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Sample records for cw 250-ghz gyrotron

  1. 250 GHz CW gyrotron oscillator for dynamic nuclear polarization in biological solid state NMR

    NASA Astrophysics Data System (ADS)

    Bajaj, Vikram S.; Hornstein, Melissa K.; Kreischer, Kenneth E.; Sirigiri, Jagadishwar R.; Woskov, Paul P.; Mak-Jurkauskas, Melody L.; Herzfeld, Judith; Temkin, Richard J.; Griffin, Robert G.

    2007-12-01

    In this paper, we describe a 250 GHz gyrotron oscillator, a critical component of an integrated system for magic angle spinning (MAS) dynamic nuclear polarization (DNP) experiments at 9 T, corresponding to 380 MHz 1H frequency. The 250 GHz gyrotron is the first gyro-device designed with the goal of seamless integration with an NMR spectrometer for routine DNP enhanced NMR spectroscopy and has operated under computer control for periods of up to 21 days with a 100% duty cycle. Following a brief historical review of the field, we present studies of the membrane protein bacteriorhodopsin (bR) using DNP enhanced multidimensional NMR. These results include assignment of active site resonances in [U- 13C, 15N]-bR and demonstrate the utility of DNP for studies of membrane proteins. Next, we review the theory of gyro-devices from quantum mechanical and classical viewpoints and discuss the unique considerations that apply to gyrotron oscillators designed for DNP experiments. We then characterize the operation of the 250 GHz gyrotron in detail, including its long-term stability and controllability. We have measured the spectral purity of the gyrotron emission using both homodyne and heterodyne techniques. Radiation intensity patterns from the corrugated waveguide that delivers power to the NMR probe were measured using two new techniques to confirm pure mode content: a thermometric approach based on the temperature-dependent color of liquid crystalline media applied to a substrate and imaging with a pyroelectric camera. We next present a detailed study of the mode excitation characteristics of the gyrotron. Exploration of the operating characteristics of several fundamental modes reveals broadband continuous frequency tuning of up to 1.8 GHz as a function of the magnetic field alone, a feature that may be exploited in future tunable gyrotron designs. Oscillation of the 250 GHz gyrotron at the second harmonic of cyclotron resonance begins at extremely low beam currents (as

  2. 250GHz CW gyrotron oscillator for dynamic nuclear polarization in biological solid state NMR.

    PubMed

    Bajaj, Vikram S; Hornstein, Melissa K; Kreischer, Kenneth E; Sirigiri, Jagadishwar R; Woskov, Paul P; Mak-Jurkauskas, Melody L; Herzfeld, Judith; Temkin, Richard J; Griffin, Robert G

    2007-12-01

    In this paper, we describe a 250 GHz gyrotron oscillator, a critical component of an integrated system for magic angle spinning (MAS) dynamic nuclear polarization (DNP) experiments at 9T, corresponding to 380 MHz (1)H frequency. The 250 GHz gyrotron is the first gyro-device designed with the goal of seamless integration with an NMR spectrometer for routine DNP enhanced NMR spectroscopy and has operated under computer control for periods of up to 21 days with a 100% duty cycle. Following a brief historical review of the field, we present studies of the membrane protein bacteriorhodopsin (bR) using DNP enhanced multidimensional NMR. These results include assignment of active site resonances in [U-(13)C, (15)N]-bR and demonstrate the utility of DNP for studies of membrane proteins. Next, we review the theory of gyro-devices from quantum mechanical and classical viewpoints and discuss the unique considerations that apply to gyrotron oscillators designed for DNP experiments. We then characterize the operation of the 250 GHz gyrotron in detail, including its long-term stability and controllability. We have measured the spectral purity of the gyrotron emission using both homodyne and heterodyne techniques. Radiation intensity patterns from the corrugated waveguide that delivers power to the NMR probe were measured using two new techniques to confirm pure mode content: a thermometric approach based on the temperature-dependent color of liquid crystalline media applied to a substrate and imaging with a pyroelectric camera. We next present a detailed study of the mode excitation characteristics of the gyrotron. Exploration of the operating characteristics of several fundamental modes reveals broadband continuous frequency tuning of up to 1.8 GHz as a function of the magnetic field alone, a feature that may be exploited in future tunable gyrotron designs. Oscillation of the 250 GHz gyrotron at the second harmonic of cyclotron resonance begins at extremely low beam currents

  3. 250 GHz CW Gyrotron Oscillator for Dynamic Nuclear Polarization in Biological Solid State NMR

    PubMed Central

    Bajaj, Vikram S.; Hornstein, Melissa K.; Kreischer, Kenneth E.; Sirigiri, Jagadishwar R.; Woskov, Paul P.; Mak-Jurkauskas, Melody L.; Herzfeld, Judith; Temkin, Richard J.; Griffin, Robert G.

    2009-01-01

    In this paper, we describe a 250 GHz gyrotron oscillator, a critical component of an integrated system for magic angle spinning (MAS) dynamic nuclear polarization (DNP) experiments at 9T, corresponding to 380 MHz 1H frequency. The 250 GHz gyrotron is the first gyro-device designed with the goal of seamless integration with an NMR spectrometer for routine DNP-enhanced NMR spectroscopy and has operated under computer control for periods of up to 21 days with a 100% duty cycle. Following a brief historical review of the field, we present studies of the membrane protein bacteriorhodopsin (bR) using DNP-enhanced multidimensional NMR. These results include assignment of active site resonances in [U-13C,15N]-bR and demonstrate the utility of DNP for studies of membrane proteins. Next, we review the theory of gyro-devices from quantum mechanical and classical viewpoints and discuss the unique considerations that apply to gyrotron oscillators designed for DNP experiments. We then characterize the operation of the 250 GHz gyrotron in detail, including its long-term stability and controllability. We have measured the spectral purity of the gyrotron emission using both homodyne and heterodyne techniques. Radiation intensity patterns from the corrugated waveguide that delivers power to the NMR probe were measured using two new techniques to confirm pure mode content: a thermometric approach based on the temperature-dependent color of liquid crystalline media applied to a substrate and imaging with a pyroelectric camera. We next present a detailed study of the mode excitation characteristics of the gyrotron. Exploration of the operating characteristics of several fundamental modes reveals broadband continuous frequency tuning of up to 1.8 GHz as a function of the magnetic field alone, a feature that may be exploited in future tunable gyrotron designs. Oscillation of the 250 GHz gyrotron at the second harmonic of cyclotron resonance begins at extremely low beam currents (as low

  4. Corrugated Waveguide and Directional Coupler for CW 250-GHz Gyrotron DNP Experiments

    PubMed Central

    Woskov, Paul P.; Bajaj, Vikram S.; Hornstein, Melissa K.; Temkin, Richard J.; Griffin, Robert G.

    2007-01-01

    A 250-GHz corrugated transmission line with a directional coupler for forward and backward power monitoring has been constructed and tested for use with a 25-W continuous-wave gyrotron for dynamic nuclear polarization (DNP) experiments. The main corrugated line (22-mm internal diameter, 2.4-m long) connects the gyrotron output to the DNP probe input. The directional coupler, inserted approximately midway, is a four-port crossed waveguide beamsplitter design. Two beamsplitters, a quartz plate and ten-wire array, were tested with output coupling of 2.5% (−16 dB) at 250.6 GHz and 1.6% (−18 dB), respectively. A pair of mirrors in the DNP probe transferred the gyrotron beam from the 22-mm waveguide to an 8-mm helically corrugated waveguide for transmission through the final 0.58-m distance inside the NMR magnet to the sample. The transmission-line components were all cold tested with a 248 ± 4-GHz radiometer. A total insertion loss of 0.8 dB was achieved for HE11 -mode propagation from the gyrotron to the sample with only 1% insertion loss for the 22-mm-diameter waveguide. A clean Gaussian gyrotron beam at the waveguide output and reliable forward power monitoring were achieved for many hours of continuous operation. PMID:17901907

  5. Corrugated Waveguide and Directional Coupler for CW 250-GHz Gyrotron DNP Experiments.

    PubMed

    Woskov, Paul P; Bajaj, Vikram S; Hornstein, Melissa K; Temkin, Richard J; Griffin, Robert G

    2005-06-01

    A 250-GHz corrugated transmission line with a directional coupler for forward and backward power monitoring has been constructed and tested for use with a 25-W continuous-wave gyrotron for dynamic nuclear polarization (DNP) experiments. The main corrugated line (22-mm internal diameter, 2.4-m long) connects the gyrotron output to the DNP probe input. The directional coupler, inserted approximately midway, is a four-port crossed waveguide beamsplitter design. Two beamsplitters, a quartz plate and ten-wire array, were tested with output coupling of 2.5% (-16 dB) at 250.6 GHz and 1.6% (-18 dB), respectively. A pair of mirrors in the DNP probe transferred the gyrotron beam from the 22-mm waveguide to an 8-mm helically corrugated waveguide for transmission through the final 0.58-m distance inside the NMR magnet to the sample. The transmission-line components were all cold tested with a 248 ± 4-GHz radiometer. A total insertion loss of 0.8 dB was achieved for HE(11) -mode propagation from the gyrotron to the sample with only 1% insertion loss for the 22-mm-diameter waveguide. A clean Gaussian gyrotron beam at the waveguide output and reliable forward power monitoring were achieved for many hours of continuous operation. PMID:17901907

  6. A 250 GHz Photonic Band Gap Gyrotron Amplifier

    NASA Astrophysics Data System (ADS)

    Nanni, Emilio A.; Lewis, Samantha M.; Shapiro, Michael A.; Temkin, Richard J.

    2012-10-01

    Initial results for a high power 250 GHz gyrotron traveling wave tube (gyro-TWT) amplifier will be presented. The amplifier uses a novel photonic band gap (PBG) interaction circuit that confines the TE03-like mode for operation. Stability from oscillations in lower order modes is provided by the PBG circuit. At 26.6 kV and 0.25 A the gyro-TWT operates with peak small signal gain of 27.3 dB at 251 GHz. The instantaneous -3 dB bandwidth of the amplifier at peak gain is 0.4 GHz. The amplifier can be tuned for operation from 245-254 GHz. A peak output power of 7.5 W has been measured. Experimental results taken over a wide range of parameters, 15-30 kV and 0.25-0.5 A, show good agreement with a theoretical model in the small signal gain regime. The theoretical model incorporates cold test measurements for the transmission line, input coupler, PBG waveguide and mode converter.

  7. Continuously Tunable 250 GHz Gyrotron with a Double Disk Window for DNP-NMR Spectroscopy

    PubMed Central

    Jawla, Sudheer; Ni, Qing Zhe; Barnes, Alexander; Guss, William; Daviso, Eugenio; Herzfeld, Judith; Griffin, Robert; Temkin, Richard

    2012-01-01

    In this paper, we describe the design and experimental results from the rebuild of a 250 GHz gyrotron used for Dynamic Nuclear Polarization enhanced Nuclear Magnetic Resonance spectroscopy on a 380 MHz spectrometer. Tuning bandwidth of approximately 2 GHz is easily achieved at a fixed magnetic field of 9.24 T and a beam current of 95 mA producing an average output power of >10 W over the entire tuning band. This tube incorporates a double disk output sapphire window in order to maximize the transmission at 250.58 GHz. DNP Signal enhancement of >125 is achieved on a 13C-Urea sample using this gyrotron. PMID:23539422

  8. Continuously Tunable 250 GHz Gyrotron with a Double Disk Window for DNP-NMR Spectroscopy.

    PubMed

    Jawla, Sudheer; Ni, Qing Zhe; Barnes, Alexander; Guss, William; Daviso, Eugenio; Herzfeld, Judith; Griffin, Robert; Temkin, Richard

    2013-01-01

    In this paper, we describe the design and experimental results from the rebuild of a 250 GHz gyrotron used for Dynamic Nuclear Polarization enhanced Nuclear Magnetic Resonance spectroscopy on a 380 MHz spectrometer. Tuning bandwidth of approximately 2 GHz is easily achieved at a fixed magnetic field of 9.24 T and a beam current of 95 mA producing an average output power of >10 W over the entire tuning band. This tube incorporates a double disk output sapphire window in order to maximize the transmission at 250.58 GHz. DNP Signal enhancement of >125 is achieved on a (13)C-Urea sample using this gyrotron. PMID:23539422

  9. Continuously Tunable 250 GHz Gyrotron with a Double Disk Window for DNP-NMR Spectroscopy

    NASA Astrophysics Data System (ADS)

    Jawla, Sudheer; Ni, Qing Zhe; Barnes, Alexander; Guss, William; Daviso, Eugenio; Herzfeld, Judith; Griffin, Robert; Temkin, Richard

    2013-01-01

    In this paper, we describe the design and experimental results from the rebuild of a 250 GHz gyrotron used for Dynamic Nuclear Polarization enhanced Nuclear Magnetic Resonance spectroscopy on a 380 MHz spectrometer. Tuning bandwidth of approximately 2 GHz is easily achieved at a fixed magnetic field of 9.24 T and a beam current of 95 mA producing an average output power of >10 W over the entire tuning band. This tube incorporates a double disk output sapphire window in order to maximize the transmission at 250.58 GHz. DNP Signal enhancement of >125 is achieved on a 13C-Urea sample using this gyrotron.

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

    PubMed

    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

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

    NASA Astrophysics Data System (ADS)

    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.

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

    PubMed Central

    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 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. PMID:22743211

  13. Dynamic nuclear polarization at 9T using a novel 250GHz gyrotron microwave source.

    PubMed

    Bajaj, V S; Farrar, C T; Hornstein, M K; Mastovsky, I; Vieregg, J; Bryant, J; Eléna, B; Kreischer, K E; Temkin, R J; Griffin, R G

    2003-02-01

    In this communication, we report enhancements of nuclear spin polarization by dynamic nuclear polarization (DNP) in static and spinning solids at a magnetic field strength of 9T (250 GHz for g=2 electrons, 380 MHz for 1H). In these experiments, 1H enhancements of up to 170+/-50 have been observed in 1-13C-glycine dispersed in a 60:40 glycerol/water matrix at temperatures of 20K; in addition, we have observed significant enhancements in 15N spectra of unoriented pf1-bacteriophage. Finally, enhancements of approximately 17 have been obtained in two-dimensional 13C-13C chemical shift correlation spectra of the amino acid U-13C, 15N-proline during magic angle spinning (MAS), demonstrating the stability of the DNP experiment for sustained acquisition and for quantitative experiments incorporating dipolar recoupling. In all cases, we have exploited the thermal mixing DNP mechanism with the nitroxide radical 4-amino-TEMPO as the paramagnetic dopant. These are the highest frequency DNP experiments performed to date and indicate that significant signal enhancements can be realized using the thermal mixing mechanism even at elevated magnetic fields. In large measure, this is due to the high microwave power output of the 250 GHz gyrotron oscillator used in these experiments. PMID:12615147

  14. Dynamic nuclear polarization at 9T using a novel 250GHz gyrotron microwave source

    PubMed Central

    Bajaj, V.S.; Farrar, C.T.; Hornstein, M.K.; Mastovsky, I.; Vieregg, J.; Bryant, J.; Eléna, B.; Kreischer, K.E.; Temkin, R.J.; Griffin, R.G.

    2010-01-01

    In this communication, we report enhancements of nuclear spin polarization by dynamic nuclear polarization (DNP) in static and spinning solids at a magnetic field strength of 9T (250 GHz for g = 2 electrons, 380 MHz for 1H). In these experiments, 1H enhancements of up to 170 ± 50 have been observed in 1-13C-glycine dispersed in a 60:40 glycerol/water matrix at temperatures of 20 K; in addition, we have observed significant enhancements in 15N spectra of unoriented pf1-bacteriophage. Finally, enhancements of ~17 have been obtained in two-dimensional 13C–13C chemical shift correlation spectra of the amino acid U-13C, 15N-proline during magic angle spinning (MAS), demonstrating the stability of the DNP experiment for sustained acquisition and for quantitative experiments incorporating dipolar recoupling. In all cases, we have exploited the thermal mixing DNP mechanism with the nitroxide radical 4-amino-TEMPO as the paramagnetic dopant. These are the highest frequency DNP experiments performed to date and indicate that significant signal enhancements can be realized using the thermal mixing mechanism even at elevated magnetic fields. In large measure, this is due to the high microwave power output of the 250 GHz gyrotron oscillator used in these experiments. PMID:12615147

  15. 2 MW CW RF load for gyrotrons

    SciTech Connect

    Lawrence Ives, R.; Marsden, David; Mizuhara, Max; Collins, George; Neilson, Jeff; Borchard, Philipp

    2011-07-01

    Final design and assembly are in progress for a 2MW CW RF load for gyrotrons. Such loads are required for testing high power gyrotrons for electron cyclotron heating of fusion plasmas. The research is building on experience with a 1 MW load to increase the power capability, reduce backscattered RF power, and improve the mechanical design. (author)

  16. Gyrotron FU CW VII for 300 MHz and 600 MHz DNP-NMR Spectroscopy

    NASA Astrophysics Data System (ADS)

    Idehara, Toshitaka; Kosuga, Kosuke; Agusu, La; Ogawa, Isamu; Takahashi, Hiroki; Smith, Mark E.; Dupree, Ray

    2010-07-01

    Gyrotron FU CW VII, one of the FU CW Series Gyrotrons, has been designed, constructed and completed operational tests successfully in the Research Center for Development of Far Infrared Region, University of Fukui (FIR FU). The gyrotron operates at around 200 GHz for the fundamental cyclotron resonances and at around 400 GHz for the second harmonics. These radiation frequencies will be applied to 300 MHz and 600 MHz DNP enhanced NMR spectroscopy.

  17. Analysis of Aftercavity Interaction in European ITER Gyrotrons and in the Compact Sub-THz Gyrotron FU CW-CI

    NASA Astrophysics Data System (ADS)

    Dumbrajs, Olgierd; Idehara, Toshitaka

    2012-12-01

    Possibilities of arising of aftercavity interaction are analyzed in the ITER 170 GHz 2 MW coaxial cavity gyrotron and the 170 GHz 1 MW cylindrical cavity gyrotron, as well as in the compact 394.5 GHz low power gyrotron FU CW-CI. Also, the simulations for the gyrotron efficiency in the presence of aftercavity interaction are performed in the cold cavity approximation. Results of the analysis illustrate the subtle interplay between the geometry of the output taper and the profile of the magnetic field.

  18. Design of a Ka Band 35 kW CW Low-Voltage Harmonic Gyrotron

    NASA Astrophysics Data System (ADS)

    Geng, Zhi-Hui; Liu, Pu-Kun; Su, Yi Nong; Xu, Shou Xi; Xue, Qian Zhong

    2010-01-01

    In this paper, a continuous wave (CW) low-voltage second harmonic gyrotron with the conventional cavity has been preliminarily designed and evaluated with self-consistent nonlinear simulation code and the particle-in-cell code CHIPIC. The simulation results of the two codes are shown to be in agreement basically. The 35 kW CW output power of the designed harmonic gyrotron driven by a 25 kV 5.0A electron beam from a magnetron injection gun (MIG) is obtained. The maximum output power and the electronic efficiency of the gyrotron is about 35 kW and 30% respectively.

  19. First 200 kW CW operation of a 60 GHz gyrotron

    SciTech Connect

    Jory, H.; Bier, R.; Evans, S.; Felch, K.; Fox, L.; Huey, H.; Shively, J.; Spang, S.

    1983-01-01

    The gyrotron is a microwave tube which employs the electron cyclotron maser interaction to produce high power output at millimeter wavelengths. It has important and growing applications for heating of plasmas in controlled thermonuclear fusion experiments. The Varian 60 GHz gyrotron has recently generated microwave power in excess of 200 kW during CW operation, wth excellent dynamic range and operating stability. This is the highest average power ever produced by a microwave tube in the millimeter wave region. A description of the gyrotron design and test results are presented.

  20. Continuous-wave Submillimeter-wave Gyrotrons

    PubMed Central

    Han, Seong-Tae; Griffin, Robert G.; Hu, Kan-Nian; Joo, Chan-Gyu; Joye, Colin D.; Mastovsky, Ivan; Shapiro, Michael A.; Sirigiri, Jagadishwar R.; Temkin, Richard J.; Torrezan, Antonio C.; Woskov, Paul P.

    2007-01-01

    Recently, dynamic nuclear polarization enhanced nuclear magnetic resonance (DNP/NMR) has emerged as a powerful technique to obtain significant enhancements in spin spectra from biological samples. For DNP in modern NMR systems, a high power continuous-wave source in the submillimeter wavelength range is necessary. Gyrotrons can deliver tens of watts of CW power at submillimeter wavelengths and are well suited for use in DNP/NMR spectrometers. To date, 140 GHz and 250 GHz gyrotrons are being employed in DNP spectrometer experiments at 200 MHz and 380 MHz at MIT. A 460 GHz gyrotron, which has operated with 8 W of CW output power, will soon be installed in a 700 MHz NMR spectrometer. High power radiation with good spectral and spatial resolution from these gyrotrons should provide NMR spectrometers with high signal enhancement through DNP. Also, these tubes operating at submillimeter wavelengths should have important applications in research in physics, chemistry, biology, materials science and medicine. PMID:17404605

  1. Continuous-wave Submillimeter-wave Gyrotrons.

    PubMed

    Han, Seong-Tae; Griffin, Robert G; Hu, Kan-Nian; Joo, Chan-Gyu; Joye, Colin D; Mastovsky, Ivan; Shapiro, Michael A; Sirigiri, Jagadishwar R; Temkin, Richard J; Torrezan, Antonio C; Woskov, Paul P

    2006-01-01

    Recently, dynamic nuclear polarization enhanced nuclear magnetic resonance (DNP/NMR) has emerged as a powerful technique to obtain significant enhancements in spin spectra from biological samples. For DNP in modern NMR systems, a high power continuous-wave source in the submillimeter wavelength range is necessary. Gyrotrons can deliver tens of watts of CW power at submillimeter wavelengths and are well suited for use in DNP/NMR spectrometers. To date, 140 GHz and 250 GHz gyrotrons are being employed in DNP spectrometer experiments at 200 MHz and 380 MHz at MIT. A 460 GHz gyrotron, which has operated with 8 W of CW output power, will soon be installed in a 700 MHz NMR spectrometer. High power radiation with good spectral and spatial resolution from these gyrotrons should provide NMR spectrometers with high signal enhancement through DNP. Also, these tubes operating at submillimeter wavelengths should have important applications in research in physics, chemistry, biology, materials science and medicine. PMID:17404605

  2. Continuous-wave submillimeter-wave gyrotrons

    NASA Astrophysics Data System (ADS)

    Han, Seong-Tae; Griffin, Robert G.; Hu, Kan-Nian; Joo, Chan-Gyu; Joye, Colin D.; Mastovsky, Ivan; Shapiro, Michael A.; Sirigiri, Jagadishwar R.; Temkin, Richard J.; Torrezan, Antonio C.; Woskov, Paul P.

    2006-10-01

    Recently, dynamic nuclear polarization enhanced nuclear magnetic resonance (DNP/NMR) has emerged as a powerful technique to obtain significant enhancements in spin spectra from biological samples. For DNP in modern NMR systems, a high power continuous-wave source in the submillimeter wavelength range is necessary. Gyrotrons can deliver tens of watts of CW power at submillimeter wavelengths and are well suited for use in DNP/NMR spectrometers. To date, 140 GHz and 250 GHz gyrotrons are being employed in DNP spectrometer experiments at 200 MHz and 380 MHz at MIT. A 460 GHz gyrotron, which has operated with 8 W of CW output power, will soon be installed in a 700 MHz NMR spectrometer. High power radiation with good spectral and spatial resolution from these gyrotrons should provide NMR spectrometers with high signal enhancement through DNP. Also, these tubes operating at submillimeter wavelengths should have important applications in research in physics, chemistry, biology, materials science and medicine.

  3. 94 GHz, 25 kW CW, Harmonic Complex-Cavity Gyrotron

    NASA Astrophysics Data System (ADS)

    McDermott, D. B.; Balkcum Luhmann, A. J., Jr.

    1997-11-01

    A low-voltage second-harmonic gyrotron has been designed and evaluated with a particle-tracing code and the PIC code MAGIC. The two codes are shown to be in excellent agreement when applied to a conventional fundamental-frequency gyrotron and also to the novel second-harmonic gyrotron. The 25 kW CW, 94 GHz gyrotron with a predicted conversion efficiency of 28.5% and device efficiency of 20% is driven by a 25 kV, 5 A, v_t/v_z=1.5, MIG electron beam with 15% axial velocity spread and employs a TE_021/TE_031 complex cavity for mode control. The compact 17 kG solenoid magnet utilizes the tremendous advances made in high-Tc superconducting technology. However, the 94 GHz prototype will be tested at low duty in pulse mode with a conventional low-Tc superconducting magnet that has been received and tested.

  4. Design studies of the output system of a 95 GHz, 100 kW, CW gyrotron

    SciTech Connect

    Vamshi Krishna, P.; Kartikeyan, M.V. E-mail: kartik@iitr.ernet.in; Thumm, M.

    2011-07-01

    This paper presents the design studies of the output system of a 95 GHz, 100 kW, CW gyrotron for ECRH7ECRIS applications. During this course, the design studies of an advanced dimpled-wall quasi optical launcher, non-linear taper and RF window will be carried out. (author)

  5. Mode selection and resonator design studies of a 95 GHz, 100 kW, CW gyrotron

    SciTech Connect

    Vamshi Krishna, P.; Kartikeyan, M.V. E-mail: kartik@iitr.ernet.in; Thumm, M.

    2011-07-01

    In this paper, the mode selection procedure leading to the design and the cavity resonator design studies of a 95 GHz, 100 kW, CW Gyrotron will be presented, such a gyrotron will be used for specific ECRH/ECRIS applications. In this course all the suitable modes with design constraints within the limits of design goals are considered and finally the TE{sub 10.4} mode is chosen as the operating mode which is suitable for the design. Design constraints are carefully investigated, and starting currents are computed. (author)

  6. Design of a multistage depressed collector system for 1 MW CW gyrotrons. Part 2: System consideration

    SciTech Connect

    Ives, R.L.; Mizuhara, M.; Schumacher, R.; Neilson, J. ); Singh, A.; Granatstein, V.L. . Inst. for Plasma Research); Gaudreau, M.; Casey, J.A. )

    1999-04-01

    Part 2 describes the basic mechanical design of the two-stage collector, including the thermal performance. The design should be applicable to Gaussian mode gyrotrons over a very broad frequency range at power levels up to one megawatt CW. Part 2 also describes an innovative regenerative power supply system that utilizes highly efficient, solid state, switching technology that provides high reliability and significantly reduced cost over conventional technology. An advanced computer control system that will provide user-friendly gyrotron operation and allow modes of operation not possible with manual operation is also being developed.

  7. Millimeter wave, 25 kW CW gyrotrons using permanent-magnets

    SciTech Connect

    McDermott, D.B.; Luhmann, N.C. Jr.

    1996-12-31

    Two compact 25 kW cw, low magnetic field gyrotrons have been designed for use in Ka-Band and W-Band systems. Both 50 kV devices have been designed to minimize their size and weight by using a 4.5 kG Samarium cobalt permanent magnet. Their designs are presented. The 35 GHz gyrotron uses a 3 A MIG and operates at the third harmonic in the TE{sub 411} mode of a smooth-bore cylindrical cavity. For an output power of 25 kW, the predicted conversion efficiency is 25%, yielding an output efficiency of 17%. An ideal 33 kV single-stage depressed collector following a magnetic downtaper could increase the device efficiency to 50%. The 94 GHz gyrotron utilizes a Cusp gun and operates at the eight-harmonic in a sixteen-vane slotted cavity. The efficiency of the 95 GHz gyrotron is predicted to be 10%, which could also be boosted to {approximately} 50% with a depressed collector. Either device can be reconfigured as a tunable gyro-BWO. Mode competition will be controlled in both gyrotrons by slicing the cavities to interrupt the azimuthal wall currents of unwanted modes as utilized recently in the successful second-harmonic TE{sub 21} gyro-TWT amplifier experiment.

  8. Development of a Compact sub-THz Gyrotron FU CW CI for Application to High Power THz Technologies

    NASA Astrophysics Data System (ADS)

    Idehara, Toshitaka; Mudiganti, Jagadish C.; Agusu, La; Kanemaki, Tomohiro; Ogawa, Isamu; Fujiwara, Toshimichi; Matsuki, Yoh; Ueda, Keisuke

    2012-07-01

    For application of high frequency gyrotron to high power THz technology, Gyrotron FU CW series is being developed in FIR FU. Gyrotron FU CW CI is developed as one of sub-THz gyrotrons included in the series. The advantage of the gyrotron is compactness using a compact superconducting magnet and compact power supply system, which makes the accesses of the gyrotron to applied large-scale devices easier and extends the applications of gyrotron to wider fields. The designed frequency and cavity mode are 394.5 GHz and TE26 mode for application to the 600 MHz DNP-NMR spectroscopy. As the operation results, the frequency and the output power were 394.03 GHz and around 30 W, respectively, which are available for the application to the 600 MHz DNP-NMR measurement. In addition, this gyrotron can operate at many other frequencies and cavity modes for application to high power THz technologies in wide fields. In this paper, the design and the operation results including long pulse or CW mode are presented.

  9. Efficient Low-Voltage Operation of a CW Gyrotron Oscillator at 233 GHz

    PubMed Central

    Hornstein, Melissa K.; Bajaj, Vikram S.; Griffin, Robert G.; Temkin, Richard J.

    2007-01-01

    The gyrotron oscillator is a source of high average power millimeter-wave through terahertz radiation. In this paper, we report low beam power and high-efficiency operation of a tunable gyrotron oscillator at 233 GHz. The low-voltage operating mode provides a path to further miniaturization of the gyrotron through reduction in the size of the electron gun, power supply, collector, and cooling system, which will benefit industrial and scientific applications requiring portability. Detailed studies of low-voltage operation in the TE2,3,1 mode reveal that the mode can be excited with less than 7 W of beam power at 3.5 kV. During CW operation with 3.5-kV beam voltage and 50-mA beam current, the gyrotron generates 12 W of RF power at 233.2 GHz. The EGUN electron optics code describes the low-voltage operation of the electron gun. Using gun-operating parameters derived from EGUN simulations, we show that a linear theory adequately predicts the low experimental starting currents. PMID:17687412

  10. Efficient Low-Voltage Operation of a CW Gyrotron Oscillator at 233 GHz.

    PubMed

    Hornstein, Melissa K; Bajaj, Vikram S; Griffin, Robert G; Temkin, Richard J

    2007-02-01

    The gyrotron oscillator is a source of high average power millimeter-wave through terahertz radiation. In this paper, we report low beam power and high-efficiency operation of a tunable gyrotron oscillator at 233 GHz. The low-voltage operating mode provides a path to further miniaturization of the gyrotron through reduction in the size of the electron gun, power supply, collector, and cooling system, which will benefit industrial and scientific applications requiring portability. Detailed studies of low-voltage operation in the TE(2) (,) (3) (,) (1) mode reveal that the mode can be excited with less than 7 W of beam power at 3.5 kV. During CW operation with 3.5-kV beam voltage and 50-mA beam current, the gyrotron generates 12 W of RF power at 233.2 GHz. The EGUN electron optics code describes the low-voltage operation of the electron gun. Using gun-operating parameters derived from EGUN simulations, we show that a linear theory adequately predicts the low experimental starting currents. PMID:17687412

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

    SciTech Connect

    Felch, K.; Feinstein, J.; Hess, C.; Huey, H.; Jongewaard, E.; Jory, H.; Neilson, J.; Pendleton, R.; Pirkle, D.; Zitelli, L. )

    1989-09-01

    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 TE{sub 15,2,1} 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.

  12. Design considerations for a 100 kW c-w, 140 GHz gyrotron oscillator

    SciTech Connect

    Felch, K.; Bier, R.; Fox, L.; Huey, H.; Ives, L.; Jory, H.; Spang, S.

    1984-01-01

    A gyrotron oscillator capable of generating 100 kW of c-w power is currently under development at Varian. The tube is being designed for operation in the TE/sup 0//sub 031/ cavity mode with the electron beam located at the second radial electric field maximum in the cavity. The electron beam will be produced by a magnetron injection gun and the 56 kG magnetic field required for 140 GHz operation will be provided by a superconducting magnet. Initial design calculations for the important elements of the tube are reported and the various technology issues of the tube design are discussed.

  13. The 28 GHZ, 10 KW, CW Gyrotron Generator for the VENUS ECR Ion Source at LBNL

    NASA Astrophysics Data System (ADS)

    Marks, M.; Evans, S.; Jory, H.; Holstein, D.; Rizzo, R.; Beck, P.; Cisto, B.; Leitner, D.; Lyneis, C. M.; Collins, D.; Dwinell, R. D.

    2005-03-01

    The VIA-301 Heatwave™ gyrotron generator was specifically designed to meet the requirements of the Venus ECR Ion Source at the Lawrence Berkeley National Laboratory (LBNL). VENUS (Versatile ECR ion source for NUclear Science) is a next generation superconducting ECR ion source, designed to produce high current, high charge state ions for the 88-Inch Cyclotron at the Lawrence Berkeley National Laboratory. VENUS also serves as the prototype ion source for the RIA (Rare Isotope Accelerator) front end [1]. This VIA-301 Heatwave™ gyrotron system provides 100 watts to 10 kW continuous wave (CW) RF output at 28 GHz. The RF output level is smoothly controllable throughout this entire range. The power can be set and maintained to within 10 watts at the higher power end of the power range and to within 30 watts at the lower power end of the power range. A dual directional coupler, analog conditioning circuitry, and a 12-bit analog input to the embedded controller are used to provide a power measurement accurate to within 2%. The embedded controller completes a feedback loop using an external command set point for desired power output. Typical control-loop-time is on the order of 500 mS. Hard-wired interlocks are provided for personnel safety and for protection of the generator system. In addition, there are software controlled interlocks for protection of the generator from high ambient temperature, high water temperature, and other conditions that would affect the performance of the generator or reduce the lifetime of the gyrotron. Cooling of the gyrotron and power supply is achieved using both water and forced circulation of ambient air. Water-cooling provides about 80% of the cooling requirement. Input power to the generator from the prime power line is less than 60 kW at full power. The Heatwave™ may be operated locally via its front panel or remotely via either RS-232 and/or Ethernet connections. Through the RS-232 the forward power, the reflected power, the

  14. The 28 GHZ, 10 KW, CW Gyrotron Generator for the VENUS ECR Ion Source at LBNL

    SciTech Connect

    Marks, M.; Evans, S.; Jory, H.; Holstein, D.; Rizzo, R.; Beck, P.; Cisto, B.; Leitner, D.; Lyneis, C.M.; Collins, D.; Dwinell, R.D.

    2005-03-15

    The VIA-301 Heatwave{sup TM} gyrotron generator was specifically designed to meet the requirements of the Venus ECR Ion Source at the Lawrence Berkeley National Laboratory (LBNL). VENUS (Versatile ECR ion source for NUclear Science) is a next generation superconducting ECR ion source, designed to produce high current, high charge state ions for the 88-Inch Cyclotron at the Lawrence Berkeley National Laboratory. VENUS also serves as the prototype ion source for the RIA (Rare Isotope Accelerator) front end].This VIA-301 Heatwave{sup TM} gyrotron system provides 100 watts to 10 kW continuous wave (CW) RF output at 28 GHz. The RF output level is smoothly controllable throughout this entire range. The power can be set and maintained to within 10 watts at the higher power end of the power range and to within 30 watts at the lower power end of the power range. A dual directional coupler, analog conditioning circuitry, and a 12-bit analog input to the embedded controller are used to provide a power measurement accurate to within 2%. The embedded controller completes a feedback loop using an external command set point for desired power output. Typical control-loop-time is on the order of 500 mS. Hard-wired interlocks are provided for personnel safety and for protection of the generator system. In addition, there are software controlled interlocks for protection of the generator from high ambient temperature, high water temperature, and other conditions that would affect the performance of the generator or reduce the lifetime of the gyrotron. Cooling of the gyrotron and power supply is achieved using both water and forced circulation of ambient air. Water-cooling provides about 80% of the cooling requirement. Input power to the generator from the prime power line is less than 60 kW at full power. The Heatwave{sup TM} may be operated locally via its front panel or remotely via either RS-232 and/or Ethernet connections. Through the RS-232 the forward power, the reflected power

  15. Analysis of oscillation characteristics and optimal conditions for high power operation of Gyrotron FU CW GIII

    SciTech Connect

    Tatematsu, Y. Yamaguchi, Y.; Kawase, T.; Ichioka, R.; Ogawa, I.; Saito, T.; Idehara, T.

    2014-08-15

    The oscillation characteristics of Gyrotron FU CW GIII and its wave frequency and output power dependences on the magnetic field strength, the gun coil current, and the anode voltage were investigated experimentally. The experimental results were analyzed theoretically using a self-consistent code that included the electron properties in the cavity, corresponding to the actual operating conditions in the experiments. As a result, it was found that the variation in frequency with the magnetic field strength was related to an axial profile change in the electromagnetic wave in the cavity. In addition, the optimal condition that gives the maximum output power was found to be determined by the pitch factor rather than by the electron beam radius under the given operating conditions.

  16. Detailed Consideration of Experimental Results of Gyrotron FU CW II Developed as a Radiation Source for DNP-NMR Spectroscopy

    NASA Astrophysics Data System (ADS)

    Agusu, La; Idehara, T.; Ogawa, I.; Saito, T.; Kanemaki, T.; Takahashi, H.; Fujiwara, T.

    2007-07-01

    A CW gyrotron for the sensitivity enhancement of NMR spectroscopy through dynamic nuclear polarization has been designed. The gyrotron operates at the second harmonic and frequency of 394.6 GHz with the main operating mode TE0,6. Operating conditions of other neighboring cavity modes such as TE2,6 at frequency of 392.6 GHz and TE2,3 at frequency of 200.7 GHz were also considered. The experimental conditions of the gyrotron at low and high voltages are simulated. The output power of 56 watts corresponds to the efficiency of 2 percent at low voltage operation and frequency of 394.6 GHz is expected.

  17. Continuously Frequency Tunable High Power Sub-THz Radiation Source—Gyrotron FU CW VI for 600 MHz DNP-NMR Spectroscopy

    NASA Astrophysics Data System (ADS)

    Idehara, Toshitaka; Kosuga, Kosuke; Agusu, La; Ikeda, Ryosuke; Ogawa, Isamu; Saito, Teruo; Matsuki, Yoh; Ueda, Keisuke; Fujiwara, Toshimichi

    2010-07-01

    A high frequency gyrotron with a 15 T superconducting magnet named Gyrotron FU CW VI has achieved continuous frequency tuning through the relatively wide range of 1.5 GHz near 400 GHz. The operation is at the fundamental cyclotron resonance of the TE06 cavity mode with many higher order axial modes. The output power measured at the end of the circular waveguide system ranges from 10 to 50 watts at the low acceleration voltage of 12 kV for beam electrons. The beam current is also low. It is around 250 mA. This gyrotron is designed as a demountable radiation source for the 600 MHz DNP-NMR spectroscopy. The design and operation results of the gyrotron FU CW VI are presented.

  18. Development program for a 200-kW, CW gyrotron. Quarterly report No. 5, July-September 1980

    SciTech Connect

    Tancredi, J.J.; Caplan, M.; Adler, E.A.; Sandoval, J.J.

    1980-01-01

    During this report period, the electrical design of the CW tube was completed. The mechanical design of a collector, capable of providing diagnostic data of the spent beam in S/N 1 was completed. Cold tests of variations of a scaled, X-band cavity were correlated with the calculated results of a cavity computer code. Parts for the magnetron injection gun were placed on order and gun tooling was designed. A subcontract was placed for a superconducting solenoid. A 3 MW power supply was dismantled, packaged and shipped from the Kwajalein Missile Range to storage at Hughes, for use in CW testing at a later date. During the latter part of this report period, a specific interim goal was imposed by ORNL, to provide for a demonstration of a 200 kW, 60 GHz gyrotron capable of 100 ms pulses, by December 31, 1981. The imposition of this interim goal has led to establishing a modified gyrotron design, based on a considerably smaller collector than that required for a CW tube.

  19. Beam-wave interaction analysis of a 42 GHz, 200 kW CW gyrotron

    SciTech Connect

    Ashutosh; Singh, Rupendra; Jain, P.K. E-mail: rupendrasingh04@gmail.com

    2011-07-01

    In this paper, the self-consistent large-signal formulation is used to study the beam-wave interaction mechanism in a gyrotron oscillator. The nonlinear interaction has been computed by solving the set of self-consistent nonlinear equations along the interaction length using numerical method. Consequently, the computation of energy, phase, output power, and efficiency of a gyrotron is made. The computed results were found to be matching with the published results. A 42 GHz, 200 kW output power gyrotron operating in TE{sub 03} mode is analysed using this analysis and results found meeting desired specifications. (author)

  20. 35-GHz 25-kW CW low-voltage third-harmonic gyrotron

    SciTech Connect

    McDermott, D.B.; Balkcum, A.J.; Luhmann, N.C. Jr.

    1996-06-01

    A 50-kV third-harmonic gyrotron is shown to be capable of high efficiency. Operation at the third harmonic allows the required magnetic field for 35 GHz generation to be supplied by a 4.5-kG permanent magnet. Two gyrotrons employing sliced circuits for mode control have been evaluated with a large-signal nonself-consistent particle-tracing simulation code and found to be capable of producing 25 kW continuously. The preliminary design of a third-harmonic TE{sub 41} gyrotron utilizing a magnetron injection electron gun is predicted to yield a device efficiency of 17%, which can potentially be increased to 46% with an ideal single-stage depressed collector, while an axis-encircling electron beam from a Cusp electron gun is predicted to drive a third-harmonic TE{sub 31} gyrotron with a device efficiency of 23%, which can theoretically be increased to 45% through the use of an ideal depressed collector.

  1. Development program for a 200 kW, CW gyrotron. Quarterly report No. 4, April-June 1980

    SciTech Connect

    Tancredi, J.J.; Caplan, M.; Sandoval, J.J.; Weiss, W.

    1980-01-01

    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, which will be 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-varyinng rf load mismatch.

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

    NASA Astrophysics Data System (ADS)

    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.

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

    NASA Astrophysics Data System (ADS)

    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.

  4. Functional and shunt states of bacteriorhodopsin resolved by 250 GHz dynamic nuclear polarization–enhanced solid-state NMR

    PubMed Central

    Bajaj, Vikram S.; Mak-Jurkauskas, Melody L.; Belenky, Marina; Herzfeld, Judith; Griffin, Robert G.

    2009-01-01

    Observation and structural studies of reaction intermediates of proteins are challenging because of the mixtures of states usually present at low concentrations. Here, we use a 250 GHz gyrotron (cyclotron resonance maser) and cryogenic temperatures to perform high-frequency dynamic nuclear polarization (DNP) NMR experiments that enhance sensitivity in magic-angle spinning NMR spectra of cryo-trapped photocycle intermediates of bacteriorhodopsin (bR) by a factor of ≈90. Multidimensional spectroscopy of U-13C,15N-labeled samples resolved coexisting states and allowed chemical shift assignments in the retinylidene chromophore for several intermediates not observed previously. The correlation spectra reveal unexpected heterogeneity in dark-adapted bR, distortion in the K state, and, most importantly, 4 discrete L substates. Thermal relaxation of the mixture of L's showed that 3 of these substates revert to bR568 and that only the 1 substate with both the strongest counterion and a fully relaxed 13-cis bond is functional. These definitive observations of functional and shunt states in the bR photocycle provide a preview of the mechanistic insights that will be accessible in membrane proteins via sensitivity-enhanced DNP NMR. These observations would have not been possible absent the signal enhancement available from DNP. PMID:19474298

  5. Functional and shunt states of bacteriorhodopsin resolved by 250 GHz dynamic nuclear polarization-enhanced solid-state NMR.

    PubMed

    Bajaj, Vikram S; Mak-Jurkauskas, Melody L; Belenky, Marina; Herzfeld, Judith; Griffin, Robert G

    2009-06-01

    Observation and structural studies of reaction intermediates of proteins are challenging because of the mixtures of states usually present at low concentrations. Here, we use a 250 GHz gyrotron (cyclotron resonance maser) and cryogenic temperatures to perform high-frequency dynamic nuclear polarization (DNP) NMR experiments that enhance sensitivity in magic-angle spinning NMR spectra of cryo-trapped photocycle intermediates of bacteriorhodopsin (bR) by a factor of approximately 90. Multidimensional spectroscopy of U-(13)C,(15)N-labeled samples resolved coexisting states and allowed chemical shift assignments in the retinylidene chromophore for several intermediates not observed previously. The correlation spectra reveal unexpected heterogeneity in dark-adapted bR, distortion in the K state, and, most importantly, 4 discrete L substates. Thermal relaxation of the mixture of L's showed that 3 of these substates revert to bR(568) and that only the 1 substate with both the strongest counterion and a fully relaxed 13-cis bond is functional. These definitive observations of functional and shunt states in the bR photocycle provide a preview of the mechanistic insights that will be accessible in membrane proteins via sensitivity-enhanced DNP NMR. These observations would have not been possible absent the signal enhancement available from DNP. PMID:19474298

  6. First demonstration of a vehicle mounted 250GHz real time passive imager

    NASA Astrophysics Data System (ADS)

    Mann, Chris

    2009-05-01

    This paper describes the design and performance of a ruggedized passive Terahertz imager, the frequency of operation is a 40GHz band centred around 250GHz. This system has been specifically targeted at vehicle mounted operation, outdoors in extreme environments. The unit incorporates temperature stabilization along with an anti-vibration chassis and is sealed to allow it to be used in a dusty environment. Within the system, a 250GHz heterodyne detector array is mated with optics and scanner to allow real time imaging out to 100 meters. First applications are envisaged to be stand-off, person borne IED detection to 30 meters but the unique properties in this frequency band present other potential uses such as seeing through smoke and fog. The possibility for use as a landing aid is discussed. A detailed description of the system design and video examples of typical imaging output will be presented.

  7. A 250-GHz CARM (Cyclotron Auto Resonance Maser) oscillator experiment driven by an induction linac

    SciTech Connect

    Caplan, M.; Kulke, B.; Bubp, D.G. ); McDermott, D.; Luhmann, N. )

    1990-09-14

    A 250-GHz Cyclotron Auto Resonance Maser (CARM) oscillator has been designed and constructed and will be tested using a 1-kA, 2-MeV electron beam produced by the induction linac at the Accelerator Research Center (ARC) facility of Lawrence Livermore National Laboratory (LLNL). The oscillator circuit was made to operate in the TE{sub 11} mode at ten times cutoff using waveguide Bragg reflectors to create an external cavity Q of 8000. Theory predicts cavity fill times of less than 30 ns (pulse length) and efficiencies approaching 20% is sufficiently low transverse electron velocity spreads are maintained (2%).

  8. Design of an induction linac driven CARM (Cyclotron Auto Resonance Maser) oscillator at 250 GHz

    SciTech Connect

    Caplan, M.; Kulke, B.

    1990-01-24

    We present the design of a 250 GHz, 400 MW Cyclotron Auto Resonance Maser (CARM) oscillator driven by a 1 KA, 2 MeV electron beam produced by the induction linac at the ARC facility of LLNL. The oscillator circuit is designed as a feedback amplifier operating in the TE{sub 11} mode at ten times cutoff terminated at each end with Bragg reflectors. Theory and cold test results are in good agreement for a manufactured Bragg reflector using 50 {mu}m corrugations to ensure mode purity. The CARM is to be operational by February 1990. 3 figs., 2 tabs.

  9. Pierce-Wiggler electron beam system for 250 GHz GYRO-BWO: Final report

    SciTech Connect

    Pirkle, D.R.; Alford, C.W.; Anderson, M.H.; Garcia, R.F.; Legarra, J.R.; Nordquist, A.L.

    1989-01-01

    This final report summarizes the design and performance of the VUW-8028 Pierce-Wiggler electron beam systems, which can be used to power high frequency gyro-BWO's. The operator's manual for this gyro-BWO beamstick is included as appendix A. Researchers at Lawrence Livermore National Laboratory (LLNL) are developing a gyro-BWO with a center frequency of 250 GHz, 6% bandwidth, and 10 kV peak output power. The gyro-BWO will be used to drive a free electron laser amplifier at LLNL. The electron beam requirements of the gyro-BWO application are: Small beam size, .100 inch at 2500 gauss axial magnetic field; a large fraction of the electron energy in rotational velocity; ability to vary the electrons' axial velocity easily, for electronic tuning; and low velocity spread i.e. little variation in the axial velocities of the electrons in the interaction region. 1 ref., 13 figs.

  10. 250-GHz electron spin resonance studies of polarity gradients along the aliphatic chains in phospholipid membranes.

    PubMed Central

    Earle, K. A.; Moscicki, J. K.; Ge, M.; Budil, D. E.; Freed, J. H.

    1994-01-01

    Rigid-limit 250-GHz electron spin resonance (FIR-ESR) spectra have been studied for a series of phosphatidylcholine spin labels (n-PC, where n = 5, 7, 10, 12, 16) in pure lipid dispersions of dipalmitoylphosphatidylcholine (DPPC) and 1-palmitoyl-2-oleoylphosphatidylcholine (POPC), as well as dispersions of DPPC containing the peptide gramicidin A (GA) in a 1:1 molar ratio. The enhanced g-tensor resolution of 250-GHz ESR for these spin labels permitted a careful study of the nitroxide g-tensor as a function of spin probe location and membrane composition. In particular, as the spin label is displaced from the polar head group, Azz decreases and gxx increases as they assume values typical of a nonpolar environment, appropriate for the hydrophobic alkyl chains in the case of pure lipid dispersions. The field shifts of spectral features due to changes in gxx are an order of magnitude larger than those from changes in Azz. The magnetic tensor parameters measured in the presence of GA were characteristic of a polar environment and showed only a very weak dependence of Azz and gxx on label position. These results demonstrate the significant influence of GA on the local polarity along the lipid molecule, and may reflect increased penetration of water into the alkyl chain region of the lipid in the presence of GA. The spectra from the pure lipid dispersions also exhibit a broad background signal that is most significant for 7-, 10-, and 12-PC, and is more pronounced in DPPC than in POPC. It is attributed to spin probe aggregation yielding spin exchange narrowing. The addition of GA to DPPC essentially suppressed the broad background signal observed in pure DPPC dispersions. PMID:7518705

  11. Status of gyrotron developments at Varian Associates

    SciTech Connect

    Jory, H.

    1984-01-01

    The status of gyrotrons developed by Varian for fusion heating applications will be briefly reviewed. Development work started in 1976 with the goal of 200 kW CW at 28 GHz. A more recent program was to develop 200 kW CW at 60 GHz. Pulsed and CW tubes produced by these programs will be briefly described and the scaling of these designs to other frequencies including 53, 56 and 70 GHz will be discussed. A 35 GHz design will also be described. Future efforts for gyrotrons at 120 and 140 GHz will also be discussed.

  12. Dynamic nuclear polarization at 9T using a novel 250 gyrotron microwave source.

    PubMed

    Griffin, Robert G

    2011-12-01

    In the 1990's we initiated development of high frequency gyrotron microwave sources with the goal of performing dynamic nuclear polarization at magnetic fields (∼5-23 T) used in contemporary NMR experiments. This article describes the motivation for these efforts and the developments that led to the operation of a gyrotron source for DNP operating at 250 GHz. We also mention results obtained with this instrument that would have been otherwise impossible absent the increased sensitivity. Finally, we describe recent efforts that have extended DNP to 460 GHz and 700 MHz (1)H frequencies. PMID:22152359

  13. Dynamic nuclear polarization at 9T using a novel 250 Gyrotron microwave source

    NASA Astrophysics Data System (ADS)

    Griffin, Robert G.

    2011-12-01

    In the 1990's we initiated development of high frequency gyrotron microwave sources with the goal of performing dynamic nuclear polarization at magnetic fields (˜5-23 T) used in contemporary NMR experiments. This article describes the motivation for these efforts and the developments that led to the operation of a gyrotron source for DNP operating at 250 GHz. We also mention results obtained with this instrument that would have been otherwise impossible absent the increased sensitivity. Finally, we describe recent efforts that have extended DNP to 460 GHz and 700 MHz 1H frequencies.

  14. Progress of high power 170 GHz gyrotron in JAEA

    NASA Astrophysics Data System (ADS)

    Sakamoto, Keishi; Kasugai, Atsushi; Kajiwara, Ken; Takahashi, Koji; Oda, Yasuhisa; Hayashi, Kazuo; Kobayashi, Noriyuki

    2009-09-01

    Recent progress on the high power gyrotron development in JAEA is presented. The gyrotron is featured to have a triode-type magnetron injection gun, a cylindrical resonator working at 170 GHz with TE31,8 mode, a water-cooled diamond window and a depressed collector. After the demonstration of the ITER basic performance, the gyrotron has been operated for 3 years, and recorded ~200 GJ of total output energy. Next, a gyrotron which oscillates in higher order resonator mode, TE31,12, is designed and fabricated to study the long pulse oscillation at greater than 1 MW. In parallel, feasibility studies of a CW-power modulation for neoclassical tearing mode stabilization, a dual frequency gyrotron and a rapid frequency control are carried out. It is shown that these gyrotrons will be available with current technology.

  15. Innovation on high-power long-pulse gyrotrons

    NASA Astrophysics Data System (ADS)

    Litvak, Alexander; Sakamoto, Keishi; Thumm, Manfred

    2011-12-01

    Progress in the worldwide development of high-power gyrotrons for magnetic confinement fusion plasma applications is described. After technology breakthroughs in research on gyrotron components in the 1990s, significant progress has been achieved in the last decade, in particular, in the field of long-pulse and continuous wave (CW) gyrotrons for a wide range of frequencies. At present, the development of 1 MW-class CW gyrotrons has been very successful; these are applicable for self-ignition experiments on fusion plasmas and their confinement in the tokamak ITER, for long-pulse confinement experiments in the stellarator Wendelstein 7-X (W7-X) and for EC H&CD in the future tokamak JT-60SA. For this progress in the field of high-power long-pulse gyrotrons, innovations such as the realization of high-efficiency stable oscillation in very high order cavity modes, the use of single-stage depressed collectors for energy recovery, highly efficient internal quasi-optical mode converters and synthetic diamond windows have essentially contributed. The total tube efficiencies are around 50% and the purity of the fundamental Gaussian output mode is 97% and higher. In addition, activities for advanced gyrotrons, e.g. a 2 MW gyrotron using a coaxial cavity, multi-frequency 1 MW gyrotrons and power modulation technology, have made progress.

  16. Recent result of gyrotron operation in NIFS

    NASA Astrophysics Data System (ADS)

    Ito, Satoshi; Shimozuma, Takashi; Yoshimura, Yasuo; Igami, Hiroe; Takahashi, Hiromi; Nishiura, Masaki; Kobayashi, Sakuji; Mizuno, Yoshinori; Okada, Kota; Kubo, Shin

    2015-03-01

    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).

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

    NASA Astrophysics Data System (ADS)

    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.

  18. Development of gyrotrons for fusion with power exceeding 1 MW over a wide frequency range

    NASA Astrophysics Data System (ADS)

    Kariya, T.; Imai, T.; Minami, R.; Numakura, T.; Eguchi, T.; Kato, T.; Endo, Y.; Ichimura, M.; Shimozuma, T.; Kubo, S.; Takahashi, H.; Yoshimura, Y.; Igami, H.; Ito, S.; Mutoh, T.; Sakamoto, K.; Idei, H.; Zushi, H.; Nagasaki, K.; Sano, F.; Ono, M.; Mitsunaka, Y.

    2015-09-01

    Megawatt-class gyrotrons covering a wide frequency range (14 GHz-300 GHz) are in increasing demand for nuclear fusion. Recent electron cyclotron heating and electron cyclotron current drive experiments highlight a requirement of megawatt-scale gyrotrons at a relatively lower frequency (14-35 GHz) range of some plasma devices, like GAMMA 10/PDX of the University of Tsukuba, QUEST of Kyushu University, NSTX-U of Princeton Plasma Physics Laboratory, and Heliotron J of Kyoto University. Collaborative studies for designing a new 28 GHz/35 GHz dual-frequency gyrotron and a 14 GHz gyrotron have commenced. Operation above 1 MW of 28 GHz/35 GHz dual oscillation was demonstrated experimentally. Further in the design of dual-frequency gyrotron, operations with 2 MW 3 s and 0.4 MW CW (continuous wave) at 28 GHz, and power exceeding 1 MW for 3 s at 34.8 GHz have been shown to be feasible. The 14 GHz gyrotron is expected to operate above 1 MW. We are also developing higher frequency gyrotrons (77-300 GHz). The joint program of National Institute for Fusion Science and the University of Tsukuba developed two new 154 GHz gyrotrons for the large helical device after the demonstration of three 77 GHz gyrotrons. The 154 GHz gyrotrons achieved a maximum output power of 1.25 MW and quasi-CW operation of 0.35 MW for 30 min.

  19. Photonic-Band-Gap Traveling-Wave Gyrotron Amplifier

    PubMed Central

    Nanni, E. A.; Lewis, S. M.; Shapiro, M. A.; Griffin, R. G.; Temkin, R. J.

    2014-01-01

    We report the experimental demonstration of a gyrotron traveling-wave-tube amplifier at 250 GHz that uses a photonic band gap (PBG) interaction circuit. The gyrotron amplifier achieved a peak small signal gain of 38 dB and 45 W output power at 247.7 GHz with an instantaneous −3 dB bandwidth of 0.4 GHz. The amplifier can be tuned for operation from 245–256 GHz. The widest instantaneous −3 dB bandwidth of 4.5 GHz centered at 253.25 GHz was observed with a gain of 24 dB. The PBG circuit provides stability from oscillations by supporting the propagation of transverse electric (TE) modes in a narrow range of frequencies, allowing for the confinement of the operating TE03-like mode while rejecting the excitation of oscillations at nearby frequencies. This experiment achieved the highest frequency of operation for a gyrotron amplifier; at present, there are no other amplifiers in this frequency range that are capable of producing either high gain or high output power. This result represents the highest gain observed above 94 GHz and the highest output power achieved above 140 GHz by any conventional-voltage vacuum electron device based amplifier. PMID:24476286

  20. Photonic-band-gap traveling-wave gyrotron amplifier.

    PubMed

    Nanni, E A; Lewis, S M; Shapiro, M A; Griffin, R G; Temkin, R J

    2013-12-01

    We report the experimental demonstration of a gyrotron traveling-wave-tube amplifier at 250 GHz that uses a photonic band gap (PBG) interaction circuit. The gyrotron amplifier achieved a peak small signal gain of 38 dB and 45 W output power at 247.7 GHz with an instantaneous -3  dB bandwidth of 0.4 GHz. The amplifier can be tuned for operation from 245-256 GHz. The widest instantaneous -3  dB bandwidth of 4.5 GHz centered at 253.25 GHz was observed with a gain of 24 dB. The PBG circuit provides stability from oscillations by supporting the propagation of transverse electric (TE) modes in a narrow range of frequencies, allowing for the confinement of the operating TE03-like mode while rejecting the excitation of oscillations at nearby frequencies. This experiment achieved the highest frequency of operation for a gyrotron amplifier; at present, there are no other amplifiers in this frequency range that are capable of producing either high gain or high output power. This result represents the highest gain observed above 94 GHz and the highest output power achieved above 140 GHz by any conventional-voltage vacuum electron device based amplifier. PMID:24476286

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

    NASA Astrophysics Data System (ADS)

    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.

  2. Terahertz Gyrotrons at IAP RAS: Status and New Designs

    NASA Astrophysics Data System (ADS)

    Bratman, V. L.; Glyavin, M. Yu.; Kalynov, Yu. K.; Litvak, A. G.; Luchinin, A. G.; Savilov, A. V.; Zapevalov, V. E.

    2011-03-01

    Powerful gyrotrons with radiation frequencies in the range 0.33-0.65 THz were demonstrated at the IAP as early as in the 1970-1980s. This trend has recently been renewed in connection with a significant increase in interest in terahertz frequency range. In the course of new experiments, the radiation frequency of pulsed gyrotrons was increased up to 1.3 THz and 1 THz at the fundamental and third cyclotron harmonics, respectively. In addition, gyrotrons operated in CW regime with a frequency of 0.3 THz for technological applications (in collaboration with the University of Fukui, Japan) and 0.26 THz for the dynamic nuclear polarization at a high-field NMR were implemented. Designs of a pulsed fundamental-harmonic gyrotron with MW-level power at 0.3 THz and a CW kW-level third-harmonic gyrotron with a frequency of 0.4 THz are currently developed. Estimates show that modern techniques for the creation of strong magnetic fields now make it possible to realize gyrotrons with an operating frequency at least up to 1-1.5 THz. Such generators utilize a relatively low particle energy and can provide higher average power than the existing FELs.

  3. The reflex gyrotron

    NASA Astrophysics Data System (ADS)

    Goldenberg, A. L.; Savilov, A. V.; Yulpatov, V. K.

    2012-02-01

    A typical problem of low-power short-wavelength gyrotrons is that a too long cavity is required to provide the start of rf oscillations. Therefore, it is attractive to realize a gyrotron with a long enough operating region but relatively low diffraction Q-factor of the operating cavity. In this work, we propose a gyrotron with reflecting of electrons back to the operating cavity. Such a scheme provides significant decrease of the starting current and considerable efficiency enhancement.

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

    SciTech Connect

    Jory, H.; Felch, K.; Hess, C.; Huey, H.; Jongewaard, E.; Neilson, J.; Pendleton, R.; Tsirulnikov, M. )

    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.

  5. Low-voltage gyrotrons

    SciTech Connect

    Glyavin, M. Yu.; Zavolskiy, N. A.; Sedov, A. S.; Nusinovich, G. S.

    2013-03-15

    For a long time, the gyrotrons were primarily developed for electron cyclotron heating and current drive of plasmas in controlled fusion reactors where a multi-megawatt, quasi-continuous millimeter-wave power is required. In addition to this important application, there are other applications (and their number increases with time) which do not require a very high power level, but such issues as the ability to operate at low voltages and have compact devices are very important. For example, gyrotrons are of interest for a dynamic nuclear polarization, which improves the sensitivity of the nuclear magnetic resonance spectroscopy. In this paper, some issues important for operation of gyrotrons driven by low-voltage electron beams are analyzed. An emphasis is made on the efficiency of low-voltage gyrotron operation at the fundamental and higher cyclotron harmonics. These efficiencies calculated with the account for ohmic losses were, first, determined in the framework of the generalized gyrotron theory based on the cold-cavity approximation. Then, more accurate, self-consistent calculations for the fundamental and second harmonic low-voltage sub-THz gyrotron designs were carried out. Results of these calculations are presented and discussed. It is shown that operation of the fundamental and second harmonic gyrotrons with noticeable efficiencies is possible even at voltages as low as 5-10 kV. Even the third harmonic gyrotrons can operate at voltages about 15 kV, albeit with rather low efficiency (1%-2% in the submillimeter wavelength region).

  6. Low-voltage gyrotrons

    NASA Astrophysics Data System (ADS)

    Glyavin, M. Yu.; Zavolskiy, N. A.; Sedov, A. S.; Nusinovich, G. S.

    2013-03-01

    For a long time, the gyrotrons were primarily developed for electron cyclotron heating and current drive of plasmas in controlled fusion reactors where a multi-megawatt, quasi-continuous millimeter-wave power is required. In addition to this important application, there are other applications (and their number increases with time) which do not require a very high power level, but such issues as the ability to operate at low voltages and have compact devices are very important. For example, gyrotrons are of interest for a dynamic nuclear polarization, which improves the sensitivity of the nuclear magnetic resonance spectroscopy. In this paper, some issues important for operation of gyrotrons driven by low-voltage electron beams are analyzed. An emphasis is made on the efficiency of low-voltage gyrotron operation at the fundamental and higher cyclotron harmonics. These efficiencies calculated with the account for ohmic losses were, first, determined in the framework of the generalized gyrotron theory based on the cold-cavity approximation. Then, more accurate, self-consistent calculations for the fundamental and second harmonic low-voltage sub-THz gyrotron designs were carried out. Results of these calculations are presented and discussed. It is shown that operation of the fundamental and second harmonic gyrotrons with noticeable efficiencies is possible even at voltages as low as 5-10 kV. Even the third harmonic gyrotrons can operate at voltages about 15 kV, albeit with rather low efficiency (1%-2% in the submillimeter wavelength region).

  7. Self-adjusting anode power supply for a gyrotron

    SciTech Connect

    Brand, G.F.; Fekete, P.W.; Hong, K. ); Idehara, T.; Tatsukawa, T. )

    1991-02-01

    Sydney University's tunable cw gyrotrons use a simplified power supply arrangement to provide the voltages on the gun electrodes. The cathode supply is conventional, but the anode voltage is provided by a single high-value resistor connected between the anode and ground. A small fraction of the electrons in the beam are reflected and the anode automatically finds an optimum operating potential. This arrangement is shown to have lower starting currents. Two advantages follow. It becomes easier to operate low-power gyrotrons with modest power supplies and it becomes easier to achieve higher frequencies by exciting harmonics of the electron cyclotron frequency.

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

    SciTech Connect

    Thumm, M.; Alberti, S.; Hogge, J.-P.; Tran, M. Q.; Yovchev, I.; Arnold, A.; Bariou, D.; Giguet, E.; Lievin, C.; Dammertz, G.; Illy, S.; Jin, J.; Piosczyk, B.; Prinz, O.; Rzesnicki, T.; Yang, X.; Darbos, C.; Magne, R.; Gantenbein, G.

    2006-01-03

    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.

  9. Integrated Design of Undepressed Collector for Low Power Gyrotron

    NASA Astrophysics Data System (ADS)

    Kumar, Anil; Goswami, Uttam K.; Poonia, Sunita; Singh, Udaybir; Kumar, Nitin; Alaria, M. K.; Bera, A.; Khatun, Hasina; Sinha, A. K.

    2011-06-01

    A 42 GHz, 200 kW continuous wave (CW) gyrotron, operating at TE03 mode is under development for the electron cyclotron resonance plasma heating of the Indian TOKAMAK system. The gyrotron is made up of an undepressed collector. The undepressed collector is simple to design and cost effective. In this paper, a detailed design study of the undepressed collector for the 42 GHz gyrotron is presented. The EGUN code is used to analyze the spent electron beam trajectory for the maximum spread to reduce the power loading on the collector surface. To achieve wall loading ≤1 kW/cm2, a collector with a length of 800 mm and a radius of 42.5 mm is designed. The design also includes the three magnet systems around the collector for maximum and uniform beam spread. The thermal and the structural analyses are done using the ANSYS code to optimize the collector structure and dimensions with tolerance.

  10. 47 CFR 15.256 - Operation of level probing radars within the bands 5.925-7.250 GHz, 24.05-29.00 GHz, and 75-85 GHz.

    Code of Federal Regulations, 2014 CFR

    2014-10-01

    ... 47 Telecommunication 1 2014-10-01 2014-10-01 false Operation of level probing radars within the bands 5.925-7.250 GHz, 24.05-29.00 GHz, and 75-85 GHz. 15.256 Section 15.256 Telecommunication FEDERAL COMMUNICATIONS COMMISSION GENERAL RADIO FREQUENCY DEVICES Intentional Radiators Radiated Emission Limits, Additional Provisions § 15.256 Operation...

  11. Progress on Gyrotrons for ITER and Future Fusion Reactors

    NASA Astrophysics Data System (ADS)

    Thumm, Manfred K.

    2009-11-01

    The prototype of the Japan 170 GHz ITER gyrotron holds the energy and efficiency world record of 2.88 GJ (0.8 MW, 3600 s, 57%) with 55% efficiency at 1 MW, 800 s, whereas the Russian 170 GHz ITER prototype tube achieved 0.83 MW with a pulse duration of 203 s at 48% efficiency and 1 MW at 116 s and 52%. The record parameters of the European megawatt-class 140 GHz gyrotron for the Stellarator Wendelstein W7-X are: 0.92 MW output power at 1800 s pulse duration, almost 45% efficiency and 97.5% Gaussian mode purity. All these gyrotrons employ a cylindrical cavity, a quasi-optical output coupler, a synthetic diamond window and a single-stage depressed collector (SDC) for energy recovery. In coaxial cavities the existence of the longitudinally corrugated inner conductor reduces the problems of mode competition and limiting current, thus allowing one to use even higher order modes with lower Ohmic attenuation than in cylindrical cavities. Synthetic diamond windows with a transmission capability of 2 MW, continuous wave (CW) are feasible. In order to keep the number of the required gyrotrons and magnets as low as possible, to reduce the costs of the ITER 26 MW, 170 GHz ECRH system and to allow compact upper launchers for plasma stabilization, 2 MW mm-wave power per gyrotron tube is desirable. The FZK pre-prototype tube for an EU 170 GHz, 2 MW ITER gyrotron has achieved 1.8 MW at 28% efficiency (without depressed collector). Design studies for a 4 MW 170 GHz coaxial-cavity gyrotron with two synthetic diamond output windows and two 2 MW mm-wave output beams for future fusion reactors are currently being performed at FZK. The availability of sources with fast frequency tunability (several GHz s-1, tuning in 1.5-2.5% steps for about ten different frequencies) would permit the use of a simple, fixed, non-steerable mirror antenna for local current drive (ECCD) experiments and plasma stabilization. GYCOM in Russia develops in collaboration with IPP Garching and FZK an industrial

  12. Progress on Gyrotrons for ITER and Future Fusion Reactors

    SciTech Connect

    Thumm, Manfred K.

    2009-11-26

    The prototype of the Japan 170 GHz ITER gyrotron holds the energy and efficiency world record of 2.88 GJ (0.8 MW, 3600 s, 57%) with 55% efficiency at 1 MW, 800 s, whereas the Russian 170 GHz ITER prototype tube achieved 0.83 MW with a pulse duration of 203 s at 48% efficiency and 1 MW at 116 s and 52%. The record parameters of the European megawatt-class 140 GHz gyrotron for the Stellarator Wendelstein W7-X are: 0.92 MW output power at 1800 s pulse duration, almost 45% efficiency and 97.5% Gaussian mode purity. All these gyrotrons employ a cylindrical cavity, a quasi-optical output coupler, a synthetic diamond window and a single-stage depressed collector (SDC) for energy recovery. In coaxial cavities the existence of the longitudinally corrugated inner conductor reduces the problems of mode competition and limiting current, thus allowing one to use even higher order modes with lower Ohmic attenuation than in cylindrical cavities. Synthetic diamond windows with a transmission capability of 2 MW, continuous wave (CW) are feasible. In order to keep the number of the required gyrotrons and magnets as low as possible, to reduce the costs of the ITER 26 MW, 170 GHz ECRH system and to allow compact upper launchers for plasma stabilization, 2 MW mm-wave power per gyrotron tube is desirable. The FZK pre-prototype tube for an EU 170 GHz, 2 MW ITER gyrotron has achieved 1.8 MW at 28% efficiency (without depressed collector). Design studies for a 4 MW 170 GHz coaxial-cavity gyrotron with two synthetic diamond output windows and two 2 MW mm-wave output beams for future fusion reactors are currently being performed at FZK. The availability of sources with fast frequency tunability (several GHz s{sup -1}, tuning in 1.5-2.5% steps for about ten different frequencies) would permit the use of a simple, fixed, non-steerable mirror antenna for local current drive (ECCD) experiments and plasma stabilization. GYCOM in Russia develops in collaboration with IPP Garching and FZK an

  13. Experimental tests of a 263 GHz gyrotron for spectroscopic applications and diagnostics of various media

    SciTech Connect

    Glyavin, M. Yu. Denisov, G. G.; Zapevalov, V. E.; Chirkov, A. V.; Fokin, A. P.; Kholoptsev, V. V.; Kuftin, A. N.; Luchinin, A. G.; Golubyatnikov, G. Yu.; Malygin, V. I.; Morozkin, M. V.; Manuilov, V. N.; Proyavin, M. D.; Sedov, A. S.; Tsvetkov, A. I.; Sokolov, E. V.; Tai, E. M.

    2015-05-15

    A 263 GHz continuous-wave (CW) gyrotron was developed at the IAP RAS for future applications as a microwave power source in Dynamic Nuclear Polarization / Nuclear magnetic resonance (DNP/NMR) spectrometers. A new experimental facility with a computerized control was built to test this and subsequent gyrotrons. We obtained the maximum CW power up to 1 kW in the 15 kV/0.4 A operation regime. The power about 10 W, which is sufficient for many spectroscopic applications, was realized in the low current 14 kV/0.02 A regime. The possibility of frequency tuning by variation of the coolant temperature about 4 MHz/1 °C was demonstrated. The spectral width of the gyrotron radiation was about 10{sup −6}.

  14. Experimental tests of a 263 GHz gyrotron for spectroscopic applications and diagnostics of various media.

    PubMed

    Glyavin, M Yu; Chirkov, A V; Denisov, G G; Fokin, A P; Kholoptsev, V V; Kuftin, A N; Luchinin, A G; Golubyatnikov, G Yu; Malygin, V I; Morozkin, M V; Manuilov, V N; Proyavin, M D; Sedov, A S; Sokolov, E V; Tai, E M; Tsvetkov, A I; Zapevalov, V E

    2015-05-01

    A 263 GHz continuous-wave (CW) gyrotron was developed at the IAP RAS for future applications as a microwave power source in Dynamic Nuclear Polarization / Nuclear magnetic resonance (DNP/NMR) spectrometers. A new experimental facility with a computerized control was built to test this and subsequent gyrotrons. We obtained the maximum CW power up to 1 kW in the 15 kV/0.4 A operation regime. The power about 10 W, which is sufficient for many spectroscopic applications, was realized in the low current 14 kV/0.02 A regime. The possibility of frequency tuning by variation of the coolant temperature about 4 MHz/1 °C was demonstrated. The spectral width of the gyrotron radiation was about 10(-6). PMID:26026544

  15. Experimental tests of a 263 GHz gyrotron for spectroscopic applications and diagnostics of various media

    NASA Astrophysics Data System (ADS)

    Glyavin, M. Yu.; Chirkov, A. V.; Denisov, G. G.; Fokin, A. P.; Kholoptsev, V. V.; Kuftin, A. N.; Luchinin, A. G.; Golubyatnikov, G. Yu.; Malygin, V. I.; Morozkin, M. V.; Manuilov, V. N.; Proyavin, M. D.; Sedov, A. S.; Sokolov, E. V.; Tai, E. M.; Tsvetkov, A. I.; Zapevalov, V. E.

    2015-05-01

    A 263 GHz continuous-wave (CW) gyrotron was developed at the IAP RAS for future applications as a microwave power source in Dynamic Nuclear Polarization / Nuclear magnetic resonance (DNP/NMR) spectrometers. A new experimental facility with a computerized control was built to test this and subsequent gyrotrons. We obtained the maximum CW power up to 1 kW in the 15 kV/0.4 A operation regime. The power about 10 W, which is sufficient for many spectroscopic applications, was realized in the low current 14 kV/0.02 A regime. The possibility of frequency tuning by variation of the coolant temperature about 4 MHz/1 °C was demonstrated. The spectral width of the gyrotron radiation was about 10-6.

  16. The multi-mode gyrotron

    SciTech Connect

    Savilov, A. V.; Glyavin, M. Yu.; Philippov, V. N.

    2011-10-15

    It is possible to provide a situation in the gyrotron when it possesses a dense spectrum of axial eigenmodes having different frequencies but almost similar Q-factors. In this case, the single-frequency operation of the gyrotron is provided due to non-linear competition of the eigenmodes. It is shown that such an approach opens a way to provide in gyrotrons a close-to-continuous frequency tuning.

  17. Initial Testing of a 140 GHz 1 MW Gyrotron

    NASA Astrophysics Data System (ADS)

    Cauffman, Stephen; Felch, Kevin; Blank, Monica; Borchard, Philipp; Cahalan, Pat; Chu, Sam; Jory, Howard

    2001-10-01

    CPI has completed the fabrication of a 140 GHz 1 MW CW gyrotron to be used on the W7-X stellarator at IPP Greifswald. Testing of the initial build of this gyrotron had just begun when this abstract was prepared, and was expected to finish in September, at which time a planned rebuild of the device was scheduled to begin. This poster will summarize the gyrotron design, present results of initial testing, and outline any design changes planned as a consequence of these results. This gyrotron's design employs a number of advanced features, including a diode electron gun for simplified operation, a single-stage depressed collector to enhance overall efficiency, a CVD diamond output window, an internal mode converter that converts the excited TE28,7 cavity mode to a Gaussian output beam, and a high-voltage layout that locates all external high voltage below the superconducting magnet system without requiring an oil tank for insulation. Similar features are being used for an 84 GHz 500 kW system being built for the KSTAR tokamak program and for a 110 GHz 1.5 MW system being designed in collaboration with MIT, UMd, UW, GA, and Calabazas Creek Research with funding provided by DOE.

  18. 28 GHz Gyrotron ECRH Upgrade for LDX

    NASA Astrophysics Data System (ADS)

    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 < 5 m straight waveguide run. A Vlasov launch antenna in LDX will direct the beam to the upper 1 Tesla resonance region. A layout of the planned system will be presented.

  19. 28 GHz Gyrotron ECRH on LDX

    NASA Astrophysics Data System (ADS)

    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.

  20. Operation of a step tunable megawatt gyrotron

    NASA Technical Reports Server (NTRS)

    Kreischer, K. E.; Temkin, R. J.

    1989-01-01

    An electron cyclotron resonance maser; gyrotron fundamental oscillator; advantages of gyrotrons; a schematic of the experiment; gyrotron design theory; 1 MW design parameters; compact ignition tokamak; and a gyrotron with quasi-optical output coupler are briefly presented. This presentation is represented by viewgraphs only.

  1. Megawatt, 1kHz PRF tunable gyrotron experiments

    SciTech Connect

    Cross, A.W.; Phelps, A.D.R.; Ronald, K.; Spark, S.N.; Turnbull, S.M.

    1995-12-31

    Repetitively pulsed and cw gyrotrons have hitherto used thermionic cathodes whereas cold cathode gyrotrons have normally operated as {open_quote} single shot{close_quote} or low pulse repetition frequency (PRF) devices. The novel results presented here demonstrate that a stacked Blumlein pulse generator driven cold cathode gyrotron developing > 1 MW per pulse (f=90 GHz) may be run with a repetition frequency of 1 kHz over timescales of >30 seconds. A short burst PRF of 2 kHz was also observed. The PRF of the system was limited to 2 kHz by the High Voltage (HV) DC power supply. The gyrotron was based on a two-electrode configuration comprising of a field-immersed, field emission cold cathode and a shaped anode cavity. A superconducting magnet was used to produce the homogeneous intra-cavity magnetic field and a stacked Blumlein pulse generator was used to drive the electron beam. This pulse generator was capable of producing an output voltage up to 300 kV with a 20ns rise time, a 100ns flat top, and a 20ns fall time. The output impedance was 200{Omega} and the energy stored in the generator at a charging voltage of 60 kV was 5.4J. No degradation effects on the mm-wave output was evident due to diode recovery time throughout this series of results. A subsequent conclusion is that the recovery time in the cold cathode gyrotron is less than 500{mu}s.

  2. First experiments with gasdynamic ion source in CW mode.

    PubMed

    Skalyga, V; Izotov, I; Golubev, S; Vodopyanov, A; Tarvainen, O

    2016-02-01

    A new type of ECR ion source-a gasdynamic ECR ion source-has been recently developed at the Institute of Applied Physics. The main advantages of such device are extremely high ion beam current with a current density up to 600-700 emA/cm(2) in combination with low emittance, i.e., normalized RMS emittance below 0.1 π mm mrad. Previous investigations were carried out in pulsed operation with 37.5 or 75 GHz gyrotron radiation with power up to 100 kW at SMIS 37 experimental facility. The present work demonstrates the first experience of operating the gasdynamic ECR ion source in CW mode. A test bench of SMIS 24 facility has been developed at IAP RAS. 24 GHz radiation of CW gyrotron was used for plasma heating in a magnetic trap with simple mirror configuration. Initial studies of plasma parameters were performed. Ion beams with pulsed and CW high voltage were successfully extracted from the CW discharge. Obtained experimental results demonstrate that all advantages of the gasdynamic source can be realized also in CW operation. PMID:26931933

  3. First experiments with gasdynamic ion source in CW mode

    NASA Astrophysics Data System (ADS)

    Skalyga, V.; Izotov, I.; Golubev, S.; Vodopyanov, A.; Tarvainen, O.

    2016-02-01

    A new type of ECR ion source—a gasdynamic ECR ion source—has been recently developed at the Institute of Applied Physics. The main advantages of such device are extremely high ion beam current with a current density up to 600-700 emA/cm2 in combination with low emittance, i.e., normalized RMS emittance below 0.1 π mm mrad. Previous investigations were carried out in pulsed operation with 37.5 or 75 GHz gyrotron radiation with power up to 100 kW at SMIS 37 experimental facility. The present work demonstrates the first experience of operating the gasdynamic ECR ion source in CW mode. A test bench of SMIS 24 facility has been developed at IAP RAS. 24 GHz radiation of CW gyrotron was used for plasma heating in a magnetic trap with simple mirror configuration. Initial studies of plasma parameters were performed. Ion beams with pulsed and CW high voltage were successfully extracted from the CW discharge. Obtained experimental results demonstrate that all advantages of the gasdynamic source can be realized also in CW operation.

  4. Development and Applications of High—Frequency Gyrotrons in FIR FU Covering the sub-THz to THz Range

    NASA Astrophysics Data System (ADS)

    Idehara, Toshitaka; Sabchevski, Svilen Petrov

    2012-07-01

    Powerful sources of coherent radiation in the sub-terahertz and in the terahertz frequency range of the electromagnetic spectrum are necessary for a great and continuously expanding number of applications in the physical research and in various advanced technological processes as well as in radars, communication systems, for remote sensing and inspection etc.. In recent years, a spectacular progress in the development of various gyro-devices and in particular of the powerful high frequency (sub-terahertz and terahertz) gyrotron oscillators has demonstrated a remarkable potential for bridging the so-called terahertz power gap and stimulated many novel and prospective applications. In this review paper we outline two series of such devices, namely the Gyrotron FU Series which includes pulsed gyrotrons and Gyrotron FU CW Series which consist of tubes operated in a CW (continuous wave) or long pulse mode, both developed at the FIR FU Center. We present the most remarkable achievements of these devices and illustrate their applications by some characteristic examples. An outlook for the further extension of the Gyrotron FU CW Series is also provided.

  5. Gyrotron transmitting tube

    NASA Technical Reports Server (NTRS)

    Kosmahl, H. G. (Inventor)

    1983-01-01

    An RF transmitting tube for the 20 GHz to 500 GHz range comprises a gyrotron and a multistage depressed collector. A winding provides a magnetic field which acts on spent, spinning or orbiting electrons changing their motion to substantially forward linear motion in a downstream direction. The spent electrons then pass through a focusser into the collector. Nearly all of the electrons injected into the collector will remain within an imaginary envelope as they travel forward toward the end collector plate. The apertures in the collector plates are at least as large in diameter as the envelope at any particular axial position.

  6. High time resolution observations of the polar stratosphere and mesosphere using a ground-based 230-250 GHz microwave radiometer

    NASA Astrophysics Data System (ADS)

    Newnham, D. A.; Espy, P. J.; Clilverd, M. A.; Maxfield, D. J.; Hartogh, P.; Holmén, K.; Blindheim, S.; Horne, R. B.

    2012-04-01

    Microwave radiometry is used to measure thermal emission by the Doppler- and pressure-broadened molecular rotational lines of atmospheric gases, from which vertical abundance profiles can be determined. Since solar radiation is not required for the measurement, the technique has the advantage that continuous observations are possible including throughout the polar winter. We describe the development of a passive microwave radiometer [Espy, P. J., P. Hartogh, and K. Holmen (2006), Proc. SPIE, 6362, 63620P, doi:10.1117/12.688953] for ground-based remote sensing of the polar middle atmosphere. The instrument measures nitric oxide (NO), ozone (O3), and carbon monoxide (CO) vertical profiles over the altitude range 35-90 km with time resolution as high as 15 minutes, allowing the diurnal variability of trace chemical species to be investigated. Heterodyne detection of atmospheric emission at 230 GHz and 250 GHz (wavelength ~1.25 mm) with a receiver noise temperature of 300 K is achieved using a superconductor-insulator-superconductor (SIS) mixer cooled to 4 K. The down-converted signals at 1.35 GHz and 2.10 GHz are analysed using both a moderate-resolution (28 kHz, 220 MHz bandwidth) and a high-resolution (14 kHz, 40 MHz bandwidth) chirp-transform spectrometer (CTS). The instrument was operated semi-autonomously at Troll station (72° 01'S 02° 32'E, 1270 m above sea level), Antarctica during 2008-10 and at the Arctic LIDAR Observatory for Middle Atmosphere Research (ALOMAR, 69° 16'N, 16° 00'E, 380 m above sea level), northern Norway during 2011-12. NO volume mixing ratio (VMR) profiles have been inverted from calibrated brightness temperature spectra of the NO line centred at 250.796 GHz, observed above Troll station, using the Microwave Observation Line Estimation and Retrieval (MOLIERE) version 5 code. A priori pressure, temperature, ozone, water vapour, and NO profiles above 30 km were calculated using the Sodankylä Ion and Neutral Chemistry (SIC, version 6

  7. Gyrotron: an ECH system component

    SciTech Connect

    Loring, C.M.; Eason, H.O.; Kimrey, H.D.; White, T.L.; Jory, H.R.; Evans, S.J.

    1981-01-01

    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.

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

    NASA Astrophysics Data System (ADS)

    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

  9. Continuous-Wave Operation of a 460-GHz Second Harmonic Gyrotron Oscillator.

    PubMed

    Hornstein, Melissa K; Bajaj, Vikram S; Griffin, Robert G; Temkin, Richard J

    2006-06-01

    We report the regulated continuous-wave (CW) operation of a second harmonic gyrotron oscillator at output power levels of over 8 W (12.4 kV and 135 mA beam voltage and current) in the TE(0,6,1) mode near 460 GHz. The gyrotron also operates in the second harmonic TE(2,6,1) mode at 456 GHz and in the TE(2,3,1) fundamental mode at 233 GHz. CW operation was demonstrated for a one-hour period in the TE(0,6,1) mode with better than 1% power stability, where the power was regulated using feedback control. Nonlinear simulations of the gyrotron operation agree with the experimentally measured output power and radio-frequency (RF) efficiency when cavity ohmic losses are included in the analysis. The output radiation pattern was measured using a pyroelectric camera and is highly Gaussian, with an ellipticity of 4%. The 460-GHz gyrotron will serve as a millimeter-wave source for sensitivity-enhanced nuclear magnetic resonance (dynamic nuclear polarization) experiments at a magnetic field of 16.4 T. PMID:17710187

  10. Continuous-Wave Operation of a 460-GHz Second Harmonic Gyrotron Oscillator

    PubMed Central

    Hornstein, Melissa K.; Bajaj, Vikram S.; Griffin, Robert G.; Temkin, Richard J.

    2007-01-01

    We report the regulated continuous-wave (CW) operation of a second harmonic gyrotron oscillator at output power levels of over 8 W (12.4 kV and 135 mA beam voltage and current) in the TE0,6,1 mode near 460 GHz. The gyrotron also operates in the second harmonic TE2,6,1 mode at 456 GHz and in the TE2,3,1 fundamental mode at 233 GHz. CW operation was demonstrated for a one-hour period in the TE0,6,1 mode with better than 1% power stability, where the power was regulated using feedback control. Nonlinear simulations of the gyrotron operation agree with the experimentally measured output power and radio-frequency (RF) efficiency when cavity ohmic losses are included in the analysis. The output radiation pattern was measured using a pyroelectric camera and is highly Gaussian, with an ellipticity of 4%. The 460-GHz gyrotron will serve as a millimeter-wave source for sensitivity-enhanced nuclear magnetic resonance (dynamic nuclear polarization) experiments at a magnetic field of 16.4 T. PMID:17710187

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

    NASA Astrophysics Data System (ADS)

    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.

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

    SciTech Connect

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

    1985-01-01

    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 TE031 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.

  13. Nonstationary oscillations in gyrotrons revisited

    SciTech Connect

    Dumbrajs, O.; Kalis, H.

    2015-05-15

    Development of gyrotrons requires careful understanding of different regimes of gyrotron oscillations. It is known that in the planes of the generalized gyrotron variables: cyclotron resonance mismatch and dimensionless current or cyclotron resonance mismatch and dimensionless interaction length complicated alternating sequences of regions of stationary, periodic, automodulation, and chaotic oscillations exist. In the past, these regions were investigated on the supposition that the transit time of electrons through the interaction space is much shorter than the cavity decay time. This assumption is valid for short and/or high diffraction quality resonators. However, in the case of long and/or low diffraction quality resonators, which are often utilized, this assumption is no longer valid. In such a case, a different mathematical formalism has to be used for studying nonstationary oscillations. One example of such a formalism is described in the present paper.

  14. Recent progress in developing a 170 GHz, 500 kW gyrotron for testing ITER transmission line components

    NASA Astrophysics Data System (ADS)

    Felch, Kevin; Blank, Monica; Borchard, Philipp; Cahalan, Pat; Cauffman, Steve

    2011-10-01

    A 170 GHz, 500 kW CW gyrotron has been developed for testing ITER transmission line components. Although specified as a 500 kW source, the electrical design has been conceived with the goal of generating up to 1 MW of continuous output power. The design employs a double-anode electron gun, an interaction cavity operating in the TE31,8 cavity mode, a three-mirror internal converter to produce a fundamental Gaussian output beam, a CVD diamond output window and a depressed collector to safely dissipate the spent electron beam power. Fabrication of the gyrotron is nearly complete and initial high-power tests will soon be carried out. Details of the gyrotron design, results of low-power tests on the internal converter and initial high-power tests will be presented.

  15. Hysteresis and Frequency Tunability of Gyrotrons

    NASA Astrophysics Data System (ADS)

    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.

  16. Effective Cavity Length of Gyrotrons

    NASA Astrophysics Data System (ADS)

    Thumm, Manfred

    2014-12-01

    Megawatt-class gyrotron oscillators for electron cyclotron heating and non-inductive current drive (ECH&CD) in magnetically confined thermonuclear fusion plasmas have relatively low cavity quality factors in the range of 1000 to 2000. The effective length of their cavities cannot be simply deduced from the cavity electric field profile, since this has by far not a Gaussian shape. The present paper presents a novel method to estimate the effective length of a gyrotron cavity just from the eigenvalue of the operating TEm,n mode, the cavity radius and the exact oscillation frequency which may be numerically computed or precisely measured. This effective cavity length then can be taken to calculate the Fresnel parameter in order to confirm that the cavity is not too short so that the transverse structure of any mode in the cavity is the same as that of the corresponding mode in a long circular waveguide with the same diameter.

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

    NASA Astrophysics Data System (ADS)

    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.

  18. Experimental results for a 1.5 MW, 110 GHz gyrotron oscillator with reduced mode competition

    SciTech Connect

    Choi, E.M.; Marchewka, C.D.; Mastovsky, I.; Sirigiri, J.R.; Shapiro, M.A.; Temkin, R.J.

    2006-02-15

    A new result from a 110 GHz gyrotron at MIT is reported with an output power of 1.67 MW and an efficiency of 42% when operated at 97 kV and 41 A for 3 {mu}s pulses in the TE{sub 22,6} mode. These results are a major improvement over results obtained with an earlier cavity design, which produced 1.43 MW of power at 37% efficiency. These new results were obtained using a cavity with a reduced output taper angle and a lower ohmic loss when compared with the earlier cavity. The improved operation is shown experimentally to be the result of reduced mode competition from the nearby TE{sub 19,7} mode. The reduced mode competition agrees well with an analysis of the startup scenario based on starting current simulations. The present results should prove useful in planning long pulse and CW versions of the 110 GHz gyrotron.

  19. Gyrotron development for space power beaming

    NASA Technical Reports Server (NTRS)

    Manheimer, Wallace M.

    1989-01-01

    The use of a gyrotron for space power beaming, especially in the form of a lunar orbiting power station is discussed. The advantages of phased array power beaming, output power, and the design of a quasi-optical gyrotron are discussed.

  20. Design of a 3-MW 140-GHz gyrotron with a coaxial cavity

    SciTech Connect

    Read, M.E.; Nusinovich, G.S.; Dumbrajs, O.; Bird, G.; Hogge, J.P.; Kreischer, K.; Blank, M.

    1996-06-01

    Gyrotrons have been developed as sources of high-power millimeter wave radiation for electron cyclotron heating for more than two decades, with orders of magnitude increases in power at frequencies to almost 300 GHz having been achieved. The requirement is for at least 1 MW, essentially CW at 110 GHz, for near-term applications such as plasma heating experiments, and greater than 1 MW CW for the next generation magnetic fusion device, the International Thermonuclear Experimental Reactor (ITER). For increased economy, multimegawatt devices are being considered. In this paper, a design for a 3-MW 140 GHz gyrotron based on the use of a coaxial cavity is given. The cavity mode is TE{sub 21,13}, chosen so that the ohmic heating on both the inner and outer conductors would be low enough for CW operation. The mode selection process, nonlinear, multimode and time-dependent modeling of the beam wave interaction, and gun design are discussed in detail. An inverted magnetron injection gun (MIG) is used to accommodate the inner conductor. The radiation is coupled out via a quasi-optical mode converter, consisting of an irregular cylindrical waveguide section followed by a step-cut launching aperture and a single near-parabolic mirror. The design of these components is also described.

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

    PubMed

    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

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

    PubMed

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

    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 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 magnetic field values is in good agreement with theoretical start currents obtained from linear theory for successive high-order axial modes TE11,2,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:23761938

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

    PubMed Central

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

    2011-01-01

    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 magnetic field values is in good agreement with theoretical start currents obtained from linear theory for successive high-order axial modes TE11,2,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

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

    PubMed Central

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

    2012-01-01

    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 magnetic field values is in good agreement with theoretical start currents obtained from linear theory for successive high-order axial modes TE11,2,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:23761938

  5. Mutual synchronization of weakly coupled gyrotrons

    SciTech Connect

    Rozental, R. M.; Glyavin, M. Yu.; Sergeev, A. S.; Zotova, I. V.; Ginzburg, N. S.

    2015-09-15

    The processes of synchronization of two weakly coupled gyrotrons are studied within the framework of non-stationary equations with non-fixed longitudinal field structure. With the allowance for a small difference of the free oscillation frequencies of the gyrotrons, we found a certain range of parameters where mutual synchronization is possible while a high electronic efficiency is remained. It is also shown that synchronization regimes can be realized even under random fluctuations of the parameters of the electron beams.

  6. Chaotic electron dynamics in gyrotron resonators

    SciTech Connect

    Kominis, Y.; Dumbrajs, O.; Avramides, K.A.; Hizanidis, K.; Vomvoridis, J.L.

    2005-04-15

    Phase space analysis of electron dynamics is used in combination with the canonical perturbation method and the KAM (Kolmogorov-Arnold-Moser) theory in order to study the dependence of the efficient gyrotron operation on the rf field profile and frequency mismatch. Knowledge of the boundaries of the electron motion provided through robust (slightly distorted) KAM surfaces is useful for optimizing depressed collectors and thereby for enhancement of overall efficiency of gyrotron operation.

  7. Resonant Cavities for Frequency Tunable Gyrotrons

    NASA Astrophysics Data System (ADS)

    Sabchevski, S.; Idehara, T.

    2008-01-01

    In this paper we present, discuss and compare several concepts based on both well-known and novel ideas for tunable gyrotron cavities. Although theoretical and design considerations are presented and discussed together the main focus is on the underlying principles and feasibility of different approaches rather than on their specific implementations. Illustrative examples are provided for configurations and frequency range appropriate for gyrotrons used as radiation sources for NMR spectroscopy with signal enhancement through DNP.

  8. Experimental study of a megawatt 200--300 GHz gyrotron oscillator

    SciTech Connect

    Grimm, T.L.; Kreischer, K.E.; Temkin, R.J. )

    1993-11-01

    A detailed experimental study is presented of a pulsed megawatt gyrotron oscillator operating in the 200--300 GHz range, whose design is consistent with continuous operation for electron cyclotron resonance heating (ECRH) of fusion plasmas. Two different radii beams produced by magnetron injection guns (MIG's) were used to excite the cylindrical waveguide cavity. The emission was found experimentally to be single mode, single frequency with a single rotation, which can be mode converted for transmission. The highest power reached with the larger radius electron beam was 1.2 MW at 230 GHz in the TE[sub 34,6] mode with an efficiency of 20% and beam parameters of 59 A and 100 kV. The highest power reached with the smaller radius electron beam was 0.78 MW at 280 GHz in the TE[sub 25,13] mode with an efficiency of 17% and beam parameters of 51 A and 92 kV. The smaller radius beam gave a peak efficiency of 18% at 0.72 MW, 290 GHz in the TE[sub 25,14] mode. Efficiencies obtained in this experiment are about half that of less highly overmoded gyrotrons. Analysis of the experiment suggests that the low efficiency is primarily caused by azimuthal mode competition, in agreement with multimode theory for a tapered cavity. These experimental results show that megawatt power levels can be generated in continuous wave (cw) gyrotron oscillators at 200--300 GHz with efficiencies approaching 20%.

  9. The Gyrotron at 50: Historical Overview

    NASA Astrophysics Data System (ADS)

    Nusinovich, Gregory S.; Thumm, Manfred K. A.; Petelin, Michael I.

    2014-04-01

    Gyrotrons form a specific group of devices in the class of fast-wave vacuum electronic sources of coherent electromagnetic wave radiation known as electron cyclotron masers (ECMs) or cyclotron resonance masers (CRMs). The operation of CRMs is based on the cyclotron maser instability which originates from the relativistic dependence of the electron cyclotron frequency on the electron energy. This relativistic effect can be pronounced even at low voltages when the electron kinetic energy is small in comparison with the rest energy. The free energy for generation of electromagnetic (EM) waves is the energy of electron gyration in an external magnetic field. As in any fast-wave device, the EM field in a gyrotron interaction space is not localized near a circuit wall (like in slow-wave devices), but can occupy large volumes. Due to possibilities of using various methods of mode selection (electrodynamical and electronic ones), gyrotrons can operate in very high order modes. Since the use of large, oversized cavities and waveguides reduces the role of ohmic wall losses and breakdown limitations, gyrotrons are capable of producing very high power radiation at millimeter and submillimeter wavelengths. The present review is restricted primarily by the description of the development and the present state-of-the-art of gyrotrons for controlled thermonuclear fusion plasma applications. The first gyrotron was invented, designed and tested in Gorky, USSR (now Nizhny Novgorod, Russia), in 1964.

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

    NASA Astrophysics Data System (ADS)

    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.

  11. Experimental investigation of a coaxial gyrotron oscillator

    NASA Astrophysics Data System (ADS)

    Advani, Rahul N.

    1999-09-01

    This thesis presents experimental results of a megawatt power level, 140 GHz coaxial gyrotron oscillator. The coaxial gyrotron has the potential to transport very high power electron beams and thus achieve higher microwave output power levels than conventional gyrotrons. A TE21,13 coaxial gyrotron was designed to operate at 95 kV, 76 A. This tube was tested to high power with the first high power Inverted Magnetron Injection Gun (IMIG). The IMIG electron gun was tested to 10 MW (105 kV, 93 A), which is the highest power level for a non-relativistic gyrotron gun. Operation of the coaxial gyrotron oscillator yielded power levels of greater than 1 MW in two different configurations: with the coaxial conductor (at 92kV, 70 A, and 16% efficiency) and without the coaxial conductor (85 kV, 65 A, and 18% efficiency). We also successfully operated this tube in three configurations (empty cavity, radial output, and axial output) with no beam interception. We observed regimes of dominant single mode and multi-mode operation. We also identified electron beam asymmetries and tube alignment as two major issues, which can limit the performance of a coaxial gyrotron. An unexpected source of magnetic field error was found in the magnetization of the stainless steel parts. All these results have led to techniques for improving not only coaxial gyrotrons but also other gyrotron tubes. We also investigated a ferroelectric cathode, which has the potential to achieve higher currents than thermionic cathodes in a simpler, low cost gun. We report the first results on a ferroelectric cathode gun in a magnetron injection gun configuration suitable for use in a gyrotron. It had an annular emitter shape with a diameter of 11.4 cm and a width of 0.25 cm and operated at currents of up to 10 A (1.1 A/cm2) at 8 kV, in 5 μs flat-top pulses. This result (along with the kiloampere beam obtained at Integrated Applied Physics) demonstrate the scalability of ferroelectric cathodes to large diameter

  12. ECH by FEL and gyrotron sources on the Microwave Tokamak Experiment (MTX) tokamak

    SciTech Connect

    Stallard, B.W.; Turner, W.C.; Allen, S.L.; Byers, J.A.; Felker, B.; Fenstermacher, M.E.; Ferguson, S.W.; Hooper, E.G.; Thomassen, K.I.; Throop, A.L. ); Makowski, M.A. )

    1990-08-09

    The Microwave Tokamak Experiment (MTX) at LLNL is studying the physics of intense pulse ECH is a high-density tokamak plasma using a microwave FEL. Related technology development includes the FEL, a windowless quasi-optical transmission system, and other microwave components. Initial plasma experiments have been carried out at 140 GHz with single rf pulses generated using the ETA-II accelerator and the ELF wiggler. Peak power levels up to 0.2 GW and pulse durations up to 10 ns were achieved for injection into the plasma using as untapered wiggler. FEL pulses were transmitted over 33 m from the FEL to MTX using six mirrors mounted in a 50-cm-diam evacuated pipe. Measurements of the microwave beam and transmission through the plasma were carried out. For future rapid pulse experiments at high average power (4 GW peak power, 5kHz pulse rate, and {bar P} > 0.5 MW) using the IMP wiggler with tapered magnetic field, a gyrotron (140 GHz, 400 kW cw or up to 1 MW short pulse) is being installed to drive the FEL input or to directly heat the tokamak plasma at full gyrotron power. Quasi-optic techniques will be used to couple the gyrotron power. For direct plasma heating, the gyrotron will couple into the existing mirror transport system. Using both sources of rf generation, experiments are planned to investigate intense pulse absorption and tokamak physics, such as the ECH of a pellet-fueled plasma and plasma control using localized heating. 12 refs., 9 figs.

  13. Final Report for "Gyrotron Design and Evaluation using New Particle-in-Cell Capability"

    SciTech Connect

    David N Smithe

    2008-05-28

    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&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.

  14. CW-pulsed laser

    SciTech Connect

    Wert, J. C.

    1981-09-01

    An apparatus for generating a spatially coherent laser beam having both CW and pulsed modes is disclosed. The modes are generated in differing volumetric regions of a single gain medium excited by a continuous energy pump. The CW portion of the output beam passes from the gain medium through a partially transmissive output coupling. The pulsed modes in the output beam are created in the respective region of the gain medium when transition materials from a selected group are stimulated to undergo an abrupt change between their reflective and transmissive states. Either cavity dumped or Q-switched configurations can be created by selective and patterned location of the transition materials at the ends of the gain medium. Symmetric organization of the volumetric regions within the gain medium allows temporal superposition of the two modes while maintaining spatial distinctiveness within the laser beam generated.

  15. Electron-optical systems for planar gyrotrons

    NASA Astrophysics Data System (ADS)

    Manuilov, V. N.; Zaslavsky, V. Yu.; Ginzburg, N. S.; Glyavin, M. Yu.; Kuftin, A. N.; Zotova, I. V.

    2014-02-01

    The methodology of designing an electron-optical system (EOS) that forms sheet helical electron beams (HEBs) for high-power gyrotrons is developed. As an example, we consider the EOS for a 140-GHz gyrotron operated at the first harmonic of the cyclotron frequency with an accelerating voltage of 50 kV, a beam current of 30 A, and a magnetic field compression of 36. A planar geometry of the magnetron-injection gun (MIG) is suggested. The adiabatic theory of MIGs modified for the planar geometry of EOS is used for preliminary estimations of MIG parameters. Numerical simulation of the HEB properties based on the CST STUDIO SUITE 3D code is performed to find the optimal configuration of a planar MIG. The accuracy of the calculated data is discussed. The main factors that affect the HEB quality are considered. It is shown that a sheet HEB with a pitch-factor of 1.3 and velocity spread not exceeding 25%-30% can be formed; this is quite acceptable for high-efficiency operation of modern gyrotrons. Calculation of the beam-wave interaction with the obtained HEB parameters proved that a high output power with a sufficiently good efficiency of about 20% can be reached. Simulations show the feasibility of the experimental implementation of a novel planar EOS and its use in short-wave planar gyrotrons. The developed technique can be used for the study and optimization of planar gyrotrons of different frequency bands and power levels.

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

    SciTech Connect

    J. Lohr; P. Calahan; R.W. Callis; T.S. Chu; J.S. deGrassie; I. Gorelov; H. Ikezi; R.A. Legg; T.C. Luce; C.C. Petty; D. Ponce; R. Prater; D.J. Schuster; S.E. Tsimring

    1999-12-01

    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.

  17. Linear theory of frequency pulling in gyrotrons

    NASA Astrophysics Data System (ADS)

    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.

  18. Compact, harmonic multiplying gyrotron amplifiers

    SciTech Connect

    Guo, H.Z.; Granatstein, V.L.; Antonsen, T.M. Jr.; Levush, B.; Tate, J.; Chen, S.H.

    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.

  19. Electron gun simulation for 95 GHz gyrotron

    SciTech Connect

    Singh, Udaybir; Kumar, Nitin; Sinha, A.K. E-mail: aksinha@ceeri.ernet.in; Purohit, L.P.

    2011-07-01

    A triode type Magnetron Injection Gun (MIG) for a 2 MW, 95 GHz Gyrotron has been designed by using commercially available code EGUN and another in-house developed code MIGANS. The operating mode of the gyrotron is TE{sub 24.8} and it is operated in the fundamental harmonic. The operating voltages of the modulating anode and the accelerating anode are 61 kV and 85 kV respectively. The parametric dependences of modulating anode voltage and cathode magnetic field on the beam quality have also been studied. (author)

  20. The K(a)-band 10-kW continuous wave gyrotron with wide-band fast frequency sweep.

    PubMed

    Glyavin, M; Luchinin, A; Morozkin, M

    2012-07-01

    The dual-frequency gyrotron with fast 2% frequency sweep at about 28 GHz is designed to power an electron cyclotron resonance ion source (ECRIS). Operation with an output power of up to 10 kW in CW mode and efficiency of 20% was demonstrated at both frequencies. Frequency manipulation has a characteristic time of about 1 ms and is based on magnetic field variation with an additional low-power coil. Fast frequency sweep will supposedly increase the ion current and the average ion charge of ECRIS. The possibility of 100% power modulation is demonstrated using the same control method. PMID:22852711

  1. The Ka-band 10-kW continuous wave gyrotron with wide-band fast frequency sweep

    NASA Astrophysics Data System (ADS)

    Glyavin, M.; Luchinin, A.; Morozkin, M.

    2012-07-01

    The dual-frequency gyrotron with fast 2% frequency sweep at about 28 GHz is designed to power an electron cyclotron resonance ion source (ECRIS). Operation with an output power of up to 10 kW in CW mode and efficiency of 20% was demonstrated at both frequencies. Frequency manipulation has a characteristic time of about 1 ms and is based on magnetic field variation with an additional low-power coil. Fast frequency sweep will supposedly increase the ion current and the average ion charge of ECRIS. The possibility of 100% power modulation is demonstrated using the same control method.

  2. Gyrotron Performance on the 110 GHZ Installation at the DIII-D Tokamak

    SciTech Connect

    Gorelov, I.; Lohr, J.M.; Ponce, D.; Callis, R.W.; Ikezi, H.; Legg, R.A.; Tsimring, S.E.

    1999-06-01

    The 110 GHz gyrotron system on the DIII-D tokamak comprises three different gyrotrons in the 1 MW class. The individual gyrotron characteristics and the operational experience with the system are described.

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

    NASA Astrophysics Data System (ADS)

    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 (<35 GHz), medium power (<100 kW), small size and easy to handle gyrotrons for industrial applications, 2. very high power (1 MW or more), medium frequency (100-200 GHz) gyrotrons for plasma fusion applications, 3. low power (few tens of watt to kW), high 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.

  4. Mode suppression means for gyrotron cavities

    DOEpatents

    Chodorow, Marvin; Symons, Robert S.

    1983-08-09

    In a gyrotron electron tube of the gyro-klystron or gyro-monotron type, having a cavity supporting an electromagnetic mode with circular electric field, spurious resonances can occur in modes having noncircular electric field. These spurious resonances are damped and their frequencies shifted by a circular groove in the cavity parallel to the electric field.

  5. Electron-optical systems for planar gyrotrons

    SciTech Connect

    Manuilov, V. N.; Zaslavsky, V. Yu.; Ginzburg, N. S.; Glyavin, M. Yu.; Kuftin, A. N.; Zotova, I. V.

    2014-02-15

    The methodology of designing an electron-optical system (EOS) that forms sheet helical electron beams (HEBs) for high-power gyrotrons is developed. As an example, we consider the EOS for a 140-GHz gyrotron operated at the first harmonic of the cyclotron frequency with an accelerating voltage of 50 kV, a beam current of 30 A, and a magnetic field compression of 36. A planar geometry of the magnetron-injection gun (MIG) is suggested. The adiabatic theory of MIGs modified for the planar geometry of EOS is used for preliminary estimations of MIG parameters. Numerical simulation of the HEB properties based on the CST STUDIO SUITE 3D code is performed to find the optimal configuration of a planar MIG. The accuracy of the calculated data is discussed. The main factors that affect the HEB quality are considered. It is shown that a sheet HEB with a pitch-factor of 1.3 and velocity spread not exceeding 25%–30% can be formed; this is quite acceptable for high-efficiency operation of modern gyrotrons. Calculation of the beam-wave interaction with the obtained HEB parameters proved that a high output power with a sufficiently good efficiency of about 20% can be reached. Simulations show the feasibility of the experimental implementation of a novel planar EOS and its use in short-wave planar gyrotrons. The developed technique can be used for the study and optimization of planar gyrotrons of different frequency bands and power levels.

  6. CW laser light condensation.

    PubMed

    Zhurahov, Michael; Bekker, Alexander; Levit, Boris; Weill, Rafi; Fischer, Baruch

    2016-03-21

    We present a first experimental demonstration of classical CW laser light condensation (LC) in the frequency (mode) domain that verifies its prediction (Fischer and Weill, Opt. Express20, 26704 (2012)). LC is based on weighting the modes in a noisy environment in a loss-gain measure compared to an energy (frequency) scale in Bose-Einstein condensation (BEC). It is characterized by a sharp transition from multi- to single-mode oscillation, occurring when the spectral-filtering (loss-trap) has near the lowest-loss mode ("ground-state") a power-law dependence with an exponent smaller than 1. An important meaning of the many-mode LC system stems from its relation to lasing and photon-BEC. PMID:27136845

  7. Studies of a Gyrotron with the Echelette Cavity

    NASA Astrophysics Data System (ADS)

    Belousov, V. I.; Vlasov, S. N.; Zavolsky, N. A.; Zapevalov, V. E.; Koposova, E. V.; Kornishin, S. Yu.; Kuftin, A. N.; Moiseev, M. A.; Khizhnyak, V. I.

    2014-11-01

    We describe a gyrotron which is operated at the first gyrofrequency harmonic and has an echelette cavity with the sinusoidal corrugation profile. A method for calculating the parameters of the echelette cavity and the gyrotron is described. The results of measuring the electrodynamic characteristics of the echelette cavity and studying experimentally the gyrotron with such a cavity are presented. It is shown that the gyrotron has a rarefied spectrum of eigenoscillations and the efficiency at the level of typical megawatt-power gyrotrons, and is characterized by a significantly lower degree of cavity wall heating. The structure of radiation from the gyrotron with the echelette cavity and the possibility of transmitting this radiation by means of a mirror waveguide, are discussed.

  8. On optimization of sub-THz gyrotron parameters

    SciTech Connect

    Dumbrajs, O.; Nusinovich, G. S.

    2012-10-15

    The theory is developed describing how the optimization of gyrotron parameters should be done taking into account two effects deteriorating the gyrotron efficiency: the spread in electron velocities and the spread in the guiding center radii. The paper starts from qualitative analysis of the problem. This simplified theory is used for making some estimates for a specific gyrotron design. The same design is then studied by using more accurate numerical methods. Results of the latter treatment agree with former qualitative predictions.

  9. Analysis of cavity and window for THz gyrotron

    SciTech Connect

    Alaria, Mukesh Kumar; Mukherjee, P.; Rao, R.R.; Sinha, A.K. E-mail: aksinha@ceeri.ernet.in

    2011-07-01

    In this paper study of cavity and window has been carried out using Ansoft HFSS for Terahertz Gyrotron. Eigen mode analysis of the cavity has been carried out at 1 THz. An idea about the operating modes in the cavity of the Gyrotron and obtained the simulated Eigen frequency and field pattern of the modes. The design of window for 1 THz Gyrotron has also been carried out using HFSS. The simulated results have also been compared with ST microwave studio. (author)

  10. Influence of Controlled Reflected Power on Gyrotron Performance

    NASA Astrophysics Data System (ADS)

    Kharchev, N.; Cappa, Á.; Malakhov, D.; Martínez, J.; Konchekov, E.; Tolkachev, A.; Borzosekov, V.; Sarksyan, K.; Petelin, M.

    2015-12-01

    This paper describes the reaction of a gyrotron oscillator when a very small fraction of its radiation, extracted from the main beam, is phase-modulated in a controlled way and is finally redirected back to the gyrotron. The gyrotron may exhibit a 10 % modulation of its total power even if the reflected power is lower than 1 %. Moreover, radial probing of the beam power distribution shows that the amplitude of the power modulation differs at different radial positions across the beam.

  11. High harmonic terahertz confocal gyrotron with nonuniform electron beam

    NASA Astrophysics Data System (ADS)

    Fu, Wenjie; Guan, Xiaotong; Yan, Yang

    2016-01-01

    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.

  12. High-harmonic gyrotron with sectioned cavity

    SciTech Connect

    Bandurkin, I. V.; Kalynov, Yu. K.; Savilov, A. V.

    2010-07-15

    High-harmonic large-orbit gyrotrons require long-length operating cavities because of both a weak electron-wave coupling and relatively low electron currents. Since diffraction Q factors of such cavities are very high, a large fraction of the radiated power is dissipated in Ohmic losses. A sectioned klystronlike cavity can be a way to combine a long electron-wave interaction region with a relatively low diffraction Q factor. In this paper, a design of a third-harmonic terahertz gyrotron is studied in detail and discussed. As compared to a regular cavity, the use of a sectioned microwave system provides an enhancement of the output rf power by several times along with the halving of the Ohmic losses.

  13. Soviet development of gyrotrons. Interim report

    SciTech Connect

    Kassel

    1986-05-01

    This report surveys the development of high power cyclotron-resonance masers (CRM) and gyrotrons in the Soviet Union, based on Soviet open-source literature. It deals with the nature and history of relativistic CRM devices; provides a sequence of the most important issues of gyrotron research and develoment as perceived by Soviet authors; and discusses individual Soviet research groups, the basic organizational units responsible for the CRM and gyrotron research and development. The study suggests, among other things, that high-power relativistic microwave electronics is one of the most successful areas of Soviet RandD. It has maintained a consistent record of significant achievements; it has managed to overcome the systemic weakness of the Soviet RandD system in being able to translate effectively the results of advanced research into production of practical equipment; and it has become the fastest growing area of application of pulsed-power technology, which itself has been for many years the subject of priority development in the USSR.

  14. Improved Collectors for High Power Gyrotrons

    SciTech Connect

    Ives, R. Lawrence; Singh, Amarjit; Read, Michael; Borchard, Phillipp; Neilson, Jeff

    2009-05-20

    High power gyrotrons are used for electron cyclotron heating, current drive and parasitic mode suppression in tokamaks for fusion energy research. These devices are crucial for successful operation of many research programs around the world, including the ITER program currently being constructed in France. Recent gyrotron failures resulted from cyclic fatigue of the copper material used to fabricated the collectors. The techniques used to collect the spent beam power is common in many gyrotrons produced around the world. There is serious concern that these tubes may also be at risk from cyclic fatigue. This program addresses the cause of the collector failure. The Phase I program successfully demonstrated feasibility of a mode of operation that eliminates the cyclic operation that caused the failure. It also demonstrated that new material can provide increased lifetime under cyclic operation that could increase the lifetime by more than on order of magnitude. The Phase II program will complete that research and develop a collector that eliminates the fatigue failures. Such a design would find application around the world.

  15. Regions of azimuthal instability in gyrotrons

    SciTech Connect

    Dumbrajs, O.; Nusinovich, G. S.; Antonsen, T. M. Jr.

    2012-06-15

    This paper is devoted to the analysis of the instability of operating modes in high-power gyrotrons with cylindrically symmetric resonators. This instability manifests itself in destruction of the azimuthally uniform wave envelope rotating in a gyrotron resonator having a transverse size greatly exceeding the wavelength. The appearance of azimuthally nonuniform solutions can be interpreted as simultaneous excitation of modes with different azimuthal indices. This problem is studied self-consistently, i.e., taking into account the temporal evolution of both the azimuthal and axial structures of the wave envelope. The region of gyrotron operation free from this instability is identified. The efficiency achievable in this region can be only 1%-2% lower than the maximum efficiency. It is also possible to address the difference between the theory of mode interaction developed under assumption that all modes have fixed axial structure and the self-consistent theory presented here. As known, for fixed axial mode profiles, single-mode high-efficiency oscillations remain stable no matter how dense is the spectrum of competing modes, while the self-consistent theory predicts stable high-efficiency operation only when the azimuthal index does not exceed a certain critical value. It is shown that the azimuthal instability found in the self-consistent theory is caused by excitation of modes having axial structures different from that of the desired central mode.

  16. Regions of azimuthal instability in gyrotrons

    NASA Astrophysics Data System (ADS)

    Dumbrajs, O.; Nusinovich, G. S.; Antonsen, T. M.

    2012-06-01

    This paper is devoted to the analysis of the instability of operating modes in high-power gyrotrons with cylindrically symmetric resonators. This instability manifests itself in destruction of the azimuthally uniform wave envelope rotating in a gyrotron resonator having a transverse size greatly exceeding the wavelength. The appearance of azimuthally nonuniform solutions can be interpreted as simultaneous excitation of modes with different azimuthal indices. This problem is studied self-consistently, i.e., taking into account the temporal evolution of both the azimuthal and axial structures of the wave envelope. The region of gyrotron operation free from this instability is identified. The efficiency achievable in this region can be only 1%-2% lower than the maximum efficiency. It is also possible to address the difference between the theory of mode interaction developed under assumption that all modes have fixed axial structure and the self-consistent theory presented here. As known, for fixed axial mode profiles, single-mode high-efficiency oscillations remain stable no matter how dense is the spectrum of competing modes, while the self-consistent theory predicts stable high-efficiency operation only when the azimuthal index does not exceed a certain critical value. It is shown that the azimuthal instability found in the self-consistent theory is caused by excitation of modes having axial structures different from that of the desired central mode.

  17. A vacuum window for a 1 MW CW 110 GHz gyrotron

    SciTech Connect

    Moeller, C.P.; Doane, J.L.; DiMartino, M.

    1994-07-01

    Development of high power microwave sources for fusion applications is limited by the availability of suitable vacuum windows in the 100 to 200 GHz frequency range. A novel vacuum window is described which uses water cooled sapphire as the dielectric. Heat removal is achieved by using thin slats of sapphire interleaved and brazed to niobium hexagonal tubes in which the cooling water flows. Analysis indicates a window 100 cm{sup 2} in area can readily pass 1 MW in the HE{sub 11} mode at 110 GHz for current experimental applications and 1 MW with a HE{sub 11}{sup 0}-HE{sub 12}{sup 0} mixture at 170 GHz, the projected ITER frequency.

  18. Phonological and Phonetic Asymmetries of Cw Combinations

    ERIC Educational Resources Information Center

    Suh, Yunju

    2009-01-01

    This thesis investigates the relationship between the phonological distribution of Cw combinations, and the acoustic/perceptual distinctiveness between syllables with plain C onsets and with Cw combination onsets. Distributional asymmetries of Cw combinations discussed in this thesis include the avoidance of Cw combinations in the labial consonant…

  19. The coaxial gyrotron with two electron beams. I. Linear theory and nonlinear theory

    SciTech Connect

    Liu Shenggang; Yuan Xuesong; Fu Wengjie; Yan Yang; Zhang Yaxin; Li Hongfu; Zhong Renbin

    2007-10-15

    The coaxial gyrotron with two electron beams (CGTB) is proposed and investigated in this paper. This paper consists of two parts: the linear theory and nonlinear theory of CGTB are presented in part I and the investigation on the dual frequency operation, a special operation state of CGTB, is given in part II. The magnetron injection gun with two electron beams has been developed, and simulations show that it may work well. It may guarantee that both the electric potential and the ratio of vertical to longitudinal velocities of two electron beams are equal. The results of the calculation show that CGTB has some distinguished advantages: mode competition is improved and output power is enhanced. Thus CGTB may be capable of providing 2-4 MW continuous-wave (CW) at 170 GHz to meet the demand of very high radio frequency CW power 1-2 MW in the ITER [ITER EDA Agreement and Protocol 2 (IAEA, Vienna, 1994)] program and other applications.

  20. Single-stage depressed collectors for gyrotrons

    SciTech Connect

    Piosczyk, B.; Iatrou, C.T.; Dammertz, G.; Thumm, M. |

    1996-06-01

    Two 140 GHz gyrotrons with a single-step depressed collector have been operated. The different position of the isolating collector gap in the stray magnetic field causes the electron motion in the retarding region to be in one case adiabatic and in the other case nonadiabatic. The kind of motion within the retarding field influences strongly the behavior of the gyrotron with a depressed collector. In the case of nonadiabatic motion a significant amount of transverse momentum is given to the electrons reflected at the collector potential. This causes the reflected electrons to be trapped between the magnetic mirror and the collector. The electrons escape from the trap by diffusion across the magnetic field to the body of the tube thus contributing to the body current. Despite the high body current there is no observable influence of the collector voltage on the RF output power. In the case of adiabatic motion the reflected electrons do not gain a sufficient amount of transverse momentum to be trapped by the magnetic mirror. They pass the cavity toward the gun and they are trapped between the negative gun potential and the collector. The interaction with the RF field by electrons traveling through the cavity enhances the diffusion in the velocity space thus enabling the trapped electrons to overcome the potential barrier and escape toward the collector. Therefore the body current stays at low values since in this case the reflected electrons do not contribute to it. However, at higher collector voltages a reduction of RF power occurred and some noise in the electron beam was observed. The main motivation for the development of gyrotrons in the frequency range above 100 GHz with power levels in excess of several hundreds kW per tube, is the application in magnetic fusion devices for plasma heating and for electron current drive.

  1. 95 GHz gyrotron with ferroelectric cathode.

    PubMed

    Einat, M; Pilossof, M; Ben-Moshe, R; Hirshbein, H; Borodin, D

    2012-11-01

    Ferroelectric cathodes were reported as a feasible electron source for microwave tubes. However, due to the surface plasma emission characterizing this cathode, operation of millimeter wave tubes based on it remains questionable. Nevertheless, the interest in compact high power sources of millimeter waves and specifically 95 GHz is continually growing. In this experiment, a ferroelectric cathode is used as an electron source for a gyrotron with the output frequency extended up to 95 GHz. Power above a 5 kW peak and ~0.5 μs pulses are reported; a duty cycle of 10% is estimated to be achievable. PMID:23215293

  2. The K{sub a}-band 10-kW continuous wave gyrotron with wide-band fast frequency sweep

    SciTech Connect

    Glyavin, M.; Luchinin, A.; Morozkin, M.

    2012-07-15

    The dual-frequency gyrotron with fast 2% frequency sweep at about 28 GHz is designed to power an electron cyclotron resonance ion source (ECRIS). Operation with an output power of up to 10 kW in CW mode and efficiency of 20% was demonstrated at both frequencies. Frequency manipulation has a characteristic time of about 1 ms and is based on magnetic field variation with an additional low-power coil. Fast frequency sweep will supposedly increase the ion current and the average ion charge of ECRIS. The possibility of 100% power modulation is demonstrated using the same control method.

  3. Design of Matching Optics Unit (MOU) for coaxial ITER gyrotron

    SciTech Connect

    Jin, Jianbo; Gantenbein, Gerd; Kern, Stefan; Rzesnicki, Tomasz; Thumm, Manfred

    2011-07-01

    The paper presents the design of a MOU for the coaxial ITER gyrotron. Corrugated waveguides are used to transmit the high power mm-waves generated by gyrotrons to the plasma Electron Cyclotron Resonance Heating (ECRH) and Current Drive (CD). The MOU contains two focusing mirrors, which are used to convert the gyrotron output into a Gaussian distribution with optimal parameters to improve the coupling efficiency of the TEM{sub 00} Gaussian distribution to the HE{sub 11} mode of the corrugated wave guide. The calculation results reveal that the coupling efficiency of the Gaussian beam to the HE{sub 11} mode is approximately 96.33%. (author)

  4. Quasi-optical harmonic gyrotron and gyroklystron

    NASA Astrophysics Data System (ADS)

    Manheimer, W.; Levush, B.

    1985-12-01

    This patent discloses 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 high 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 therethrough the beam of electrons and for exchanging energy therewith. This method includes the steps for choosing a mirror radius size large enough relative to the spot size of a desired radiation cyclotron harmonic so that the harmonic oscillates within the at least one resonator, but small enough so that the spot size for the next lower cyclotron harmonic is larger than the mirror so that harmonic does not oscillate due to diffraction losses. This method further includes the step of generating an electron beam bias the electron beam source with a beam current which is greater than or equal to the starting current for the desired nth cyclotron harmonic, but less than the starting current for the nth cyclotron harmonic.

  5. Reflections in gyrotrons with radial output: Consequences for the ITER coaxial gyrotron

    SciTech Connect

    Dumbrajs, O.; Nusinovich, G.S.; Piosczyk, B.

    2004-12-01

    A theory describing the influence of reflections on operation of gyrotrons with radial output is presented. The theory is used for evaluating the effect of reflections on the operation of the 170 GHz ITER coaxial cavity gyrotron, which is under development in cooperation between EUROATOM Associations (CRPP Lausanne, FZK Karlsruhe, and HUT Helsinki) together with European tube industry (Thales Electron Devices, Velizy, France). It is shown that for optimally chosen external magnetic field value and electron beam radius, possible reflections do not change the final steady-state operation, which corresponds to generation of a 2.2 MW millimeter-wave power. The effect of deviation of the magnetic field and the beam radius from optimal values on the device operation is also studied.

  6. Gyrotron cavity resonator with an improved value of Q

    DOEpatents

    Stone, David S.; Shively, James F.

    1982-10-26

    A gyrotron cavity resonator is connected smoothly and directly to an output waveguide with a very gradually tapered wall so that values of external Q lower than twice the diffraction limit are obtainable.

  7. Harmonic gyrotrons operating in high-order symmetric modes

    SciTech Connect

    Nusinovich, Gregory S.; Kashyn, Dmytro G.; Antonsen, T. M.

    2015-01-05

    It is shown that gyrotrons operating at cyclotron harmonics can be designed for operation in symmetric TE{sub 0,p}-modes. Such operation in fundamental harmonic gyrotrons is possible only at small radial indices (p≤3) because of the severe mode competition with TE{sub 2,p}-modes, which are equally coupled to annular beams as the symmetric modes. At cyclotron harmonics, however, this “degeneracy” of coupling is absent, and there is a region in the parameter space where harmonic gyrotrons can steadily operate in symmetric modes. This fact is especially important for sub-THz and THz-range gyrotrons where ohmic losses limit the power achievable in continuous-wave and high duty cycle regimes.

  8. The 10-100 kW submillimeter gyrotron

    NASA Technical Reports Server (NTRS)

    Spira, S.; Kreischer, K. E.; Temkin, R. J.

    1989-01-01

    High frequency high harmonic gyrotrons; cyclotron autoresonance maser (CARM); CARM amplifier schematics; MIT electron gun; and baseline design for the 140 GHz CARM amplifier are briefly reviewed. This presentation is represented by viewgraphs only.

  9. Effect of electron beam misalignments on the gyrotron efficiency

    SciTech Connect

    Dumbrajs, O.; Nusinovich, G. S.

    2013-07-15

    The theory describing the operation of gyrotrons with tilted and shifted electron beams has been developed. Effects of the tilt and shift are studied for a 1 MW, 170 GHz gyrotron, which is presently under development in Europe for electron cyclotron resonance plasma heating and current drive in the International Thermonuclear Experimental Reactor. It is shown that one should expect significant deterioration of gyrotron operation in such gyrotrons when the tilt angle exceeds 0.4°–0.5° and the parallel shift of the beam axis with respect to the axis of a microwave circuit is larger than 0.4–0.5 mm. At the same time, simultaneous tilting and shifting in a proper manner can mitigate this deteriorating effect.

  10. Analysis of a high harmonic rectangular gyrotron using ribbon beams

    NASA Technical Reports Server (NTRS)

    Ferendeci, Altan M.

    1989-01-01

    Cylindrical cavity structures and electron orbits; a grooved gyrotron using a ribbon beam; construction details; radiation patterns; radiation distribution; phase distribution; energy curves; and advantages are outlined. This presentation is represented by viewgraphs and charts only.

  11. Slow processes in startup scenarios of long-pulse gyrotrons

    SciTech Connect

    Nusinovich, G. S.; Sinitsyn, O. V.; Antonsen, T. M. Jr.; Vlasov, A. N.; Cauffman, S. R.; Felch, K. L.

    2006-08-15

    A gyrotron startup scenario describes the variation of gyrotron parameters during onset of a pulse. This typically includes variations in beam parameters during the voltage rise, in the course of which the operating mode is excited and then driven to high efficiency operation while suppressing other parasitic modes. For long-pulse gyrotrons, however, additional processes with longer time constants should also be considered as part of the startup scenario. Such slow processes include ion neutralization of the beam space charge, thermal expansion of cavity walls caused by their ohmic heating, and reduction of the beam current due to emission cooling of the cathode. In the present paper, we analyze the importance of these effects on the stability and efficiency of gyrotron operation.

  12. The Multiple Gyrotron System on the DIII-D Tokamak

    NASA Astrophysics Data System (ADS)

    Lohr, J.; Anderson, J.; Brambila, R.; Cengher, M.; Chen, X.; Ellis, R. A.; Grosnickle, W.; Moeller, C.; Prater, R.; Ponce, D.; Riford, L.; Torrezan, A. C.

    2016-01-01

    A major component of the versatile heating systems on the DIII-D tokamak is the gyrotron complex. This system routinely operates at 110 GHz with 4.7 MW-generated rf power for electron cyclotron heating and current drive. The complex is being upgraded with the addition of new depressed collector potential gyrotrons operating at 117.5 GHz and generating rf power in excess of 1.0 MW each. The long-term upgrade plan calls for 10 gyrotrons at the higher frequency being phased in as resources permit, for an injected power near 10 MW. This paper presents a summary of the current status of the DIII-D gyrotron complex, its performance, individual components, testing procedures, operational parameters, plans, and a brief summary of the experiments for which the system is currently being used.

  13. Electron dynamics in the process of mode switching in gyrotrons

    SciTech Connect

    Dumbrajs, O.; Kominis, Y.; Nusinovich, G. S.

    2009-01-15

    The present paper is devoted to the analysis of electron interaction process in the course of gyrotron switching from one mode to another. This analysis is based on the use of the Hamiltonian formalism that allows one to construct Poincare plots for different instants of switching time. The study is carried out for a 170 GHz, MW-class gyrotron for the International Thermonuclear Experimental Reactor (ITER) [ITER web site: http://www.iter.org].

  14. Low-Q cavities for high-power gyrotrons

    SciTech Connect

    Zapevalov, V.E.; Kalynov, Y.K.; Kuftin, A.N.

    1994-09-01

    The parameters of free oscillations in gyrotoron resonators with a lowered reflection from the diffractive energy output for the purpose of reducing ohmic heating by rf power loss have been calculated. A gyrotron with such a cavity has been studied experimentally. The gyrotron had an efficiency of more than 45% with an output of 350 to 700 kW when operating in the 3.6-mm H{sub 11,3} mode.

  15. Application of Continuously Frequency-Tunable 0.4 THz Gyrotron to Dynamic Nuclear Polarization for 600 MHz Solid-State NMR

    NASA Astrophysics Data System (ADS)

    Matsuki, Yoh; Ueda, Keisuke; Idehara, Toshitaka; Ikeda, Ryosuke; Kosuga, Kosuke; Ogawa, Isamu; Nakamura, Shinji; Toda, Mitsuru; Anai, Takahiro; Fujiwara, Toshimichi

    2012-07-01

    In this paper we present results that demonstrate the utility of a continuously frequency-tunable 0.4 THz-gyrotron in a dynamic nuclear polarization (DNP)-enhanced solid-state NMR (SSNMR) spectroscopy at one of the highest magnetic fields, B 0 = 14.1 T (600 MHz for 1H Larmor frequency). Our gyrotron called FU CW VI generates sub-mm wave at a frequency near 0.4 THz with an output power of 4-25 W and a tunability over a range of more than 1 GHz by sweeping the magnetic field at the gyrotron cavity. We observed overall down shifting of the central frequency by up to ~1 GHz at high radiation duty factors and beam current, presumably due to the cavity thermal expansion by a heating, but the tunable range was not significantly changed. The frequency tunability facilitated the optimization of the DNP resonance condition without time-consuming field-sweep of the high-resolution NMR magnet, and enabled us to observe substantial enhancement of the SSNMR signal ( ɛ DNP = 12 at 90 K).

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

    NASA Astrophysics Data System (ADS)

    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

  17. Spectral Characteristics of a 140-GHz Long-Pulsed Gyrotron.

    PubMed

    Han, Seong-Tae; Griffin, Robert G; Hu, Kan-Nian; Joo, Chan-Gyu; Joye, Colin D; Sirigiri, Jagadishwar R; Temkin, Richard J; Torrezan, Antonio C; Woskov, Paul P

    2007-06-01

    Gyrotrons operating in the millimeter and submillimeter wavelength ranges are the promising sources for applications that are requiring good spectral characteristics and a wide range of output power. We report the precise measurement results of gyrotron spectra. Experiments were conducted using a 140-GHz long-pulse gyrotron that is developed for the dynamic nuclear polarization/nuclear-magnetic-resonance spectroscopy at the Massachusetts Institute of Technology. Transient downshift of the frequency by 12 MHz with a time constant of 3 s was observed. After reaching equilibrium, the frequency was maintained within 1 ppm for over 20 s. The coefficient of the frequency change with cavity temperature was -2.0 MHz/K, which shows that fine tuning of the gyrotron frequency is plausible by cavity-temperature control. Frequency pulling by the beam current was observed, but it was shown to be masked by the downward shift of the gyrotron frequency with temperature. The linewidth was measured to be much less than 1 MHz at 60 dB relative to the carrier power [in decibels relative to carrier (dBc)] and 4.3 MHz at 75 dBc, which is the largest dynamic range to date for the measurement of gyrotron linewidth to our knowledge. PMID:19081779

  18. Spectral Characteristics of a 140-GHz Long-Pulsed Gyrotron

    PubMed Central

    Han, Seong-Tae; Griffin, Robert G.; Hu, Kan-Nian; Joo, Chan-Gyu; Joye, Colin D.; Sirigiri, Jagadishwar R.; Temkin, Richard J.; Torrezan, Antonio C.; Woskov, Paul P.

    2008-01-01

    Gyrotrons operating in the millimeter and submillimeter wavelength ranges are the promising sources for applications that are requiring good spectral characteristics and a wide range of output power. We report the precise measurement results of gyrotron spectra. Experiments were conducted using a 140-GHz long-pulse gyrotron that is developed for the dynamic nuclear polarization/nuclear-magnetic-resonance spectroscopy at the Massachusetts Institute of Technology. Transient downshift of the frequency by 12 MHz with a time constant of 3 s was observed. After reaching equilibrium, the frequency was maintained within 1 ppm for over 20 s. The coefficient of the frequency change with cavity temperature was −2.0 MHz/K, which shows that fine tuning of the gyrotron frequency is plausible by cavity-temperature control. Frequency pulling by the beam current was observed, but it was shown to be masked by the downward shift of the gyrotron frequency with temperature. The linewidth was measured to be much less than 1 MHz at 60 dB relative to the carrier power [in decibels relative to carrier (dBc)] and 4.3 MHz at 75 dBc, which is the largest dynamic range to date for the measurement of gyrotron linewidth to our knowledge. PMID:19081779

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

    NASA Technical Reports Server (NTRS)

    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.

  20. CW laser pumped emerald laser

    SciTech Connect

    Shand, M.L.; Lai, S.T.

    1984-02-01

    A CW laser-pumped emerald laser is reported. A 34 percent output power slope efficiency is observed with longitudinal pumping by a krypton laser in a nearly concentric cavity. The laser has been tuned from 728.8 to 809.0 nm. Losses in emerald are larger than those of alexandrite determined in a similar cavity. The present data also indicate that the excited state absorption minimum is shifted from that of alexandrite. 13 references.

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

    NASA Astrophysics Data System (ADS)

    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.

  2. High-Speed Frequency Modulation of a 460-GHz Gyrotron for Enhancement of 700-MHz DNP-NMR Spectroscopy

    NASA Astrophysics Data System (ADS)

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

    2015-09-01

    The high-speed frequency modulation of a 460-GHz Gyrotron FU CW GVI (the official name in Osaka University is Gyrotron FU CW GOI) was achieved by modulation of acceleration voltage of beam electrons. The modulation speed f m can be increased up to 10 kHz without decreasing the modulation amplitude δ f of frequency. The amplitude δ f was increased almost linearly with the modulation amplitude of acceleration voltage Δ V a. At the Δ V a = 1 kV, frequency spectrum width df was 50 MHz in the case of f m < 10 kHz. The frequency modulation was observed as both the variation of the IF frequency in the heterodyne detection system measured by a high-speed oscilloscope and the widths of frequency spectra df measured on a frequency spectrum analyzer. Both results well agree reasonably. When f m exceeds 10 kHz, the amplitude δ f is decreased gradually with increasing f m because of the degradation of the used amplifier in response for high-speed modulation. The experiment was performed successfully for both a sinusoidal wave and triangle wave modulations. We can use the high-speed frequency modulation for increasing the enhancement factor of the dynamic nuclear polarization (DNP)-enhanced nuclear magnetic resonance (NMR) spectroscopy, which is one of effective and attractive methods for the high-frequency DNP-NMR spectroscopy, for example, at 700 MHz. Because the sensitivity of NMR is inversely proportional to the frequency, high-speed frequency modulation can compensate the decreasing the enhancement factor in the high-frequency DNP-NMR spectroscopy and keep the factor at high value. In addition, the high-speed frequency modulation is useful for frequency stabilization by a PID control of an acceleration voltage by feeding back of the fluctuation of frequency. The frequency stabilization in long time is also useful for application of a DNP-NMR spectroscopy to the analysis of complicated protein molecules.

  3. Ultrastrong light-matter-coupling at 250 GHz

    NASA Astrophysics Data System (ADS)

    Maissen, Curdin; Scalari, Giacomo; Beck, Mattias; Faist, Jérôme; Reichl, Christian; Wegscheider, Werner

    2016-03-01

    The Ultrastrong light-matter coupling regime is attained when the coupling rate Ω is comparable or larger than the resonance frequency of the light ωLC and electronic transition frequency of the matter part ωc. This regime has attained much attention due to the peculiar properties of the coupled state. Here, we present a physical system showing a high normalized coupling rate not far from unity. The LC-mode of a THz-metasurface unitcell at ωLC = 2π x 0:25 THz is coupled to the collective cyclotron transition of 4 two dimensional electron gases (2DEGs) resulting in a normalized coupling rate of Ω/ωc = 0:9, Ω being the vacuum Rabi frequency. The high coupling rate is enabled by the small mode volume provided by the LC-mode of the split ring resonator geometry which was employed. Equally important is the large collective transition dipole element of the cyclotron transition.

  4. Gyrotron and its Electron Beam Source: A Review

    NASA Astrophysics Data System (ADS)

    Singh, Udaybir; Kumar, Nitin; Sinha, AK

    2012-10-01

    Microwave occupies a glorious position in the electromagnetic spectrum and in that there are a number of devices in this frequency regime which are capable of high power operations. Among them, gyrotron has proven to be an efficient source for radio frequency (RF) generation at high power level and up to very high frequency. The gyrotron consists of several components like electron beam source, interaction structure, quasi-optical launcher, collector, RF window, magnet system, etc. All the components have their distinct role in the function of the device. Among them, electron beam source also called magnetron injection gun (MIG) is the generator of electron beam and it is very essential that MIG should produce and provide electron beam suitable for the beam-wave interaction at the interaction structure for the effective power growth. The paper presents the introduction of a microwave tube, gyrotron and its components alongwith review of the previous work, the background and the applications. The functions of various components of a gyrotron are discussed with particular highlighting on the electron beam emission from the electron beam source and the beam-wave interaction for power growth in the device. A review on different types of gyrotron electron beam sources is also presented.

  5. Stability of gyrotron operation in very high-order modes

    SciTech Connect

    Sinitsyn, O. V.; Nusinovich, G. S.; Antonsen, T. M. Jr.

    2012-06-15

    This study was motivated by the desire to increase the power, which can be delivered by gyrotrons in long pulse and continuous regimes. Since the admissible power level is determined by the density of ohmic losses in resonator walls, to increase the radiated power a gyrotron should operate in higher order modes. Using an existing gyrotron developed for plasma experiments in the International Thermonuclear Experimental Reactor as a base model, the stability of operation of such a gyrotron in modes with larger number of radial variations was studied. It is shown that the power level achievable in such gyrotrons in stable single mode regimes is close to 1.5 MW. The power level 1.7-1.8 MW can be realized in regimes where the oscillations of the desired mode are accompanied by excitation of distant sidebands whose power is about 1% level of the power of the operating mode. Finally, in the case of operation at the 2-MW level, either the desired mode loses its stability and is replaced by less efficient oscillations of a mode with a smaller azimuthal index or oscillations of the operating mode are accompanied by excitation of sidebands with equally spaced frequencies.

  6. Development of multi-purpose MW gyrotrons for fusion devices

    NASA Astrophysics Data System (ADS)

    Minami, R.; Kariya, T.; Imai, T.; Numakura, T.; Endo, Y.; Nakabayashi, H.; Eguchi, T.; Shimozuma, T.; Kubo, S.; Yoshimura, Y.; Igami, H.; Takahashi, H.; Mutoh, T.; Ito, S.; Idei, H.; Zushi, H.; Yamaguchi, Y.; Sakamoto, K.; Mitsunaka, Y.; the GAMMA 10 Group

    2013-06-01

    The latest development achievements in the University of Tsukuba of over-1 MW power level gyrotrons required in present-day fusion devices, GAMMA 10, Large Helical Device (LHD), QUEST, Heliotron J and NSTX, are presented. The obtained maximum outputs are 1.9 MW for 0.1 s on the 77 GHz LHD tube and 1.2 MW for 1 ms on the 28 GHz GAMMA 10 one, which are new records in these frequency ranges. In long-pulse operation, 0.3 MW for 40 min at 77 GHz and 0.54 MW for 2 s at 28 GHz are achieved. A new programme of 154 GHz 1 MW development has started for high-density plasma heating in LHD. On the first 154 GHz tube, 1.0 MW for 1 s is achieved. As a next activity of the 28 GHz gyrotron, an over-1.5 MW gyrotron is designed and fabricated to study the multi-MW oscillation. The possibility of 0.4 MW continuous wave and 2 MW level output in operations of a few seconds, after the improvements of output window and mode converter, is shown. Moreover, a new design study of dual-frequency gyrotron at 28 and 35 GHz has started, which indicates the practicability of the multi-purpose gyrotron.

  7. CW ultrasonic bolt tensioning monitor

    NASA Technical Reports Server (NTRS)

    Heyman, J. S. (Inventor)

    1977-01-01

    A CW ultrasonic device is described for measuring frequency shifts of the peak of a mechanical resonance in a body. One application of the device is measuring the strain in a bolt, and other applications such as measuring the thickness of a body, measuring the depth of a flaw in a body, measuring the elongation of a body, and measuring changes in velocity of sound in a body. The body is connected, by means of a CW transducer, to electrical circuit means including a narrow band RF amplifier to form a closed loop feedback marginal oscillator that frequency locks the device to the peak of a mechanical resonance in the body. When the frequency of this peak changes, because of a physical change in the body, the frequency of the oscillator changes. The device includes an automatic frequency resonant peak tracker that produces a voltage that is related to a change in frequency of the oscillator. This voltage is applied to the RF amplifier to change the center of its frequency band to include the frequency of the peak and is a measure of the frequency shift.

  8. Possibilities for reducing the aftercavity interaction effect in gyrotrons

    SciTech Connect

    Sinitsyn, O. V.; Nusinovich, G. S.; Antonsen, T. M. Jr.

    2010-08-15

    This paper addresses the problem of aftercavity interaction in gyrotrons. The term ''aftercavity interaction'' is used for the cyclotron resonance interaction between electrons in a spent beam exiting the microwave cavity and traveling electromagnetic waves propagating from the cavity exit into the output part of a gyrotron. Aftercavity interaction may reduce the interaction efficiency by several percent and spoil the energy distribution of spent electrons, thus reducing the possibility of efficient utilization of depressed collectors. We have used a simple theory to find conditions resulting in the reduction of this effect. In particular, we have shown that both the axial waveguide wall profile and magnetic field distribution should be modified in order to weaken the effect of aftercavity interaction. We verified results of our simple analysis with advanced simulations and demonstrated that they are in good agreement. Result of these studies can be beneficial for the gyrotron efficiency enhancement.

  9. Field Formation in the Interaction Space of Gyrotrons

    NASA Astrophysics Data System (ADS)

    Nusinovich, Gregory S.; Dumbrajs, Olgierd

    2016-01-01

    For gyrotron applications in plasma installations, one of the most important factors is the gyrotron efficiency. To maximize the interaction efficiency, it is necessary not only to optimize such operating parameters as the magnetic field, beam voltage, and current but also the axial profile of the electromagnetic (EM) field in the interaction space. The present paper describes a study of the effect of the profile of an irregular waveguide serving as a resonator on the axial structure of the EM field. Specific attention is paid to the profile of the uptaper connecting the regular part of a resonator to the output waveguide. Conditions of applicability of the nonuniform string equation, which is widely used in gyrotron designs for finding the axial structure of the EM field, are discussed. Also discussed are the occurrence of reflections from a smooth uptaper and the analogy between the nonuniform string equation and the stationary Schrodinger equation.

  10. Design and development of mode launcher for high frequency Gyrotron

    NASA Astrophysics Data System (ADS)

    Alaria, Mukesh Kumar; Sinha, A. K.; Khatun, H.

    2016-03-01

    In this paper, we describe the design and development of helical cut smooth wall mode launcher for high frequency and high power Gyrotron. A Vlasov-type helical cut mode launcher for converting TE22,6 mode to a Gaussian mode has been designed for 120 GHz, 1 MW Gyrotron. The initial design of mode launcher has been optimized using LOT/SURF-3D software. The mode launcher diameter and length are optimized considering the minimum return loss and the minimum insertion loss by using CST microwave studio. The return loss (S11) and insertion loss (S21) performance of helical cut smooth wall mode launcher have been obtained using CST-Microwave Studio. The fabrication of Vlasov-type helical cut mode launcher for 120 GHz Gyrotron has also been carried out.

  11. The Multiple Gyrotron System on the DIII-D Tokamak

    NASA Astrophysics Data System (ADS)

    Lohr, John; Cengher, Mirela; Doane, John L.; Gorelov, Yuri A.; Moeller, Charles P.; Ponce, Dan; Prater, Ron

    2011-03-01

    The electron cyclotron heating and current drive complex on the DIII-D tokamak presently comprises six gyrotrons injecting rf power from the low field side at 110 GHz, the 2 f ce resonance at the center of the vacuum chamber. Typical injected rf power is 600-650 kW per gyrotron. The launched rf can be directed over ±20° toroidally to create both co- and counter-current drive and scanned over 40° poloidally to permit the injected rf beams to intersect, and be absorbed at, the second harmonic resonance anywhere in the tokamak upper half plane. The elliptical polarization is controlled so that the desired extraordinary or ordinary modes are excited for any injection geometry. The maximum injected energy on a single plasma shot has been 16.6 MJ for six gyrotrons injecting a total of 3.4 MW for 5 seconds.

  12. Development of high-power gyrotrons with gradually tapered cavity

    SciTech Connect

    Lei Chaojun; Yu Sheng; Niu Xinjian; Liu Yinghui; Li Hongfu; Li Xiang

    2012-12-15

    In high power gyrotrons, the parasitic modes coupled with the operating mode cannot be avoided in the beam-wave interaction. These parasitic modes will decrease the efficiency of the gyrotrons. The purity of the operating mode affected by different tapers should be carefully studied. The steady-state self-consistent nonlinear theory for gyrotron with gradually tapered cavity is developed in this paper. A steady-state calculation code including 'cold cavity' and 'hot cavity' is designed. By comparison, a time-domain model analysis of gyrotron operation is also studied by particle-in-cell (PIC). It is found that the tapers of gyrotron have different influences on the modes coupling between the operating mode and the parasitic modes. During the study, an example of 94 GHz gyrotron with pure operating mode TE{sub 03} has been designed. The purity of the operating mode in the optimized cavity is up to -77 dB, and in output waveguide of the cavity is up to -76 dB. At the same time, the beam-wave interaction in the designed cavity has been simulated, too. An output power of 120 kW, corresponding to 41.6% efficiency and an oscillation frequency of 94.099 GHz have been achieved with a 50 kV, 6 A helical electron beam at a guiding magnetic field of 3.5485 T. The results show that the power in spurious modes of the optimized cavity may be kept far below than that of the traditional tapered cavity.

  13. Phase locking and bandwidth in a gyrotron oscillator

    NASA Technical Reports Server (NTRS)

    Latham, P. E.; Granatstein, V. L.; Carmel, Y.

    1993-01-01

    For imaging radar and for satellite and space communication (e.g. NASA's deep space network), it is important that the bandwidth be as large as possible. Here we derive a formalism for computing the phase locking bandwidth that can be achieved in a gyrotron oscillator while varying the beam voltage. As an example, a second harmonic TE02/03 gyrotron is considered. For this device, the effective bandwidth can be increased by a factor of about 3 compared with the fixed voltage case by allowing the beam voltage to change together with the input locking signal.

  14. Mode switching in a gyrotron with azimuthally corrugated resonator.

    PubMed

    Nusinovich, G S; Sinitsyn, O V; Antonsen, T M

    2007-05-18

    The operation of a gyrotron having a cylindrical resonator with an azimuthally corrugated wall is analyzed. In such a device, wall corrugation cancels the degeneracy of the modes with azimuthally standing patterns. The coupling between these modes depends on the radius of electron beam. It is shown that such a gyrotron can be easily switched from one mode to another. When the switching is done with the repetition frequency equal to the rotational frequency of magnetic islands, this sort of operation can be used for suppression of neoclassical tearing modes in large-scale tokamaks and stellarators. PMID:17677705

  15. Mode Switching in a Gyrotron with Azimuthally Corrugated Resonator

    SciTech Connect

    Nusinovich, G. S.; Sinitsyn, O. V.; Antonsen, T. M. Jr.

    2007-05-18

    The operation of a gyrotron having a cylindrical resonator with an azimuthally corrugated wall is analyzed. In such a device, wall corrugation cancels the degeneracy of the modes with azimuthally standing patterns. The coupling between these modes depends on the radius of electron beam. It is shown that such a gyrotron can be easily switched from one mode to another. When the switching is done with the repetition frequency equal to the rotational frequency of magnetic islands, this sort of operation can be used for suppression of neoclassical tearing modes in large-scale tokamaks and stellarators.

  16. Analysis of the harmonic gyrotron traveling wave amplifier

    NASA Technical Reports Server (NTRS)

    Kuo, S. P.; Kuo, S. C.; Cheo, B. R.; Lee, M. C.

    1986-01-01

    A single nonlinear differential equation is derived for describing the spatial evolution of the wave field in a gyrotron amplifier on the cylindrical guide geometry. The equation is then used to determine the efficiencies and the optimized interaction lengths for gyrotron operated with TE sub N1 modes at the N-th cyclotron harmonic. The equation offers a significant advantage in simplifying numerical work in comparison with the brute force particle simulation approach. The efficiencies of the harmonic operations by using a hollow beam decrease quickly with increasing harmonic number, but are enhanced by using an axis-encircling beam instead.

  17. Designing A Mode Converter For Use With A Gyrotron

    NASA Technical Reports Server (NTRS)

    Hoppe, Daniel J.

    1995-01-01

    Report describes process of designing corrugated, circular-cross-section length of waveguide converting input electromagnetic radiation at frequency of 34.5 GHz in TM(11) mode to output radiation in HE(11) mode. TM(11)-mode input radiation supplied by gyrotron generating continuous-wave power of 200 kW at 34.5 GHz in TE(01) mode followed by TE(01)-to-TM(11) mode converter. Together, gyrotron and mode converters constitute prototype high-power transmitter for long-distance free-space communication.

  18. NBS-LASL cw microtron

    SciTech Connect

    Penner, S.; Cutler, R.I.; Debenham, D.H.

    1980-01-01

    The NBS-LASL racetrack microtron (RIM) is a joint research project of the National Bureau of Standards and the Los Alamos Scientific Laboratory. The project goals are to determine the feasibility of, and develop the necessary technology for building high-energy, high-current, continuous-beam (cw) electron accelerators using beam recirculation and room-temperature rf accelerating structures. To achieve these goals, a demonstration accelerator will be designed, constructed, and tested. Parameters of the demonstration RIM are: injection energy - 5 MEV; energy gain per pass -12 MeV; number of passes - 15; final beam energy - 185 MeV; maximum current 550 ..mu..A. One 450 kW cw klystron operating at 2380 MHz will supply rf power to both the injector linac and the main accelerating section of the RTM. The disk and washer standing wave rf structure being developed at LASL will be used. SUPERFISH calculations indicate that an effective shunt impedance (ZT) of about 100 M..cap omega../m can be obtained. Thus, rf power dissipation of 25 kW/m results in an energy gain of more than 1.5 MeV/m. Accelerators of this type should be attractive for many applications. At beam energies above about 50 MeV, an RTM should be considerably cheaper to build and operate than a conventional pulsed rf linac of the same maximum energy and time-average beam power. In addition, the RTM provides superior beam quality and a continuous beam which is essential for nuclear physics experiments requiring time-coincidence measurements between emitted particles.

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

    SciTech Connect

    Harris, T.E.

    1991-10-01

    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.

  20. Gyrotron experiments employing a field emission array cathode

    SciTech Connect

    Garven, M.; Cooke, S.J.; Cross, A.W.; Phelps, A.D.R.; Spark, S.N.

    1995-12-31

    The design and operation of a field emission array (FEA) cathode for a millimeter wave gyrotron are presented. The FEA chip employed achieved 10mA reproducibly while operating in the environment of a gyrotron, namely in a vacuum of 1 {times} 10{sup {minus}8} mbar at voltages of up to 40kV. New methods are presented of mounting such FEA chips involving the shielding of the micron devices from voltages of up to 40kV, as experienced in a microwave device. The design parameters of the FEA gun were similar to those of a magnetron injection gun with cathode radius 12.5mm and slope angle 4{degree}. An electron beam current of up to 100mA was achievable from the FEA gyrotron cathode. An electrically isolated, fiber-optic, 10-channel control unit was developed to allow individual control of each chip. Electron beam powers of {approximately} 1kW were measured from the FEA cathode. To obtain oscillation, cavity inserts were employed in the electron beam-microwave interaction region to increase the cavity quality factor. Results are presented which verify the gyrotron interaction from the novel FEA cathode.

  1. Study of Cavity and Output Window for High Power Gyrotron

    NASA Astrophysics Data System (ADS)

    Alaria, M. K.; Mukherjee, P.; Das, S.; Sinha, A. K.

    2011-02-01

    In this paper Eigen mode analysis has been carried out using Ansoft HFSS for high frequency 42, 120 and 140 GHz Gyrotron cavity. The design of RF window for 42 GHz, 200 kW Gyrotron has also been carried out using the Ansoft HFSS and CST microwave studio. In 42 GHz gyrotron double disc of diameter 85 mm and thickness 3.2 mm sapphire window and spacing (Coolant FC-75) of discs 2.5 mm has been used in the simulation. The return loss (S11) and transmission loss (S21) of the 42 GHz gyrotron window have been found -47.3 and -0.04 dB, respectively. The return loss and transmission loss of the S-band single disc sapphire window have also been found -27.3 and -0.07 dB, respectively at cylindrical waveguide length 33 mm. The simulated result has been validated through experimental results for pill-box S-band sapphire window.

  2. Gyrotron Frequency Stabilization by a Weak Reflected Wave

    NASA Astrophysics Data System (ADS)

    Glyavin, M. Yu.; Denisov, G. G.; Kulygin, M. L.; Mel'nikova, M. M.; Novozhilova, Yu. V.; Ryskin, N. M.

    2016-02-01

    The possibility of reducing the radiation frequency fluctuations by a factor of 3-5 using a nonresonant or highly resonant weakly reflecting load for the gyrotrons employed in controlled-fusion facilities is shown. The ranges of system parameters where the frequency stabilization is most effective were identified both analytically and numerically.

  3. High Efficiency Mode Converter for Low-Frequency Gyrotron

    NASA Astrophysics Data System (ADS)

    Minami, Ryutaro; Kariya, Tsuyoshi; Imai, Tsuyoshi; Mitsunaka, Yoshika; Sakamoto, Keishi

    2011-03-01

    A high efficiency quasi-optical (QO) mode converter for high-power, low-frequency gyrotron have been designed and tested. For low-frequency gyrotrons, the scales of the mode converter are comparatively small on the wavelength scale, thus causing significant diffraction losses. Over-1 MW power gyrotron with TE8,3 cavity at 28 GHz have been developed, which has a high efficiency mode converter designed by the use of numerical methods for launcher optimization. This calculation is sufficiently optimized to maximize the fractional Gaussian content of the far field. The total transmission efficiency from the mode converter to output window is 94.7%. For the experimental result of first tube, the output power of more than 1 MW has been obtained with about 40% efficiency and output burn pattern agrees fairly with the calculated profiles, which imply the design appropriateness. Besides, the frequency dependence for diffraction loss is discussed, and these results give the guiding design principle of the mode converter for high-power, low-frequency and long-pulse gyrotrons.

  4. The DIII-D ECH multiple gyrotron control system

    SciTech Connect

    Ponce, D.; Lohr, J.; Tooker, J.F.; Cary, W.P.; Harris, T.E.

    1997-11-01

    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.

  5. System Development and Performance Testing of a W-Band Gyrotron

    NASA Astrophysics Data System (ADS)

    Kim, Sung Gug; Sawant, Ashwini; Lee, Ingeun; Kim, Dongsung; Choe, MunSeok; Won, Jong-Hyo; Kim, Jungho; So, Joonho; Jang, Won; Choi, EunMi

    2016-03-01

    A high-power W-band gyrotron has been designed and performance tested in Korea, with an output power in the range of tens of kilowatts. The gyrotron consists of a diode-type electron gun operating at 40 kV, a TE6,2 mode interaction cavity, and a mode converter for producing a highly Gaussian output mode beam. Presented here are the detailed component design procedure and the experimental results of the gyrotron's performance evaluation. A maximum power of 62 kW was achieved with an efficiency of 22 %, and a highly Gaussian output beam was observed. The gyrotron's output beam is analyzed, and its transmission through an oversized waveguide is discussed. This gyrotron is the first gyrotron developed in Korea with high power greater than 10 kW and high frequency greater than 90 GHz.

  6. Klystron-like cavity with mode transformation for high-harmonic terahertz gyrotrons

    NASA Astrophysics Data System (ADS)

    Bandurkin, I. V.; Kalynov, Yu. K.; Savilov, A. V.

    2013-01-01

    A novel cavity scheme of a gyrotron is proposed and investigated. As it provides low Ohmic losses and high mode selectivity, it can be especially prospective for realization in gyrotrons operating in the THz frequency range. Numerical simulations show that it allows three-fold increase in the efficiency of the low-relativistic 500 GHz fourth-harmonic gyrotron as compared to conventional two-section scheme with modes transformation.

  7. Klystron-like cavity with mode transformation for high-harmonic terahertz gyrotrons

    SciTech Connect

    Bandurkin, I. V.; Kalynov, Yu. K.; Savilov, A. V.

    2013-01-15

    A novel cavity scheme of a gyrotron is proposed and investigated. As it provides low Ohmic losses and high mode selectivity, it can be especially prospective for realization in gyrotrons operating in the THz frequency range. Numerical simulations show that it allows three-fold increase in the efficiency of the low-relativistic 500 GHz fourth-harmonic gyrotron as compared to conventional two-section scheme with modes transformation.

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

    SciTech Connect

    Wright, A.L.; Tooker, J.; Allen, J.C.; Cary, W.P.; Harris, T.E.

    1995-10-01

    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.

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

    NASA Astrophysics Data System (ADS)

    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.

  10. Subterahertz gyrotron developments for collective Thomson scattering in LHD.

    PubMed

    Notake, T; Saito, T; Tatematsu, Y; Kubo, S; Shimozuma, T; Tanaka, K; Nishiura, M; Fujii, A; Agusu, La; Ogawa, I; Idehara, T

    2008-10-01

    Collective Thomson scattering (CTS) is expected to provide the spatially resolved velocity distribution functions of not only thermal and tail ions but also alpha particles resulting from fusion reactions. CTS using gyrotrons with frequency higher than the conventional ones used for plasma heating would have advantages to alleviate refraction, cutoff effects, and background electron cyclotron emission noise. Therefore, a high-power pulse gyrotron operating at approximately 400 GHz is being developed for CTS in Large Helical Device (LHD). A single-mode oscillation with a frequency greater than 400 GHz, applying the second-harmonic resonance, was successfully demonstrated in the first stage. At the same time, concrete feasibility study based on ray tracing, scattering spectra, and electron cyclotron emission calculations has been conducted. PMID:19044548

  11. Subterahertz gyrotron developments for collective Thomson scattering in LHD

    SciTech Connect

    Notake, T.; Saito, T.; Tatematsu, Y.; Fujii, A.; Agusu, La; Ogawa, I.; Idehara, T.; Kubo, S.; Shimozuma, T.; Tanaka, K.; Nishiura, M.

    2008-10-15

    Collective Thomson scattering (CTS) is expected to provide the spatially resolved velocity distribution functions of not only thermal and tail ions but also alpha particles resulting from fusion reactions. CTS using gyrotrons with frequency higher than the conventional ones used for plasma heating would have advantages to alleviate refraction, cutoff effects, and background electron cyclotron emission noise. Therefore, a high-power pulse gyrotron operating at approximately 400 GHz is being developed for CTS in Large Helical Device (LHD). A single-mode oscillation with a frequency greater than 400 GHz, applying the second-harmonic resonance, was successfully demonstrated in the first stage. At the same time, concrete feasibility study based on ray tracing, scattering spectra, and electron cyclotron emission calculations has been conducted.

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

    SciTech Connect

    Avramidis, K. A.

    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. Investigations and advanced concepts on gyrotron interaction modeling and simulations

    NASA Astrophysics Data System (ADS)

    Avramidis, K. A.

    2015-12-01

    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.

  14. A 670 GHz gyrotron with record power and efficiency

    NASA Astrophysics Data System (ADS)

    Glyavin, M. Yu.; Luchinin, A. G.; Nusinovich, G. S.; Rodgers, J.; Kashyn, D. G.; Romero-Talamas, C. A.; Pu, R.

    2012-10-01

    A 670 GHz gyrotron with record power and efficiency has been developed in joint experiments of the Institute of Applied Physics, Russian Academy of Sciences (Nizhny Novgord, Russia), and the University of Maryland (USA) teams. The magnetic field of 27-28 T required for operation at the 670 GHz at the fundamental cyclotron resonance is produced by a pulsed solenoid. The pulse duration of the magnetic field is several milliseconds. A gyrotron is driven by a 70 kV, 15 A electron beam, so the beam power is on the order of 1 MW in 10-20 ms pulses. The ratio of the orbital to axial electron velocity components is in the range of 1.2-1.3. The gyrotron is designed to operate in the TE31,8-mode. Operation in a so high-order mode results in relatively low ohmic losses (less than 10% of the radiated power). Achieved power of the outgoing radiation (210 kW) and corresponding efficiency (about 20%) represent record numbers for high-power sources of sub-THz radiation.

  15. Effect of velocity spread on operation of high power gyrotrons

    SciTech Connect

    Levush, B.; Cai, S.Y.; Antonsen, T.M. Jr.; Guss, W.C.; Basten, M.A.; Kreischer, K.E.; Temkin, R.

    1995-12-31

    The effect of velocity spread on the operation of 140 GHz gyrotrons has been studied. The performance of two cavities, with low and high Q, has been examined experimentally and theoretically. The simulation code MAGY was modified to include the measured velocity distribution function and the measured pitch angle in order to compare the measured efficiencies with the predicted efficiencies. Based on measurements, the inferred velocity spread at a beam current of 40 A is given by {l_angle}{delta}{upsilon}{sub {perpendicular}}/{upsilon}{sub {perpendicular}}{r_angle}{sub RMS} = 15%. Simulations with this spread produced efficiencies lower than those measured. However, it was found that assuming {l_angle}{delta}{upsilon}{sub {perpendicular}}/{upsilon}{sub {perpendicular}}{r_angle}{sub RMS} = 10% for 40 A current and using the experimentally determined dependence of the spread on the current the calculated efficiencies agree well with the measured efficiencies for the low Q cavity. The efficiency of the low Q gyrotron at 40 A beam current is only 27%. For the same beam current and velocity spread the efficiency of the high Q gyrotron was predicted to be 40% which agrees well with the measured efficiency of 39%.

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

    NASA Astrophysics Data System (ADS)

    Kreischer, K. E.

    1982-01-01

    A program which calculates the linear characteristics of a gyrotron is presented. 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; and (4) doing the above for any axial RF field profile.

  17. Fast frequency-step-tunable gyrotrons for plasma heating and fusion diagnostics

    SciTech Connect

    Dumbrajs, O.; Heikkinen, J.

    1994-11-01

    Usefulness of frequency tunable sources for plasma heating and fusion diagnostics is studied. Applicability of fast frequency-step-tunable gyrotrons for these purposes is examined. A gyrotron based on a coaxial cavity with impedance rod is considered as an example.

  18. CW CO2 Laser Induced Chemical Reactions

    NASA Astrophysics Data System (ADS)

    Pola, Joseph

    1989-05-01

    CW CO2 laser driven reactions between sulfur hexafluoride and carbon oxide, carbon suboxide, carbonyl sulfide and carbon disulfide proceed at subatmospheric pressures and yield fluorinated carbon compounds and sulfur tetrafluoride. CW CO2 laser driven reactions of organic compounds in the presence of energy-conveying sulfur hexafluoride show reaction course different from that normally observed due to elimination of reactor hot surface effects. The examples concern the decomposition of polychlorohydrocarbons, 2-nitropropane, tert.-butylamine, allyl chloride, spirohexane, isobornyl acetate and the oxidation of haloolefins. CW CO2 laser induced fragmentation of 1-methyl-l-silacyclobutanes and 4-silaspiro(3.4)octane in the presence of sulfur hexafluoride is an effective way for preparation and deposition of stable organosilicon polymers.

  19. GYROTRON POWER BALANCE BASED ON CALORIMETRIC MEASUREMENTS IN THE DIII-D ECH SYSTEM

    SciTech Connect

    GORELOV,I.A; LOHR,J.M; BAITY,JR.,F.W; CAHALAN,P; CALLIS,R.W; PONCE,D; CHIU,H.K

    2003-10-01

    OAK-B135 A powerful microwave system operating at the second harmonic of the electron cyclotron frequency on the DIII-D tokamak was upgraded up to six assemblies of 110 GHz gyrotrons in 2003. three Gycom gyrotrons nominally generate 750 kW for 2 s pulses, with the pulse length limit resulting from the peak temperature allowed on the boron nitride rf output window. Three Communications and Power Industries (CPI) gyrotrons with diamond windows have been recently installed and have been tested to 0.9-1.0 MW for 5 s pulses. Heat loading on internal parts of the gyrotrons, the matching optics unit and the dummy loads is measured calorimetrically. This paper discusses the calorimetry system and calorimetric measurements of gyrotron performance.

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

    NASA Astrophysics Data System (ADS)

    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.

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

    SciTech Connect

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

    2015-06-29

    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. Possibilities for Continuous Frequency Tuning in Terahertz Gyrotrons with Nontunable Electrodynamic Systems

    NASA Astrophysics Data System (ADS)

    Bratman, V. L.; Savilov, A. V.; Chang, T. H.

    2016-02-01

    Large ohmic losses in the cavities of terahertz gyrotrons may lead to the overlapping of the axial mode spectra. In a number of gyrotron experiments, this effect has been used to provide a fairly broadband frequency tuning by changing appropriately the operating magnetic field and/or accelerating voltage of the gyrotron. Similar to the systems with nonfixed axial structure of the RF electromagnetic field and low diffraction quality, which are due to weak reflections of the operating wave from the collector end of the electrodynamic system, this changing leads to a monotonic change in the axial index of the operating wave and transition from the gyrotron regime to the gyro-BWO regime. According to a theoretical comparison of these two methods performed on the basis of generalization of self-consistent gyrotron equations with allowance for variations in the axial electron momenta, low-reflection systems can provide a higher efficiency and monotonicity of the frequency tuning.

  3. INFRARED MONITORING OF 110GHz GYROTRON WINDOWS AT DIII-D

    SciTech Connect

    Y. GORELOV; J. LOHR; R.W. CALLIS; D. PONCE

    2002-05-01

    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 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.

  4. Design study of a 0.4 THz 100 kW pulsed gyrotron

    SciTech Connect

    Choi, E.M.

    2011-07-01

    We present a status of development of a 0.4 THz, 100 kW pulsed gyrotron at UNIST 0.4 THz, 100 kW gyrotron is currently under design for a remote radioactive material detection. A magnetic injection gun (MIG) is used for the electron gun with a beam voltage of 70 kV and beam current of 10 A with a pulse duration of 10 usec. A second harmonic cavity for the gyrotron interaction is considered for the high power THz gyrotron. Numerical optimization of the electron gun design and the cavity is performed in the study. In this paper, we briefly report the design study of the gyrotron. (author)

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

    SciTech Connect

    Hou, Shenyong; Yu, Sheng; Li, Hongfu

    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.

  6. Cw operation of the FMIT RFQ accelerator

    SciTech Connect

    Cornelius, W.D.

    1985-01-01

    Recently, we have achieved reliable cw operation of the Fusion Materials Irradiation Test (FMIT) radio-frequency quadrupole (RFQ) accelerator. In addition to the operational experiences in achieving this status, some of the modifications of the vacuum system, cooling system, and rf structure are discussed. Preliminary beam-characterization results are presented. 10 refs., 8 figs.

  7. CW arc-lamp-pumped alexandrite lasers

    SciTech Connect

    Samelson, H.; Walling, J.C.; Wernikowski, T.; Harter, D.J.

    1988-06-01

    The performance characteristics of arc-lamp- (Xe and Hg) pumped, CW alexandrite lasers are described in detail. The modes of operation considered are free running, tuned, and repetitively Q-switched. The experimental arrangement and apparatus are also outlined. The experimental results are discussed in terms of a steady-state model, and the areas of agreement and difficulty are pointed out.

  8. A CW Gunn Diode Switching Element.

    ERIC Educational Resources Information Center

    Hurtado, Marco; Rosenbaum, Fred J.

    As part of a study of the application of communication satellites to educational development, certain technical aspects of such a system were examined. A current controlled bistable switching element using a CW Gunn diode is reported on here. With modest circuits switching rates of the order of 10 MHz have been obtained. Switching is initiated by…

  9. High power 303 GHz gyrotron for CTS in LHD

    NASA Astrophysics Data System (ADS)

    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.

  10. Nonlinearly driven oscillations in the gyrotron traveling-wave amplifier

    SciTech Connect

    Chiu, C. C.; Pao, K. F.; Yan, Y. C.; Chu, K. R.; Barnett, L. R.; Luhmann, N. C. Jr.

    2008-12-15

    By delivering unprecedented power and gain, the gyrotron traveling-wave amplifier (gyro-TWT) offers great promise for advanced millimeter wave radars. However, the underlying physics of this complex nonlinear system is yet to be fully elucidated. Here, we report a new phenomenon in the form of nonlinearly driven oscillations. A zero-drive stable gyro-TWT is shown to be susceptible to a considerably reduced dynamic range at the band edge, followed by a sudden transition into driven oscillations and then a hysteresis effect. An analysis of this unexpected behavior and its physical interpretation are presented.

  11. Improved Design of Beam Tunnel for 42 GHz Gyrotron

    NASA Astrophysics Data System (ADS)

    Singh, Udaybir; Kumar, Nitin; Purohit, L. P.; Sinha, A. K.

    2011-04-01

    In gyrotron, there is the chance of generation and excitation of unwanted RF modes (parasite oscillations). These modes may interact with electron beam and consequently degrade the beam quality. This paper presents the improved design of the beam tunnel to reduce the parasite oscillations and the effect of beam tunnel geometry on the electron beam parameters. The design optimization of the beam tunnel has been done with the help of 3-D simulation software CST-Microwave Studio and the effect of beam tunnel geometry on the electron beam parameters has been analyzed by EGUN code.

  12. Frequency multiplied harmonic gyrotron-traveling-wave-tube amplifier

    SciTech Connect

    Choi, J.J.; Ganguly, A.K.; Armstrong, C.M. )

    1994-06-01

    Numerical simulations of a [ital W]-band two-stage tapered, frequency multiplied gyrotron- traveling-wave-tube amplifier are reported. Unlike conventional harmonic gyrodevices, a drive signal at the fundamental harmonic frequency is injected in the first stage for beam modulation, and amplified output radiation is extracted from the third harmonic cyclotron resonance interaction. Numerical results show that broadband millimeter wave radiation is obtained with an efficiency of 10%--15%, a gain of [similar to]30 dB, and an instantaneous bandwidth of [similar to]10% at a center frequency of 95 GHz for [Delta][ital v][sub [ital z

  13. Characterization of stationary and nonstationary behavior in gyrotron oscillators.

    PubMed

    Chang, T H; Chen, S H; Barnett, L R; Chu, K R

    2001-08-01

    The transition from the stationary state to a sequence of nonstationary states in the gyromonotron oscillator is experimentally characterized for the first time. We have also demonstrated the stationary operation of a gyrotron backward-wave oscillator at a beam current far in excess of the generally predicted nonstationary threshold. This difference in nonlinear behavior has been investigated and shown to be fundamental with a comparative analysis of the feedback mechanisms, energy deposition profiles, and field shaping processes involved in these two types of oscillations. PMID:11497832

  14. Mode competition effects in free electron lasers and gyrotrons

    SciTech Connect

    Levush, B.; Antonsen, T.M.

    1990-01-01

    In many cases in high frequency, high power coherent radiation generators (such as free electron laser and gyrotrons) the linear gain is positive for many modes and therefore these modes will grow and compete for the beam energy. The questions related to mode competition, coherency of the radiation and maximization of the interaction efficiency are of great importance. To address these issues simple multi-mode models have been formulated. This paper is a short review of the recent results from both simulation and analyses of these models. 3 figs.

  15. Silicon with extra low losses for megawatt output gyrotron windows

    SciTech Connect

    Parshin, V.V.; Heidinger, R.; Andreev, B.A.; Gusev, A.V.; Shmagin, V.B.

    1995-12-31

    The dielectric losses are investigated in high-purity grades of silicon doped by different ways to reduce their mm-wave absorption. The results of the dielectric loss tangent measurements are given for the frequency range of 30 - 330 GHz and for the temperature interval 30-330K. The obtained data are discussed together with the thermophysical properties with respect to the power transmission capabilitity of edge-cooled output windows for high power gyrotrons and the potential of the special silicon grades are demonstrated for these applications.

  16. Generation of high power sub-terahertz radiation from a gyrotron with second harmonic oscillation

    SciTech Connect

    Saito, Teruo; Yamada, Naoki; Ikeuti, Shinji; Tatematsu, Yoshinori; Ikeda, Ryosuke; Ogawa, Isamu; Idehara, Toshitaka; Ogasawara, Shinya; Manuilov, Vladimir N.; Shimozuma, Takashi; Kubo, Shin; Nishiura, Masaki; Tanaka, Kenji; Kawahata, Kazuo

    2012-06-15

    New power records of second harmonic gyrotron oscillation have been demonstrated in the sub-THz band. The first step gyrotron of demountable type had succeeded in oscillation with power more than 50 kW at 350 GHz and nearly 40 kW at 390 GHz [T. Notake et al., Phys. Rev. Lett. 103, 225002 (2009)]. Then, the second step gyrotron of sealed-off type was manufactured. A cavity mode was carefully selected to avoid mode competition with a neighboring fundamental harmonic mode. Matching of the selected mode with the electron gun was also circumspectly considered. The second step gyrotron has attained higher power radiation than the first gyrotron. The maximum single mode power was 62 kW at 388 GHz. Then, the electron gun was modified for use of a different cavity mode with a higher coupling coefficient than that for the 62 kW mode. The new mode proved single mode oscillation power of 83 kW at about 389 GHz. These results are new second-harmonic-oscillation power records for sub-THz gyrotrons. The present study constitutes foundations of development of high power second harmonic sub-THz gyrotron for application to collective Thomson scattering measurement on fusion plasmas, especially on high-density plasmas such as those produced in LHD [N. Ohyabu et al., Phys. Rev. Lett. 97, 055002 (2006)]. This paper reports the design consideration to realize high power single mode gyrotron oscillation at second harmonic and the examination of oscillation characteristics of the gyrotron.

  17. Preliminary design of a magnetron injection gun for a 670 GHz gyrotron

    NASA Astrophysics Data System (ADS)

    Kesar, Amit S.; Pu, Ruifeng; Nusinovich, Gregory S.; Granatstein, Victor L.

    2010-11-01

    At present, our research team is working on the design of a 300 kW, 670 GHz gyrotron with a pulsed solenoid. The gyrotron will operate at the fundamental cyclotron resonance. The pulsed solenoid will provide magnetic fields in the range of 27-28 T. Design of a magnetron-type electron gun for such a gyrotron is done by using available numerical codes EGN2W and MICHELLE. Magnetic compression of a beam in the region between the gun and a resonator is about 100; the beam voltage and current are 70 kV and 15 A, respectively. Simulation results will be presented.

  18. Nonlinear theory for a terahertz gyrotron with a special cross-section interaction cavity

    SciTech Connect

    Yuan, Xuesong; Han Yu; Yan Yang; Lan Ying

    2012-05-15

    The fully numerical nonlinear theory for a gyrotron with a special cross-section interaction cavity has been developed in this paper. In this theory, the analytical solution to different modes in the special cross-section interaction cavity is replaced by the numerical solution based on electromagnetic simulation results. A 0.4 THz third harmonic gyrotron with an azimuthally corrugated interaction cavity has been investigated by using this theory and simulation results show that this approach has a significant advantage of developing high harmonic terahertz gyrotrons.

  19. Note: A 95 GHz mid-power gyrotron for medical applications measurements.

    PubMed

    Pilossof, Moritz; Einat, Moshe

    2015-01-01

    A mid-power 95 GHz gyrotron was built and used for measuring insertion loss of biological tissue. The gyrotron is a compact table-top device that allows convenient measurements in a biological setup. It operates at the fundamental harmonic with TE02 circular mode. A mode converter is used to obtain TE10 rectangular mode in standard WR10 components. Using this gyrotron, beef tissue insertion loss was measured to be about 7-8 dB per millimeter. PMID:25638140

  20. HIGH POWER LONG PULSE PERFORMANCE OF THE DIII-D GYROTRON INSTALLATION

    SciTech Connect

    J. LOHR; Y.A. GORELOV; R.W. CALLIS; H.J. GRUNLOH; J.J. PEAVY; R.I. PINSKER; D. PONCE; R. PRATER; R.A. ELLIS,III

    2002-05-01

    At DIII-D, five 110 GHz gyrotrons are operating routinely for 2.0 s pulses at generated power levels {ge}750 kW per gyrotron. A sixth gyrotron is being installed, which should bring the generated power level to >4 MW and the injected power to about 3.0 MW. The output power now can be modulated by the plasma control system to fix T{sub e} at a desired value. The system is being used as a tool for control of current diffusion, for current profile control and other experiments leading to advanced tokamak operation.

  1. A 100 MV cryomodule for CW operation

    SciTech Connect

    Charles Reece

    2005-07-10

    A cryomodule designed for high-gradient CW operation has been built at Jefferson Lab. The Renascence cryomodule is the final prototype of a design for use in the 12 GeV CEBAF upgrade. The module uses eight 7-cell 1497 MHz cavities to be individually powered by 13 kW klystrons. Specifications call for providing >109 MV CW with < 250 W of dynamic heat at 2.07 K. The module incorporates a new generation of tuners and higher power input waveguides. A mixture of the new HG and LL cavity shapes are used. A new high thermal conductivity RF feedthrough has been developed and used on the 32 HOM coupler probes of Renascence. The cryomodule assembly is complete. Testing is to begin late June. Design features and initial test data will be presented.

  2. 137-GHz gyrotron diagnostic for instability studies in Tara

    SciTech Connect

    Machuzak, J.S.; Woskoboinikow, P.; Mulligan, W.J.; Cohn, D.R.; Gerver, M.; Guss, W.; Mauel, M.; Post, R.S.; Temkin, R.J.

    1986-08-01

    A narrow linewidth (<100 kHz), 1-kW, 137-GHz gyrotron and an efficient TE/sub 03/ to TE/sub 11/ cylindrical waveguide mode converter set (>97% TE/sub 11/ mode output) have been built for collective Thomson scattering diagnostics. The main goal will be to study instability driven ion density fluctuations in the Tara plug such as the drift cyclotron loss cone (DCLC), the axial loss cone (ALC), harmonics of the DCLC and ALC, and the ion two-stream instability. The heterodyne receiver and signal optics have been installed on Tara. Background electron cyclotron emission (ECE) at 139 +- 1.5 GHz after electron cyclotron resonance heating (ECRH) in the Tara plug corresponded to equivalent blackbody temperatures of 453 and 70 eV for extraordinary and ordinary emission, respectively. The well-collimated receiver field of view completely through the Tara plug has allowed for excellent polarization discrimination of the ECE. The high-power capability of this gyrotron will allow weak fluctuation levels (n-italic-tilde/n-italic<10/sup -6/) to be detected above this background during ECRH in the plugs.

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

    NASA Astrophysics Data System (ADS)

    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.

  4. New results and applications for the quasioptical gyrotron

    NASA Astrophysics Data System (ADS)

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

    1993-02-01

    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 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.

  5. New results and applications for the quasioptical gyrotron

    NASA Astrophysics Data System (ADS)

    Fliflet, Arne W.; Fischer, Richard P.; Manheimer, Wallace M.

    1993-07-01

    The quasi-optical 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 quasi-optical 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 percent have been obtained by increasing the frequency detuning of the operating mode. An overall efficiency of 30 percent 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 percent. The high circulating power in the QOG resonator is currently being considered for use as an electromagnetic wiggler for compact infrared FELs. The QOG is also promising as a source for an active sensor of upper atmosphere trace impurities.

  6. Generalized Radiation Boundary Conditions in Gyrotron Oscillator Modeling

    NASA Astrophysics Data System (ADS)

    Alberti, S.; Tran, T. M.; Brunner, S.; Braunmueller, F.; Genoud, J.; Hogge, J.-Ph.; Tran, M. Q.

    2015-11-01

    A numerical procedure to implement a frequency-independent generalized non-reflecting radiation boundary conditions, GNRBC, based on the Laplace Transform, is described in details and tested successfully on a simple 2 frequency test problem. In the case of non-stationary regimes occurring in gyrotron oscillators, it is shown that the reflection at frequencies significantly separated from the carrier frequency can be effectively suppressed by this method. A detailed analysis shows that this numerical approach can be consistently used only for models in which there is no assumed separation of time scales between the RF field envelope time-evolution and the electron time of flight across the interaction region. The GNRBC has been implemented in a nonlinear time-dependent self-consistent monomode model, TWANGpic, in which there is no time scale separation since the RF field envelope is updated at each integration time step of the electron motion. The illustration of the effectiveness of the GNRBC is made with TWANGpic on a gyrotron for which extensive theoretical and experimental results have been performed.

  7. Interpretation of the nonlinear mode excitation in the ITER gyrotron

    SciTech Connect

    Nusinovich, G. S.; Sinitsyn, O. V.

    2007-11-15

    This study was motivated by an interesting physical effect observed in experiments with a 1 MW, 170 GHz, continuous-wave gyrotron developed at the Japan Atomic Energy Agency for plasma heating and current drive in ITER [see, e.g., Fusion Eng. Des. 55, issues 2-3 (2001)]. In these experiments, the gyrotron switching from a parasitic mode to the operating one was observed with the increase in external magnetic field in the region of hard self-excitation of the operating mode where it cannot be excited from the noise level in the absence of other modes. Below, the theory describing this effect is developed. The switching mechanism caused by merging and disappearance of two (one stable and another unstable) equilibrium states with nonzero amplitudes of both modes is proposed. It is found that the present theory can correctly interpret experimental results qualitatively, but the lack of experimental data does not let the authors carry out some simulations more adequate to experimental conditions.

  8. A W-band Third Harmonic Gyrotron with an Iris Cavity

    NASA Astrophysics Data System (ADS)

    Sun, Dimin; Chen, Huaibi; Ma, Guowu; Lei, Wenqiang; Chen, Hongbin; Meng, Fanbao

    2014-05-01

    The design and experimental results of a W-band gyrotron operating at the third cyclotron harmonic are presented. The gyrotron is designed to operate at the TE61 mode, which is significantly distinct from competing modes. An iris cavity is employed for the purpose of trapping the third harmonic mode more effectively and lowering its start current. In the experiment, the gyrotron is drived by a triode magnetron injection gun (MIG) which can produce a 45 kV, 3 A electron beam. When maximum axial magnetic field is 1.22 T, a single mode third harmonic gyrotron radiation is observed with the frequency of 94.86 GHz. The maximum output power is 5.5 kW, corresponding to an efficiency of 4%. Another third harmonic mode TE02 is also detected at 88.8 GHz, with maximum output power of 1.5 kW.

  9. Ion Compensation for Space Charge in the Helical Electron Beams of Gyrotrons

    NASA Astrophysics Data System (ADS)

    Manuilov, V. N.; Semenov, V. E.

    2016-06-01

    We solve analytically the problem about ion compensation for the space charge of a helical electron beam in a gyrotron operated in the long-pulse regime. Elementary processes, which take place during ionization of residual gas in the tube under typical pressures of 10-6-10-7 mm Hg, are considered. It is shown that distribution of the space charge is affected mainly by the electrons of the initial beam and slow-moving ions produced by ionization of the residual gas. Steady-state density of ions in the operating space of the gyrotron after the end of the transitional processes is found, as well as the electron density profile in the channel of electron beam transportation. The results obtained allow us to evaluate the pitch-factor variations caused by partial compensations for the potential "sagging" in the gyrotron cavity, thus being useful for analysis of starting currents, efficiency, and mode competition in high-power gyrotrons.

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

    SciTech Connect

    Chaojun, Lei; Sheng, Yu; Hongfu, Li; Yinghui, Liu; Xinjian, Niu; Qixiang, Zhao

    2013-07-15

    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 TE{sub 32,5} 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.

  11. Effect of the thickness of electron beams on the gyrotron efficiency

    SciTech Connect

    Pu Ruifeng; Nusinovich, Gregory S.; Sinitsyn, Oleksandr V.; Antonsen, Thomas M. Jr.

    2010-08-15

    In this paper the effect of the spread in the radii of electron guiding centers on the gyrotron efficiency is studied. First, the analytical theory is developed for describing this effect in gyrotrons operating in regimes of soft and hard self-excitations. Then, study of this effect in a 670 GHz gyrotron is carried out both analytically and numerically with the use of the available nonstationary self-consistent code. Comparison of results demonstrates very reasonable agreement between numerical data and analytical predictions. It was found that in the case of beam injection at the inner peak of the function describing the beam coupling to the wave the spread in electron guiding center radii can be significantly larger than is usually allowed. This fact greatly alleviates the design of electron guns for terahertz-range gyrotrons.

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

    NASA Astrophysics Data System (ADS)

    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.

  13. Increase of Efficiency of Gyrotron by Optimizing Conditions of RF-field Emission

    SciTech Connect

    Kuklin, V. M.; Lapshin, V. I.; Puzyrkov, S. Yu

    2006-01-15

    Dependence of efficiency and output power on parameter which is equal to ratio of total emission power to accumulated energy is considered in simplified model of gyrotron. It is shown that this parameter changes with changing of emission conditions at the generator output, which leads to the change of field distribution inside of gyrotron as well. Behavior of efficiency and output power is introduced in the vicinity of their maximal values.

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

    SciTech Connect

    Samartsev, A.; Gantenbein, G.; Dammertz, G.; Illy, S.; Kern, S.; Leonhardt, W.; Schlaich, A.; Schmid, M.; Thumm, M.

    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)

  15. Influence of emitter ring manufacturing tolerances on electron beam quality of high power gyrotrons

    NASA Astrophysics Data System (ADS)

    Pagonakis, Ioannis Gr.; Illy, Stefan; Thumm, Manfred

    2016-08-01

    A sensitivity analysis of manufacturing imperfections and possible misalignments of the emitter ring in the gyrotron cathode structure on the electron beam quality has been performed. It has been shown that a possible radial displacement of the emitter ring of the order of few tens of microns can cause dramatic effects on the beam quality and therefore the gyrotron operation. Two different design approaches are proposed in order to achieve an electron beam which is less sensitive to manufacturing imperfections.

  16. Scaling calculations for a relativistic gyrotron. Memorandum report, March 1984-March 1985

    SciTech Connect

    Fliflet, A.W.

    1985-07-31

    The relativistic gyrotron is under development as an ultra-high power source of millimeter-wave radiation. The purpose of the present study is to estimate the optimum operating characteristics of gyrotrons based on multi-kiloampere, mega-electron volt electron beams. Gyrotrons with weakly relativistic, moderate-current electron beams have demonstrated very high efficiency and average power at millimeter wavelengths and the possibility of achieving good efficiencies at very high-peak powers is of interest. Compared to other high-power millimeter-wave generators, gyrotrons are relatively insensitive to electron-beam velocity spread and thus appear well suited to device configurations based on high-current pulseline accelerators. The results of this study indicate that the relativistic gyrotron has potential for achieving high efficiency (15-30%) using relativistic electron beams with gamma approx 2-3. Optimum efficiency occurs for short interaction lengths, characterized by 4-8 cyclotron periods. Such short interaction lengths lead to the possibility of very high peak power generation using multi-kiloampere beams: 100-300 MW with a 600 keV beam and about 1 GW with a 1 MeV beam. The output power risetime has been estimated to be a few nanoseconds for a low-Q oscillator at 35 GHz, which implies the gyrotron interaction can be readily investigated using a 20-100 nsec pulseline accelerator.

  17. Optimization of operation of a three-electrode gyrotron with the use of a flow-type calorimeter

    SciTech Connect

    Kharchev, Nikolay K.; Batanov, German M.; Kolik, Leonid V.; Malakhov, Dmitrii V.; Petrov, Aleksandr Ye.; Sarksyan, Karen A.; Skvortsova, Nina N.; Stepakhin, Vladimir D.; Belousov, Vladimir I.; Malygin, Sergei A.; Tai, Yevgenii M.

    2013-01-15

    Results are presented for measurements of microwave power of the Borets-75/0.8 gyrotron with recovery of residual electron energy, which were performed by a flow-type calorimeter. This gyrotron is a part of the ECR plasma heating complex put into operation in 2010 at the L-2M stellarator. The new calorimeter is capable of measuring microwave power up to 0.5 MW. Monitoring of the microwave power makes it possible to control the parameters of the gyrotron power supply unit (its voltage and current) and the magnetic field of the cryomagnet in order to optimize the gyrotron operation and arrive at maximum efficiency.

  18. Optimization of operation of a three-electrode gyrotron with the use of a flow-type calorimeter.

    PubMed

    Kharchev, Nikolay K; Batanov, German M; Kolik, Leonid V; Malakhov, Dmitrii V; Petrov, Aleksandr Ye; Sarksyan, Karen A; Skvortsova, Nina N; Stepakhin, Vladimir D; Belousov, Vladimir I; Malygin, Sergei A; Tai, Yevgenii M

    2013-01-01

    Results are presented for measurements of microwave power of the Borets-75/0.8 gyrotron with recovery of residual electron energy, which were performed by a flow-type calorimeter. This gyrotron is a part of the ECR plasma heating complex put into operation in 2010 at the L-2M stellarator. The new calorimeter is capable of measuring microwave power up to 0.5 MW. Monitoring of the microwave power makes it possible to control the parameters of the gyrotron power supply unit (its voltage and current) and the magnetic field of the cryomagnet in order to optimize the gyrotron operation and arrive at maximum efficiency. PMID:23387650

  19. Diode-pumped CW molecular lasers

    NASA Astrophysics Data System (ADS)

    Wellegehausen, B.; Luhs, W.

    2016-05-01

    First continuous laser oscillation on many lines in the range of 533-635 nm on different transitions of Na2 and Te2 molecules has been obtained, optically pumped with common cw blue emitting InGaN diode lasers operating around 445 and 460 nm. Spectral narrowing of the diode laser is achieved with a beamsplitter and grating setup, allowing use of more than 50 % of the diode power. Operation conditions and properties of the laser systems are presented, and perspectives for the realization of compact low cost molecular lasers are discussed.

  20. Folded waveguide gyrotron traveling-wave-tube amplifier

    SciTech Connect

    Choi, J.J.; Armstrong, C.M.; Ganguly, A.K.; Calise, F.

    1995-03-01

    A compact, low cost gyrotron traveling-wave-tube (gyro-TWT) amplifier capable of producing high-power, broadband, millimeter wave radiation is reported. The interaction circuit is a periodic, magnetic field plane (H plane) bend, transverse folded waveguide employed with a high-power axis-encircling electron beam. Transverse beam modulation and wave amplification in the folded waveguide gyro-TWT are observed in both linear theory and large signal simulations. Calculations from an equivalent circuit model and a three-dimensional electromagnetic code predict a mode coalescing of the first stop-band in a periodic structure. The mode coalescing is verified from experimental measurements. {copyright} {ital 1995} {ital American} {ital Institute} {ital of} {ital Physics}.

  1. Thermal and Structural Analysis of MIG for Gyrotron

    NASA Astrophysics Data System (ADS)

    Singh, Udaybir; Kumar, Anil; Kumar, Nitin; Kumar, Narendra; Raju, R. S.; Purohit, L. P.; Sinha, A. K.

    2011-04-01

    The paper presents the thermal analysis of the Magnetron Injection Gun for 42 GHz, 200 kW gyrotron, which is used to provide a high quality hollow electron beam. The Finite Element Analysis code ANSYS has been used for the thermal and the structural simulation. The thermal analysis of the structure of Magnetron Injection Gun has been carried out to find out the effect of heater temperature required for maintaining more than 1,000°C at cathode emitter surface to get 10 A of beam current. These results have been experimentally verified. The experimental results closely match the ANSYS results. The effect of the radial expansion of the emitter radius on beam quality has also been analyzed.

  2. Design of Cathode Heater Assembly for High Power Gyrotron

    NASA Astrophysics Data System (ADS)

    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. Numerical study of efficiency for a 670 GHz gyrotron

    SciTech Connect

    Pu Ruifeng; Nusinovich, Gregory S.; Sinitsyn, Oleksandr V.; Antonsen, Thomas M. Jr.

    2011-02-15

    In this paper, the results of the efficiency study of a 670 GHz gyrotron operating at TE{sub 31,8}-mode are presented. Calculations are performed by using the self-consistent nonstationary code MAGY. Three cavity configurations were examined. The effects of ohmic losses and electron velocity spread were included in the simulation. The results show that the output efficiency can reach 35% and the velocity spread in the electron beam does not degrade the operation significantly. Furthermore, we verified that the smoothing of the sharp corners for a small tapering angle would reduce mode conversion; the parasitic excitation of neighboring radial modes is less than 1% of the amplitude of the operating mode and the effect on efficiency is small. Lastly, the simulation results show that the after-cavity interaction causes only slight variations in the efficiency.

  4. Liquid state DNP using a 260 GHz high power gyrotron.

    PubMed

    Denysenkov, Vasyl; Prandolini, Mark J; Gafurov, Marat; Sezer, Deniz; Endeward, Burkhard; Prisner, Thomas F

    2010-06-14

    Dynamic nuclear polarization (DNP) at high magnetic fields (9.2 T, 400 MHz (1)H NMR frequency) requires high microwave power sources to achieve saturation of the EPR transitions. Here we describe the first high-field liquid-state DNP results using a high-power gyrotron microwave source (20 W at 260 GHz). A DNP enhancement of -29 on water protons was obtained for an aqueous solution of Fremy's Salt; in comparison the previous highest value was -10 using a solid-state microwave power source (maximum power 45 mW). The increased enhancements are partly due to larger microwave saturation and elevated sample temperature. These experimentally observed DNP enhancements, which by far exceed the predicted values extrapolated from low-field DNP experiments, demonstrate experimentally that DNP is possible in the liquid state also at high magnetic fields. PMID:20461255

  5. Large-orbit gyrotron operation in the terahertz frequency range.

    PubMed

    Bratman, V L; Kalynov, Yu K; Manuilov, V N

    2009-06-19

    Coherent terahertz high-harmonic radiation has been obtained in a gyrotron with an axis-encircling electron beam. An electron-optical system with a cusp gun and a following drift section of adiabatic magnetic compression with an area factor of 3000 provides the formation of an 80-keV/0.7-A beam of gyrating electrons in a wide range of voltages and magnetic fields. Stable single-mode generation with a power of 0.3-1.8 kW in microsecond pulses is detected at four frequencies in the range 0.55-1.00 THz at resonant magnetic fields 10.5-14 T. PMID:19659020

  6. Numerical simulations of a co-harmonic gyrotron

    NASA Astrophysics Data System (ADS)

    Constable, D. A.; Ronald, K.; He, W.; Phelps, A. D. R.; Cross, A. W.; Savilov, A. V.; Bratman, V. L.; Bandurkin, I. V.

    2012-02-01

    A co-harmonic gyrotron, operating simultaneously at the second and fourth harmonics of the electron cyclotron frequency, has been successfully modelled with the particle-in-cell code, Magic 3D. Results show excitation of the TE2,2 and TE4,3 waveguide modes, at frequencies of 37.5 GHz and 75 GHz, respectively, consistent with experimental measurements. The total predicted output power was ˜3 kW. Lengthening of the cut-off output taper has demonstrated an improved confinement of the second harmonic signal, facilitating purer output of the fourth harmonic signal. In this enhanced configuration, the predicted output power of the second harmonic was ˜250 W, while the fourth harmonic was ˜15 W. The system demonstrates the potential for selective fourth harmonic generation, for starting currents which are two orders of magnitude lower than would be required for direct excitation.

  7. Effect of electron-cyclotron resonance plasma heating conditions on the low-frequency modulation of the gyrotron power at the L-2M stellarator

    SciTech Connect

    Batanov, G. M.; Borzosekov, V. D.; Kolik, L. V.; Konchekov, E. M. Malakhov, D. V.; Petelin, M. I.; Petrov, A. E.; Sarksyan, K. A.; Skvortsova, N. N.; Stepakhin, V. D.; Kharchev, N. K.

    2015-08-15

    Low-frequency modulation of the gyrotron power at the L-2M stellarator was studied at different modes of plasma confinement. The plasma was heated at the second harmonic of the electron gyrofrequency. The effect of reflection of gyrotron radiation from the region of electron-cyclotron resonance plasma heating, as well as of backscattering of gyrotron radiation from fluctuations of the plasma density, on the modulation of the gyrotron power was investigated.

  8. Effect of electron-cyclotron resonance plasma heating conditions on the low-frequency modulation of the gyrotron power at the L-2M stellarator

    NASA Astrophysics Data System (ADS)

    Batanov, G. M.; Borzosekov, V. D.; Kolik, L. V.; Konchekov, E. M.; Malakhov, D. V.; Petelin, M. I.; Petrov, A. E.; Sarksyan, K. A.; Skvortsova, N. N.; Stepakhin, V. D.; Kharchev, N. K.

    2015-08-01

    Low-frequency modulation of the gyrotron power at the L-2M stellarator was studied at different modes of plasma confinement. The plasma was heated at the second harmonic of the electron gyrofrequency. The effect of reflection of gyrotron radiation from the region of electron-cyclotron resonance plasma heating, as well as of backscattering of gyrotron radiation from fluctuations of the plasma density, on the modulation of the gyrotron power was investigated.

  9. Dependence of the gyrotron efficiency on the azimuthal index of non-symmetric modes

    SciTech Connect

    Dumbrajs, O.; Nusinovich, G. S.; Antonsen, T. M.

    2014-06-15

    Development of MW-class gyrotrons for future controlled fusion reactors requires careful analysis of the stability of high efficiency operation in very high-order modes. In the present paper, this problem is analyzed in the framework of the non-stationary self-consistent theory of gyrotrons. Two approaches are used: the one based on the wave envelope representation of the resonator field and the second one based on representation of this field as a superposition of eigenmodes, whose fields are determined by a self-consistent set of equations. It is shown that at relatively low beam currents, when the maximum efficiency can be realized in the regime of soft self-excitation, the operation in the desired mode is stable even in the case of a very dense spectrum of competing modes. At higher currents, the maximum efficiency can be realized in the regimes with hard self-excitation; here the operation in the desired mode can be unstable because of the presence of some competing modes with low start currents. Two 170 GHz European gyrotrons for the international thermonuclear experimental reactor are considered as examples. In the first one, which is the 2 MW gyrotron with a coaxial resonator, the stability of operation in a chosen TE{sub 34,19}-mode in the presence of two sideband modes with almost equidistant spectrum is analyzed and the region of magnetic fields in which the oscillations of the central mode are stable is determined. The operation of the second gyrotron, which is the 1 MW gyrotron with a cylindrical cavity currently under development in Europe, is studied by using the wave envelope approach. It is shown that high efficiency operation of this gyrotron in the TE{sub 32,9}-mode should be stable.

  10. CW silver ion laser with electron beam excitation

    NASA Astrophysics Data System (ADS)

    Wernsman, B.; Prabhuram, T.; Lewis, K.; Gonzalez, F.; Villagran, M.

    1988-08-01

    A CW laser power of 140 mW was obtained in the 840.39-nm transition of Ag II by electron-beam excitation. The electron-beam excited metal-vapor ion laser is capable of operating using metals with high vaporization temperatures, and is of interest for generation of CW coherent radiation in the 220-260-nm spectral region.

  11. PRACTICAL EXERIENCES WITH THE 6 GYROTRON SYSTEM ON THE DIII-D TOKAMAK

    SciTech Connect

    LOHR,J; CARY,W.P; GORELOV,Y.A; GRUNLOH,H.J; KAJIWARA,K; PEAVY,J.J; PONCE,D; TOOKER,J; CALLIS,R.W

    2003-10-01

    OAK-B135 The gyrotron installation on the DIII-D tokamak now comprises six 110 GHz gyrotrons in the 1 MW class, three manufactured by CPI[1] and three by Gycom [2]. Two tetrode rectifier/modulator/regulator power supplies were constructed to provide power for the CPI gyrotrons. A second system uses three mod/reg tetrodes connected in parallel, which are fed by a dual parallel tetrode mod/reg to power the Gycom tubes. the windowless evacuated transmission lines are up to 100 m in length, with 80% transmission efficiency. Engineering solutions were developed in specific problematic areas encountered in the development of this complex system, including: Gyrotron instability; high voltage circuit instability; gyrotron conditioning; rf beam forming and coupling to waveguide; output window vacuum seals; material control; launcher mechanics and diagnosis; polarizer mechanics; dummy loads; power measurements; polarization measurements; cooling; calorimetry; and operating controls. The system is in routine operation in support of tokamak experiments, with peak generated power of about 5 MW at 2 s. pulse length and about 3 MW for 5 s. pulses. This presentation focuses on practical lessons learned in the development and operation of these systems.

  12. Development of an Ultra High Frequency Gyrotron with a Pulsed Magnet

    SciTech Connect

    Idehara, T.; Kamada, M.; Tsuchiya, H.; Hayashi, T.; Agusu, La; Mitsudo, S.; Ogawa, I.; Manuilov, V. N.; Naito, K.; Yuyama, T.; Jiang, W.; Yatsui, K.

    2006-01-03

    An ultra-high frequency gyrotron is being developed as a THz radiation source by using a pulsed magnet. We have achieved the highest field intensity of 20.2 T. High frequency operation at the second harmonic will achieve 1.01 THz; the corresponding cavity mode is TE6,11,1. On the other hand, an ultra-high power gyrotron with a pulsed magnet is also being developed as a millimeter to submillimeter wave radiation source. The gyrotron is a large orbit gyrotron (LOG) using an intense relativistic electron beam (IREB). A pulsed power generator 'ETIGO-IV' is applied for generation of the IREB. A prototype relativistic LOG was constructed for fundamental operation. The output of the LOG will achieve 144 GHz and 9 MW; the corresponding cavity mode is TE1,4,1. Cavities for 2nd and 4th harmonic operations were designed by numerical simulation for achievement of higher frequency. The progress of development for prototype high frequency gyrotrons with pulsed magnets is presented.

  13. Frequency measurements of the gyrotrons used for collective Thomson scattering diagnostics at TEXTOR and ASDEX Upgrade

    SciTech Connect

    Woskov, P.; Bindslev, H.; Leipold, F.; Meo, F.; Nielsen, S. K.; Tsakadze, E. L.; Korsholm, S. B.; Scholten, J.; Tito, C.; Westerhof, E.; Oosterbeek, J. W.; Leuterer, F.; Monaco, F.; Muenich, M.; Wagner, D.

    2006-10-15

    High resolution frequency measurements of the 110 GHz gyrotron at TEXTOR and the 105 GHz mode of the two-frequency gyrotron (Odissey-1) at ASDEX Upgrade (AUG) have been made in support of fast ion collective Thomson scattering diagnostics. Measurements were done by harmonic heterodyne methods using both fast Fourier transform spectroscopy with digital oscilloscopes and fast scanning spectrum analyzers. Accurate frequencies were obtained with a frequency counter. At TEXTOR, at 180 kW forward power the starting frequency was 109.970{+-}0.005 GHz and chirped down as much as 27 MHz depending on the duty factor. At AUG, at 500 kW forward power the frequency started at 104.786 GHz and chirped down 104 MHz, with 90% of the chirp occurring in the first 100 ms. Plasma perturbation of the TEXTOR gyrotron was observed when both ion cyclotron resonance heating antennas and neutral beam injection were operating, producing modulation at 29 and 58 MHz in the gyrotron output. Each gyrotron was observed to have an instrumental measurement limited linewidth of 120 kHz full width at half maximum.

  14. Moderate-power cw fibre lasers

    SciTech Connect

    Kurkov, Andrei S; Dianov, Evgenii M

    2004-10-31

    A review of the development and investigation of moderate-power (10{sup -1}-10{sup 2} W) cw fibre lasers is presented. The properties of optical fibres doped with rare-earth ions and methods for fabricating double-clad fibres are considered. The methods for fabrication of fibre Bragg gratings used as selective reflectors are discussed and the grating properties are analysed. The main pump schemes for double-clad fibre lasers are described. The properties of fibre lasers doped with neodymium, ytterbium, erbium, thulium, and holmium ions are also considered. The principles of fabrication of Raman converters of laser radiation based on optical fibres of different compositions are discussed and the main results of their studies are presented. It is concluded that fibre lasers described in the review can produce moderate-power radiation at any wavelength in the spectral range from 0.9 to 2 {mu}m. (review)

  15. Development of Dual-Frequency Gyrotron with Triode Magnetron Injection Gun

    NASA Astrophysics Data System (ADS)

    Kajiwara, Ken; Oda, Yasuhisa; Kasugai, Atsushi; Takahashi, Koji; Sakamoto, Keishi

    2011-12-01

    A high power dual-frequency gyrotron is designed and tested. The design is based on a 170 GHz single-frequency gyrotron with a triode magnetron injection gun (MIG). The triode MIG enables to choose variety of oscillation modes for different frequencies with suitable pitch factor, which is the great advantage for a multi-frequency gyrotron. Another frequency of 137 GHz is selected in order to use a 1.853-mm-thick single-disk output window. Cavity modes are TE31,11 and TE25,9 for 170 and 137 GHz, respectively, which have high mode conversion efficiency to the RF beam mode with similar radiation angles. In short-pulse experiments, the maximum power of more than 1.3 MW is achieved with high-efficiency for both frequencies.

  16. Influence of emitter surface roughness on high power fusion gyrotron operation

    NASA Astrophysics Data System (ADS)

    Zhang, Jianghua; Illy, Stefan; Pagonakis, Ioannis Gr; Avramidis, Konstantinos A.; Thumm, Manfred; Jelonnek, John

    2016-02-01

    Emitter surface roughness is one of the important factors of electron beam degradation in magnetron injection gun (MIG) and the decrease of gyrotron efficiency. This paper surveys the influence of emitter surface roughness on the operation of the EU 1 MW 170 GHz gyrotron for ITER for two different gun designs. The emitter surface roughness was taken into account using a simple model. The ESRAY code was used for gun simulation and the EURIDICE code for calculation of the RF interaction in the cavity. The degradation of the beam quality due to the surface roughness is quantitatively studied and, furthermore, the influence on the gyrotron efficiency and the mode competition are investigated. Some dramatic phenomena, such as the generation of magnetically trapped electrons, are predicted at a very high level of roughness.

  17. Novel linear analysis for a gyrotron oscillator based on a spectral approach

    NASA Astrophysics Data System (ADS)

    Genoud, J.; Tran, T. M.; Alberti, S.; Braunmueller, F.; Hogge, J.-Ph.; Tran, M. Q.; Guss, W. C.; Temkin, R. J.

    2016-04-01

    With the aim of gaining a better physical insight into linear regimes in gyrotrons, a new linear model was developed. This model is based on a spectral approach for solving the self-consistent system of equations describing the wave-particle interaction in the cavity of a gyrotron oscillator. Taking into account the wall-losses self-consistently and including the main system inhomogeneities in the cavity geometry and in the magnetic field, the model is appropriate to consider real system parameters. The main advantage of the spectral approach, compared with a time-dependent approach, is the possibility to describe all of the stable and unstable modes, respectively, with negative and positive growth rates. This permits to reveal the existence of a new set of eigenmodes, in addition to the usual eigenmodes issued from cold-cavity modes. The proposed model can be used for studying other instabilities such as, for instance, backward waves potentially excited in gyrotron beam tunnels.

  18. THz Gyrotron and BWO Designed for Operation in DNP-NMR Spectrometer Magnet

    NASA Astrophysics Data System (ADS)

    Bratman, V. L.; Fedotov, A. E.; Kalynov, Yu. K.; Makhalov, P. B.; Samoson, A.

    2013-12-01

    Dynamic nuclear polarization (DNP) in high-field nuclear magnetic resonance (NMR) spectroscopy requires medium-power terahertz radiation, which nowadays can be provided basically by gyrotrons with superconducting magnets. As the electron cyclotron frequency is very close to the frequency of electron paramagnetic resonance for the same magnetic field, under certain conditions the gyrotron can be installed inside the same solenoid used for NMR spectrometer. This eliminates the need for an additional superconducting magnet, results in a shorter terahertz transmission line, and can make DNP systems practical. In addition to an extremely low-voltage gyrotron ("gyrotrino"), we analyze also advantages of strong magnetic field for a slow-wave electron device as an alternative terahertz source.

  19. Principles of gyrotron powered electromagnetic wigglers for free-electron lasers

    SciTech Connect

    Danly, B.G.; Bekefi, G.; Davidson, R.C.; Temkin, R.J.; Tran, T.M.; Wurtele, J.S.

    1987-01-01

    The operation of free-electron lasers (FEL's) with axial electron beams and high-power electromagnetic wiggler fields such as those produced by high-power gyrotrons is discussed. The use of short wavelength electromagnetic wigglers in waveguides and resonant cavities can significantly reduce required electron beam voltages, resulting in compact FEL's. Gain calculations in the low- and high-gain Compton regime are presented, including the effects of emittance, transverse wiggler gradient, and electron temperature. Optimized scaling laws for the FEL gain and the required electromagnetic wiggler field power are discussed. Several possible configurations for FEL's with electromagnetic wigglers powered by millimeter wavelength gyrotrons are presented. Gyrotron powered wigglers appear promising for operation of compact FEL's in the infrared regime using moderate energy (<10 MeV) electron beams.

  20. Nonlinear theory of stable, efficient operation of a gyrotron at cyclotron harmonics

    NASA Astrophysics Data System (ADS)

    Saraph, G. P.; Antonsen, T. M., Jr.; Nusinovich, G. S.; Levush, B.

    1993-12-01

    One of the main obstacles in achieving stable, efficient operation at the cyclotron harmonics in a gyrotron is mode competition with parasitic modes at the fundamental frequency. In this article, the nonlinear dynamics of mode interactions in such a system are studied using a multifrequency, time-dependent model. The results of numerical simulations for a second harmonic gyrotron are presented by considering two starting scenarios: (a) fast voltage rise or an instant turn-on case, and (b) slow voltage rise case. For the first case, it is demonstrated that for a certain range of operating parameters, the presence of a parasitic mode at the fundamental can be helpful in the excitation of the second harmonic operating mode. In the second case, it is found that the unstable operating region increases with the value of the rise time constant of the electrode voltages. Stable, efficient gyrotron operation at the second harmonic is demonstrated using the numerical study.

  1. 140-GHz gyrotron experiments based on a confocal cavity

    SciTech Connect

    Hu, W.; Shapiro, M.A.; Kreischer, K.E.; Temkin, R.J.

    1998-06-01

    The authors have designed and experimentally demonstrated the operation of a novel quasioptical gyrotron oscillator based on an overmoded confocal waveguide cavity. This cavity effectively suppresses undesired modes, and therefore has extremely low mode density. Stable single-mode, single-frequency operation was achieved in the TE06 mode at 136 GHz. A peak RF output power of 66 kW, corresponding to an efficiency of 18%, was measured. By varying the cavity magnetic field, high-power generation was observed at 136 GHz in the TE{sub 06} mode and at 114 GHz in the TE{sub 05} mode. These frequencies correspond to the high Q modes of the confocal resonator. The low Q modes were either weak or not observed. In this paper, the authors will review the design procedure for this cavity and present experimental data verifying its effectiveness in reducing the number of modes that can be excited. The confocal waveguide could also be used in high-power, gyro-TWT amplifiers to provide greater operating stability and bandwidth, especially in an overmoded waveguide structure.

  2. High-power operation of a 170 GHz megawatt gyrotron

    SciTech Connect

    Kreischer, K.E.; Kimura, T.; Danly, B.G.; Temkin, R.J.

    1997-05-01

    Recent gyrotron oscillator experiments have achieved record powers at 170 GHz. Single mode emission with a peak output power of 1.5 MW and an efficiency of 35{percent} has been measured. The experiment is based on a resonant TE{sub 28,8,1} cylindrical cavity situated in a 6.7 T magnetic field. Microwaves are generated in the cavity by an 83 kV annular electron beam produced by a triode-type magnetron injection gun that is capable of currents up to 50 A. Megawatt power levels with efficiencies between 30{percent}{endash}36{percent} have been measured over a wide range of operating parameters for the TE{sub 28,8,1} mode. Similar results were also achieved in the neighboring TE{sub 27,8,1} mode at 166.6 GHz, and the TE{sub 29,8,1} mode at 173.5 GHz. The high output power is the result of a carefully designed electron gun with low perpendicular velocity spread (6{percent}{endash}10{percent}) and a novel cavity with an output iris that is less prone to mode competition. These results are in good agreement with nonlinear multimode simulations. {copyright} {ital 1997 American Institute of Physics.}

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

    NASA Astrophysics Data System (ADS)

    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.

  4. Stable, high efficiency gyrotron backward-wave oscillator

    SciTech Connect

    Fan, C. T.; Chang, T. H.; Pao, K. F.; Chu, K. R.; Chen, S. H.

    2007-09-15

    Stability issues have been a major concern for the realization of broadband tunability of the gyrotron backward-wave oscillator (gyro-BWO). Multimode, time-dependent simulations are employed to examine the stability properties of the gyro-BWO. It is shown that the gyro-BWO is susceptible to both nonstationary oscillations and axial mode competition in the course of frequency tuning. Regions of nonstationary oscillations and axial mode competition are displayed in the form of stability maps over wide-ranging parameter spaces. These maps serve as a guide for the identification and optimization of stable windows for broadband tuning. Results indicate that a shorter interaction length provides greater stability without efficiency degradation. These theoretical predictions have been verified in a Ka-band gyro-BWO experiment using both short and long interaction lengths. In the case of a short interaction length, continuous and smooth tunability, in magnetic field and in beam voltage, was demonstrated with the high interaction efficiency reported so far. A maximum 3-dB tuning range of 1.3 GHz with a peak power of 149 kW at 29.8% efficiency was achieved. In a comparative experiment with a longer interaction length, the experimental data are characterized by piecewise-stable tuning curves separated by region(s) of nonstationary oscillations, as predicted by theory.

  5. Numerical Simulation of MIG for 42 GHz, 200 kW Gyrotron

    NASA Astrophysics Data System (ADS)

    Singh, Udaybir; Bera, Anirban; Kumar, Narendra; Purohit, L. P.; Sinha, Ashok K.

    2010-06-01

    A triode type magnetron injection gun (MIG) of a 42 GHz, 200 kW gyrotron for an Indian TOKAMAK system is designed by using the commercially available code EGUN. The operating voltages of the modulating anode and the accelerating anode are 29 kV and 65 kV respectively. The operating mode of the gyrotron is TE03 and it is operated in fundamental harmonic. The simulated results of MIG obtained with the EGUN code are validated with another trajectory code TRAK.

  6. Real-time, T-ray imaging using a sub-terahertz gyrotron

    NASA Astrophysics Data System (ADS)

    Han, Seong-Tae; Torrezan, Antonio C.; Sirigiri, Jagadishwar R.; Shapiro, Michael A.; Temkin, Richard J.

    2012-06-01

    We demonstrated real-time, active, T-ray imaging using a 0.46 THz gyrotron capable of producing 16 W in continuous wave operation and a pyroelectric array camera with 124-by-124 pixels. An expanded Gaussian beam from the gyrotron was used to maintain the power density above the detection level of the pyroelectric array over the area of the irradiated object. Real-time imaging at a video rate of 48 Hz was achieved through the use of the built-in chopper of the camera. Potential applications include fast scanning for security purposes and for quality control of dry or frozen foods.

  7. Two-wave regime of operation of the high-harmonic gyrotron

    SciTech Connect

    Savilov, A. V.; Denisov, G. G.; Kalynov, Yu. K.; Osharin, I. V.

    2015-04-15

    The use of the two-wave co-generation is proposed as a way to decrease the effective Q-factor of the operating near-cutoff wave of the gyrotron. In this two-wave regime, the operating wave represents a “hot” wave mode formed by two partial “cold” modes (near-cutoff and far-from-cutoff ones) coupled on the electron beam. It is shown that the use of this regime can provide a significant decrease of the Ohmic losses in low-relativistic high-harmonic gyrotrons operating in the THz frequency range.

  8. Collective backscattering of gyrotron radiation by small-scale plasma density fluctuations in large helical device.

    PubMed

    Kharchev, Nikolay; Tanaka, Kenji; Kubo, Shin; Igami, Hiroe; Batanov, German; Petrov, Alexandr; Sarksyan, Karen; Skvortsova, Nina; Azuma, Yoshifumi; Tsuji-Iio, Shunji

    2008-10-01

    A version of the collective backscattering diagnostic using gyrotron radiation for small-scale turbulence is described. The diagnostic is used to measure small-scale (k(s) approximately 34 cm(-1)) plasma density fluctuations in large helical device experiments on the electron cyclotron heating of plasma with the use of 200 kW 82.7 GHz heating gyrotron. A good signal to noise ratio during plasma production phase was obtained, while contamination of stray light increased during plasma build-up phase. The effect of the stray radiation was investigated. The available quasioptical system of the heating system was utilized for this purpose. PMID:19044538

  9. Design of interaction cavity for 170 GHz, 1 MW ITER gyrotron

    SciTech Connect

    Kumar, Anil; Kumar, Nitin; Khatun, Hasina; Singh, Udaybir; Sinha, A.K. E-mail: aksinha@ceeri.ernet.in; Vyas, V.

    2011-07-01

    In this paper the design of interaction cavity for 170 GHz, 1 MW gyrotron is presented. An in-house developed code GCOMS has been used for operating mode selection and mode competition. For 170 GHz, 1 MW gyrotron interaction cavity TE28, 7 mode excite as a operating mode at the fundamental harmonic number. The electromagnetic simulator-MAGIC, a Particle-in-Cell (PIC) code has been used for the cold cavity analysis and the beam-wave interaction. More than 1MW output power has been achieved at guiding cavity magnetic field 6.77 T. (author)

  10. Dynamics of mode competition in the gyrotron backward-wave oscillator.

    PubMed

    Pao, K F; Chang, T H; Fan, C T; Chen, S H; Yu, C F; Chu, K R

    2005-10-28

    The axial modes of the gyrotron backward-wave oscillator (gyro-BWO) each exhibit a distinctive asymmetry in axial field profile. As a result, and in sharp contrast to the behavior of the familiar resonator-based gyrotron oscillator, particle simulations of the gyro-BWO reveal a radically different pattern of mode competition in which a fast-growing and well-established mode is subsequently suppressed by a later-starting mode with a more favorable field profile. This is verified in a Ka-band experiment and the interaction dynamics are elucidated with a time-frequency analysis. PMID:16383909

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

    NASA Astrophysics Data System (ADS)

    Bandurkin, I. V.; Kalynov, Yu. K.; Osharin, I. V.; Savilov, A. V.

    2016-01-01

    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.

  12. Collective backscattering of gyrotron radiation by small-scale plasma density fluctuations in large helical device

    SciTech Connect

    Kharchev, Nikolay; Batanov, German; Petrov, Alexandr; Sarksyan, Karen; Skvortsova, Nina; Tanaka, Kenji; Kubo, Shin; Igami, Hiroe; Azuma, Yoshifumi; Tsuji-Iio, Shunji

    2008-10-15

    A version of the collective backscattering diagnostic using gyrotron radiation for small-scale turbulence is described. The diagnostic is used to measure small-scale (k{sub s}{approx_equal}34 cm{sup -1}) plasma density fluctuations in large helical device experiments on the electron cyclotron heating of plasma with the use of 200 kW 82.7 GHz heating gyrotron. A good signal to noise ratio during plasma production phase was obtained, while contamination of stray light increased during plasma build-up phase. The effect of the stray radiation was investigated. The available quasioptical system of the heating system was utilized for this purpose.

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

    SciTech Connect

    Ginzburg, N. S.; Sergeev, A. S.; Zotova, I. V.

    2015-03-15

    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.

  14. Generation of 1.5-kW, 1-THz coherent radiation from a gyrotron with a pulsed magnetic field.

    PubMed

    Glyavin, M Yu; Luchinin, A G; Golubiatnikov, G Yu

    2008-01-11

    To cover a so-called terahertz gap in available sources of coherent electromagnetic radiation, the gyrotron with a pulsed solenoid producing up to a 40 T magnetic field has been designed, manufactured, and tested. At a 38.5 T magnetic field, the gyrotron generated coherent radiation at 1.022 THz frequency in 50 musec pulses. The microwave power and energy per pulse were about 1.5 kW and 75 mJ, respectively. Details of the gyrotron design, manufacturing, operation and measurements of output radiation are given. PMID:18232780

  15. Three-dimensional particle-in-cell modeling of terahertz gyrotrons with cylindrical and planar configurations of the interaction space

    SciTech Connect

    Zaslavsky, V. Yu.; Ginzburg, N. S.; Glyavin, M. Yu.; Zheleznov, I. V.; Zotova, I. V.

    2013-04-15

    We perform 3D particle-in-cell simulations of terahertz gyrotrons with two different configurations of the interaction space. For a gyrotron with conventional cylindrical configuration of the interaction cavity, we demonstrate reasonable agreement between simulations and experimental results, including output frequency, structure of the higher-order operating mode (TE{sub 17,4}), output power, and ohmic losses. For a novel planar gyrotron scheme with transverse energy extraction, a possibility of further increasing the oversized factor with the single-mode operation regime retained is shown. Frequency detuning by mechanical variation of the gap between waveguide plates is also demonstrated.

  16. Generation of 1.5-kW, 1-THz Coherent Radiation from a Gyrotron with a Pulsed Magnetic Field

    SciTech Connect

    Glyavin, M. Yu.; Luchinin, A. G.; Golubiatnikov, G. Yu.

    2008-01-11

    To cover a so-called terahertz gap in available sources of coherent electromagnetic radiation, the gyrotron with a pulsed solenoid producing up to a 40 T magnetic field has been designed, manufactured, and tested. At a 38.5 T magnetic field, the gyrotron generated coherent radiation at 1.022 THz frequency in 50 {mu}sec pulses. The microwave power and energy per pulse were about 1.5 kW and 75 mJ, respectively. Details of the gyrotron design, manufacturing, operation and measurements of output radiation are given.

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

    NASA Astrophysics Data System (ADS)

    Ginzburg, N. S.; Sergeev, A. S.; Zotova, I. V.

    2015-03-01

    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.

  18. Multimegawatt relativistic harmonic gyrotron traveling-wave tube amplifier experiments

    SciTech Connect

    Menninger, W.L.; Danly, B.G.; Temkin, R.J.

    1996-06-01

    The first multimegawatt harmonic relativistic gyrotron traveling-wave tube (gyro-twt) amplifier experiment has been designed, built, and tested. Results from this experimental setup, including the first ever reported third-harmonic gyro-twt results, are presented. Operation frequency is 17.1 GHz. Detailed phase measurements are also presented. The electron beam source is SNOMAD-II, a solid-state nonlinear magnetic accelerator driver with nominal parameters of 400 kV and 350 A. The flat-top pulsewidth is 30 ns. The electron beam is focused using a Pierce geometry and then imparted with transverse momentum using a bifilar helical wiggler magnet. Experimental operation involving both a second-harmonic interaction with the TE{sub 21} mode and a third-harmonic interaction with the TE{sub 31} mode, both at 17 GHz, has been characterized. The third-harmonic interaction resulted in 4-MW output power and 50-dB single-pass gain, with an efficiency of up to {approximately}8%. The best measured phase stability of the TE{sub 31} amplified pulse was {+-}10{degree} over a 9-ns period. The phase stability was limited because the maximum RF power was attained when operating far from wiggler resonance. The second harmonic, TE{sub 21} had a peak amplified power of 2 MW corresponding to 40-dB single-pass gain and 4% efficiency. The second-harmonic interaction showed stronger superradiant emission than the third-harmonic interaction. Characterizations of the second- and third-harmonic gyro-twt experiments presented here include measurement of far-field radiation patterns, gain and phase versus interaction length, phase stability, and output power versus input power.

  19. High efficiency cw laser-pumped tunable alexandrite laser

    SciTech Connect

    Lai, S.T.; Shand, M.L.

    1983-10-01

    High efficiency cw alexandrite laser operation has been achieved. With longitudinal pumping by a krypton laser in a nearly concentric cavity, a 51% output power slope efficiency has been measured. Including the transmission at the input coupler mirror, a quantum yield of 85% has been attained above threshold. Tunability from 726 to 802 nm has also been demonstrated. The low loss and good thermal properties make alexandrite ideal for cw laser operation.

  20. 3 μm CW lasers for myringotomy and microsurgery.

    PubMed

    Linden, Kurt J; Pfeffer, Christian P; Sousa, John Gary; D'Alleva, Nicholas; Aslani, Arash; Gorski, Grzegorz; Kenna, Margaret; Poe, Dennis S

    2013-03-01

    This paper describes the development and implementation of 3 μm lasers for myringotomy and microsurgery. Two different lasers were investigated. The first, an Er-doped, CW zirconate glass fiber laser optically pumped by a 970 nm diode laser, emitted > 1 W of CW power at 2.76 μm with concomitant green incoherent emission that served as a convenient visible illumination beam. The second, a 1 W CW Er:YAG solid-state laser also optically pumped by a 970 nm diode laser, emitted > 1 W of CW power at 2.94 μm, coincident with the strongest infrared water absorption peak. Running CW, both lasers are expected to avoid the loud acoustical shocks associated with pulsed lasers. Myringotomies were carried out with the Er:YAG laser on anaesthetized guinea pigs and the effects of the laser were documented. Laser ablated samples of tympanic membrane, soft tissue and bone were histologically examined. Histology results indicated that the CW Er:YAG laser is a potential candidate for a new myringotomy tool and possibly for otologic microsurgery, but deliverable power levels need to be increased to the 2 W (or higher) level. This work was funded under NIH SBIR Grant No. 5R44DC004899. PMID:24382990

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

    DOE PAGESBeta

    Lohr, J.; Anderson, J. P.; Cengher, M.; Ellis, R. A.; Gorelov, Y. A.; Kolemen, E.; Lambot, T.; Murakami, D. D.; Myrabo, L.; Noraky, S.; et al

    2015-03-12

    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.

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

    NASA Astrophysics Data System (ADS)

    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.

  3. High-frequency gyrotron scattering diagnostic for instability studies on TARA

    SciTech Connect

    Woskoboinikow, P.; Cohn, D.R.; Gerver, M.; Mulligan, W.J.; Post, R.S.; Temkin, R.J.; Trulsen, J.

    1985-05-01

    A 1- to 10-kW,>30-ms pulsed, narrow linewidth (<1 MHz), 137-GHz gyrotron is being fabricated for collective Thomson scattering plasma diagnostics on the TARA tandem mirror experiment. The drift cyclotron loss cone, the axial loss cone, harmonics of these instabilities, and the ion two stream instability in the TARA plugs will be studied with this diagnostic.

  4. Study on Low-Frequency Oscillations in a Gyrotron Using a 3D CFDTD PIC Method

    NASA Astrophysics Data System (ADS)

    Lin, M. C.; Smithe, D. N.

    2010-11-01

    Low-frequency oscillations (LFOs) have been observed in a high average power gyrotron and the trapped electron population contributing to the oscillation has been measured. As high average power gyrotrons are the most promising millimeter wave source for thermonuclear fusion research, it is important to get a better understanding of this parasitic phenomenon to avoid any deterioration of the electron beam quality thus reducing the gyrotron efficiency. 2D Particle-in-cell simulations quasi-statically model the development of oscillations of the space charge in the adiabatic trap, but the physics of the electron dynamics in the adiabatic trap is only partially understood. Therefore, understanding of the LFOs remains incomplete and a full picture of this parasitic phenomenon has not been seen yet. In this work, we use a 3D conformal finite-difference time-domain (CFDTD) particle-in-cell (PIC) method to accurately and efficiently study the LFOs in a high average power gyrotron. As the CFDTD method exhibits a second order accuracy, complicated structures, such as a magnetron injection gun, can be well described. Employing a highly parallelized computation, the model can be simulated in time domain more realistically.

  5. 3D CFDTD PIC Simulation Study on Low-Frequency Oscillations in a Gyrotron

    NASA Astrophysics Data System (ADS)

    Lin, M. C.; Smithe, D. N.

    2011-10-01

    Low-frequency oscillations (LFOs) have been observed in a high average power gyrotron and the trapped electron population contributing to the oscillation has been measured. As high average power gyrotrons are the most promising millimeter wave source for thermonuclear fusion research, it is important to get a better understanding of this parasitic phenomenon to avoid any deterioration of the electron beam quality thus reducing the gyrotron efficiency. However, understanding of the LFOs remains incomplete and a full picture of this parasitic phenomenon has not been seen yet. In this work, we use a 3D conformal finite-difference time-domain (CFDTD) particle-in-cell (PIC) method to accurately and efficiently study the LFOs in a magnetron injection gun (MIG) of a high average power gyrotron. Employing a highly parallelized computation, the model can be simulated in time domain more realistically. LFOs have been obtained in a 3D time domain simulation for the first time. From our preliminary simulation studies, it is found that not only magnetic compression profile but initial velocity or velocity ratio play an important role in the operation of a MIG electron gun. In addition, the secondary emission effects on the LFOs are also studied. Detailed results will be presented. Work supported by the U.S. Department of Energy under Grant No. DE-SC0004436.

  6. Electron Optical System of the Sub-terahertz Coaxial Gyrotron with Continuous Frequency Tuning

    NASA Astrophysics Data System (ADS)

    Manuilov, V.; Glyavin, M.; Idehara, T.; Saito, T.

    2010-08-01

    Analytical estimations and the results of numerical analysis of the electron beam parameters in the reverse moderate power (15 kV/1A) Magnetron Injection Gun (MIG) for a coaxial 394.6 GHz gyrotron are presented. The design of the MIG with a movable inner rod is discussed, and the influence of emitter roughness is analyzed.

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

    NASA Astrophysics Data System (ADS)

    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.

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

    PubMed Central

    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

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

    NASA Astrophysics Data System (ADS)

    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.

  10. Start-up scenario in gyrotrons with a nonstationary microwave-field structure.

    PubMed

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

    2006-03-31

    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, 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 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. PMID:16605920

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

    SciTech Connect

    Dumbrajs, O.; Nusinovich, G. S.

    2010-05-15

    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.

  12. Moment-based, self-consistent linear analysis of gyrotron oscillators

    SciTech Connect

    Braunmueller, F. Tran, T. M.; Alberti, S.; Hogge, J.-Ph.; Tran, M. Q.

    2014-04-15

    A new model for simulating gyrotron oscillators in the monomode time-dependent linear self-consistent regime is presented. Starting from a nonlinear time-dependent monomode model, the linearization and the following simplification of the model, based on a moment approach, are described. This simplified model represents a numerically efficient model and allows to have a deeper physical insight, in particular, for regimes dominated by self-consistent effects such as for the gyro-backward wave instability. One specific case of a gyrotron cavity is studied in detail and compared with experimental results, with special attention to self-consistent effects and to the differences with a model using a fixed field profile. Self-consistent linear simulations are, amongst other applications, important for the design of frequency-tunable gyrotrons or high-power gyrotrons with cavities having a relatively low quality factor, but also for studies of parasitic oscillations as they may occur in beam ducts and/or in the launcher section following the interaction cavity.

  13. Experimental observation of the effect of aftercavity interaction in a depressed collector gyrotron oscillator

    SciTech Connect

    Choi, E. M.; Shapiro, M. A.; Sirigiri, J. R.; Temkin, R. J.

    2007-09-15

    This paper presents the experimental observation of the effect of an aftercavity interaction (ACI) in a depressed collector gyrotron oscillator. The gyrotron generates an output power of 1.5 MW at 110 GHz in 3 {mu}s pulses with a 96 kV and 40 A electron beam and has a single-stage depressed collector. The ACI arises from an unintended cyclotron resonant interaction between the microwave beam traveling out from the cavity and the gyrating electron beam. The interaction occurs in the uptaper of the launcher, immediately downstream from the cavity, where the magnetic field is slightly lower than its value in the cavity region. The ACI results in a reduction in efficiency since the electron beam tends to extract power from the wave. There is also a broadening of the spent beam energy profile, which reduces the effectiveness of the depressed collector and in turn limits the overall efficiency of a gyrotron. Measurements of the maximum depression voltage of the collector vs beam current at 96 kV are compared with simulations from the MAGY code [M. Botton et al., IEEE Trans. Plasma Sci. 26, 882 (1998)]. Excellent agreement is obtained between theory and experiment but only if the ACI is included. In the present experiment, it is estimated that the observed efficiency of 50% would have been about 60% in the absence of the ACI. These results verify the role of the ACI in reducing the efficiency of the gyrotron interaction.

  14. CONDITIONING AND PROTECTION CIRCUITRY FOR EXTERNAL MODULATION OF A PREPROGRAMMED GYROTRON CATHODE VOLTAGE COMMAND WAVEFORM

    SciTech Connect

    PONCE,D; FERRON,J.R; LEGG,R.A

    2003-10-01

    OAK-B135 The modulating voltages applied to the DIII-D gyrotrons are controlled by reference signals which are synthesized by arbitrary waveform generators.These generators allow ECH operators to pre-program reference waveforms consisting of ramps, flat tops, and various modulation shapes. This capability is independent of the DIII-D central timing and waveform facilities, which provides the ECH operators operational flexibility. The waveform generators include an amplitude modulation input, providing a means to control the pre-programmed waveform externally. This input is being used to allow the DIII-D plasma control system (PCS) to control gyrotron power in response top selected feedback signals. As the PCS control signal could potentially modulate the gyrotrons beyond operational limits or otherwise in a manner leading to recalcitrant rf generation, the control signal is conditioned so that its effect upon the ECH pre-programmed reference waveform is limited by conditions set by the ECH operators. The design of the circuitry which restricts the range over which the PCS control signal may modulate the reference waveform will be discussed. Test and DIII-D experimental results demonstrating the utility and effectiveness of gyrotron power modulated by the PCS will be presented.

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

    PubMed

    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

  16. A comparative study on the modeling of dynamic after-cavity interaction in gyrotrons

    NASA Astrophysics Data System (ADS)

    Avramidis, K. A.; Ioannidis, Z. C.; Kern, S.; Samartsev, A.; Pagonakis, I. Gr.; Tigelis, I. G.; Jelonnek, J.

    2015-05-01

    There are cases where gyrotron interaction simulations predict dynamic After-Cavity Interaction (ACI). In dynamic ACI, a mode is excited by the electron beam at a dominant frequency in the gyrotron cavity and, at the same time, this mode is also interacting with the beam at a different frequency in the non-linear uptaper after the cavity. In favor of dynamic ACI being a real physical effect, there are some experimental findings that could be attributed to it, as well as some physical rationale indicating the possibility of a mode being resonant with the beam at different frequencies in different regions. However, the interaction codes used in dynamic ACI prediction up to now are based on simplifications that put questions on their capability of correctly simulating this effect. In this work, the shortcomings of the usual simplifications with respect to dynamic ACI modeling, namely, the trajectory approach and the single-frequency boundary condition, are identified. Extensive simulations of dynamic ACI cases are presented, using several "in-house" as well as commercial codes. We report on the comparison and the assessment of different modeling approaches and their results and we discuss whether, in some cases, dynamic ACI can be a numerical artifact or not. Although the possibility of existence of dynamic ACI in gyrotrons is not disputed, it is concluded that the widely used trajectory approach for gyrotron interaction modeling is questionable for simulating dynamic ACI and can lead to misleading results.

  17. TESTS AND PERFORMANCE ON THE SIX GYROTRON SYSTEM ON THE DIII-D TOKAMAK

    SciTech Connect

    LOHR,J; GORELOV,YA; KAJIWARA,K; PONCE,D; CALLIS,RW; FERRON,JR; GREENFIELD,CM; LAHAYE,RJ; PINSKER,RI; PRATER,R; WADE,MR; ELLIS,RA

    2002-09-01

    A271 TESTS AND PERFORMANCE ON THE SIX GYROTRON SYSTEM ON THE DIII-D TOKAMAK. The DIII-D gyrotron complex for electron cyclotron heating (ECH) and electron cyclotron current drive (ECCD) has been expanded to include five operational gyrotrons with a sixth being commissioned. The generated rf power exceeds 4.0 MW and the transmission lines deliver about 80% of this power to the tokamak. Among the experiments performed during the most recent campaign, the installation has been used to achieve stabilization of the m/n=2/1 and 3/2 neoclassical tearing modes, to control the rate of current penetration early in the discharge, and to study ECCD contributions to advanced tokamak discharges with high bootstrap fractions. Observations of the thermal performance of CVD diamond output windows have shown good agreement with theoretical predictions, but have revealed a number of interesting phenomena connected with impurities, including points of visible light emission at hot spots identified by infrared measurements. One window was cleaned in situ by alumina grit blasting and Raman spectra verified the removal of some surface contamination. A significant new capability is the simultaneous control of the output power of the entire array of gyrotrons by the DIII-D plasma control system. This allows a predetermined electron temperature evolution to be followed at a specific location in the plasma and opens a new group of experimental possibilities leading to the achievement of higher levels of tokamak performance.

  18. Moment-based, self-consistent linear analysis of gyrotron oscillators

    NASA Astrophysics Data System (ADS)

    Braunmueller, F.; Tran, T. M.; Alberti, S.; Hogge, J.-Ph.; Tran, M. Q.

    2014-04-01

    A new model for simulating gyrotron oscillators in the monomode time-dependent linear self-consistent regime is presented. Starting from a nonlinear time-dependent monomode model, the linearization and the following simplification of the model, based on a moment approach, are described. This simplified model represents a numerically efficient model and allows to have a deeper physical insight, in particular, for regimes dominated by self-consistent effects such as for the gyro-backward wave instability. One specific case of a gyrotron cavity is studied in detail and compared with experimental results, with special attention to self-consistent effects and to the differences with a model using a fixed field profile. Self-consistent linear simulations are, amongst other applications, important for the design of frequency-tunable gyrotrons or high-power gyrotrons with cavities having a relatively low quality factor, but also for studies of parasitic oscillations as they may occur in beam ducts and/or in the launcher section following the interaction cavity.

  19. Design for a compact CW atom laser

    NASA Astrophysics Data System (ADS)

    Power, Erik; Raithel, Georg

    2011-05-01

    We present a design for a compact continuous-wave atom laser on a chip. A 2D spiral-shaped quadrupole guide is formed by two 0.5 mm × 0.5 mm wires carrying 5 A each embedded in a Si wafer; a 1.5 mm × 0.5 mm wire on the bottom layer carries -10 A, producing a horizontal B-field that pushes the guiding channel center above the chip surface. The center-to-center separation between the top wires is varied from 1.6 mm at the start of the guide to 1 mm at the end, decreasing the guide height from ~ 500 μm to ~ 25 μm above the surface as the atoms travel the 70 cm-long guide. The magnetic gradient of the guiding channel gradually increases from ~ 100 G /cm to ~ 930 G /cm . These features result in continuous surface adsorption evaporative cooling and progressive magnetic compression. Spin flip losses are mitigated by a solenoid sewn around the guide to produce a longitudinal B-field. 87Rb atoms are gravitationally loaded into the guide. A far off-resonant light shift barrier at the end of the guide traps the atoms and allows formation of a BEC. Tuning the barrier height to create a non-zero tunneling rate equal to the loading rate completes the implementation of a CW atom laser. Two options for atom interferometry are implemented on the first-generation chip (matter-wave Fabry-Perot interferometer and guide-based Mach-Zehnder interferometer). Current construction status and challenges will be discussed, along with preliminary results.

  20. Phase locking of a second harmonic gyrotron using a quasi-optical circulator

    NASA Astrophysics Data System (ADS)

    Hoppe, Daniel J.; Perez, Raul M.; Bhanji, Alaudin M.; Guo, Hezhong Z.; Rogers, John; Tate, Jeffrey P.

    1995-09-01

    Phase locking of a high power pulsed gyrotron oscillator through the use of a quasi-optical circulator was investigated. A second harmonic gyrotron which features a novel complex cavity, operating at 34.5 GHz, was used in the experiment. The quasi-optical circulator consisted of a 5.75 inch diameter ferrite disk biased with a one kilogauss permanent magnet. A polarizing grid was used to separate the input and output signals in the circulator. In order to couple the gyrotron oscillator output efficiently to the quasi-optical system, a number of mode converters, TE03-TE02, TE02-TE01, TE01-TM11, and TM11-HE11, were required. The insertion loss of the circulator and mode converter chain was approximately 1 dB, and an isolation exceeding 25 dB was achieved. In addition, a low power WR28 waveguide isolator was inserted in the injection signal path, providing an additional 35 dB of isolation, for a total isolation of 60 dB. The injection signal was provided by a synthesized signal generator and a 100 Watt traveling wave tube amplifier. A sample of the gyrotron output signal was obtained through an additional horn and mixed with a sample of the injection signal, producing a difference signal. The injection signal was swept slowly through a known frequency range while the difference signal was recorded. The recorded signals were analyzed off-line, and the locking bandwidth was determined. Experiments were performed for injection powers from 0-60 Watts, and a gyrotron output power of approximately 80-100 kW. Phase locking was observed for all non-zero injection powers.

  1. CHARACTERISTICS OF DIAMOND WINDOWS ON THE 1 MW, 110 GHz GYROTRON SYSTEMS ON THE DIII-D TOKAMAK

    SciTech Connect

    Y.A. GORELOV; J. LOHR; R.W. CALLIS; D. PONCE

    2002-08-01

    Diamond disks made using the chemical vapor deposition (CVD) technique are now in common use as gyrotron output windows. The low millimeter wave losses and excellent thermal conductivity of diamond have made it possible to use such windows in gyrotrons with {approx}1 MW output power and pulse length up to and greater than 10 s. A ubiquitous characteristic of diamond gyrotron windows is the presence of apparent hot spots in the infrared images registered during rf pulses. Many of these spots are co-located with bright points seen in visible video images. The spots do not seem to compromise the integrity of the windows. Analysis of the infrared observations on several different gyrotrons operating at the DIII-D tokamak are reported.

  2. Numerical study of the start-up scenario of a 670 GHz gyrotron operation at TE31,8 mode

    NASA Astrophysics Data System (ADS)

    Pu, Ruifeng; Sinitsyn, Oleksandr; Nusinovich, Gregory; Ireap Team

    2011-10-01

    In order to develop a system to detect concealed radioactive materials, we are designing a 670 GHz gyrotron with sufficient power to cause breakdown in the air. Design studies of the cavity and the magnetron injection gun (MIG) of this gyrotron had already been presented. We concluded study of simple start-up regime for this 670GHz gyrotron operating at TE31,8 mode and found that at the fundamental cyclotron harmonics, the operating mode can be excited and the competitor modes will be suppressed. Currently we are studying gyrotron operating on the second cyclotron harmonics using the same electron gun. Preliminary studies show that if the higher harmonics mode is excited first, it will suppress competitors of the fundamental mode. Using available MIG data, we are performing numerical simulation using MAGY. The results of these simulations can be illustrative for our future experiments, and the results of the study will be presented at the conference. Supported by ONR.

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

    NASA Astrophysics Data System (ADS)

    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.

  4. High efficiency coupling of radio frequency beams from the dual frequency gyrotron with a corrugated waveguide transmission system.

    PubMed

    Oda, Yasuhisa; Kajiwara, Ken; Takahashi, Koji; Mitsunaka, Yoshika; Sakamoto, Keishi

    2013-01-01

    High efficiency coupling of the millimeter-wave output of the dual-frequency gyrotron with the transmission line was demonstrated. The dual-frequency gyrotron was design to produce similar beam profiles for two operation frequencies (170 GHz and 137 GHz). Using two RF beam reflecting mirrors in a matching optics unit (MOU), which are designed to transform the beam profile of the gyrotron output to the fundamental waveguide mode (HE(11) mode) at 170 GHz, high efficiency coupling was demonstrated for two frequencies. The measured mode purity of HE(11) mode was 96% at 170 GHz and 94% at 137 GHz operations with the identical mirrors at the fixed mirror position and angle. The results indicate that the significantly simple dual frequency system is realized by the gyrotron designed to output the similar beam profiles at different frequency operation. PMID:23387644

  5. Gyrotron anode modulation of the Electron Cyclotron Resonant Heating (ECRH) from dc to 50 kHz on the Tandem Mirror Experiment-Upgrade (TMX-U)

    SciTech Connect

    Williams, C.W.; Heefner, J.W.; Rupert, R.R.

    1985-11-11

    This paper describes control of gyrotron microwave energy output by modulation of gyrotron anode voltage. At present, Electron Cyclotron Resonant Heating (ECRH) uses five gyrotrons on the Tandem Mirror Experiment-Upgrade (TMX-U) for plasma heating. One is in the 10 kG region of each end plug, one at the 5 kG region of each end plug, and one is used for central-cell heating. Also described are the design and operation of the anode modulation system. The operating advantages of gyrotron anode modulation include power balance, independent control of each gyrotron, an ability to modulate microwave output power up to 50 kHz, and gyrotron tuning. The performance results of anode modulation will be discussed. 9 figs.

  6. Phase-locking of a second-harmonic gyrotron oscillator using a quasi-optical circulator to separate injection and output signals

    SciTech Connect

    Guo, H.Z.; Rodgers, J.; Hoppe, D.J.

    1995-12-31

    Phase-locking in a 34.5 GHz special complex cavity gyrotron oscillator operating at the second harmonic of the electron cyclotron frequency was studied. Injection of the locking power was made via a quasi-optical circulator connected to the gyrotron output. Locking bandwidth was measured by comparing the phase of the injection signal and output signal using a balanced mixer. Locking was observed with input power level as low as 40 dB below the gyrotron output power. The locking bandwidth is, however, narrower than in gyrotrons operating at the fundamental cyclotron frequency which may be attributed to the longer resonant cavity in the second harmonic gyrotron and the corresponding larger value of external quality factor. The measurements are roughly in agreement with predictions of Adler`s phase-locking equation which is given for the system in terms of powers propagating in the output waveguide toward and away from the gyrotron cavity.

  7. Relativistic Harmonic Gyrotron Traveling-Wave Tube Amplifier Experiments.

    NASA Astrophysics Data System (ADS)

    Menninger, William Libbey

    1995-01-01

    The first multi-megawatt (4 MW, eta = 8%) harmonic (omega = sOmega _{c}, s = 2 or 3) relativistic gyrotron traveling-wave tube amplifier (gyro-twt) experiment has been designed, built, and tested. Results from this experimental setup, including the first ever reported third harmonic gyro-twt results, are presented. The first detailed phase measurements of a gyro-twt are also reported. The electron beam source is SNOMAD-II, a solid-state nonlinear magnetic accelerator driver with nominal parameters of 400 kV and 350 A. The flat-top pulse width is 30 ns. The electron beam is focused using a Pierce geometry and then imparted with transverse momentum using a bifilar helical wiggler magnet. The imparted beam pitch is alpha equivbeta_bot/beta_ |~1. Experimental operation involving both a second harmonic interaction with the TE_{21 } mode and a third harmonic interaction with the TE_{31} mode has been characterized. The third harmonic interaction resulted in 4 MW output power and 50 dB single-pass gain, with an efficiency of up to ~8% (for 115 A beam current). The best measured phase stability of the TE_{31} amplified pulse was +/-10^circ over a 9 ns period. The phase stability was limited because the maximum rf power was attained when operating far from wiggler resonance. The second harmonic, TE_ {21} had a peak amplified power of 2 MW corresponding to 40 dB single-pass gain and 4% efficiency. The second harmonic interaction showed stronger superradiant emission than the third harmonic interaction. Characterizations of the second and third harmonic gyro-twt experiments presented in this thesis include measurement of far-field radiation patterns, gain and phase versus interaction length, frequency spectrum, phase, and output power versus input power. The absolute power measurements are based both on angular radiation scans with a calibrated horn and diode, and on propagation of the TE_{31} mode through an efficient in-guide converter and measurement of the converted TE

  8. A portable CW/FM-CW Doppler radar for local investigation of severe storms

    SciTech Connect

    Unruh, W.P.; Wolf, M.A.; Bluestein, H.B.

    1988-01-01

    During the 1987 spring storm season we used a portable 1-W X-band CW Doppler radar to probe a tornado, a funnel cloud, and a wall cloud in Oklahoma and Texas. This same device was used during the spring storm season in 1988 to probe a wall cloud in Texas. The radar was battery powered and highly portable, and thus convenient to deploy from our chase vehicle. The device separated the receding and approaching Doppler velocities in real time and, while the radar was being used, it allowed convenient stereo data recording for later spectral analysis and operator monitoring of the Doppler signals in stereo headphones. This aural monitoring, coupled with the ease with which an operator can be trained to recognize the nature of the signals heard, made the radar very easy to operate reliably and significantly enhanced the quality of the data being recorded. At the end of the 1988 spring season, the radar was modified to include FM-CW ranging and processing. These modifications were based on a unique combination of video recording and FM chirp generation, which incorporated a video camera and recorder as an integral part of the radar. After modification, the radar retains its convenient portability and the operational advantage of being able to listen to the Doppler signals directly. The original mechanical design was unaffected by these additions. During the summer of 1988, this modified device was used at the Langmuir Laboratory at Socorro, New Mexico in an attempt to measure vertical convective flow in a thunderstorm. 2 refs., 2 figs.

  9. A portable CW/FM-CW Doppler radar for local investigation of severe storms

    NASA Astrophysics Data System (ADS)

    Unruh, Wesley P.; Wolf, Michael A.; Bluestein, Howard B.

    During the 1987 spring storm season we used a portable 1-W X-band CW Doppler radar to probe a tornado, a funnel cloud, and a wall cloud in Oklahoma and Texas. This same device was used during the spring storm season in 1988 to probe a wall cloud in Texas. The radar was battery powered and highly portable, and thus convenient to deploy from our chase vehicle. The device separated the receding and approaching Doppler velocities in real time and, while the radar was being used, it allowed convenient stereo data recording for later spectral analysis and operator monitoring of the Doppler signals in stereo headphones. This aural monitoring, coupled with the ease with which an operator can be trained to recognize the nature of the signals heard, made the radar very easy to operate reliably and significantly enhanced the quality of the data being recorded. At the end of the 1988 spring season, the radar was modified to include FM-CW ranging and processing. These modifications were based on a unique combination of video recording and FM chirp generation, which incorporated a video camera and recorder as an integral part of the radar. After modification, the radar retains its convenient portability and the operational advantage of being able to listen to the Doppler signals directly. The original mechanical design was unaffected by these additions. During the summer of 1988, this modified device was used at the Langmuir Laboratory at Socorro, New Mexico in an attempt to measure vertical convective flow in a thunderstorm.

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

    SciTech Connect

    Singh, Ashutosh; Jain, P. K.

    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.

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

    NASA Astrophysics Data System (ADS)

    Singh, Ashutosh; Jain, P. K.

    2015-09-01

    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.

  12. On the measurement of wind speeds in tornadoes with a portable CW/FM-CW Doppler radar

    SciTech Connect

    Bluestein, H.B. . School of Meteorology); Unruh, W.P. )

    1991-01-01

    Both the formation mechanism and structure of tornadoes are not yet well understood. The Doppler radar is probably the best remote-sensing instrument at present for determining the wind field in tornadoes. Although much has been learned about the non-supercell tornado from relatively close range using Doppler radars at fixed sites, close-range measurements in supercell tornadoes are relatively few. Doppler radar can increase significantly the number of high-resolution, sub-cloud base measurements of both the tornado vortex and its parent vortex in supercells, with simultaneous visual documentation. The design details and operation of the CW/FM-CW Doppler radar developed at the Los Alamos National Laboratory and used by storm-intercept teams at the Univ. of Oklahoma are described elsewhere. The radar transmits 1 W at 3 cm, and can be switched back and forth between CW and FM-CW modes. In the FM-CW mode the sweep repetition frequency is 15.575 kHz and the sweep width 1.9 MHz; the corresponding maximum unambiguous range and velocity, and range resolution are 5 km, {plus minus} 115 m s{sup {minus}1}, and 78 m respectively. The bistatic antennas, which have half-power beamwidths of 5{degree}, are easily pointed wit the aid of a boresighted VCR. FM-CW Data are recorded on the VCR, while voice documentation is recorded on the audio tape; video is recorded on another VCR. The radar and antennas are easily mounted on a tripod, and can be set up by three people in a minute or two. The purpose of this paper is to describe the signal processing techniques used to determine the Doppler spectrum in the FM-CW mode and a method of its interpretation in real time, and to present data gathered in a tornadic storm in 1990. 15 refs., 7 figs.

  13. Simple laboratory methods for quantitative IR measurements of CW agents

    NASA Astrophysics Data System (ADS)

    Puckrin, Eldon; Thériault, Jean-Marc; Lavoie, Hugo; Dubé, Denis; Lepage, Carmela J.; Petryk, Michael

    2005-11-01

    A simple method is presented for quantitatively measuring the absorbance of chemical warfare (CW) agents and their simulants in the vapour phase. The technique is based on a standard lab-bench FTIR spectrometer, 10-cm gas cell, a high accuracy Baratron pressure manometer, vacuum pump and simple stainless-steel hardware components. The results of this measurement technique are demonstrated for sarin (GB) and soman (GD). A second technique is also introduced for the passive IR detection of CW agents in an open- air path located in a fumehood. Using a modified open-cell with a pathlength of 45 cm, open-air passive infrared measurements have been obtained for simulants and several classical CW agents. Detection, identification and quantification results based on passive infrared measurements are presented for GB and the CW agent simulant, DMMP, using the CATSI sensor which has been developed by DRDC Valcartier. The open-cell technique represents a relatively simple and feasible method for examining the detection capability of passive sensors, such as CATSI, for CW agents.

  14. Saturation by Noise and CW Signals in SIS Mixers

    NASA Astrophysics Data System (ADS)

    Kerr, A. R.

    2002-03-01

    In ALMA Memo 321, Plambeck points out that saturation (gain compression) is likely to be a significant factor limiting the calibration accuracy of ALMA observations. In this paper, saturation by broadband noise and CW signals is analyzed for representative SIS receivers operating at different frequencies. Many SIS mixers in current use are expected to exhibit a significant degree of gain compression when connected to a room-temperature source. Previous analyses of saturation in SIS mixers have applied only to CW signals. To analyze saturation by noise, the statistics of the output voltage are derived from those of the input signal. A single constant, applicable to all SIS mixers, is determined experimentally by fitting the predicted CW gain compression curve to measured data.

  15. Time Shifted PN Codes for CW Lidar, Radar, and Sonar

    NASA Technical Reports Server (NTRS)

    Campbell, Joel F. (Inventor); Prasad, Narasimha S. (Inventor); Harrison, Fenton W. (Inventor); Flood, Michael A. (Inventor)

    2013-01-01

    A continuous wave Light Detection and Ranging (CW LiDAR) system utilizes two or more laser frequencies and time or range shifted pseudorandom noise (PN) codes to discriminate between the laser frequencies. The performance of these codes can be improved by subtracting out the bias before processing. The CW LiDAR system may be mounted to an artificial satellite orbiting the earth, and the relative strength of the return signal for each frequency can be utilized to determine the concentration of selected gases or other substances in the atmosphere.

  16. SRF cavities for CW option of Project X Linac

    SciTech Connect

    Solyak, N.; Gonin, I.; Khabiboulline, T.; Lunin, A.; Perunov, N.; Yakovlev, V.; /Fermilab

    2009-09-01

    Alternative option of Project X is based on the CW SC 2GeV Linac with the average current 1mA. Possible option of the CW Linac considered in the paper includes low energy part consisted of a few families SC Spoke cavities (from 2.5 MeV to 466 MeV) and high energy part consisted of 2 types of elliptical cavities (v/c=0.81 and v/c=1). Requirements and designed parameters of cavities are considered.

  17. cw passive mode locking of a Ti:sapphire laser

    SciTech Connect

    Sarukura, N.; Ishida, Y.; Nakano, H.; Yamamoto, Y. )

    1990-02-26

    cw passive mode locking of a Ti:sapphire laser is achieved with 1,1{prime}-dietyl-2,2{prime}-dicarbocyanine iodide as the saturable absorber dye, using a 5 {mu}m thin dye jet flow. The pulse width is 4.0 ps, which is almost the transform-limited pulse for the observed spectrum width. The output power is {similar to}50 mW, when it is pumped by a 5 W cw Ar laser, while the tuning range is 745--755 nm.

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

    NASA Astrophysics Data System (ADS)

    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.

  19. Amplification of picosecond pulses in a 140-GHz gyrotron-traveling wave tube.

    PubMed

    Kim, H J; Nanni, E A; Shapiro, M A; Sirigiri, J R; Woskov, P P; Temkin, R J

    2010-09-24

    An experimental study of picosecond pulse amplification in a gyrotron-traveling wave tube (gyro-TWT) has been carried out. The gyro-TWT operates with 30 dB of small signal gain near 140 GHz in the HE₀₆ mode of a confocal waveguide. Picosecond pulses show broadening and transit time delay due to two distinct effects: the frequency dependence of the group velocity near cutoff and gain narrowing by the finite gain bandwidth of 1.2 GHz. Experimental results taken over a wide range of parameters show good agreement with a theoretical model in the small signal gain regime. These results show that in order to limit the pulse broadening effect in gyrotron amplifiers, it is crucial to both choose an operating frequency at least several percent above the cutoff of the waveguide circuit and operate at the center of the gain spectrum with sufficient gain bandwidth. PMID:21230783

  20. Formation of a laminar electron flow for 300 GHz high-power pulsed gyrotron

    SciTech Connect

    Yamaguchi, Yuusuke; Tatematsu, Yoshinori; Saito, Teruo; Ikeda, Ryosuke; Mudiganti, Jagadish C.; Ogawa, Isamu; Idehara, Toshitaka

    2012-11-15

    This paper describes the design of a triode magnetron injection gun for use in a 200 kW, 300 GHz gyrotron. As power and frequency increase, the performance of the gyrotron becomes quite sensitive to the quality of the electron beam. Formation of a laminar electron flow is essential for the realization of a high quality beam with a small velocity spread. In this study, a new method is developed for a quantitative evaluation of the laminarity and is applied to optimize the electrode design. The laminarity depends not only on conventional design parameters such as the cathode slant angle but also on the spatial distribution of the electric field along the beam trajectory. In the optimized design, the velocity pitch factors, {alpha}, larger than 1.2 are obtained at 65 kV, 10 A with spreads, {Delta}{alpha}, less than 5%.

  1. Design of 84 GHz 500 kW Gyrotron for Technological Millimeter Wave Applications

    NASA Astrophysics Data System (ADS)

    Singh, Udaybir; Kumar, Nitin; Kumar, Anil; Purohit, L. P.; Sinha, A. K.

    2011-04-01

    In this paper, the design and the numerical simulation of the 84 GHz, 500 kW gyrotron at first harmonic operation for technological applications is described. The operating mode of the gyrotron is TE10, 4. Various in-house developed and commercially available computer codes are used for the design purpose. The triode-type magnetron injection gun with the accelerating voltage 70-kV, the beam current 10-A and the maximum transverse velocity spread less than 5% is designed. The preliminary design is obtained by using some trade-off equations. The mode selection, the cold cavity and the beam-wave interaction analysis are discussed for the design of weakly tapered open resonator type of the interaction cavity. The parametric analysis of the interaction cavity and the electron gun is also presented.

  2. Design of Electron Gun for 1.5 MW, 140 GHz Gyrotron

    NASA Astrophysics Data System (ADS)

    Singh, Udaybir; Kumar, Nitin; Purohit, L. P.; Sinha, A. K.

    2011-02-01

    This paper presents the design of the triode type electron gun for a 140 GHz, 1.5 MW gyrotron with the transverse to the axial velocity ratio of the beam 1.4 and the transverse velocity spread 1.28%. The operating mode of the gyrotron is TE24,8 and it is operated in the fundamental harmonic. The analytic trade-off equations for the electron gun design have been used to estimate the initial gun parameters. The electron trajectory tracing program has been used to optimize the electron gun design. The parametric dependences of modulating anode voltage, beam voltage and cathode magnetic field on the beam quality has also been studied.

  3. Theoretical study on a 0.6 THz third harmonic gyrotron

    NASA Astrophysics Data System (ADS)

    Yuan, Xuesong; Lan, Ying; Ma, Chunyan; Han, Yu; Yan, Yang

    2011-10-01

    A theoretical study on a 0.6 THz third harmonic TE37 mode gyrotron oscillator is reported in this paper in order to develop a compact, reliable, and high power terahertz radiation source. An output power of 4 kW can be generated in the TE37 mode (0.6 THz) at a resonant magnetic field of 7.86 T by the gyrotron oscillator operating at 55 kV/2 A with an electron beam radius of 0.32 mm. A magnetron injection gun (MIG) with high compression ratio has been designed. The simulation results of MIG show that the velocity ratio α is 1.37, and the perpendicular velocity spread and parallel velocity spread are 6.1% and 8.9%, respectively.

  4. Formation of a laminar electron flow for 300 GHz high-power pulsed gyrotron

    NASA Astrophysics Data System (ADS)

    Yamaguchi, Yuusuke; Tatematsu, Yoshinori; Saito, Teruo; Ikeda, Ryosuke; Mudiganti, Jagadish C.; Ogawa, Isamu; Idehara, Toshitaka

    2012-11-01

    This paper describes the design of a triode magnetron injection gun for use in a 200 kW, 300 GHz gyrotron. As power and frequency increase, the performance of the gyrotron becomes quite sensitive to the quality of the electron beam. Formation of a laminar electron flow is essential for the realization of a high quality beam with a small velocity spread. In this study, a new method is developed for a quantitative evaluation of the laminarity and is applied to optimize the electrode design. The laminarity depends not only on conventional design parameters such as the cathode slant angle but also on the spatial distribution of the electric field along the beam trajectory. In the optimized design, the velocity pitch factors, α, larger than 1.2 are obtained at 65 kV, 10 A with spreads, Δα, less than 5%.

  5. Design of 132 GHz gyrotron with 3 GHz tunability for 200 MHz DNP/NMR spectrometer

    NASA Astrophysics Data System (ADS)

    Kumar, Nitin; Singh, Udaybir; Sinha, Ashok Kumar

    2015-01-01

    A complete design of 132 GHz gyrotron for 200 MHz DNP-NMR spectroscopy application is presented in this article. The design is performed considering a frequency tunability range of 3 GHz and output power around 100 W. A smooth frequency tunability is achieved via the excitation of TE03p modes (p = 1-6) through the variation of cavity magnetic field. The start oscillation current calculation is performed to estimate the required magnetic field for each TE03p mode. Cold cavity analysis and beam-wave interaction computation are carried out for the estimation of quality factor, resonant frequency corresponding to each TE03p mode, axial electric field profile and output power. Other important components of gyrotron such as magnetron injection gun, non-linear taper and RF window are also designed considering the smooth frequency tunability a main design parameter.

  6. Numerical Simulation of a Double-anode Magnetron Injection Gun for 110 GHz, 1 MW Gyrotron

    NASA Astrophysics Data System (ADS)

    Singh, Udaybir; Kumar, Nitin; Purohit, L. P.; Sinha, Ashok K.

    2010-07-01

    A 40 A double-anode magnetron injection gun for a 1 MW, 110 GHz gyrotron has been designed. The preliminary design has been obtained by using some trade-off equations. The electron beam analysis has been performed by using the commercially available code EGUN and the in-house developed code MIGANS. The operating mode of the gyrotron is TE22,6 and it is operated in the fundamental harmonic. The electron beam with a low transverse velocity spread ( δ {β_{ bot max }} = 2.26% ) and the transverse-to-axial velocity ratio of the electron beam (α) = 1.37 is obtained. The simulated results of the MIG obtained with the EGUN code have been validated with another trajectory code TRAK. The results on the design output parameters obtained by both the codes are in good agreement. The sensitivity analysis has been carried out by changing the different gun parameters to decide the fabrication tolerance.

  7. Formation of Laminar Electron Flow for a High-Power Sub-THz Gyrotron

    NASA Astrophysics Data System (ADS)

    Yamaguchi, Yuusuke; Tatematsu, Yoshinori; Saito, Teruo; Ikeda, Ryosuke; Mudiganti, Jagadish C.; Ogawa, Isamu; Idehara, Toshitaka

    This paper describes the design of a magnetron-injection gun for a 100 kW, 300 GHz gyrotron. With an increase in power and frequency, performance of the gyrotron becomes quite sensitive to the quality of the electron beam. Formation of a laminar electron flow is essential for the realization of a high quality beam with small velocity spread. In this study, a new method is proposed for the evaluation of the laminarity, and applied to the design optimization of the electrodes. It is found that the laminarity depends not only on the conventional design parameter of the cathode slant angle, but also on the spatial distribution of the electric field inside the beam.

  8. Theoretical study on a 0.6 THz third harmonic gyrotron

    SciTech Connect

    Yuan Xuesong; Ma Chunyan; Han Yu; Yan Yang; Lan Ying

    2011-10-15

    A theoretical study on a 0.6 THz third harmonic TE{sub 37} mode gyrotron oscillator is reported in this paper in order to develop a compact, reliable, and high power terahertz radiation source. An output power of 4 kW can be generated in the TE{sub 37} mode (0.6 THz) at a resonant magnetic field of 7.86 T by the gyrotron oscillator operating at 55 kV/2 A with an electron beam radius of 0.32 mm. A magnetron injection gun (MIG) with high compression ratio has been designed. The simulation results of MIG show that the velocity ratio {alpha} is 1.37, and the perpendicular velocity spread and parallel velocity spread are 6.1% and 8.9%, respectively.

  9. Suppression criteria of parasitic mode oscillations in a gyrotron beam tunnel

    NASA Astrophysics Data System (ADS)

    Kumar, Nitin; Singh, Udaybir; Singh, T. P.; Sinha, A. K.

    2011-02-01

    This paper presents the design criteria of the parasitic mode oscillations suppression for a periodic, ceramic, and copper loaded gyrotron beam tunnel. In such a type of beam tunnel, the suppression of parasitic mode oscillations is an important design problem. A method of beam-wave coupling coefficient and its mathematical formulation are presented. The developed design criteria are used in the beam tunnel design of a 42 GHz gyrotron to be developed for the Indian TOKAMAK system. The role of the thickness and the radius of the beam tunnel copper rings to obtain the developed design criteria are also discussed. The commercially available electromagnetic code CST and the electron trajectory code EGUN are used for the simulations.

  10. Amplification of Picosecond Pulses in a 140-GHz Gyrotron-Traveling Wave Tube

    PubMed Central

    Kim, H. J.; Nanni, E. A.; Shapiro, M. A.; Sirigiri, J. R.; Woskov, P. P.; Temkin, R. J.

    2011-01-01

    An experimental study of picosecond pulse amplification in a gyrotron-traveling wave tube (gyro-TWT) has been carried out. The gyro-TWT operates with 30 dB of small signal gain near 140 GHz in the HE06 mode of a confocal waveguide. Picosecond pulses show broadening and transit time delay due to two distinct effects: the frequency dependence of the group velocity near cutoff and gain narrowing by the finite gain bandwidth of 1.2 GHz. Experimental results taken over a wide range of parameters show good agreement with a theoretical model in the small signal gain regime. These results show that in order to limit the pulse broadening effect in gyrotron amplifiers, it is crucial to both choose an operating frequency at least several percent above the cutoff of the waveguide circuit and operate at the center of the gain spectrum with sufficient gain bandwidth. PMID:21230783

  11. Generation of high charge state platinum ions on vacuum arc plasma heated by gyrotron radiation.

    PubMed

    Yushkov, G Yu; Vodopyanov, A V; Nikolaev, A G; Izotov, I V; Savkin, K P; Golubev, S V; Oks, E M

    2014-02-01

    The hybrid high charge metal ion source based on vacuum arc plasma heated by gyrotron radiation into simple magnetic trap has been developed. Two types of magnetic traps were used: a mirror configuration and a cusp one with inherent "minimum-B" structure. Pulsed high power (>100 kW) gyrotrons with frequency 37.5 GHz and 75 GHz were used for heating the vacuum arc plasma injected into the traps. Two different ways were used for injecting the metal plasma-axial injection by a miniature arc source located on-axis near the microwave window, and simultaneous radial injection by a number of sources mounted radially at the midplane of the traps. This article represents all data gathered for platinum ions, thus making comparison of the experimental results obtained with different traps and injections convenient and accurate. PMID:24593607

  12. Spectroscopic temperature measurements of air breakdown plasma using a 110 GHz megawatt gyrotron beam

    SciTech Connect

    Hummelt, J. S.; Shapiro, M. A.; Temkin, R. J.

    2012-12-15

    Temperature measurements are presented of a non-equilibrium air breakdown plasma using optical emission spectroscopy. A plasma is created with a focused 110 GHz 3 {mu}s pulse gyrotron beam in air that produces power fluxes exceeding 1 MW/cm{sup 2}. Rotational and vibrational temperatures are spectroscopically measured over a pressure range of 1-100 Torr as the gyrotron power is varied above threshold. The temperature dependence on microwave field as well as pressure is examined. Rotational temperature measurements of the plasma reveal gas temperatures in the range of 300-500 K and vibrational temperatures in the range of 4200-6200 K. The vibrational and rotational temperatures increase slowly with increasing applied microwave field over the range of microwave fields investigated.

  13. Suppression criteria of parasitic mode oscillations in a gyrotron beam tunnel

    SciTech Connect

    Kumar, Nitin; Singh, Udaybir; Sinha, A. K.; Singh, T. P.

    2011-02-15

    This paper presents the design criteria of the parasitic mode oscillations suppression for a periodic, ceramic, and copper loaded gyrotron beam tunnel. In such a type of beam tunnel, the suppression of parasitic mode oscillations is an important design problem. A method of beam-wave coupling coefficient and its mathematical formulation are presented. The developed design criteria are used in the beam tunnel design of a 42 GHz gyrotron to be developed for the Indian TOKAMAK system. The role of the thickness and the radius of the beam tunnel copper rings to obtain the developed design criteria are also discussed. The commercially available electromagnetic code CST and the electron trajectory code EGUN are used for the simulations.

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

    NASA Astrophysics Data System (ADS)

    Ginzburg, N. S.; Sergeev, A. S.; Zotova, I. V.; Zheleznov, I. V.

    2015-01-01

    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.

  15. Gyrotron collective Thomson scattering from plasma fluctuations in a Tara axicell

    SciTech Connect

    Machuzak, J.S.; Woskov, P.P.; Myer, R.C.; Mulligan, W.J.; Cohn, D.R.; Gerver, M.; Golovato, S.N.; Horne, S.; Kubota, S.; Post, R.S.; and others

    1988-08-01

    Collective Thomson scattering in the Tara Tandem Mirror axicell at MIT was accomplished with a 137-GHz, approx.0.4-kW, 75-ms pulsed gyrotron. Ion cyclotron waves, ion Bernstein wave harmonics, and other plasma fluctuations possibly due to microinstabilities and magnetohydrodynamic (MHD) activity have been observed during ion cyclotron resonance frequency (ICRF) heating. The observation of ion Bernstein waves may be due to an enhanced ion thermal fluctuation spectrum in an ICRF heated plasma.

  16. Evaluation of Cathode Heater Assembly for 42 GHz, 200 kW Gyrotron

    NASA Astrophysics Data System (ADS)

    Sharma, S. K.; Singh, Narendra Kumar; Singh, Udaybir; Khatun, Hasina; Kumar, Nitin; Alaria, M. K.; Raju, R. S.; Jain, P. K.; Sinha, A. K.

    2014-09-01

    In this paper, the evaluation of cathode-heater assembly of magnetron injection gun (MIG) for 42 GHz, 200 kW gyrotron is presented. The cathode-heater assembly is purchased from M/S SEMICON.The cathode-heater assembly is experimentally studied in three different conditions; in a belljar system, during vacuum processing of MIG and during MIG testing to ensure the required rise of cathode surface temperature for pre-set heater power.

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

    SciTech Connect

    Ginzburg, N. S.; Sergeev, A. S.; Zotova, I. V.; Zheleznov, I. V.

    2015-01-15

    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.

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

    SciTech Connect

    Wang, Qiushi Peng, Shuyuan; Luo, Jirun

    2014-08-15

    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 TE{sub 01} 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.

  19. Experimental Studies of sub-THz Gyrotron with Pulsed Solenoid for Air Breakdown Investigation

    NASA Astrophysics Data System (ADS)

    Kashyn, Dmytro; Nusinovich, Gregory; Rodgers, John; Romero-Talamás, Carlos; Shkvarunets, Anatoly

    2012-10-01

    The development of sub-THz gyrotron for air breakdown studies is one of the research tasks under the Center of Applied Electromagnetics program in University of Maryland. The goal is to remotely detect concealed radioactive materials as described by V. L. Granatstein and G. S. Nusinovich (J. Appl. Phys 108 063304 (2010)). There it was proposed to focus high-power sub-THz radiation in a small volume where the wave field exceeds the breakdown threshold. The presence of the radioactive material in the vicinity (<= 20-40m) of such volume significantly increases the probability of the air breakdown. The gyrotron can serve as a source of sub THz radiation required for this scheme. We report our experimental activities on the sub-THz gyrotron operating at 670 GHz at TE 31,8 mode with 28T pulsed magnetic field. This tube was developed in collaboration with Institute of Applied Physics of Russian Academy of Science. Our team was responsible for the design of major components while our colleagues manufactured the tube. We achieved 80 kW of output power in 10μs pulses which corresponds to 0.2 J of energy. We introduced several improvements to the original design addressing the issues with discharges and multipactoring that were impeding the performance of the tube. Unfortunately we had a catastrophic failure which ruined the existing device. We are now working on the design of another gyrotron that will operate at 220 GHz and can be capable of delivering 250-350 kW of RF power.

  20. Cold cavity analysis for 35 GHz gyrotron interaction cavity using free space method

    SciTech Connect

    Kumar, Nitin; Saran, Sudeep; Singh, Udaybir; Yadav, Vivek; Sinha, Ashok K.; Jha, B.; Jain, P.K.; Singh, T.P.

    2011-07-01

    The interaction cavity simulated, designed and fabricated for the 35 GHz gyrotron is verified experimentally. Free space method for the Q value and resonant frequency measurement is used in the experiments. The WR22 waveguide based antenna system, Agilent Vector Network Analyzer are used as the experimental set-up in the cavity measurement. The simulation results for the same cavity are also obtained by using the electromagnetic simulator MAGIC for the comparison. (author)

  1. Frequency and phase stabilization of a multimode gyrotron with megawatt power by an external signal

    NASA Astrophysics Data System (ADS)

    Bakunin, V. L.; Denisov, G. G.; Novozhilova, Yu. V.

    2014-05-01

    We have numerically studied capturing of the oscillation frequency and phase of the TE28.12 operating mode by an external monochromatic signal for a multimode gyrotron with a close to real regime of activation. It is shown that, even at a low external-signal power, in a wide range of the magnetic field and voltage, a highly efficient single-mode generating is set at the frequency of the external signal.

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

    SciTech Connect

    Nusinovich, Gregory S.; Pu, Ruifeng; Granatstein, Victor L.

    2015-07-06

    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 TE{sub 31,8}-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 TE{sub 31,8}-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 TE{sub 31,8} mode is possible with only modest sacrifice of efficiency and power.

  3. Towards a 1 MW, 170 GHz gyrotron design for fusion application

    NASA Astrophysics Data System (ADS)

    Kumar, Anil; Kumar, Nitin; Singh, Udaybir; Bhattacharya, Ranajoy; Yadav, Vivek; Sinha, A. K.

    2013-03-01

    The electrical design of different components of 1 MW, 170 GHz gyrotron such as, magnetron injection gun, cylindrical interaction cavity and collector and RF window is presented in this article. Recently, a new project related to the development of 170 GHz, 1 MW gyrotron has been started for the Indian Tokamak. TE34,10 mode is selected as the operating mode after studied the problem of mode competition. The triode type geometry is selected for the design of magnetron injection gun (MIG) to achieve the required beam parameters. The maximum transverse velocity spread of 3.28% at the velocity ratio of 1.34 is obtained in simulations for a 40 A, 80 kV electron beam. The RF output power of more than 1 MW with 36.5% interaction efficiency without depressed collector is predicted by simulation in single-mode operation at 170 GHz frequency. The simulated single-stage depressed collector of the gyrotron predicted the overall device efficiencies >55%. Due to the very good thermal conductivity and very weak dependency of the dielectric parameters on temperature, PACVD diamond is selected for window design for the transmission of RF power. The in-house developed code MIGSYN and GCOMS are used for initial geometry design of MIG and mode selection respectively. Commercially available simulation tools MAGIC and ANSYS are used for beam-wave interaction and mechanical analysis respectively.

  4. NRL quasioptical gyrotron program. Final report, November 1, 1991--October 31, 1993

    SciTech Connect

    Fliflet, A.

    1997-06-01

    The quasioptical gyrotron (QOG) has been under development as a high power, tunable source for tokamak plasma heating applications. Given the critical importance of source efficiency for large-scale ESCH applications, understanding the causes of the low QOG efficiency and finding ways of improving it became a top priority for the current NRL program. The importance of the present work is that is represents new insight into the factors controlling the efficiency of quasioptical gyrotrons. The author has demonstrated that the technique of mode priming provides a method for improving efficiency via enhanced mode detuning and leads to more stable single-mode operation of highly over-moded resonators. The latter feature is an important consideration for output coupler and rf transmission system optimization and can make the QOG less sensitive to external influences such as window reflections. He has shown that a prebunching resonator is readily implemented in the quasioptical configuration. It is relatively free of the problems of spurious modes and cross-talk which plague over-moded prebunching cavities in conventional gyrotrons. The observation of almost 18% efficiency represents a doubling of the previous best single-mode results. Further improvements are expected from the optimization of start-up conditions and the study of the effects of the second harmonic interaction.

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

    NASA Astrophysics Data System (ADS)

    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).

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

    NASA Astrophysics Data System (ADS)

    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.

  7. Development of THz-range Gyrotrons for Detection of Concealed Radioactive Materials

    NASA Astrophysics Data System (ADS)

    Nusinovich, Gregory S.; Pu, Ruifeng; Antonsen, Thomas M.; Sinitsyn, Oleksandr V.; Rodgers, John; Mohamed, Ali; Silverman, Joseph; Al-Sheikhly, Mohamad; Dimant, Yakov S.; Milikh, Gennady M.; Glyavin, Michael Yu.; Luchinin, Alexei G.; Kopelovich, Eugene A.; Granatstein, Victor L.

    2011-03-01

    The Center for Applied Electromagnetics (AppEl) at the University of Maryland had started development of a sub-THz gyrotron for detecting concealed radioactive materials. The concept is based on the use of a high-power gyrotron whose power being focused in a small spot with dimensions on the order of a wavelength exceeds the threshold level required for initiating a freely localized microwave breakdown in air. However, in the absence of radioactive materials, the ambient electron density is so small that there is a very small probability to find a free electron in this small volume to trigger the avalanche breakdown process. Therefore the fact that the breakdown was observed would indicate that there is a hidden radioactive material in the vicinity of a focused wave beam. We present the design data for a 200-300 kW, 670 GHz gyrotron operating with a pulsed solenoid and describe a single-shot pulsed solenoid producing 27-28 T magnetic fields. Also numerous issues in this specific application are discussed, viz. threshold conditions for initiating the breakdown, production of gamma rays by concealed radioactive materials and their role in producing low energy electrons outside a container, wave beam focusing in a small spot by a limited-size antenna, random walk of energetic electrons which may result in appearance of free electrons in a given volume during the RF pulse and comparison of diffusion time with the time required for competing processes, such as ionization and three-body attachment.

  8. Nonlinear optical properties of methyl red under CW irradiation

    NASA Astrophysics Data System (ADS)

    Zheng, Yu; Ye, Qing; Wang, Chen; Wang, Jin; Deng, Zhichao; Mei, Jianchun; Zhou, Wenyuan; Zhang, Chunping; Tian, Jianguo

    2015-12-01

    Organic materials have wide potential application in nonlinear optical devices. The nonlinear optical (NLO) properties of methyl red (MR) doped polymethyl methacrylate (MR-PMMA) are investigated under CW laser irradiation at 473 nm, 532 nm and 632.8 nm, respectively. By combining Kramers-Kronig (K-K) relation and CW Z-scan technique, the effective refractive index n2 and the change of refractive index Δn are obtained under different scanning speed at 473 nm and 532 nm. Δn is positive at 473 nm, while Δn is negative at 532 nm. The experimental result is consistent with that of K-K relation. With the scanning speed decreasing, the NLO properties of MR-PMMA are enhanced. With different laser powers at 632.8 nm, MR-PMMA has only nonlinear absorption rather than nonlinear refraction. Meanwhile, the sample is investigated under pulse laser irradiation at 532 nm. Through the comparison of results of CW Z-scan and pulse Z-scan, the influence of the cumulative thermal effect on NLO properties of material is investigated. The results indicate that, under CW irradiation near the absorption peak wavelength, the cumulative thermal effect has great influence to the NLO properties of MR-PMMA.

  9. Investigations of atmospheric dynamics using a CW Doppler sounder array

    NASA Technical Reports Server (NTRS)

    Rao, G. L.

    1974-01-01

    A three-dimensional CW Doppler sounding system currently under operation at the NASA-Marshall Space Flight Center, Alabama is described. The properties of the neutral atmosphere are discussed along with the theory of Doppler sounding technique. Methods of data analyses used to investigate the dynamical phenomena at the ionospheric heights are presented and suggestions for future investigations provided.

  10. Applications of KHZ-CW Lidar in Ecological Entomology

    NASA Astrophysics Data System (ADS)

    Malmqvist, Elin; Brydegaard, Mikkel

    2016-06-01

    The benefits of kHz lidar in ecological entomology are explained. Results from kHz-measurements on insects, carried out with a CW-lidar system, employing the Scheimpflug principle to obtain range resolution, are presented. A method to extract insect events and analyze the large amount of lidar data is also described.

  11. CW-FIT: Group Contingency Effects across the Day

    ERIC Educational Resources Information Center

    Wills, Howard P.; Iwaszuk, Wendy M.; Kamps, Debra; Shumate, Emily

    2014-01-01

    This study explored the effects of a group-contingency intervention on student behavior across academic instructional periods. Research suggests group contingencies are evidence-based practices, yet calls for investigation to determine the best conditions and groups suited for this type of intervention. CW-FIT (Class-Wide Function-related…

  12. Cascaded combiners for a high power CW fiber laser

    NASA Astrophysics Data System (ADS)

    Tan, Qirui; Ge, Tingwu; Zhang, Xuexia; Wang, Zhiyong

    2016-02-01

    We report cascaded combiners for a high power continuous wave (CW) fiber laser in this paper. The cascaded combiners are fabricated with an improved lateral splicing process. During the fusing process, there is no stress or tension between the pump fiber and the double-cladding fiber. Thus, the parameters of the combiner are better than those that have been reported. The coupling efficiency is 98.5%, and the signal insertion loss is 1%. The coupling efficiency of the cascaded combiners is 97.5%. The pump lights are individually coupled into the double-cladding fiber via five combiners. The thermal effects cannot cause damage to the combiners and the cascaded combiners can operate stably in high power CW fiber lasers. We also develop a high power CW fiber laser that generates a maximum 780 W of CW signal power at 1080 nm with 71% optical-to-optical conversion efficiency. The fiber laser is pumped via five intra-cavity cascaded combiners and five extra-cavity cascaded combiners with a maximum pump power of 1096 W and a pump wavelength of 975 nm.

  13. Experimental atomic scale investigation of irradiation effects in CW 316SS and UFG-CW 316SS

    NASA Astrophysics Data System (ADS)

    Pareige, P.; Etienne, A.; Radiguet, B.

    2009-06-01

    Materials of the core internals of pressurized water reactor (austenitic stainless steels) are subject to neutron irradiation. To understand the ageing mechanisms associated with irradiation and propose life predictions of components or develop new materials, irradiation damage needs to be experimentally investigated. Atomic scale investigation of a neutron-irradiated CW316 SS with the laser pulsed atom probe gives a detailed description of the solute segregation in the austenitic grains. In order to understand the mechanism of solute segregation detected in the neutron-irradiated materials, ion irradiations were performed. These latest irradiations were realized on a CW 316SS as well as on a nanostructured CW 316SS. The study of irradiation effects in a nanograin material allows first, to easily analyse grain boundary segregation and second, to test the behaviour under irradiation of a new nanostructured material. The three aspects of this atomic scale investigation (neutron irradiation effect, model ion irradiation, new nanostructured CW 316 SS) are tackled in this paper.

  14. 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

    SciTech Connect

    Dumbrajs, O.; Avramidis, K. A.; Franck, J.; Jelonnek, J.

    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.

  15. 500-fold enhancement of in situ 13C liquid state NMR using gyrotron-driven temperature-jump DNP

    NASA Astrophysics Data System (ADS)

    Yoon, Dongyoung; Soundararajan, Murari; Caspers, Christian; Braunmueller, Falk; Genoud, Jérémy; Alberti, Stefano; Ansermet, Jean-Philippe

    2016-09-01

    A 550-fold increase in the liquid state 13C NMR signal of a 50 μL sample was obtained by first hyperpolarizing the sample at 20 K using a gyrotron (260 GHz), then, switching its frequency in order to apply 100 W for 1.5 s so as to melt the sample, finally, turning off the gyrotron to acquire the 13C NMR signal. The sample stays in its NMR resonator, so the sequence can be repeated with rapid cooling as the entire cryostat stays cold. DNP and thawing of the sample are performed only by the switchable and tunable gyrotron without external devices. Rapid transition from DNP to thawing in one second time scale was necessary especially in order to enhance liquid 1H NMR signal.

  16. A double-beam magnetron-injection gun for third-harmonic continuous wave 1-THz gyrotron

    NASA Astrophysics Data System (ADS)

    Glyavin, M.; Manuilov, V.; Idehara, T.

    2013-12-01

    The concept of a continuous wave 1-kW/1-THz gyrotron operated at the third cyclotron harmonic of the transverse electric TE9,7 operating mode has been developed. To suppress the mode competition effects in a terahertz gyrotron, we propose a scheme with two generating helical electron beams (HEBs) formed in a double-beam triode magnetron-injection gun (MIG), where both emitters of the electron beams are located on a common cathode of the conventional MIG. An optimal geometry of the MIG electrodes is found. It is shown that in a proposed scheme two HEBs having close pitch factors and a moderate velocity spread can be formed. This makes them suitable for high-efficiency single-mode generation in the high frequency gyrotron at high harmonic.

  17. A double-beam magnetron-injection gun for third-harmonic continuous wave 1-THz gyrotron

    SciTech Connect

    Glyavin, M.; Manuilov, V.; Idehara, T.

    2013-12-15

    The concept of a continuous wave 1-kW/1-THz gyrotron operated at the third cyclotron harmonic of the transverse electric TE{sub 9,7} operating mode has been developed. To suppress the mode competition effects in a terahertz gyrotron, we propose a scheme with two generating helical electron beams (HEBs) formed in a double-beam triode magnetron-injection gun (MIG), where both emitters of the electron beams are located on a common cathode of the conventional MIG. An optimal geometry of the MIG electrodes is found. It is shown that in a proposed scheme two HEBs having close pitch factors and a moderate velocity spread can be formed. This makes them suitable for high-efficiency single-mode generation in the high frequency gyrotron at high harmonic.

  18. 500-fold enhancement of in situ (13)C liquid state NMR using gyrotron-driven temperature-jump DNP.

    PubMed

    Yoon, Dongyoung; Soundararajan, Murari; Caspers, Christian; Braunmueller, Falk; Genoud, Jérémy; Alberti, Stefano; Ansermet, Jean-Philippe

    2016-09-01

    A 550-fold increase in the liquid state (13)C NMR signal of a 50μL sample was obtained by first hyperpolarizing the sample at 20K using a gyrotron (260GHz), then, switching its frequency in order to apply 100W for 1.5s so as to melt the sample, finally, turning off the gyrotron to acquire the (13)C NMR signal. The sample stays in its NMR resonator, so the sequence can be repeated with rapid cooling as the entire cryostat stays cold. DNP and thawing of the sample are performed only by the switchable and tunable gyrotron without external devices. Rapid transition from DNP to thawing in one second time scale was necessary especially in order to enhance liquid (1)H NMR signal. PMID:27490302

  19. Cold testing of quasi-optical mode converters using a generator for non-rotating high-order gyrotron modes.

    PubMed

    Kim, S G; Kim, D S; Choe, M S; Lee, W; So, J; Choi, E M

    2014-10-01

    In this paper, we test the performance of a quasi-optical, internal-gyrotron mode converter. When cold testing mode converters, a rotating higher-order mode is commonly used. However, this requires a nontrivial design and precise alignment. We thus propose a new technique for testing gyrotron mode converters by using a simple, non-rotating, higher-order mode generator. We demonstrate the feasibility of this technique for a W-band gyrotron quasi-optical mode converter by examining the excitation of a TE6,2 mode from a non-rotating mode generator. Our results demonstrate that this new cold-test scheme is an easy and efficient method for verifying the performance of quasi-optical mode converters. PMID:25362436

  20. Modeling of cw OIL energy performance based on similarity criteria

    NASA Astrophysics Data System (ADS)

    Mezhenin, Andrey V.; Pichugin, Sergey Y.; Azyazov, Valeriy N.

    2012-01-01

    A simplified two-level generation model predicts that power extraction from an cw oxygen-iodine laser (OIL) with stable resonator depends on three similarity criteria. Criterion τd is the ratio of the residence time of active medium in the resonator to the O2(1Δ) reduction time at the infinitely large intraresonator intensity. Criterion Π is small-signal gain to the threshold ratio. Criterion Λ is the relaxation to excitation rate ratio for the electronically excited iodine atoms I(2P1/2). Effective power extraction from a cw OIL is achieved when the values of the similarity criteria are located in the intervals: τd=5-8, Π=3-8 and Λ<=0.01.

  1. Absorption line CW EPR using an amplitude modulated longitudinal field.

    PubMed

    Fedin, Matvey; Gromov, Igor; Schweiger, Arthur

    2004-11-01

    In standard continuous wave electron paramagnetic resonance (CW-EPR) experiments, the first derivative of absorption lines is detected. This type of a line shape is caused by the magnetic field modulation and is usually an undesired feature, since the sensitivity of CW-EPR drastically decreases with increasing linewidth. A new approach is introduced, which allows for the measurement of absorption line EPR spectra in systems with broad inhomogeneous lines. The method makes use of multiple-photon transitions that are induced in spin systems when a transverse microwave and a longitudinal radio frequency field are simultaneously applied. The absorption lines are obtained by using amplitude modulation of the radio frequency field and slight saturation of the spectral lines. The basics of the new approach are discussed and experimental examples are given. PMID:15504685

  2. PROSPECTS FOR A VERY HIGH POWER CW SRF LINAC

    SciTech Connect

    Robert Rimmer

    2010-06-01

    Steady development in SRF accelerator technology combined with the success of large scale installations such as CEBAF at Jefferson Laboratory and the SNS Linac at ORNL gives credibility to the concept of very high average power CW machines for light sources or Proton drivers. Such machines would be powerful tools for discovery science in themselves but could also pave the way to reliable cost effective drivers for such applications as neutrino factories, an energy-frontier muon collider, nuclear waste transmutation or accelerator driven subcritical reactors for energy production. In contrast to machines such as ILC that need maximum accelerating gradient, the challenges in these machines are mainly in efficiency, reliability, beam stability, beam loss and of course cost. In this paper the present state of the art is briefly reviewed and options for a multi-GeV, multi-MW CW linac are discussed.

  3. Computationally efficient, rotational nonequilibrium CW chemical laser model

    SciTech Connect

    Sentman, L.H.; Rushmore, W.

    1981-10-01

    The essential fluid dynamic and kinetic phenomena required for a quantitative, computationally efficient, rotational nonequilibrium model of a CW HF chemical laser are identified. It is shown that, in addition to the pumping, collisional deactivation, and rotational relaxation reactions, F-atom wall recombination, the hot pumping reaction, and multiquantum deactivation reactions play a significant role in determining laser performance. Several problems with the HF kinetics package are identified. The effect of various parameters on run time is discussed.

  4. The eclipsing binary CW Eridani. [three-color photoelectric observation

    NASA Technical Reports Server (NTRS)

    Chen, K.-Y.

    1975-01-01

    Results of three-color photoelectric observations of CW Eridani are presented which were made with a 30-inch telescope over the three-year period from 1970 to 1973. The times of minima are computed, solutions of the light curves are obtained, and theoretical light curves are computed from the solutions. The period is determined to be 2.72837 days, and the orbital and photoelectric elements are derived from solutions based on the idealized Russell model.

  5. Low threshold CW Nc laser oscillator at 1060 nm study

    NASA Technical Reports Server (NTRS)

    Birnbaum, M.; Deshazer, L. G.

    1976-01-01

    A broad range of characteristics of neodymium/yag lasers were investigated. With Nd:YVO4 crystals, CW 1.06 mu lasers were operated with thresholds a factor of 2 lower than Nd:YAG and with greater slope efficiencies. Thus, the first step in the development of new oscillators suitable for application in high data rate laser communication systems which surpass the present performance of the Nd:YAG laser has been successfully demonstrated.

  6. Laser Photon Force Measurements using a CW Laser

    NASA Technical Reports Server (NTRS)

    Gray, Perry; Edwards, David L.; Carruth, M. Ralph, Jr.; Munafo, Paul M. (Technical Monitor)

    2002-01-01

    The photon force resulting from the non-damaging impact of laser derived photons on a metallic target was measured using a vacuum compatible microbalance. This experiment quantitatively verified that the force resulting from laser photons impacting a reflective surface is measurable and predictable. The photon wavelength is 1064 mn and the laser is a multi-mode 30OW Nd YAG continuous wave (CW) laser.

  7. Power-Stabilization of High Frequency Gyrotrons Using a Double PID Feedback Control for Applications to High Power THz Spectroscopy

    NASA Astrophysics Data System (ADS)

    Idehara, Toshitaka; Kuleshov, Alexei; Ueda, Keisuke; Khutoryan, Eduard

    2013-11-01

    High stabilization of the output power of high frequency gyrotrons for high power THz spectroscopy 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 magnetron injection gun (MIG) for stabilization of an electron beam current and an additional PID control of an anode voltage of the gun for direct stabilization of output power. This double PID control achieved effective responses for the stabilization of output power in both slow (from several tens seconds to several minutes) and fast (from milliseconds to seconds) time scales.

  8. A method for suppression of spurious fundamental-harmonic waves in gyrotrons operating at the second cyclotron harmonic

    NASA Astrophysics Data System (ADS)

    Kalynov, Yu. K.; Osharin, I. V.; Savilov, A. V.

    2016-05-01

    A typical problem of gyrotrons operating at high harmonics of the electron cyclotron frequency is the suppression of parasitic near-cutoff waves excited at lower harmonics. In this paper, a method for a significant improvement of the selectivity of the second-harmonic gyrotrons is proposed. This method is based on the use of quasi-regular cavities with short irregularities, which provide different effects on the process of excitation of the operating second-harmonic wave and the spurious fundamental-harmonic wave by the electron beam.

  9. Status of the Project-X CW Linac Design

    SciTech Connect

    Ostiguy, J-F.; Solyak, N.; Berrutti, P.; Carneiro, J.P.; Lebedev, V.; Nagaitsev, S.; Saini, A.; Stheynas, B.; Yakovlev, V.P.; /Fermilab

    2012-05-01

    Project-X is a proposed proton accelerator complex at Fermilab that would provide particle beams to support a diversified experimental program at the intensity frontier. As currently envisioned, the complex would employ a CW superconducting linac to accelerate a 1 mA average, 5 mA peak H{sup -} beam from 2.1 MeV to 3 GeV. A second superconducting linac, operating in pulsed mode would ultimately accelerate a small fraction of this beam up to 8 GeV. The CW linac is based on five families of resonators operating at three frequencies: half-wave (1 family at 162.5 MHz), spoke (2 families at 325 MHz) and elliptical (2 families at 650 MHz). Accelerating and focusing elements are assembled in cryomodules separated by short warm sections. A long open region ({approx} 15 m) allows beam extraction at 1 GeV in support of a nuclear experimental program. In this paper, we present the latest iteration of the CW linac baseline lattice. We also briefly compare it to an alternative where the 162.5 half-wave resonators are replaced with 325 MHz spoke resonators.

  10. Operation of a 3 MW, 140 GHz gyrotron with a coaxial cavity

    SciTech Connect

    Advani, R.N.; Pedrozzi, M.; Kreischer, K.E.; Temkin, R.J.; Read, M.E.

    1998-12-31

    Experimental results will be presented here for a high power, high frequency coaxial gyrotron. The designed goal for this experiment is to produce 3 MW, at 140 GHz in the TE 21,13 mode with an efficiency of at least 30%. In the experiment the inner conductor extends from the electron gun to the output. The main advantages of the coaxial conductor are: causes rarefied mode spectrum around the design mode; reduces the quality factor of competing modes; volume modes (higher radial index) can be chosen (which increases the output power); and reduces voltage depression.

  11. Particle simulation of a ka-band gyrotron traveling wave amplifier

    SciTech Connect

    Xu Shouxi; Liu Pukun; Zhang Shichang; Du Chaohai; Xue Qianzhong; Geng Zhihui; Su Yinong

    2011-08-15

    The design of a ka-band gyrotron traveling wave (gyro-TWT) amplifier is presented. The gyro-TWT amplifier with a severed structure operates in the fundamental harmonic TE{sub 01} circular electric mode. The beam-wave interaction is studied by using a particle-in-cell (PIC) code. The simulations predict that the amplifier can produce an output peak power of over 155 kW, 22% efficiency, 23 dB gain, and a 3 dB bandwidth of 2 GHz for a 70 kV, 10 A electron beam with an axial velocity spread {Delta}v{sub z}/v{sub z}=5%.

  12. Gyrotron scattering from non-thermal fluctuations in the Tara Tandem Mirror

    SciTech Connect

    Machuzak, J.S.; Myer, R.C.; Woskoboinikow, P.P.; Cohn, D.R.; Gerver, M.; Golovato, S.N.; Horne, S.; Kubota, S.; Mulligan, W.J.; Post, R.S.

    1987-09-01

    A 137 GHz, approx.0.4 kW, 75 ms pulsed gyrotron has been used for collective Thomson scattering in the Tara Tandem Mirror plug cell at MIT. Scattering from ion cyclotron waves during ion cyclotron resonance frequency (ICRF) heating, ion Bernstein wave harmonics, and plasma fluctuations possibly due to microinstabilities have been observed. The observed harmonic nature of the ion Bernstein waves may be due to an enhanced ion thermal frequency spectrum in an ICRF heated plasma. 6 refs., 1 fig.

  13. Studying the start-up scenario for a pulsed gyrotron with a relativistic electron beam

    NASA Astrophysics Data System (ADS)

    Zaitsev, N. I.; Zapevalov, S. A.; Malygin, A. V.; Moiseev, M. A.; Shevchenko, A. S.

    2010-08-01

    We present the results of studying the start-up scenario for a high-power pulsed gyrotron operated at the TE53 mode for two variants of the current-voltage characteristic of a three-electrode magnetron-injection electron gun. In the standard variant of feeding the voltage to the first anode from the resistive divider, sequential generation of the TE73 and TE63 modes, and, finally, the operating TE53 mode was observed at the edge of the pulse. The current-voltage characteristic for which only the operating mode is excited is obtained by decreasing the growth rate of the voltage applied to the first anode.

  14. Synthesized Parameters of MIG for 200 kW, 42 GHz Gyrotron

    NASA Astrophysics Data System (ADS)

    Singh, Udaybir; Bera, Anirban; Rao, R. R.; Sinha, Ashok K.

    2010-04-01

    In this paper, a synthesized design of the magnetron injection gun (MIG) for a 200 kW, 42 GHz gyrotron is presented. The synthesis steps involve the selection of the type of the MIG, the development of the design criteria, the selection of initial design parameters and the development of a program for the estimation of the synthesized parameters for the MIG design. The presented approach estimates the cathode, the beam and the anode parameters, enabling one to build a synthesis model of a complete MIG system.

  15. Design principles for a sheet-beam electron gun for a quasi-optical gyrotron

    NASA Astrophysics Data System (ADS)

    Manheimer, Wallace M.; Fliflet, Arne W.; Lee, Robert

    1990-03-01

    The design considerations for a magnetized sheet beam for which the electrons have energy both perpendicular and parallel to the magnetic field are examined, including the basic design principles and scaling laws, the issue of orbit crossing and electrode synthesis in a sheet beam configuration, limiting currents both in the guide tube and across the resonator, and the edge effects and their reduction or elimination by the use of edge focusing electrodes. The application envisioned for the sheet beam is the driving of a quasi-optical gyrotron for electron cyclotron resonance heating and current drive in fusion plasmas.

  16. Linear and nonlinear theories of a large-orbit gyrotron traveling wave amplifier

    SciTech Connect

    Jiao Chongqing; Luo Jirun

    2010-05-15

    The linear and nonlinear theories of large-orbit gyrotron traveling wave amplifiers (gyro-TWAs) have been developed based on the corresponding theories of small-orbit gyro-TWAs. The linear theory is in good agreement with the nonlinear theory in the small signal region of large-orbit gyro-TWAs. The phenomenon that most electrons move toward the axis of interaction circuit during the beam-wave interaction is observed and its potential effect on the design of large-orbit coaxial gyro-TWAs is emphasized.

  17. Design of 28 GHz, 200 kW Gyrotron for ECRH Applications

    NASA Astrophysics Data System (ADS)

    Yadav, Vivek; Singh, Udaybir; Kumar, Nitin; Kumar, Anil; Deorani, S. C.; Sinha, A. K.

    2013-01-01

    This paper presents the design of 28 GHz, 200 kW gyrotron for Indian TOKAMAK system. The paper reports the designs of interaction cavity, magnetron injection gun and RF window. EGUN code is used for the optimization of electron gun parameters. TE03 mode is selected as the operating mode by using the in-house developed code GCOMS. The simulation and optimization of the cavity parameters are carried out by using the Particle-in-cell, three dimensional (3-D)-electromagnetic simulation code MAGIC. The output power more than 250 kW is achieved.

  18. Coupler for coupling gyrotron whispering gallery mode RF into HE11 waveguide

    DOEpatents

    Neilson, Jeffrey M

    2015-02-24

    A cylindrical waveguide with a mode converter transforms a whispering gallery mode from a gyrotron cylindrical waveguide with a helical cut launch edge to a quasi-Gaussian beam suitable for conveyance through a corrugated waveguide. This quasi-Gaussian beam is radiated away from the waveguide using a spiral cut launch edge, which is in close proximity to a first mode converting reflector. The first mode converting reflector is coupled to a second mode converting reflector which provides an output free-space HE11 mode wave suitable for direct coupling into a corrugated waveguide. The radiated beam produced at the output of the second mode converting reflector is substantially circular.

  19. Gyrotron Output Power Stabilization by PID Feedback Control of Heater Current and Anode Voltage

    NASA Astrophysics Data System (ADS)

    Khutoryan, E. M.; Idehara, T.; Kuleshov, A. N.; Ueda, K.

    2014-12-01

    To provide stable output power of a gyrotron during long operation time the power stabilization was achieved by two schemes with PID feedback control of heater current and anode voltage. It was based on the dependence of the output power on both the anode voltage and the beam current and also on the dependence of the beam current on the gun heater current. Both schemes provided decrease of the power standard deviation to 0.3-0.5%. The comparison between parameters of both schemes is discussed in the paper.

  20. Study of a high-order-mode gyrotron traveling-wave amplifier

    SciTech Connect

    Chiu, C. C.; Tsai, C. Y.; Kao, S. H.; Chu, K. R.; Barnett, L. R.; Luhmann, N. C. Jr.

    2010-11-15

    Physics and performance issues of a TE{sub 01}-mode gyrotron traveling-wave amplifier are studied in theory. For a high order mode, absolute instabilities on neighboring modes at the fundamental and higher cyclotron harmonic frequencies impose severe constraints to the device capability. Methods for their stabilization are outlined, on the basis of which the performance characteristics are examined in a multidimensional parameter space under the marginal stability criterion. The results demonstrate the viability of a high-order-mode traveling-wave amplifier and provide a roadmap for design tradeoffs among power, bandwidth, and efficiency. General trends are observed and illustrated with specific examples.

  1. Demonstration of Steady State Operation with 1 MW of 170 GHz gyrotron for ITER

    SciTech Connect

    Kasugai, Atsushi; Takahashi, Koji; Kajiwara, Ken; Kobayashi, Noriyuki; Sakamoto, Keishi

    2007-09-28

    A quasi-steady-state operation of 1 MW/800 s with the efficiency of 55%, which exceeded 1 MW/500 s/50% of the performance required in ITER, was demonstrated in a 170 GHz gyrotron. The oscillation characteristics in the long pulse operation was clarified, and the operation scenario to the hard self-excitation region for the high efficiency oscillation was newly established by controlling a pitch factor of the electron and the cavity magnetic field during the pulse with fixed beam voltage in the triode MIG. The result gives a clear outlook for the success of ECH and ECCD in ITER.

  2. Linear analysis of an axially grooved rectangular gyrotron for harmonic operation

    NASA Technical Reports Server (NTRS)

    Ferendeci, A. M.; Han, C. C.

    1985-01-01

    In an axially grooved rectangular waveguide the linearized Vlasov equation is solved to find the perturbed distribution function resulting from the electromagnetic forces on the electrons. The resulting beam current and the propagating electromagnetic waves of the cold tube are used in the inhomogeneous Maxwell's equation to derive the general dispersion equation. This equation is then transformed into the electron beam frame and the resulting linear growth rate of amplification is calculated. By maximizing the linear growth rate, the operational parameters of the gyrotron are then optimized.

  3. Linear and time-dependent behavior of the gyrotron backward-wave oscillator.

    PubMed

    Chen, S H; Chang, T H; Pao, K F; Fan, C T; Chu, K R

    2002-12-23

    Formation of axial modes in the gyrotron backward-wave oscillator is examined in the perspective of optimum conditions for beam-wave interactions. Distinctive linear properties are revealed and interpreted physically. Nonlinear implications of these properties (specifically, the role of high-order axial modes) are investigated with time-dependent simulations. Nonstationary oscillations exhibit self-modulation behavior while displaying no evidence of axial mode competition. Reasons for the erratic frequency tuning are investigated and stable tuning regimes are identified as a remedy. PMID:12484861

  4. Feasibility study of a cryogenically cooled window for high-power gyrotrons

    SciTech Connect

    Haste, G.R.; Kimrey, H.D.; Prosise, J.D.

    1986-07-01

    Single-crystal sapphire is currently in use as the material for output windows in high-power microwave tubes, particularly gyrotrons. These windows are currently being cooled by fluorocarbon fluids at near-room temperatures. There are, however, several advantages in operating the window at very low temperatures: less absorption and consequent heating of the window, greater material strength, improved resistance to crack formation, greater thermal conductivity, and reduced thermal expansion. Operation at cryogenic temperatures is shown to be feasible. The output power, which is currently limited by window constraints, could be increased by an order of magnitude or more.

  5. Peculiarities of Optimizing the Subsystems of a Continuous-Wave Gyrotron with a Generation Frequency of 0.26 THz at the Fundamental Cyclotron Resonance

    NASA Astrophysics Data System (ADS)

    Glyavin, M. Yu.; Denisov, G. G.; Zapevalov, V. E.; Kuftin, A. N.; Manuilov, V. N.; Soluyanova, E. A.; Sedov, A. S.; Kholoptsev, V. V.; Chirkov, A. V.

    2016-02-01

    We present the results of developing the main units of a gyrotron operated in the continuous-wave regime with a generation frequency of 0 .26 THz. To improve selection of the operating mode in a oversized electrodynamic system, the gyrotron works at the fundamental cyclotron harmonic, which anticipates the use of a cryomagnet with a maximum magnetic field of 10 T, which does not require filling with liquid helium. The results of optimizing the electron-optical system, the cavity, and the quasi-optical converter of the output radiation are presented, and the control system, which is developed for the gyrotron setup, is described.

  6. Near Real-Time Gyrotron Data Streaming and Data Acquisition with ns Resolution on the DIII-D ECH System

    NASA Astrophysics Data System (ADS)

    Torrezan, A. C.; Ponce, D.; Gorelov, Y. A.; Cengher, M.; Lohr, J.

    2014-10-01

    As part of the expansion and upgrade of the electron cyclotron heating (ECH) systen on DIII-D, a new data acquisition setup has been implemented to acquire and display waveform data from all gyrotrons in near real time with high time resolution. The data acquisition for each gyrotron system is based on a fast digitizer with 8 channels running at 2 MS/s/channel and a resolution of 14 bits. This enables the operator to monitor all gyrotron-relevant variables as well as fast diagnostic signals such as window arcs. The data are transferred to a local computer through a 132 MB/s PCI bus, and then are streamed to the ECH operator and to a local network attached storage using 1 GB Ethernet links. The data are displayed to the ECH operator by means of a graphical user interface developed in LabVIEW, replacing physical scopes. Acquired gyrotron data are accessible at DIII-D through a local database (PTDATA) connected to the ECH data acquisition system by an Ethernet line, a configuration that eliminates the need for legacy CAMAC hardware in the data link. Work supported by the US Department of Energy under DE-FC02-04ER54698.

  7. Numerical studies of startup scenarios in a 1.5 MW, 110 GHz gyrotron operating in short pulses

    NASA Astrophysics Data System (ADS)

    Sinitsyn, Oleksandr; Nusinovich, Gregory; Antonsen, Thomas, Jr.; Tax, David; Temkin, Richard; Ireap, University Of Maryland Collaboration; Psfc, Massachusetts Institute Of Technology Collaboration

    2011-10-01

    Megawatt class gyrotrons operate in very high-order modes which form a very dense spectrum. In order to excite the operating mode in the presence of many competitors and drive it to the nominal operating point, careful control of the gyrotron's startup is necessary. Our studies are focused on the startup scenarios of the 110 GHz MIT gyrotron designed for operation at 1.5 MW power level in short pulses. Nominal parameters of the electron beam are: 96 kV, 42 A and orbital-to-axial velocity ratio α = 1.4. Previous numerical studies of the startup of this gyrotron had shown that at low voltages (at about 62 kV), first, the high-frequency TE23,6 mode was excited and then, at higher voltages (at about 74 kV), it was replaced by the desired TE22,6 mode. However, during a series of recent experiments at MIT it was shown that instead of the TE23,6 mode a low-frequency TE21,6 mode was excited during the voltage rise and persisted up to a voltage of 70 kV. In this work the authors make an attempt to simulate and explain this result with the help of self-consistent time-dependent code MAGY.

  8. High-power gyrotron traveling-wave amplifier with distributed wall losses and attenuating severs

    SciTech Connect

    Yeh, Y.S.; Shin, Y.Y.; You, Y.C.; Chen, L.K.

    2005-04-15

    Distributed-loss gyrotron traveling-wave amplifiers (gyro-TWTs) with high-gain, broadband, and millimeter-wave capabilities have been demonstrated. Most structures with distributed wall losses are stabilized in gyro-TWTs that operate at low beam currents. Attenuating severs are added to the interaction circuit of a distributed-loss gyro-TWT to prevent high beam currents that result in mode competition. Simulation results show that gyrotron backward-wave oscillations (gyro-BWOs) are not effectively suppressed by the lossy section; in contrast, the severed sections can effectively enhance the start-oscillation threshold of gyro-BWOs in the proposed gyro-TWT. Meanwhile, localized reflective oscillations seem not to occur in the gyro-TWT unless it operates at a high magnetic field or with a high interaction length. The stable gyro-TWT, operating in the low-loss TE{sub 01} mode, is predicted to yield a peak output power of 405 kW at 33 GHz with an efficiency of 20%, a saturated gain of 77 dB and a 3 dB bandwidth of 2.5 GHz for a 100 kV, 20 A electron beam with an axial velocity spread of {delta}v{sub z}/v{sub z}=5%.

  9. Stability analysis of a coaxial-waveguide gyrotron traveling-wave amplifier

    SciTech Connect

    Hung, C.L.; Yeh, Y.S.

    2005-10-01

    The gyrotron traveling-wave tube (gyro-TWT) amplifier is known to be highly susceptible to spurious oscillations. This study develops a simulation approach to analyze the stability of a coaxial-waveguide gyro-TWT with distributed wall losses. The interplay among the absolute instabilities, the gyrotron backward-wave oscillations, and the circuit parameters is analyzed. Simulation results reveal that the distributed wall losses effectively stabilize spurious oscillations in the coaxial gyro-TWT. Furthermore, the wall resistivity of the center conductor is shown to be an additional effective mechanism for suppressing oscillations. Under stable operation conditions, the coaxial gyro-TWT with distributed losses is predicted to generate 435 kW in the Ka band with 31% efficiency, a saturated gain of 45 dB, and a bandwidth of 1.86 GHz ({approx_equal}5.8%) for a 70 kV, 20 A electron beam with an {alpha}(={nu}{sub perpendicular})/{nu}{sub z})=1.0 and an axial velocity spread of {delta}{nu}{sub z}/{nu}{sub z}=5%.

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

    NASA Astrophysics Data System (ADS)

    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.

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

    SciTech Connect

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

    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.

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

    SciTech Connect

    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.; Chen, H. Y.; Fan, C. T.

    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.

  13. Scattering volume in the collective Thomson scattering measurement using high power gyrotron in the LHD

    NASA Astrophysics Data System (ADS)

    Kubo, S.; Nishiura, M.; Tanaka, K.; Moseev, D.; Ogasawara, S.; Shimozuma, T.; Yoshimura, Y.; Igami, H.; Takahashi, H.; Tsujimura, T. I.; Makino, R.

    2016-06-01

    High-power gyrotrons prepared for the electron cyclotron heating at 77 GHz has been used for a collective Thomson scattering (CTS) study in LHD. Due to the difficulty in removing fundamental and/or second harmonic resonance in the viewing line of sight, the subtraction of the background ECE from measured signal was performed by modulating the probe beam power from a gyrotron. The separation of the scattering component from the background has been performed successfully taking into account the response time difference between both high-energy and bulk components. The other separation was attempted by fast scanning the viewing beam across the probing beam. It is found that the intensity of the scattered spectrum corresponding to the bulk and high energy components were almost proportional to the calculated scattering volume in the relatively low density region, while appreciable background scattered component remains even in the off volume in some high density cases. The ray-trace code TRAVIS is used to estimate the change in the scattering volume due to probing and receiving beam deflection effect.

  14. Beam-wave interaction behavior of a 35 GHz metal PBG cavity gyrotron

    SciTech Connect

    Singh, Ashutosh; Jain, P. K.

    2014-09-15

    The RF behavior of a 35 GHz photonic band gap (PBG) cavity gyrotron operating in TE{sub 041}-like mode has been presented to demonstrate its single mode operation capability. In this PBG cavity gyrotron, the conventional tapered cylindrical cavity is replaced by a metal PBG cavity as its RF interaction structure. The beam-wave interaction behavior has been explored using time dependent multimode nonlinear analysis as well as through 3D PIC simulation. Metal PBG cavity is treated here similar to that of a conventional cylindrical cavity for the desired mode confinement. The applied DC magnetic field profile has been considered uniform along the PBG cavity length both in analysis as well as in simulation. Electrons energy and phase along the interaction length of the PBG cavity facilitates bunching mechanism as well as energy transfer phenomena from the electron beam to the RF field. The RF output power for the TE{sub 041}-like design mode as well as nearby competing modes have been estimated and found above to 100 kW in TE{sub 041}-like mode with ∼15% efficiency. Results obtained from the analysis and the PIC simulation are found in agreement within 8% variation, and also it supports the single mode operation, as the PBG cavity does not switch into other parasitic modes in considerably large range of varying DC magnetic field, contrary to the conventional cylindrical cavity interaction structure.

  15. Effect of background plasma on electromagnetic properties of coaxial gyrotron cavity

    NASA Astrophysics Data System (ADS)

    Moskvitina, Yu. K.; Zaginaylov, G. I.; Tkachenko, V. I.

    2014-07-01

    We analyze the effect of the background plasma on the electromagnetic properties of coaxial resonators with a smooth and a corrugated inner conductors used in high-power gyrotrons. It is shown that the plasma produces different effects on the modes with different signs of the azimuthal index, leading to a decrease or an increase in the resonance frequencies. A modification of the distributions of electromagnetic fields and the electromagnetic energy density by the background plasma occurs in such a way that Ohmic losses decrease both on the inner and on the outer conductors. In the case of a smooth inner conductor, this is due to a decrease in the field strengths on the surface of the conductors. If the inner conductor is corrugated, the background plasma leads to an increase in the field strengths on its surface. Nevertheless, the relative Ohmic loss power decreases due to an increase in the energy density in the resonator (which is also caused by the background plasma). Calculations were mainly performed for a coaxial resonator of a gyrotron operating on the TE34.19 mode (Karlsruhe, Germany).

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

    NASA Astrophysics Data System (ADS)

    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.

  17. Plasma structures observed in gas breakdown using a 1.5 MW, 110 GHz pulsed gyrotron

    SciTech Connect

    Hidaka, Yoshiteru; Choi, E. M.; Mastovsky, I.; Shapiro, M. A.; Sirigiri, J. R.; Temkin, R. J.; Edmiston, G. F.; Neuber, A. A.; Oda, Y.

    2009-05-15

    Regular two-dimensional plasma filamentary arrays have been observed in gas breakdown experiments using a pulsed 1.5 MW, 110 GHz gyrotron. The gyrotron Gaussian output beam is focused to an intensity of up to 4 MW/cm{sup 2}. The plasma filaments develop in an array with a spacing of about one quarter wavelength, elongated in the electric field direction. The array was imaged using photodiodes, a slow camera, which captures the entire breakdown event, and a fast camera with a 6 ns window. These diagnostics demonstrate the sequential development of the array propagating back toward the source. Gases studied included air, nitrogen, SF{sub 6}, and helium at various pressures. A discrete plasma array structure is observed at high pressure, while a diffuse plasma is observed at lower pressure. The propagation speed of the ionization front for air and nitrogen at atmospheric pressure for 3 MW/cm{sup 2} was found to be of the order of 10 km/s.

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

    SciTech Connect

    Darbos, C.; Bouquey, F.; Lambert, R.; Magne, R.; Traisnel, E.; Prinz, H. O.; Thumm, M.; Hogge, J. P.; Lievin, C.

    2007-09-28

    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.

  19. Solid-state nitrogen-14 nuclear magnetic resonance enhanced by dynamic nuclear polarization using a gyrotron.

    PubMed

    Vitzthum, Veronika; Caporini, Marc A; Bodenhausen, Geoffrey

    2010-07-01

    By combining indirect detection of 14N with dynamic nuclear polarization (DNP) using a gyrotron, the signal-to-noise ratio can be dramatically improved and the recovery delay between subsequent experiments can be shortened. Spectra of glassy samples of the amino acid proline doped with the stable bi-radical TOTAPOL rotating at 15.625 kHz at 110K were obtained in a 400 MHz solid-state NMR spectrometer equipped with a gyrotron for microwave irradiation at 263 GHz. DNP enhancement factors on the order of epsilon approximately 40 were achieved. The recovery delays can be reduced from 60 s without radicals at 300 K to 6 s with radicals at 110 K. In the absence of radicals at room temperature, the proton relaxation in proline is inefficient due to the absence of rotating methyl groups and other heat sinks, thus making long recovery delays mandatory. DNP allows one to reduce the acquisition times of 13C-detected 14N spectra from several days to a few hours. PMID:20488737

  20. High current multicharged metal ion source using high power gyrotron heating of vacuum arc plasma.

    PubMed

    Vodopyanov, A V; Golubev, S V; Khizhnyak, V I; Mansfeld, D A; Nikolaev, A G; Oks, E M; Savkin, K P; Vizir, A V; Yushkov, G Yu

    2008-02-01

    A high current, multi charged, metal ion source using electron heating of vacuum arc plasma by high power gyrotron radiation has been developed. The plasma is confined in a simple mirror trap with peak magnetic field in the plug up to 2.5 T, mirror ratio of 3-5, and length variable from 15 to 20 cm. Plasma formed by a cathodic vacuum arc is injected into the trap either (i) axially using a compact vacuum arc plasma gun located on axis outside the mirror trap region or (ii) radially using four plasma guns surrounding the trap at midplane. Microwave heating of the mirror-confined, vacuum arc plasma is accomplished by gyrotron microwave radiation of frequency 75 GHz, power up to 200 kW, and pulse duration up to 150 micros, leading to additional stripping of metal ions by electron impact. Pulsed beams of platinum ions with charge state up to 10+, a mean charge state over 6+, and total (all charge states) beam current of a few hundred milliamperes have been formed. PMID:18315170

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

    NASA Astrophysics Data System (ADS)

    Li, G. D.; Chang, P. C.; Chen, H. Y.; Chiang, W. Y.; Fan, C. T.; Lin, P. N.; Kao, S. H.; Lin, Y. N.; Huang, Y. J.; Barnett, L. R.; Chu, K. R.

    2015-11-01

    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.

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

    PubMed Central

    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) mode. Experimental results are compared with nonlinear simulations and show reasonable agreement. The millimeter-wave output beam was imaged in a single shot using a pyroelectric camera. The mode patterns matched reasonably well to theory for both the TE(0,1) mode and the TE(1,1) mode. Repeatable mode patterns were obtained at intervals ranging from 0.8 s apart to 11 min apart at the output of the final mode converter. PMID:17431442

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

    PubMed

    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

    2006-06-01

    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) mode. Experimental results are compared with nonlinear simulations and show reasonable agreement. The millimeter-wave output beam was imaged in a single shot using a pyroelectric camera. The mode patterns matched reasonably well to theory for both the TE(0,1) mode and the TE(1,1) mode. Repeatable mode patterns were obtained at intervals ranging from 0.8 s apart to 11 min apart at the output of the final mode converter. PMID:17431442

  4. High current multicharged metal ion source using high power gyrotron heating of vacuum arc plasma

    SciTech Connect

    Vodopyanov, A. V.; Golubev, S. V.; Khizhnyak, V. I.; Mansfeld, D. A.; Nikolaev, A. G.; Oks, E. M.; Savkin, K. P.; Vizir, A. V.; Yushkov, G. Yu.

    2008-02-15

    A high current, multi charged, metal ion source using electron heating of vacuum arc plasma by high power gyrotron radiation has been developed. The plasma is confined in a simple mirror trap with peak magnetic field in the plug up to 2.5 T, mirror ratio of 3-5, and length variable from 15 to 20 cm. Plasma formed by a cathodic vacuum arc is injected into the trap either (i) axially using a compact vacuum arc plasma gun located on axis outside the mirror trap region or (ii) radially using four plasma guns surrounding the trap at midplane. Microwave heating of the mirror-confined, vacuum arc plasma is accomplished by gyrotron microwave radiation of frequency 75 GHz, power up to 200 kW, and pulse duration up to 150 {mu}s, leading to additional stripping of metal ions by electron impact. Pulsed beams of platinum ions with charge state up to 10+, a mean charge state over 6+, and total (all charge states) beam current of a few hundred milliamperes have been formed.

  5. JLab CW Cryomodules for 4th Generation Light Sources

    SciTech Connect

    Rimmer, Robert; Bundy, Richard; Cheng, Guangfeng; Ciovati, Gianluigi; Clemens, William; Daly, Edward; Henry, James; Hicks, William; Kneisel, Peter; Manning, Stephen; Manus, Robert; Marhauser, Frank; Preble, Joseph; Reece, Charles; Smith, Karl; Stirbet, Mircea; Turlington, Larry; Wang, Haipeng; Wilson, Katherine

    2008-01-23

    Fourth generation light sources hold the prospect of unprecedented brightness and optical beam quality for a wide range of scientific applications. Many of the proposed new facilities will rely on large superconducting radio frequency (SRF) based linacs to provide high energy, low emittance CW electron beams. For high average power applications there is a growing acceptance of energy recovery linac (ERL) technology as the way to support large recirculating currents with modest RF power requirements. CW SRF and high current ERLs are two core competencies at Jefferson Lab. JLab has designed and built a number of CW cryomodules of several different types starting with the original CEBAF design, with variations for higher current in the two generations of JLab’s free-electron laser (FEL), through two intermediate prototypes to the final high-performance module for the 12 GeV upgrade. Each of these represent fully engineered and tested configurations with a variety of specifications that could be considered for possible use in fourth generation light sources. Furthermore JLab has been actively pursuing advanced concepts for highcurrent high-efficiency cryomodules for next generation ERL based FEL’s. These existing and proposed designs span the range from about 1mA single-pass to over 100 mA energy recovered current capability. Specialized configurations also exist for high-current non-energy recovered sections such as the injector region where very high RF power is required. We discuss the performance parameters of these existing and proposed designs and their suitability to different classes of fourth generation light sources.

  6. Quasi-CW Laser Diode Bar Life Tests

    NASA Technical Reports Server (NTRS)

    Stephen, Mark A.; Krainak, Michael A.; Dallas, Joseph L.

    1997-01-01

    NASA's Goddard Space Flight Center is developing technology for satellite-based, high peak power, LIDAR transmitters requiring 3-5 years of reliable operation. Semi-conductor laser diodes provide high efficiency pumping of solid state lasers with the promise of long-lived, reliable operation. 100-watt quasi- CW laser diode bars have been baselined for the next generation laser altimeters. Multi-billion shot lifetimes are required. The authors have monitored the performance of several diodes for billions of shots and investigated operational modes for improving diode lifetime.

  7. Design of 250-MW CW RF system for APT

    SciTech Connect

    Rees, D.

    1997-09-01

    The design for the RF systems for the APT (Accelerator Production of Tritium) proton linac will be presented. The linac produces a continuous beam power of 130 MW at 1300 MeV with the installed capability to produce up to a 170 MW beam at 1700 MeV. The linac is comprised of a 350 MHz RFQ to 7 MeV followed in sequence by a 700 MHz coupled-cavity drift tube linac, coupled-cavity linac, and superconducting (SC) linac to 1700 MeV. At the 1700 MeV, 100 mA level the linac requires 213 MW of continuous-wave (CW) RF power. This power will be supplied by klystrons with a nominal output power of 1.0 MW. 237 kystrons are required with all but three of these klystrons operating at 700 MHz. The klystron count includes redundancy provisions that will be described which allow the RF systems to meet an operational availability in excess of 95 percent. The approach to achieve this redundancy will be presented for both the normal conducting (NC) and SC accelerators. Because of the large amount of CW RF power required for the APT linac, efficiency is very important to minimize operating cost. Operation and the RF system design, including in-progress advanced technology developments which improve efficiency, will be discussed. RF system performance will also be predicted. Because of the simultaneous pressures to increase RF system reliability, reduce tunnel envelope, and minimize RF system cost, the design of the RF vacuum windows has become an important issue. The power from a klystron will be divided into four equal parts to minimize the stress on the RF vacuum windows. Even with this reduction, the RF power level at the window is at the upper boundary of the power levels employed at other CW accelerator facilities. The design of a 350 MHz, coaxial vacuum window will be presented as well as test results and high power conditioning profiles. The transmission of 950 kW, CW, power through this window has been demonstrated with only minimal high power conditioning.

  8. High efficiency CW green-pumped alexandrite lasers

    NASA Astrophysics Data System (ADS)

    Kuper, J. W.; Brown, D. C.

    2006-02-01

    High power, CW and pulsed alexandrite lasers were produced by pumping the laser rod with a high quality diode pumped 532 nm laser sources. This pumping architecture provides stable performance with output power > 1.4 W at 767nm in the free running mode and 0.78W at 1000 Hz. An output of 80 mW at 375.5 nm was achieved at 500 Hz. This approach holds promise for the production of a scalable diode-pumped, tunable alexandrite laser systems operating in the near infrared (750 nm), and the ultraviolet (375 and 250 nm) spectral regions.

  9. Cavitation induced by CW lasers in absorbing liquids

    NASA Astrophysics Data System (ADS)

    Ramirez-San-Juan, J. C.; Rodriguez-Aboytes, E.; Martínez-Canton, A. E.; Baldovino-Pantaleon, O.; Torres-Hurtado, S.; Robledo-Martinez, A.; Korneev, N.; Ramos-Garcia, R.

    2010-02-01

    Novel results are presented on thermocavitation in highly absorbing solutions using CW low power laser (λ=975 nm). Due to the large absorption coefficient (135 cm-1) at the laser wavelength, penetration length is only ~74μm inside the liquid and asymmetric bubbles are generated near the beam's entrance wall. We report the temporal dynamic of the cavitation bubble, which is much shorter than previously reported. We found that the amplitude of the shock wave decreases exponentially with the beam power. As shown in this work, thermocavitation is a phenomenon that has a great application potential in areas such as ultrasonic waves generation and controlled tissue ablation for use in lithotripsy.

  10. Ultraviolet photometry of the eclipsing variable CW Cephei

    NASA Technical Reports Server (NTRS)

    Sobieski, S.

    1972-01-01

    An extended series of photometric observations were made of the eclipsing variable CW Cephei using the Wisconsin instrument on OAO-2. Approximate elements which were derived based solely on the eclipse depths and shape of the secondary are in satisfactory agreement with those found using ground based observations. However, persistent asymmetries and anomalous light variations, all larger than the expected experimental error, were also found; subsequent ground-based observations show H sub alpha entirely in emission indicating the presence of an extended gaseous system surrounding one or both of the components. Consistent solutions utilizing all data at all wavelengths were not found.

  11. GEM: ANL 4-GeV CW electron microtron design

    SciTech Connect

    Kustom, R.L.

    1983-01-01

    A six-sided hexagonal microtron has been chosen as the accelerator to generate the beams required to pursue a national research program at a CW 4 GeV electron laboratory. This option has the advantage of superior beam quality, low capital and operating cost, and promise of furnishing beams of several electron energies simultaneously. Only moderate rf power is required because of the basic feature of all microtron designs, recirculation of the electron beam through the same rf accelerating section many times. The hexatron design has the additional feature of compatibility with an existing accelerator complex at Argonne which is currently unoccupied and available.

  12. Photometric analysis of the overcontact binary CW Cas

    SciTech Connect

    Wang, J. J.; Qian, S. B.; He, J. J.; Li, L. J.; Zhao, E. G.

    2014-11-01

    New CCD photometric observations of overcontact binary CW Cas were carried out in 2004 and 2011. In particular, the light curve obtained in 2004 shows a remarkable O'Connell effect. Compared with light curves in different observing seasons, variations were found. These variations can be explained by dark spot activities on the surface of at least one component. Using the Wilson-Devinney code with a spot model, we find that the photometric solutions confirm CW Cas is a shallow W-subtype overcontact binary with a spotted massive component. Our new determined times of minimum light together with the others published in the literature were analyzed to find a change of orbital period. From the O – C curves, the period of the system shows a cyclic period change (P {sub 3} = 69.9 yr, A {sub 3} = 0.03196 days) superposed on the linear increase. The cyclic variation, if explained as the light-travel time effect, reveals the presence of a tertiary companion.

  13. An Acoustic Demonstration Model for CW and Pulsed Spectrosocopy Experiments

    NASA Astrophysics Data System (ADS)

    Starck, Torben; Mäder, Heinrich; Trueman, Trevor; Jäger, Wolfgang

    2009-06-01

    High school and undergraduate students have often difficulties if new concepts are introduced in their physics or chemistry lectures. Lecture demonstrations and references to more familiar analogues can be of great help to the students in such situations. We have developed an experimental setup to demonstrate the principles of cw absorption and pulsed excitation - emission spectroscopies, using acoustical analogues. Our radiation source is a speaker and the detector is a microphone, both controlled by a computer sound card. The acoustical setup is housed in a plexiglas box, which serves as a resonator. It turns out that beer glasses are suitable samples; this also helps to keep the students interested! The instrument is controlled by a LabView program. In a cw experiment, the sound frequency is swept through a certain frequency range and the microphone response is recorded simultaneously as function of frequency. A background signal without sample is recorded, and background subtraction yields the beer glass spectrum. In a pulsed experiment, a short sound pulse is generated and the microphone is used to record the resulting emission signal of the beer glass. A Fourier transformation of the time domain signal gives then the spectrum. We will discuss the experimental setup and show videos of the experiments.

  14. Photometric Analysis of the Overcontact Binary CW Cas

    NASA Astrophysics Data System (ADS)

    Wang, J. J.; Qian, S. B.; He, J. J.; Li, L. J.; Zhao, E. G.

    2014-11-01

    New CCD photometric observations of overcontact binary CW Cas were carried out in 2004 and 2011. In particular, the light curve obtained in 2004 shows a remarkable O'Connell effect. Compared with light curves in different observing seasons, variations were found. These variations can be explained by dark spot activities on the surface of at least one component. Using the Wilson-Devinney code with a spot model, we find that the photometric solutions confirm CW Cas is a shallow W-subtype overcontact binary with a spotted massive component. Our new determined times of minimum light together with the others published in the literature were analyzed to find a change of orbital period. From the O - C curves, the period of the system shows a cyclic period change (P 3 = 69.9 yr, A 3 = 0.03196 days) superposed on the linear increase. The cyclic variation, if explained as the light-travel time effect, reveals the presence of a tertiary companion.

  15. Optimal Signal Processing of Frequency-Stepped CW Radar Data

    NASA Technical Reports Server (NTRS)

    Ybarra, Gary A.; Wu, Shawkang M.; Bilbro, Griff L.; Ardalan, Sasan H.; Hearn, Chase P.; Neece, Robert T.

    1995-01-01

    An optimal signal processing algorithm is derived for estimating the time delay and amplitude of each scatterer reflection using a frequency-stepped CW system. The channel is assumed to be composed of abrupt changes in the reflection coefficient profile. The optimization technique is intended to maximize the target range resolution achievable from any set of frequency-stepped CW radar measurements made in such an environment. The algorithm is composed of an iterative two-step procedure. First, the amplitudes of the echoes are optimized by solving an overdetermined least squares set of equations. Then, a nonlinear objective function is scanned in an organized fashion to find its global minimum. The result is a set of echo strengths and time delay estimates. Although this paper addresses the specific problem of resolving the time delay between the two echoes, the derivation is general in the number of echoes. Performance of the optimization approach is illustrated using measured data obtained from an HP-851O network analyzer. It is demonstrated that the optimization approach offers a significant resolution enhancement over the standard processing approach that employs an IFFT. Degradation in the performance of the algorithm due to suboptimal model order selection and the effects of additive white Gaussion noise are addressed.

  16. Optimal Signal Processing of Frequency-Stepped CW Radar Data

    NASA Technical Reports Server (NTRS)

    Ybarra, Gary A.; Wu, Shawkang M.; Bilbro, Griff L.; Ardalan, Sasan H.; Hearn, Chase P.; Neece, Robert T.

    1995-01-01

    An optimal signal processing algorithm is derived for estimating the time delay and amplitude of each scatterer reflection using a frequency-stepped CW system. The channel is assumed to be composed of abrupt changes in the reflection coefficient profile. The optimization technique is intended to maximize the target range resolution achievable from any set of frequency-stepped CW radar measurements made in such an environment. The algorithm is composed of an iterative two-step procedure. First, the amplitudes of the echoes are optimized by solving an overdetermined least squares set of equations. Then, a nonlinear objective function is scanned in an organized fashion to find its global minimum. The result is a set of echo strengths and time delay estimates. Although this paper addresses the specific problem of resolving the time delay between the first two echoes, the derivation is general in the number of echoes. Performance of the optimization approach is illustrated using measured data obtained from an HP-X510 network analyzer. It is demonstrated that the optimization approach offers a significant resolution enhancement over the standard processing approach that employs an IFFT. Degradation in the performance of the algorithm due to suboptimal model order selection and the effects of additive white Gaussion noise are addressed.

  17. Optimizing Frequency-Modulated CW EDMR in silicon

    NASA Astrophysics Data System (ADS)

    Zhu, Lihuang; van Schooten, Kipp; Ramanathan, Chandrasekhar

    Electrically detected magnetic resonance (EDMR) is a powerful method of probing dopant and defect spin states in semiconductor devices. Moreover, at the single dopant level, these spin states are heavily investigated as potential qubit systems, though facile electronic access to single dopants is exceedingly difficult. We therefore characterize detection sensitivities of frequency-modulated CW-EDMR of phosphorus donors in silicon Si:P using a home-built 2.5 GHz system (~80 mT) at 5 K. An arbitrary waveform generator controls the frequency modulation, allowing us to optimize the signal to noise ratio (SNR) of both the dangling bond and phosphorus donor signals against multiple experimental parameters, such as modulation amplitude and modulation frequency. The optimal range of frequency modulation parameters is constrained by the relaxation time of the phosphorous electron at 5 K, resulting in the same sensitivity limit as field modulated CW-EDMR, but offers some technical advantages; e.g. reducing the relative contribution of magnetic field induced currents and eliminating the need for field modulation coils. We further characterize the EDMR SNR in Si:P as a function of optical excitation energy by using a narrow line laser, tunable across donor exciton and band gap states.

  18. Spectra of low-frequency modulation of gyrotron radiation during electron-cyclotron resonance heating of plasma in the L-2M stellarator

    SciTech Connect

    Batanov, G. M.; Kolik, L. V.; Konchekov, E. M.; Malakhov, D. V.; Novozhilova, Yu. V.; Petelin, M. I.; Petrov, A. E.; Pshenichnikov, A. A.; Sarksyan, K. A.; Skvortsova, N. N.; Kharchev, N. K.

    2011-05-15

    Results from experimental studies of the modulation of the gyrotron power during electron cyclotron resonance heating of plasma L-2M stellarator are presented. It is shown that the modulation spectrum consists of separate spectral bands, among which a 20-kHz peak with a spectral density exceeding by one order of magnitude the spectral density of the other peaks is observed. This can be explained by the gyrotron operation being affected by the wave reflected from long-wavelength plasma fluctuations.

  19. Spectra of low-frequency modulation of gyrotron radiation during electron-cyclotron resonance heating of plasma in the L-2M stellarator

    NASA Astrophysics Data System (ADS)

    Batanov, G. M.; Kolik, L. V.; Konchekov, E. M.; Malakhov, D. V.; Novozhilova, Yu. V.; Petelin, M. I.; Petrov, A. E.; Pshenichnikov, A. A.; Sarksyan, K. A.; Skvortsova, N. N.; Kharchev, N. K.

    2011-05-01

    Results from experimental studies of the modulation of the gyrotron power during electron cyclotron resonance heating of plasma L-2M stellarator are presented. It is shown that the modulation spectrum consists of separate spectral bands, among which a 20-kHz peak with a spectral density exceeding by one order of magnitude the spectral density of the other peaks is observed. This can be explained by the gyrotron operation being affected by the wave reflected from long-wavelength plasma fluctuations.

  20. Synthesis of Current-Voltage Characteristics of 670 GHz Gyrotron Magnetron Injection Gun and Calculation of the Helical Electron Beam Parameters at the Leading Edge of a High-Voltage Pulse

    NASA Astrophysics Data System (ADS)

    Manuilov, V. N.; Glyavin, M. Yu.

    2013-02-01

    A method of synthesis of current-voltage characteristics (CVC) and calculation of the parameters of a helical electron beam (HEB) at the leading edge of the accelerating voltage pulse for gyrotron electron guns is proposed. These data can be used for a study of the gyrotron startup scenario with the mode competition taken into account. As an example, the results of calculations for a pulsed gyrotron with a frequency of 670 GHz are presented.

  1. Theory and algorithms for a quasi-optical launcher design method for high-frequency gyrotrons

    NASA Astrophysics Data System (ADS)

    Ungku Farid, Ungku Fazri

    Gyrotrons are vacuum tubes that can generate high amounts of coherent high-frequency microwave radiation used for plasma heating, breakdown and current drive, and other applications. The gyrotron output power is not directly usable, and must be converted to either a free-space circular TEM00 Gaussian beam or a HE11 corrugated waveguide mode by employing mode converters. Quasi-optical mode converters (QOMC) achieve this by utilizing a launcher (a type of waveguide antenna) and a mirror system. Adding perturbations to smooth-wall launchers can produce a better Gaussian shaped radiation pattern with smaller side lobes and less diffraction, and this improvement leads to higher power efficiency in the QOMC. The oversize factor (OF) is defined as the ratio of the operating to cutoff frequency of the launcher, and the higher this value is, the more difficult it is to obtain good launcher designs. This thesis presents a new method for the design of any perturbed-wall TE 0n launcher that is not too highly oversized, and it is an improvement over previous launcher design methods that do not work well for highly oversized launchers. This new launcher design method is a fusion of three different methods, which are the Iterative Stratton-Chu algorithm (used for fast and accurate waveguide field propagations), the Katsenelenbaum-Semenov phase-correcting optimization algorithm, and Geometrical Optics. Three different TE02 launchers were designed using this new method, 1) a highly oversized (2.49 OF) 60 GHz launcher as proof-of-method, 2) a highly oversized (2.66 OF) 28 GHz launcher for possible use in the quasihelically symmetric stellarator (HSX) transmission line at the University of Wisconsin -- Madison, and 3) a compact internal 94 GHz 1.54 OF launcher for use in a compact gyrotron. Good to excellent results were achieved, and all launcher designs were independently verified with Surf3d, a method-of-moments based software. Additionally, the corresponding mirror system for

  2. 60 GHz gyrotron development program. Quarterly report No. 4, April-June 1980

    SciTech Connect

    Shively, J.F.; Grant, T.J.; Stone, D.S.; Symons, R.S.; Wendell, G.E.

    1980-01-01

    The objective of this program is to develop a microwave oscillator capable of producing 200 kW of CW output power at 60 GHz. The use of cyclotron resonance interaction is being pursued. The design and early procurement and construction phases of this program are discussed.

  3. Linear analysis of a coaxial-waveguide gyrotron traveling-wave tube

    SciTech Connect

    Hung, C.L.

    2006-03-15

    Linear theory provides an efficient analysis model for the preliminary design of a gyrotron traveling-wave tube (gyro-TWT). This study presents a linear theory, which is applicable to amplifications or self-excited oscillations induced by absolute instabilities in a coaxial waveguide of finite length. The effects of wall losses are incorporated in the theoretical formalism. The validity of the linear theory is verified by comparison with calculation results obtained using an existing self-consistent nonlinear theory. The linear theory is applied to analyze a TE{sub 01} mode coaxial gyro-TWT at the fundamental cyclotron harmonic. Numerical analysis of coupling between the beam cyclotron mode and the waveguide mode provides physical insight into the wave-growing mechanisms of various oscillations. The critical parameters for the onset of threatening oscillation modes are analyzed to determine the stable operating conditions. Finally, the dependencies of small-signal amplifications on system parameters are studied in great detail.

  4. High-power 140-GHz quasioptical gyrotron traveling-wave amplifier.

    PubMed

    Sirigiri, J R; Shapiro, M A; Temkin, R J

    2003-06-27

    We present the design and experimental results of a novel quasioptical gyrotron traveling-wave tube (gyro-TWT) amplifier at 140 GHz. The gyro-TWT produced up to 30 kW of peak power in 2 micros pulsed operation at 6 Hz achieving a peak gain of 29 dB, a peak efficiency of 12%, and a bandwidth of 2.3 GHz. The device was operated in a very higher-order mode of an open quasioptical interaction structure, namely, a confocal waveguide. The diffraction loss from the open sidewalls of the confocal waveguide was used to suppress mode competition in this highly overmoded circuit resulting in a stable single-mode operation. The experiment achieved record high power levels at 140 GHz for a gyro-TWT. These experiments demonstrate the effectiveness of using overmoded quasioptical waveguide interaction structures for generating high power in the millimeter and submillimeter wave bands with a gyro-TWT. PMID:12857176

  5. On the launching loss and the Weibel instability of the gyrotron traveling wave tube

    SciTech Connect

    Kou, C.S.

    1995-02-01

    A linear theory and a self-consistent theory are used to study the launching loss and the Weibel instability of the gyrotron traveling wave tube (gyro-TWT). Numerical results and a simplified analytical model both show that the launching loss is inversely proportional to the growth rate of the wave, and proportional to the difference between the propagation constant of the forward constant amplitude wave and that of the forward growing wave. In addition, the prediction of the Weibel instability in a fast wave interaction structure by the dispersion relation is verified to be valid even though the assumption of close resonance condition of the linear theory breaks down in this region. Nevertheless, this instability is overwhelmed by the launching loss. {copyright} {ital 1995} {ital American} {ital Institute} {ital of} {ital Physics}.

  6. Magnetron injection gun for a broadband gyrotron backward-wave oscillator

    SciTech Connect

    Yuan, C. P.; Chang, T. H.; Chen, N. C.; Yeh, Y. S.

    2009-07-15

    The magnetron injection gun is capable of generating relativistic electron beam with high velocity ratio and low velocity spread for a gyrotron backward-wave oscillator (gyro-BWO). However, the velocity ratio ({alpha}) varies drastically against both the magnetic field and the beam voltage, which significantly limits the tuning bandwidth of a gyro-BWO. This study remedies this drawback by adding a variable trim field to adjust the magnetic compression ratio when changing the operating conditions. Theoretical results obtained by employing a two-dimensional electron gun code (EGUN) demonstrate a constant velocity ratio of 1.5 with a low axial velocity spread of 6% from 3.4-4.8 Tesla. These results are compared with a three-dimensional particle-tracing code (computer simulation technology, CST). The underlying physics for constant {alpha} will be discussed in depth.

  7. Design of a double-anode magnetron-injection gun for the W-band gyrotron

    NASA Astrophysics Data System (ADS)

    Jang, Kwang Ho; Choi, Jin Joo; So, Joon Ho

    2015-07-01

    A double-anode magnetron-injection gun (MIG) was designed. The MIG is for a W-band 10-kW gyrotron. Analytic equations based on adiabatic theory and angular momentum conservation were used to examine the initial design parameters such as the cathode angle, and the radius of the beam emitting surface. The MIG's performances were predicted by using an electron trajectory code, the EGUN code. The beam spread of the axial velocity, Δvz/vz, obtained from the EGUN code was observed to be 1.34% at α = 1.3. The cathode edge emission and the thermal effect were modeled. The cathode edge emission was found to have a major effect on the velocity spread. The electron beam's quality was significantly improved by affixing non-emissive cylinders to the cathode.

  8. Numerical Design of Megawatt Gyrotron with 120 GHz Frequency and 50% Efficiency for Plasma Fusion Application

    NASA Astrophysics Data System (ADS)

    Kumar, Nitin; Singh, Udaybir; Kumar, Anil; Bhattacharya, Ranajoy; Singh, T. P.; Sinha, A. K.

    2013-02-01

    The design of 120 GHz, 1 MW gyrotron for plasma fusion application is presented in this paper. The mode selection is carried out considering the aim of minimum mode competition, minimum cavity wall heating, etc. On the basis of the selected operating mode, the interaction cavity design and beam-wave interaction computation are carried out by using the PIC code. The design of triode type Magnetron Injection Gun (MIG) is also presented. Trajectory code EGUN, synthesis code MIGSYN and data analysis code MIGANS are used in the MIG designing. Further, the design of MIG is also validated by using the another trajectory code TRAK. The design results of beam dumping system (collector) and RF window are also presented. Depressed collector is designed to enhance the overall tube efficiency. The design study confirms >1 MW output power with tube efficiency around 50% (with collector efficiency).

  9. Analytical theory of low-frequency space charge oscillations in gyrotrons

    SciTech Connect

    Yan Ran; Antonsen, T. M. Jr.; Nusinovich, G. S.

    2008-10-15

    Low-frequency oscillations attributed to reflected electrons bouncing adiabatically between the electron gun and the interaction space have been observed in many gyrotrons. An analytical model is considered which allows one to apply space-charge wave theory to the analysis of these oscillations. In the framework of the small-signal theory, the regions of low-frequency oscillations, the oscillation frequency and the temporal and spatial growth rates of low-frequency oscillations are determined in the relevant parameter space. The mode frequency is determined not only by the particle travel time, but by the travel time of charge waves on the reflected electron beam. This explains the existence of modes with noncommensurate frequencies.

  10. Dynamic nuclear polarization by frequency modulation of a tunable gyrotron of 260 GHz

    NASA Astrophysics Data System (ADS)

    Yoon, Dongyoung; Soundararajan, Murari; Cuanillon, Philippe; Braunmueller, Falk; Alberti, Stefano; Ansermet, Jean-Philippe

    2016-01-01

    An increase in Dynamic Nuclear Polarization (DNP) signal intensity is obtained with a tunable gyrotron producing frequency modulation around 260 GHz at power levels less than 1 W. The sweep rate of frequency modulation can reach 14 kHz, and its amplitude is fixed at 50 MHz. In water/glycerol glassy ice doped with 40 mM TEMPOL, the relative increase in the DNP enhancement was obtained as a function of frequency-sweep rate for several temperatures. A 68 % increase was obtained at 15 K, thus giving a DNP enhancement of about 80. By employing λ / 4 and λ / 8 polarizer mirrors, we transformed the polarization of the microwave beam from linear to circular, and achieved an increase in the enhancement by a factor of about 66% for a given power.

  11. Experiments on a Ku-band gyrotron traveling-wave-tube amplifier with a tapered waveguide

    NASA Astrophysics Data System (ADS)

    Jung, Sang Wook; Lee, Han Seul; Jang, Kwang Ho; Choi, Jin Joo; So, Joon Ho

    2015-09-01

    A Ku-band gyrotron traveling-wave-tube (gyro-TWT) amplifier was investigated. To obtain a wide operating bandwidth, we used a two-stage tapered rectangular waveguide interaction circuit. An electron beam of 27 keV and 3.56 A was produced from a double-anode magnetron-injection-gun (MIG). The measured frequency bandwidth over 10 dB gain in the linear operation region was found to be 18%. The gyro-TWT's saturated output power was 14.9 kW at 14.4 GHz, corresponding to a saturated output power gain of 27.4 dB and an efficiency of 15.5%. The measured experimental results were in agreement with those of non-linear numerical simulations.

  12. Magnetron injection gun for a broadband gyrotron backward-wave oscillator

    NASA Astrophysics Data System (ADS)

    Yuan, C. P.; Chang, T. H.; Chen, N. C.; Yeh, Y. S.

    2009-07-01

    The magnetron injection gun is capable of generating relativistic electron beam with high velocity ratio and low velocity spread for a gyrotron backward-wave oscillator (gyro-BWO). However, the velocity ratio (α) varies drastically against both the magnetic field and the beam voltage, which significantly limits the tuning bandwidth of a gyro-BWO. This study remedies this drawback by adding a variable trim field to adjust the magnetic compression ratio when changing the operating conditions. Theoretical results obtained by employing a two-dimensional electron gun code (EGUN) demonstrate a constant velocity ratio of 1.5 with a low axial velocity spread of 6% from 3.4-4.8 Tesla. These results are compared with a three-dimensional particle-tracing code (computer simulation technology, CST). The underlying physics for constant α will be discussed in depth.

  13. Selective suppression of high order axial modes of the gyrotron backward-wave oscillator

    SciTech Connect

    Pao, K. F.; Fan, C. T.; Chang, T. H.; Chiu, C. C.; Chu, K. R.

    2007-09-15

    Selective suppression of high order axial modes of the gyrotron backward-wave oscillator (gyro-BWO) is investigated in theory and in experiment. The gyro-BWO interaction is much more efficient in a down-tapered interaction structure, while it is also more susceptible to the problem of axial mode competition in such a structure. Because higher order axial modes (at a higher oscillation frequency) penetrate deeper into the interaction structure, application of distributed wall loss at the downstream end of the interaction structure is shown to be effective for selective suppression of these modes with minor effects on the efficiency of the desired fundamental axial mode. A stable gyro-BWO operating in a single mode throughout the entire beam pulse is demonstrated on the basis of this principle. Theoretical and experimental results are found to be in good agreement.

  14. Transition of absolute instability from global to local modes in a gyrotron traveling-wave amplifier.

    PubMed

    Chang, T H; Chen, N C

    2006-07-01

    The gyrotron traveling-wave amplifier employing the distributed-loss scheme is capable of very high gain and effective in suppressing the global absolute instabilities. This study systematically characterizes the local absolute instabilities and their transitional behavior. The local absolute instabilities are analyzed using a model that incorporates the penetration of the field from the copper section into the lossy section. The axial modes were characterized from the perspective of beam-wave interaction and were found to share many characteristics with the global modes. The transition from global modes to local modes as the distributed loss increases was demonstrated. The electron transit angle in the copper section, which determines the feedback criterion, governs the survivability of an oscillation. In addition, the oscillation thresholds predicted using this model are more accurate than those obtained using a simplified model. PMID:16907193

  15. Linear and nonlinear analysis of a gyrotron traveling wave amplifier with misaligned electron beam

    SciTech Connect

    Jiao Chongqing; Luo Jirun

    2006-11-15

    This paper presents linear and self-consistent nonlinear theories to describe the beam-wave interaction in a gyrotron traveling wave amplifier (gyro-TWA) with a misaligned electron beam. A linear theory based on the linearized Vlasov equations is developed by using Laplace transforms. By setting appropriate initial values of the electron guiding center, the nonlinear theory without misalignment can be used to study the misalignment effect. The two theories are in good agreement in the small-signal region for the gyro-TWA. The effects of beam misalignment on the TE{sub 01} mode gyro-TWA operating at the fundamental are discussed and the corresponding physical mechanism is analyzed.

  16. A TE{sub 21} second-harmonic gyrotron backward-wave oscillator with slotted structure

    SciTech Connect

    Chen, N. C.; Yu, C. F.; Chang, T. H.

    2007-12-15

    Second-harmonic gyrotron backward-wave oscillator (gyro-BWO) with a reduced magnetic field strength is a tunable source in the millimeter wave regime, but it has long been impeded by the severe mode competition as a result of low efficiency and narrow bandwidth. This study employs a slotted structure functioning as a mode selective circuit to suppress the lower order transverse modes. In addition, a two-step tapered waveguide is adopted to stabilize the higher-order transverse modes and axial modes. Some important characteristics of the slotted gyro-BWO will be analyzed and discussed. As a calculated result, the interaction efficiency is improved and the stable tuning range is broadened. A stable, Ka-band, slotted second-harmonic gyro-BWO is capable of producing an efficiency of 23% with a 3 dB tuning bandwidth of 9% at 5 A and 100 kV.

  17. Development of a novel high power sub-THz second harmonic gyrotron.

    PubMed

    Notake, T; Saito, T; Tatematsu, Y; Fujii, A; Ogasawara, S; Agusu, La; Ogawa, I; Idehara, T; Manuilov, V N

    2009-11-27

    Record-breaking high power coherent radiation at a subterahertz frequency region from a gyrotron utilizing second harmonic resonance modes was attained with a simple cavity. In order to aim at high power and high frequency simultaneously, the oscillation mode was selected carefully enough to realize stable radiation free from mode competition. The cavity radius was determined from the viewpoints of the oscillation frequency, the coupling coefficient between the electron beam, and the rf-electric field. The cavity length was also optimized for the highest perpendicular efficiency. In addition, a new electron gun which is capable of generating a thin laminar beam for a large current was introduced. Consequently, single mode second harmonic radiation with powers of 52 and 37 kW at frequencies of about 349 and 390 GHz, respectively, was achieved. PMID:20366101

  18. W-band TE{sub 01} gyrotron backward-wave oscillator with distributed loss

    SciTech Connect

    Chang, T. H.; Yu, C. F.; Hung, C. L.; Yeh, Y. S.; Hsiao, M. C.; Shin, Y. Y.

    2008-07-15

    Distributed wall loss is proposed to enhance the stability and tunability of a W-band TE{sub 01} gyrotron backward-wave oscillator (gyro-BWO). Simulation results reveal that loss effectively suppresses the unwanted transverse modes as well as the high-order axial modes (HOAMs) without degrading the performance of a gyro-BWO that operates at the fundamental axial mode. Linear and nonlinear codes are used to calculate the interaction properties. The effects of the distributed loss on the starting currents of all of the modes of interest are discussed in depth. The interacting structure is optimized for stability. The calculated peak output power is 102 kW, corresponding to an efficiency of 20%. The 3 dB tuning bandwidth is 1.8 GHz, centered at 94.0 GHz when using 5 A and 100 kV electron beam.

  19. High power wideband gyrotron backward wave oscillator operating towards the terahertz region.

    PubMed

    He, W; Donaldson, C R; Zhang, L; Ronald, K; McElhinney, P; Cross, A W

    2013-04-19

    Experimental results are presented of the first successful gyrotron backward wave oscillator (gyro-BWO) with continuous frequency tuning near the low-terahertz region. A helically corrugated interaction region was used to allow efficient interaction over a wide frequency band at the second harmonic of the electron cyclotron frequency without parasitic output. The gyro-BWO generated a maximum output power of 12 kW when driven by a 40 kV, 1.5 A, annular-shaped large-orbit electron beam and achieved a frequency tuning band of 88-102.5 GHz by adjusting the cavity magnetic field. The performance of the gyro-BWO is consistent with 3D particle-in-cell numerical simulations. PMID:23679610

  20. Development of a Novel High Power Sub-THz Second Harmonic Gyrotron

    SciTech Connect

    Notake, T.; Saito, T.; Tatematsu, Y.; Fujii, A.; Ogasawara, S.; Agusu, La; Ogawa, I.; Idehara, T.; Manuilov, V. N.

    2009-11-27

    Record-breaking high power coherent radiation at a subterahertz frequency region from a gyrotron utilizing second harmonic resonance modes was attained with a simple cavity. In order to aim at high power and high frequency simultaneously, the oscillation mode was selected carefully enough to realize stable radiation free from mode competition. The cavity radius was determined from the viewpoints of the oscillation frequency, the coupling coefficient between the electron beam, and the rf-electric field. The cavity length was also optimized for the highest perpendicular efficiency. In addition, a new electron gun which is capable of generating a thin laminar beam for a large current was introduced. Consequently, single mode second harmonic radiation with powers of 52 and 37 kW at frequencies of about 349 and 390 GHz, respectively, was achieved.

  1. Nonlinear oscillation behavior of a driven gyrotron backward-wave oscillator

    SciTech Connect

    Yeh, Y. S.; Jhou, J. N.; Huang, J. M.; Shiao, J. L.; Wu, Z. Q.; Chang, T. H.; Fan, C. T.; Chiu, C. C.; Hung, C. L.

    2010-11-15

    Controlling the phase and frequency of a gyrotron backward-wave oscillator (gyro-BWO) by means of injection-locking techniques is of practical importance. This study employed a nonlinear self-consistent time-independent code to analyze the nonlinear oscillation behavior of a driven gyro-BWO. There are three regimes in the driven gyro-BWO, including amplification, injection-locked oscillation, and mode competition regimes. Based on the theory of nonlinear oscillation, the amplification and injection-locked oscillation modes are the stable modes and compete with each other in the mode competition regime. An oscillator plane of the driven gyro-BWO is elucidated in the paper. This work demonstrates for the first time that the amplification mode transits to the injection-locked oscillation mode in the driven gyro-BWO. Moreover, the signification efficiency enhancement of the driven gyro-BWO over the free-running efficiency is found.

  2. Linear theory of large-orbit gyrotron traveling wave amplifiers with misaligned electron beam

    SciTech Connect

    Jiao Chongqing; Luo Jirun

    2010-11-15

    A linear theory of large-orbit gyrotron traveling wave amplifiers (gyro-TWAs), which can be applied to analyze the effect of electron beam misalignment, is developed by specializing the corresponding theory of small-orbit gyro-TWAs. The linear theory is validated by comparing with a nonlinear theory. Numerical results show that beam misalignment can reduce linear gain and amplification bandwidth of large-orbit gyro-TWAs and increase the starting length of large-orbit gyro-BWOs for modes in accordance with the mode-selective condition. In addition, beam misalignment can also break the limitation of mode-selective condition and make the instability problem more complex.

  3. Dynamic nuclear polarization by frequency modulation of a tunable gyrotron of 260GHz.

    PubMed

    Yoon, Dongyoung; Soundararajan, Murari; Cuanillon, Philippe; Braunmueller, Falk; Alberti, Stefano; Ansermet, Jean-Philippe

    2016-01-01

    An increase in Dynamic Nuclear Polarization (DNP) signal intensity is obtained with a tunable gyrotron producing frequency modulation around 260GHz at power levels less than 1W. The sweep rate of frequency modulation can reach 14kHz, and its amplitude is fixed at 50MHz. In water/glycerol glassy ice doped with 40mM TEMPOL, the relative increase in the DNP enhancement was obtained as a function of frequency-sweep rate for several temperatures. A 68 % increase was obtained at 15K, thus giving a DNP enhancement of about 80. By employing λ/4 and λ/8 polarizer mirrors, we transformed the polarization of the microwave beam from linear to circular, and achieved an increase in the enhancement by a factor of about 66% for a given power. PMID:26759116

  4. The coaxial gyrotron with two electron beams. II. Dual frequency operation

    SciTech Connect

    Liu Shenggang; Yuan Xuesong; Liu Diwei; Yan Yang; Zhang Yaxin; Li Hongfu; Zhong Renbin

    2007-10-15

    The dual frequency operation (DFO) of the coaxial gyrotron with two electron beams (CGTB) has been investigated in this part by means of both linear theory and computer simulation. In such an operation, the cavity is at degeneration and one beam works at the first harmonic while another at high harmonic. Making use of the coupled-mode theory, the dispersion equation considering the coupling of two beams and two modes has been obtained. The results of the numerical calculation and the particle in cell simulation show that CGTB with DFO can obtain high output power at two different frequencies simultaneously. In addition, the power of the high harmonic can be enhanced due to the nonlinear coupling between two beams, and some interesting and important phenomena of CGTB with DFO revealed in the paper are of significance in physics.

  5. Nonstationary oscillation of gyrotron backward wave oscillators with cylindrical interaction structure

    SciTech Connect

    Chen, Shih-Hung; Chen, Liu

    2013-12-15

    The nonstationary oscillation of the gyrotron backward wave oscillator (gyro-BWO) with cylindrical interaction structure was studied utilizing both steady-state analyses and time-dependent simulations. Comparisons of the numerical results reveal that the gyro-BWO becomes nonstationary when the trailing field structure completely forms due to the dephasing energetic electrons. The backward propagation of radiated waves with a lower resonant frequency from the trailing field structure interferes with the main internal feedback loop, thereby inducing the nonstationary oscillation of the gyro-BWO. The nonstationary gyro-BWO exhibits the same spectral pattern of modulated oscillations with a constant frequency separation between the central frequency and sidebands throughout the whole system. The frequency separation is found to be scaled with the square root of the maximum field amplitude, thus further demonstrating that the nonstationary oscillation of the gyro-BWO is associated with the beam-wave resonance detuning.

  6. Precision characterization of gyrotron window materials. Final report, September 1, 1995--April 30, 1997

    SciTech Connect

    Dutta, J.M.; Jones, C.R.

    1998-03-03

    An optical resonator has been constructed to measure dielectric properties of materials at millimeter wavelengths. The objectives are the identification and loss measurements of window materials for high power gyrotrons. The source of radiation is from a backward wave oscillator (BWO) with enhanced power, good stability, and spectral purity. The measurement technique is based on the application of a high Q Fabry-Perot resonator which provides a means of determining the difference in the reciprocal Q-factors with high accuracy. Initial loss measurements at 150 GHz at room temperature are performed on sapphire. Preliminary loss tangent results on sapphire is found to be around 10{sup {minus}4} and are reported here. Work is in progress to develop a system which will scan the resonance rapidly to produce a measurement in less than a minute and to measure the loss as a function of temperature.

  7. High Power Wideband Gyrotron Backward Wave Oscillator Operating towards the Terahertz Region

    NASA Astrophysics Data System (ADS)

    He, W.; Donaldson, C. R.; Zhang, L.; Ronald, K.; McElhinney, P.; Cross, A. W.

    2013-04-01

    Experimental results are presented of the first successful gyrotron backward wave oscillator (gyro-BWO) with continuous frequency tuning near the low-terahertz region. A helically corrugated interaction region was used to allow efficient interaction over a wide frequency band at the second harmonic of the electron cyclotron frequency without parasitic output. The gyro-BWO generated a maximum output power of 12 kW when driven by a 40 kV, 1.5 A, annular-shaped large-orbit electron beam and achieved a frequency tuning band of 88-102.5 GHz by adjusting the cavity magnetic field. The performance of the gyro-BWO is consistent with 3D particle-in-cell numerical simulations.

  8. Control of soliton train transmission, storage, and clock recovery by cw light injection

    NASA Astrophysics Data System (ADS)

    Wabnitz, S.

    1996-12-01

    The Gordon-Haus time jitter and the soliton-soliton interactions in a soliton fiber loop memory or in a transmission link may be suppressed by the periodic injection of a weak cw control beam. In the case of a fiber ring cavity cw injection may also permit clock regeneration from a randomly modulated soliton train. .

  9. The 1.083 micron tunable CW semiconductor laser

    NASA Technical Reports Server (NTRS)

    Wang, C. S.; Chen, Jan-Shin; Lu, Ken-Gen; Ouyang, Keng

    1991-01-01

    A tunable CW laser is desired to produce light equivalent to the helium spectral line at 1.08 microns. This laser will serve as an optical pumping source for He-3 and He-4 atoms used in space magnetometers. This light source can be fabricated either as a semiconductor laser diode or a pumped solid state laser. Continuous output power of greater than 10 mW is desired. Semiconductor lasers can be thermally tuned, but must be capable of locking onto the helium resonance lines. Solid state lasers must have efficient pumping sources suitable for space configuration. Additional requirements are as follows: space magnetometer applications will include low mass (less than 0.5 kg), low power consumption (less than 0.75 W), and high stability/reliability for long missions (5-10 years).

  10. Concepts for the JLab Ampere-Class CW Cryomodule

    SciTech Connect

    R. Rimmer; E.F. Daly; W.R. Hicks; J. Henry; J. Preble; M. Stirbet; H. Wang; K.M. Wilson; G. Wu

    2005-05-01

    We describe the concepts and developments underway at JLab as part of the program to develop a new CW cryomodule capable of transporting ampere-level beam currents in a compact FEL. Requirements include real-estate gradient of at least 10 MV/m and very strong HOM damping to push BBU thresholds up by two or more orders of magnitude compared to existing designs. Cavity shape, HOM damping, power couplers, tuners etc. are being designed and optimized for this application. Cavity considerations include a large iris for beam halo, low-RF losses, HOM frequencies and Q's, low peak surface fields, field flatness and microphonics. Module considerations include high packing factor, low static heat leak, image current heating of beam-line components, cost and maintainability. This module is being developed for the next generation ERL based high power FELs but may be useful for other applications such as electron cooling, electron-ion colliders, industrial processing etc.

  11. CW laser generated ultrasound techniques for microstructure material properties evaluation

    NASA Astrophysics Data System (ADS)

    Thursby, Graham; Culshaw, Brian; Pierce, Gareth; Cleary, Alison; McKee, Campbell; Veres, Istvan

    2009-03-01

    Mechanical properties of materials may be obtained from the inversion of ultrasonic Lamb wave dispersion curves. In order to do this broadband excitation and detection of ultrasound is required. As sample size and, in particular, thickness, are reduced to those of microstructures, ultrasound frequencies in the range of the gigahertz region will be required. We look at two possible cw laser excitation techniques which, having far lower peak powers than the more frequently used Q-switched lasers, therefore give a negligible risk of damaging the sample through ablation. In the first method the modulation frequency of a sinusoidally modulated laser is swept over the required range. In the second, the laser is modulated with a series of square pulses whose timing is given by a PRBS (pseudo random binary sequence) in the form of a modified m-sequence.

  12. Low power cw-laser signatures on human skin

    SciTech Connect

    Lihachev, A; Lesinsh, J; Jakovels, D; Spigulis, J

    2011-01-24

    Impact of cw laser radiation on autofluorescence features of human skin is studied. Two methods of autofluorescence detection are applied: the spectral method with the use of a fibreoptic probe and spectrometer for determining the autofluorescence recovery kinetics at a fixed skin area of {approx}12 mm{sup 2}, and the multispectral visualisation method with the use of a multispectral imaging camera for visualising long-term autofluorescence changes in a skin area of {approx}4 cm{sup 2}. The autofluorescence recovery kinetics after preliminary laser irradiation is determined. Skin autofluorescence images with visible long-term changes - 'signatures' of low power laser treatment are acquired. (application of lasers and laser-optical methods in life sciences)

  13. Operational experience with CW high gradient and high QL cryomodules

    SciTech Connect

    Hovater, J. Curt; Allison, Trent L.; Bachimanchi, Ramakrishna; Daly, Edward F.; Drury, Michael A.; Lahti, George E.; Mounts, Clyde I.; Nelson, Richard M.; Plawski, Tomasz E.

    2014-12-01

    The Continuous Electron Beam Accelerator Facility (CEBAF) energy upgrade from 6 GeV to 12 GeV includes the installation of ten new 100 MV cryomodules (80 cavities). The superconducting RF cavities are designed to operate CW at an accelerating gradient of 19.3 MV/m with a QL of 3×107. The RF system employs single cavity control using new digital LLRF controls and 13 kW klystrons. Recently, all of the new cryomodules and associated RF hardware and software have been commissioned and operated in the CEBAF accelerator. Electrons at linac currents up to 10 ?A have been successfully accelerated and used for nuclear physics experiments. This paper reports on the commissioning and operation of the cryomodules and RF system.

  14. The reliability of /AlGa/As CW laser diodes

    NASA Astrophysics Data System (ADS)

    Ettenberg, M.; Kressel, H.

    1980-02-01

    Major factors bearing on the reliability of (AlGa)As CW laser diodes are reviewed with attention given to the degradation modes of facet mirror damage, contact degradation, and internal damage. Detailed results are provided for the oxide-defined stripe-contact double-heterojunction lasers operated for more than 40,000 h with extrapolations indicating a median time to failure between 100,000 and 1,000,000. Facet damage and contact degradation appear to be under control, and internal damage remains the dominant failure mechanism. Most of the data deals with threshold current increase; however, shifts in far-field pattern and changes in laser modulation characteristics, including self-sustained oscillations, may affect laser performance in real systems.

  15. Parametric four-wave mixing using a single cw laser.

    PubMed

    Brekke, E; Alderson, L

    2013-06-15

    Four-wave mixing can be used to generate coherent output beams, with frequencies difficult to acquire in commercial lasers. Here, a single narrow external cavity diode laser locked to the two photon 5s-5d transition in rubidium is combined with a tapered amplifier system to produce a high power cw beam at 778 nm and used to generate coherent light at 420 nm through parametric four-wave mixing. This process is analyzed in terms of the intensity and frequency of the incoming beam as well as the atomic density of the sample. The efficiency of the process is currently limited when on resonance due to the absorption of the 420 nm beam, and modifications should allow a significant increase in output power. PMID:23939005

  16. Characterization of a THz CW spectrometer pumped at 1550 nm

    NASA Astrophysics Data System (ADS)

    Yeo, Woon-Gi; Nahar, Niru K.

    2015-07-01

    We present an evaluation of a cost-effective THz CW spectrometer pumped at 1550 nm wavelengths with a fixed delay line. To study the spectral competence of the spectrometer, transmission data is obtained for various organic and inorganic samples. Spectral comparisons of the samples are presented by using THz time domain spectroscopy and vector network analyzer (VNA). Despite the capability of highly resolved transmission spectroscopy, our current system reveals the uncertainty in interferometric output data for phase analysis. Here, we identify the effect of fringing space of raw output data toward frequency resolution, phase analysis, and data acquisition time. We also propose the proper delay line setup for phase analysis for this type of spectrometers.

  17. Quasi-cw tissue transillumination at 1064 nm

    NASA Astrophysics Data System (ADS)

    Bernini, Umberto; Ramaglia, Antonio; Russo, Paolo

    1997-08-01

    An extended series of transillumination experiments has been performed in vitro on animal samples (bovine muscle, up to 30- mm-thick; chicken wing and quail femur, 12-mm-thick) and in vivo on the human hand (thickness, about 20 mm), using a pulsed light source (7 ns, about 10-4 J/pulse, 10 Hz rep rate) from a collimated (1.2 m) Nd:YAG laser beam (1064 nm). A PIN photodiode connected to a digital oscilloscope was used to measure the maximum intensity of the beam pulse transmitted through the sample (i.e., no temporal discrimination of the output signal was attempted) while it was scanned across the source/detector assembly. One dimensional scans were performed on bovine muscle samples in which thin metallic test objects were embedded, in order to study the spatial resolution of the technique (for bovine muscle at 1064 nm, absorption and reduced scattering coefficients are reported to be about 1 cm-1 and 3 cm-1, respectively). The measured spatial resolution was as good as 3.6 mm in 30 mm of tissue thickness. In the two-dimensional scans of the chicken and quail sample, fat and bone tissues can be easily seen with good resolution, whereas imaging of the middle finger of a human hand shows cartilaginoid and bone tissue with 1 - 2 mm resolution. Hence, this simple collimated quasi-cw technique gives significantly better results for tissue imaging than pure cw transillumination. Use of (pulsed) light above 1000 nm and a high energy content per pulse are supposed to explain the positive experimental findings.

  18. Experimental Study of a Gyrotron with a Sectioned Klystron-Type Cavity Operated at Higher Cyclotron Harmonics

    NASA Astrophysics Data System (ADS)

    Bandurkin, I. V.; Kalynov, Yu. K.; Savilov, A. V.

    2016-02-01

    We are planning to use extended cavities in order to excite gyrotrons with large electron orbits, which are operated at higher cyclotron harmonics in the terahertz frequency range. This is determined by both the weakness of the electron-wave interaction, and relatively low operating currents. Since the diffraction Q-factor of such cavities is high, a significant part of the highfrequency power produced by the electron beam is lost due to the ohmic loss in the cavity walls. As a way to solve this problem, we proposed a sectioned klystron-type cavity, where an extended length of the electron-wave interaction region can be combined with a relatively low diffraction Q-factor of the system. This work presents the results of the first experiment on a gyrotron with a sectioned cavity, where selective excitation of higher (second and third) cyclotron harmonics was observed in the terahertz frequency range (0 .55 and 0 .74 THz).

  19. Nanosecond pulses in a THz gyrotron oscillator operating in a mode-locked self-consistent Q-switch regime.

    PubMed

    Alberti, S; Braunmueller, F; Tran, T M; Genoud, J; Hogge, J-Ph; Tran, M Q; Ansermet, J-Ph

    2013-11-15

    An experimental study of a nanosecond pulsed regime in a THz gyrotron oscillator operating in a self-consistent Q-switch regime has been carried out. The gyrotron is operated in the TE(7,2) transverse mode radiating at a frequency of 260.5 GHz. The 5 W nanosecond pulses are obtained in a self-consistent Q-switch regime in which the cavity diffraction quality factor dynamically varies by nearly 2 orders of magnitude on a subnanosecond time scale via the nonlinear interaction of different mode-locked frequency-equidistant sidebands. The experimental results are in good agreement with numerical simulations performed with the TWANG code based on a slow time scale formulation of the self-consistent time-dependent nonlinear wave particle interaction equations. PMID:24289692

  20. A Numerical Study on Finite-Bandwidth Resonances of High-Order Axial Modes (HOAM) in a Gyrotron Cavity

    NASA Astrophysics Data System (ADS)

    Sabchevski, Svilen Petrov; Idehara, Toshitaka

    2015-07-01

    Many novel and prospective applications of the gyrotrons as sources of coherent radiation require a broadband and continuous frequency tunability. A promising and experimentally proven technique to achieve it is based on a successive excitation of a sequence of high-order axial modes (HOAM) in the cavity resonator. Therefore, the studies on HOAM are of both theoretical and practical importance and interest. In this paper, we present and discuss the methods and the results of a numerical investigation on the resonances of HOAM in a typical open gyrotron cavity. The simulations have been performed using the existing as well as novel computational modules of the problem-oriented software package GYROSIM (GYROtron SIMulation) for solution of both the homogeneous and the inhomogeneous Helmholtz equation with radiation boundary conditions, which governs the field amplitude along the axis of the resonant structure. The frequency response of the cavity is studied by analyzing several resonance curves (spectral domain analysis) obtained from the numerical solution of the boundary value problem for the inhomogeneous Helmholtz equation with a predefined source term (excitation) by the finite-difference method (FDM). The approach proposed here allows finite-bandwidth resonances of HOAM to be identified and represented on the dispersion diagram of the cavity mode as bands rather than as discrete points, in contrast to the frequently used physical models that neglect the finite width of these resonances. Developed numerical procedures for calculation of the field profiles for an arbitrary frequency and excitation will be embedded in the cold cavity and self-consistent codes of the GYROSIM package in order to study the beam-wave interaction and energy transfer in gyrotron cavities.

  1. Upgraded Waveguide Components for New 1.2 and 1.5 MW Gyrotrons on the DIII-D Tokamak

    NASA Astrophysics Data System (ADS)

    Gorelov, Y. A.; Doane, J. L.; Cengher, M.; Lohr, J.; Ponce, D.

    2012-10-01

    The present gyrotron system on the DIII-D tokamak comprises 110 GHz gyrotrons in the 1 MW class with designed pulse lengths of 10 s. The system is being upgraded with two types of depressed collector gyrotrons producing 1.2 MW at 110 GHz and 1.5 MW at 117.5 GHz, for which waveguide components having higher power ratings will be required. New power monitors and polarizers have been designed and fabricated, which are capable of operating for 10 s pulses at the higher power levels. This presentation reports an analysis of the component heat loading to obtain a thermal equilibrium. Using this equilibrium, a stress strain analysis was performed to calculate life expectancies. The calculations take into account the temperature dependence of the heat transfer coefficient in the component coolant channels. Although the high heat load components required upgrading, the waveguide lines themselves have adequate margins for the expected power and pulse length. A summary of the thermal capabilities of other components will also be presented.

  2. Picosecond Measurements with Mode-Locked CW Lasers.

    NASA Astrophysics Data System (ADS)

    Mosaad, Neamat Roushdy M.

    Available from UMI in association with The British Library. Requires signed TDF. The characteristics of output pulses from a synchronously and hybridly mode-locked CW Rhodamine 6G dye laser were studied in detail by both spectral and temporal measurements. In a synchronous system, the observed spectrum was found to change from deeply channelled to nearly smooth according to the position of the birefringent filter. The output pulses were nearly transform-limited and believed to have a single-sided exponential shape. Hybridly CW mode-locked dye laser was a more reliable source for generating broadly tunable subpicosecond pulses, compared to a synchronously mode-locked laser. With carefull adjustment of the dye laser and the saturable absorber concentration (DQOCI) mixed with R6G in a single dye jet stream, pulses as short as 0.21 ps have been obtained with a compression factor of 5. The observed spectrum showed asymmetric broadening at the long-wavelength side alone. The SHG autocorrelation traces showed broad wings with exponential-like shape. The time-bandwidth product for these pulses were about three to seven times larger than that for the transform-limited pulse with single-sided exponential shape. This suggest that the pulse is largely frequency-chirped which can consistently be explained by taking into account the nonlinear process of self-phase modulation due to optical Kerr effect in a mixed dye jet stream. The timing pulse jitter was reduced by a factor of 2.4 due to mode-locking stabilization. Optical pulse compression utilizing nonlinear propagation in single-mode fibres was studied. The propagation in the fibre broadens and chirps the pulse due to the combined action of group velocity dispersion and self-phase modulation. The channelled spectrum disappeared completely and a smooth Gaussian shape was observed with the same overall width. The pulse can then be compressed by passage through a suitable dispersive delay line. Short pulses were obtained with a

  3. Effect of a weak CW trigger on optical rogue waves in the femtosecond supercontinuum generation.

    PubMed

    Li, Qian; Duan, Xiaoqi

    2015-06-15

    We numerically study the characteristics of optical rogue waves in the femtosecond supercontinuum (SC) generation and use the CW triggering mechanism to control the SC generation. Detailed simulation results show for the first time that a weak CW trigger can manipulate the behaviors of optical rogue waves in the femtosecond SC regime. For the proposed CW triggering technique which requires only wavelength tuning and is a handy approach for the active control of SC, the resultant spectrum can be greatly broadened, and the noise properties of the SC can be significantly improved in terms of both of the coherence and intensity stability. PMID:26193609

  4. Adapting TESLA technology for future cw light sources using HoBiCaT.

    PubMed

    Kugeler, O; Neumann, A; Anders, W; Knobloch, J

    2010-07-01

    The HoBiCaT facility has been set up and operated at the Helmholtz-Zentrum-Berlin and BESSY since 2005. Its purpose is testing superconducting cavities in cw mode of operation and it was successfully demonstrated that TESLA pulsed technology can be used for cw mode of operation with only minor changes. Issues that were addressed comprise of elevated dynamic thermal losses in the cavity walls, necessary modifications in the cryogenics and the cavity processing, the optimum choice of operational parameters such as cavity temperature or bandwidth, the characterization of higher order modes in the cavity, and the usability of existing tuners and couplers for cw. PMID:20687747

  5. Adapting TESLA technology for future cw light sources using HoBiCaT

    NASA Astrophysics Data System (ADS)

    Kugeler, O.; Neumann, A.; Anders, W.; Knobloch, J.

    2010-07-01

    The HoBiCaT facility has been set up and operated at the Helmholtz-Zentrum-Berlin and BESSY since 2005. Its purpose is testing superconducting cavities in cw mode of operation and it was successfully demonstrated that TESLA pulsed technology can be used for cw mode of operation with only minor changes. Issues that were addressed comprise of elevated dynamic thermal losses in the cavity walls, necessary modifications in the cryogenics and the cavity processing, the optimum choice of operational parameters such as cavity temperature or bandwidth, the characterization of higher order modes in the cavity, and the usability of existing tuners and couplers for cw.

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

    SciTech Connect

    Zhao, Qixiang Yu, Sheng; Zhang, Tianzhong; Li, Xiang

    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.

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

    NASA Astrophysics Data System (ADS)

    Zhao, Qixiang; Yu, Sheng; Li, Xiang; Zhang, Tianzhong

    2015-10-01

    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.

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

    NASA Astrophysics Data System (ADS)

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

    2015-03-01

    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 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.

  9. Investigation of RF excited CW CO2 waveguide lasers

    NASA Technical Reports Server (NTRS)

    Hochuli, U.

    1984-01-01

    The RF excited 2 to 3W CW CO2 waveguide lasers with lifetimes of the order of 10(4) to 2.10(4) hours were produced. This was achieved with CO and N2 bearing gas mixtures and with internal as well as external discharge electrodes. It is noted that these tests were conducted with unstabilized lasers which drift around in their signatures. The average power output was reduced to about one half of the highest peak power output in the signature. One of the lasers, no. 1.1, still shows 60% of its original output power after it was cycled on and off every 10 minutes for more than 50,000 times. The starting voltage and driving point impedance of the RF excited gas discharge structure for different gas pressures and mixtures were measured. These data will serve as a basis for the matching and starting network optimization. The second laser body was frit and indium sealed. To our a vacuum leak between the bore and electrode holes was noted. The leak seems to be due to a defect or crack in the BeO body.

  10. CW high intensity non-scaling FFAG proton drivers

    SciTech Connect

    Johnstone, C.; Berz, M.; Makino, K.; Snopok, P.; /IIT, Chicago

    2011-04-01

    Accelerators are playing increasingly important roles in basic science, technology, and medicine including nuclear power, industrial irradiation, material science, and neutrino production. Proton and light-ion accelerators in particular have many research, energy and medical applications, providing one of the most effective treatments for many types of cancer. Ultra high-intensity and high-energy (GeV) proton drivers are a critical technology for accelerator-driven sub-critical reactors (ADS) and many HEP programs (Muon Collider). These high-intensity GeV-range proton drivers are particularly challenging, encountering duty cycle and space-charge limits in the synchrotron and machine size concerns in the weaker-focusing cyclotrons; a 10-20 MW proton driver is not presently considered technically achievable with conventional re-circulating accelerators. One, as-yet, unexplored re-circulating accelerator, the Fixed-field Alternating Gradient, or FFAG, is an attractive alternative to the cyclotron. Its strong focusing optics are expected to mitigate space charge effects, and a recent innovation in design has coupled stable tunes with isochronous orbits, making the FFAG capable of fixed-frequency, CW acceleration, as in the classical cyclotron. This paper reports on these new advances in FFAG accelerator technology and references advanced modeling tools for fixed-field accelerators developed for and unique to the code COSY INFINITY.

  11. Proton Injector for CW-Mode Linear Accelerators

    NASA Astrophysics Data System (ADS)

    Sherman, Joseph D.; Swenson, Donald; Guy, Frank; Love, Cody; Starling, Joel; Willis, Carl

    2009-03-01

    Numerous applications exist for CW linear accelerators with final energies in the 0.5 to 4.0 MeV proton energy range. Typical proton current at the linac output energy is 20 mA. An important subsystem for the accelerator facility is a reliable dc mode proton injector. We present here design and laboratory results for a dc, 25-keV, 30-mA proton injector. The proton source is a 2.45-GHz microwave hydrogen ion source which operates with an 875-G axial magnetic field. Low emittance, high proton fraction (>85%), beams have been demonstrated from this source. The injector uses a novel dual-solenoid magnet for matching the injector beam into a radio frequency quadrupole (RFQ) linear accelerator. Recently, a dc ion-source development program has given up to 30 mA beam current. The dual solenoid is a compact and simple design utilizing tape-wound, edge-cooled coils. The low-energy beam transport design as well as 25-keV beam matching calculations to an RFQ will also be presented.

  12. Transpupillary CW YAG laser coagulation. A comparison with argon green and krypton red lasers.

    PubMed

    Peyman, G A; Conway, M D; House, B

    1983-08-01

    The authors have developed a CW YAG laser for transpupillary coagulation. The effects of CW YAG coagulation on the retina, retinal vessels, and fovea were compared with those produced by the krypton red and argon green lasers. To produce threshold coagulative lesions in monkeys and rabbits, we needed five to ten times more energy with the CW YAG than with the krypton red or argon green lasers. Nerve fiber damage was observed only when coagulating retinal vessels with the argon green laser. At the parameters used, none of the lasers damaged the sensory retina of the fovea. The CW YAG may be used as a new mode of laser coagulation in the treatment of retinal diseases. PMID:6688868

  13. Draft Genome Sequences of Ralstonia pickettii Strains SSH4 and CW2, Isolated from Space Equipment.

    PubMed

    Monsieurs, Pieter; Mijnendonckx, Kristel; Provoost, Ann; Venkateswaran, Kasthuri; Ott, C Mark; Leys, Natalie; Van Houdt, Rob

    2014-01-01

    Ralstonia pickettii SSH4 and CW2 were isolated from space equipment. Here, we report their draft genome sequences with the aim of gaining insight into their potential to adapt to these environments. PMID:25189592

  14. Draft Genome Sequences of Ralstonia pickettii Strains SSH4 and CW2, Isolated from Space Equipment

    PubMed Central

    Monsieurs, Pieter; Mijnendonckx, Kristel; Provoost, Ann; Venkateswaran, Kasthuri; Ott, C. Mark; Leys, Natalie

    2014-01-01

    Ralstonia pickettii SSH4 and CW2 were isolated from space equipment. Here, we report their draft genome sequences with the aim of gaining insight into their potential to adapt to these environments. PMID:25189592

  15. Design of collective Thomson scattering system using 77 GHz gyrotron for bulk and tail ion diagnostics in the large helical device

    SciTech Connect

    Nishiura, M.; Tanaka, K.; Kubo, S.; Kawahata, K.; Shimozuma, T.; Mutoh, T.; Saito, T.; Tatematsu, Y.; Notake, T.

    2008-10-15

    Collective Thomson scattering (CTS) system is expected to be a strong diagnostic tool for measuring thermal and fast ion distribution function at a local point inside plasmas. The electron cyclotron resonance heating system using a gyrotron at the frequency range of 77 GHz has been installed at the large helical device (LHD). The feasibility of CTS system using the 77 GHz gyrotron is assessed in terms of scattering spectrum and a background noise of the electron cyclotron emission, which affect the signal to noise ratio, with the realistic plasma parameters and incident port locations of LHD. Based on the calculated scattering spectra for bulk and tail fast ion diagnostics, the scattering radiation receiver system with gyrotron frequency feedback circuit is proposed to avoid the frequency chirping.

  16. Design of collective Thomson scattering system using 77 GHz gyrotron for bulk and tail ion diagnostics in the large helical device.

    PubMed

    Nishiura, M; Tanaka, K; Kubo, S; Saito, T; Tatematsu, Y; Notake, T; Kawahata, K; Shimozuma, T; Mutoh, T

    2008-10-01

    Collective Thomson scattering (CTS) system is expected to be a strong diagnostic tool for measuring thermal and fast ion distribution function at a local point inside plasmas. The electron cyclotron resonance heating system using a gyrotron at the frequency range of 77 GHz has been installed at the large helical device (LHD). The feasibility of CTS system using the 77 GHz gyrotron is assessed in terms of scattering spectrum and a background noise of the electron cyclotron emission, which affect the signal to noise ratio, with the realistic plasma parameters and incident port locations of LHD. Based on the calculated scattering spectra for bulk and tail fast ion diagnostics, the scattering radiation receiver system with gyrotron frequency feedback circuit is proposed to avoid the frequency chirping. PMID:19044547

  17. Attogram measurement of rare isotopes by CW resonance ionization mass spectrometry

    SciTech Connect

    Bushaw, B.A.

    1992-05-01

    Three-color double-resonance ionization mass spectrometry, using two single-frequency cw dye lasers and a cw carbon dioxide laser, has been applied to the detection of attogram quantities of rare radionuclides. {sup 210}Pb has been measured in human hair and brain tissue samples to assess indoor radon exposure. Measurements on {sup 90}Sr have shown overall isotopic selectivity of greater than 10{sup 9} despite unfavorable isotope shifts relative to the major stable isotope, {sup 88}Sr.

  18. Natural gas leaks detection by spatial-resolvable-CW-laser-based remote monitoring

    SciTech Connect

    Agishev, R.R.; Bajazitov, R.A.; Galeyev, M.M.; Ismagilow, Z.B.

    1996-12-31

    The opportunities of spatial-resolvable atmosphere monitoring and atmospheric pollutions remote chemical analysis based on the CW-laser radiants are investigated. A frequency-responsive processing peculiarities of atmosphere remote sensing signals are described. Application of the mentioned approach for the limited hydrocarbons remote detection and sensing is discussed. The requirements to the CW-LIDAR receiving and radiating systems parameters are formulated. The evaluations of the system sensitivity limit, measurement accuracy and accuracy increase ways are presented.

  19. CW operation of an intracavity pumped molecular submillimeter-wave laser

    NASA Technical Reports Server (NTRS)

    Koepf, G. A.

    1977-01-01

    The 373-micron line of CH3CN was operated in a CW mode in an arrangement where the submillimeter (SMM)-wave laser is placed inside the resonator of the CO2 pump laser. 1 mW of CW output power was obtained; this is five times the power of a comparable SMM-wave laser in the common extracavity arrangement. In a pulsed mode, a peak power of 46 mW was measured.

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

    NASA Astrophysics Data System (ADS)

    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.

  1. Experimental study from linear to chaotic regimes on a terahertz-frequency gyrotron oscillator

    SciTech Connect

    Alberti, S.; Braunmueller, F.; Dubray, J.; Fasel, D.; Hogge, J.-Ph.; Silva, M. da; Tran, M. Q.; Tran, T. M.; Vuillemin, Q.; Ansermet, J.-Ph.; Cuanillon, P.; Avramides, K. A.; Macor, A.; Rijk, E. de

    2012-12-15

    Basic wave-particle interaction dynamics from linear to chaotic regimes is experimentally studied on a frequency tunable gyrotron generating THz radiation in continuous mode (200 W) at 263 GHz which will be used for dynamic nuclear polarization nuclear magnetic resonance spectroscopy applications. In the studied system, the nonlinear dynamics associated to the wave-particle interaction is dominated by longitudinal mode competition of a given transverse TE{sub m,p} cavity-mode. This study covers a wide range of control parameter from gyro-traveling wave tube (gyro-TWT) to gyro-backward wave oscillator (gyro-BWO) like interactions for which extensive theoretical studies have been performed in the past on a simplified system. Besides the common route to chaos characterized by period doubling, other routes have been identified among which some are characterized by line-width frequency-broadening on the side-bands. The complex nonlinear dynamics is in good agreement with the theory and the experimental results are discussed on the basis of the prediction obtained with the nonlinear time-dependent self-consistent codes TWANG and EURIDICE both based on a slow-time scale formulation of the self-consistent equations governing the wave-particle dynamics.

  2. Absolute instabilities in a high-order-mode gyrotron traveling-wave amplifier.

    PubMed

    Tsai, W C; Chang, T H; Chen, N C; Chu, K R; Song, H H; Luhmann, N C

    2004-11-01

    The absolute instability is a subject of considerable physics interest as well as a major source of self-oscillations in the gyrotron traveling-wave amplifier (gyro-TWT). We present a theoretical study of the absolute instabilities in a TE01 mode, fundamental cyclotron harmonic gyro-TWT with distributed wall losses. In this high-order-mode circuit, absolute instabilities arise in a variety of ways, including overdrive of the operating mode, fundamental cyclotron harmonic interactions with lower-order modes, and second cyclotron harmonic interaction with a higher-order mode. The distributed losses, on the other hand, provide an effective means for their stabilization. The combined configuration thus allows a rich display of absolute instability behavior together with the demonstration of its control. We begin with a study of the field profiles of absolute instabilities, which exhibit a range of characteristics depending in large measure upon the sign and magnitude of the synchronous value of the propagation constant. These profiles in turn explain the sensitivity of oscillation thresholds to the beam and circuit parameters. A general recipe for oscillation stabilization has resulted from these studies and its significance to the current TE01 -mode, 94-GHz gyro-TWT experiment at UC Davis is discussed. PMID:15600760

  3. Stable harmonic multiplying gyrotron traveling-wave amplifier with distributed wall losses and attenuating severs

    SciTech Connect

    Yeh, Y. S.; Cheng, J. H.; Chen, L. K.; Hung, C. W.; Lo, C. Y.; Liao, C. W.

    2008-02-15

    Harmonic multiplying gyrotron traveling-wave amplifiers (gyro-TWTs) provide magnetic field reduction and frequency multiplication. However, spurious oscillations may reduce the amplification of the gyro-TWT. Most distributed-loss structures are stabilized in gyro-TWTs that operate at low beam currents. Attenuating severs are added to the interaction circuit of a distributed-loss gyro-TWT to prevent high beam currents that result in mode competition. This study proposes a Ka-band harmonic multiplying gyro-TWT, using distributed wall losses and attenuating severs, to improve the stability of the amplification and the performance of the amplifier. Simulation results reveal that the absolute instabilities are effectively suppressed by wall losses of the lossy and severed sections, especially in the low-k{sub z} and high-order modes. Meanwhile, the severed section, dividing an interaction circuit into several short sections, reduces the effective interaction lengths of the absolute instabilities. The stable harmonic multiplying gyro-TWT is predicted to yield a peak output power of 230 kW at 33.65 GHz with an efficiency of 30%, a saturated gain of 40 dB, and a 3 dB bandwidth of 0.8 GHz for a 60 kV, 13 A electron beam with an axial velocity spread of {delta}v{sub z}/v{sub z}=8%. The power/gain scaling and phase relation between the drive and the output waves are elucidated.

  4. Design of 95 GHz gyrotron based on continuous operation copper solenoid with water cooling.

    PubMed

    Borodin, Dmitri; Ben-Moshe, Roey; Einat, Moshe

    2014-07-01

    The design work for 2nd harmonic 95 GHz, 50 kW gyrotron based on continuous operation copper solenoid is presented. Thermionic magnetron injection gun specifications were calculated according to the linear trade off equation, and simulated with CST program. Numerical code is used for cavity design using the non-uniform string equation as well as particle motion in the "cold" cavity field. The mode TE02 with low Ohmic losses in the cavity walls was chosen as the operating mode. The Solenoid is designed to induce magnetic field of 1.8 T over a length of 40 mm in the interaction region with homogeneity of ±0.34%. The solenoid has six concentric cylindrical segments (and two correction segments) of copper foil windings separated by water channels for cooling. The predicted temperature in continuous operation is below 93 °C. The parameters of the design together with simulation results of the electromagnetic cavity field, magnetic field, electron trajectories, and thermal analyses are presented. PMID:25085157

  5. Design of 95 GHz gyrotron based on continuous operation copper solenoid with water cooling

    NASA Astrophysics Data System (ADS)

    Borodin, Dmitri; Ben-Moshe, Roey; Einat, Moshe

    2014-07-01

    The design work for 2nd harmonic 95 GHz, 50 kW gyrotron based on continuous operation copper solenoid is presented. Thermionic magnetron injection gun specifications were calculated according to the linear trade off equation, and simulated with CST program. Numerical code is used for cavity design using the non-uniform string equation as well as particle motion in the "cold" cavity field. The mode TE02 with low Ohmic losses in the cavity walls was chosen as the operating mode. The Solenoid is designed to induce magnetic field of 1.8 T over a length of 40 mm in the interaction region with homogeneity of ±0.34%. The solenoid has six concentric cylindrical segments (and two correction segments) of copper foil windings separated by water channels for cooling. The predicted temperature in continuous operation is below 93 °C. The parameters of the design together with simulation results of the electromagnetic cavity field, magnetic field, electron trajectories, and thermal analyses are presented.

  6. Design of 95 GHz gyrotron based on continuous operation copper solenoid with water cooling

    SciTech Connect

    Borodin, Dmitri; Ben-Moshe, Roey; Einat, Moshe

    2014-07-15

    The design work for 2nd harmonic 95 GHz, 50 kW gyrotron based on continuous operation copper solenoid is presented. Thermionic magnetron injection gun specifications were calculated according to the linear trade off equation, and simulated with CST program. Numerical code is used for cavity design using the non-uniform string equation as well as particle motion in the “cold” cavity field. The mode TE02 with low Ohmic losses in the cavity walls was chosen as the operating mode. The Solenoid is designed to induce magnetic field of 1.8 T over a length of 40 mm in the interaction region with homogeneity of ±0.34%. The solenoid has six concentric cylindrical segments (and two correction segments) of copper foil windings separated by water channels for cooling. The predicted temperature in continuous operation is below 93 °C. The parameters of the design together with simulation results of the electromagnetic cavity field, magnetic field, electron trajectories, and thermal analyses are presented.

  7. Study of a Ka-Band TE11 Mode Gyrotron Traveling-Wave Amplifier

    NASA Astrophysics Data System (ADS)

    Xu, Shou-Xi; Du, Chao-Hai; Liu, Pu-Kun

    2010-05-01

    A Ka-band gyrotron traveling wave (gyro-TWT) amplifier with high power and wide bandwidth operated in the fundamental TE11 circular mode is presented in detail. The stability of the gyro-TWT amplifier using linear and nonlinear theory is analyzed. The distributed loss technique is employed in the interaction circuit which guarantees the amplifier zero-drive stability. The effects of the parameters such as input power, driver frequency, magnetic field on the performance of the gyro-TWT is discussed. The simulation results show that the gain and the bandwidth of the designed Ka-band gyro-TWT are about 60.0 dB and 1.4 GHz at constant drive with an axial velocity spread {{Δ {v_z}} {{v_z}}} = 5% . The peak output power and the corresponding electronic efficiency are about 111 kW and 26.4% respectively for a 70 kV, 6A electron beam at 35 GHz. In addition, the design of the input coupler, a triode-type magnetron injection gun (MIG) and a triple output window are given.

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

    SciTech Connect

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

    2015-11-15

    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.

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

    SciTech Connect

    Yeh, Y. S.; Chen, Chang-Hong; Wang, Z. W.; Kao, B. H.; Chen, Chien-Hsiang; Lin, T. Y.; Guo, Y. W.

    2014-12-15

    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 TE{sub 01} drive wave, the second harmonic component of the beam current initiates a TE{sub 02} 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 (TE{sub 21}, TE{sub 51}, TE{sub 22}, and TE{sub 03}). 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.

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

    SciTech Connect

    Yeh, Y. S.; Guo, Y. W.; Kao, B. H.; Chen, C. H.; Wang, Z. W.; Hung, C. L.; Chang, T. H.

    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.

  11. Design of Beam Tunnel for 42 GHz, 200 kW Gyrotron

    NASA Astrophysics Data System (ADS)

    Kumar, Nitin; Alaria, Mukesh K.; Singh, Udaybir; Bera, A.; Singh, T. P.; Sinha, A. K.

    2010-05-01

    A beam tunnel for a 42 GHz, 200 kW gyrotron for an Indian TOKAMAK system has been designed. The initial design of the beam tunnel has been carried out on the basis of the required electron beam parameters at the interaction cavity and the electron beam simulation of the magnetron injection gun. The design optimization of the beam tunnel has been done with the help of 3-D simulation software CST-Microwave Studio. In the simulation, the absorption, the reflection and the transmission of RF power by the beam tunnel have been analyzed. Three different lossy ceramics, Al2O3-SiC, AlN-SiC and BeO-SiC have been investigated during the simulation. The simulation results obtained with CST-Microwave Studio have been validated with another 3-D simulation software HFSS. The Q value of the beam tunnel for different ceramic material has also been analyzed to investigate the parasitic mode excitation in the beam tunnel.

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

    SciTech Connect

    Yeh, Y. S.; Chen, C. H.; Yang, S. J.; Lai, C. H.; Lin, T. Y.; Lo, Y. C.; Hong, J. W.; Hung, C. L.; Chang, T. H.

    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%.

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

    NASA Astrophysics Data System (ADS)

    Yeh, Y. S.; Hung, C. L.; Chang, T. H.; Guo, Y. W.; Kao, B. H.; Chen, C. H.; Wang, Z. W.

    2015-12-01

    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.

  14. Harmonic mode competition in a terahertz gyrotron backward-wave oscillator

    SciTech Connect

    Kao, S. H.; Chiu, C. C.; Chang, P. C.; Wu, K. L.; Chu, K. R.

    2012-10-15

    Electron cyclotron maser interactions at terahertz (THz) frequencies require a high-order-mode structure to reduce the wall loss to a tolerable level. To generate THz radiation, it is also essential to employ cyclotron harmonic resonances to reduce the required magnetic field strength to a value within the capability of the superconducting magnets. However, much weaker harmonic interactions in a high-order-mode structure lead to serious mode competition problems. The current paper addresses harmonic mode competition in the gyrotron backward wave oscillator (gyro-BWO). We begin with a comparative study of the mode formation and oscillation thresholds in the gyro-BWO and gyromonotron. Differences in linear features result in far fewer 'windows' for harmonic operation of the gyro-BWO. Nonlinear consequences of these differences are examined in particle simulations of the multimode competition processes in the gyro-BWO, which shed light on the competition criteria between modes of different as well as the same cyclotron harmonic numbers. The viability of a harmonic gyro-BWO is assessed on the basis of the results obtained.

  15. Rise and fall time behavior of the gyrotron backward-wave oscillator.

    PubMed

    Pao, K F; Chang, T H; Chen, S H; Chu, K R

    2006-10-01

    The rise and fall time behavior of a pulsed microwave oscillator is a problem of academic interest. It is also of importance to radar and other applications because it can lead to phase and frequency jitters or even lock the entire pulse into an undesired mode. Here we present a study of the rise and fall time behavior in the gyrotron backward-wave oscillator (gyro-BWO). Single-mode simulations reveal that, during the rise and fall portions of the electron beam pulse, oscillation frequencies of the axial modes vary in such a way that their transit angles remain at the respective optimum values. Thus, axial mode competition and mode switching can readily take place in these transient stages. Time-dependent simulations demonstrate that, under both the gradual and instant turn-on conditions, the axial modes compete in a pattern governed by the characteristic asymmetry of the mode profiles. Other aspects of physics interest include the analysis and explanation of a resultant hysteresis effect between the rise and fall portions of the beam pulse. These understandings are expected to provide the basis for achieving a stable gyro-BWO operating at a single mode throughout the entire beam pulse. PMID:17155180

  16. Numerical analysis of an injection-locked gyrotron backward-wave oscillator with tapered sections.

    PubMed

    Grudiev, A; Schünemann, K

    2003-07-01

    Injection-locked operation of a gyrotron backward-wave oscillator (gyro-BWO) is investigated by means of our time-dependent self-consistent code. Numerical results for a 100 kW, Ka-band, TE11-mode gyro-BWO developed at NTHU, Hsinchu, Taiwan, are compared to the experimental ones. The results are in good agreement showing, in both cases, the asymmetric form of the locking bandwidth curve. Comparison of these results obtained for the case of injection of the external signal into the upstream port, as has been done in the experiments, to the results for injection into the downstream port is made. The results of the comparison demonstrate that the asymmetry of the locking bandwidth curves must be attributed to the influence of the injection signal on the electron bunching that takes place in the input tapered section. Moreover, in some cases, this influence results also in a significant increase of the locking bandwidth (up to a factor of 5). An increase of the output power of the locked gyro-BWO over the output power of the free running one is also investigated and compared with the experimental data. PMID:12935262

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

    NASA Astrophysics Data System (ADS)

    Yeh, Y. S.; Hung, C. L.; Chang, T. H.; Chen, C. H.; Yang, S. J.; Lai, C. H.; Lin, T. Y.; Lo, Y. C.; Hong, J. W.

    2012-09-01

    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 TE11 drive wave, the second harmonic component of the beam current initiates a TE21 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%.

  18. On the sensitivity of terahertz gyrotron based systems for remote detection of concealed radioactive materials

    NASA Astrophysics Data System (ADS)

    Nusinovich, G. S.; Sprangle, P.; Semenov, V. E.; Dorozhkina, D. S.; Glyavin, M. Yu

    2012-06-01

    This paper analyzes some features of systems intended to remotely detect concealed radioactive materials by using a focused THz radiation. This concept is based on possibility to focus high-power THz radiation in a small spot where the wave field exceeds the breakdown threshold. However, in the absence of any sources of ionization, the probability to have in this breakdown-prone volume any seed electrons is very low. Thus, high breakdown rate in a series of THz pulses will indicate the presence of concealed radioactive materials in the vicinity of a focused wave beam. The goal of the present paper is to determine by using the statistical theory THz pulse duration required for reliable initiation of the discharge. Then, the detectable mass of the radioactive material is determined as the function of distance and of the THz wave power and pulse duration. Lastly, possible benefits from using pulse compressors, which shorten the pulse duration but increase the wave power and, hence, the breakdown-prone volume, are analyzed. It is shown that the use of pulse compressors can significantly improve the sensitivity of THz gyrotron based systems for remote detection of concealed radioactive materials.

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

    NASA Astrophysics Data System (ADS)

    Yeh, Y. S.; Chen, Chang-Hong; Wang, Z. W.; Kao, B. H.; Chen, Chien-Hsiang; Lin, T. Y.; Guo, Y. W.

    2014-12-01

    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 ( TE 21 , TE 51 , TE 22 , and TE 03 ). 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. High current proton source based on ECR discharge sustained by 37.5 GHz gyrotron radiation

    NASA Astrophysics Data System (ADS)

    Skalyga, V.; Izotov, I.; Sidorov, A.; Razin, S.; Zorin, V.; Tarvainen, O.; Koivisto, H.; Kalvas, T.

    2012-10-01

    Formation of hydrogen ion beams with high intensity and low transverse emittance is one of the key challenges in accelerator technology. Present work is devoted to experimental investigation of proton beam production from dense plasma (Ne > 1013 cm-3) of an ECR discharge sustained by 37.5 GHz, 100 kW gyrotron radiation at SMIS 37 facility at IAP RAS. The anticipated advantages of the SMIS 37 gasdynamic ion source over the current state-of-the-art proton source technology based on 2.45 GHz hydrogen discharges are described. Experimental result obtained with different extraction configurations i.e. single- and multi-aperture systems are presented. It was demonstrated that ultra bright proton beam with approximately 4.5 mA current and 0.03 π·mm·mrad normalized emittance can be produced with the single-aperture (1 mm in diameter) extraction, the corresponding brightness being 5 A/(π·mm·mrad)2. For production of high current beams a multi-aperture extractor was used resulting to a record of 200 mA / 1.1 π·mm·mrad normalized emittance proton beam. The species fraction i.e. the ratio of H+ to H2+ current was recorded to be > 90 % for all extraction systems. A possibility of further enhancement of the beam parameters by improvements of the extraction system and its power supply is discussed.