High Power, Frequency Tunable, Submillimeter Wave ESR Device Using a Gyrotron as a Radiation Source

ESR device using a submillimeter wave gyrotron as a radiation source and a pulse magnet for high field up to 30 T has been constructed. Our gyrotrons (Gyrotron FU series) were developed as millimeter and submillimeter wave radiation sources and have attractive advantages for ESR spectroscopy, for example, high power and frequency tunability over broad range. The ESR device has been successfully applied to three cases of ESR measurements. In the first case, the temperature dependence of ESR was measured for a typical antiferromagnetic material MnO at the frequency of 301 GHz. In the second case, the dependence of the fine structure constant of the ruby on the magnetic field intensity was measured in the millimeter to submillimeter wave region. In these two cases, the gyrotron was operated by complete cw mode. In the final case, a pulse technique was applied to the ESR, the gyrotron was operated in pulse mode and the pulsed magnetic field was generated in the synchronized phase with the gyrotron operation.     

连续调谐太赫兹回旋管非稳定振荡状态研究

太赫兹回旋管可实现高功率输出,并具有一定的频率调谐范围,是核磁共振波谱系统理想的高功率太赫兹辐射源。设计了263 GHz,TE_5,2基波连续调谐回旋管,通过磁场调节实现频率调谐范围为1.39 GHz,利用时域多模多频自洽非线性理论对设计的连续调谐回旋管非稳定振荡状态进行了研究。结果表明,在低次纵向谐波模式工作磁场范围内,当工作电流大于起振电流时,连续调谐回旋管先进入稳定状态,高次纵向谐波模式被抑制,工作模式TE_5,2的输出功率随时间不变;当电流增大,纵向谐波模式间的竞争引起回旋管由稳定状态进入到非稳定振荡状态,工作模式TE_5,2的输出功率随时间呈振荡变化且互作用效率大大降低;随着电流的进一步增大,回旋管又回到与低电流不同的稳定状态,互作用效率进一步降低。同时发现非稳定振荡状态的起始电流随着磁场增加而增大。本研究对需工作于稳定状态的面向DNP-NMR应用的连续调谐太赫兹回旋管的研制具有一定指导意义。     

宽温度范围微型人眼安全激光器

报道了一种宽温度适应范围的微型化人眼安全激光器。采用中心波长940 nm的二极管作为泵浦源,Er3+/Yb3+共掺磷酸盐玻璃作为增益介质,Co2+: MgAl2O4作为被动调Q晶体,研究了微型激光器的结构和激光在宽温度范围下的输出特性。当泵浦能量9 mJ,重复频率10 Hz,泵浦脉宽5 ms时,获得了单脉冲能量130 J,脉宽5.5 ns,峰值功率大于20 kW的激光输出,光束质量因子为1.3。采用真空封装工艺,在－40~50 ℃温度范围内,自然冷却方式下激光器稳定输出,功率不稳定性波动小于5%。     

Ruby ESR Over a Wide Frequency Range in the Millimeter Wave Region

The ESR of Cr³⁺ in dark ruby is measured using a high frequency ESR spectrometer with a wide frequency range which uses a gyrotron as the radiation source. For this purpose, GYROTRON FU- IV A developed at Fukui University was optimized for use in an ESR apparatus operating in the millimeter-wave range.The observed fine structure constant D for ruby is found to be D –5.728 GHz and the g-values g 1.981, g 1.982. Both the values of |D| and g are smaller than those obtained at lower frequencies by other work. Higher order terms of the spin hamiltonian are discussed in order to understand the ruby ESR results in this higher frequency range.     

复合腔回旋管高频结构

为了提高回旋管的工作效率,高频结构中的模式之间的竞争是急需解决的问题。从模式耦合理论出发系统地研究了回旋管中过渡渐变复合腔的高频场结构,同时考虑了TM型寄生模式对工作模式的影响。通过对耦合系数的分析,为了降低模式之间的耦合程度,采用曲线作为回旋管中高频结构的渐变段。用三维电磁仿真软件和自主开发的程序对高频结构进行计算。计算结果与传统的线性渐变段谐振腔相比,采用非线性类型的谐振腔具有更强的模式抑制能力,并且该类型腔体中能够激励起更强的场幅值。     

宽量程高时间分辨扫描变像管

为改善大偏转角度的偏转像质,设计了一种高时间分辨、大扫描长度的扫描变像管电子光学和行波偏转系统。对变像管后加速技术进行了实验研究,结合图像外增强技术,解决了大面积扫描图像的探测灵敏度问题,达到了同时扩展扫描变像管的时间量程和提高时间分辨力的目的,研制出了宽时间量程、高时间分辨力的扫描变像管。初步实验表明,在量程为5 ns时,时间分辨力达到5 ps,也就是时间分辨力与时间量程之比达到1/1 000。     

宽光谱平像场全息凹面光栅的优化研究

基于凹面光栅的几何理论,推导了子午、弧矢聚焦曲线的数学表达式和全息平像场凹面光栅制作参数的计算关系式.提出了一种新的在整个使用波长范围内同时消除子午和弧矢像差的最佳优化设计方法.这种方法不同于以光线追迹技术为基础的标准光学设计软件如CODEV或ZEMAX的优化设计方法,而是从数学表达式出发,采用光栅优化因子,对凹面光栅的子午聚焦曲线和弧矢聚焦曲线进行拟合,从理论上找到最佳的能够使子午和弧矢像差同时趋于零的像平面,然后再根据拟合参数设计制作光栅.用Matlab软件解决了子午聚焦曲线超越方程无法解的困难;讨论了不同光栅常数和入射角度时对两聚焦曲线拟合程度的影响.提出了在宽光谱使用条件下,可以通过减小入射角度和光栅刻线数来提高光谱像质.     

宽量程高时间分辨扫描变像管

 为改善大偏转角度的偏转像质,设计了一种高时间分辨、大扫描长度的扫描变像管电子光学和行波偏转系统。对变像管后加速技术进行了实验研究,结合图像外增强技术,解决了大面积扫描图像的探测灵敏度问题,达到了同时扩展扫描变像管的时间量程和提高时间分辨力的目的,研制出了宽时间量程、高时间分辨力的扫描变像管。初步实验表明,在量程为5 ns时,时间分辨力达到5 ps,也就是时间分辨力与时间量程之比达到1/1 000。     

ESR spectrometer with a loop-gap resonator for cw and time resolved studies in a superconducting magnet

The design and performance of an electron spin resonance spectrometer operating at 3 and 9 GHz microwave frequencies combined with a 9-T superconducting magnet are described. The probehead contains a compact two-loop, one gap resonator, and is inside the variable temperature insert of the magnet enabling measurements in the 0-9T magnetic field and 1.5-400 K temperature range. The spectrometer allows studies on systems where resonance occurs at fields far above the g approximately 2 paramagnetic condition such as in antiferromagnets. The low quality factor of the resonator allows time resolved experiments such as, e.g., longitudinally detected ESR. We demonstrate the performance of the spectrometer on the NaNiO2 antiferromagnet, the MgB2 superconductor, and the RbC60 conducting alkaline fulleride polymer.     

水平变化浅海声波导中模态特征频率与声源距离被动估计

针对水平变化浅海声波导中声源宽容性被动测距问题,理论分析了海底地形水平缓变浅海波导中卷绕变换基础上的低频声场特征频率.推导了绝对硬海底时水平变化波导中声场模态时频到达结构以及模态瞬时相位的表达式,由该表达式给出了特征频率与收发距离的变化关系,进而提出了水平变化浅海波导中声源距离被动估计的修正方法,通过仿真和实验对理论与方法进行了验证.     

小型超宽谱高功率微波辐射系统

小型超宽谱高功率微波辐射系统由Tesla型100 kV级ns脉冲源、Peaking-Chopping型亚纳秒气体开关及TEM喇叭天线构成。系统重复运行频率100 Hz,辐射因子rEp值75 kV,主轴辐射场中心频率520 MHz,-3 dB频谱范围230~810 MHz。系统集成于一便携箱内,体积为80 cm50 cm26 cm,质量约45 kg。该系统结构紧凑,能够快速展开和撤收,可方便用于超宽谱高功率微波应用技术研究。     

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.     

波瓣波导谐振腔太赫兹回旋管的研究

以电子回旋脉塞非线性理论为基础, 结合三维电磁仿真软件, 通过导入高频场数值解替代理论解析的方法, 对波瓣波导谐振腔高次谐波太赫兹回旋管进行了理论和模拟研究. 给出了该类回旋管的起振电流、耦合系数以及注波互作用效率等重要参数, 并在此基础上设计了一只工作频率为0.4 THz, 工作模式TE₃₃模三次谐波波瓣波导谐振腔回旋管, 其电子注参数为1.0 A, 40.5 kV, 横纵速度比1.5,互作用区引导磁场为5.09 T, 输出功率达到3.3 kW.     

D-band frequency step-tuning of A 1 MW gyrotron using a brewster output window

In order to demonstrate the usability of gyrotron oscillators as frequency step tunable high power millimeter-wave sources, experiments on a 1 MW, 140 GHz TE_22,6 gyrotron with a built-in quasi-optical (q. o.) mode converter have been performed. By varying the operating parameters of the tube, a series of oscillations in the frequency range from 114 GHz to 166 GHz were excited. To avoid reflections, caused by the required vacuum barrier window, the gyrotron was equipped with a Brewster window. The achieved output power levels between 0.85 and 1.05 MW are compared to measurements carried out with the same tube using a conventional single-disk window. These experiments showed that even by using a q. o. mode converter, the influence of window reflections on the gyrotron oscillatory behavior cannot be removed completely.     

宽谱段大口径透射式摄影镜头设计

 设计了一种宽谱段大口径透射式摄影镜头,主要光学参数：焦距f′=200mm,口径D=160mm,视场角2ω=18°,光谱范围400μm～950μm。通过增加透镜个数,分裂厚透镜,选择具有相似色散特性的玻璃等方法将双高斯物镜复杂化,并且通过减小透镜通光口径消除部分边缘光线来改善像质。最终设计出的光学系统在空间频率30lp/mm时MTF 大于0.55,且各种像差都得到了很好地校正,像质均匀,满足宽谱段大口径摄影镜头的要求。     

94GHz缓变结构回旋管设计与数值模拟研究

通过分析广义传输线理论中的模式耦合系数,优化设计了一支94GHz光滑缓变结构回旋管,当电子注电压50kV,电流6A,横纵速度比1.4,工作磁场3.548 5T时,在频率94.099GHz处得到了41%互作用效率,约120kW的功率输出;与折变结构回旋管相比,缓变结构回旋管中的工作模式纯度提高约27dB,注波互作用效率提高约7%。基于自洽非线性理论计算的互作用效率与PIC模拟结果有较好的一致性。     

Some features of operation of a heterodyne receiver with the Mach-Zender diplexer in a wide wave region

The relations between the diplexer transmission coefficient, the noise suppression depth of a local oscillator and the path difference of an interferometer, maximum operating wavelength, intermediate frequency amplifier characteristics are considered.     

A diode laser spectrometer at 634nm and absolute frequency measurements using optical frequency comb

This paper reports that two identical external-cavity-diode-laser (ECDL) based spectrometers are constructed at 634 nm referencing on the hyperfine B-X transition R(80)8-4 of ¹²⁷I₂. The lasers are stabilized on the Doppler-free absorption signals using the third-harmonic detection technique. The instability of the stabilized laser is measured to be 2.8×10^-12 (after 1000 s) by counting the beat note between the two lasers. The absolute optical frequency of the transition is, for the first time, determined to be 472851936189.5 kHz by using an optical frequency comb referenced on the microwave caesium atomic clock. The uncertainty of the measurement is less than 4.9 kHz.     

Theoretical and numerical studies on a planar gyrotron with transverse energy extraction

In this paper, we study the planar gyrotron theoretically and numerically. Applying the large-signal theory to the planar gyrotron, the wave equation of electric field and the equation of motion of an electron are simultaneously solved to obtain some characteristic parameters, such as the phase-space plot of electrons, working frequency, startup time, electronic efficiency, and output power of the device. To verify the formulations used in this paper, three-dimensional particle simulations are performed on the same device, and the numerical results accord well with those obtained by using the large-signal theory. Theoretical and numerical results show that the electronic efficiency can reach 21% for the prototype of the planar gyrotron working at the frequency of 0.81 THz.     

Coherent diffraction radiation as a source of radiation in far-infrared and terahertz range

The results of measurements of the coherent diffraction radiation yield generated by femtosecond electron beam are presented. It is shown that the simulated and experimental data agreed quite well. The coherent diffraction radiation can be considered as a real candidate to develop a source of radiation in far-infrared and terahertz range.