Submillimeter Wave ESR Measurement for Cr3+ in Ruby Crystal Using a Gyrotron as a Radiation Source

Fine structure constant of ruby has been measured using an ESR spectrometer with a pulse magnetic for high fields and a gyrotron as a radiation source in a millimeter to submillimeter wave range. The measurement was carried out at room temperature. The Zeeman energy in this frequency range is large enough compared with the fine structure constant. The higher order term in the effective spin Hamiltonian can explain the dependence of fine structure constant on the frequency. The observed fine structure constants depend on the field intensity.     

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

High frequency, medium power gyrotrons (Gyrotron FU series) have been developed at Fukui University as radiation sources covering a broad band from millimeter to submillimeter wave region. They have already been applied to high frequency electron spin resonance and to submillimeter wave scattering in plasma. Many parameters of the gyrotron series could be useful for applications in several new areas. The development and some applications of the Gyrotron FU series are summarized in this paper     

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.     

Fabrication of Liquid Helium-Free Superconducting Magnet for Millimeter Wave Gyrotron

A liquid helium free superconducting magnet was designed and fabricated and for an application to a millimeter wave gyrotron and a peniotron. The magnet generates a magnetic field of 5T in a 100mm room temperature bore and has been continuously working for more than 5,400 hours without troubles.The magnet system was applied to the millimeter wave gyrotron experiments to confirm the stability of the magnet. In the experiments, stable operations of the gyrotron were achieved in the frequency range of 30 - 133GHz.     

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.     

磁压对级联爆磁压缩脉冲发生器性能的影响

为了研究负载为mH量级的间接馈电两级级联柱-锥构型的爆磁压缩产生器的基本物理过程和能量转换机理，利用描述爆磁压缩物理过程的2维爆轰磁流体力学程序MFCG(Ⅴ)，以实验模型结构参数为基础模拟计算了一系列模型，分析了磁压对金属套筒径向膨胀速度及膨胀过程的影响。计算结果表明:套筒的径向膨胀速度取决于爆轰压与磁压的共同作用，在爆磁压缩过程的绝大部分时间里，向外膨胀的爆轰压都远大于向内压缩的磁压，因而套筒的径向膨胀速度主要是由爆轰压决定;但是在功率放大级的后半段，也就是发生器电流增长最快阶段，磁压也迅速增长，它的增长大大降低了套筒的径向膨胀速度；在功率放大级的后期，磁压已经超过爆轰压，它对系统设计的影响已经不能完全忽略。     

THE FIRST EXPERIMENT OF A THz GYROTRON WITH A PULSE MAGNET

A THz gyrotron with a pulse magnet has been designed, constructed and operated in FIR FU. It is developed as one of high frequency gyrotrons included in Gyrotron FU Series. The gyrotron has already achieved the first experimental result for high frequency operations whose radiation frequency exceeds 1 THz. In this paper, the design detail and the operation test results for sub-terahertz to terahertz range are described. The second harmonic operation is confirmed experimentally at the expected frequency of 1.005 THz due to TE_6,11 cavity mode at the magnetic field intensity of 19.0 T.     

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

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.     

低磁场过模慢波结构型高功率毫米波发生器的改进

 利用粒子模拟的方法设计了一个高功率毫米波发生器,并对其进行了实验研究及改进。采用过模慢波结构以增大束波作用空间,从而提高功率容量;为实现过模慢波器件的单模、单频工作,选择TM01模的π模作为工作模式。采用过模慢波结构,结合合理的器件结构设计,可降低器件工作所需的导引磁场。实验在TORCH-01加速器平台进行,产生的微波频率由色散线法测量,其功率由远场积分法得到。最初的器件采用矩形波纹慢波结构,得到频率为33.56 GHz、功率约110 MW的微波输出,但功率难以进一步提高,脉宽仅为7~8 ns,且在慢波结构边沿发现击穿痕迹。对矩形慢波结构进行倒圆角处理后,借助数值模拟,发现其TM01模的π模频率变化不大。改进后的器件在0.8 T导引磁场下,当电压和电流分别为590 kV与5.2 kA时,实验得到频率33.56 GHz、功率320 MW的毫米波输出,微波模式为准TM01模,效率约10%,脉宽延长至约13 ns,器件内表面无明显击穿痕迹。     

Application of the Gyrotron FU II Submillimeter Wave Radiation Source to Plasma Scattering Measurements

Gyrotron FU II has been successfully applied as a submillimeter wave radiation source to plasma scattering measurements on the Compact Helical System (CHS) in National Institute for Fusion Science (NIFS) in Japan. The gyrotron operates in a long pulse mode (the pulse width is about 600 ms) at a frequency of about 350 GHz (the corresponding wavelength is 0.85 mm). The output power is about 110 W. The output power is transmitted along a circular waveguide system and converted to a Gaussian-like beam by a quasi-optical antenna. After that, the beam is directed onto the CHS plasma and the scattered signal is detected by a homodyne detection system. The frequency and the wave number of the scattered signal are analyzed. The results suggest that a broad band low frequency (several tens to several hundreds kHz) density fluctuation is excited in the CHS plasma only during neutral beam injection (NBI) or ion cyclotron resonance (ICR) heating.     

Millimeter and Submillimeter Wave ESR System: Using 30 T Pulsed Magnetic Field

New systems for millimeter and submillimeter wave ESR have been developed in Kobe University. In the previous system the pulsed magnetic field was limited up to 17 T in the temperature range from 1.8 to 86 K. Using the new systems, we can measure in the field range up to 30 T in the temperature range from 1.8 K to 4.2 K and from 18 K to room temperature. The resolution of the magnetic field has been also improved in the new ESR system. The details of our new ESR systems are presented. In addition, the measurements of Yb₂Cu₂O₅ using these new systems are presented.     

A submillimeter gyrotron with a pulsed magnetic field

Pulse solenoids seem promising for sumbillimeter wave generation in gyrotrons. In this paper a single-pulse submillimeter gyrotron with a pulsed magnetic field is described. At the wavelength 0.8 mm the output power 120 KW with the efficiency 15% has been obtained.     

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.     

1.8 T直流磁体94 GHz连续波二次谐波回旋管

首次实现直流磁体W波段二次谐波回旋管连续波稳定运行。回旋管工作时所需1.8 T磁场由一个水冷直流线圈产生。直流线圈励磁电流为500 A,功耗28 kW,内孔直径66 mm,可直接将回旋管插入内孔中。回旋管内电子束由双阳极磁控注入电子枪产生。采用高效率内置准光模式变换器实现束波分离并输出准高斯波束。研制的回旋管工作频率为94.08 GHz,腔内工作模式为TE₀₂。实验中成功实现5 min连续稳定运行,输出功率达到12 kW。电子束电压为45 kV,电流1.7 A,对应的输出效率15.7 %。     

Long Pulse Operation of the THz Gyrotron with a Pulse Magnet

Long pulse operation up to 1 msec of a high frequency gyrotron with a pulse magnet has been successfully carried out in a frequency range including 1 THz. In the experiments, the timing of an electron beam pulse injection is adjusted at the top of the magnetic field pulse, where the variation of field intensity is negligible. The operation cavity modes seem to be TE_{1, 12} and TE_4,12 at the second harmonics. The corresponding frequencies are 903 GHz and 1,013 GHz, respectively. Additionally several features of radiation measurement results of the gyrotron are described and brief considerations are presented.     

W波段二次谐波回旋行波管放大器的模拟与设计

回旋行波管放大器是一种具有高功率、高频率、宽带宽的毫米波放大器，TE₀₂模二次谐波回旋行波管放大器在保持基波回旋行波管放大器的基础上极大地减小了工作磁场,从而具有广阔的应用前景. 利用两段分布式损耗的互作用结构，有效抑制了绝对不稳定性和回旋返波振荡,避免了模式互作用电路引起的模式畸变，提高了输出功率，在一定程度上克服了谐波互作用较弱的缺点，满足了扩展功率容量和放大器长时间稳定工作的要求. 非线性模拟结果和粒子模型(particle in cell)模拟结果均表明，在工作电压为100k 关键词： W波段 二次谐波 回旋行波管放大器     

94 GHz回旋管准光模式变换器设计

基于几何光学理论和矢量绕射理论,研究了将回旋管及其他高功率微波器件的振荡输出模式转换成准光高斯波束的模式变换器,采用伏拉索夫(Vlasov)辐射器和三级准光反射面实现了准高斯模TEM₀₀的横向输出.研究了Vlasov辐射器的工作机理,运用矢量绕射理论计算出波导辐射场,口面电流分布的方法计算反射面辐射场.通过编写程序设计了将94 GHz,模式为TE₆₂的毫米波转化为准光高斯波束的内置式准光模式变换器. 关键词： 94 GHz回旋管 内置式准光模式变换器 Vlasov辐射器 矢量绕射理论     

CW Operation of a Submillimeter Wave Gyrotron (Gyrotron Fu IV) for High Stability of the Output Frequency

The first cw operation of our submillimeter wave gyrotron (Gyrotron FU IV) using a 12 T superconducting magnet has been successfully carried out. Output power is more than 20 W at a frequency of 301 GHz in the TE₀₃₁ resonant cavity mode. Time-resolved frequency measurement s shows that the frequency fluctuation of the gyrotron output is smaller than 2 MHz. This frequency fluctuation is mainly due to the fluctuation in the output voltage of the power supply.     

A Continuously Tunable Ka-Band Gyrotron

An experimental study was carried out to test the concept of using a gyrotron with a tapered circuit in a uniform magnetic field as a high-power tunable source of millimeter-wave radiation. It was demonstrated that the device can be used as either an oscillator or an amplifier with the operating frequency tunable by varying the magnetic field. In the oscillator mode, the tube produced a peak output power of 500-750 W with the frequency continuously tunable from 30 to 39 GHz. As an amplifier mode, the tube demonstrated an electronic gain of ~23 dB at a magnetically tunable center frequency with an instantaneous bandwidth of ~5 percent. The stability characteristics of the amplifier were also investigated.     

TE_(02)模式95 GHz三次谐波回旋管实验

首次实现W波段三次谐波回旋管输出功率突破10kW。谐波回旋管互作用结构采用带有光阑结构的圆柱型开放式谐振腔,工作模式为低损耗圆对称模式TE02。实验中,在脉冲宽度20μs、电子束电压45kV、电流3A、磁场1.23T时,测得工作频率为95.22GHz,输出功率13.4kW,对应效率9.9%。