012-4025. DOI:10.1109/TPS.2019.2927015.
https://ieeexplore.ieee.org/abstract/document/8767963
Y. Xing, Y. Zhang, N. Xu, Y. Ke, B. Li, Deng, "A Cold-Cathode Microwave and Terahertz Radiation Source:
Experimental Realization @10’s GHz and Computational Design @THz," IEEE Electron Device Letters, vol. 40,
n. 9 (2019) 1534-1537. DOI: 10.1109/LED.2019.2932097.
https://ieeexplore.ieee.org/abstract/document/8782657
K. Wang et al., "A Broadband TE01–TE11 Mode Converter With Elliptical Section for Gyro-TWTs," IEEE
Transactions on Microwave Theory and Techniques, vol. 67, n. 9 (2019) 3586-3594.
DOI:10.1109/TMTT.2019.2925065.
https://ieeexplore.ieee.org/abstract/document/8765606
C. An, D. Zhang, J. Zhang, Zhong, "Theoretical Analysis and PIC Simulation of a 220-GHz Second-Harmonic
Confocal Waveguide Gyro-TWT Amplifier," IEEE Transactions on Electron Devices, vol. 66, n. 9 (2019) 40164021. DOI: 10.1109/TED.2019.2925895.
https://ieeexplore.ieee.org/abstract/document/8766862
S. Yuvaraj, D. A. Jose, S. Singh and M. V. Kartikeyan, "Effect of Insert Misalignment on a Triangular CorrugatedCoaxial Cavity Gyrotron," IEEE Transactions on Electron Devices, vol. 66, n. 9 (2019) 4029-4035, Sept. 2019..
DOI:10.1109/TED.2019.2925914.
https://ieeexplore.ieee.org/abstract/document/8765396
Zhang S., Xue Q., Wang X., Wang K., Zhao D., "Ohmic loss analysis for coaxial cavities of high-power highfrequency gyrotrons," AIP Advances, vol. 9, n. 8 (2019) 085017. DOI:10.1063/1.5118828.
https://aip.scitation.org/doi/full/10.1063/1.5118828
K. K. O et al., "Opening Terahertz for Everyday Applications," IEEE Communications Magazine, vol. 57, n. 8
(2019) 70-76. DOI:10.1109/MCOM.2019.1800909.
https://ieeexplore.ieee.org/abstract/document/8808165
C. Gao, N. Alaniva, E.P. Saliba, E.L. Sesti, P.T. Judge, F.J. Scott, Th. Halbritter, S.Th. Sigurdsson, A.B. Barnes,“Frequency-chirped Dynamic Nuclear Polarization with Magic Angle Spinning Using a Frequency-agile
Gyrotron,” Journal of Magnetic Resonance, (2019). DOI:10.1016/j.jmr.2019.106586.
http://www.sciencedirect.com/science/article/pii/S1090780719302253
K. Singh, J. Itteera, R.R. Singh, S. Malhotra, D. Rathi, "Development of Normal Conducting Cavity Magnet for
42 GHz 200 kW Long Pulse Gyrotron," IEEE Transactions on Magnetics, (2019).
DOI:10.1109/TMAG.2019.2931864.
https://ieeexplore.ieee.org/abstract/document/8809268
Kimberly S. Reichel, Nicolas Lozada-Smith, Ishan D. Joshipura, Jianjun Ma, Rabi Shrestha, Rajind Mendis,
Michael D. Dickey, Daniel M. Mittleman, "Terahertz waveguide signal processing: passive and active devices,"
Proc. SPIE 11124, Terahertz Emitters, Receivers, and Applications X, 111240S (6 September 2019). DOI:
10.1117/12.2527413.
https://www.spiedigitallibrary.org/conference-proceedings-of-spie/11124/111240S/Terahertz-waveguidesignal-processing-passive-and-active-devices/10.1117/12.2527413.short?SSO=1
Tkachova T.I., Shcherbinin V.I., Tkachenko V.I., ”Selectivity Properties of Cylindrical Waveguides with
Longitudinal Wall Corrugations for Second-Harmonic Gyrotrons,” Journal of Infrared Millimeter, and Terahertz
Waves (2019). DOI:10.1007/s10762-019-00623-y.
https://link.springer.com/article/10.1007%2Fs10762-019-00623-y

M. Witman, E. Avraham, R. Ben-Moshe, M. Pilossof , M. Einat, "Long-Pulse Uncooled Copper Magnet for
Gyrotron," IEEE Transactions on Electron Devices (2019). DOI:10.1109/TED.2019.2937884.
https://ieeexplore.ieee.org/document/8834846
R.G. Griffin, T.M. Swager, R.J. Temkin, “High frequency dynamic nuclear polarization: New directions for the
21st century,” Journal of Magnetic Resonance, vol. 306 (2019) 128-133. DOI:10.1016/j.jmr.2019.07.019.
http://www.sciencedirect.com/science/article/pii/S1090780719301430
M. Reese, Ch. George, Ch. Yang, S. Jawla, J. T. Grün, H.Schwalbe, Ch. Redfield, Ri.J. Temkin, R.G. Griffin, “Modular, triple-resonance, transmission line DNP MAS probe for 500 MHz/330 GHz,” vol. 307 (2019).
DOI:10.1016/j.jmr.2019.106573.
http://www.sciencedirect.com/science/article/pii/S1090780719302125
Honda Y., Shimada M., Aryshev A., Kato R., Miyajima T., Obina T., Takai R., Uchiyama T., Yamamoto N.,“High-efficiency broadband THz emission via diffraction-radiation cavity,” Phys. Rev. Accel. Beams, vol. 22, n.
4 (2019) 040703. DOI:10.1103/PhysRevAccelBeams.22.040703.
https://link.aps.org/doi/10.1103/PhysRevAccelBeams.22.040703
A. Bera et al., "Development of 42-GHz, 200-kW Gyrotron for Indian Tokamak System Tested in the Regime of
Short Pulselength," IEEE Transactions on Plasma Science, (2019). DOI:10.1109/TPS.2019.2938540.
https://ieeexplore.ieee.org/document/8845778
Hesler J., Prasankumar R., Tignon J., “Advances in terahertz solid-state physics and devices,” ournal of Applied
Physics, vol. 126, no. 11 (2019) 110401. DOI: 10.1063/1.5122975.
https://aip.scitation.org/doi/full/10.1063/1.5122975
Appanam K.J., Nusinovich G.S., Beaudoin B.L., Ting A.C., Narayan A.H., Antonsen T.M., "Physics of efficientgridless tetrodes with intense electron beams,"Physics of Plasmas, vol. 26, n. 9 (2019)093101.
DOI:10.1063/1.5090886.
https://aip.scitation.org/doi/10.1063/1.5090886
Mazieres V., Pascaud R., Liard L., Dap S., Clergereaux R., Pscal O., "Plasma generation using time reversal of
microwaves,"Applied Physics Letters, vol. 115, n. 15 (2019)154101.DOI:10.1063/1.5126198.
https://aip.scitation.org/doi/full/10.1063/1.5126198
C Patents
Tunable band-close waveguide filter
Inventors: Gojkhman Mikhail Borisovich (RU), Gromov Aleksandr Viktorovich (RU), Palitsin Aleksej
Valentinovich (RU)
Russian Federation Invention: 2019100408
Date of publication: 06.08.2019 Bull. № 22https://www.researchgate.net/publication/335030080_No_2_696_817 [accessed Oct 17 2019].
Methods and devices for producing an electron beam
Inventors: Einat, Moshe (Ariel, IL); Orbach, Yafit (Ariel, IL); Pilossof, Moritz (Ariel, IL)
US Patent Application: 20190272968
Date of publication: 09/05/2019
http://www.freepatentsonline.com/y2019/0272968.html
System and method for launching guided electromagnetic waves with impedance matching
Inventors: Rappaport, Harold Lee (Middletown, NJ, US)
US Patent: 10305192
Date of publication: 05/28/2019http://www.freepatentsonline.com/10305192.html
Transmission device with impairment compensation and methods for use therewith
Inventors: Barzegar, Farhad (Branchburg, NJ, US); Gerszberg, Irwin (Kendall Park, NJ, US); Bennett, Robert(Southold, NY, US); Henry, Paul Shala (Holmdel, NJ, US)
US Patent: 10355790
Date of publication: 07/16/2019
http://www.freepatentsonline.com/10355790.html
Method and apparatus of communication utilizing waveguide and wireless devices
Inventors: David M. Britz, John W. MacNeill, David DeVincentis, Robert Bennett, Paul Shala Henry, Irwin
Gerszberg, Farhad, Barzegar, Thomas M. Willis, III, Donald J. Barnickel
US Patent: 20190007096A1
Date of application granted: 06/08/2019https://patents.google.com/patent/US20190007096A1/en
Triode electron gun
Inventors: Allen, Curtis (Redwood City, CA, US)
US Patent Application: 20190272969
Date of publication: 09/05/2019
http://www.freepatentsonline.com/y2019/0272969.html
Apparatus and method for guided wave communications using an absorber
Inventors: Paul Shala Henry, Giovanni Vannucci, Thomas M. Willis, III
US Patent: US20190173151A1
Date of publication: 06/06/2019https://patents.google.com/patent/US20190173151A1/en
System and method for identifying materials using a THz spectral fingerprint in a media with high watercontent
Inventor: Patrick K Brady
US Patent: 10401283B2
Date of publication:
https://patents.google.com/patent/US10401283B2/en

NEW BOOKSWang, Minjie, and Eui-Hyeok Yang. "Terahertz Applications of Graphene." Handbook of Graphene:
Technology and Innovations (2019): 341.
Sakoda K. (eds) “Electromagnetic Metamaterials. Springer Series in Materials Science,” (2019) vol 287. Springer,
Singapore. DOI: 10.1007/978-981-13-8649-7. ISSN 0933-033X.
https://www.springer.com/gp/book/9789811386480
Demtröder W., “Electrodynamics and Optics,” Springer, 2019). ISBN 978-3-030-02291-4. DOI: 10.1007/9783-030-02291-4.
https://www.springer.com/gp/book/9783030022891
Thomas Elsaesser, Klaus Reimann and Michael Woerner, “Concepts and Applications of Nonlinear Terahertz
Spectroscopy,” 2019 Morgan & Claypool Publishers. Online ISBN: 978-1-64327-216-0, Print ISBN: 978-164327-213-9. DOI: 10.1088/2053-2571/aae931.
https://iopscience.iop.org/book/978-1-64327-216-0

NEWS FROM THE NET (OUR BROADER HORIZONS)The Nobel Prizes in Physics and Chemistry 2019
The Nobel Prize in Physics 2019 was awarded "for contributions to our understanding of the evolution of theuniverse and Earth's place in the cosmos" with one half to James Peebles "for theoretical discoveries in physicalcosmology", the other half jointly to Michel Mayor and Didier Queloz "for the discovery of an exoplanet orbitinga solar-type star."
For more details please see the press release at the following link.
Source: The Nobel Prize in Physics 2019. NobelPrize.org. Nobel Media AB 2019. Wed. 9 Oct 2019
Akira Yoshino, honorary fellow at Asahi Kasei Corp., has won this year's Nobel Prize in Chemistry, the Royal
Swedish Academy of Sciences announced on Oct. 9 in Stockholm. Yoshino, 71, a professor at Meijo University,
shares the prize with two other researchers for the development of lithium-ion batteries. The co-laureates are John
Goodenough of the University of Texas, and M. Stanley Whittingham of Binghamton University, State Universityof New York. The Royal Swedish Academy of Sciences said lithium-ion batteries -- "secondary cell"
rechargeable and reusable batteries widely used in mobile phones and laptop computers -- "have revolutionized
our lives." With this award, the number of Japanese Nobel laureates has become 27 altogether.
Source: The Mainichi

Chopping megawatt-level output power of gyrotron for particle acceleration
In a posting of August 12, 2019, the MIT News reported that Julian Picard was awarded the Outstanding Student
Paper Award from the IEEE Nuclear and Plasma Sciences Society at the 2019 Pulsed Power and Plasma Science
Conference in June for a paper published in the journal Applied Physics Letters, which describes a method to“chop” the pulse of a powerful gyrotron with a megawatt-level output power operating at a frequency of 110
GHz. The experimental setup involves a semiconductor wafer (silicon or gallium arsenide), which is irradiatedby a laser beam. As a result of the irradiation, plasma is created inside the silicon which reflects the microwaves
produced by the gyrotron for as long as the laser pulse continues. The reflected high-frequency and short-pulse
gyrotron radiation (chopped to 10 ns simply by turning on and off the laser)) can then be directed towards a highfrequency, high-gradient accelerating structure. It has been observed, however, that only 70 percent of theradiation is reflected while the rest 30 percent is absorbed or pass through the silicon wafer. More importantly, it
has been found that an increase of the gyrotron output power toward megawatt levels leads to an increase of thereflection as well reaching 80-85 percent. In this laser-driven semiconductor switch (LDSS) thephotoconductivity was induced in the wafers using a 532 nm laser, which produced 6 ns, 230 mJ pulses. Using
two active wafers, pulses of variable length down to 3 ns duration were created. The switch was tested at incident
110 GHz RF power levels up to 600 kW.
The Plasma Science and Fusion Center (PSFC) at MIT is collaborating with a group from Stanford Universitythat designs accelerator cavities, which can now be tested with the “Megawatt Microwave Pulse Chopper.”Source: MIT News

Novel Highly Sensitive Diode which Converts Microwaves to Electricity
Recently, the Japan Science and Technology Agency (JST), Fujitsu Limited, and the Tokyo Metropolitan
University developed a highly sensitive new rectifying element in the form of a nanowire backward diode which
can covert low-power microwaves into electricity. It is expected that such devices can be used for harvestingenergy from the ambient radio waves in the environment such as, for example, that are produced by the mobile
base stations and wireless networks. This is important for building networks of sensors for IoT that do not require
batteries. The selectivity of this novel nanowire backward diode is more than one order of magnitude higher thanthat of the available Schottky barrier diodes. This technology allows converting weak microwaves (with power
as low as 100 nW) to electricity. The backward diode is formed by joining two different types of semiconductors
and operate on a principle that involves the tunnel effect. It is characterized by steep rectification at zero bias.
The experiments carried out at a frequency of 2.4 GHz (which is widely used in the contemporary 4G LTE and
Wi-Fi communications) have demonstrated a sensitivity of 700 kV/W. This value is more than 10 times higher
than the sensitivity of the conventional Schottkiy barrier diode, which amounts to only 60KV/W.
Source: ACN Newswire

A New Way to Convert Heat to Electricity
The discovery made by an international team of researchers from China and the USA has been published in thejournal Science Advances. It is considered a promising new way to provide more efficient energy generationfrom heat in various instances like car exhaust, interplanetary space probes, and industrial processes. The
discovery is based on quasi particles called paramagnons. Paramagnons are magnons (a collective excitation of
the electrons' spin structure in a crystal lattice) in magnetic materials which are in their high temperature,
disordered (paramagnetic) phase. In such state, the flux of their spins give rise to an effect known as magnondrag thermoelectricity. The essence of this effect is that when one side of a magnet is heated, the magnetism inthe colder side increases and drags the electrons creating electricity.
Source: Science Advances and Technology.Org

Magnetization of non-magnetic metals by laser light
Physicists from Nanyang Technological University, Singapore (NTU Singapore) and the Niels Bohr Institute in
Copenhagen, Denmark, have developed a method to turn a non-magnetic metal into a magnet using laser light.
They have found that when the light irradiation is strong enough, the plasmons in a non-magnetic metallic disk
can spontaneously rotate in either a left-handed or right-handed fashion, even when driven by linearly polarised
light. According to their work, when a plasmon's strong internal fields modify a material's electronic band
structure it transforms also the plasmon as well, creating a feedback loop enabling the plasmon to exhibit
spontaneously a chirality. It is namely this chiral motion of the plasmon that produces a magnetization whichthen made the non-ferrous metallic disk magnetic.
Source: Phys Org