Toshiaki Tatsukawa

Development of a second cyclotron harmonic gyrotron operating at submillimeter wavelengths

The development of a high‐frequency, step‐tunable gyrotron operating at submillimeter wavelengths is described. The gyrotron design was optimized for operation at the second harmonic of the electron cyclotron frequency in the TE261 cavity mode, whose resonant frequency is 384 GHz. Experimental results show that second harmonic operation can occur without mode competition as long as the beam current is low (Ib ≲0.8 A), but as the current is increased, the fundamental TE231 cavity mode increases and eventually (Ib ≳1 A) suppresses the second harmonic. The competition between the two modes is studied in detail. The starting current for second harmonic operation is also studied experimentally and compared with calculated results. Other resonances have also been examined. With the present superconducting magnet, the maximum frequency achieved is 402 GHz (second harmonic operation in the TE551 cavity mode) at several kilowatts.

ESR spectrometer with a wide frequency range using a gyrotron as a radiation power source

The development of a high frequency electron spin resonance (ESR) spectrometer with a wide frequency range using a gyrotron as the radiation power source is described.GYROTRON FU-E, optimized for use in an ESR spectrometer in the millimeter wave range, was developed in Fukui University. In order to test the normal operation of the spectrometer, the ESR of two standard samples, single crystal and polycrystalline DPPH, has been measured, in the pulsed mode over the frequency range from 65 GHz to 135 GHz.

Development of a second cyclotron harmonic gyrotron operating at 0.8 mm wavelength

This letter describes the development of a submillimeter wave gyrotron operating at the second harmonic of the cyclotron frequency. The observed frequency is 383 GHz, which corresponds to the wavelength of 0.79 mm, and the output power is about 1 kW. We believe that the frequency is a world record for a stable, long pulse gyrotron operation at the second cyclotron harmonic, without a competition with the operation at the fundamental. Comparisons with the simulation results are represented.

Development of a medium power, submillimeter wave gyrotron using a 17 T superconducting magnet

GYROTRON FU IV, a frequency tunable gyrotron for spectroscopy in the submillimeter wavelength range using a 17 T superconducting magnet, has been designed and constructed. Simulations predict that the gyrotron will emit radiation at high frequencies up to 394 GHz (TE041 cavity mode) at the fundamental of the electron cyclotron frequency, up to 858 GHz (TE091 mode) at the second harmonic and up to 1301 GHz (TE8 11 1 mode) at the third harmonic. Preliminary experimental results have demonstrated operation from 158 to 443 GHz at the fundamental and from 336 to 838 GHz at the second harmonic. Output powers are several hundred watts and efficiencies several percent.

Competition between fundamental and second‐harmonic operations in a submillimeter wave gyrotron

Competition between electron cyclotron fundamental (f=fc) and second‐harmonic (f=2fc) operation in a submillimeter wave gyrotron is described. Even when the magnetic field intensity is adjusted to the optimum value for second‐harmonic operation, we can get a pure mode only for small beam currents. As the beam current is increased, excitation of the fundamental appears and eventually suppresses the second harmonic. The observed competition between the fundamental and second harmonic is compared with a computer simulation.

Development of a high‐frequency, second‐harmonic gyrotron tunable up to 636 GHz

In this Letter, a high‐frequency, second‐harmonic gyrotron using a 12 T superconducting magnet is described. It has achieved a maximum frequency of 636 GHz (corresponding to a wavelength of 472 μm). Operating at both the fundamental and the second harmonic of the electron cyclotron frequency enables the gyrotron to act as a high power (several 100 W), step tunable, millimeter to submillimeter wave source in the wide frequency range from 150 to 630 GHz.

Development of Submillimeter Wave Catheter Transmitting a Gyrotron Output for Irradiation on Living Bodies

The development of a millimeter and submillimeter wave catheter for irradiation on living bodies using a gyrotron as the radiation power source is described. The GYROTRON FU-IV, optimized for such applications was used in the development. It was operated in both CW and pulsed regime at TE03 and TE32 modes with frequencies 302 GHz and 238 GHz respectively. Irradiation tests were made on thermal papers, beefs and liver of living rats.

Study of Electron Beam Misalignment in a Submillimeter Wave Gyrotron

Electron beam misalignment in a submillimeter-wave gyrotron strongly affects its total efficiency as well as excitation of rotating and counterrotating modes. Some of misalignment phenomena were studied theoretically and experimentally.

Development of high frequency, cyclotron harmonic gyrotron oscillator

Abstract The oscillation results of a high frequency gyrotron which operates at the fundamental cyctron frequency and its higher harmonics ( s =1, 2, 3) are described. The fairly high frequency of 220 GHz (corresponding wave length 1.35 mm) has been achieved at the fundamental and second harmonic of the cyclotron frequency. The scaling law of output power to harmonic number s is also described.

High Frequency and High Mode Purity Operations of Gyrotron FU IVA

The cavity of the newest gyrotron, Gyrotron FU IVA in the high frequency series of Fukui University gyrotrons (the Gyrotron FU series) is designed to minimize the mode conversion from the main cavity mode to the higher modes. In this paper, the experimental results are compared with simulations for the complete gyrotron oscillator. The gyrotron has an additional advantage to cover the wide frequency range in submillimeter wave region.