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Sample records for 14-w 140-ghz gyrotron

  1. Operational Characteristics of a 14-W 140-GHz Gyrotron for Dynamic Nuclear Polarization

    Joye, Colin D.; Griffin, Robert G.; Hornstein, Melissa K.; Hu, Kan-Nian; Kreischer, Kenneth E.; Rosay, Melanie; Shapiro, Michael A; Sirigiri, Jagadishwar R.; Temkin, Richard J.; Woskov, Paul P.

    2006-01-01

    The operating characteristics of a 140-GHz 14-W long pulse gyrotron are presented. The device is being used in dynamic nuclear polarization enhanced nuclear magnetic resonance (DNP/NMR) spectroscopy experiments. The gyrotron yields 14 W peak power at 139.65 GHz from the TE(0,3) operating mode using a 12.3-kV 25-mA electron beam. Additionally, up to 12 W peak has been observed in the TE(2,3) mode at 136.90 GHz. A series of mode converters transform the TE(0,3) operating mode to the TE(1,1) mod...

  2. Velocity diagnostics of electron beams within a 140 GHz gyrotron

    Experimental measurements of the average axial velocity vparallel of the electron beam within the M.I.T. 140 GHz MW gyrotron have been performed. The method involves the simultaneous measurement of the radial electrostatic potential of the electron beam Vp and the beam current Ib. Vp is measured through the use of a capacitive probe installed near or within the gyrotron cavity, while Ib is measured with a previously installed Rogowski coil. Three capacitive probes have been designed and built, and two have operated within the gyrotron. The probe results are repeatable and consistent with theory. The measurements of vparallel and calculations of the corresponding transverse to longitudinal beam velocity ratio α = vperpendicular/vparallel at the cavity have been made at various gyrotron operation parameters. These measurements will provide insight into the causes of discrepancies between theoretical rf interaction efficiencies and experimental efficiencies obtained in experiments with the M.I.T. 140 GHz MW gyrotron. The expected values of vparallel and α are determined through the use of a computer code entitled EGUN. EGUN is used to model the cathode and anode regions of the gyrotron and it computes the trajectories and velocities of the electrons within the gyrotron. There is good correlation between the expected and measured values of α at low α, with the expected values from EGUN often falling within the standard errors of the measured values. 10 refs., 29 figs., 2 tabs

  3. 140 GHz gyrotron development program. Quarterly report No. 4, January-March 1985

    The objective of this program is to develop a gyrotron oscillator capable of producing 100 kW CW at 140 GHz. Further analysis of the electron guns, interaction cavity, and beam tunnel designs for the first two experimental tubes, Experimental Tube 1 and preprototype Tube 1, is presented. A window deflection tester has been built and initial deflection test results are given. The first 140 GHz gyrotron magnet has successfully passed the major points in the acceptance test. The detailed results of the magnet acceptance test are discussed. Progress concerning the fabrication of 149 GHz gyrotron components, diagnostics, and protective devices, as well as the status of Experimental Tube 1, are summarized

  4. Design and operation of 140 GHz gyrotron oscillators for power levels up to 1 MW CW

    Jory, H.; Bier, R.; Craig, L.J.; Felch, K.; Ives, L.; Lopez, N.; Spang, S.

    1986-12-01

    Varian has designed and tested 140 GHz gyrotron oscillators that have generated output powers of 100 kW CW and 200 kW for 1 ms pulses. Upcoming tubes will be designed to operate at power levels of 200 kW CW and ultimately up to 1 MW CW. The important design considerations which are addressed in the higher power tubes include the design of the electron gun, interaction circuit, and output window. These issues will be discussed and the results of the earlier 140 GHz gyrotron work at Varian will be summarized.

  5. The 140 GHZ, 1 MW Gyrotron - Status and Recent Results

    Gantenbein, G.; Dammertz, G.; Illy, S.; Kern, S.; Leonhardt, W.; Piosczyk, B.; Schmid, M.; Thumm, M.; Braune, H.; Erckmann, V.; Laqua, H. P.; Michel, G.; Kasparek, W.; Lechte, C.; Legrand, F.; Lievin, C.; Prinz, O.

    2009-04-01

    A 10 MW ECRH system is currently under construction for the stellarator W7-X which will be built up and operated by IPP in Greifswald, Germany. The present status of the complete system is reported in [1]. The RF power will be provided by 10 gyrotrons. A European collaboration has been established to develop and build the 10 gyrotrons each with an output power of 1 MW for continuous wave (CW) operation [2]. Nine gyrotrons are being manufactured by Thales Electron Devices (TED), Vélizy, France, one gyrotron was produced by CPI, Palo Alto, CA and passed the acceptance tests at IPP. The acceptance tests of the TED gyrotrons are performed at the test stand at FZK and on site at IPP. The first series tube yielded a total output power of 0.98 MW, with an efficiency of 31 % (without a single stage depressed collector) in short pulse operation and of 0.92 MW in pulses of 1800 s (efficiency of almost 45 % at a depression voltage of 29 kV) [3], The Gaussian mode output power was 0.91 MW. The RF power, measured in a calorimetric load at the end of a 25 m long quasi-optical transmission line with seven mirrors, was 0.87 MW. In this contribution typical results of the next series gyrotrons will be reported.

  6. Recent operating experience with Varian 70 GHz and 140 GHz gyrotrons

    The design features and initial test results of Varian 70 GHz and 140 GHz CW gyrotrons are presented. The first experimental 140 GHz tube has achieved an output power of 102 kW at 24% efficiency under pulsed conditions in the desired TE0310 cavity mode. Further tests aimed at achieving the design goal of 100 kW CW are currently underway. The 70 GHz tube has achieved an output power of 200 kW under pulsed conditions and possesses a wide dynamic range for output power variations. 6 refs., 8 figs

  7. Installation and operation of the 400 kW 140 GHZ gyrotron on the MTX experiment

    This paper describes the installation and operation of the 400 kW 140 GHz gyrotron used for plasma heating on the Microwave Tokamak Experiment (MTX) at Lawrence Livermore National Laboratory (LLNL). The Varian VGT-8140 gyrotron has operated at a power level of 400 kW for 100 ms in conjunction with MTX plasma shots. The gyrotron system is comprised of a high voltage (- 80 kV) modulated power supply, a multistation CAMAC computer control, a 5-tesla superconducting magnet, a series of conventional copper magnets, a circulating fluorinert (FC75) window cooling system, a circulating oil cooling system, a water cooling system, and microwave frequency and power diagnostics. Additionally, a Vlasov launcher is used to convert the gyrotron TE 15,2 mode to a Gaussian beam. Two versions of the Vlasov launcher have been used on the gyrotron, one version designed by LLNL and one version designed by the Japan Atomic Energy Research Institute (JAERI). The Varian VGT-8140 gyrotron has been installed on the MTX tokamak experiment to provide electron cyclotron resonant heating (ECRH) of the tokamak plasma. The gyrotron has been operated with the tokamak for periods as long as 100 ms at power levels of 400 kW. he gyrotron will also be used as the RF driver for the intense microwave prototype (IMP) wiggler associated with the electron test accelerator (ETA). In this configuration, the IMP wiggler will produce multigigawatt, 140 GHz, 50-ns pulses at a 5-kHz repetition rate. The plasma heating efficiency of the long RF pulse from the gyrotron can then be compared with the higher power but shorter RF pulses from the wiggler. The M2 mirror can be reversed to determine whether the gyrotron microwave beam or the IMP wiggler microwave beam is directed into the MTX tokamak. When the IMP wiggler is in operation, the gyrotron will be used as the master oscillator to drive the wiggler

  8. Experimental results of the 1 MW, 140 GHz, CW gyrotron for W7-X

    A 10 MW ECRH system will be provided by FZK in collaboration with several European associations for the stellarator W7-X. The RF power will be delivered by 10 gyrotrons operating at 140 GHz in CW with 1 MW each. The development of this gyrotron has been performed within a European collaboration in an industrial frame. Two R and D tubes have been built, up to know one serial tube has been passed the acceptance tests. The design of the gyrotron will be described and short pulse and long pulse results of the first serial gyrotron will be discussed. This gyrotron has been successfully operated at more then 900 kW with a pulse length of 30 min. (author)

  9. 140 GHz high-power gyrotron development for the stellarator W7-X

    Electron cyclotron resonance heating (ECRH) has proven to be one of the most attractive heating schemes for stellarators. Therefore, ECRH was chosen to be the main heating method for the Wendelstein 7-X stellarator (W7-X) now under construction at IPP Greifswald, Germany. A 10 MW ECRH system with continuous wave (CW) possibilities, operating at 140 GHz will be built up to meet the scientific goals of the stellarator. Two prototype gyrotrons with an output power of 1 MW were developed in collaboration between European research laboratories and European industry (Thales Electron Devices, France). The gyrotrons are equipped with a single-stage depressed collector, an optimised quasi-optical mode converter and a CVD-diamond window. The prototypes have been successfully tested at FZK. With the second one, an output power of 0.89 MW at a pulse duration of 3 min and an output power of 0.54 MW for about 15 min have been obtained

  10. Installation and operation of the 400 kW 140 GHz gyrotron on the MTX experiment

    This paper describes the installation and operation of the 400 kW 140 GHz gyrotron used for plasma heating on the Microwave Tokamak Experiment (MTX) at Lawrence Livermore National Laboratory (LLNL). The Varian VGT-8140 gyrotron has operated at a power level of 400 kW for 100 ms in conjunction with MTX plasma shots. The gyrotron system is comprised of a high voltage (-80 kV) modulated power supply, a multistation CAMAC computer control, a 5-tesla superconducting magnet, a series of conventional copper magnets, a circulating fluorinert (FC75) window cooling system, a circulating oil cooling system, a water cooling system, and microwave frequency and power diagnostics. Additionally, a Vlasov launcher is used to convert the gyrotron TE 15,2 mode to a Gaussian beam. Two versions of the Vlasov launcher have been used on the gyrotron, one version designed by LLNL and one version designed by the Japan Atomic Energy Research Institute (JAERI). The Gaussian beam from the Vlasov launcher is transported to the MTX tokamak by a series of 5 mirrors in a 35-meter-long, high-efficiency, quasioptical beam transport system. A twist polarizer is built into one of the mirrors to adjust for horizontal polarization in the tokamak. No windows are used between the Vlasov reflector and the MTX tokamak. A laser alignment system is used to perform the initial system alignment. A summary of the design and operating characteristics of each of these systems is included. Also included is a summary of the system operation and performance

  11. Experimental results of the 1 MW, 140 GHz, CW gyrotron for W7-X

    For the stellarator Wendelstein 7-X now under construction at IPP Greifswald, Germany, a 10 MW ECRH system is foreseen. A European collaboration has been established between Forschungszentrum Karlsruhe (FZK), IPP Garching/Greifswald, IPF Stuttgart, CRPP Lausanne, CEA Cadarache and TED Velizy, to develop and build the 10 gyrotrons each with an output power of 1 MW for continuous wave (CW) operation. The dependence of the output power and efficiency of the first series tube versus the beam current will be shown in short pulse operation (without depressed collector) and in CW operation (up to 30 minutes, depressed collector operation). RF-field measurements have been performed in order to characterise the output field of the gyrotron and to minimise losses during the transmission to the W7-X device. Several parameters have been optimised (e.g. beam radii, magnetic field) to maximise output power and efficiency of the tube. At FZK site, long pulse tests up to 180 s have been performed (limited by the available power supply), at IPP site the pulse length could be extended to 30 min, both at a power level of 1 MW and high efficiency. (author)

  12. Gyrotrons

    The purpose of this study is to bring together some relevant ideas and developments in the field of gyrotrons. The development of the electron cyclotron resonance maser (ECRM or Gyrotron) was an important break through in microwave electronics in the 1970s. As we look to the 1980's, we find scientists channelling their collective efforts to shorten the wavelength and increase output power and efficiency, thereby yielding an important device for generating high power microwave radiation. 24 refs

  13. Status of the 140 GHz, 10 MW CW transmission system for ECRH on the stellarator W7-X

    The stellarator W7-X, which is currently under construction at IPP Greifswald, Germany, will be equipped with a 10 MW ECRH system working at 140 GHz in CW regime. The microwave power will be generated by 10 gyrotrons delivering 1 MW each and will be transmitted from the gyrotron hall to the W7-X stellarator ports via a fully optical system. The status of the construction of the transmission lines and the design of the launchers is reported. Low-power tests of a prototype system at IPF Stuttgart are reviewed. Now, the first two gyrotrons are operating at IPP Greifswald, and high-power long-pulse tests have started. Measurements on transmission performance, behaviour of the water-cooled mirrors under thermal and microwave loads as well as alignment issues, characteristics of directional couplers, calorimetric loads, and other diagnostics are discussed

  14. Recent Progress of 2MW 140GHz ECRH System on HL-2A

    Lu Z.H.

    2012-09-01

    Full Text Available In order to provide more capability of physics study for high-performance plasma, such as current profile control, neoclassical tearing modes suppression, transport study and so on, a new 2MW/140GHz/3s second-harmonic ECRH system with X-mode injection is on schedule on HL-2A. The total power of this system is 2MW and the pulse duration is 3 sec, which is generated by two gyrotrons manufactured by GYCOM. Two evacuated Φ63.5mm transmission lines were used to propagate these two 1MW/3s wave beams. A fast steerable launcher has been designed and installed on the HL-2A tokamak to inject four beams with narrow beam width and enable continuous beam scanning in toroidal and poloidal directions independently.

  15. Design of a 140 GHz, 100 W Gyroklystron Amplifier

    Joye, Colin; Shapiro, Michael; Sirigiri, Jagadishwar; Temkin, Richard

    2004-11-01

    We present the design and the simulation results for a 140 GHz, 100 watt CW gyroklystron amplifier for use in Dynamic Nuclear Polarization (DNP) experiments. The amplifier was designed for a 15 kV, 150 mA annular electron beam and simulations show a saturated gain of 36 dB at a pitch factor of 1.5 for the TE02 mode with an efficiency of 6% and output power of 130 watts. The -3dB bandwidth is 1 GHz (0.7%) and 1.2 GHz of bandwidth is available at the 50-watt level. This design is also capable of emitting pulses on the nanosecond scale. The circuit consists of an input cavity, three bunching cavities and an output cavity with a nonlinear uptaper. This project is supported by NIBIB grant #5R01EB1965.

  16. Components for transmission of very high power mm-waves (200 kW at 28, 70 and 140 GHz) in overmoded circular waveguides

    Optimized overmoded circular waveguide components of transmission lines developed for high-power (200 kW) millimeter wave applications at 28, 70 and 140 GHz, as e.g. electron cyclotron resonance heating (ECRH) of plasmas for thermonuclear fusion research with gyrotrons, are described. Axisymmetric, narrow, pencil-like beams with well-defined polarization (HE11 hybrid mode) are used at open-ended corrugated waveguide antennas. The HE11 mode is generated from TEsub(On) gyrotron modes by the two multi-step mode conversion processes: (1) TEsub(On)->TE01->TE11->HE11 or (2) TEsub(On)->TE01->TM11->HE11. This paper reports computer-aided analyses and measurements on mode transducer systems of the first type at 28 and 70 GHz and of the second type at 140 GHz. In all cases the overall efficiency of the complete mode conversion sequence in the desired mode is approximately (92-95)%. The mode purity in the transmission lines is conserved by using corrugated gradual waveguide bends with optimized curvature distribution and diameter tapers with non-linear contours. Highly efficient corrugated-wall mode selective filters decouple the different waveguide sections. Mode content and reflected power are determined by a novel device (k-spectrometer). Absolute power calibration is done with newly developed calorimetric loads using an organic absorbing fluid. (orig.)

  17. Development in Russia of high power gyrotrons for fusion

    Full text: Electron cyclotron systems of fusion installations are based on powerful millimetre wave sources - gyrotrons, which are capable to produce now microwave power up to 1 MW in very long (hundreds of seconds) pulses. The paper presents the latest achievements in development at IAP/GYCOM of MW power level gyrotrons for fusion installations. Among them are a new versions of 170 GHz gyrotron for ITER and multi-frequency (105-140 GHz) gyrotron for Asdex-Up. The gyrotrons are equipped with diamond CVD windows and depressed collectors. The most efforts were spent for development of ITER gyrotron. The tests are carried out at specially prepared test stand in Kurchatov Institute. The following gyrotron output parameters were demonstrated so far in many pulses: 1MW/30 sec and 0.64 MW/300 sec. Also a gyrotron with a higher power -1.5 MW was designed and tested in short pulses. The tests continue. In two tested long-pulse dual-frequency gyrotrons, power in the output Gaussian beam exceeding 0.9MW at 140GHz and 0.7MW at 105GHz was attained at specified 10-s pulse duration. The multi-frequency gyrotron should operate at least at four frequencies in the frequency range 105GHz-140 GHz. Two window concepts for the gyrotron are considered: Brewster window and two-disc adjustable window. Last years significant efforts were done by IAP/GYCOM in order to solve the whole scope of problems associated with the use of CVD diamond windows in gyrotrons: growing of discs, their cutting and polishing, and then high-temperature brazing and mounting to a tube. Two setups for growing diamond discs have been put into operation. The first discs grown at IAP have acceptable mechanical and electrical parameters. The IAP/GYCOM discs have been successfully brazed at near 800 deg. C temperature to metal constructions and tested with high-power gyrotrons. (author)

  18. On the origin of 140 GHz emission from the 4 July 2012 solar flare

    Tsap, Yuriy T.; Smirnova, Victoria V.; Morgachev, Alexander S.; Motorina, Galina G.; Kontar, Eduard P.; Nagnibeda, Valery G.; Strekalova, Polina V.

    2016-04-01

    The sub-THz event observed on the 4 July 2012 with the Bauman Moscow State Technical University Radio Telescope RT-7.5 at 93 and 140 GHz as well as Kislovodsk and Metsähovi radio telescopes, Radio Solar Telescope Network (RSTN), GOES, RHESSI, and SDO orbital stations is analyzed. The spectral flux between 93 and 140 GHz has been observed increasing with frequency. On the basis of the SDO/AIA data the differential emission measure has been calculated. It is shown that the thermal coronal plasma with the temperature above 0.5 MK cannot be responsible for the observed sub-THz flare emission. The non-thermal gyrosynchrotron mechanism can be responsible for the microwave emission near 10 GHz but the observed millimeter spectral characteristics are likely to be produced by the thermal bremsstrahlung emission from plasma with a temperature of about 0.1 MK.

  19. On the origin of 140 GHz emission from the 4 July 2012 solar flare

    Tsap, Yuriy T; Morgachev, Alexander S; Motorina, Galina G; Kontar, Eduard P; Nagnibeda, Valery G; Strekalova, Polina V

    2016-01-01

    The sub-THz event observed on the 4 July 2012 with the Bauman Moscow State Technical University Radio Telescope RT-7.5 at 93 and 140~GHz as well as Kislovodsk and Mets\\"ahovi radio telescopes, Radio Solar Telescope Network (RSTN), GOES, RHESSI, and SDO orbital stations is analyzed. The spectral flux between 93 and 140 GHz has been observed increasing with frequency. On the basis of the SDO/AIA data the differential emission measure has been calculated. It is shown that the thermal coronal plasma with the temperature above 0.5~MK cannot be responsible for the observed sub-THz flare emission. The non-thermal gyrosynchrotron mechanism can be responsible for the microwave emission near $10$~GHz but the observed millimeter spectral characteristics are likely to be produced by the thermal bremsstrahlung emission from plasma with a temperature of about 0.1~MK.

  20. A 140 GHz pulsed EPR/212 MHz NMR spectrometer for DNP studies

    Smith, Albert A.; Corzilius, Björn; Bryant, Jeffrey A.; DeRocher, Ronald; Woskov, Paul P.; Temkin, Richard J.; Griffin, Robert G.

    2012-10-01

    We described a versatile spectrometer designed for the study of dynamic nuclear polarization (DNP) at low temperatures and high fields. The instrument functions both as an NMR spectrometer operating at 212 MHz (1H frequency) with DNP capabilities, and as a pulsed-EPR operating at 140 GHz. A coiled TE011 resonator acts as both an NMR coil and microwave resonator, and a double balanced (1H, 13C) radio frequency circuit greatly stabilizes the NMR performance. A new 140 GHz microwave bridge has also been developed, which utilizes a four-phase network and ELDOR channel at 8.75 GHz, that is then multiplied and mixed to obtain 140 GHz microwave pulses with an output power of 120 mW. Nutation frequencies obtained are as follows: 6 MHz on S = 1/2 electron spins, 100 kHz on 1H, and 50 kHz on 13C. We demonstrate basic EPR, ELDOR, ENDOR, and DNP experiments here. Our solid effect DNP results demonstrate an enhancement of 144 and sensitivity gain of 310 using OX063 trityl at 80 K and an enhancement of 157 and maximum sensitivity gain of 234 using Gd-DOTA at 20 K, which is significantly better performance than previously reported at high fields (⩾3 T).

  1. Results of 170 GHz gyrotron tests

    During the last few years the development of 170 GHz gyrotron for ITER have been under way. Sketchy description of experiment and test results of an improved design gyrotron with a depressed collector, are reported. The analysis of the phenomena causing the destruction of the output window is submitted. The projects for the following experiments are presented. The new 170 GHz/1 MW/50%/CW gyrotron with depressed collector and CVD diamond window was developed by GYCOM. This gyrotron was tested with BN window and then with diamond window. The gyrotron testing showed that practically all ITER requirements are satisfied except of pulse duration limited to that time by brick load arcing. Imperfection of arc protection system gave the possibility for arc-plasma to come to the window and destroy it. New loads have been created and tested at 140 GHz, with output gyrotron power Phf = 820 kW and the pulse duration T = 3.5 s. A new version of protection system has been developed and tested in experiment. The next gyrotron with modified electron gun has been manufactured. After first stage test, BN window will be replaced with new CVD diamond unit, which is assembling now. Testing of this gyrotron is planned to carry out in May 2002. (authors)

  2. Demonstration of a 140-GHz 1-kW Confocal Gyro-Traveling-Wave Amplifier

    Joye, Colin D.; Shapiro, Michael A.; Sirigiri, Jagadishwar R.; Temkin, Richard J.

    2009-01-01

    The theory, design, and experimental results of a wideband 140-GHz 1-kW pulsed gyro-traveling-wave amplifier (gyro-TWA) are presented. The gyro-TWA operates in the HE06 mode of an overmoded quasi-optical waveguide using a gyrating electron beam. The electromagnetic theory, interaction theory, design processes, and experimental procedures are described in detail. At 37.7 kV and a 2.7-A beam current, the experiment has produced over 820 W of peak power with a –3-dB bandwidth of 0.8 GHz and a li...

  3. 140 GHz electron cyclotron resonance heating experiments at the W7-AS stellarator

    Electron cyclotron resonance heating (ECRH) at the W7-AS stellarator is performed with two systems of comparable heating power at 70GHz (0.8MW, 3s) and 140GHz (0.9MW, 0.4s). Experiments with 140GHz open a new parameter window with high density operation up to 1.1x1020m-3. H mode transitions were observed in high density discharges at 2.5T and at lower density at 1.25T. The operational window for the stellarator H mode with emphasis on the density and power threshold and the influence of gas puffing on the H transitions are discussed. Perturbation experiments with modulated ECRH power were performed to determine the heat transport and the power deposition profile. Density control is achieved in combined heating with neutral beam injection (NBI) despite the beam particle fuelling, whereas with NBI alone a steady density rise is observed. The impact of combined heating on the impurity confinement was investigated. Electron cyclotron current drive (ECCD) was studied in different magnetic field configurations and the influence of trapped particles on the ECCD efficiency was examined experimentally and compared with theory. ((orig.))

  4. High-power tests of a remote steering launcher mock-up at 140 GHz

    This paper reports the results of the high-power test of a remote steering launcher mock-up at 140 GHz, which were performed at the ECRH installation for the future stellarator W7-X at IPP Greifswald. The mock-up test system consists of a 6.62 m long corrugated square waveguide with a steerable optic at the entrance and various diagnostics at the exit of the waveguide. A straight and a dog-leg version of the launcher were investigated. The high-power tests of the straight setup have been performed with powers up to P0 = 700 kW (typically 500 kW) and pulse lengths of up to 10 seconds. For both polarizations (parallel and perpendicular to the steering plane), no arcing was observed in spite of the fact, that the experiments were performed under ambient atmospheric conditions. After the integration of 2 mitre bends in the setup, arcing limited the usable parameter range. The ohmic loss Px of the waveguide was measured via the temperature increase of the waveguide wall, and was used to calibrate the calculated angular dependence of the total ohmic losses of the waveguide. Short-pulse radiation pattern measurements with thermographic recording show high beam quality and confirm the steering range of -12 deg. < φ < 12deg

  5. Conditioning optics for astigmatic Gaussian beams at 140 GHz, 0.5 MW

    A quasi-optical system has been designed to couple the power coming from a gyrotron with astigmatic gaussian beam output, into an oversized corrugated waveguide (HE11 mode). The fraction of the power injected in the transmission line can be controlled by means of a wire grid beam splitter. Polarization control is provided by two rotating corrugated mirrors of electrical depth λ/4 and λ/8 respectively

  6. Photonic-Band-Gap Resonator Gyrotron

    We report the design and experimental demonstration of a gyrotron oscillator using a photonic-band-gap (PBG) structure to eliminate mode competition in a highly overmoded resonator. The PBG cavity supports a TE041 -like mode at 140GHz and is designed to have no competing modes over a minimum frequency range δω/ω of 30% about the design mode. Experimental operation of a PBG gyrotron at 68kV and 5A produced 25kW of peak power in the design mode. No other modes were observed over the full predicted operating range about the design mode. PBG cavities show great promise for applications in vacuum electron devices in the millimeter- and submillimeter-wave bands

  7. Electron cyclotron heating at 140 GHZ on FTU tokamak in steady-state conditions and during current ramp-up

    Localized absorption of EC waves at 140 Ghz, 0.7 MW, in FTU is used to shape the current density profile (qa∼6) in a way to affect sawteeth. If absorption is localized near the inversion radius, temporary stabilization occurs. Sawteeth with a small inversion radius (r/a<0.2) do not affect electron energy confinement. Energy transport appears diffusive, and global confinement is found to be in good agreement with ITER89P L-mode scaling law. (author)

  8. Millimeter-wave, megawatt gyrotron development for ECR (electron cyclotron resonance) heating applications

    Jory, H.; Felch, K.; Hess, C.; Huey, H.; Jongewaard, E.; Neilson, J.; Pendleton, R.; Tsirulnikov, M. (Varian Associates, Inc., Palo Alto, CA (USA))

    1990-09-17

    To address the electron cyclotron heating requirements of planned fusion experiments such as the International Thermonuclear Experimental Reactor (ITER) and the Compact Ignition Tokamak (CIT), Varian is developing gyrotrons at frequencies ranging from 100--300 GHz with output power capabilities up to 1 MW CW. Experimental gyrotrons have been built at frequencies between 100--140 GHz, and a study program has addressed the critical elements of designing 280--300 GHz gyrotrons capable of generating CW power levels up to 1 MW. Initial test vehicles at 140 GHz have utilized TE{sub 15,2,1} interaction cavities, and have been designed to generate short-pulse (up to 20 ms) power levels of 1 MW and up to 400 kW CW. Recently, short-pulse power levels of 1040 kW at 38% efficiency have been obtained and average powers of 200 kW have been achieved. Long-pulse operation has been extended to pulse durations of 0.5 seconds at power levels of 400 kW. Gyrotron oscillators capable of generating output powers of 500 kW CW at a frequency of 110 GHz have recently been designed and a prototype is currently being tested. Design work for a 1 MW CW gyrotron at 110 GHz, is in progress. The 1 MW CW tube will employ an output coupling approach where the microwave output is separated from the microwave output. 15 refs., 10 figs., 3 tabs.

  9. Experimental results of series gyrotrons for the stellarator W7-X

    A powerful ECRH system with 10 MW RF power at 140 GHz and CW operation is foreseen for the stellarator W7-X, being under construction at IPP Greifswald. The RF power will be delivered by 10 gyrotrons, each capable of 1 MW, CW. Nine gyrotrons are being manufactured by Thales Electron Devices (TED), Velizy, France, one gyrotron was produced by CPI, Palo Alto, CA. Testing of the TED gyrotrons is performed at the test stand at FZK (pulse duration 3 min) and the final tests are performed at IPP (pulse length 30 min). Both, the first TED series gyrotron and the CPI gyrotron have passed the acceptance tests successfully. The acceptance tests of the TED series gyrotrons are ongoing. The RF output beam quality of all tubes tested so far is at a constant high level of about 97% in the Gaussian beam. In short pulse operation the gyrotrons have achieved the specified parameters. However, for long pulse operation the performance decreases due to the occurrence of parasitic oscillations which are assumed to be excited by the electron beam in the beam tunnel close to the cavity. Experimental results of this effect and possible modifications of the beam tunnel geometry will be discussed. (author)

  10. Gyrotron Development in the EU for Present Fusion Experiments and for ITER

    The long term strategy of the EU in the field of gyrotrons in fusion plasma applications is based on two approaches: R and D in laboratories to develop advanced concepts and industrial development of state-of-the-art tubes for use in present experiments like TCV, Tore Supra (118 GHz, 0.5 MW, CW) and W7-X (140 GHz, 1 MW, CW). The results from these two approaches are then applied to the development of a coaxial cavity gyrotron operating at 170 GHz and delivering 2 MW-CW for the electron cyclotron wave system of ITER. This paper will recall the main achievements of this program and will outline the present status of the 170 GHz coaxial cavity gyrotron development

  11. Optimization of oversized corrugated waveguide bends for higher-order TE0n-modes at 140 GHz

    Oversized corrugated 900 waveguide bends with a waveguide diameter of 27.79 mm were optimized for TE0n (n = 3...6) transmission lines to transmit power of about 200 kW for Electron-Cyclotron-Resonance-Heating of plasmas in thermonuclear fusion research at a frequency of 140 GHz. The corrugation removes the degeneracy of the mode pairs TE0n/TM1n. The bends were optimized by numerical integration of the coupled-mode differential equations for six coupled modes: TE0n, HE1n, EH1n, EH1,n+1, HE2n and EH2n. During the optimization procedure three parameters were varied: curvature distribution, corrugation depth and arc length. Following curvature distributions were studied: sine-sine-squared, triangular and specific Fourier series. The last one was found to be the best. The optimum corrugation depth increases with increasing mode number n, whereas the arc length decreases. It was found, that a small elliptical deformation of less than 0.04 mm has a negligible influence on TE03- and TE04-bends. In the case of TE05- and TE06-bends the arc length must be increased in order to maintain a pure output mode. (orig.)

  12. Investigation of a 140 GHz gryo-backward wave oscillator and a 95 GHz gyro-traveling wave

    There is current interest in developing a high-power source of continuously tunable millimeter wave radiation as a RF driver for high-power gyrotron, CARM, or FEL amplifiers. The gyrotron backward wave oscillator is a voltage-tunable fast-wave device that can satisfy these requirements. This thesis reports on the design and experimental investigation of a 130--145 GHz gyrotron backward wave oscillator Novel operating features of this design include the use of a 80-kV, 6.2-A Pierce-wiggler electron beam source, a broadband motheye window and an overmoded TE1,2 cylindrical interaction waveguide. Although this device has demonstrated voltage-tunable operation over the design range in the TE1,2 mode, the frequency tuning is not continuous, output powers were low and full-beam transmission through the interaction region was not possible. Simulations indicate that the beam has very high velocity spread induced by space charge forces in the compression region. After increasing the diameter of the beam tunnel to achieve full transmission, the TE1,2 was not found. It is felt that the scraping off of the beam edge in the initial experiments allowed a better quality beam to enter the interaction region and inhibited coupling into competing forward wave modes. The need for radar systems with greater resolution has led to renewed interest in the development of efficient high-power amplifiers at 95 GHz. Current sources are limited to 6--8 kW of output power due to ohmic loading on the slow-wave circuit. A gyrotron traveling wave tube amplifier is capable of efficient operation over a wide bandwidth with the added attraction of low ohmic loading on the smooth fast-wave circuit. This thesis reports of the design a 95-GHz gyrotron traveling wave tube amplifier that is capable of high power (125 kW), high gain (38 dB), large bandwidth > 5 GHz and high efficiencies (> 30%)

  13. Design considerations in achieving 1 MW CW operation with a whispering-gallery-mode gyrotron

    Varian is developing high-power, CW gyrotrons at frequencies in the range 100 GHz to 150 GHz, for use in electron cyclotron heating applications. Early test vehicles have utilized a TE15,2,1 interaction cavity, have achieved short-pulse power levels of 820 kW and average power levels of 80 kW at 140 GHz. Present tests are aimed at reaching 400 kW under CW operating conditions and up to 1 MW for short pulse durations. Work is also underway on modifications to the present design that will enable power levels of up to 1 MW CW to be achieved. 7 refs., 2 figs

  14. State-of-the-art and recent developments of high-power gyrotron oscillators

    Thumm, Manfred

    1999-05-01

    Gyrotron oscillators (gyromonotrons) are mainly used as high-power millimeter wave sources for electron cyclotron resonance heating (ECRH) and diagnostics of magnetically confined plasmas for generation of energy by controlled thermonuclear fusion. High unit power and high efficiency single-mode CW gyrotrons with conventional cylindrical (1 MW) and advanced coaxial (2 MW) cavities are worldwide under development. 118 GHz, 140 GHz and 170 GHz conventional cavity gyrotrons with output power Pout≈0.5 MW, pulse length τ≈5.0 s and efficiency η≈35% are commercially available. Advanced internal quasi-optical mode converters generate linearly polarized output wave beams from the high-order cavity modes (e.g., TE22,6) with efficiencies of 90-95% and separate the millimeter-wave beam from the electron beam, thus allowing the use of large CW-relevant depressed collectors for energy recovery. Overall efficiencies between 50 and 60% have been already achieved at JAERI, FZK, and GYCOM employing single-stage depressed collectors (SDC). First successful experiments at FZK employing a broadband Brewster window gave up to 1.5 MW output power at around 50% efficiency (SDC) for all operating mode series in the frequency range from 114 to 166 GHz (frequency tuning in 3.7 GHz steps by variation of the magnetic field strength in the cavity). Gyrotrons with advanced coaxial cavities designed for operation in the TE28,16 and TE31,17 modes at 140 and 165 GHz, respectively, are under development and test at IAP Nizhny Novgorod and FZK Karlsruhe. A maximum output power of 1.7 MW has been measured at 165 GHz with an efficiency of 35.2% (SDC, FZK). Cryogenically edge-cooled single-disk sapphire (T=77 K) and Au-doped silicon (T=230 K) windows as well as CVD-diamond windows with water edge-cooling at room temperature are under investigation in order to solve the window problem. Commercial CVD-diamond disks will easily allow the transmission of 2 MW power level at 170 GHz, CW. Bonding and

  15. State-of-the-art and recent developments of high-power gyrotron oscillators

    Gyrotron oscillators (gyromonotrons) are mainly used as high-power millimeter wave sources for electron cyclotron resonance heating (ECRH) and diagnostics of magnetically confined plasmas for generation of energy by controlled thermonuclear fusion. High unit power and high efficiency single-mode CW gyrotrons with conventional cylindrical (1 MW) and advanced coaxial (2 MW) cavities are worldwide under development. 118 GHz, 140 GHz and 170 GHz conventional cavity gyrotrons with output power Pout≅0.5 MW, pulse length τ≅5.0 s and efficiency η≅35% are commercially available. Advanced internal quasi-optical mode converters generate linearly polarized output wave beams from the high-order cavity modes (e.g., TE22,6) with efficiencies of 90-95% and separate the millimeter-wave beam from the electron beam, thus allowing the use of large CW-relevant depressed collectors for energy recovery. Overall efficiencies between 50 and 60% have been already achieved at JAERI, FZK, and GYCOM employing single-stage depressed collectors (SDC). First successful experiments at FZK employing a broadband Brewster window gave up to 1.5 MW output power at around 50% efficiency (SDC) for all operating mode series in the frequency range from 114 to 166 GHz (frequency tuning in 3.7 GHz steps by variation of the magnetic field strength in the cavity). Gyrotrons with advanced coaxial cavities designed for operation in the TE28,16 and TE31,17 modes at 140 and 165 GHz, respectively, are under development and test at IAP Nizhny Novgorod and FZK Karlsruhe. A maximum output power of 1.7 MW has been measured at 165 GHz with an efficiency of 35.2% (SDC, FZK). Cryogenically edge-cooled single-disk sapphire (T=77 K) and Au-doped silicon (T=230 K) windows as well as CVD-diamond windows with water edge-cooling at room temperature are under investigation in order to solve the window problem. Commercial CVD-diamond disks will easily allow the transmission of 2 MW power level at 170 GHz, CW. Bonding and

  16. Gyrotron: an ECH system component

    The gyrotron, or electron-cyclotron maser, in the form of a gyromonotron, is being developed as a source of millimeter wave energy for fusion plasma heating. The characteristics of this high power, high efficiency electron tube are described in terms of the requirements for the beam power supply system, the mechanical support system, the cooling system, the focusing and tuning magnets, and the waveguide system. Requirements of power level and transmission efficiency dictate the use of oversize waveguide. The implications, both to the user and to the interaction mechanisms in the gyrotron, of the use of oversize waveguide are treated. The effects of variations of various operating parameters upon the gyrotron's power output and stability are also discussed. Data from gyrotron development and system operation are used where appropriate

  17. Design of an ultra-broadband single-disk output window for a frequency step-tunable 1 MW gyrotron

    Output window design is one of the key issues to realize broadband output of a multi-frequency gyrotron. Corresponding to the recent development of a frequency step-tunable 1 MW gyrotron at Forschungszentrum Karlsruhe (FZK), this paper reports about a newly designed ultra-broadband CVD-diamond disk Brewster window. The thickness of the disk and the geometry of the window unit have been optimized to get low power reflection over a broadband incident angle range around the Brewster angle at different operating frequencies. Detailed calculations of mm-wave transmission characteristics for this Brewster window have been performed for all the considered operation modes from TE17,6 at 105 GHz up to TE23,8 at 143 GHz, and for thickness of the disk from 1.5 to 2.0 mm. Calculations show if one prefers to place the low reflection area in the middle of the discussed frequency range (120-130 GHz), the thickness of 1.6 mm is near optimum and its -20 dB bandwidth angle is more than 30o. For operation near 105 and 140 GHz, a 1.9 mm disk is preferable and its -20 dB bandwidth angle is around 30o

  18. Gyrotron oscillators for fusion heating

    Recent experiments have been performed to determine the ultimate power capability of a 28 GHz 200 kW CW gyrotron design. A power output of 342 kW CW was measured in these tests with an efficiency of 37%. Progress in the development of 60 GHz 200 kW pulsed and CW gyrotrons is discussed. An output of 200 kW with 100 msec pulse length has been achieved with the pulsed design

  19. Advances in high power calorimetric matched loads for short pulses and CW gyrotrons

    ) and the CW version at 2 MW, 170 GHz, are described in the paper. High power tests on short-pulse loads have been done using a double frequency gyrotron, 105 GHz/600 kW for 0.5 s and 140 GHz/800 kW for 1 s. Also a method for emulating 2 MW conditions while using 1 MW gyrotron has been applied to test the load to be used for the European 2 MW coaxial cavity gyrotron development programme

  20. Advances in High Power Calorimetric Matched Loads for Short Pulses and CW Gyrotrons

    the CW version at 2 MW, 170 GHz, are described in the paper. High power tests on short-pulse loads have been done using a double frequency gyrotron, 105 GHz/600 kW for 0.5 s and 140 GHz/800 kW for 1 s. Also a method for emulating 2 MW conditions while using 1 MW gyrotron has been applied for testing the load to be used for the European 2 MW coaxial cavity gyrotron development programme. (author)

  1. Systematic Observation of Time-Dependent Phenomena in the RF Output Spectrum of High Power Gyrotrons

    Kern Stefan

    2012-09-01

    Full Text Available At IHM/KIT, high power gyrotrons with conventional cavity (e.g. 1 MW CW at 140 GHz for the stellarator Wendelstein 7-X and coaxial cavity (2 MW shortpulse at 170 GHz for ITER for fusion applications are being developed and verified experimentally. Especially with respect to the problem of parasitic RF oscillations in the beam tunnel of some W7-X tubes, investigations of the gyrotron RF output spectrum have proved to be a valuable source of diagnostic information. Signs of transient effects in millisecond pulses, like frequency switching or intermittent low-frequency modulation, have indicated that truly time-dependent measurements with high frequency resolution and dynamic range could give deeper insight into these phenomena. In this paper, an improved measurement system is presented, which employs a fast oscilloscope as receiver. Shorttime Fourier transform (STFT is applied to the time-domain signal, yielding time-variant spectra with frequency resolutions only limited by acquisition length and STFT segmentation choice. Typical reasonable resolutions are in the range of 100 kHz to 10 MHz with a currently memory-limited maximum acquisition length of 4 ms. A key feature of the system consists in the unambiguity of frequency measurement: The system receives through two parallel channels, each using a harmonic mixer (h = 9 – 12 to convert the signal from RF millimeter wave frequencies (full D-Band, 110 – 170 GHz to IF (0 – 3 GHz. For each IF output signal of each individual mixer, injection side and receiving harmonic are initially not known. Using accordingly determined LO frequencies, this information is retrieved from the redundancy of the channels, yielding unambiguously reconstructed RF spectra with a total span of twice the usable receiver IF bandwidth, up to ≈ 6 GHz in our case. Using the system, which is still being improved continuously, various transient effects like cavity mode switching, parasitic oscillation frequency variation

  2. Systematic Observation of Time-Dependent Phenomena in the RF Output Spectrum of High Power Gyrotrons

    Schlaich, Andreas; Gantenbein, Gerd; Kern, Stefan; Thumm, Manfred

    2012-09-01

    At IHM/KIT, high power gyrotrons with conventional cavity (e.g. 1 MW CW at 140 GHz for the stellarator Wendelstein 7-X) and coaxial cavity (2 MW shortpulse at 170 GHz for ITER) for fusion applications are being developed and verified experimentally. Especially with respect to the problem of parasitic RF oscillations in the beam tunnel of some W7-X tubes, investigations of the gyrotron RF output spectrum have proved to be a valuable source of diagnostic information. Signs of transient effects in millisecond pulses, like frequency switching or intermittent low-frequency modulation, have indicated that truly time-dependent measurements with high frequency resolution and dynamic range could give deeper insight into these phenomena. In this paper, an improved measurement system is presented, which employs a fast oscilloscope as receiver. Shorttime Fourier transform (STFT) is applied to the time-domain signal, yielding time-variant spectra with frequency resolutions only limited by acquisition length and STFT segmentation choice. Typical reasonable resolutions are in the range of 100 kHz to 10 MHz with a currently memory-limited maximum acquisition length of 4 ms. A key feature of the system consists in the unambiguity of frequency measurement: The system receives through two parallel channels, each using a harmonic mixer (h = 9 - 12) to convert the signal from RF millimeter wave frequencies (full D-Band, 110 - 170 GHz) to IF (0 - 3 GHz). For each IF output signal of each individual mixer, injection side and receiving harmonic are initially not known. Using accordingly determined LO frequencies, this information is retrieved from the redundancy of the channels, yielding unambiguously reconstructed RF spectra with a total span of twice the usable receiver IF bandwidth, up to ≈ 6 GHz in our case. Using the system, which is still being improved continuously, various transient effects like cavity mode switching, parasitic oscillation frequency variation, and lowfrequency

  3. Hysteresis and Frequency Tunability of Gyrotrons

    Dumbrajs, O.; Khutoryan, E. M.; Idehara, T.

    2016-06-01

    We present the first devoted theoretical and experimental study of the hysteresis phenomenon in relation to frequency tunability of gyrotrons. In addition, we generalize the theory describing electron tuning of frequency in gyrotrons developed earlier to arbitrary harmonics. It is found that theoretical magnetic and voltage hysteresis loops are about two times larger than experimental loops. In gyrotrons whose cavities have high quality factors, hysteresis allows one only little to broaden the frequency tunability range.

  4. Matched calorimetric loads for high power, long pulse millimeter-wave gyrotrons

    A compact matched load for high power gyrotron testing in ECRH plants for fusion research applications is in development, with the main goal of providing reflection-free absorption and fast calorimetric measurement of the millimeter-wave power, also at long pulse duration. It is based on the results of the tests at full power and pulse length (140 GHz, 0.5 MW, 0.5 s) on similar loads installed on the ECRH plant of the FTU Tokamak in Frascati. Basically, the load is made of an integrating sphere in copper, with the inner wall covered by plasma spray with a mixture of lossy ceramics, providing an average wall reflectivity in the order of 40%. Absorbing material degradation, small-scale and large-scale damage patterns, caused by fatigue and long-term exposure to high power mm-wave, have been analyzed in detail, with the aim of improving the performances in terms of power handling capability and energy extraction efficiency. Physical-chemical analyses, performed on the original and on the degraded absorbing material, showed the effects of the mm-wave exposure. Damage patterns were recognized as interference of multiple reflections inside the load, with radiation accumulation close to the entrance port, as confirmed by a detailed numerical analysis. Increase in power and energy deposition capabilities require improvements of the present design in different areas: - strategies for the mitigation of the different causes of non-homogeneous deposition; - use of different plasma-sprayed materials as mm-wave absorbers; - improved cooling channel geometry with increased heat transfer rate to the cooling medium, for achieving 1 MW-CW power capability. (authors)

  5. Analytic theory of the gyrotron

    An analytic theory is derived for a gyrotron operating in the linear gain regime. The gyrotron is a coherent source of microwave and millimeter wave radiation based on an electron beam emitting at cyclotron resonance Ω in a strong, uniform magnetic field. Relativistic equations of motion and first order perturbation theory are used. Results are obtained in both laboratory and normalized variables. An expression for cavity threshold gain is derived in the linear regime. An analytic expression for the electron phase angle in momentum space shows that the effect of the RF field is to form bunches that are equal to the unperturbed transit phase plus a correction term which varies as the sine of the input phase angle. The expression for the phase angle is plotted and bunching effects in and out of phase (0 and -π) with respect to the RF field are evident for detunings leading to gain and absorption, respectively. For exact resonance, field frequency ω = Ω, a bunch also forms at a phase of -π/2. This beam yields the same energy exchange with the RF field as an unbunched, (nonrelativistic) beam. 6 refs., 10 figs

  6. Gyrotrons for fusion. Status and prospects

    Gyrotrons are the most advanced high-power sources of millimeter wavelength radiation. They have been used for many years in electron-cyclotron-wave (ECW) systems of many existing fusion installations. Typically modern gyrotrons produce power of 0.5...0.8 MW in pulses of 2-3 seconds, or lower power in longer pulses (e.g. 300-400 kW in pulses up to 10-15 seconds). For the next generation of fusion installations, such as ITER or W7-X the ECW systems based on gyrotrons capable to produce 1MW/CW radiation are considered. Definitely, such gyrotrons with enhanced performance are very interesting also for the use also at existing installations

  7. A review on the sub-THz/THz gyrotrons

    Kumar, Nitin; Singh, Udaybir; Bera, Anirban; Sinha, A. K.

    2016-05-01

    A review on the sub-THz/THz gyrotrons is performed in this manuscript. The present development status of gyrotrons can be divided into three streams for the sake of better understanding: 1. low frequency (200 GHz) gyrotrons for various innovative applications. In this manuscript, the third stream of gyrotron development is reviewed. In last few decades several innovative applications are searched in sub-THz/THz band where the gyrotrons could be used as an efficient source of RF radiation. The applications of sub-THz/THz gyrotrons including the futuristic scope of the device are also discussed in this article. Further, several criticalities arise in the design and development when the gyrotron operation shifts toward the high frequency band. Various such design and technological challenges are also discussed here. Finally the development status of sub-THz/THz gyrotrons as per the use in various scientific and technological applications is also discussed.

  8. Recent result of gyrotron operation in NIFS

    Ito Satoshi

    2015-01-01

    Full Text Available In the last Large Helical Device (LHD experimental campaign, a 154GHz gyrotron which had been conditioned to generate 1 MW/2 s, 0.5 MW/CW was installed for LHD experiments. Four high power gyrotrons (three-77 GHz/1~1.5 MW and one-154 GHz/1 MW and a CW gyrotron (84 GHz/0.2 MW are ready. Our experiment requires high energy and various injection patterns for Electron Cyclotron Resonance Heating (ECRH. Higher individual injection power and various injection patterns, we developed a power enhancement method by stepped anode acceleration voltage control and operated the gyrotron in the hard excitation region. These operations were realized by a remote controlled waveform generator. However the oscillation map of high power or long pulse operation in the hard excitation region were limited because in order to achieve the hard excitation region by the anode voltage control one must pass through the high anode current phase within a time short enough that the anode or the anode power supply is not overloaded. This limitation becomes more critical when the gyrotron beam current is increased in order to increase the output power. In the long pulse operation it was impossible to reach the hard excitation region in a low beam current (<10A.

  9. The 110 GHz Gyrotron System on DIII-D: Gyrotron Tests and Physics Results

    The DIII-D tokamak has installed a system with three gyrotrons at the 1 MW level operating at 110 GHz. Physics experiments on electron cyclotron current drive, heating, and transport have been performed. Good efficiency has been achieved both for on-axis and off-axis current drive with relevance for control of the current density profile leading to advanced regimes of tokamak operation, although there is a difference between off-axis ECCD efficiency inside and outside the magnetic axis. Heating efficiency is excellent and electron temperatures up to 10 keV have been achieved. The gyrotron system is versatile, with poloidal scan and control of the polarization of the injected rf beam. Phase correcting mirrors form a Gaussian beam and focus it into the waveguide. Both perpendicular and oblique launch into the tokamak have been used. Three different gyrotron designs are installed and therefore unique problems specific to each have been encountered, including parasitic oscillations, mode hops during modulation and polarization control problems. Two of the gyrotrons suffered damage during operations, one due to filament failure and one due to a vacuum leak. The repairs and subsequent testing will be described. The transmission system uses evacuated, windowless waveguide and the three gyrotrons have output windows of three different materials. One gyrotron uses a diamond window and generates a Gaussian beam directly. The development of the system and specific tests and results from each of the gyrotrons will be presented. The DIII-D project has committed to an upgrade of the system, which will add three gyrotrons in the 1 MW class, all using diamond output windows, to permit operation at up to ten seconds per pulse at one megawatt output for each gyrotron

  10. Linear theory of frequency pulling in gyrotrons

    Nusinovich, Gregory S.; Luo, Li; Liu, Pu-kun

    2016-05-01

    The effect of the electron beam on the gyrotron operating frequency (the frequency pulling) is studied analytically in the framework of the linear (or small-signal) theory. The theory is applicable for gyrotrons operating at any cyclotron harmonics and in modes with arbitrary axial structures. The present consideration is limited to cases of operation at the fundamental cyclotron resonance and the second harmonic; also two specific axial profiles of the resonator modes are analyzed: the constant and the sinusoidal distributions. In the case of the sinusoidal distribution, we considered the operation in modes with one, two, and three axial variations. It is shown how to use the theory developed for analyzing the frequency tunability due to the frequency pulling effect in a gyrotron with specified parameters of the electron beam.

  11. Compact, harmonic multiplying gyrotron amplifiers

    Guo, H.Z.; Granatstein, V.L.; Antonsen, T.M. Jr.; Levush, B.; Tate, J.; Chen, S.H. [Univ. of Maryland, College Park, MD (United States). Inst. for Plasma Research

    1995-12-31

    A compact, harmonic multiplying gyrotron traveling wave amplifier is being developed. The device is a three-stage tube with the output section running as a fourth harmonic gyro-TWT, the input section running as a fundamental gyro-TWT, and the middle operating at the second harmonic of the cyclotron frequency. Radiation is suppressed by servers between the sections. The operating beam of the tube is produced by a magnetron injection gun (MIG). A TE{sub 0n} mode selective interaction circuit consisting of mode converters and a filter waveguide is employed for both input and output sections to solve the mode competition problem, which is pervasive in gyro-TWT operation. The input section has an input coupler designed as a TE{sub 0n} mode launcher. It excites a signal at the fundamental cyclotron frequency (17.5 GHz), which is amplified in the first TWT interaction region. So far the device is similar to a two-stage harmonic gyro-TWT. The distinction is that in the three-stage device the second section will be optimized not for output power but for fourth harmonic bunching of the beam. A gyroklystron amplifier has also been designed. The configuration is similar to the gyro-TWT but with the traveling wave interaction structures replaced by mode selective special complex cavities. Cold test results of the wideband input coupler and the TE{sub 0n} mode selective interaction circuit have been obtained.

  12. Electron beam instabilities in gyrotron beam tunnels

    Electron beam instabilities occurring in a gyrotron electron beam can induce an energy spread which might significantly deteriorate the gyrotron efficiency. Three types of instabilities are considered to explain the important discrepancy found between the theoretical and experimental efficiency in the case of quasi-optical gyrotrons (QOG): the electron cyclotron maser instability, the Bernstein instability and the Langmuir instability. The low magnetic field gradient in drift tubes of QOG makes that the electron cyclotron maser instability can develop in the drift tube at very low electron beam currents. Experimental measurements show that with a proper choice of absorbing structures in the beam tunnel, this instability can be suppressed. At high beam currents, the electrostatic Bernstein instability can induce a significant energy spread at the entrance of the interaction region. The induced energy spread scales approximately linearly with the electron beam density and for QOG one observes that the beam density is significantly higher than the beam density of an equivalent cylindrical cavity gyrotron. (author) figs., tabs., refs

  13. Recent achievements on tests of series gyrotrons for W7-X and planned extension at the KIT gyrotron test facility

    Schmid, M., E-mail: martin.schmid@kit.edu [Karlsruhe Institute of Technology, Association EURATOM-KIT, Karlsruhe (Germany); Institute for Pulsed Power and Microwave Technology (IHM) (Germany); Choudhury, A. Roy; Dammertz, G. [Karlsruhe Institute of Technology, Association EURATOM-KIT, Karlsruhe (Germany); Institute for Pulsed Power and Microwave Technology (IHM) (Germany); Erckmann, V. [Karlsruhe Institute of Technology, Association EURATOM-KIT, Karlsruhe (Germany); Max-Planck-Institute for Plasmaphysics, Association EURATOM-IPP, Greifswald (Germany); Gantenbein, G.; Illy, S. [Karlsruhe Institute of Technology, Association EURATOM-KIT, Karlsruhe (Germany); Institute for Pulsed Power and Microwave Technology (IHM) (Germany); Jelonnek, J. [Karlsruhe Institute of Technology, Association EURATOM-KIT, Karlsruhe (Germany); Institute for Pulsed Power and Microwave Technology (IHM) (Germany); Institute of High Frequency Techniques and Electronics (IHE) (Germany); Kern, S. [Karlsruhe Institute of Technology, Association EURATOM-KIT, Karlsruhe (Germany); Institute for Pulsed Power and Microwave Technology (IHM) (Germany); Legrand, F. [Karlsruhe Institute of Technology, Association EURATOM-KIT, Karlsruhe (Germany); Thales Electron Devices, Vélicy (France); Rzesnicki, T.; Samartsev, A. [Karlsruhe Institute of Technology, Association EURATOM-KIT, Karlsruhe (Germany); Institute for Pulsed Power and Microwave Technology (IHM) (Germany); Schlaich, A.; Thumm, M. [Karlsruhe Institute of Technology, Association EURATOM-KIT, Karlsruhe (Germany); Institute for Pulsed Power and Microwave Technology (IHM) (Germany); Institute of High Frequency Techniques and Electronics (IHE) (Germany)

    2013-10-15

    Highlights: ► Solution found to suppress parasitic beam tunnel oscillations on high power gyrotrons. ► Electron beam sweeping technique to avoid plastic deformation on collector of high power gyrotrons. ► Ongoing investigations on limitations of gyrotron efficiency. ► Upgrade of 10 MW CW modulator for gyrotrons with multistage depressed collectors. -- Abstract: Parasitic beam tunnel oscillations have been hampering the series production of gyrotrons for W7-X. This problem has now been overcome thanks to the introduction of a specially corrugated beam tunnel. Two gyrotrons equipped with the new beam tunnel have fully passed the acceptance tests. Despite excellent power capability, the expected efficiency has not yet been achieved, possibly due to the presence of parasitic oscillations suspected to be dynamic after-cavity-oscillations (ACI's) or due to insufficient electron beam quality. Both theoretical and experimental investigations on these topics are ongoing. On previous W7-X gyrotrons collector fatigue has been observed, not (yet) leading to any failures so far. The plastic deformation occurring on the collector has now been eliminated due to the strict use (on all gyrotrons) of a sweeping method which combines the conventional 7 Hz solenoid sweeping technique with a 50 Hz transverse-field sweep system. Starting in 2013, the gyrotron test facility at KIT will be enhanced, chiefly with a new 10 MW DC modulator, capable of testing gyrotrons up to 4 MW CW output power with multi-stage-depressed collectors.

  14. Recent achievements on tests of series gyrotrons for W7-X and planned extension at the KIT gyrotron test facility

    Highlights: ► Solution found to suppress parasitic beam tunnel oscillations on high power gyrotrons. ► Electron beam sweeping technique to avoid plastic deformation on collector of high power gyrotrons. ► Ongoing investigations on limitations of gyrotron efficiency. ► Upgrade of 10 MW CW modulator for gyrotrons with multistage depressed collectors. -- Abstract: Parasitic beam tunnel oscillations have been hampering the series production of gyrotrons for W7-X. This problem has now been overcome thanks to the introduction of a specially corrugated beam tunnel. Two gyrotrons equipped with the new beam tunnel have fully passed the acceptance tests. Despite excellent power capability, the expected efficiency has not yet been achieved, possibly due to the presence of parasitic oscillations suspected to be dynamic after-cavity-oscillations (ACI's) or due to insufficient electron beam quality. Both theoretical and experimental investigations on these topics are ongoing. On previous W7-X gyrotrons collector fatigue has been observed, not (yet) leading to any failures so far. The plastic deformation occurring on the collector has now been eliminated due to the strict use (on all gyrotrons) of a sweeping method which combines the conventional 7 Hz solenoid sweeping technique with a 50 Hz transverse-field sweep system. Starting in 2013, the gyrotron test facility at KIT will be enhanced, chiefly with a new 10 MW DC modulator, capable of testing gyrotrons up to 4 MW CW output power with multi-stage-depressed collectors

  15. 100 GHz, 1 MW, CW gyrotron study program. Final report

    The results of a study program to investigate the feasibility of various approaches in designing a 100 GHz, 1 MW CW gyrotron are presented. A summary is given of the possible configurations for a high average power, high frequency gyrotron, including an historical survey of experimental results which are relevant to the various approaches. A set of basic scaling considerations which enable qualitative comparisons between particular gyrotron interaction circuits is presented. These calculations are important in understanding the role of various electron beam and circuit parameters in achieving a viable gyrotron design. Following these scaling exercises, a series of design calculations is presented for a possible approach in achieving 100 GHz, 1 MW CW. These calculations include analyses of the electron gun and interaction circuit parts of the gyrotron, and a general analysis of other aspects of a high average power, high frequency gyrotron. Scalability of important aspects of the design to other frequencies is also discussed, as well as key technology issues

  16. Development of high power long pulse gyrotron for ITER

    A development of 170GHz gyrotron has been carried out as a task of ITER/EDA, and remarkable progress was obtained. Critical issues on the gyrotron development; low efficiency, high heat load at the resonator, window problem, have been solved by breakthroughs; a depressed collector, 1MW single mode oscillation with a high order mode TE31,8, and development of the diamond window gyrotron, respectively. The prototype ITER gyrotron which integrated these technologies were fabricated and tested. Up to now, the power output of 0.45MW, 8sec has been obtained with a diamond window gyrotron. These results give a clear prospect of the 1MW/CW 170GHz gyrotron. (author)

  17. Gyrotron electromagnetic wiggler for a compact free electron laser

    We have demonstrated a novel, high power (≥1 MW), short wavelength (2 mm) gyrotron electromagnetic (GEM) wiggler for use in a compact free electron laser (FEL). The gyrotron consisted of an electron gun and resonator section followed by a special high Q cavity for storing the power created in the gyrotron resonator. The electromagnetic field stored in the high Q cavity would then be appropriate for use as a wiggler field in an infrared or visible FEL with a moderate energy (4 to 10 MeV) electron beam. The gyrotron experiment tested the practical limits due to ohmic loss, mode conversion, etc. on the strength of such a stored field. It also tested the effect of strong feedback from the high Q cavity back onto the gyrotron resonator. The proposed research utilized the technology of high power, high frequency gyrotrons developed at M.I.T. as part of the Department of Energy program on development of sources for plasma heating

  18. Theory and Modeling of High-Power Gyrotrons

    Nusinovich, Gregory Semeon [Univ. of Maryland, College Park, MD (United States)

    2016-04-29

    This report summarized results of the work performed at the Institute for Research in Electronics and Applied Physics of the University of Maryland (College Park, MD) in the framework of the DOE Grant “Theory and Modeling of High-Power Gyrotrons”. The report covers the work performed in 2011-2014. The research work was performed in three directions: - possibilities of stable gyrotron operation in very high-order modes offering the output power exceeding 1 MW level in long-pulse/continuous-wave regimes, - effect of small imperfections in gyrotron fabrication and alignment on the gyrotron efficiency and operation, - some issues in physics of beam-wave interaction in gyrotrons.

  19. High harmonic terahertz confocal gyrotron with nonuniform electron beam

    Fu, Wenjie; Guan, Xiaotong; Yan, Yang [THz Research Center, School of Physical Electronics, University of Electronic Science and Technology of China, Chengdu 610054 (China)

    2016-01-15

    The harmonic confocal gyrotron with nonuniform electron beam is proposed in this paper in order to develop compact and high power terahertz radiation source. A 0.56 THz third harmonic confocal gyrotron with a dual arc section nonuniform electron beam has been designed and investigated. The studies show that confocal cavity has extremely low mode density, and has great advantage to operate at high harmonic. Nonuniform electron beam is an approach to improve output power and interaction efficiency of confocal gyrotron. A dual arc beam magnetron injection gun for designed confocal gyrotron has been developed and presented in this paper.

  20. High harmonic terahertz confocal gyrotron with nonuniform electron beam

    The harmonic confocal gyrotron with nonuniform electron beam is proposed in this paper in order to develop compact and high power terahertz radiation source. A 0.56 THz third harmonic confocal gyrotron with a dual arc section nonuniform electron beam has been designed and investigated. The studies show that confocal cavity has extremely low mode density, and has great advantage to operate at high harmonic. Nonuniform electron beam is an approach to improve output power and interaction efficiency of confocal gyrotron. A dual arc beam magnetron injection gun for designed confocal gyrotron has been developed and presented in this paper

  1. 28 GHz Gyrotron ECRH Upgrade for LDX

    Michael, P. C.; Woskov, P. P.; Ellsworth, J. L.; Kesner, J.; Garnier, D. T.; Mauel, M. E.; Ellis, R. F.

    2009-11-01

    A 10 kW, CW, 28 GHz gyrotron is being implemented on LDX to increase the plasma density and to more fully explore the potential of high beta plasma stability in a dipole magnetic configuration. Higher density increases the heating of ions by thermal equilibration and allows for improved wave propagation in planned ICRF experiments. This represents over a 50% increase in the 17 kW ECRH from sources at 2.45, 6.4, and 10.5 GHz. The higher frequency will also make possible access to plasma densities of up to 10^13 cm-3. The 1 Tesla resonances are located above and below the floating coil near the dipole axial region. The gyrotron beam will be transmitted in TE01 mode in 32.5 mm diameter guide using one 90 bend and a short Tesla resonance region. A layout of the planned system will be presented.

  2. Design of Single disc RF window for High Power Gyrotron

    In this paper investigates the design of water edge cooled single-disc CVD-diamond window for 120 GHz, 1MW gyrotron. The design of RF window for 120 GHz, 1MW gyrotron has been carried out using the CST microwave studio. In 120 GHz gyrotron single disc of diameter 90 mm and thickness 2.0 mm CVD diamond window has been used in the simulation. The return loss (S11) and transmission loss (S21) of the 120 GHz gyrotron window have been found - 40.0 dB and -0.02 dB respectively. Thermal analysis of single disc rf window has also been carried out using ANSYS software for high power 120 GHz gyrotron. The temperature range on the disc surface has been found to be 100 °C - 300 ° C.

  3. A high-order particle-in-cell method for low density plasma flow and the simulation of gyrotron resonator devices

    of its huge computational demand and the thereby resulting long calculation time. Using the presented high-order discontinuous Galerkin Particle-in-Cell scheme on high-performance-computers, this thesis demonstrates for the first time that full-wave and transient research- and design-simulations of gyrotron resonators with high mode-indices can be efficiently performed. For benchmark issues the developed discontinuous Galerkin Particle-in-Cell scheme is verified with a 30 GHz resonant cavity and the results are compared to the SELFT code, which is a state-of-the-art design code for resonators. The discontinuous Galerkin Particle-in-Cell scheme is used to simulate the resonator of the 1 MW, 140 GHz, TE(28,8)-mode gyrotron, used for plasma heating of the Wendelstein 7-X fusion-reactor. Due to the huge number of degrees of freedom and particles, this type of simulation can only be performed on high-performance-computers with enough memory and computational power. Hence, the discontinuous Galerkin Particle-in-Cell code is improved by a new parallelization approach for the high-order shape-function deposition method on unstructured grids, allowing for a high-order coupling between the particles and the electromagnetic field. To further improve the discontinuous Galerkin Particle-in-Cell code, a multi-rate time-stepping method, based on an Adams-Bashforth approach, for the hyperbolic divergence cleaning is developed and verified. This new approach considers the different time scales occurring in the hyperbolic divergence cleaning allowing for a more efficient time-stepping-algorithm then standard time-stepping-schemes. A rule for the construction of arbitrary-order multi-rate time-stepping methods has been derived. The presented simulations provide new physical insights to the complex particle-field-interaction appearing in gyrotrons. The discontinuous Galerkin Particle-in-Cell scheme can be used to analyse transient phenomena, such as beam-miss-alignment, mode competition

  4. Feasibility of a dual regime gyrotron

    The design concept of a 42/84 GHz, 500 kW, CW, dual-regime gyrotron for ECRH of plasma in an experimental Tokamak will be presented in this paper. Operation at 42 GHz is fundamental where as that in 84 GHz will be second harmonic so that a similar guidance system will be retained for dual regime operation. In this paper, the mode competition and mode selection procedures are presented for such a dual regime operation. Cold cavity design and self-consistent calculations will be carried out for power and efficiencies. (author)

  5. Development of submillimeter wave source Gyrotron FU Series for plasma diagnostics

    Our gyrotrons developed in Fukui University (FU), Research Center for Development of Far Infrared Region are high frequency, medium power gyrotrons and are used as millimeter to submillimeter wave radiation sources for application to new far-infrared technologies including plasma diagnostics. We have already developed Gyrotron FU Series which consists of 8 gyrotrons. The gyrotron series has achieved frequency tunability in wide range (from 38 GHz to 889 GHz). The highest frequency is corresponding to a wavelength of 337 μm. This is a current record for high frequency operation of gyrotron. Recently, we have developed a high harmonic gyrotron with an axis-encircling electron beam and a THz gyrotron with a pulse magnet. In this presentation, the present status of Gyrotron FU Series is described. (authors)

  6. 28 GHz Gyrotron ECRH on LDX

    Woskov, P. P.; Kesner, J.; Michael, P. C.; Garnier, D. T.; Mauel, M. E.

    2010-12-01

    A 10 kW, CW, 28 GHz gyrotron has been implemented on LDX to increase the plasma density and to more fully explore the potential of high beta plasma stability in a dipole magnetic configuration. This added power represents about a 60% increase in ECRH to a new total of 26.9 kW with sources at 2.45, 6.4, and 10.5 GHz. The 1 Tesla resonances in LDX form small rings encompassing the entire plasma cross-section above and below the floating coil (F-coil) near the dipole axial region. A 32.5 mm diameter TE01 waveguide with a partial Vlasov step cut launches a diverging beam from above the F-coil that depends on internal wall reflections for plasma coupling. Initial gyrotron only plasmas exhibit steep natural profiles with fewer hot electrons than with the other sources. The background scattered radiation suggests that only about half the power is being absorbed with the present launcher.

  7. Submillimeter-wave harmonic gyrotron experiment

    A theoretical and experimental investigation of the operation at submillimeter wavelengths of a harmonic gyrotron is reported. Using a waveguide cavity with an iris at the output end of the straight section, 14 different second-harmonic modes were observed with frequencies of 301--503 GHz, output powers of 1-22 kW, and a 12-MHz emission frequency bandwidth. The highest output power was 22 kW, with a total efficiency of 3.5% at 467 GHz, and an output power of 15 kW with a 6% efficiency was obtained at 417 GHz. Research was conducted using a 65--75 kV up to 10-A electron gun with 1--1.5 μs pulse-length and a 4-Hz repetition rate, which produced a helical electron beam in magnetic fields of up to 14 T. These results represent the first operation of a high-power harmonic gyrotron in the submillimeter region

  8. Quasi-optical gyrotron: present status and future prospect

    A review of the main experiments on quasi-optical gyrotron is presented. Methods to improve the efficiency (pencil beam electron gun and depressed collector) will be discussed. (author) 5 figs., 1 tab., 10 refs

  9. Technical developments at the KIT gyrotron test facility

    Parasitic beam tunnel oscillations have been discovered on some of the series production gyrotrons for W7-X and also on the coaxial pre-prototype gyrotron for ITER. Solutions to remedy these problems have resulted in a modified beam tunnel design, technologically close to the existing beam tunnel. The new design has successfully been tested on both the coaxial and also the f-step-tunable gyrotrons and has subsequently been implemented on one of the W7-X series-production-tubes presently undergoing factory acceptance tests in Karlsruhe. The ECRH test loads at KIT are operated under normal atmospheric conditions. Several loads have eventually failed in 1 MW long pulse experiments and KIT has therefore started to design its own loads. The first KIT-load is based on a fixed conical mirror and an aluminum cylinder coated with a lossy material for increased absorption. The new load has so far successfully been used during the acceptance tests of two 1-MW CW gyrotrons. Nevertheless a new load based on pure (uncoated) stainless steel absorbers is being developed as a backup solution for the ongoing high priority gyrotron testing. A superconducting magnet capable of rapid field changes between 4.15 and 5.67 T for frequency step-tunable gyrotrons has been procured, has demonstrated a (static) field of 7.2 T and its capability of rapid field-changes.

  10. Technical developments at the KIT gyrotron test facility

    Schmid, Martin, E-mail: martin.schmid@kit.edu [Institute for Pulsed Power and Microwave Technology (IHM), Karlsruhe Institute of Technology, Association EURATOM-KIT, Karlsruhe (Germany); Erckmann, Volker [Max-Planck-Institute for Plasmaphysics, Association EURATOM-IPP, Greifswald (Germany); Gantenbein, Gerd; Illy, Stefan; Kern, Stefan [Institute for Pulsed Power and Microwave Technology (IHM), Karlsruhe Institute of Technology, Association EURATOM-KIT, Karlsruhe (Germany); Lievin, Christophe [Thales Electron Devices, Velicy (France); Samartsev, Andrey [Institute for Pulsed Power and Microwave Technology (IHM), Karlsruhe Institute of Technology, Association EURATOM-KIT, Karlsruhe (Germany); Schlaich, Andreas [Institute of High Frequency Techniques and Electronics (IHE), Karlsruhe Institute of Technology, Association EURATOM-KIT, Karlsruhe (Germany); Rzesnicki, Thomaz [Institute for Pulsed Power and Microwave Technology (IHM), Karlsruhe Institute of Technology, Association EURATOM-KIT, Karlsruhe (Germany); Thumm, Manfred [Institute for Pulsed Power and Microwave Technology (IHM), Karlsruhe Institute of Technology, Association EURATOM-KIT, Karlsruhe (Germany); Institute of High Frequency Techniques and Electronics (IHE), Karlsruhe Institute of Technology, Association EURATOM-KIT, Karlsruhe (Germany)

    2011-10-15

    Parasitic beam tunnel oscillations have been discovered on some of the series production gyrotrons for W7-X and also on the coaxial pre-prototype gyrotron for ITER. Solutions to remedy these problems have resulted in a modified beam tunnel design, technologically close to the existing beam tunnel. The new design has successfully been tested on both the coaxial and also the f-step-tunable gyrotrons and has subsequently been implemented on one of the W7-X series-production-tubes presently undergoing factory acceptance tests in Karlsruhe. The ECRH test loads at KIT are operated under normal atmospheric conditions. Several loads have eventually failed in 1 MW long pulse experiments and KIT has therefore started to design its own loads. The first KIT-load is based on a fixed conical mirror and an aluminum cylinder coated with a lossy material for increased absorption. The new load has so far successfully been used during the acceptance tests of two 1-MW CW gyrotrons. Nevertheless a new load based on pure (uncoated) stainless steel absorbers is being developed as a backup solution for the ongoing high priority gyrotron testing. A superconducting magnet capable of rapid field changes between 4.15 and 5.67 T for frequency step-tunable gyrotrons has been procured, has demonstrated a (static) field of 7.2 T and its capability of rapid field-changes.

  11. A simple quantum-electronic approach to the Gyrotron and its application to the solid-state gyrotron

    Ho, P.-T.; Granatstein, V. L.

    1986-01-01

    A simple, unifying theory of the gyrotron is presented. It is of the Lamb type. Within its framework, important results from different approaches can be easily obtained. As an application, gyrotron action in InSb is reexamined, and coherent emission at 10 to the 12th Hz appears possible with an output power of about 0.5 mW/sq mm of the device.

  12. Efficiency optimization for quasi-optical gyrotrons

    Optimization studies for resonator cavities of quasi-optical gyrotrons have been carried out. With the constraint that the RF field is limited by peak power load on the mirrors, the electronic efficiency can have a value of up to 10% higher than the confocal results by using spherical mirrors with g=1-d/R close to -1. Optimized nonspherical cavities yield similar results. When output coupling through circular slots is considered, confocal (g=0) as well as more extreme designs near the resonator stability boundary are less favorable and the optimum configurations found are spherical mirrors with g-factors of about -0.3, -0.6, and possibly -0.75. (author) 16 figs., 1 tab., 8 refs

  13. Gyrotrons for magnetic fusion applications at 110 GHz and 170 GHz

    Cahalan P.

    2012-09-01

    Full Text Available Two megawatt-class gyrotrons at frequencies of 110 GHz and 170 GHz have recently been fabricated at CPI. The 110 GHz gyrotron is designed to produce 1.2 MW of output power for 10-second pulses, and will be used for electron cyclotron heating and current drive on the DIII-D tokamak at General Atomics. This gyrotron has completed factory testing and has been delivered to General Atomics for installation and additional testing. The 170 GHz gyrotron, though specified as a 500 kW CW system, has been designed with the goal of generating up to 1 MW CW. Oak Ridge National Laboratory will use this gyrotron in ITER ECH transmission line testing. This gyrotron has been fabricated and is awaiting factory testing, Design features of each gyrotron are described, and test data for the 110 GHz gyrotron are presented.

  14. Quasi-optical harmonic gyrotron and gyroklystron

    A method and apparatus for suppressing lower order cyclotron harmonics in order to permit resonance within a quasi-optical gyrotron/gyroklystron configuration of a desired higher order harmonic. In the gyrotron/gyroklystron configuration at least one open resonator defined by at least two mirrors is positioned downstream from an electron beam source for receiving the beam of electrons and for exchanging energy therewith. This method includes the steps of choosing a mirror radius size p for the mirrors forming at least one open resonator which is large enough relative to the spot size of a desired radiation cyclotron harmonic w /sub n/ so that the harmonic w /sub n/ oscillates within the at least one resonator, but small enough so that the spot size for the next lower cyclotron harmonic w /sub m/ is larger than the mirror so that the harmonic w /sub m/ does not oscillate due to diffraction losses. This method further includes the step of generating an electron beam via the electron beam source with a beam current which is greater than or equal to the starting current I /sub n/ for the desired nth cyclotron harmonic, but less than the starting current I /sub m/ for the mth cyclotron harmonic. The method also includes the step of extracting radiation energy at the nth cyclotron harmonic from the at least one open resonator. The desired mirror radius size p for a given cyclotron harmonic frequency w /sub n/, for a desired diffraction loss Y /sub n/ for that harmonic n, a given half length separation L /sub y/ between the mirrors, and a given radius of curvature R /sub M/, can be determined by the equation wherein r /sub on/ is the spot size at the mirror for radiation at the nth cyclotron harmonic

  15. Gyrotron source system for ITER plasma start up

    Full text: For a reliable plasma current start-up with a limited toroidal electric field of ∼0.3V/m, ITER would require Electron Cyclotron Heating (ECH) assistance during this phase. An ECH Start-up system with an installed capacity of 3MW RF power, at a frequency of ∼127 GHz with a maximum pulse length of 10 s, is being envisaged for ITER Plasma Start-up system. The Indian Participating Team (IN PT) is currently working on the details of the gyrotron source including auxiliary power supplies, High voltage power supplies, protections and controls for the ECH Start-up system. The specified gyrotron sources are expected to be commercially available involving certain development on the part of supplier to re adopt the proven technologies to a new design suitable for the specified frequency. Diode type tube configuration would be preferred, as this would allow a simpler High voltage power supply configuration. The required HVPS would be based on PSM technology and one HVPS would be driving all the three start up gyrotrons in parallel. The required auxiliary power supplies like the Ion pump power supplies, Magnet power supplies, filament power supplies and the gyrotron tanks would be procured as per the basic designs and /or tube specifications. A VME based Data Acquisition and Control system would be built with various fast (critical) and slow interlocks for the safe operation of the tubes. For the critical faults, the HVPS would be removed within a time scale of 10 μs. Various parameters like rf, vacuum, cooling and DC parameters would be monitored and/or set remotely. Integrated testing of the gyrotron source system into a calorimetric water load is planned at IN-PT site. The paper highlights the details of the integrated gyrotron system as planned by the Indian participating team. (author)

  16. Oscillating virtual cathode, large-orbit gyrotron and driver

    VanHaaften, F.W.; Hoeberling, R.F.; Fazio, M.V.

    1986-01-01

    Studies using an oscillating virtual cathode (vircator) and a large-orbit gyrotron to generate microwave levels of several hundred megawatts are being conducted at the Los Alamos National Laboratory (LANL). A pulse level of approx.1 MV, with length approaching 1 ..mu..s at a repetition rate of a few hertz, is anticipated for extension of these studies from the present single-shot mode with 100-ns pulse width. The increased pulse width is needed to test longer pulse length microwave sources. Pulse forming network (PFN), transformer-coupled drivers have been studied and are part of the subject of this paper. The large-orbit gyrotron is discussed here.

  17. Active heater control and regulation for the Varian VGT-8011 gyrotron

    The Varian VGT-8011 gyrotron is currently being used in the new 110 GHz 2 MW ECH system installed on D3-D. This new ECH system augments the 60 GHz system which uses Varian VA-8060 gyrotrons. The new 110 GHz system will be used for ECH experiments on D3-D with a pulse width capability of 10 sec. In order to maintain a constant RF outpower level during long pulse operation, active filament-heater control and regulation is required to maintain a constant cathode current. On past D3-D experiments involving the use of Varian VA-8060 gyrotrons for ECH power, significant gyrotron heater-emission depletion was experienced for pulse widths > 300 msec. This decline in heater-emission directly results in gyrotron-cathode current droop. Since RF power from gyrotrons decreases as cathode current decreases, it is necessary to maintain a constant cathode current level during gyrotron pulses for efficient gyrotron operation. Therefore, it was determined that a filament-heater control system should be developed for the Varian VGT-8011 gyrotron which will include cathode-current feed-back. This paper discusses the mechanisms used to regulate gyrotron filament-heater voltage by using cathode-current feed-back. 1 fig

  18. Electron beam emission and interaction of double-beam gyrotron

    Highlights: ► The complete electrical design of electron gun and interaction structure of double-beam gyrotron. ► EGUN code is used for the simulation of electron gun of double-beam gyrotron. ► MAGIC code is used for the simulation of interaction structure of double-beam gyrotron. ► Design validations with other codes. - Abstract: This paper presents the numerical simulation of a double-beam magnetron injection gun (DB-MIG) and beam-wave interaction for 60 GHz, 500 kW gyrotron. The beam-wave interaction calculations, power and frequency growth estimation are performed by using PIC code MAGIC. The maximum output power of 510 kW at 41.5% efficiency, beam currents of 6 A and 12 A, electron beam velocity ratios of 1.41 and 1.25 and beam voltage of 69 kV are estimated. To obtain the design parameters, the DB-MIG with maximum transverse velocity spread less than 5% is designed. The computer simulations are performed by using the commercially available code EGUN and the in-house developed code MIGANS. The simulated results of DB-MIG design obtained by using the EGUN code are also validated with another trajectory code TRAK, which are in good agreement.

  19. New results and applications for the quasioptical gyrotron. Interim report

    Fliflet, A.W.; Fischer, R.P.; Manheimer, W.M.

    1993-02-26

    The quasioptical gyrotron (QOG), which features an open resonator formed by a pair of spherical mirrors instead of the conventional gyrotron waveguide cavity, has been under development at the U.S. Naval Research Laboratory as a tunable high power millimeterwave source for tokamak plasma heating, advanced radars, and power beaming. In the free running oscillator configuration, the QOG has produced a peak power of 6OOkW at a frequency of 120GHZ, and a peak efficiency of 12% at 200kW. Results have recently been obtained for a quasioptical gyroklystron (QOGK) realized by the addition of an open-mirror prebunching resonator driven by an 85GHz, 1.5kW Extended Interaction Oscillator. Efficiency enhancement by mode priming has been investigated, and efficiencies up to 19% have been obtained by increasing the detuning of the operating mode. An overall efficiency of 30% was obtained by the addition of a simple depressed collector. The high circulating power in the QOG resonator is currently being considered for use as an electromagnetic wiggler for compact IR free-electron lasers. The QOG is also promising as a source for an active sensor of upper atmosphere trace impurities.... Gyrotrons, Gyroklystron, Atmospheric sensing, Quasioptical gyrotron, Electromagnetic wiggler, Free-electron laser.

  20. Research on advanced high power gyrotrons at FZK

    The experimental 170 GHz coaxial cavity gyrotron for ITER has been assembled and installed in the SC magnet. The operation started in May 2004 with performing the alignment and conditioning of the tube. The main goal of the experiments is to verify the design of components for a 2 MW, CW industrial prototype

  1. The DIII-D ECH multiple gyrotron control system

    DIII-D's ECH upgrade with 1 MW, 110 GHz gyrotrons is ongoing, and with it, an upgrade of the control system. The ECH Multiple Gyrotron Control System uses software distributed among networked computers, interfaced to a programmable logic controller (PLC), the timing and pulse system, power supplies, vacuum and wave guide controls, and instrumentation. During DIII-D operations, the system will allow a chief and a co-operator to control and monitor a number of gyrotrons from different manufacturers. The software, written using LabVIEW, allows for remote and multiple operator control. Thus any supported computer can become a control station and multiple projects can be simultaneously accommodated. Each operator can be given access to the controls of all gyrotrons or to a subset of controls. Status information is also remotely available. The use of a PLC simplifies the hardware and software design. It reduces interlock and control circuitry, includes monitoring for slow analog signals, and allows one software driver to efficiently interface to a number of systems. In addition, the interlock logic can be easily changed and control points can be forced as needed. The pulse system is designed around arbitrary function generators. Various modulation schemes can be accommodated, including real-time control of the modulation. This discussion will include the hardware and software design of the control system and its current implementation

  2. Design study of a test stand for ITER gyrotron

    In the frame of development of the ITER electron cyclotron wave (ECW) system, a two MW CW coaxial cavity gyrotron will be developed during the Sixth Framework Program (2003-2006). Such development relies on the availability of a test stand capable of providing the electrical energy and cooling capacity. This test stand will possibly be used, in a later stage, for the component test of the ITER ECW system. This paper will first present the main parameters of this new coaxial gyrotron. Then we describe the test stand itself, including the general requirements for testing and evaluating the behaviour of the RF source and then a description of the electrical system design. Compared to the ITER reference design, the test stand emphasises the requirement of flexibility, which is necessary during the development of the gyrotron. The additional electrical equipment is included in the overview of the electrical system. The cooling system will be an important part of the design study. Indeed, the design efficiency of such a depressed collector gyrotron is ∼50%, implying >4 MW of continuous heat dissipation and evacuation by the cooling equipment. The specifications of the cooling system must also comply with ITER reference design values

  3. Development of high power gyrotron with energy recovery system

    A gyrotron with an energy recovery system was developed and its stable operation was performed. The efficiency was improved from 30% to 50% at 610kW, 50msec, and the long pulse, high efficiency operation, 350kW, 5sec, 48% was demonstrated. These results should bring a large cost reduction of ECH system. (orig.)

  4. A high efficiency, high power 100 GHz gyrotron

    Gyrotrons, operating at 28 GHz, 35 GHz and 60 GHz are currently producing 100-200 KW, pulsed and CW, for electron cyclotron heating experiments in magnetically-confined gaseous fusion machines. Recently, considerable interest has been expressed towards the development of a 100 GHz, 1.0 MW CW gyrotron for increasing the electron temperature above that achieved with the lower frequency, lower power devices listed above. Toward this goal, Hughes Aircraft Company has developed a 100 GHz, 0.5 MW gyrotron operating at low duty at 30 msec pulse widths. This device employs a single anode magnetron injection gun operating at a cathode voltage of 90 kV at 14A cathode current. Control of the electron beam is by cathode pulsing or CW. RF control is accomplished by low-level cathode magnetic field modulation. Computations show that velocity spread, both perpendicular and parallel, is considerable lower, rotational energy is higher and voltage gradients are significantly lower than for a comparable double anode magnetron injection gun, typically employed on lower frequency gyrotrons

  5. Development of 100 GHz band high power gyrotron for fusion experimental reactor

    In JAERI, 1MW gyrotrons of 170GHz and 110GHz are under development for ITER (International Thermonuclear Experimental Reactor) and JT-60U, respectively. Both gyrotrons have a depressed collector for an efficiency improvement and a low loss synthetic diamond window that enables Gaussian beam output over 1MW. Three 110GHz gyrotrons are used on an electron cyclotron heating and current drive(ECH/ECCD) system on JT-60U, in which the output power of ∼0.8MW/3sec was generated from each gyrotron. As for 170GHz, output power of 1.2MW with electron beam of 85kV/49A was obtained on a short pulse gyrotron. The efficiency of ∼57% was attained at 1.1MW with the depressed collector. Based on these results, the 1MW 170GHz gyrotron for long pulse operation was fabricated. (author)

  6. ECH control system for new 1 MW 110 GHz gyrotrons at DIII-D

    Two new Varian 1 MW 110 GHz gyrotrons are currently being developed and are due to be tested at General Atomics next year. A new cost-effective gyrotron control system to operate multiple gyrotrons simultaneously is being developed. Different systems and combinations that were considered include CAMAC, PLC, VXIbus, and a local computer. This paper will explain the decision making processes used in choosing and implementing the new control system architecture

  7. Particle-in-cell (PIC) simulations of beam instabilities in gyrotrons

    Extensive simulations are performed to investigate effects of electron cyclotron instabilities on the gyrotron beam quality, using two-dimensional axisymmetric particle-in-cell (PIC) codes. Both electrostatic and electromagnetic models, as well as realistic geometries of the gyrotron are considered. It is found that a large beam density can lead to an electrostatic-instability-induced energy spread which substantially degrades the gyrotron efficiency. (author) 11 figs., 14 refs

  8. A generic mode selection strategy for high-order mode gyrotrons operating at multiple frequencies

    Franck, Joachim; Avramidis, Konstantinos; Gantenbein, Gerd; Illy, Stefan; Jin, Jianbo; Thumm, Manfred; Jelonnek, John

    2015-01-01

    High-power, high-frequency gyrotrons for electron cyclotron resonance heating and current drive, such as proposed for the demonstration thermonuclear fusion reactor DEMO, require operating modes of very high order. As it is shown, the selection of the operating modes for such gyrotrons can be based on multi-frequency operability. A general selection strategy is derived, suitable for multi-purpose multi-frequency gyrotrons with quasi-optical mode converter and single-disc output window. Two examples, one of them relevant for future DEMO gyrotron designs, are discussed.

  9. Recent Tests on 117.5 GHz and 170 GHz Gyrotrons

    Felch K.

    2015-01-01

    Full Text Available Two megawatt-class gyrotrons at frequencies of 117.5 GHz and 170 GHz have recently been fabricated and tested at CPI. The 117.5 GHz gyrotron was designed to produce up to 1.8 MW for 10-second pulses, and will be used for electron cyclotron heating and current drive on the DIII-D tokamak at General Atomics. The 170 GHz gyrotron is specified as a 500 kW CW system, but has been designed with the goal of generating up to 1 MW CW. Oak Ridge National Laboratory will use the gyrotron in ITER ECH transmission line testing.

  10. Study of the parasitic oscillations in a gyrotron

    This work is dedicated to the study of parasitic instabilities in a gyrotron, and to the influence of such instabilities on the interaction efficiency. The gyrotron is a high-power millimeter wave radiation source, based on the resonant interaction between a weakly relativistic electron beam immersed in a guiding magnetic field, and an electromagnetic wave. The gyrotron investigated here operates at a frequency close to 100 GHz: its main feature is that it is quasi optical. In this configuration, the electron beam interacts with a high order TEM eigenmode of a Fabry-Perot resonator, the axis of which is perpendicular to the electron beam path. During the development of this source, the highest efficiency that was achieved is approximately 30% lower than the theoretical predictions. At the same time, parasitic oscillations at frequencies close to the maximum relativistic cyclotronic frequency are detected. The power associated with these oscillations ranges from a few watts to a few kilowatts, with threshold currents of the order of 100 mA. It is suspected that the excitation of parasitic oscillations in the beam duct section before the interaction region might have a dramatic effect on the electron beam distribution function inducing, in particular, an energy spread. The cyclotron maser instability responsible for the energy exchange between particles and fields in a gyrotron, is very sensitive to energy spreads. It is thus necessary to identify the origin of the parasitic radiation. A few physical mechanisms suspected to lead to a degradation of the electron beam properties were investigated: the cyclotron maser process itself, the Bernstein electrostatic instability and the Langmuir instability. The experimental work concentrated on the study of the beam ducts between the electron gun and the resonant cavity. (author) figs., tabs., 90 refs

  11. Characterization of a gyrotron cavity at 10 GHz

    Experiments have been conducted to characterize a gyrotron cavity designed to operate in the Te 021 mode at 10 GHz. Small holes were introduced into the cavity to couple in and detect the probing power. Evaluation of the loaded Q factor is based on bandwidth measurements whereas standing-wave electric field profile is determined by using perturbation techniques. Good agreement between measured and predicted values of resonant frequencies and Q factors for several fundamental TE modes is found. (author)

  12. Investigations and advanced concepts on gyrotron interaction modeling and simulations

    Avramidis, K. A., E-mail: konstantinos.avramidis@kit.edu [Institute for Pulsed Power and Microwave Technologies, Karlsruhe Institute of Technology, Karlsruhe 76131 (Germany)

    2015-12-15

    In gyrotron theory, the interaction between the electron beam and the high frequency electromagnetic field is commonly modeled using the slow variables approach. The slow variables are quantities that vary slowly in time in comparison to the electron cyclotron frequency. They represent the electron momentum and the high frequency field of the resonant TE modes in the gyrotron cavity. For their definition, some reference frequencies need to be introduced. These include the so-called averaging frequency, used to define the slow variable corresponding to the electron momentum, and the carrier frequencies, used to define the slow variables corresponding to the field envelopes of the modes. From the mathematical point of view, the choice of the reference frequencies is, to some extent, arbitrary. However, from the numerical point of view, there are arguments that point toward specific choices, in the sense that these choices are advantageous in terms of simulation speed and accuracy. In this paper, the typical monochromatic gyrotron operation is considered, and the numerical integration of the interaction equations is performed by the trajectory approach, since it is the fastest, and therefore it is the one that is most commonly used. The influence of the choice of the reference frequencies on the interaction simulations is studied using theoretical arguments, as well as numerical simulations. From these investigations, appropriate choices for the values of the reference frequencies are identified. In addition, novel, advanced concepts for the definitions of these frequencies are addressed, and their benefits are demonstrated numerically.

  13. Modeling of mode purity in high power gyrotrons

    Cai, S.Y.; Antonsen, T.M. Jr.; Saraph, G.P. [Univ. of Maryland, College Park, MD (United States)] [and others

    1993-04-01

    Spurious mode generation at the same frequency of the operational mode in a high power gyrotron can significantly reduce the power handling capability and the stability of a gyrotron oscillator because these modes are usually not matched at the output window and thus have high absorption and reflection rates. To study the generation of this kind of mode, the authors developed a numerical model based on an existing multimode self-consistent time-dependent computer code. This model includes both TE and TM modes and accounts for mode transformations due to the waveguide inhomogeneity. With this new tool, they study the mode transformation in the gyrotron and the possibility of excitation of parasitic TE and TM modes in the up taper section due to the gyroklystron mechanism. Their preliminary results show moderate excitation of both TE and TM modes at the same frequency as the main operating mode at locations near their cutoff. Details of the model and further simulation results will be presented.

  14. Solid-state gyrotron body power supply, test results

    Santinelli, M. [Association Euratom-ENEA, ENEA CR Frascati, 00044 Frascati (Italy)], E-mail: santinelli@frascati.enea.it; Claesen, R.; Coletti, A. [Association Euratom-ENEA, ENEA CR Frascati, 00044 Frascati (Italy); Bonicelli, T.; Mondino, P.L. [EFDA, EFDA CSU Garching, D-85748 Garching (Germany); Pretelli, M.; Rinaldi, L.; Sita, L.; Taddia, G. [OCEM SpA, Via 2 Agosto 1980 no. 11, 40016 San Giorgio di Piano (Italy)

    2007-10-15

    A 170 GHz, 2 MW, steady-state gyrotron is being developed in collaboration between European research associations and industries to be used for the electron cyclotron resonance heating (ECRH) system of ITER, the gyrotron is presently in the prototype state. EFDA entrusted ENEA with the design of a new power supply for the gyrotron's body; in which, the traditional power vacuum tubes are replaced with solid-state components (IGBT); furthermore ENEA had the task of developing the new body power supply (BPS), following the initial conceptual design. The BPS is formed by 50 identical bidirectional (in current) modules, connected in series; the BPS's control system regulates the output voltage by changing the modulation index. OCEM Spa, under ENEA's supervision, has manufactured the BPS. Tests, done at the start of this year, showed the substantial agreement between the initial technical specifications and the values achieved. Particularly the ramp-up/down-emergency time (50-10 {mu}s), the accuracy ({+-}0.5%), the sine wave modulation (45-20 kV at 5 kHz) and the maximum phase shift (<10 deg.) have been tested. In the article, the new stair-way modulation (SWM) scheme will be sketched and the test results will be described in detail.

  15. User's manual for LINEAR, a computer program that calculates the linear characteristics of a gyrotron

    This program calculates the linear characteristics of a gyrotron. This program is capable of: (1) calculating the starting current or frequency detuning for each gyrotron mode, (2) generating mode spectra, (3) plotting these linear characteristics as a function of device parameters (e.g., beam voltage), and (4) doing the above for any axial rf field profile

  16. Development and application of superconducting magnet for gyrotron with 4 mm wave length

    A superconducting magnet for gyrotron with 4 mm wave legnth is developed, its main magnetic field reaches 3 T. The gyrotron combined with the magnet producesfundamental wave long pulse, its power is more than 60 kW, pulse duration 10 ∼ 20 ms, frequency 70 GHz. It is used for plasma preionization experiment on HL-1 Tokamak

  17. Gyrotron and power supply development for upgrading the electron cyclotron heating system on DIII-D

    Highlights: ► Vendor completed design of 1.5 MW, 117.5 GHz gyrotron for DIII-D. ► Fabrication of gyrotron by vendor underway. ► Finalizing design of solid-state high voltage modulator for cathode power supply. ► Fabrication of solid-state high voltage modulator has begun. ► Finalizing design of high voltage linear amplifier for gyrotron body power supply. -- Abstract: An upgrade of the electron cyclotron heating system on DIII-D to almost 15 MW is being planned which will expand it from a system with six 1 MW 110 GHz gyrotrons to one with ten gyrotrons. A depressed collector 1.2 MW 110 GHz gyrotron is being commissioned as the seventh gyrotron. A new 117.5 GHz 1.5 MW depressed collector gyrotron has been designed, and the first article will be the eighth gyrotron. Two more are planned, increasing the system to ten total gyrotrons, and the existing 1 MW gyrotrons will subsequently be replaced with 1.5 MW gyrotrons. Communications and Power Industries completed the design of the 117.5 GHz gyrotron, and are now fabricating the first article. The design was optimized for a nominal 1.5 MW at a beam voltage of 105 kV, collector potential depression of 30 kV, and beam current of 50 A, but can achieve 1.8 MW at 60 A. The design of the collector permits modulation above 100 Hz by either the body or the cathode power supply, or both, while modulation below 100 Hz must use only the cathode power supply. General Atomics is developing solid-state power supplies for this upgrade: a solid-state modulator for the cathode power supply and a linear high voltage amplifier for the body power supply. The solid-state modulator has series-connected insulated-gate bipolar transistors that are switched at a fixed frequency by a pulse-width modulation regulator to control the output voltage. The design of the linear high voltage amplifier has series-connected transistors to control the output voltage, which was successfully demonstrated in a proof-of-principle test at 2 kV. The

  18. Gyrotron and power supply development for upgrading the electron cyclotron heating system on DIII-D

    Tooker, Joseph F., E-mail: tooker@fusion.gat.com [General Atomics, PO Box 85608, San Diego, CA 92186-5608 (United States); Huynh, Paul [General Atomics, PO Box 85608, San Diego, CA 92186-5608 (United States); Felch, Kevin; Blank, Monica; Borchardt, Philipp; Cauffman, Steve [Communications and Power Industries, 811 Hanson Way, Palo Alto, CA 94304 (United States)

    2013-10-15

    Highlights: ► Vendor completed design of 1.5 MW, 117.5 GHz gyrotron for DIII-D. ► Fabrication of gyrotron by vendor underway. ► Finalizing design of solid-state high voltage modulator for cathode power supply. ► Fabrication of solid-state high voltage modulator has begun. ► Finalizing design of high voltage linear amplifier for gyrotron body power supply. -- Abstract: An upgrade of the electron cyclotron heating system on DIII-D to almost 15 MW is being planned which will expand it from a system with six 1 MW 110 GHz gyrotrons to one with ten gyrotrons. A depressed collector 1.2 MW 110 GHz gyrotron is being commissioned as the seventh gyrotron. A new 117.5 GHz 1.5 MW depressed collector gyrotron has been designed, and the first article will be the eighth gyrotron. Two more are planned, increasing the system to ten total gyrotrons, and the existing 1 MW gyrotrons will subsequently be replaced with 1.5 MW gyrotrons. Communications and Power Industries completed the design of the 117.5 GHz gyrotron, and are now fabricating the first article. The design was optimized for a nominal 1.5 MW at a beam voltage of 105 kV, collector potential depression of 30 kV, and beam current of 50 A, but can achieve 1.8 MW at 60 A. The design of the collector permits modulation above 100 Hz by either the body or the cathode power supply, or both, while modulation below 100 Hz must use only the cathode power supply. General Atomics is developing solid-state power supplies for this upgrade: a solid-state modulator for the cathode power supply and a linear high voltage amplifier for the body power supply. The solid-state modulator has series-connected insulated-gate bipolar transistors that are switched at a fixed frequency by a pulse-width modulation regulator to control the output voltage. The design of the linear high voltage amplifier has series-connected transistors to control the output voltage, which was successfully demonstrated in a proof-of-principle test at 2 kV. The

  19. Perspective gyrotron with mode converter for co- and counter-rotation operating modes

    Chirkov, A. V.; Denisov, G. G.; Kuftin, A. N.

    2015-06-01

    A gyrotron oscillator operating efficiently at modes of both rotations was developed and tested. The gyrotron operation can be switched between two modes: co- and counter rotating ones with respect to electron rotation in a resonance magnetic field. A synthesized mode converter provides output of both waves in the form of two different paraxial wave beams corresponding to direction of the mode rotation. Measured gyrotron power (up to 2 MW), interaction efficiency (34%), and diffraction losses in the mode converter (≈2%) agree well with the design values. The proposed gyrotron scheme alloys principal enhancement in the device parameters—possibility of electronic switching of output wave beam direction and possibility to arrange an effective scheme to provide frequency/phase locking of a gyrotron-oscillator.

  20. Infrared monitoring of 110 GHz gyrotron windows at DIII-D

    The combination of low millimeter wave losses and excellent thermal conductivity with good mechanical properties make artificial chemical vapor deposition (CVD) diamonds a compelling choice for 1 MW 110 GHz gyrotron windows. Five gyrotrons are currently operating at the DIII-D tokamak. Three Gycom gyrotrons have boron nitride (BN) ceramic windows. Due to temperature increases of the windows up to about 930 deg. C, the pulse duration of these tubes is limited to 2 s for output power near 800 kW. Two Communications and Power Industries (CPI) gyrotrons with diamond windows are also installed and operating. The diamond disks of these windows and the construction of their water-cooling assemblies are different. This paper reviews the infrared (IR) measurements of both types of gyrotron windows, with emphasis on the two diamond designs. (authors)

  1. Perspective gyrotron with mode converter for co- and counter-rotation operating modes

    A gyrotron oscillator operating efficiently at modes of both rotations was developed and tested. The gyrotron operation can be switched between two modes: co- and counter rotating ones with respect to electron rotation in a resonance magnetic field. A synthesized mode converter provides output of both waves in the form of two different paraxial wave beams corresponding to direction of the mode rotation. Measured gyrotron power (up to 2 MW), interaction efficiency (34%), and diffraction losses in the mode converter (≈2%) agree well with the design values. The proposed gyrotron scheme alloys principal enhancement in the device parameters—possibility of electronic switching of output wave beam direction and possibility to arrange an effective scheme to provide frequency/phase locking of a gyrotron-oscillator

  2. Performance of 170 GHz high-power gyrotron for CW operation

    A quasi-steady-state oscillation of 100 s with 0.5 MW power level was demonstrated on a 170 GHz ITER gyrotron. The temperature of major components of the gyrotron reached the steady state, which gives a prospect for a 1 MW-CW, 170 GHz ITER gyrotron. For a further pulse extension and power increase, the gyrotron and its control system have been modified; i.e. a built-in radiator has been optimized for improvement of an efficiency of gyrotron output power and reduction of stray radiation, and pre-program controls of a cathode heater power, magnetic field at the cavity and voltage between anode and cathode, have been employed for stabilization of the beam current and the output power. (author)

  3. Research on a 170 GHz, 2 MW coaxial cavity gyrotron with inner-outer corrugation

    Hou, Shenyong, E-mail: houshenyong@sohu.com [Yangtze Normal University, Chongqing, 408001 (China); Yu, Sheng; Li, Hongfu [University of Electronics Science and Technology of China, Chengdu 610054 (China)

    2015-03-15

    In this paper, a coaxial cavity gyrotron with inner-outer corrugation is researched. The electron kineto-equations and the first order transmission line equations of the gyrotron are derived from Lorentz force equation and the transmission line theory, respectively. And then, a 2 MW, 170 GHz coaxial cavity gyrotron with inner-outer corrugation is designed. By means of numerical calculation, the beam-wave interaction of the coaxial cavity gyrotron with inner-outer corrugation is investigated. Results show that the efficient and the outpower of the gyrotron are 42.3% and 2.38 MW, respectively.

  4. High power 303 GHz gyrotron for CTS in LHD

    A high-power pulsed gyrotron is under development for 300 GHz-band collective Thomson scattering (CTS) diagnostics in the Large Helical Device (LHD). High-density plasmas in the LHD require a probe wave with power exceeding 100 kW in the sub-terahertz region to obtain sufficient signal intensity and large scattering angles. At the same time, the frequency bandwidth should be less than several tens of megahertz to protect the CTS receiver using a notch filter against stray radiations. Moreover, duty cycles of ∼ 10% are desired for the time domain analysis of the CTS spectrum. At present, a 77 GHz gyrotron for electron cyclotron heating is used as a CTS wave source in the LHD. However, the use of such a low-frequency wave suffers from refraction, cutoff and absorption at the electron cyclotron resonance layer. Additionally, the signal detection is severely affected by background noise from electron cyclotron emission. To resolve those problems, high-power gyrotrons in the 300 GHz range have been developed. In this frequency range, avoiding mode competition is critical to realizing high-power and stable oscillation. A moderately over-moded cavity was investigated to isolate a desired mode from neighbouring modes. After successful tests with a prototype tube, the practical one was constructed with a cavity for TE22,2 operation mode, a triode electron gun forming intense laminar electron beams, and an internal mode convertor. We have experimentally confirmed single mode oscillation of the TE22,2 mode at the frequency of 303.3 GHz. The spectrum peak is sufficiently narrow. The output power of 290 kW has been obtained at the moment

  5. High power 303 GHz gyrotron for CTS in LHD

    Yamaguchi, Y.; Kasa, J.; Saito, T.; Tatematsu, Y.; Kotera, M.; Kubo, S.; Shimozuma, T.; Tanaka, K.; Nishiura, M.

    2015-10-01

    A high-power pulsed gyrotron is under development for 300 GHz-band collective Thomson scattering (CTS) diagnostics in the Large Helical Device (LHD). High-density plasmas in the LHD require a probe wave with power exceeding 100 kW in the sub-terahertz region to obtain sufficient signal intensity and large scattering angles. At the same time, the frequency bandwidth should be less than several tens of megahertz to protect the CTS receiver using a notch filter against stray radiations. Moreover, duty cycles of ~ 10% are desired for the time domain analysis of the CTS spectrum. At present, a 77 GHz gyrotron for electron cyclotron heating is used as a CTS wave source in the LHD. However, the use of such a low-frequency wave suffers from refraction, cutoff and absorption at the electron cyclotron resonance layer. Additionally, the signal detection is severely affected by background noise from electron cyclotron emission. To resolve those problems, high-power gyrotrons in the 300 GHz range have been developed. In this frequency range, avoiding mode competition is critical to realizing high-power and stable oscillation. A moderately over-moded cavity was investigated to isolate a desired mode from neighbouring modes. After successful tests with a prototype tube, the practical one was constructed with a cavity for TE22,2 operation mode, a triode electron gun forming intense laminar electron beams, and an internal mode convertor. We have experimentally confirmed single mode oscillation of the TE22,2 mode at the frequency of 303.3 GHz. The spectrum peak is sufficiently narrow. The output power of 290 kW has been obtained at the moment.

  6. The Development of 460 GHz gyrotrons for 700 MHz DNP-NMR spectroscopy

    Idehara, T.; Tatematsu, Y.; Yamaguchi, Y.; Khutoryan, E. M.; Kuleshov, A. N.; Ueda, K.; Matsuki, Y.; Fujiwara, T.

    2015-07-01

    Two demountable gyrotrons with internal mode converters were developded as sub-THz radiation sources for 700 MHz DNP (Dynamic Nuclear Polarization) enhanced NMR spectroscopy. Experimental study on the DNP-NMR spectroscopy will be carried out in Osaka University, Institute for Protein Research, as a collaboration with FIR UF. Both gyrotrons operate near 460 GHz and the output CW power measured at the end of transmission system made by circular waveguides is typically 20 to 30 watts. One of them named Gyrotron FU CW GVI (we are using "Gyrotron FU CW GO-1" as an official name in Osaka University) is designed to have a special function of high speed frequency modulation δ f within 100 MHz band. This will expand excitable band width of ESR and increase the number of electron spins contributing to DNP. The other gyrotron, Gyrotron FU CW GVIA ("Gyrotron FU CW GO-II") has a function of frequency tunability Δ f in the range of wider than 1.5 GHz, which is achieved in steady state by changing magnetic field intensity. This function should be used for adjusting the output frequency at the optimal value to achieve the highest enhancement factor of DNP.

  7. Thermal Stress Analysis of 1 MW Gyrotron Collector

    At the DIII-D tokamak, up to 6 gyrotrons supply ECH power to the plasma. Each gyrotron injects 800 kW for 5 s at the tokamak during normal operation and are designed to generate 1 MW for 10 s pulse lengths. A power of ∼ 2000 kW is absorbed by the collector of each gyrotron from the electron beam. The gyrotrons are manufactured by Communications and Power Industries (CPI). The collectors are 0.6 m diameter cylinders, 60 cm in height. The collector walls are 20.7 mm thick and have 196 coolant holes of 5.3 mm diameter. Each pair of adjacent coolant holes is connected in series to provide 98 cooling paths. The collector material is oxygen free high conductivity copper (OFHC) and the collectors are cooled by water at a design flow rate of 300 gpm. In order to reduce the peak thermal load on the collector walls, the beam is swept over the collector wall at 4 Hz and an amplitude of about 15 cm using an external coil. Sweeping reduces the effective peak heat flux from 1400 W/cm2 to 600 W/cm2. During 2004 and 2005, some of the collectors failed due to stress cracks. In order to investigate reasons for these failures, a nonlinear elastic plastic thermal stress analysis of the collector was undertaken. The thermal stress analysis results indicated that the effective strain for OFHC material under the operating conditions limited the cycle life of the collector due to fatigue, resulting in failures. The desired service life of more than 105 thermal cycles can be obtained by 1) operational changes, such as: increasing the frequency and amplitude of sweeping to reduce the average heat flux, 2) design changes, such as: increasing the height and/or diameter of collector, enhancing the heat transfer coefficient by roughening the coolant channel walls or 3) changing the material of the collector to dispersion strengthened copper such as Glidcop. The analysis and conclusions will be presented. (author)

  8. Influence of construction concepts on training behavior of gyrotron magnets

    A series of 60 NbTi gyrotron magnets intended mainly for high frequency plasma heating complexes at Tokamak T-10 and Tokamak T-15, and prototypes and later improved versions for the same applications within ITER project, were developed and tested. A variety of constructional and technological concepts was applied. As a result of empirical experience in parallel with the application of established theoretical models to the magnet development, a remarkable improvement in winding mechanical stability was reached. The differences in magnet winding construction are related to operational as well as training and quench behaviour. (Author)

  9. Stabilization of Gyrotron Frequency by PID Feedback Control on the Acceleration Voltage

    Khutoryan, E. M.; Idehara, T.; Kuleshov, A. N.; Tatematsu, Y.; Yamaguchi, Y.; Matsuki, Y.; Fujiwara, T.

    2015-12-01

    The results of frequency stabilization by proportional-integral-derivative (PID) feedback control of acceleration voltage in the 460-GHz Gyrotron FU CW GVI (the official name in Osaka University is Gyrotron FU CW GOI) are presented. The experiment was organized on the basis of the frequency modulation by modulation of acceleration voltage of beam electrons. The frequency stabilization during 10 h experiment was better than 10-6, which is compared with the results of the frequency deviation in free-running gyrotron operation.

  10. Development of ITER CODAC compatible gyrotron local control system and its operation

    JAEA has developed a prototype of the gyrotron local control system required in the ITER ECH and CD system. This system is compatible with the ITER plant control design handbook. The code is based on the ITER CODAC Core System and implements functions of the state transition management and monitoring in the gyrotron operating system and the power supply control and data acquisition. We have succeeded in the demonstration test of high power operation of an ITER 170 GHz gyrotron using the present system and the ITER compatible setup and protocol. (J.P.N.)

  11. A 2 MW, 170 GHz coaxial cavity gyrotron - experimental verification of the design of main components

    A 2 MW, CW, 170 GHz coaxial cavity gyrotron is under development in cooperation between European Research Institutions (FZK Karlsruhe, CRPP Lausanne, HUT Helsinki) and the European tube industry (TED, Velizy, France). The design of critical components has recently been examined experimentally at FZK Karlsruhe with a short pulse (∼ few ms) coaxial cavity gyrotron. This gyrotron uses the same cavity and the same quasioptical (q.o.) RF-output system as designed for the industrial prototype and a very similar electron gun

  12. New results and applications for the quasioptical gyrotron

    Fliflet, A.W.; Fischer, R.P.; Manheimer, W.M. (Plasma Physics Division, U.S. Naval Research Laboratory, Washington, D.C. 20375-5320 (United States))

    1993-07-01

    The quasioptical gyrotron (QOG), which features an open resonator formed by a pair of spherical mirrors instead of the conventional gyrotron waveguide cavity, has been under development at the U. S. Naval Research Laboratory as a tunable high power millimeter-wave source for tokamak plasma heating, advanced radars, and power beaming. Results have recently been obtained for a quasioptical gyroklystron (QOGK) realized by the addition of an open-mirror prebunching resonator driven by an 85 GHz, 1.5 kW extended interaction oscillator. Efficiency enhancement by mode priming has been investigated, and efficiencies up to 19% have been obtained by increasing the frequency detuning of the operating mode. An overall efficiency of 30% was obtained by the addition of a simple depressed collector. Phase-locked operation was demonstrated at a power of 57 kW and efficiency of 16%. The high circulating power in the QOG resonator is currently being considered for use as an electromagnetic wiggler for compact infrared free-electron lasers. The QOG is also promising as a source for an active sensor of upper atmosphere trace impurities.

  13. Application of Fusion Gyrotrons to Enhanced Geothermal Systems (EGS)

    Woskov, P.; Einstein, H.; Oglesby, K.

    2013-10-01

    The potential size of geothermal energy resources is second only to fusion energy. Advances are needed in drilling technology and heat reservoir formation to realize this potential. Millimeter-wave (MMW) gyrotrons and related technologies developed for fusion energy research could contribute to enabling EGS. Directed MMW energy can be used to advance rock penetration capabilities, borehole casing, and fracking. MMWs are ideally suited because they can penetrate through small particulate extraction plumes, can be efficiently guided long distances in borehole dimensions, and continuous megawatt sources are commercially available. Laboratory experiments with a 10 kW, 28 GHz CPI gyrotron have shown that granite rock can be fractured and melted with power intensities of about 1 kW/cm2 and minute exposure times. Observed melted rock MMW emissivity and estimated thermodynamics suggest that penetrating hot, hard crystalline rock formations may be economic with fusion research developed MMW sources. Supported by USDOE, Office of Energy Efficiency and Renewable Energy and Impact Technologies, LLC.

  14. Frequency Locking and Stabilization Regimes in High-Power Gyrotrons with Low-Q Resonators

    Zotova, I. V.; Ginzburg, N. S.; Denisov, G. G.; Rozental', R. M.; Sergeev, A. S.

    2016-02-01

    Using a nonstationary self-consistent model, we analyze the frequency locking and stabilization regimes arising in gyrotrons with low-Q resonators under the action of an external signal or when reflections from a remote nonresonant load are introduced. In the simulations, we used the parameters of high-power gyrotrons designed for controlled thermonuclear fusion with optimized resonator profile. This approach makes it possible to determine output characteristics of the gyrotrons operated in considered regimes taking into account the effect of the incident wave (external or reflected) on the longitudinal field structure with greater precision compared with the earlier results based on the fixed RF-field structure approximation, while qualitative results of the two approaches coincide. Analysis of the effect of reflections from a remote load has demonstrated a substantial dependence of the efficiency of the gyrotron frequency stabilization on the ratio between the characteristic time scale of the synchronism detuning fluctuations and the signal delay time.

  15. On the mode-competition of high power gyrotrons operating in rotationally symmetric modes

    The gyrotron has proven to be a powerful source in the millimeterwaves region. However fusion application calls for more power per tube. Therefore highly overmoded resonators are required, with a vary dense mode spectrum, which leads to mode-competition. The influence of external parameters - such as the electron beam, magnetic field and load - on mode competition has been investigated theoretically and experimentally. It could be shown, that even in a dense mode spectrum single-mode operation of a gyrotron is possible. Due to the optimized startup conditions high-power single-mode oscillation could be achieved in the KfK 150 GHz gyrotron experiment. In the appendices a self-consistent multi-mode theory is developed and the problems in numerically solving the differential equations of the gyrotron are investigated. (orig.)

  16. Numerical study on a 0.4 THz second harmonic gyrotron with high power

    Terahertz and sub-terahertz science and technology are promising topics today. However, it is difficult to obtain high power source of terahertz wave. In this paper, the mode competition and beam-wave interaction in a gradually tapered cavity are studied to achieve high efficiency of a 0.4THz second harmonic gyrotron in practice. In order to attain high power and stable radiation, the TE32,5 mode is selected as the operating mode of the desired gyrotron to realize single mode oscillation. The issues of studying on the high-order mode gyrotrons are solved effectively by transforming the generalized telegraphist's equations. The efficiency and output power of the gyrotron under different conditions have been calculated by the code, which is based on the transformed equations. Consequently, the results show that single mode second harmonic radiation with power of over 150 kW at frequency of 0.4 THz could be achieved

  17. Performance, diagnostics, controls and plans for the gyrotron system on the DIII-D tokamak

    Ponce D.M.

    2012-09-01

    Full Text Available The DIII-D ECH complex is being upgraded with three new depressed collector gyrotrons. The performance of the existing system has been very good. As more gyrotrons having higher power are added to the system, diagnostics of gyrotron operation, optimization of the performance and qualification of components for higher power become more important. A new FPGA-based gyrotron control system is being installed, additional capabilities for rapid real time variation of the rf injection angles by the DIII-D Plasma Control System are being tested and infrastructure enhancements are being completed. Longer term plans continue to include ECH as a major component in the DIII-D heating and current drive capabilities.

  18. Gyrotron physics from linear to chaotic regimes: experiment and numerical modeling

    Braunmüller, Falk Hans

    2016-01-01

    Gyrotrons belong to the family of high-power coherent radiation sources known as Electron Cyclotron Masers (ECMs) and are based on the physical mechanism of the ECM-instability, converting electron rotational kinetic energy into coherent electromagnetic radiation. The worldwide gyrotron R&D is mainly driven by the application in heating a magnetically confined fusion plasma, which requires coherent radiation sources with MW power-level in the sub-THz frequency range. In the last two decades,...

  19. Development of frequency step tunable 1 MW gyrotron at 131 to 146.5 GHz

    Samartsev, A.; Gantenbein, G.; Dammertz, G.; Illy, S.; Kern, S.; Leonhardt, W.; Schlaich, A.; Schmid, M.; Thumm, M., E-mail: andrey.samartsev@kit.edu [Karlsruhe Institute of Technology, Association EURATOM-KIT, Karlsruhe (Germany)

    2011-07-01

    Effective control of power absorption in tokamaks and stellarators could be achieved by the frequency tuning of ECH and CD power delivered by high-power gyrotrons. In this report some results of the development of a frequency tunable gyrotron with fused-silica Brewster window are presented. Excitation of several modes at 1 MW power level in the range of frequencies from 131 to 146.5 GHz is achieved. (author)

  20. Cold test of cylindrical open resonator for 42 GHz, 200 kW gyrotron

    Vivek Yadav; Sudeep Sharan; Hasina Khatun; Nitin Kumar; M K Alaria; B Jha; S C Deorani; A K Sinha; P K Jain

    2013-12-01

    This paper presents experimental results for cold testing of a gyrotron open resonator. Experiments were carried out to measure resonant frequency and their particular quality factor for TE mode at the frequency 42 GHz. The perturbation technique was used to determine the axial, radial and azimuthal electric field profile for identification of TE031 mode at operating frequency 42 GHz. The good agreement between experimental results and theoretical studies was found. The results verify the design and fabrication of the specific gyrotron cavity.

  1. Gyrotron development at the Instituto de Pesquisas Espaciais

    The conceptual design of a 35GHz gyrotron operating in the TE021 mode, intended for plasma heating experiments, is presented. The electrooptical system is synthesized from the electron beam parameters in the cavity region and the electrodynamical system includes a conventional resonator consisting of truncated cones. The starting and operating characteristics are calculated by integrating the exact equation of electron motion under the action of an RF fiel with fixed spatial distribution. For the moment, the experimental activities, in addition to providing all the infrastructure for the laboratory, are concentrated on the construction of a system of magnetic coils, able to generated a 15kG magnetic induction with a fluctuation of 0.1% over an extension of 13cm, on the manufacture of cavities by using electroforming techniques and on the development of techniques for the construction of electron guns. (author)

  2. Design of Cathode Heater Assembly for High Power Gyrotron

    Bhattacharya, Ranajoy; Khatun, Hasina; Singh, Narendra Kr.; Singh, Udaybir; Sinha, A. K.

    2013-04-01

    A 3D model of dispenser cathode with toroid shape heater assembly is simulated using simulation software, ANSYS Multi-physics. The reported design study of cathode heater assembly of 1 MW 120 GHz gyrotron helps to optimize the input heater power with respect to cathode surface temperature. The simulation study shows that the input power depends strongly on the heater dimension as well as material properties including the potting material. The optimum input power helps to achieve desired current density (10 A/cm2) and cathode surface temperature (1000 °C). Further, the thermal and structural analyses are carried out to study the temperature distribution on the cathode assembly due to the heat dissipation and mechanical strength of the assembly.

  3. Design of a Compact Sub-Terahertz Gyrotron for Spectroscopic Applications

    Sabchevski, Svilen Petrov; Idehara, Toshitaka

    2010-08-01

    In this paper we present the initial design of a novel and versatile high frequency gyrotron with parameters suitable for application to various spectroscopic studies that require coherent radiation in the subterahertz frequency range (such as NMR/DNP spectroscopy, ESR spectroscopy, spectrometer based on the X-ray detected magnetic resonance etc.). The most characteristic feature of the design is that it utilises a compact, cryogen-free 8 T superconducting magnet. As a result, the overall dimensions of the entire device are considerably reduced in comparison with the previously developed tubes belonging to the Gyrotron FU and Gyrotron FU CW series. This makes the novel gyrotron highly portable to diverse laboratory environments and easily embeddable to different measuring systems. The electron-optical system (EOS) of the tube is based on a compact low-voltage magnetron injection gun (MIG), which has been specially designed and optimized together with the resonant cavity using our problem-oriented software package GYROSIM for CAD of gyrotrons. The tube operates at the second harmonic of the cyclotron frequency and generates a radiation with an output power of about 100 W and a frequency tunable up to around 424 GHz, respectively.

  4. Development of dual frequency gyrotron and high power test of EC components

    Sakamoto K.

    2012-09-01

    Full Text Available In JAEA, development of high-power long-pulse gyrotrons is underway. The output power of the gyrotron was applied for high-power long-pulse tests of the transmission line (TL and the equatorial launcher (EL mock up for ITER. The feature of design in the dual frequency gyrotron is the simultaneously satisfying the matching of both frequencies at a window and the same radiation angle at an internal mode convertor for both frequencies. The dual frequency gyrotron was developed and high power operations at 170 GHz and 137 GHz were carried out. The 170 GHz high power experiment of 40 m length ITER relevant TL was carried out and transmission efficiency and mode purity change caused by long pulse operation were measured. The mock-up model of EL was also tested using 170 GHz gyrotron. The power transmission through the quasi-optical beam line in EL was demonstrated using the full scale mock up model. Furthermore, the high power test results of the transmission components will be summarized.

  5. A 250 GHz gyrotron with a 3 GHz tuning bandwidth for dynamic nuclear polarization.

    Barnes, Alexander B; Nanni, Emilio A; Herzfeld, Judith; Griffin, Robert G; Temkin, Richard J

    2012-08-01

    We describe the design and implementation of a novel tunable 250 GHz gyrotron oscillator with >10 W output power over most of a 3 GHz band and >35 W peak power. The tuning bandwidth and power are sufficient to generate a >1 MHz nutation frequency across the entire nitroxide EPR lineshape for cross effect DNP, as well as to excite solid effect transitions utilizing other radicals, without the need for sweeping the NMR magnetic field. Substantially improved tunability is achieved by implementing a long (23 mm) interaction cavity that can excite higher order axial modes by changing either the magnetic field of the gyrotron or the cathode potential. This interaction cavity excites the rotating TE(₅,₂,q) mode, and an internal mode converter outputs a high-quality microwave beam with >94% Gaussian content. The gyrotron was integrated into a DNP spectrometer, resulting in a measured DNP enhancement of 54 on the membrane protein bacteriorhodopsin. PMID:22743211

  6. A 250 GHz gyrotron with a 3 GHz tuning bandwidth for dynamic nuclear polarization

    Barnes, Alexander B.; Nanni, Emilio A.; Herzfeld, Judith; Griffin, Robert G.; Temkin, Richard J.

    2012-08-01

    We describe the design and implementation of a novel tunable 250 GHz gyrotron oscillator with >10 W output power over most of a 3 GHz band and >35 W peak power. The tuning bandwidth and power are sufficient to generate a >1 MHz nutation frequency across the entire nitroxide EPR lineshape for cross effect DNP, as well as to excite solid effect transitions utilizing other radicals, without the need for sweeping the NMR magnetic field. Substantially improved tunability is achieved by implementing a long (23 mm) interaction cavity that can excite higher order axial modes by changing either the magnetic field of the gyrotron or the cathode potential. This interaction cavity excites the rotating TE5,2,q mode, and an internal mode converter outputs a high-quality microwave beam with >94% Gaussian content. The gyrotron was integrated into a DNP spectrometer, resulting in a measured DNP enhancement of 54 on the membrane protein bacteriorhodopsin.

  7. High power operation of Gaussian beam gyrotron with CVD diamond window for JT-60U

    A 110 GHz-Gaussian beam output gyrotron with CVD (Chemical Vapor Deposition) diamond window was developed for the electron cyclotron heating and current drive on JT-60U. A stable Gaussian output beam power of 1.1 MW-0.1 s was obtained with the efficiency of 39% with depressed collector operation. Due to Gaussian beam output from the gyrotron, the coupling efficiency to HE11 mode in the mirror optical unit was 94%. Moreover, the transmission efficiency of 89% for HE11 mode was performed at the power level of 1 MW on the 40 m-transmission test line of φ31.751 mm corrugated waveguide and 8-miter bends included 1-pair of polarizer. The gyrotron and transmission line were installed into JT-60U system and 0.6 MW-0.3 s power was successfully injected into JT-60U plasmas as an initial operation

  8. Control of the Superconducting Magnets current Power Supplies of the TJ-II Gyrotrons

    The TJ-II ECRH heating system consists of two gyrotrons, which can deliver a maximum power of 300 kW at a frequency of 53.2 GHz. Another 28 GHz gyrotron is going to be used in the Bernstein waves heating system. In order to get the required frequency, the gyrotrons need and homogeneous magnetic field of several tesla, which is generated by a superconducting coil field by a current source. This document describes the current source control as well as the high precision ammeters control. These ammeters measure the current in the superconducting coils. The user interface and the programming of the control system are described. The communication between devices is also explained. (author) 9 Refs

  9. Commissioning a Megawatt-class Gyrotron with Collector Potential Depression

    Lohr, J.; Cengher, M.; Gorelov, Y. A.; Ponce, D.; Prater, R.

    2013-10-01

    A 110 GHz depressed collector gyrotron has been installed on the DIII-D tokamak. The commissioning process rapidly achieved operation at full parameters, 45 A and 94 kV total voltage, with 29 kV depression. Although short pulse, 2 ms, factory testing demonstrated 1.2 MW at 41% electrical efficiency, long pulse testing at DIII-D achieved only 33% efficiency at full power parameters, for pulse lengths up to 10 s. Maximum generated power was ~950 kW, considerably below the 1.2 MW target. During attempts to increase the power at 5 s pulse length, it was noted that the collector cooling water was boiling. This led to the discovery that 14 of the 160 cooling channels in the collector had been blocked by braze material during manufacture of the tube. The locations of blocked channels were identified using infrared imaging of the outside of the collector during rapid changes in the cooling water temperature. Despite these difficulties, the rf beam itself was of very high quality and the stray rf found calorimetrically in the Matching Optics Unit, which couples the Gaussian rf beam to the waveguide, was only 2% of the generated power, about half that of our previous best quality high power beam. Details of the power measurements and collector observations will be presented. Work supported by the US DOE under DE-FC02-04ER54698.

  10. Status of the 2 MW, 170 GHz coaxial cavity gyrotron for ITER

    Full text: A 170 GHz coaxial cavity gyrotron with 2 MW output power in continuous wave (CW) operation is under development in cooperation between European research centres together with European industry. A first industrial prototype of such a gyrotron has already been fabricated and delivered to CRPP Lausanne, where a suitable test facility has been constructed. Due to a delay in fabrication the delivery of the gyrotron magnet is expected in May 2007. Thus experimental tests are expected for the second half of this year. In parallel to the industrial activities, experimental operation with a short pulse (∼ few ms) 170 GHz coaxial gyrotron ('pre-prototype') which uses the same main components as designed for the industrial tube has been continued. The mechanism of parasitic low frequency (LF) oscillations around 260 MHz has been identified. Based on this identification, small modifications of the geometry of the coaxial insert have been made. As a result the starting current for the LF oscillations has been increased by a factor of about 3 causing a strong reduction of the LF amplitude. Measurements with a prototype of a microwave load, which has been designed and fabricated for operation with the 2 MW prototype tube, have been performed. In addition to the distribution of the microwave power absorbed on the wall, the amount of power reflected back into the gyrotron has been measured and its influence on gyrotron performance has been investigated. The performance of the quasi optical (q.o.) RF output system presently installed in the industrial prototype tube is insufficient, mainly because of the low Gaussian content of the RF output beam. As a first step a new launcher with a different wall corrugation and a new adapted phase correcting mirror has been designed and fabricated. According to simulations an increase of the Gaussian content to about 87% is expected. This q.o. RF output system has been installed in the pre-prototype tube for performing hot

  11. Infrared measurements of the synthetic diamond window of a 110 GHz high power Gyrotron

    Artificially grown diamond has extremely low absorption for microwaves in the millimeter wave range, making this material an attractive candidate for output windows on high power gyrotrons. Several windows have failed in this application due to higher than expected losses. Infrared measurements of the window temperature on a high power gyrotron operating at 110 GHz have been performed. The peak central temperature and time to equilibrium during the rf pulse were consistent with the low loss properties of the material determined from low power cavity measurements

  12. Gyrotron with a sectioned cavity based on excitation of a far-from-cutoff operating mode

    A typical problem of weakly relativistic low-power gyrotrons (especially in the case of operation at high cyclotron harmonics) is the use of long cavities ensuring extremely high diffraction Q-factors for the operating near-cutoff waves. As a result, a great share of the rf power radiated by electrons is spent in Ohmic losses. In this paper, we propose to use a sectioned cavity with π-shifts of the wave phase between sections. In such a cavity, a far-from-cutoff axial mode of the operating cavity having a decreased diffraction Q-factor is excited by the electron beam in a gyrotron-like regime

  13. High-power and long-pulse gyrotron development in JAERI

    A maximum pulse duration of 1.3s was achieved with a power of 410kW at a frequency of 110GHz and a maximum power of 550kW was obtained with short-pulse operations (ca. 2ms). The oscillation mode of the gyrotron is the TE22,2 whispering gallery mode, which is transformed into a gaussian-like beam by a built-in quasi-optical mode converter. R.f. power is extracted through a sapphire double-disc window cooled by FC-75. In long-pulse operation, no damage was observed in the gyrotron. ((orig.))

  14. Gyrotrons for High-Power Terahertz Science and Technology at FIR UF

    Idehara, Toshitaka

    2016-01-01

    In this paper, we present the recent progress in the development of a series of gyrotrons at FIR UF that have opened the road to many novel applications in the high-power Terahertz science and technology. The current status of the research in this actively developing field is illustrated by the most representative examples in which the developed gyrotrons are used as powerful and frequency tunable sources of coherent radiation operating in a CW regime. Among them are high-precision spectroscopic techniques (most notably DNP-NMR, ESR, XDMR, and studies of the hyperfine splitting of the energy levels of positronium), treatment and characterization of advanced materials, new medical technologies.

  15. Broadband continuously frequency tunable gyrotron for 600 MHz DNP-NMR spectroscopy

    A broadband continuously frequency tunable gyrotron with a triode-type magnetron injection gun was developed as power source for analysis of protein structures. The TE7,3 oscillation mode was selected to avoid mode competitions in the high magnetic field side. Axial modes of the TE7,3,-10 were sequentially excited by changing the cavity magnetic field, and frequency tuning of about 4 GHz around 395 GHz was observed with output power greater than 50 W. The frequency also varied about 1 GHz as the anode-cathode voltage varied. Thus, the broadest tuning bandwidth in the 400 GHz band gyrotrons was achieved. (author)

  16. Suppression and nonlinear excitation of parasitic modes in second harmonic gyrotrons operating in a very high order mode

    In recent years, there was an active development of high-power, sub-terahertz (sub-THz) gyrotrons for numerous applications. For example, a 0.67 THz gyrotron delivering more than 200 kW with about 20% efficiency was developed. This record high efficiency was achieved because the gyrotron operated in a high-order TE31,8-mode with the power of ohmic losses less than 10% of the power of outgoing radiation. That gyrotron operated at the fundamental cyclotron resonance, and a high magnetic field of about 27 T was created by a pulse solenoid. For numerous applications, it is beneficial to use gyrotrons at cyclotron harmonics which can operate in available cryomagnets with fields not exceeding 15 T. However, typically, the gyrotron operation at harmonics faces severe competition from parasitic modes at the fundamental resonance. In the present paper, we consider a similar 0.67 THz gyrotron designed for operation in the same TE31,8-mode, but at the second harmonic. We focus on two nonlinear effects typical for interaction between the fundamental and second harmonic modes, viz., the mode suppression and the nonlinear excitation of the mode at the fundamental harmonic by the second harmonic oscillations. Our study includes both the analytical theory and numerical simulations performed with the self-consistent code MAGY. The simulations show that stable second harmonic operation in the TE31,8 mode is possible with only modest sacrifice of efficiency and power

  17. High-power 140 GHz ECRH experiments at the W7-AS stellarator

    ECRH was combined with NBI at moderate and high densities with on- and off-axis heating. Density control was achieved for combined heating in long pulse operation despite the beam fueling in contrast to discharges with pure NBI heating. Particle confinement degradation by profile changes inferred by ECRH is discussed as a possible mechanism. The impurity confinement is strongly affected and is discussed for on- and off-axis combined heating conditions

  18. Recent results with 140 GHz ECRH at the W7-AS stellarator

    H-mode transitions, which are well known from tokamaks were observed in W7-AS. The operational window for the H-mode is discussed. The basic features of the Stellarator H-mode were reported in previous papers. Here we concentrate on the influence of gas puffing on the H-transitions and heat wave experiments. Combined heating experiments with NBI were performed, which is inherently related to high density operation. Typical high-power NBI-heated plasmas in W7-AS are non-stationary, because beam particle fuelling and recycling causes a steady density rise. Under combined heating conditions, however, the density can be controlled despite the beam fuelling and a strong impact on the impurity confinement was found. (orig.)

  19. Low Noise Amplifiers for 140 Ghz Wide-Band Cryogenic Receivers

    Larkoski, Patricia V.; Kangaslahti, Pekka; Samoska, Lorene; Lai, Richard; Sarkozy, Stephen

    2013-01-01

    We report S-parameter and noise measurements for three different Indium Phosphide 35-nanometer-gate-length High Electron Mobility Transistor (HEMT) Low Noise Amplifier (LNA) designs operating in the frequency range centered on 140 gigahertz. When packaged in a Waveguide Rectangular-6.1 waveguide housing, the LNAs have an average measured noise figure of 3.0 decibels - 3.6 decibels over the 122-170 gigahertz band. One LNA was cooled to 20 degrees Kelvin and a record low noise temperature of 46 Kelvin, or 0.64 decibels noise figure, was measured at 152 gigahertz. These amplifiers can be used to develop receivers for instruments that operate in the 130-170 gigahertz atmospheric window, which is an important frequency band for ground-based astronomy and millimeter-wave imaging applications.

  20. Continuous-Wave Operation of a Frequency-Tunable 460-GHz Second-Harmonic Gyrotron for Enhanced Nuclear Magnetic Resonance

    Torrezan, Antonio C.; Han, Seong-Tae; Mastovsky, Ivan; Shapiro, Michael A; Sirigiri, Jagadishwar R.; Temkin, Richard J.; Griffin, Robert G.; Barnes, Alexander B.

    2010-01-01

    The design, operation, and characterization of a continuous-wave (CW) tunable second-harmonic 460-GHz gyrotron are reported. The gyrotron is intended to be used as a submillimeter-wave source for 700-MHz nuclear magnetic resonance experiments with sensitivity enhanced by dynamic nuclear polarization. The gyrotron operates in the whispering-gallery mode TE11,2 and has generated 16 W of output power with a 13-kV 100-mA electron beam. The start oscillation current measured over a range of magnet...

  1. Time-domain self-consistent theory of frequency-locking regimes in gyrotrons with low-Q resonators

    A time-domain theory of frequency-locking gyrotron oscillators with low-Q resonators has been developed. The presented theory is based on the description of wave propagation by a parabolic equation taking into account the external signal by modification of boundary conditions. We show that the developed model can be effectively used for simulations of both single- and multi-mode operation regimes in gyrotrons driven by an external signal. For the case of low-Q resonators typical for powerful gyrotrons, the external signal can influence the axial field profile inside the interaction space significantly and, correspondingly, the value of the electron orbital efficiency

  2. To the theory of high-power gyrotrons with uptapered resonators

    Dumbrajs, O.; Nusinovich, G. S.

    2010-05-01

    In high-power gyrotrons it is desirable to combine an optimal resonator length with the optimal value of the resonator quality factor. In resonators with the constant radius of the central part, the possibilities of this combination are limited because the quality factor of the resonator sharply increases with its length. Therefore the attempts to increase the length for maximizing the efficiency leads to such increase in the quality factor which makes the optimal current too small. Resonators with slightly uptapered profiles offer more flexibility in this regard. In such resonators, one can separate optimization of the interaction length from optimization of the quality factor because the quality factor determined by diffractive losses can be reduced by increasing the angle of uptapering. In the present paper, these issues are analyzed by studying as a typical high-power 17 GHz gyrotron which is currently under development in Europe for ITER (http://en.wikipedia.org/wiki/ITER). The effect of a slight uptapering of the resonator wall on the efficiency enhancement and the purity of the radiation spectrum in the process of the gyrotron start-up and power modulation are studied. Results show that optimal modification of the shape of a slightly uptapered resonator may result in increasing the gyrotron power from 1052 to 1360 kW.

  3. To the theory of high-power gyrotrons with uptapered resonators

    In high-power gyrotrons it is desirable to combine an optimal resonator length with the optimal value of the resonator quality factor. In resonators with the constant radius of the central part, the possibilities of this combination are limited because the quality factor of the resonator sharply increases with its length. Therefore the attempts to increase the length for maximizing the efficiency leads to such increase in the quality factor which makes the optimal current too small. Resonators with slightly uptapered profiles offer more flexibility in this regard. In such resonators, one can separate optimization of the interaction length from optimization of the quality factor because the quality factor determined by diffractive losses can be reduced by increasing the angle of uptapering. In the present paper, these issues are analyzed by studying as a typical high-power 17 GHz gyrotron which is currently under development in Europe for ITER (http://en.wikipedia.org/wiki/ITER). The effect of a slight uptapering of the resonator wall on the efficiency enhancement and the purity of the radiation spectrum in the process of the gyrotron start-up and power modulation are studied. Results show that optimal modification of the shape of a slightly uptapered resonator may result in increasing the gyrotron power from 1052 to 1360 kW.

  4. Start-Up Scenario in Gyrotrons with a Nonstationary Microwave-Field Structure

    Nusinovich, G. S.; Yeddulla, M.; Antonsen, T. M., Jr.; Vlasov, A. N.

    2006-03-01

    Megawatt class gyrotrons operate in very high-order modes. Therefore, control of a gyrotron oscillator’s start-up is important for excitation of the desired mode in the presence of the many undesired modes. Analysis of such scenario using the self-consistent code MAGY [M. Botton , IEEE Trans. Plasma Sci. 26,ITPSBD0093-3813 882 (1998)10.1109/27.700860] reveals that during start-up not only mode amplitudes vary in time, but also their axial structure can be time dependent. Simulations done for a 1.5 MW gyrotron show that the excitation of a single operating TE22,6 mode can exhibit a sort of intermittency when, first, it is excited as a mode whose axial structure extends outside the interaction cavity, then it ceases and then reappears as a mode mostly localized in the cavity. This phenomenon makes it necessary to analyze start-up scenarios in such gyrotrons with the use of codes that account for the possible evolution of field profiles.

  5. Performance history and upgrades for the DIII-D gyrotron complex

    The gyrotron installation on the DIII-D tokamak has been in operation at the second harmonic of the electron cyclotron resonance since the mid-1990s. Prior to that a large installation of ten 60 GHz tubes was operated at the fundamental resonance. The system has been upgraded regularly and is an everyday tool for experiments on DIII-D

  6. A Fully-Sealed Carbon-Nanotube Cold-Cathode Terahertz Gyrotron.

    Yuan, Xuesong; Zhu, Weiwei; Zhang, Yu; Xu, Ningsheng; Yan, Yang; Wu, Jianqiang; Shen, Yan; Chen, Jun; She, Juncong; Deng, Shaozhi

    2016-01-01

    Gigahertz to terahertz radiation sources based on cold-cathode vacuum electron technology are pursued, because its unique characteristics of instant switch-on and power saving are important to military and space applications. Gigahertz gyrotron was reported using carbon nanotube (CNT) cold-cathode. It is reported here in first time that a fully-sealed CNT cold-cathode 0.22 THz-gyrotron is realized, typically with output power of 500 mW. To achieve this, we have studied mechanisms responsible for CNTs growth on curved shape metal surface, field emission from the sidewall of a CNT, and crystallized interface junction between CNT and substrate material. We have obtained uniform growth of CNTs on and direct growth from cone-cylinder stainless-steel electrode surface, and field emission from both tips and sidewalls of CNTs. It is essential for the success of a CNT terahertz gyrotron to have such high quality, high emitting performance CNTs. Also, we have developed a magnetic injection electron gun using CNT cold-cathode to exploit the advantages of such a conventional gun design, so that a large area emitting surface is utilized to deliver large current for electron beam. The results indicate that higher output power and higher radiation frequency terahertz gyrotron may be made using CNT cold-cathode electron gun. PMID:27609247

  7. Simulation tools for computer-aided design and numerical investigations of high-power gyrotrons

    Modelling and simulation are essential tools for computer-aided design (CAD), analysis and optimization of high-power gyrotrons used as radiation sources for electron cyclotron resonance heating (ECRH) and current drive (ECCD) of magnetically confined plasmas in the thermonuclear reactor ITER. In this communication, we present the current status of our simulation tools and discuss their further development.

  8. Development program for a 200 kW, cw gyrotron. Final report

    Development of a millimeter-wave device to produce 200 kW of continuous wave power at 60 GHz is described. The device, a gyrotron oscillator, is intended for electron-cyclotron heating of fusion plasmas. The design philosophy is herein discussed and experimental results, both diagnostic and long pulse, are given

  9. Frequency-Based Investigation of Charge Neutralization Processes and Thermal Cavity Expansion in Gyrotrons

    Schlaich, Andreas; Wu, Chuanren; Pagonakis, Ioannis; Avramidis, Konstantinos; Illy, Stefan; Gantenbein, Gerd; Jelonnek, John; Thumm, Manfred

    2015-09-01

    During the first hundred milliseconds, the frequency and RF output power of long pulse operating gyrotrons undergo deterministic variation. This well-known behavior is caused by the thermal expansion of the cavity and internal electrostatic processes related to the ionization of residual gas. A macroscopic analytical investigation of the gas conditions in modern gyrotrons indicates that ionization processes are unlikely to influence the overall internal gas pressure. In combination with electrostatic potential considerations, it was found that the beam depression voltage is not fully neutralized; in the case of W7-X gyrotrons, a maximum value of about 60 % neutralization is expected, in conflict with the common assumption of full neutralization in steady state. Using experimentally measured frequency shifts and the Evridiki gyrotron interaction simulation code, a fitting process was employed to further investigate these effects. The results are in very good agreement with the theoretical predictions and allow a separation of the time constants of the two processes causing the frequency tuning.

  10. Performance History and Upgrades for the DIII-D Gyrotron Complex

    Lohr J.

    2015-01-01

    Full Text Available The gyrotron installation on the DIII-D tokamak has been in operation at the second harmonic of the electron cyclotron resonance since the mid-1990s. Prior to that a large installation of ten 60 GHz tubes was operated at the fundamental resonance. The system has been upgraded regularly and is an everyday tool for experiments on DIII-D.

  11. 5 MW CW supply system for the ITER gyrotrons Test Facility

    ECH (Electron Cyclotron Heating) for ITER will deliver into the plasma 20 MW of RF power. The procurement of the RF sources will be shared equally between the three following partners: Europe, Japan and Russia. Moreover, Europe decided to develop a RF source capable of 2 MW CW of RF power, based on the design of a coaxial gyrotron with a depressed collector. In order to be able to develop and test these RF sources, a Test Facility (TF) has been built at the CRPP premises in Lausanne (CH). The present paper will first remind the main operation conditions considered to test safely a gyrotron. The power supplies parameters allowing to fulfill these conditions will be reviewed. The core of the paper content will describe the newly installed Main High Voltage Power Supply (MHVPS), to be connected to the gyrotron cathode and capable of -60 kV/80 A-CW. The principle, the characteristics, the on-site test results will be described at the light of the requirements imposed by the gyrotron testing. Particular aspects of the installation and commissioning on-site will be highlighted in comparison with the ITER environment. The synchronized operation of the MHVPS and the BPS (Body Power Supply) on dummy load, piloted through the TF remote control, will be presented and commented. Since the TF supply structure has been built integrating the particular conditions and requirements expected for ITER, a conclusion will summarize the performances obtained at the light of these criteria.

  12. Design of a second cyclotron harmonic gyrotron oscillator with photonic band-gap cavity

    A photonic band-gap cavity (PBGC) gyrotron with a frequency of about 98 GHz is designed. Theoretical analyses and numerical calculations are made for the PBGC operating at fundamental and second cyclotron harmonic with a TE34 waveguide mode to demonstrate the beam-wave interaction. The results show that mode competition is successfully eliminated in the PBGC using mode selectivity and choosing the appropriate operating parameters. As a result, the second harmonic PBGC gyrotron operating at TE34 mode achieves a higher output efficiency than that of the fundamental. It is also demonstrated that, in the case of the chosen parameters for TE34 waveguide mode, the use of PBG structure in the second harmonic gyrotron brings about not only a lower operating B-field but also a weaker mode competition. The results show that the high-order electromagnetic mode can be developed to interact with the high cyclotron harmonic using the selectivity of the PBGC, which gives an encouraging outlook for the development of high-harmonic gyrotrons.

  13. Operation of the 118 GHz very long pulse gyrotron for the ECRH experiment on Tore Supra

    An ECRH (Electron Cyclotron Resonance Heating) system capable of delivering 2.4 MW CW is presently under development at CEA (Commissariat a l'Energie Atomique) Cadarache, for the Tore Supra experiment, to provide plasma heating and current drive by Electron Cyclotron Resonance interaction. The generator is planned to consist of six gyrotrons TH 1506 B developed thanks to a collaboration between TED (Thales Electron Devices) and European laboratories; the gyrotrons are specified to provide RF waves with a frequency of 118 GHz and a unit power of 400 kW (500 kW) for a pulse length up to 600 s (5 s). At present, one prototype and one series tube are installed, which were first tested on dummy loads and then on plasma, individually and together. Even though the specification was not fulfilled, a record pulse of 300 kW during 110 s was achieved by the series gyrotron; the pulse was stopped by a strong degassing within the tube, due to the overheating of the internal mirror box. This seems to be the consequence of spurious frequencies generated in the injector. New upgraded tubes will be developed by TED and the next gyrotron is planned to be delivered during summer 2003. At the end of 2001, 800 kW generated by the two existing gyrotrons were coupled to the plasma, using various polarizations and injection angles allowed by the mobile mirrors of the antenna; the power was modulated at frequencies between 2 Hz and 25 Hz, on both tubes. As a result, about 50 ECRH pulses have successfully been coupled to the plasma, leading to a first comparison of theoretical deposition profiles with the experimental profiles observed through the ECE diagnostic. (authors)

  14. 1 MW and long pulse operation of Gaussian beam output gyrotron with CVD diamond window for fusion devices

    A 110 GHz-Gaussian beam output gyrotron with chemical vapor deposition (CVD) diamond window was developed for electron cyclotron heating and current drive on JT-60U. A stable Gaussian output beam power of 1.0 MW for 2 s was obtained with depressed collector operation. The temperature at the center of the diamond window was stabilized at the ΔT∼25 K. Gaussian beam output from the gyrotron remarkably improved the coupling efficiency to the HE11 mode in the transmission waveguide. 94% of the gyrotron output power was coupled to the corrugated waveguide of 31.75 mm in diameter, via a matching optics unit with two mirrors. A combination of the Gaussian output and the diamond window are indispensable for high power gyrotron operation at more than 1 MW and efficient coupling to the transmission line

  15. Relief Creation on Molybdenum Plates in Discharges Initiated by Gyrotron Radiation in Metal-Dielectric Powder Mixtures

    Skvortsova, N. N.; Stepakhin, V. D.; Malakhov, D. V.; Sorokin, A. A.; Batanov, G. M.; Borzosekov, V. D.; Glyavin, M. Yu.; Kolik, L. V.; Konchekov, E. M.; Letunov, A. A.; Petrov, A. E.; Ryabikina, I. G.; Sarksyan, K. A.; Sokolov, A. S.; Smirnov, V. A.; Kharchev, N. K.

    2016-02-01

    We show the possibility of creating a metal microcrystalline relief (micro- and nanosized) on molybdenum plates in a plasma gas-phase discharge initiated by gyrotron radiation in molybdenum-dielectric powder mixtures.

  16. Design studies of quasioptical launcher for a 170 GHz, 1.5 MW CW gyrotron for ITER project

    The first hand design of Quasi-optical launcher for 170 GHz, 1.5 MW CW gyrotron with TE36,10 is stated in present paper. The proposed launcher converts cavity mode (TE36,10) into free space TEM mode for easy transmission over transmission line. RF-output with 99.7% Gaussian fit profile is achieved with 99.9% energy conversion. Results support the bright, single Gaussian beam output from gyrotron. (author)

  17. Effects of electron beam parameters and velocity spread on radio frequency output of a photonic band gap cavity gyrotron oscillator

    Singh, Ashutosh, E-mail: asingh.rs.ece@iitbhu.ac.in [Faculty of Physical Sciences, Institute of Natural Sciences and Humanities, Shri Ramswaroop Memorial University, Lucknow-Deva Road, Uttar Pradesh 225003 (India); Center of Research in Microwave Tubes, Department of Electronics Engineering, Indian Institute of Technology (Banaras Hindu University), Varanasi 221005 (India); Jain, P. K. [Center of Research in Microwave Tubes, Department of Electronics Engineering, Indian Institute of Technology (Banaras Hindu University), Varanasi 221005 (India)

    2015-09-15

    In this paper, the effects of electron beam parameters and velocity spread on the RF behavior of a metallic photonic band gap (PBG) cavity gyrotron operating at 35 GHz with TE{sub 041}–like mode have been theoretically demonstrated. PBG cavity is used here to achieve a single mode operation of the overmoded cavity. The nonlinear time-dependent multimode analysis has been used to observe the beam-wave interaction behavior of the PBG cavity gyrotron, and a commercially available PIC code “CST Particle Studio” has been reconfigured to obtain 3D simulation results in order to validate the analytical values. The output power for this typical PBG gyrotron has been obtained ∼108 kW with ∼15.5% efficiency in a well confined TE{sub 041}–like mode, while all other competing modes have significantly low values of power output. The output power and efficiency of a gyrotron depend highly on the electron beam parameters and velocity spread. The influence of several electron beam parameters, e.g., beam voltage, beam current, beam velocity pitch factor, and DC magnetic field, on the PBG gyrotron operations has been investigated. This study would be helpful in optimising the electron beam parameters and estimating accurate RF output power of the high frequency PBG cavity based gyrotron oscillators.

  18. Gyrotron: an application of the relativistic bunching of electrons to the generation of intense millimeter microwave radiation

    The cyclotron maser or gyrotron is capable of generating high power microwaves at millimeter wave frequencies for applications in fusion heating, radar astronomy and communications. Analytic and numerical simulation models are developed that describe the behavior of these devices under realistic laboratory conditions including the effects of circuit geometry, beam thermal spread, and mode competition. In Chapter 2, a generalized linear theory for the gyrotron is presented in the form of an integro-differential equation that can be solved within various circuit geometries thus describing gyro-amplifiers, gyro-oscillatory and gyroklystrons. In Chapter 3 a complete description of a finite size electromagnetic particle simulation model is presented that describes gyrotrons operating in a TE/sub mn/ waveguide mode. In Chapter 4 simulations and theoretical analysis are made of gyrotron amplifiers operating in the TE/sub 01/ mode. In Chapter 5 the linear eigenmodes and eigenfrequencies of gyrotron oscillators are examined. In Chapter 6 the experimental development of a GHz gyrotron is presented. Theoretical and numerical predictions of oscillation thresholds and efficiencies compare favorably with experimental data

  19. Effects of electron beam parameters and velocity spread on radio frequency output of a photonic band gap cavity gyrotron oscillator

    In this paper, the effects of electron beam parameters and velocity spread on the RF behavior of a metallic photonic band gap (PBG) cavity gyrotron operating at 35 GHz with TE041–like mode have been theoretically demonstrated. PBG cavity is used here to achieve a single mode operation of the overmoded cavity. The nonlinear time-dependent multimode analysis has been used to observe the beam-wave interaction behavior of the PBG cavity gyrotron, and a commercially available PIC code “CST Particle Studio” has been reconfigured to obtain 3D simulation results in order to validate the analytical values. The output power for this typical PBG gyrotron has been obtained ∼108 kW with ∼15.5% efficiency in a well confined TE041–like mode, while all other competing modes have significantly low values of power output. The output power and efficiency of a gyrotron depend highly on the electron beam parameters and velocity spread. The influence of several electron beam parameters, e.g., beam voltage, beam current, beam velocity pitch factor, and DC magnetic field, on the PBG gyrotron operations has been investigated. This study would be helpful in optimising the electron beam parameters and estimating accurate RF output power of the high frequency PBG cavity based gyrotron oscillators

  20. Development of the Multifrequency Gyrotron FU CW GV with Gaussian Beam Output

    Tatematsu, Yoshinori; Yamaguchi, Yuusuke; Ichioka, Ryoichi; Kotera, Masaki; Saito, Teruo; Idehara, Toshitaka

    2015-08-01

    Gyrotron FU CW GV has been developed as a multifrequency gyrotron for operation over the frequency range from 162 to 265 GHz at frequencies separated by steps of approximately 10 GHz. The oscillation modes were selected; the radii of the caustic surfaces for the electromagnetic waves of the modes had similar values in the waveguide, and it was therefore expected that these modes would be converted into Gaussian beams by a mode converter. In reality, more than ten modes oscillated and the Gaussian-like beams were radiated. A double-disk window with variable spacing maintains the transmittance through the window at a high level over a wide range of frequencies. Using this window, output powers of more than 1 kW were observed for almost all the expected modes.

  1. Development of Gyrotron and JT-60U EC heating system for fusion reactor

    The progress of ECH technology, for ITER and JT-60U tokamak, are presented. In the development of gyrotron, 0.9MW/9.2sec, 0.5MW/30sec, 0.3MW/60sec, etc. have been demonstrated at 170GHz. At 110GHz, 1.3MW/1.2sec, 1.2MW/4.1sec, 1MW/5sec were obtained. It is found that the reduction of the stray radiation and the enhancement of cooling capability are keys for CW operation. Four 110GHz gyrotrons are under operation in the ECH system of JT-60U. The power up to approximately 3MW/2.7sec was injected into the plasma through the poloidally movable mirrors, and contributed to the electron heating up to 26keV(ne∼0.5x1013cm-3), and the suppression of the neo-classical tearing mode. (author)

  2. Comparison of Different Methods for Calculating Gyrotron Quasi-Optical Mode Converters

    Gashturi, A. P.; Chirkov, A. V.; Denisov, G. G.; Paveliev, A. B.

    2013-01-01

    This paper presents the use of combination of three methods for calculation and synthesis of high-efficiency microwave mode converters, such as radiators of gyrotrons. The analytical method yields immediate estimates of mode converter dimensions, the Scalar Integral Equation (SIE) allows one to synthesize efficiently the optimal profile of the mode converter, and the most accurate Electric Field Integral Equation (EFIE) is used to check all transmission characteristics of the converter including calculations of reflection and cross-polarization. The combination of these three methods is an optimal for the mode converter design. Just so the launcher was designed for a quasi-optical mode converter used in the 60 GHz gyrotron in the TE7,3 operating mode. The simulation results agree well with the measured data. The paper also presents for the first time an accurate derivation of the SIE method.

  3. The gyrotron - a key component of high-power microwave transmitters

    Radio-frequency heating of dense plasmas is a central feature of numerous experiments currently being carried out in fusion research facilities the world over. To heat the plasma to a thermonuclear state, microwave transmitters with power outputs of 1 MW at frequencies from a few GHz to more than 100 GHz are required. The only commercially available r.f. tube capable of generating continuous-wave powers of more than 100 kW at frequencies above 10 GHz is the gyrotron. Work is being carried out on the development of a quasi-optical gyroklystron (120-150 GHz/>200 kW) for electron cyclotron resonant heating (ECRH) of fusion plasmas. A prototype of a cylindrical gyromonotron for lower hybrid heating (LHH) at 8 GHz has already been built and successfully tested. The operating principles and design of the two types of gyrotron are described. (Auth.)

  4. Problem-Oriented Simulation Packages and Computational Infrastructure for Numerical Studies of Powerful Gyrotrons

    Damyanova, M.; Sabchevski, S.; Zhelyazkov, I.; Vasileva, E.; Balabanova, E.; Dankov, P.; Malinov, P.

    2016-05-01

    Powerful gyrotrons are necessary as sources of strong microwaves for electron cyclotron resonance heating (ECRH) and electron cyclotron current drive (ECCD) of magnetically confined plasmas in various reactors (most notably ITER) for controlled thermonuclear fusion. Adequate physical models and efficient problem-oriented software packages are essential tools for numerical studies, analysis, optimization and computer-aided design (CAD) of such high-performance gyrotrons operating in a CW mode and delivering output power of the order of 1-2 MW. In this report we present the current status of our simulation tools (physical models, numerical codes, pre- and post-processing programs, etc.) as well as the computational infrastructure on which they are being developed, maintained and executed.

  5. Development and simulation of RF components for high power millimeter wave gyrotrons

    To test gyrotron RF components, efficient low-power generators for rotating high-order modes of high purity are necessary. Designs of generators for the TE15,3 mode at 84 GHz and for the TE31,8 mode at 168 GHz are presented and some preliminary test results are discussed. In addition, Toshiba gyrotron cavities at 168 GHz were analyzed for leakage of RF power in the beam tunnel. To decrease RF power leakage, the declination angle of the cut-off cavity cross section has to be decreased. A TE15,3 waveguide nonlinear uptaper is analyzed at 84 GHz as well as 168 GHz uptapers. Since the calculated conversion losses are slightly higher than designed value, an optimization of those uptapers may be required. (author)

  6. High-frequency gyrotrons and their application to tokamak plasma heating

    A comprehensive analysis of high frequency (100 to 200 GHz) and high power (> 100 kW) gyrotrons has been conducted. It is shown that high frequencies will be required in order for electron cyclotron radiation to propagate to the center of a compact tokamak power reactor. High power levels will be needed in order to ignite the plasma with a reasonable number of gyrotron units. In the first part of this research, a set of analytic expressions, valid for all TE cavity modes and all harmonics, is derived for the starting current and frequency detuning using the Vlasov-Maxwell equations in the weakly relativistic limit. The use of an optical cavity is also investigated

  7. Development of gyrotron and JT-60U EC heating system for fusion reactor

    The progress of ECH technology, for ITER and JT-60U tokamak, are presented. In the development of gyrotron, 0.9MW/9.2sec, 0.5MW/30sec, 0.3MW/60sec, etc. have been demonstrated at 170GHz. At 110GHz, 1.3MW/1.2sec, 1.2MW/4. 1sec. 1MW/5sec were obtained. It is found that the reduction of the stray radiation and the enhancement of cooling capability are keys for CW operation. Four 110GHz gyrotrons are under operation in the ECH system of JT-60U. The power up to approximately 3MW/2.7sec was injected into the plasma through the poloidally movable mirrors, and contributed to the electron heating up to 26keV(ne∼0.5x1013cm-3), and the suppression of the neo-classical tearing mode. (author)

  8. A 250 GHz Gyrotron with a 3 GHz Tuning Bandwidth for Dynamic Nuclear Polarization

    Barnes, Alexander B.; Nanni, Emilio A.; Herzfeld, Judith; Griffin, Robert G.; Temkin, Richard J.

    2012-01-01

    We describe the design and implementation of a novel tunable 250 GHz gyrotron oscillator with >10 W output power over most of a 3 GHz band and >35 W peak power. The tuning bandwidth and power are sufficient to generate a >1 MHz nutation frequency across the entire nitroxide EPR lineshape for cross effect DNP, as well as to excite solid effect transitions utilizing other radicals, without the need for sweeping the NMR magnetic field. Substantially improved tunability is achieved by implementin...

  9. Feasibility of ion temperature measurement with a gyrotron scattering alpha particle diagnostic

    Collective Thomson scattering can be used to diagnose localized ion temperature as well as alpha particle velocity distribution and density in a D-T burning tokamak. With one diagnostic beam a simultaneous, but independent, measure of the bulk ion temperature and alpha particle parameters can be made. Use of a long pulse, millimeter-wave gyrotron offers a significant margin in signal to noise ratio capability (√Δftau > 1000) not previously possible with lasers. 9 refs., 2 figs

  10. Final Report for 'Gyrotron Design and Evaluation using New Particle-in-Cell Capability'

    ITER will depend on high power CW gyrotrons to deliver power to the plasma at ECR frequencies. However, gyrotrons can suffer from undesirable low frequency oscillations (LFO's) which are known to interfere with the gun-region diagnostics and data collection, and are also expected to produce undesirable energy and velocity spread in the beam. The origins and processes leading to these oscillations are poorly understood, and existing gyrotron R and D tools, such as static gun solvers and interaction region models, are not designed to look at time-dependant oscillatory behavior. We have applied a time-domain particle-in-cell method to investigate the LFO phenomenon. Our company is at the forefront of smooth-curved-boundary treatment of the electromagnetic fields and particle emission surfaces, and such methods are necessary to simulate the adiabatically trapped and reflected electrons thought to be driving the oscillations. This approach provides the means for understanding, in microscopic detail, the underlying physical processes driving the low-frequency oscillations. In the Phase I project, an electron gun region from an existing gyrotron, known to observe LFO's, was selected as a proof-of-principle geometry, and was modeled with the curved-geometry time-domain simulation tool, in order to establish the feasibility of simulating LFO physics with this tool on office-scale, and larger, parallel cluster computers. Generally, it was found to be feasible to model the simulation geometry, emission, and magnetic features of the electron gun. Ultimately, the tool will be used to investigate the origins and life cycle within the trapped particle population. This tool also provides the foundations and validation for potential application of the software to numerous other time-dependant beam and rf source problems in the commercial arena.

  11. Diffraction and Scattering in Launchers of Quasi-Optical Mode Converters for Gyrotrons

    Flamm, Jens Hanspeter

    2012-01-01

    In this work different methods for the calculation of diffraction and scattering in launchers of quasi-optical mode converters for gyrotrons are compared, ranked and extended. The extension gives the opportunity to take a tapered average radius of the waveguide antenna into account. The comparison and the extension of the fast field calculation methods for component synthesis opens the possibility to reduce diffraction and stray radiation of reliable and powerful millimeter wave sources.

  12. Time-domain theory of gyrotron traveling wave amplifiers operating at grazing incidence

    Time-domain theory of the gyrotron traveling wave tube (gyro-TWT) operating at grazing incidence has been developed. The theory is based on a description of wave propagation by a parabolic equation. The results of the simulations are compared with experimental results of the observation of subnanosecond pulse amplification in a gyro-TWT consisting of three gain sections separated by severs. The theory developed can also be used successfully for a description of amplification of monochromatic signals

  13. Time domain analysis of a gyrotron traveling wave amplifier with misaligned electron beam

    This article develops a time-domain theory to study the beam-wave interaction in gyrotron traveling wave amplifier (gyro-TWA) with a misaligned electron beam. The effects of beam misalignment on the TE01 mode gyro-TWA operating at the fundamental are discussed. Numerical results show that the effect of misalignment is less obvious when the input power is larger, and the influences of misalignment on the stable gain and the stable time are basically opposite

  14. Progress on the Development of High Power Long Pulse Gyrotron and Related Technologies

    Full text: In the development of a higher power dual-frequency gyrotron, a high order mode gyrotron, which permits to select the oscillation at 170 GHz or 137 GHz, has been fabricated and tested. Short pulse experiments (0.5 ms) were performed with 1.3 MW power output at more than 30% of the oscillation efficiency for both frequencies. In long pulse experiments, 760 kW/46%/60 s at 170 GHz and 540 kW/42%/20 s at 137 GHz are achieved. It is the first time long pulse experiments with the dual-frequency gyrotron/triode electron gun. Since the RF beam direction from the output window is designed to be almost the same for both frequencies, good power couplings to the transmission line, which are 96% for 170 GHz and 94% for 137 GHz, are obtained by using a pair of identical phase correcting mirrors. Pulse extension is underway aiming for > 1 MW at CW operation. A 5 kHz full power modulation experiment was performed using the 170 GHz gyrotron of TE31,8 mode oscillation. The 5 kHz full power modulation was achieved with the full beam modulation by employing a fast voltage switching between the anode and cathode of the triode type electron gun. This satisfies the requirement of ITER. For further improvement, an advanced anode power supply system is proposed to reduce the oscillation period of adjacent mode at the start-up phase of each pulse. (author)

  15. A 0.33-THz second-harmonic frequency-tunable gyrotron

    Zheng-Di, Li; Chao-Hai, Du; Xiang-Bo, Qi; Li, Luo; Pu-Kun, Liu

    2016-02-01

    Dynamics of the axial mode transition process in a 0.33-THz second-harmonic gyrotron is investigated to reveal the physical mechanism of realizing broadband frequency tuning in an open cavity circuit. A new interaction mechanism about propagating waves, featured by wave competition and wave cooperation, is presented and provides a new insight into the beam-wave interaction. The two different features revealed in the two different operation regions of low-order axial modes (LOAMs) and high-order axial modes (HOAMs) respectively determine the characteristic of the overall performance of the device essentially. The device performance is obtained by the simulation based on the time-domain nonlinear theory and shows that using a 12-kV/150-mA electron beam and TE-3,4 mode, the second harmonic gyrotron can generate terahertz radiations with frequency-tuning ranges of about 0.85 GHz and 0.60 GHz via magnetic field and beam voltage tuning, respectively. Additionally, some non-stationary phenomena in the mode startup process are also analyzed. The investigation in this paper presents guidance for future developing high-performance frequency-tunable gyrotrons toward terahertz applications. Project supported by the National Natural Science Foundation of China (Grant Nos. 61471007, 61531002, 61522101, and 11275206) and the Seeding Grant for Medicine and Information Science of Peking University, China (Grant No. 2014-MI-01).

  16. Development of high power gyrotron and transmission line for ECH/ECCD system

    170 GHz, high power and long pulse gyrotron with CVD diamond output window (tanδ ≤ 1.4 x 10-4, σ = 1800 W/m/K) has successfully been developed. The operation of 0.45 MW-8.0 sec and of 0.52 MW-6.2 sec were performed. Temperature increase of the window center was 150 deg. C at the operation of 0.52 MW-6.2 sec, moreover, the increment saturated, which well agreed with the simulation result. No damage on the gyrotron window and the gyrotron itself was observed through the experiment. We have constructed the 40 m run transmission line to demonstrate the efficient transmission of high power and long pulse millimeter wave. The total transmission loss has been estimated as less than 18%, which includes the loss in mirror optical unit, assumed as 10%. The transmission efficiency, the mode purity and the polarization are mainly investigated in the high power transmission experiment. The diamond window assembly as tritium or vacuum barrier in a transmission line was fabricated for high pressure test. The disk was failed at pressure of 0.465 MPa, which is consistent with the material strength. (author)

  17. Analysis of the output mode from 60 GHz, 200 kW pulsed and CW gyrotrons

    A Varian 60 GHz, CW gyrotron has recently been operated at power levels up to 200 kW CW. The tube employs a TE011/TE021 complex interaction cavity which inhibits mode competition by the TE221 mode with the desired TE021 mode. The output mode of the cavity is nominally in the TE02 circular waveguide mode in overmoded waveguide. Since the output waveguide also serves as the gyrotron collector, mode conversion occurs in the taper sections and gaps incorporated into the collector. Measurements of the mode conversion on a 60 GHz, 200 kw, 100 ms pulse tube, have been made and compared with similar measurements on the 60 GHz. 200 kW, CW gyrotron. These measurements indicated that the CW tube had significantly more conversion of the TE02 mode into other TE/sub on/ modes than did the pulse tube. Current design work is aimed at reducing the mode conversion of the CW design to the same levels as the pulse design (less than or equal to 10% mode converison)

  18. Heater design and thermal analysis of cathode assembly for 170 GHZ, 1 MW gyrotron

    An activity of design and development of 170 GHz gyrotron is started at CEERI Pilani. 170 GHz is chosen ECRH frequency at ITER and total 24 MW of RF power generated from gyrotrons will be pumped into the ECRH system of ITER. This paper presents the design of toroid shape heater for dispenser cathode and the thermal analysis of complete cathode assembly for 3.2 MW triode type MIG for 170 GHz gyrotron. Finite element method based simulation tool ANSYS Work Banch (v.14.0) is used in the simulations. In the heater design, various electrical and geometrical parameters such as filament radius, number of turns, wire thickness, heater voltage, etc are optimized. The temperature on heater is optimized around 1600 °C considering the cathode temperature around 1100 °C. Tungsten is used as the filament material due to its excellent thermal properties. After the design of heater, thermal analysis is also performed for the complete cathode assembly. Various types of potting materials are also investigated. (author)

  19. Experimental Study Of A 1.5-mw, 110-ghz Gyrotron Oscillator

    Anderson, J P

    2005-01-01

    This thesis reports the design, construction and testing of a 1.5 MW, 110 GHz gyrotron oscillator. This high power microwave tube has been proposed as the next evolutionary step for gyrotrons used to provide electron cyclotron heating required in fusion devices. A short pulse gyrotron based on the industrial tube design was built at MIT for experimental studies. The experiments are the first demonstration of such high powers at 110 GHz. Using a 96 kV, 40 A electron beam, over 1.4 MW was axially extracted in the design (TE22,6) mode in 3 μs pulses, corresponding to a microwave efficiency of 37%. The beam alpha, the ratio of transverse to axial velocity in the electron beam, was measured with a probe. At the high efficiency operating point the beam alpha was measured as 1.33. This value of alpha is less than the design value of 1.4, possibly accounting for the slightly reduced experimental efficiency. The output power and efficiency, as a function of magnetic field, beam voltage, and beam current, are in...

  20. Microwave method for synthesis of micro- and nanostructures with controllable composition during gyrotron discharge

    Batanov, German M.; Borzosekov, Valentin D.; Golberg, Dmitri; Iskhakova, Ludmila D.; Kolik, Leonid V.; Konchekov, Evgeny M.; Kharchev, Nikolai K.; Letunov, Alexander A.; Malakhov, Dmitry V.; Milovich, Filipp O.; Obraztsova, Ekaterina A.; Petrov, Alexander E.; Ryabikina, Irina G.; Sarksian, Karen A.; Stepakhin, Vladimir D.; Skvortsova, Nina N.

    2016-01-01

    We introduce an approach toward the synthesis of micro- and nanostructures under nonequilibrium microwave discharges within metal-dielectric powder mixtures induced by powerful microwave gyrotron radiation. A new plasma-chemical reactor capable of sustaining a discharge regime with an afterglow phase of an order of magnitude longer than the gyrotron pulse duration was constructed for these experiments. In the nonequilibrium conditions of such a discharge, plasma-induced exothermic chemical reactions leading to the synthesis of various compounds were initiated. The synthesized structures were deposited on the reactor walls and on the impurity particles within the reactor. This method was tested under gyrotron-initiated discharges within various metal-dielectric powder mixtures of titanium-boron, molybdenum-boron, titanium-silicon-boron, molybdenum-boron nitride, molybdenum-tungsten-boron nitride, and so on. Depending on the powder mixture composition, reactor atmosphere, and other parameters, micro- and nanosized particles of boron nitride, titanium diboride, molybdenum boride, titanium boride, molybdenum, and molybdenum oxide, were synthesized, detected, and analyzed.

  1. Optimization of megawatt 77-GHz gyrotron operation for collective Thomson scattering in LHD

    To establish a method for suppressing the spurious radiation that interferes with collective Thomson scattering measurements with less degradation of the main mode output power, the frequency evolution, and the output power of the megawatt 77-GHz gyrotron were measured during operation under optimized parameters. According to a mode competition calculation, the main mode output power may be increased by setting a lower gyrotron anode voltage at a higher magnetic field strength in the gyrotron resonator. Although the output power increased from 300 kW to 530 kW without any spurious radiation when the optimized operational parameters were used, the output power was about 50% of that at a lower magnetic field strength, and thus the output pulse width was limited to 60 ms. When an approach using the optimized operational parameters and a PIN switch was applied, the output power increased to 800 kW without any harmful spurious radiation effect and the pulse width was expanded to 2 s. (author)

  2. On the dependence of the efficiency of a 240 GHz high-power gyrotron on the displacement of the electron beam and on the azimuthal index

    Dumbrajs, O. [Institute of Solid State Physics (ISSP), Association EUROATOM-University of Latvia, Kengaraga iela 8, LV-1063 Riga (Latvia); Avramidis, K. A.; Franck, J.; Jelonnek, J. [Karlsruhe Institute of Technology (KIT), Institute for Pulsed Power and Microwave Technology (IHM), Association EURATOM-KIT, Kaiserstrasse 12, 76131 Karlsruhe (Germany)

    2014-01-15

    Two issues in the cavity design for a Megawatt-class, 240 GHz gyrotron are addressed. Those are first, the effect of a misaligned electron beam on the gyrotron efficiency and second, a possible azimuthal instability of the gyrotron. The aforementioned effects are important for any gyrotron operation, but could be more critical in the operation of Megawatt-class gyrotrons at frequencies above 200 GHz, which will be the anticipated requirement of DEMO. The target is to provide some basic trends to be considered during the refinement and optimization of the design. Self-consistent calculations are the base for simulations wherever possible. However, in cases for which self-consistent models were not available, fixed-field results are presented. In those cases, the conservative nature of the results should be kept in mind.

  3. On the dependence of the efficiency of a 240 GHz high-power gyrotron on the displacement of the electron beam and on the azimuthal index

    Two issues in the cavity design for a Megawatt-class, 240 GHz gyrotron are addressed. Those are first, the effect of a misaligned electron beam on the gyrotron efficiency and second, a possible azimuthal instability of the gyrotron. The aforementioned effects are important for any gyrotron operation, but could be more critical in the operation of Megawatt-class gyrotrons at frequencies above 200 GHz, which will be the anticipated requirement of DEMO. The target is to provide some basic trends to be considered during the refinement and optimization of the design. Self-consistent calculations are the base for simulations wherever possible. However, in cases for which self-consistent models were not available, fixed-field results are presented. In those cases, the conservative nature of the results should be kept in mind

  4. 2.2 MW Operation of the European Coaxial-Cavity Pre-Prototype Gyrotron for ITER

    Full text: A 2 MW, CW, 170 GHz coaxial-cavity gyrotron for electron cyclotron heating and current drive in the International Thermonuclear Experimental Reactor (ITER) is under development within an European Gyrotron Consortium (EGYC*). To support the development of the industrial prototype of a CW gyrotron, a short pulse tube (pre-prototype) is used at KIT (former FZK) for experimental verification of the design of critical components, such as electron gun, beam tunnel, cavity and quasi-optical (q.o.) RF-output coupler. Significant progress was achieved recently. In particular, RF output power of up to 2.2 MW with 30% output efficiency has been obtained in single-mode operation at 170 GHz. Furthermore, an excellent quality of the RF output beam with ∼ 96% fundamental Gaussian mode content has been obtained by using a new quasi-optical RF output system. The verification of these results with computer simulations will be presented. (author)

  5. Study of a cylindrical cavity gyrotron, influence of power reflection and of the oscillation of a travelling mode

    The quality factor and oscillating mode of a gyrotron cavity are essential parameters to consider when trying to obtain a high power (>500 kW), high efficiency (∼50%) microwave source, which oscillates in a stable manner in the principal mode of the cavity. The study and development of an 8 GHz gyrotron whose resonant cavity is formed by a cylindrical waveguide of slowly varying radius, is undertaken. The study is principally concerned with the phenomena associated with the low quality factor of the TEo011 mode of the cavity. (author) figs., tabs., 102 refs

  6. Measurement of the electric field pattern of a Fabry-Perot resonator used in quasi-optical gyrotrons

    The field pattern of the resonator used in a quasi-optical gyrotron operating in the millimetre wave range is measured. Two resonators are studied: one composed of a spherical mirror and an ellipsoidal grating and the other symmetric using two mirrors with annular slots. The measurements indicate that the electric field distribution is gaussian, in spite of the complex geometry of the resonator, and thus provide an experimental basis for the assumption often used to compute the efficiency of quasi-optical gyrotrons. (author) 9 figs., 8 refs

  7. ECH-assisted Startup using ITER Prototype of 170 GHz Gyrotron in KSTAR

    Full text: The newly installed electron cyclotron heating and current drive (EC H&CD) system with a frequency of 170 GHz was successfully commissioned and used for the second-harmonic ECH- assisted startup in 2011 operational campaign of the KSTAR. As a RF power source, ITER pre-prototype of 170 GHz, 1 MW continuous-wave gyrotron was loaned from the Japan Atomic Energy Agency (JAEA). The Gaussian beam output from the gyrotron passes through an edge- cooled diamond window and is coupled to an HE11 corrugated waveguide via two phase correcting mirrors in a matching optics unit (MOU). The power coupled to the HE11 corrugated waveguide is delivered to the launcher by the transmission total length of 70 meters. For the first 1 MW EC H&CD system, 1-beam based 1 MW equatorial launcher is installed in the KSTAR Bay E-m. The launcher has been designed and fabricated in collaboration with both Princeton Plasma Physics Laboratory (PPPL) and Pohang University of Science and Technology (POSTECH). During the KSTAR 2011 campaign, 10-s pulse at 0.6 MW EC beam was reliably injected into the plasma. Also, 170 GHz second harmonic ECH-assisted start-up was successful leading to reduce the flux consumption at toroidal magnetic field of 3 T. In this experiment, the flux consumption until the plasma current flat-top was reduced from 4.13 Wb for pure Ohmic to 3.62 Wb (12% reduction) for the perpendicular injection. When the EC beam is launched with toroidal angle of 20 deg with respect to the outward radial direction at the steering mirror, more reduced magnetic flux consumption was obtained with 3.14 Wb (24% reduction) compared with pure OH plasmas. After the 2011 campaign, the gyrotron has been fully commissioned with the output power of 1 MW at the diamond window and the frequency of 170 GHz by precise alignment of the magnet to the gyrotron axis. (author)

  8. Preliminary design of 1 MW, Ku-band gyrotron traveling-wave amplifier

    Chongqing JIAO

    2009-01-01

    The preliminary design results ofa 1-MW, Ku-band gyrotron traveling wave amplifier (gyro-TWA) are presented. Operating at the second cyclotron harmonic of the TE11 mode, the amplifier characterizes good stability even in the case of no distributed losses loaded, which could potentially allow it to be operated at high average power. Large signal simulation shows that the amplifier can generate a saturated peak power of about 1 MW with efficiency of 26.6%, gain of 31 dB, and 3-dB bandwidth of about 1 GHz when driven by a 100 kV, 40 A electron beam with 5% axial velocity spread.

  9. Experiment for over 200 kW oscillation of a 295 GHz pulse gyrotron

    A high-power sub-THz gyrotron is under development as a power source of collective Thomson scattering diagnostic of fusion plasmas. It operates at a fundamental harmonic frequency of 295 GHz. A cavity which realizes stable and efficient single mode oscillation, an electron gun with an intense laminar electron beam, and an internal mode convertor are designed. A maximum oscillation power of 234 kW is achieved with a Gaussian like radiation pattern. The duration of 130 kW pulse is extended up to 30 microseconds, which is limited by the configuration of power supply. (author)

  10. Experiment for Over 200 kW Oscillation of a 295 GHz Pulse Gyrotron

    YAMAGUCHI, YuuSuke; SAITO, Teruo; TATEMATSU, Yoshinori; IKEUCHI, Shinji; KASA, Jun; KOTERA, Masaki; Ogawa, Isamu; Idehara, Toshitaka; Kubo, Shin; SHIMOZUMA, Takashi; NISHIURA, Masaki; Tanaka, Kenji

    2013-01-01

    A high-power sub-THz gyrotron is under development as a power source of collective Thomson scatteringdiagnostic of fusion plasmas. It operates at a fundamental harmonic frequency of 295 GHz. A cavity whichrealizes stable and efficient single mode oscillation, an electron gun with an intense laminar electron beam, andan internal mode convertor are designed. A maximum oscillation power of 234kW is achieved with a Gaussianlike radiation pattern. The duration of 130kW pulse is extended up to 30 m...

  11. ECRH transmission system

    The M.I.T. gyrotron group operates a 140 GHz, short pulse (1μs) gyrotron with output power, at present, of up to 175 kW. Output radiation has been obtained in several modes, including TE03 at 140 GHz, TE23 at 137 GHz, TE42 at 128 GHz and TE52 at 145 GHz. Studies have been carried out of the mode purity, both in frequency and in space, of gyrotron output radiation. These studies investigate parasitic mode excitation and mode conversion of gyrotron output power. Far field patterns of gyrotron radiation have been investigated to determine mode symmetry and purity. These results are useful in estimating the efficiency of various transmission systems. Finally, a new approach to quasi-optical transmission lines and mode converters, using axisymmetric optics, is suggested

  12. Development of problem-oriented software packages for numerical studies and computer-aided design (CAD) of gyrotrons

    Damyanova, M.; Sabchevski, S.; Zhelyazkov, I.; Vasileva, E.; Balabanova, E.; Dankov, P.; Malinov, P.

    2016-03-01

    Gyrotrons are the most powerful sources of coherent CW (continuous wave) radiation in the frequency range situated between the long-wavelength edge of the infrared light (far-infrared region) and the microwaves, i.e., in the region of the electromagnetic spectrum which is usually called the THz-gap (or T-gap), since the output power of other devices (e.g., solid-state oscillators) operating in this interval is by several orders of magnitude lower. In the recent years, the unique capabilities of the sub-THz and THz gyrotrons have opened the road to many novel and future prospective applications in various physical studies and advanced high-power terahertz technologies. In this paper, we present the current status and functionality of the problem-oriented software packages (most notably GYROSIM and GYREOSS) used for numerical studies, computer-aided design (CAD) and optimization of gyrotrons for diverse applications. They consist of a hierarchy of codes specialized to modelling and simulation of different subsystems of the gyrotrons (EOS, resonant cavity, etc.) and are based on adequate physical models, efficient numerical methods and algorithms.

  13. A broadband gyrotron backward-wave oscillator with tapered interaction structure and magnetic field

    Li, G. D.; Chang, P. C.; Chiang, W. Y.; Lin, P. N.; Kao, S. H.; Lin, Y. N.; Huang, Y. J.; Barnett, L. R.; Chu, K. R., E-mail: krchu@yahoo.com.tw [Department of Physics, National Taiwan University, Taipei 106, Taiwan (China); Chen, H. Y.; Fan, C. T. [Wave Power Technology, 232 Youyi Road, Zhunan, Miaoli, Taiwan (China)

    2015-11-15

    The gyro-monotron and gyrotron backward-wave oscillator (gyro-BWO) are the two oscillator versions of gyrotrons. While serving different functions, they are also radically different in the RF field formation mechanisms. The gyro-monotron RF field profile is essentially fixed by the resonant interaction structure, while the gyro-BWO possesses an extra degree of freedom in that the axial RF field profile is self-determined by the beam-wave interaction in a waveguide structure. The present study examines ways to utilize the latter feature for bandwidth broadening with a tapered magnetic field, while also employing a tapered waveguide to enhance the interaction efficiency. We begin with a mode competition analysis, which suggests the theoretical feasibility of broadband frequency tuning in single-mode operation. It is then shown in theory that, by controlling the RF field profile with an up- or down-tapered magnetic field, the gyro-BWO is capable of efficient operation with a much improved tunable bandwidth.

  14. Safety and protection of 8T NbTi gyrotron magnet in persistent mode

    Successful series of 5T cryomagnetic systems for additional high frequency plasma heating in Tokamaks T10 and T15, produced in Czechoslovakia during the last decade with the authors participation in magnet design and testing encouraged them to continue in further development of gyrotron magnets for further generation with operational field B0 = 8T. Approximately of the size and dimensions as was the case of previous 5T series, the 8T gyrotron magnet was designed as a part of preliminary work with preparations for ITER project. To achieve high mechanical stability of the superconducting winding, numerical stress-strain analyzes of winding structure and appropriate technology of epoxy impregnation were applied. To improve winding mechanical stability, initially round φ1 mm varnish insulated conductor was flattened to ''race track'' cross section (1.25 x 0.75 mm2 for inner section, respectively, 1.31 x 0.65 mm2 for the rest of magnet). Stainless steel road (φ1mm) of the bandage was flattened in the same way too (up to 1.14 x 0.77 mm2). Danger of creating a hot spot region has been limited by radial magnet sectioning and sections shunting by low ohmic shunts. Superconducting switch was protected by couple of antiparallel silicon diodes mounted between magnet flanges in parallel to it. High threshold voltages of diodes at 4.2K allow to run up system with relatively high speed without any limitation on sign of magnet field polarity

  15. Upgrade Of The TH1506B 118 GHz Gyrotron Using Modeing Tools

    The first TH1506B prototype showing problems of overheating and spurious oscillations, a new modified gyrotron was built. During the tests, the extwo peaks, which was never predicted by simulations. Various low evel tests were performed on the mode converter with different shapes for the launcher but without real improvement. Besides measurements, the use of a new software Surf3D[l] showed that the problem mainly comes from the 3rd mirror whose curvature is too high and not well taken nto account by the calculation. This analysis software is based on ntegral equations and the complete 3D modelling alowed to determine a new profile for the 3rd mirror. An aluminium model of a new mirror was manufactured and thorough low level tests made at FZK showed that there was no double peak.The next step would consist in building a gyrotron based on this new design, to confirm the simulation and to valdate it for long pulses

  16. Combined Hyperthermia and Photodynamic Therapy Using a Sub-THz Gyrotron as a Radiation Source

    Miyoshi, Norio; Idehara, Toshitaka; Khutoryan, Eduard; Fukunaga, Yukihiro; Bibin, Andriana Bintang; Ito, Shinji; Sabchevski, Svilen Petrov

    2016-08-01

    In this paper, we present results of a hyperthermia treatment of malignant tumors using a gyrotron as a radiation source for heating of the cancerous tissue. They clearly demonstrate the efficiency of the irradiation by sub-THz waves, which leads to steady decrease of the volume of the tumor and finally to its disappearance. A combination of hyperthermia and photodynamic therapy (PDT) that utilizes a novel multifunctional photosensitizer has also been explored. In the latter case, the results are even more convincing and promising. In particular, while after a hyperthermia treatment sometimes a regrowth of the tumor is being observed, in the case of combined hyperthermia and PDT such regrowth has never been noticed. Another combined therapy is based on a preheating of the tumor by gyrotron radiation to temperatures lower than the hyperthermia temperature of 43 °C and followed then by PDT. The results show that such combination significantly increases the efficiency of the treatment. We consider this phenomenon as a synergy effect since it is absent when hyperthermia and PDT are applied separately, and manifests itself only when both methods are combined.

  17. Effect of ion compensation of the beam space charge on gyrotron operation

    In gyrotrons, the coherent radiation of electromagnetic waves takes place when the cyclotron resonance condition between the wave frequency and the electron cyclotron frequency or its harmonic holds. The voltage depression caused by the beam space charge field changes the relativistic cyclotron frequency and, hence, can play an important role in the beam-wave interaction process. In long pulse and continuous-wave regimes, the beam space charge field can be partially compensated by the ions, which appear due to the beam impact ionization of neutral molecules of residual gases in the interaction space. In the present paper, the role of this ion compensation of the beam space charge on the interaction efficiency is analyzed. We also analyze the effect of the electron velocity spread on the limiting currents and discuss some effects restricting the ion-to-beam electron density ratio in the saturation stage. It is shown that the effect of the ion compensation on the voltage depression caused by the beam space charge field can cause significant changes in the efficiency of gyrotron operation and, in some cases, even result in the break of oscillations

  18. Characteristics of a superconducting magnet using a persistent current for a 110 GHz gyrotron

    Maebara, Sunao; Kasugai, Atsushi; Sakamoto, Keishi; Tsuneoka, Masaki; Imai, Tsuyoshi [Japan Atomic Energy Research Inst., Naka, Ibaraki (Japan). Naka Fusion Research Establishment

    1996-03-01

    A superconducting magnet (SCM) using a persistent current for a 110 GHz gyrotron was developed to reduce liquid-helium loss, the boiled-off rate of 0.13 liter/hour was attained in a persistent current operation. It shows that the continuous operation for 50 days is capable without additional liquid-helium supply. Moreover, the 3040 liter in a year is used for a gyrotron test during five months and for the maintenance during seven months and liquid-helium savings of 65% was successfully demonstrated. The SCM is capable to excite the maximum magnetic field of 5.0 T in the persistent current mode. A mirror ratio between resonant cavity and magnetron injection gun (MIG) is 20 for operating the main coils in the persistent mode, since cavity coils and gun coils are connected in series. Auxiliary coils are equipped independently to control the mirror ratio, the mirror ratio of 13.6 - 37.0 at the 110 GHz is available. A two-stage refrigerator using helium gas was also installed and made liquid-nitrogen for cooling thermal shield of 80 K free. By developing this new type SCM, the number of routine works was drastically decreased in one time per 22-50 days, while routine works of a few times per week was needed up to now. (author).

  19. Effect of ion compensation of the beam space charge on gyrotron operation

    Fokin, A. P.; Glyavin, M. Yu. [Institute of Applied Physics, Russian Academy of Sciences, Nizhny Novgorod 603950 (Russian Federation); Nusinovich, G. S. [Institute for Research in Electronics and Applied Physics, University of Maryland, College Park, Maryland 20742-3511 (United States)

    2015-04-15

    In gyrotrons, the coherent radiation of electromagnetic waves takes place when the cyclotron resonance condition between the wave frequency and the electron cyclotron frequency or its harmonic holds. The voltage depression caused by the beam space charge field changes the relativistic cyclotron frequency and, hence, can play an important role in the beam-wave interaction process. In long pulse and continuous-wave regimes, the beam space charge field can be partially compensated by the ions, which appear due to the beam impact ionization of neutral molecules of residual gases in the interaction space. In the present paper, the role of this ion compensation of the beam space charge on the interaction efficiency is analyzed. We also analyze the effect of the electron velocity spread on the limiting currents and discuss some effects restricting the ion-to-beam electron density ratio in the saturation stage. It is shown that the effect of the ion compensation on the voltage depression caused by the beam space charge field can cause significant changes in the efficiency of gyrotron operation and, in some cases, even result in the break of oscillations.

  20. Design of the collective Thomson scattering (CTS) system by using 170-GHz gyrotron in the KSTAR

    Park, Min; Kim, Sun-Ho; Kim, Sung-Kyu [Korea Atomic Energy Research Institute, Daejeon (Korea, Republic of); Lee, Kyu-Dong; Wang, Son-Jong [National Fusion Research Institute, Daejeon (Korea, Republic of)

    2014-10-15

    The physics of energetic ions is one of the primary subjects to be understood toward the realization of a nuclear fusion power plant. Collective Thomson scattering (CTS) offers the possibility to diagnose the fast ions and the alpha particles in burning plasmas. Spatially- and temporally resolved one-dimensional velocity distributions of the fast ions can be obtained from the scattered radiation with fewer geometric constraints by utilizing millimeter waves from a high-power gyrotron as a probe beam. We studied the feasibility of CTS fast-ion measurements in the KSTAR by calculating the spectral density functions. Based on that, we suggest a design for the CTS system that uses the currently-operating 170-GHz gyrotron for electron cyclotron heating (ECH) and electron cyclotron current drive (ECCD) in the KSTAR. The CTS system is presented as two subsystems: the antenna system and the heterodyne receiver system. The design procedure for an off-axis ellipsoidal mirror is described, and the CTS system requirements are discussed.

  1. Effect of ion compensation of the beam space charge on gyrotron operation

    Fokin, A. P.; Glyavin, M. Yu.; Nusinovich, G. S.

    2015-04-01

    In gyrotrons, the coherent radiation of electromagnetic waves takes place when the cyclotron resonance condition between the wave frequency and the electron cyclotron frequency or its harmonic holds. The voltage depression caused by the beam space charge field changes the relativistic cyclotron frequency and, hence, can play an important role in the beam-wave interaction process. In long pulse and continuous-wave regimes, the beam space charge field can be partially compensated by the ions, which appear due to the beam impact ionization of neutral molecules of residual gases in the interaction space. In the present paper, the role of this ion compensation of the beam space charge on the interaction efficiency is analyzed. We also analyze the effect of the electron velocity spread on the limiting currents and discuss some effects restricting the ion-to-beam electron density ratio in the saturation stage. It is shown that the effect of the ion compensation on the voltage depression caused by the beam space charge field can cause significant changes in the efficiency of gyrotron operation and, in some cases, even result in the break of oscillations.

  2. Continuous-Wave Operation of a Frequency-Tunable 460-GHz Second-Harmonic Gyrotron for Enhanced Nuclear Magnetic Resonance.

    Torrezan, Antonio C; Han, Seong-Tae; Mastovsky, Ivan; Shapiro, Michael A; Sirigiri, Jagadishwar R; Temkin, Richard J; Barnes, Alexander B; Griffin, Robert G

    2010-06-01

    The design, operation, and characterization of a continuous-wave (CW) tunable second-harmonic 460-GHz gyrotron are reported. The gyrotron is intended to be used as a submillimeter-wave source for 700-MHz nuclear magnetic resonance experiments with sensitivity enhanced by dynamic nuclear polarization. The gyrotron operates in the whispering-gallery mode TE(11,2) and has generated 16 W of output power with a 13-kV 100-mA electron beam. The start oscillation current measured over a range of magnetic field values is in good agreement with theoretical start currents obtained from linear theory for successive high-order axial modes TE(11,2,q). The minimum start current is 27 mA. Power and frequency tuning measurements as a function of the electron cyclotron frequency have also been carried out. A smooth frequency tuning range of 1 GHz was obtained for the operating second-harmonic mode either by magnetic field tuning or beam voltage tuning. Long-term CW operation was evaluated during an uninterrupted period of 48 h, where the gyrotron output power and frequency were kept stable to within ±0.7% and ±6 ppm, respectively, by a computerized control system. Proper operation of an internal quasi-optical mode converter implemented to transform the operating whispering-gallery mode to a Gaussian-like beam was also verified. Based on the images of the gyrotron output beam taken with a pyroelectric camera, the Gaussian-like mode content of the output beam was computed to be 92% with an ellipticity of 12%. PMID:21243088

  3. Power-stabilization of high frequency gyrotrons using a double PID feedback control for applications to many high power THz spectroscopy

    Kuleshov, Alexei; Ueda, Keisuke; Idehara, Toshitaka

    2013-01-01

    High stabilization of the output power of high frequency gyrotrons for high power THzspectroscopy is an important issue in order to extend the applications of gyrotrons to wider subjects.For this objective, we tried a PID feedback control on a heater current of a triode magnetroninjection gun (MIG) for stabilization of an electron beam current and an additional PID control ofan anode voltage of the gun for direct stabilization of output power. This double PID controlachieves effective respons...

  4. Increase in efficiency of gyrotron by optimizing conditions of RF-field emission

    Operation efficiency of many electronics devices depends on the relation between integral flux of emitted energy and value of total energy in the volume of device. This relation is similar to the value of effective decrement which determines the relative part of the emitted useful energy per unit of time. The optimum values of this relation exist, at which greatest output power of devices and their greatest efficiency is reached. Change in the relative part of the emitted energy frequently depends on boundary conditions or concordance the output of device with the line of transmission of energy. However, for the more adequate descriptions of the instruments operation it is useful to switch over to use the value of the relative part of energy that emitted in unit of time as the guide parameter (or the value of effective decrement). Modern highly effective generators of RF field are gyrotrons which can be used for the heating of plasma in the thermonuclear fusion facilities and diagnostics of nature phenomenon. As known these devices are very sensitive to the selection of boundary conditions or conditions of concordance with the lines of transmissions of energy. In the present work it is examined the influence of changes in the boundary conditions and, accordingly, the change the relative part of the emitted energy, on the value of radiated power and efficiency of gyrotron. The optimum values of the relative part of the emitted energy are determined, at which the greatest level of radiated power and efficiency is reached. The presence of the low-density plasma changes the conditions for generation of RF-field and makes it possible to increase the maximally accessible output power of device. Therefore in the work the influence of the low-density plasma on change in the optimum parameters of the RF field generation are determined. It is shown, that in the vacuum case the greatest efficiency is reached when effective decrement is of order 0.7. The filling of gyrotron by

  5. Analysis of Mig-type electron guns for a 35GHz gyrotron

    A 35GHz gyrotron is currently under construction at the Associated Plasma Laboratory of the Institute for Space Research to be used in plasma heating and noninductive current drive experiments. A critical component of the device is the electrooptical system, which must generate a beam with low velocity spread and high transverse energy. One way to decrease the velocity spread is to use laminar beams. For laminar flow, where the trajectories do not cross, the axial component of the space-charge forces changes sign each half cycle models of magnetron injection guns that produce laminar beams are analyzed and procedures for controlling the pitch angle parameter, which defines the transverse-to-axial electron velocity ratio are investigated. (author)

  6. Studies of self-consistent field structure in a quasi-optical gyrotron

    The presence of an electron beam in a quasi-optical gyrotron cavity alters the structure of the fields from that of the empty cavity. A computer code has been written which calculates this alteration for either an electron beam or a thin dielectric tube placed in the cavity. Experiments measuring the quality factor of such a cavity performed for the case of a dielectric tube and the results agree with the predictions of the code. Simulations of the case of an electron beam indicate that self-consistent effects can be made small in that almost all the power leaves the cavity in a symmetric gaussian-like mode provided the resonator parameters are chosen carefully. (author) 6 figs., 1 tab., 13 refs

  7. 1 megawatt, 100 GHz gyrotron study. Final report, March 21-September 1, 1983

    This report provides the results of a design study on a gyrotron device employing a new type of hollow gyrobeam formation system and having a capability for delivering megawatt CW power at 100 GHz to an ECRH-heated, magnetically-confined plasma. The conceptual basis for the beam formation system is the tilt-angle gun (TAG) in which a conically-shaped electron beam is formed in a magnetically-shielded region and is then injected into the stray-field region of the main magnetic focusing system. Because fluid coolants can be accessed through the central pole of the TAG-type gun, rf interaction can be contemplated with cavity configurations not practical with the conventional MIG-type gyrobeam formation systems

  8. Free-electron masers vs. gyrotrons prospects for high-power sources at millimeter and submillimeter wavelengths

    Thumm, M K

    2002-01-01

    The possible applications of high-power millimeter (mm) and sub-mm waves from free-electron masers (FEMs) and gyro-devices span a wide range of technologies. The plasma physics community has already taken advantage of recent advances in applying high-power mm waves generated by long pulse or continuous wave (CW) gyrotron oscillators and short pulse very high-power FEMs in the areas of RF-plasma production, heating, non-inductive current drive, plasma stabilization and active plasma diagnostics for magnetic confinement thermonuclear fusion research, such as electron cyclotron resonance heating (28-170 GHz), electron cyclotron current drive , collective Thomson scattering , microwave transmission and heat-wave propagation experiments. Continuously frequency tunable FEMs could widen these fields of applications. Another important application of CW gyrotrons is industrial materials processing, e.g. sintering of high-performance functional and structural nanostructured ceramics. Sub-mm wave sources are employed in...

  9. Infrared Measurements of the RF Output of 170-GHz/2-MW Coaxial Cavity Gyrotron and Its Phase Retrieval Analysis

    Jawla, S.; Hogge, J.-P.; Alberti, S.; Goodman, T.; Piosczyk, B.; Rzesnicki, T.

    2009-01-01

    We report the experimental results of the infrared measurements of output RF beam of the European 2-MW 170-GHz coaxial cavity gyrotron for ITER. The output beam profile is measured by the infrared thermographic technique using an infrared camera and a target material which is being irradiated by the RF output. The beam intensity was measured at several locations along the propagation direction. The data were processed for noise reduction and perspective correction and then used with the phase...

  10. Development of 1 MW gyrotron and progress of ECH system for the GAMMA 10 tandem mirror in Tsukuba

    High power gyrotrons with TE4,2 cavity at 28 GHz and with TE18,6 cavity and a diamond window at 77 GHz have been developed for GAMMA 10 and LHD in the joint program of NIFS and University of Tsukuba. The maximum outputs of 570 kW at 28 GHz and 1.1 MW at 77 GHz were obtained corresponding to each design. The operations of more than 750 kW for 5 sec. and 810 kW for 3.5 sec. were achieved in the developing tubes at 77 GHz, which is the first high power-long pulse result of the 77 GHz tube. The experimental simulation of the effect of the stray RF in the 28 GHz tube indicates the stray RF is the one of the major causes limiting gyrotron performance. The output of more than 1 MW with 40% oscillation efficiency is expected from the design of the next 28 GHz gyrotron for GAMMA 10. Installation of the polarizer in the transmission line enhanced the performance of the ECH system in GAMMA 10, that is the first result which clearly showed ∼100% X mode excitation is a key to design the efficient fundamental ECH system of strong field side injection in mirror devices. (author)

  11. Theoretical study on mode competition between fundamental and second harmonic modes in a 0.42 THz gyrotron with gradually tapered complex cavity

    Zhao, Qixiang, E-mail: zxqi1105@gmail.com; Yu, Sheng; Zhang, Tianzhong [Terahertz Science and Technology Research Center, University of Electronic Science and Technology of China, Chengdu 610054 (China); Li, Xiang [Queen Mary University of London, London E1 4NS (United Kingdom)

    2015-10-15

    In this paper, the nonlinear dynamics of mode competition in the complex cavity gyrotron are studied by using multi-frequency, time-dependent theory with the cold-cavity longitudinal profile approximation. Based on the theory, a code is written to simulate the mode competition in the gradually tapered complex cavity gyrotron operating at second harmonic oscillation. The simulations tracking seven competition modes show that single mode oscillation of the desired mode TE{sub 17.4} at 150 kW level can be expected with proper choice of operating parameters. Through studying on mode competition, it is proved that the complex cavity has a good capability for suppressing the mode competition. Meanwhile, it is found that TE{sub 17.3} could be excited in the first cavity as a competition mode when the gyrotron operating at large beam current, which leads to that TE{sub 17.3} and TE{sub 17.4} with different frequencies can coexist stably in the complex cavity gyrotron with very close amplitudes. Thus, the complex cavity might be used for multi-frequency output gyrotron.

  12. Development of a dual frequency (110/138 GHz gyrotron for JT-60SA and its extension to an oscillation at 82 GHz

    Kobayashia Takayuki

    2015-01-01

    Full Text Available A dual-frequency gyrotron, which can generate 110 GHz and 138 GHz waves independently, is being developed in JAEA to enable electron cyclotron heating (ECH and current drive (ECCD in a wider range of plasma discharge conditions of JT-60SA. Conditioning operation of the gyrotron toward 1 MW for 100 s, which is the target output power and pulse length for JT-60SA, is in progress without significant problems. Oscillations of 1 MW for 10 s and 0.5 MW for 198 s were obtained, so far, at both frequencies. Cooling water temperatures in the gyrotron and matching optics unit were saturated in the 198 s oscillation, and the observed maximum water temperature is sufficiently low. In addition to the above activity on the dual-frequency gyrotron development, an oscillation (0.3 MW for 20 ms at 82 GHz was demonstrated as an additional frequency of the dual-frequency gyrotron. A possibility of the use of fundamental harmonic wave at 82 GHz in JT-60SA has been shown.

  13. Theoretical study on mode competition between fundamental and second harmonic modes in a 0.42 THz gyrotron with gradually tapered complex cavity

    In this paper, the nonlinear dynamics of mode competition in the complex cavity gyrotron are studied by using multi-frequency, time-dependent theory with the cold-cavity longitudinal profile approximation. Based on the theory, a code is written to simulate the mode competition in the gradually tapered complex cavity gyrotron operating at second harmonic oscillation. The simulations tracking seven competition modes show that single mode oscillation of the desired mode TE17.4 at 150 kW level can be expected with proper choice of operating parameters. Through studying on mode competition, it is proved that the complex cavity has a good capability for suppressing the mode competition. Meanwhile, it is found that TE17.3 could be excited in the first cavity as a competition mode when the gyrotron operating at large beam current, which leads to that TE17.3 and TE17.4 with different frequencies can coexist stably in the complex cavity gyrotron with very close amplitudes. Thus, the complex cavity might be used for multi-frequency output gyrotron

  14. Microwave generation for magnetic fusion energy applications, Task B

    One of the main issues in the development of high power gyrotrons is the present discrepancy between the theoretically predicted efficiency and that observed in the experiments. Recent 140 GHz experiments by MIT employed three cavities; two of the cavities have different interaction lengths and the third cavity is a complex two-section cavity. In all cases, the maximum experimental efficiency is well below the theoretically predicted one. A better theoretical understanding of the causes of these discrepancies is essential to the scaling of gyrotrons to higher power and higher frequency. We continued our investigation with the objective of determining whether mode competition and velocity spread in the electron beam could in some way be influencing the current result from the MIT 140 GHz gyrotrons experiments and determining to what extent these effects would influence operation of a 1 MW, 280 GHz, TE42,7 gyrotron as conceived at MIT. In our investigations, we used two models, the ''fixed axial field profile'' model and the ''self-consistent determination of the axial field profile'' model. With the ''fixed axial field profile'' model we studied the effect of thermal spread on the efficiency of gyrotrons operation, mode competition between unequally spaced modes, and we simulated the start up of the MIT 140 GHz gyrotrons. Our main conclusions from all these studies are discussed in this paper

  15. State-of-the-art of high power gyro-devices and free electron masers 1994

    At present, gyrotron oscillators are mainly used as high power millimeter wave sources for electron cyclotron resonance heating (ECRH) and diagnostics of magnetically confined plasmas for generation of energy by controlled thermonuclear fusion. 140 GHz gyrotrons with output power Pout=0.54 MW, pulse length τ=3.0 s and efficiency η=42% are commercially available. Total efficiencies around 50% have been achieved using single-stage depressed collectors. Diagnostic gyrotrons deliver Pout=40 kW with τ=40 μs at frequencies up to 650 GHz (η≥4%). Recently, gyrotron oscillators have also been successfully used in material processing and plasma chemistry. Such technological applications require gyrotrons with the following parameters: f≥24 GHz, Pout=10-50 kW, CW, η≥30%. This paper reports on achievements and problems related to the development of very high power mm-wave gyrotrons for long pulse or CW operation and describes the microwave technological pecularities of the different development steps. In addition, this work gives a short overview of the present development of gyrotrons for technological applications, relativistic gyrotrons, quasi-optical gyrotrons, cyclotron autoresonance masers (CARMs), gyro klystrons, gyro-TWT amplifiers, gyrotwystron amplifiers, gyro-BWO's, peniotrons and free electron masers (FEMs). The most impressive FEM output parameters are: Pout=2 GW, τ=20 ns, η=13% at 140 GHz (LLNL) and Pout=15 kW, τ=20 μs, η=5% in the range from 120 to 900 GHz (UCSB). (orig.)

  16. A gyrotron-powered pellet accelerator for ITER - Improvements and experiments

    Assessments of design modifications of the gyrotron-powered pellet accelerator show that issues raised by the initial design can be eliminated by appropriate design changes. These include: (1) Use of an annular guide tube which separates the mm-wave waveguide function from the pellet guide-tube function will eliminate low density gas breakdown from the mm-wave guide. (2) A calculation concludes that the mm-wave electric fields, while strong, are nonetheless well-below breakdown because of the high density of solid hydrogen. (3) The ITER thermal-engineering design should make provisions for mounting the annular guidetube on the thermal shield which will passively cool the guide tubes. Microwave heating of the thermal shield will be less than 1% of the total heat load. (4) A mobile tamper, transparent to mm-waves, can eliminate the need for moving parts in the tokamak interior. Tamper recoil energy and momentum will be used to operate the loading of pellet cartridges but only well outside the tokamak chamber. Several experiments to test these ideas are outlined. With a minimum of engineering redesign, speed of ITER pellets could increase by an order of magnitude. An improved ablation model finds this increases the ablation penetration length by a factor-of-six. (author)

  17. Numerical analysis on bandwidth and growth rate of plasma-filled gyrotron devices

    The linear theory of a plasma-loaded gyrotron amplifier is studied in the fast and mixed wave modes. The analysis is done for an infinitely hollow thin electron beam, as the electrons have the same energy and angular momentum. The plasma is assumed to be cold. In the numerical analysis, the plasma has electrons and ions, with dielectric coefficient ε. The system configuration consists of the cylindrical plasma column loaded inside the electron beam and is placed parallel to the axis of conductive cylinder. There is a strong magnetic field, B0êz along the axis of the cylinder. The dispersion relation is derived with the Vlasov-Maxwell's equations. The effects of beam location, plasma column radius, electron beam parameters and azimuthal harmonic number on the growth rate for fast and mixed wave modes are investigated. Results show that the growth rate and bandwidth of the mixed wave mode is larger than the fast wave mode. It is shown that the bandwidth of this structure is largest for small value of the axial momentum spread. (author)

  18. Low-voltage harmonic multiplying gyrotron traveling-wave amplifier in G band

    Harmonic multiplying operation in a gyrotron traveling-wave amplifier (gyro-TWA) permits for magnetic field reduction and frequency multiplication. Lowering a beam voltage is an important step toward miniaturization of a harmonic multiplying gyro-TWA. However, the additional degree of freedom that is provided by the multitude cyclotron harmonics in a low-voltage harmonic multiplying gyro-TWA still easily generates various competing modes. An improved mode-selective circuit, using circular waveguides with various radii, can provide the rejection points within the frequency range to suppress competing modes. Simulated results reveal that the mode-selective circuit can provide an attenuation of more than 14 dB to suppress the competing modes. Furthermore, the performance of the gyro-TWA is analyzed for studying the sensitivity of the saturated output power and full width at half maximum bandwidth of the gyro-TWA to the beam voltage and the magnetic field. A stable low-voltage harmonic multiplying gyro-TWA with the mode-selective circuit is predicted to yield a peak output power of 24 kW at 200.4 GHz, corresponding to a saturated gain of 56 dB at an interaction efficiency of 20%. The full width at half maximum bandwidth is 3.0 GHz

  19. G-band harmonic multiplying gyrotron traveling-wave amplifier with a mode-selective circuit

    Harmonic multiplying gyrotron traveling-wave amplifiers (gyro-TWAs) permit for magnetic field reduction and frequency multiplication. A high-order-mode harmonic multiplying gyro-TWA with large circuit dimensions and low ohmic loss can achieve a high average power. By amplifying a fundamental harmonic TE01 drive wave, the second harmonic component of the beam current initiates a TE02 wave to be amplified. Wall losses can suppress some competing modes because they act as an effective sink of the energy of the modes. However, such wall losses do not suppress all competing modes as the fields are contracted in the copper section in the gyro-TWA. An improved mode-selective circuit, using circular waveguides with the specified radii, can provide the rejection points within the frequency range to suppress the competing modes. The simulated results reveal that the mode-selective circuit can provide an attenuation of more than 10 dB to suppress the competing modes (TE21, TE51, TE22, and TE03). A G-band second harmonic multiplying gyro-TWA with the mode-selective circuit is predicted to yield a peak output power of 50 kW at 198.8 GHz, corresponding to a saturated gain of 55 dB at an interaction efficiency of 10%. The full width at half maximum bandwidth is 5 GHz

  20. Mechanisms of amplification of ultrashort electromagnetic pulses in gyrotron traveling wave tube with helically corrugated waveguide

    A time-domain self consistent theory of a gyrotron traveling wave tube with a helically corrugated operating waveguide has been developed. Based on this model, the process of short pulse amplification was studied in regimes of grazing and intersection of the dispersion curves of the electromagnetic wave and the electron beam. In the first case, the possibility of amplification without pulse form distortion was demonstrated for the pulse spectrum width of the order of the gain bandwidth. In the second case, when the electrons' axial velocity was smaller than the wave's group velocity, it was shown that the slippage of the incident signal with respect to the electron beam provides feeding of the signal by “fresh” electrons without initial modulation. As a result, the amplitude of the output pulse can exceed the amplitude of its saturated value for the case of the grazing regime, and, for optimal parameters, the peak output power can be even larger than the kinetic power of the electron beam

  1. Mechanisms of amplification of ultrashort electromagnetic pulses in gyrotron traveling wave tube with helically corrugated waveguide

    Ginzburg, N. S.; Zotova, I. V.; Sergeev, A. S.; Zaslavsky, V. Yu.; Zheleznov, I. V.; Samsonov, S. V.; Mishakin, S. V.

    2015-11-01

    A time-domain self consistent theory of a gyrotron traveling wave tube with a helically corrugated operating waveguide has been developed. Based on this model, the process of short pulse amplification was studied in regimes of grazing and intersection of the dispersion curves of the electromagnetic wave and the electron beam. In the first case, the possibility of amplification without pulse form distortion was demonstrated for the pulse spectrum width of the order of the gain bandwidth. In the second case, when the electrons' axial velocity was smaller than the wave's group velocity, it was shown that the slippage of the incident signal with respect to the electron beam provides feeding of the signal by "fresh" electrons without initial modulation. As a result, the amplitude of the output pulse can exceed the amplitude of its saturated value for the case of the grazing regime, and, for optimal parameters, the peak output power can be even larger than the kinetic power of the electron beam.

  2. Analysis and design of double-anode magnetron injection gun for 170 GHz gyrotron

    Based on adiabatic compression theory and electro-optical theory, a double-anode magnetron injection gun for 170 GHz gyrotron was designed. By theoretical analysis and calculations, using simulation software to simulate and optimize the electron gun, and got the result that the velocity ratio of electron beam was 1.31, the transverse velocity spread was 3.5% and the axial velocity spread was 7.1%, the beam current was 51 A. The effects of the cathode magnetic field, the control Jantage and the second anode Jantage on the properties of electron beam were discussed and found that electron beam were very sensitive with these factors. When cathode magnetic field increased, the velocity ratio of electron beam decreased, the axial velocity spread increased first and then decreased, the transverse velocity spread decreased first and then increased. The increase of the first anode Jantage could improve the velocity ratio and velocity spread of electron beam. The closer the anode angle and cathode angle, the smaller axial velocity spread. The transverse velocity spread became smaller while the anode angle changed toward the direction of reducing the distance between anode could cathode. When the two anode Jantage did not change, the increase of the distance between cathode and anode could minish the velocity spread of electron beam but the velocity ratio decreased at the same time. (authors)

  3. Low-voltage harmonic multiplying gyrotron traveling-wave amplifier in G band

    Yeh, Y. S.; Guo, Y. W.; Kao, B. H.; Chen, C. H.; Wang, Z. W. [Department of Electro-Optical Engineering, Southern Taiwan University of Science and Technology, Tainan, Taiwan (China); Hung, C. L. [Department of Communication Engineering, National Penghu University of Science and Technology, Penghu, Taiwan (China); Chang, T. H. [Department of Physics, National Tsing Hua University, Hsinchu, Taiwan (China)

    2015-12-15

    Harmonic multiplying operation in a gyrotron traveling-wave amplifier (gyro-TWA) permits for magnetic field reduction and frequency multiplication. Lowering a beam voltage is an important step toward miniaturization of a harmonic multiplying gyro-TWA. However, the additional degree of freedom that is provided by the multitude cyclotron harmonics in a low-voltage harmonic multiplying gyro-TWA still easily generates various competing modes. An improved mode-selective circuit, using circular waveguides with various radii, can provide the rejection points within the frequency range to suppress competing modes. Simulated results reveal that the mode-selective circuit can provide an attenuation of more than 14 dB to suppress the competing modes. Furthermore, the performance of the gyro-TWA is analyzed for studying the sensitivity of the saturated output power and full width at half maximum bandwidth of the gyro-TWA to the beam voltage and the magnetic field. A stable low-voltage harmonic multiplying gyro-TWA with the mode-selective circuit is predicted to yield a peak output power of 24 kW at 200.4 GHz, corresponding to a saturated gain of 56 dB at an interaction efficiency of 20%. The full width at half maximum bandwidth is 3.0 GHz.

  4. Low-order-mode harmonic multiplying gyrotron traveling-wave amplifier in W band

    Yeh, Y. S.; Chen, C. H.; Yang, S. J.; Lai, C. H.; Lin, T. Y.; Lo, Y. C.; Hong, J. W. [Department of Electro-Optical Engineering, Southern Taiwan University, Tainan, Taiwan (China); Hung, C. L. [Department of Communication Engineering, National Penghu University of Science and Technology, Penghu, Taiwan (China); Chang, T. H. [Department of Physics, National Tsing Hua University, Hsinchu, Taiwan (China)

    2012-09-15

    Harmonic multiplying gyrotron traveling-wave amplifiers (gyro-TWAs) allow for magnetic field reduction and frequency multiplication. To avoid absolute instabilities, this work proposes a W-band harmonic multiplying gyro-TWA operating at low-order modes. By amplifying a fundamental harmonic TE{sub 11} drive wave, the second harmonic component of the beam current initiates a TE{sub 21} wave to be amplified. Absolute instabilities in the gyro-TWA are suppressed by shortening the interaction circuit and increasing wall losses. Simulation results reveal that compared with Ka-band gyro-TWTs, the lower wall losses effectively suppress absolute instabilities in the W-band gyro-TWA. However, a global reflective oscillation occurs as the wall losses decrease. Increasing the length or resistivity of the lossy section can reduce the feedback of the oscillation to stabilize the amplifier. The W-band harmonic multiplying gyro-TWA is predicted to yield a peak output power of 111 kW at 98 GHz with an efficiency of 25%, a saturated gain of 26 dB, and a bandwidth of 1.6 GHz for a 60 kV, 7.5 A electron beam with an axial velocity spread of 8%.

  5. Development of a dual frequency (110/138 GHz) gyrotron for JT-60SA and its extension to an oscillation at 82 GHz

    Kobayashia Takayuki; Moriyama Shinichi; Isayama Akihiko; Sawahata Masayuki; Terakado Masayuki; Hiranai Shinichi; Wada Kenji; Sato Yoshikatsu; Hinata Jun; Yokokura Kenji; Hoshino Katsumichi; Sakamoto Keishi

    2015-01-01

    A dual-frequency gyrotron, which can generate 110 GHz and 138 GHz waves independently, is being developed in JAEA to enable electron cyclotron heating (ECH) and current drive (ECCD) in a wider range of plasma discharge conditions of JT-60SA. Conditioning operation of the gyrotron toward 1 MW for 100 s, which is the target output power and pulse length for JT-60SA, is in progress without significant problems. Oscillations of 1 MW for 10 s and 0.5 MW for 198 s were obtained, so far, at both fre...

  6. Development program for a 200 kW, CW gyrotron. Quarterly report No. 16, April-June 1983

    The objective of this program is the design and development of a millimeter-wave device to produce 200 kW of continuous wave power at 60 GHz. The device, a gyrotron oscillator, will be compatible with power delivery to an electron-cyclotron heated plasma. Smooth control of rf power over a 17 dB range is required, and the device should be capable of operation into a severely time-varying load mismatch. Progress is presented in the testing, analyses and understanding of S/N 1B behavior and in preparing S/N 3 for test in the coming report period

  7. 60 GHz gyrotron development program. Final report, April 1979-June 1984

    The original objective of this program was to develop a microwave amplifier or oscillator capable of producing 200 kW CW power output at 110 GHz. The use of cyclotron resonance interaction was pursued, and the design phases of this effort are discussed. Later, however, the program's objective was changed to develop a family of oscillators capable of producing 200 kw of peak output power at 60 GHz. Gyrotron behavior studies were performed at 28 GHz to obtain generic design information as quickly as possible. The first experimental device at 60 GHz produced over 200 kw of peak power at a pulse duration of 20 μs. Heating problems and mode interference were encountered. The second experimental tube incorporated an optimized gun location but also suffered from mode interference. The third experimental tube included modifications that reduced mode interference. It demonstrated 200 kw of peak output at 100 ms pulse duration. The fourth experimental tube, which used an older rf circuit design but in a CW configuration, produced 71.5 kW CW. The fifth experimental tube incorporated a thinner double-disc output window which improved window bandwidth and reduced window loss. This tube also incorporated modifications to the drift tunnel and cavity coupling, which had proven successful in the third experimental pulse tube tests. It produced 123 kW of CW output power at 60 GHz rf load coolant boiling and tube window failure terminated the tests. A new waterload was designed and constructed, and alternative window designs were explored

  8. Injector for a high frequency wave generating tube of the central injection Gyrotron type

    This theoretical and at the same time experimental study was carried out at the 'Service Ionique Generale' in Grenoble. High frequency wave generators are already in use there, making it possible to approach the fusion conditions of light elements such as deuterium. The plasma confined by the toroidal magnetic field uses to heat itself the electromagnetic energy provided by sources from which a good performance is required. Klystron and Magnetron are devices in which the interaction between the electric and magnetic fields of a resonating cavity and the continuous energy of a beam produces a positive result. In the Klystron, the velocity modulation is axial whereas in the Magnetron it is azimuthal. Therefore packets of electrons are formed. If this modulation of the velocities occurs radially, the beam will swell and compress periodically. The name of 'Central Injection Gyrotron' has been associated recently in the literature to this type of interaction exhibiting a good performance. Placing on trajectory the electrons forming the beam is one of the difficulties of the good working of this ultra high frenquency tube. Since no device gives safisfaction at the present time, the devising of a new type of injector specially adapted to the forming of the beam is therefore justified. The originality is that it uses on the electrostatic gun side a cathode immersed in a magnetic field of which the axial component is in the opposite direction to that which maintains the formed beam injected in the cavity. The magnetic correction of the trajectories is the most practical with respect to the experiment, providing that the electrostatic gun does not disperse them individually. This leads to seeking an improvement in the geometry of the gun. However, it will be necessary to consider the problems of power limitation due to the space charge

  9. Micro-pulses generation in ECR breakdown stimulated by gyrotron radiation at 37,5 GHz

    The present work is devoted to experimental and theoretical investigation of the creation of short pulsed (< 100 μs) multicharged ion beams. The possibility of quasi-stationary generation of short pulsed beams under conditions of quasi-gasdynamic plasma confinement was shown in recent experiments. Later another way of such beams creation based on the Pre-glow effect was proposed. In present work it was demonstrated that in the case when duration of microwave (MW) pulse is less than formation time of Pre-glow peak, realization of a regime when ion current is negligible during MW pulse and intense multicharged ions flux appears only when MW ends could be possible. Such pulses after the end of MW were called micro-pulses. In the present work the generation of micro-pulses was observed in experiments with ECR discharge stimulated by gyrotron radiation at 37,5 GHz, 100 kW. In this case pulses with duration less than 30 μs were obtained. Probably the same effect was observed in GANIL where 14 GHz radiation was used and pulses with duration about 2 ms were registered. In present work it was shown that the intensity of such micro-pulse could be higher than intensity of Pre-glow peak at the same conditions but with longer MW pulse. The generation of micro-pulses of nitrogen and argon multicharged ions with current of a few mA and length about 30 μs after MW pulse with duration of 30-100 μs was demonstrated. The low level of impurities, high current density and rather high average charge make possible to consider such micro-pulse regime as a possibility for the creation of a short pulsed ion source. The paper is followed by the slides of the presentation. (authors)

  10. TWANG-PIC, a novel gyro-averaged one-dimensional particle-in-cell code for interpretation of gyrotron experiments

    A new gyrotron simulation code for simulating the beam-wave interaction using a monomode time-dependent self-consistent model is presented. The new code TWANG-PIC is derived from the trajectory-based code TWANG by describing the electron motion in a gyro-averaged one-dimensional Particle-In-Cell (PIC) approach. In comparison to common PIC-codes, it is distinguished by its computation speed, which makes its use in parameter scans and in experiment interpretation possible. A benchmark of the new code is presented as well as a comparative study between the two codes. This study shows that the inclusion of a time-dependence in the electron equations, as it is the case in the PIC-approach, is mandatory for simulating any kind of non-stationary oscillations in gyrotrons. Finally, the new code is compared with experimental results and some implications of the violated model assumptions in the TWANG code are disclosed for a gyrotron experiment in which non-stationary regimes have been observed and for a critical case that is of interest in high power gyrotron development

  11. Three-Dimensional Numerical Simulation of a 30-GHz Gyrotron Resonator With an Explicit High-Order Discontinuous-Galerkin-Based Parallel Particle-In-Cell Method

    Stock, Andreas; Neudorfer, Jonathan; Riedlinger, Marc; Pirrung, Georg; Gassner, Gregor; Schneider, Rudolf; Roller, Sabine; Munz, Claus-Dieter

    2012-01-01

    Fast design codes for the simulation of the particle–field interaction in the interior of gyrotron resonators are available. They procure their rapidity by making strong physical simplifications and approximations, which are not known to be valid for many variations of the geometry and the operat...

  12. State-of-the-art of high power gyro-devices and free electron masers

    At present, gyrotron oscillators are mainly used as high power millimeter wave sources for electron cyclotron resonance heating (ECRH) and diagnostics of magnetically confined plasmas for generation of energy by controlled thermonuclear fusion. 140 GHz gyrotrons with output power Pout = 0.58 MW, pulse length τ = 2.0 s and efficiency η = 34% are commercially available. Diagnostic gyrotrons deliver Pout = 40 kW with τ = 40 μs at frequencies up to 650 GHz (η ≥ 4%). Recently, gyrotron oscillators have also been successfully used in material processing and plasma chemistry. Such technological applications require gyrotrons with the following parameters: f ≥ 28 GHz, Pout = 10-30 kW, CW, η ≥ 30%. This paper reports on achievements and problems related to the development of very high power mm-wave gyrotrons for long pulse or CW operation and describes the microwave technological pecularities of the different development steps. In addition, this work gives a short overview of the present development of gyrotrons for technological applications, quasi-optical gyrotrons, cyclotron autoresonance masers (CARMs), gyro-klystrons, gyro-TWT amplifiers, gyro-BWO's and free electron masers (FEMs). The most impressive FEM output parameters are: Pout = 2 GW, τ = 20 ns, η = 13% at 140 GHz (LLNL) and Pout = 15 kW, τ = 20 μs, η = 5% in the range from 120 to 900 GHz (UCSB). (orig.)

  13. Design of a Second Harmonic Double-Beam Continuous Wave Gyrotron with Operating Frequency of 0.79 THz

    Manuilov, V. N.; Glyavin, M. Yu; Sedov, A. S.; Zaslavsky, V. Yu; Idehara, T.

    2015-12-01

    This paper presents the most essential steps of a design study of a novel second harmonic gyrotron operating in CW (continuous wave) regime at a frequency of 0.79 THz and an output power of 1-100 W. It is based on a novel idea for suppression of the parasitic modes using a double-beam electron-optical system (EOS). It includes a triode magnetron injection gun (MIG), which forms two high-quality helical electron beams (HEB). Different schemes, namely one with two generating beams and another with one generating and one absorbing beam, have been investigated and compared. It has been shown that the scheme with two generating beams is more advantageous since it allows an effective suppression of the parasitic modes and a stable single-mode operation at the second harmonic resonance. A MIG which is appropriate for the realization of the latter scheme has been optimized using numerical codes for computer-aided design (CAD). It forms beams with practically equal pitch factors and moderate velocity spread. The construction of the gun is not sensitive to small misalignments and shifts of the electrodes and the magnetic field. Among the most promising characteristics of the presented design are an improved mode selection and a stable single-mode generation at currents that are two to three times higher than the currents in the single-beam (i.e., conventional) gyrotrons.

  14. Development Program for a 200-kW, c-w gyrotron. Quarterly report No. 14, October-December 1982

    The objective of this program is the design and development of a millimeter-wave device to produce 200 kW of continuous-wave power at 60 GHz. The device, a gyrotron oscillator, will be compatible with power delivery to an electron-cyclotron plasma. Smooth control of RF power output over a 17 dB range is required, and the device should be capable of operation into a severe time-varying load mismatch. Continued testing of S/N 1 A was limited by boiling in the water load. An efficiency of 48.9 percent was achieved at 3.3 amps cathode current. Extensive experimentation with eclectic water-load configurations was performed and significant progress was made toward a permanent load configuration. Testing was completed on S/N 2. This gyrotron had a limited operating range due to a nonconcentric cathode. After regunning, initial tests on S/N 2A produced 150 kW RF on the diagnostic modulator. Further investigation of a beam instability problem, which occurs under certain magnetic-field conditions, was performed on S/N 2A. Corrective action has been taken on S/N 3 to suppress this oscillation

  15. High-power pulsed gyrotron for 300 GHz-band collective Thomson scattering diagnostics in the Large Helical Device

    A high-power pulse gyrotron was developed to generate a probe wave for 300 GHz-band collective Thomson scattering (CTS) diagnostics in the Large Helical Device. In this frequency range, avoiding mode competition is critical to realizing high-power and stable oscillation with a narrow frequency bandwidth. A moderately over-moded cavity was investigated to ensure sufficient isolation of a desired mode from neighbouring modes, and to achieve high power output simultaneously. A cavity with the TE14,2 operation mode, a triode electron gun with an intense laminar electron beam, and an internal mode convertor were designed to construct a prototype tube. It was experimentally observed that oscillation of the TE14,2 mode was strong enough for mode competition, and provided high power with sufficient stability. The oscillation characteristics associated with the electron beam properties were compared with the numerical characteristics to find an optimum operating condition. As a result, single-mode operation with maximum output power of 246 kW was demonstrated at 294 GHz with 65 kV/14 A electron beam, yielding efficiency of ∼27%. The radiation pattern was confirmed to be highly Gaussian. The duration of the 130 kW pulse, which is presently limited by the power supply, was extended up to 30 µs. The experimental results validate our design concept and indicate the potential for realizing a gyrotron with higher power and longer pulse toward practical use in 300 GHz CTS diagnostics. (paper)

  16. Optimizing the coupling of output of a quasi-optical gyrotron owing to a diffraction grating with ellipsoidal support

    The output scheme of a quasi-optical gyrotron has been optimized in order to produce a gaussian output microwave beam suitable for transmission over long distances. The technique which has been applied consists of substituting one of the mirrors of the Fabry-Perot resonator in which the particle-wave interaction takes place by a diffraction grating placed in the -1 order Littrow mount and designed such that only orders -1 and 0 can propagate. In such a configuration, the diffraction angle of the order -1 coincides exactly with the incidence direction, thus providing a feedback in the cavity, whereas the order 0 constitutes the output of the resonator. A theoretical study of the power content in each diffracted order of a planar grating of infinite extent with equally spaced linear grooves as a function of the grating parameters has been performed. It has been shown that parameter domains can be found, which provide appropriate efficiencies in both orders for an application on a quasi-optical gyrotron. The Littrow condition was then adapted in order to match the spherical wavefronts of a gaussian beam incident on a possibly non-planar surface. The grooves become thus curvilinear and are no longer equally spaced. Measurements made on a cold test stand have confirmed the validity of the Littrow condition extension and allowed to determine its limits. It has also been shown that this type of cavity provides a mode having an optimal gaussian content and giving a minimal cavity transmission. The angular dispersion of the grating leads to a higher cavity transmission and to a slightly lower gaussian content for the adjacent resonator modes. The fundamental eigenmode electric field profile has been measured inside the cavity and is similar to that of an equivalent resonator made with two spherical mirrors. (author) figs., tabs., 141 refs

  17. Development of a water load for a Ka-band 10 kW continuous-wave gyrotron in an ECR ion source system

    Ok, Jung-Woo; Choi, Seyong; Lee, Byoung-Seob; Yoon, Jang-Hee; Park, Jin Yong; Shin, Chang Seouk; Won, Mi-Sook; Hong, In-Seok

    2015-02-01

    A gyrotron is used as a microwave power source in an electron-cyclotron-resonance (ECR) ion source system. In order to test the gyrotron, which operates at a frequency of 28 GHz in the continuous-wave (CW) mode, the Korea Basic Science Institute (KBSI) developed a water load that absorbed up to 10 kW of power. The water load consists of an aluminum jacket, a quartz window, and a waveguide. A distilled water flow of 13 L/min, sealed with the quartz window, is used as the absorbent. At 28 GHz, the S 11 parameter and the voltage standing-wave ratio (VSWR) of the water load design were calculated to be less than -30 dB and 1.05, respectively. In practical experiments, the increase in the water's temperature was approximately 10 °C at the highest power.

  18. Generation of electron beams in cyclotron motion and its interaction with electromagnetic fields in weakly irregular cavities: a study applied to conceptual elaboration of a 35 GHz gyrotron

    It is presented an investigation of different phenomena that occur in the gyrotron: 1) generation and transport of helical electron beams, 2) interaction of electrons in cyclotron motion with a transverse electric mode in resonant cavities operating near cutoff and 3) electron deposition over the collector active region. An exact ballistic model, which points out the nonlinear attributes of the relativistic equation of electron cyclotron motion and that includes a complex formulation for the longitudinal electric field distribution in weakly irregular waveguides, is used. Physically realizable RF field profiles are studied with the objective of maximizing gyrotron efficiency. For this purpose, an investigation is made of the resonant properties of truncated cones cavities and a new resonator type, with a profile described in terms of a continuous function, is developed. High perpendicular efficiencies (ηperpendicularMAX=0.86) have been calculated for interaction at the fundamental 1cyclotron harmonic and for uniform external magnetic field. A maximum efficiency scaling parameter S has been introduced, by which scaling relations ηperpendicularMAX= ηperpendicularMAX (S) are applicable to a variety of field profiles. The conceptual design of a 35 GHz gyrotron gives emphasis to selection criteria of operating parameters in compliance with technical constraints and with the requirement of soft self-excited oscillations. The proposed gyrotron operates in the azimuthally symetrical mode TE021 and is able to produce, with an electronic efficiency of 40%, an output power of 100 kW, in pulses of 20 ms, with a duty factor of 0.04%. (author)

  19. Control of the Superconducting Magnets current Power Supplies of the TJ-II Gyrotrons; Control de las Fuentes de Corriente de las Bobinas Superconductoras de los Girotrones del TJ-II

    Ros, A.; Fernandez, A.; Tolkachev, A.; Catalan, G.

    2006-07-01

    The TJ-II ECRH heating system consists of two gyrotrons, which can deliver a maximum power of 300 kW at a frequency of 53.2 GHz. Another 28 GHz gyrotron is going to be used in the Bernstein waves heating system. In order to get the required frequency, the gyrotrons need and homogeneous magnetic field of several tesla, which is generated by a superconducting coil field by a current source. This document describes the current source control as well as the high precision ammeters control. These ammeters measure the current in the superconducting coils. The user interface and the programming of the control system are described. The communication between devices is also explained. (author) 9 Refs.

  20. A point-like source of extreme ultraviolet radiation based on a discharge in a non-uniform gas flow, sustained by powerful gyrotron radiation of terahertz frequency band

    The possibility and prospects of extreme ultraviolet (UV) point-like source development are discussed in the present paper. The UV source is based on the discharge sustained by powerful gyrotron radiation of terahertz (THz) frequency band in non-uniform gas flow injected into vacuum volume through a nozzle with diameter less than 1 mm. Recent developments of THz-band gyrotrons with appropriate power level made such discharges possible. First experimental results on a point-like plasma creation by 100 kW radiation of 0.67 THz gyrotron are presented. The possibility of discharge localization within the area less than 1 mm is demonstrated. The discharge emission within the wavelength range from 112 nm to 650 nm was studied. The measured power of light emission in the range of 112–180 nm was measured to be up to 10 kW.

  1. Status, Operation, and Extension of the ECRH System at ASDEX Upgrade

    Wagner, D.; Stober, J.; Leuterer, F.; Monaco, F.; Müller, S.; Münich, M.; Rapson, C. J.; Reich, M.; Schubert, M.; Schütz, H.; Treutterer, W.; Zohm, H.; Thumm, M.; Scherer, T.; Meier, A.; Gantenbein, G.; Jelonnek, J.; Kasparek, W.; Lechte, C.; Plaum, B.; Goodman, T.; Litvak, A. G.; Denisov, G. G.; Chirkov, A.; Zapevalov, V.; Malygin, V.; Popov, L. G.; Nichiporenko, V. O.; Myasnikov, V. E.; Tai, E. M.; Solyanova, E. A.; Malygin, S. A.

    2016-01-01

    The upgraded electron cyclotron resonance heating (ECRH) system at ASDEX Upgrade (AUG) has been routinely used with eight gyrotrons during the last experimental campaign. A further upgrade will replace the existing system of four short-pulse (140 GHz, 2 s, 500 kW) gyrotrons. The final goal is to have around 6.5-7 MW at 140 GHz (or 5.5 MW at 105 GHz) from eight units available in the plasma during the whole AUG discharge (10 s). The system operates at 140 and 105 GHz with X2, O2 and X3 schemes. For B > 3 T also an ITER-like O1-scenario can be run using the 105 GHz option. Four of the eight launching antennas are capable of fast poloidal movements necessary for real-time control of the location of power deposition.

  2. Stabilization of the potential multi-steady-state absolute instabilities in a gyrotron traveling-wave amplifier

    The problem of spurious oscillations induced by absolute instabilities is the most challenging one that hinders the development of the millimeter-wave gyrotron traveling-wave amplifiers (gyro-TWTs). A spurious oscillation exists as a high order axial mode (HOAM) in the interaction circuit. This paper is devoted to demonstrating the complicated steady states of these HOAMs and exploring corresponding techniques to stabilize these potential multi-steady-state absolute instabilities. The stability-oriented design principle is conveyed in a start-to-end design flow of a Ka-band TE11 mode gyro-TWT. Strong magnetic tapering near the downstream port, which is capable of cutting short the effective interaction circuit of a spurious oscillation and simultaneously boosting the amplification performance, is for the first time proposed to further improve the system stability. It is also found that an ideal prebunched electron beam in the linear stage is the necessary condition to efficient amplification in the nonlinear stage, suggesting that it is feasible to design a stable prebunching stage to replace the distributed-loss-loaded linear stage. The stability-oriented design principle provides more explicit reference for future design of a zero-drive stable gyro-TWT.

  3. High power rf amplifiers for accelerator applications: The large orbit gyrotron and the high current, space charge enhanced relativistic klystron

    Stringfield, R.M.; Fazio, M.V.; Rickel, D.G.; Kwan, T.J.T.; Peratt, A.L.; Kinross-Wright, J.; Van Haaften, F.W.; Hoeberling, R.F.; Faehl, R.; Carlsten, B.; Destler, W.W.; Warner, L.B.

    1990-01-01

    Los Alamos is investigating a number of high power microwave sources for their potential to power advanced accelerators. Included in this investigation are the large orbit gyrotron amplifier and oscillator (LOG) and the relativistic klystron amplifier (RKA). LOG amplifier development is newly underway. Electron beam power levels of 3 GW, 70 ns duration, are planned, with anticipated conversion efficiencies into RF on the order of 20 percent. Ongoing investigations on this device include experimental improvement of the electron beam optics, and computational studies of resonator design and RF extraction. Recent RKA studies have operated at electron beam powers into the device of 1.35 GW in microsecond duration pulses. The device has yielded modulated electron beam power approaching 300 MW using 3--5 kW of RF input drive. RF powers extracted into waveguide have been up to 70 MW, suggesting that more power is available from the device that we have converted to-date in the extractor. We have examined several aspects of operation, including beam bunching phenomena and RF power extraction techniques. In addition, investigations of the amplifier gain as a function of input drive, electron beam parameters and axial magnetic field strength also have been explored. The effect of ions formed during device operation also has been considered.

  4. State-of-the-art of high power gyro-devices and free electron masers. Update 2005

    Gyrotron oscillators (gyromonotrons) are mainly used as high power millimeter wave sources for electron cyclotron resonance heating (ECRH), electron cyclotron current drive (ECCD), stability control and diagnostics of magnetically confined plasmas for generation of energy by controlled thermonuclear fusion. The maximum pulse length of commercially available 140 GHz, megawatt-class gyrotrons employing synthetic diamond output windows is 30 minutes (CPI and European FZK-CRPP-CEA-TED collaboration). The world record parameters of the European 140 GHz gyrotron are: 0.92 MW output power at 30 min. pulse duration, 97.5% Gaussian mode purity and 43% efficiency, employing a single-stage depressed collector for energy recovery. This results in an energy content of 1.66 GJ. A maximum output power of 1.2 MW in 4.1 s pulses was generated with the JAERI-TOSHIBA 110 GHz gyrotron. The Russian and the Japan 170 GHz ITER gyrotrons achieved 0.5 MW with pulse durations of 80 s and 500 s, respectively. Diagnostic gyrotrons deliver Pout=40 kW with τ=40 μs at frequencies up to 650 GHz (η=4%). Gyrotron oscillators have also been successfully used in materials processing. Such technological applications require gyrotrons with the following parameters: f≥24 GHz, Pout=4-50 kW, CW, η≥30%. This paper gives an update of the experimental achievements related to the development of high power gyrotron oscillators for long pulse or CW operation and pulsed gyrotrons for plasma diagnostics. In addition, this work gives a short overview of the present development status of coaxial-cavity gyrotrons, gyrotrons for technological applications, relativistic gyrotrons, quasi-optical gyrotrons, fast- and slow-wave cyclotron autoresonance masers (CARMs), gyroklystrons, gyro-TWT amplifiers, gyrotwystron amplifiers, gyro-BWO's, gyropeniotrons, magnicons, gyroharmonic converters, free electron masers (FEMs) and of vacuum windows for such high-power mm-wave sources. The highest CW powers produced by

  5. 200 kW gyrotron power supply and protection system for the electron cyclotron resonant heating experiment on Thor, CNR, Milano

    A high voltage (100 kV) regulated power supply and protection system for gyrotron has been completely developed and tested at the ENEA Laboratory of Frascati by the electrical, electronics and mechanical staff of the Technology Division. The system uses a high voltage, high power tetrode as a series voltage regulator and as a fast switching unit either to control the pulse duration (1 / 10 ms) or in the protection system, completed by a shunt crowbar as back-up protection. The crowbar is fired only if the tetrode does not clear the fault in the fixed time or when the tetrode has an arcing. In the first case the total intervention time is less than 20 μs. The main design lines of the system and the results of the tests performed on it are described. (author)

  6. Design of megawatt gyrotrons

    The design parameters of a 120 GHz gyromonotron capable of output powers in excess of 1 MW are determined. A nonlinear model of the interaction between the beam and rf field is used in which the efficiency is a function of only three normalized variables. By expressing the technological constraints in terms of these variables, permissible design parameters yielding high efficiency operation can be calculated. Constraints that are considered include ohmic heating of the walls, voltage depression of the beam, reduced coupling between the beam and rf field due to beam thickness, and efficiency degradation due to space charge forces within the beam. An analysis of the tradeoffs between current and voltage at the 1 MW level indicates that lower order modes can be utilized at lower voltages, but the constraints based on current limitations are difficult to satisfy. An 80 kV, 29 A design is presented that achieves a total efficiency of 44%. The primary uncertainty of these designs is the severity of competition due to parasitic modes. However, a number of isolated asymmetric modes appear capable of single mode emission at 1 MW based on present experimental results. Multimegawatt operation is also considered. It is shown that powers exceeding 20 MW are possible if single mode operation can be achieved in very high order modes. The methodology presented in this paper is general and can be easily adapted to other frequencies and output powers

  7. Backscattering of gyrotron radiation and short-wavelength turbulence during electron cyclotron resonance plasma heating in the L-2M stellarator

    Batanov, G. M.; Borzosekov, V. D., E-mail: tinborz@gmail.com; Kovrizhnykh, L. M.; Kolik, L. V.; Konchekov, E. M.; Malakhov, D. V.; Petrov, A. E.; Sarksyan, K. A.; Skvortsova, N. N.; Stepakhin, V. D.; Kharchev, N. K. [Russian Academy of Sciences, Prokhorov General Physics Institute (Russian Federation)

    2013-06-15

    Backscattering of gyrotron radiation ({theta} = {pi}) by short-wavelength density fluctuations (k{sub Up-Tack} = 30 cm{sup -1}) in the plasma of the L-2M stellarator was studied under conditions of electron cyclotron resonance (ECR) plasma heating at the second harmonic of the electron gyrofrequency (75 GHz). The scattering of the O-wave emerging due to the splitting of the linearly polarized gyrotron radiation into the X- and O-waves was analyzed. The signal obtained after homodyne detection of scattered radiation is a result of interference of the reference signal, the quasi-steady component, and the fast oscillating component. The coefficients of reflection of the quasi-steady component, R{sub =}{sup 2}(Y), and fast oscillating component, R{sub {approx}}{sup 2}(Y), of scattered radiation are estimated. The growth of the R{sub {approx}}{sup 2}(Y) coefficient from 3.7 Multiplication-Sign 10{sup -4} to 5.2 Multiplication-Sign 10{sup -4} with increasing ECR heating power from 190 to 430 kW is found to correlate with the decrease in the energy lifetime from 1.9 to 1.46 ms. The relative density of short-wavelength fluctuations is estimated to be Left-Pointing-Angle-Bracket n{sub {approx}}{sup 2} Right-Pointing-Angle-Bracket / Left-Pointing-Angle-Bracket n{sub e}{sup 2} Right-Pointing-Angle-Bracket = 3 Multiplication-Sign 10{sup -7}. It is shown that the frequencies of short-wavelength fluctuations are in the range 10-150 kHz. The recorded short-wavelength fluctuations can be interpreted as structural turbulence, the energy of which comprises {approx}10% of the total fluctuations energy. Simulations of transport processes show that neoclassical heat fluxes are much smaller than anomalous ones. It is suggested that short-wavelength turbulence plays a decisive role in the anomalous heat transport.

  8. Design of the magnetron injection gun for 170 GHz gyrotron%170 GHz回旋管电子枪的设计

    曾旭; 王峨锋; 刘本田; 李志良; 冯进军

    2013-01-01

      170 GHz回旋管是等离子体核聚变中电子回旋谐振加热的理想功率源,在功率上要求具有1 MW以上的输出功率。要产生这么大的输出功率,就需要具有足够大横向能量的电子注与高频场的横向电场进行互作用,因此要对电子枪进行专门的设计。利用绝热压缩理论及相关的仿真软件对双阳极磁控注入电子枪进行了设计,得到了较好的电子注参数。所设计的电子枪能在工作电压80 kV、工作电流40 A 的条件下为170 GHz 基波回旋管提供所需的回旋电子注,其引导中心半径为8.27 mm,横纵速度比1.5。%A 170 GHz gryotron is an ideal power source for the Electron Cyclotron Resonance Heating (ECRH) in the plasma fusion. The required output power from a single gyrotron tube at 170 GHz operating frequency for ECRH application is 1 MW or more. For generating the high output power,a Magnetron Injection Gun(MIG) which can provide the electron beam with large enough transverse energy for interacting with the transverse filed of the electromagnetic wave is designed. Ideal parameters of the double-anode MIG are obtained according to the adiabatic compression theory and the correlative simulation software. The designed MIG can provide the necessary beams for the 170 GHz fundamental harmonic gyrotron under 80 kV of voltage and 40 A of current with the guidance center radius of 8.27 mm and the pitch factor of 1.5.

  9. Further Characterization of 394-GHz Gyrotron FU CW GII with Additional PID Control System for 600-MHz DNP-SSNMR Spectroscopy

    Ueda, Keisuke; Matsuki, Yoh; Fujiwara, Toshimichi; Tatematsu, Yoshinori; Ogawa, Isamu; Idehara, Toshitaka

    2016-04-01

    A 394-GHz gyrotron, FU CW GII, has been designed at the University of Fukui, Japan, for dynamic nuclear polarization (DNP)-enhanced solid-state nuclear magnetic resonance (SSNMR) experiments at 600-MHz 1H resonant frequency. After installation at the Institute for Protein Research (IPR), Osaka University, Japan, a PID feedback control system was equipped to regulate the electron gun heater current for stabilization of the electron beam current, which ultimately achieved stabilization of output power when operating in continuous wave (CW) mode. During exploration to further optimize operating conditions, a continuous tuning bandwidth of approximately 1 GHz was observed by varying the operating voltage at a fixed magnetic field. In the frequency range required for positive DNP enhancement, the output power was improved by increasing the magnetic field and the operating voltage from their initial operational settings. In addition, fine tuning of output frequency by varying the cavity cooling water temperature was demonstrated. These operating conditions and ancillary enhancements are expected to contribute to further enhancement of SSNMR signal.

  10. Further Characterization of 394-GHz Gyrotron FU CW GII with Additional PID Control System for 600-MHz DNP-SSNMR Spectroscopy

    Ueda, Keisuke; Matsuki, Yoh; Fujiwara, Toshimichi; Tatematsu, Yoshinori; Ogawa, Isamu; Idehara, Toshitaka

    2016-09-01

    A 394-GHz gyrotron, FU CW GII, has been designed at the University of Fukui, Japan, for dynamic nuclear polarization (DNP)-enhanced solid-state nuclear magnetic resonance (SSNMR) experiments at 600-MHz 1H resonant frequency. After installation at the Institute for Protein Research (IPR), Osaka University, Japan, a PID feedback control system was equipped to regulate the electron gun heater current for stabilization of the electron beam current, which ultimately achieved stabilization of output power when operating in continuous wave (CW) mode. During exploration to further optimize operating conditions, a continuous tuning bandwidth of approximately 1 GHz was observed by varying the operating voltage at a fixed magnetic field. In the frequency range required for positive DNP enhancement, the output power was improved by increasing the magnetic field and the operating voltage from their initial operational settings. In addition, fine tuning of output frequency by varying the cavity cooling water temperature was demonstrated. These operating conditions and ancillary enhancements are expected to contribute to further enhancement of SSNMR signal.