[Show abstract][Hide abstract] ABSTRACT: The capabilities of two types of terahertz sources based on stimulated Smith-Purcell radiation of electrons in open cavities are discussed. A series of developed pulsed orotrons provides coherent radiation with an output power of 1-0.1 W in the frequency range of 90-410 GHz, with high frequency stability and broad-band electromechanical frequency tuning. A promising alternative source with smaller currents than that in orotrons is a frequency multiplier based on excitation of a surface wave of a periodic structure and Smith-Purcell radiation of arising electron bunches inside the orotron cavity. In contrast to a number of works where only an open grating is used, exploiting a cavity enables a stimulated radiation process with a much higher power. The developed theory demonstrates the possibility of single-mode generation in such multipliers with wide electron beams.
[Show abstract][Hide abstract] ABSTRACT: An orotronlike feedback can provide a significant increase in the selectivity and power of frequency-multiplied Smith-Purcell radiation of the electron bunches formed in the course of self-excitation of a grating surface eigenmode. This method looks promising for efficient terahertz generation from both weakly and mildly relativistic electron beams.
[Show abstract][Hide abstract] ABSTRACT: The orotron (the Smith-Purcell electron microwave tube with open cavity) provides coherent radiation at the frequencies up to 0.4 THz. The output power of 50-100 mW is obtained in the microsecond pulses with possibility of a wide frequency tuning. A proposed new scheme of a frequency-multiplication regime allows increasing the orotron operating frequency up to 0.6 THz.
Terahertz and Mid Infrared Radiation: Basic Research and Practical Applications, 2009. TERA-MIR 2009. International Workshop; 01/2009
[Show abstract][Hide abstract] ABSTRACT: In this paper, the low-voltage pulse orotron generators of the short millimeter and long submillimeter waves with power level up to 1 W have been developed. Some methods of frequency and power enhancement are proposed.
Physics and Engineering of Microwaves, Millimeter and Submillimeter Waves and Workshop on Terahertz Technologies, 2007. MSMW '07. The Sixth International Kharkov Symposium on; 07/2007
[Show abstract][Hide abstract] ABSTRACT: We have developed a series of low-voltage orotrons operated in the short-wave part of the millimeter and long-wave section
of the submillimeter wavelength range. The use of an open resonator as the electrodynamic system of the orotron ensures high
stability of the radiation frequency and a wide band of frequency tuning. The output orotron power achieved experimentally
amounts to hundreds of milliwatts, which is sufficient for many promising spectroscopy methods.
[Show abstract][Hide abstract] ABSTRACT: Summary form only given. Electron vacuum sources of coherent terahertz radiation are being now intensively developed at the Institute of Applied Physics (IAP). These devices are intended for wide-spread utilizing in many research and technical applications including spectroscopy, diagnostics of different media, communications, material processing etc. In this presentation, two types of promising THz electron oscillators, namely orotrons and gyrotrons, will be discussed. The orotrons have been realized at the IAP in collaboration with the Institute of Metrology for Time and Space and Institute of Spectroscopy. The operation of the orotron (or diffraction radiation generator) is based on the stimulated Smith-Purcell radiation of a rectilinear electron beam in a selective open cavity which has a periodic structure on one of its mirrors. At the moment, a series of the low-voltage (0.5-5 kV) orotrons developed generate in the frequency range of 0.1-0.4 THz with output power of 1.0-0.1 W and typical electrical-mechanical frequency tuning within an octave. Using same voltage, orotrons can enable higher power and frequency stability than BWOs that are most widespread devices within entire terahertz range. Orotrons with relativistic electron beams, which are studied at the IAP, are capable to provide significantly higher pulse THz power (up to MW level at ns pulse duration). Both conventional and large-orbit gyrotrons (LOGs) are also under development at the IAP The LOGs are based on the same mechanism of stimulated cyclotron radiation of electrons as conventional gyrotrons, but they are more selective when operating at higher cyclotron harmonics. Correspondingly, they work at lower magnetic fields. At the same time significantly more complicated electron guns are needed for the LOGs to provide appropriate axis-encircling electron beams. Such beams with electron energy 50-250 keV and very high compression have been obtained and powerful selective generation at 1st-5th cyclot-
ron harmonics have been demonstrated in the IAP at millimeter and submillimeter waves. When operating at the third cyclotron harmonic generation with power level of 10-20 kW has been obtained in the range of 0.3-0.42 THz. Another prospective way for developing THz sources, that will be also presented, is realization of gyro-multipliers with self-exciting LF sections and HF sections operating at high cyclotron harmonics
Plasma Science, 2006. ICOPS 2006. IEEE Conference Record - Abstracts. The 33rd IEEE International Conference on; 07/2006
[Show abstract][Hide abstract] ABSTRACT: New results in the field of high-frequency gyrotrons, gyro-multipliers and orotrons allow one to consider these electron devices as promising candidates for the realization of powerful and available sources in Terahertz range. Electron beams with a very high compression of up to a factor of 4,400 have been obtained and selective generation at the 1st-5th cyclotron harmonics have been demonstrated in Large Orbit Gyrotrons (LOGs) at millimeter and submillimeter wavelengths at operating voltages from 50 to 250 kV. When operating at the third cyclotron harmonic (TE3,8 and TE3,9 modes in the first oscillator; TE3,5 mode in the second oscillator) output power levels of 10-20 kW have been obtained in the frequency range of 0.37-0.41 THz. Gyro-multipliers with self-exciting low-frequency sections are proposed and studied theoretically. Low-voltage orotrons have been demonstrated in the frequency range of 0.1-0.4 THz with output powers of 1.0-0.1 W and typical electrical-mechanical frequency tunability within an octave range. Using the same voltage, orotrons can achieve higher power and frequency stability within the entire Terahertz range compared with BWOs that are the most widespread devices at these frequencies.
[Show abstract][Hide abstract] ABSTRACT: A vacuum-tube device for the generation of pulsed microwave radiation in the submillimeter range (up to 380 GHz) is presented, designed for use as a source in a 360 GHz high-field/high-frequency electron paramagnetic resonance (EPR) spectrometer-the pulsed Orotron. Analogous to the known continuous wave (cw) version, in the pulsed Orotron microwave radiation is generated by the interaction of a nonrelativistic electron beam with a diffraction grating (stimulated Smith-Purcell radiation) in feedback with an open Fabry-Pérot resonator construction. The presented design extends the cw Orotron by a gate electrode and a high-voltage pulsing unit to control the electron beam current. The generated pulses at 360 GHz have pulse lengths from 100 ns-10 mus and a pulse power of (22+/-5) mW. The output in a broader frequency band between 320 and 380 GHz ranges from 20 up to 60 mW. Within a 10 mus time slot, incoherent pulse trains of arbitrary duration can be generated. The pulsed Orotron has been incorporated in the quasioptical microwave bridge of a heterodyne induction mode EPR spectrometer. The first free induction decay measurements at a microwave frequency of 360 GHz and a magnetic field of 12.8 T on a polycrystalline perylenyl-ion sample are presented and future applications and extensions of Orotron-EPR spectroscopy are discussed.
[Show abstract][Hide abstract] ABSTRACT: Large orbit gyrotron (LOG) provides output power of 40 kW at the frequency of 240 GHz. Orotrons radiate at frequencies of 100-380 GHz with power of 50-200 mW and high frequency stability. In a LOG, electron-wave interaction at high cyclotron harmonics is more selective than in conventional gyrotrons that allows achieving higher frequencies. Higher output power and higher frequency stability can be obtained in orotrons in comparison with conventional BWOs due to use of open cavities.
Infrared and Millimeter Waves, 2004 and 12th International Conference on Terahertz Electronics, 2004. Conference Digest of the 2004 Joint 29th International Conference on; 01/2004
[Show abstract][Hide abstract] ABSTRACT: Due to high selectivity of open cavity, wider electron beams with higher current can be used in orotron as compared with other Cherenkov devices. It provides important advantages at short millimeter and submillimeter waves. Theory and preliminary experiments in the short part of millimeter and long part of submillimeter wavelength range show that orotron with operating voltage of few kV can generate significantly higher output power than existing BWOs. Combined electronic and mechanical frequency tuning in the band of about of octave has been obtained.
International Journal of Infrared and Millimeter Waves 11/2002; 23(11):1595-1601. DOI:10.1023/A:1020749601248 · 0.67 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Doppler-free two-photon rotational transitions J = 13<--<--11 and J = 12<--<--10 of OCS and J = 8<--<--6 and J = 7<--<--5 of CHF (3) were detected in the frequency range 134-156 GHz, using a novel, highly sensitive intracavity-jet technique. The sub-Doppler narrowing of the observed peaks (down to 40 kHz full width at half maximum as compared to 300 kHz of the Doppler width) demonstrates the potential of this new technique for high precision millimeter wave spectroscopy. The possibilities of the further reduction of the two-photon absorption line widths are considered.
[Show abstract][Hide abstract] ABSTRACT: The design and operation of a gas millimetre-wave spectrometer based on a tunable generator orotron are presented. The absorption cell occupies a part of the high quality (Q approximately=104) orotron Fabry-Perot cavity. The limit of sensitivity gamma min approximately=(3-5)*10-10 cm-1 has been achieved with source frequency modulation at the output band of a receiver of 1 Hz. The narrow spectral width of the orotron radiation (10-15 kHz without locking) provides the Doppler resolution of spectral lines. An absorption signal of gas under investigation is detected by variations of the collector current of the orotron. New results on rotational transition of SiH4 in a vibrational dyad v2/v4 with the absorption coefficient gamma approximately=10-8 cm-1 are briefly given as an illustration of the sensitivity of this spectrometer.
[Show abstract][Hide abstract] ABSTRACT: Mixing of orotron oscillations in the 100-220 GHz range with second and third local-oscillator (LO) harmonics on an electron detector was achieved. The interaction of the LO harmonics with the electron beam was realized by means of an additional periodic structure cut into the flat mirror of the orotron. The mixing signal was registered according to beats of the collector current, and reached 100-200 mV at a load of 10 k-ohms.
[Show abstract][Hide abstract] ABSTRACT: For frequency stabilization, a system of automatic tuning of the resonator by the amplitude criterion was resorted to with the use of "rapid modulation" which was developed for the first time in the VNIIFTRI . The AFC system stabilizes the resonator frequency relative to the value at which the modulation of the resonator's natural frequency (m r = ~0 + A~m) does not cause amplitude modulation of the HG signal. The modulation frequency is selected such that it is much more than the emission line width (~ >> 6s In the design described, resonator frequency modulation is achieved by a changeover diode which closes and opens a loop located on the resonator cover. The depth of modulation of the resonator frequency.
[Show abstract][Hide abstract] ABSTRACT: Results of a theoretical analysis of the density of starting currents of
surface waves in an orotron for different electron-beam voltages and
different periods of the comb-type periodic structure are presented with
reference to the design of backward-wave tubes. Good agreement is found
between the theoretical results and experimental data on the voltage
dependences of the starting currents of orotron oscillations and
surface-wave starting currents. It is concluded that the results
obtained can be used to control the excitation of surface waves in
orotrons and maintain the stable operation of orotrons in the
appropriate high-frequency range.
[Show abstract][Hide abstract] ABSTRACT: A theoretical analysis of the influence of electron-beam shot noise on the frequency stability of an orotron is presented. A formula is obtained for the spectral line width due to the short noise, and a comparison is made with other resonant oscillators. It is shown that the line width due to shot noise for an orotron is three orders of magnitude less than that for klystrons and magnetrons of the same frequency range.