Development of frequency tunable, medium power gyrotrons (Gyrotron FU series) as submillimeter wave radiation sources

Idehara, T.; Ogawa, I.; Mitsudo, S.; Pereyaslavets, M.; Nishida, Nobuo; Yoshida, Kazufumi

doi:10.1109/27.772260

Cited by 116 publications

(48 citation statements)

References 18 publications

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“…While this gyrotron is constructed in a manner that is very similar to other demountable tube gyrotrons used in academic research [100][101][102], our desire to make it compact and compatible with operation in close proximity to an NMR spectrometer necessitated special design considerations.…”

Section: General Backgroundmentioning

confidence: 99%

“…The gyrotron control system continuously monitors the microwave output power and adjusts the cathode heater to counteract any variations. No effort has been made to regulate the frequency, though we note that this has previously been attempted in other gyrotrons designed for academic research [100].…”

Section: Appendix 1 Gyrotron Control System --Functional Specificationmentioning

confidence: 99%

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

Bajaj

Hornstein

Kreischer

et al. 2007

Journal of Magnetic Resonance

162

130

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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 temperaturedependent 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 12 mA) at frequencies between 320-365 GHz, suggesting an efficient route for the generation of even higher frequency radiation. The low starting currents were attributed to an elevated cavity Q, which is confirmed by cavity thermal load measurements. We conclude with an appendix containing a detailed description of the control system that safely automates all aspects of the gyrotron operation.

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Section: General Backgroundmentioning

confidence: 99%

Section: Appendix 1 Gyrotron Control System --Functional Specificationmentioning

confidence: 99%

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

Bajaj

Hornstein

Kreischer

et al. 2007

Journal of Magnetic Resonance

162

130

View full text Add to dashboard Cite

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“…[10], and experimentally studied in Ref. [8]. Below we show how to estimate the required modulation in the mod-anode voltage for frequency-doubling gyroklystrons (GKLs).…”

Section: B Ohmic Lossesmentioning

confidence: 99%

“…These were done at Fukui University, Japan. A review of this work was published recently [8]. Experiments with a 250 GHz gyrotron oscillator for Electron Paramagnetic Resonance (EPR) spectroscopy is going on at MIT [9].…”

Section: Introductionmentioning

confidence: 99%

A submillimeter-wave gyroklystron: theory and design

Nusinovich

Walter²,

Kremer³

et al. 2000

IEEE Trans. Plasma Sci.

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New elements of the theory and a preliminary design for a pulse/CW 360 GHz gyroklystron are presented. Issues germane to very high frequency operation of gyroklystron amplifiers, including drive power and limits on cavity Q, are discussed. A specific two cavity design is described. That device had a gain of 33 dB and a beam extraction power of 1 kW with an electronic efficiency of 8% and a power output of 700 W after taking into account Ohmic losses . To produce fast rising pulses, the beam velocity ratio was varied via the modulating anode of a magnetron injection gun. A design for an electron gun through which reduction of the output signal by -50 dB was achieved by a 400 V modulation is given. The input coupler, cavities, electron gun, collector, output coupling optics and collector are described. In addition, issues concerning the fabrication of the high precision, 2 mm diameter cavities are discussed.

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“…However, the Vlasov IMC is used in low power gyrotrons because it is very compact and easy to fabricate [4]. It is also used external to the gyrotron [5].…”

Section: Introductionmentioning

confidence: 99%

Calculation of Radiation from a Helically Cut Waveguide for a Gyrotron Mode Converter in the Quasi-Optical Approximation

Choi

Shapiro

Sirigiri

et al. 2008

J Infrared Milli Terahz Waves

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A gyrotron internal mode converter consists of a launcher that radiates the waveguide mode as a nearly Gaussian beam in free space, followed by a set of mirrors to focus and direct the radiation.We present a calculation of the radiation from the launcher based on a quasi-optical approach that includes diffraction. The results are in good agreement with a calculation using a numerical code based on the electric field integral equation approach. The results should be useful for designing so-called Vlasov internal mode converters and for understanding the role of diffraction in the design of internal mode converters for gyrotrons.

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Development of frequency tunable, medium power gyrotrons (Gyrotron FU series) as submillimeter wave radiation sources

Cited by 116 publications

References 18 publications

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

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

A submillimeter-wave gyroklystron: theory and design

Calculation of Radiation from a Helically Cut Waveguide for a Gyrotron Mode Converter in the Quasi-Optical Approximation

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