行波离子迁移谱的行波脉冲电源设计及应用

基于行波的无损离子操作结构装置(TW-SLIM)是一种新型的可实现复杂气相离子操作的离子漂移管,是行波离子迁移谱(TWIMS)的核心器件,其利用行波脉冲电源提供振荡电场实现离子传输和分离。针对行波无损离子操作结构特性,采用现场可编程逻辑门阵列(FPGA)作为行波脉冲信号源,使用集成半桥驱动器作为栅极驱动,以金属氧化物半导体场效应管(MOSFET)构成的半桥拓扑电路作为脉冲输出级,使用可调高压电源作为半桥电路的直流母线电源,设计了一种行波脉冲电源。脉冲电源输出脉冲电压最大频率可达100 kHz,峰-峰值可达200 V,上升时间和下降时间均小于20 ns。在实验室自制的行波离子迁移谱仪器平台上测试了行波幅值和频率对离子传输和离子分离的影响。结果表明,当频率为10 kHz、幅值为35 V时,六(2,2-二氟乙氧基)磷腈的传输效率最高;在行波幅值不变时,随着行波频率的增大,离子信号强度减小。利用六(2,2-二氟乙氧基)磷腈和六(1H,1H,3H-全氟丙氧基)磷氮烯探究行波幅值和频率对离子基于结构分离情况的影响,在行波幅值不变时,随着行波频率增大,对2种离子的分离能力变强;在频率不变时,随着行波...     

A study of the switching of the microwave compressor switch in a circular waveguide

Results of the experimental study of the interference switch for the H ₁₁ mode in a circular 10-cm-wavelength waveguide are presented. The conditions required for efficient microwave discharge switching of the interference switch are determined. The results of the study of the switching process allowed us to design and produce an interference switch with better characteristics than those of rectangular waveguides. It is shown that this switch extracts the stored energy from the microwave compressor cavity more efficiently and improves the amplitude stability of the output pulse radiation.     

Rapid Extraction of Microwave Energy from an Overmoded Storage Cavity

The resonant compressor of microwave pulses contains an overmoded cavity with an overmoded output waveguide. The commutator is a bandpass filter formed of a chain of transmission-type (reentrant) cavities. The basic results of the experiments carried out at low and high power levels and a block diagram of the experimental setup are presented. The compressor has the following performance characteristics: (1) an operating radio frequency of 9.16 GHz, (2) a power gain of 16.3 dB, and (3) the duration of the output pulses is 2 ns. The latter figure ensures the minimum energy output time.     

Beam current enhancement of microwave plasma ion source utilizing double-port rectangular cavity resonator

Microwave plasma ion source with rectangular cavity resonator has been examined to improve ion beam current by changing wave launcher type from single-port to double-port. The cavity resonators with double-port and single-port wave launchers are designed to get resonance effect at TE-103 mode and TE-102 mode, respectively. In order to confirm that the cavities are acting as resonator, the microwave power for breakdown is measured and compared with the E-field strength estimated from the HFSS (High Frequency Structure Simulator) simulation. Langmuir probe measurements show that double-port cavity enhances central density of plasma ion source by modifying non-uniform plasma density profile of the single-port cavity. Correspondingly, beam current from the plasma ion source utilizing the double-port resonator is measured to be higher than that utilizing single-port resonator. Moreover, the enhancement in plasma density and ion beam current utilizing the double-port resonator is more pronounced as higher microwave power applied to the plasma ion source. Therefore, the rectangular cavity resonator utilizing the double-port is expected to enhance the performance of plasma ion source in terms of ion beam extraction.     

Studying a gas-discharge switch of a high-power microwave compressor

The results of a study of a high-pressure gas-discharge switch with a blown-through discharge gap are presented. This switch is designed for controlling the energy-storage and-extraction processes in a high-power resonance microwave compressor operating in the 10-cm wavelength region. The dependences of the amplitude stability of the compressor output pulses on the level of the switched power, pulse repetition rate, pressure of the insulating gas, composition of the gaseous mixture (N₂ and SF₆), blowing-through rate, and features of the discharge-gap configuration are presented. A version of the switch design with a high junction attenuation (～40 dB) of the compressor’s interference switch, which operates at a switched power of ～160 MW at a maximum switching power of 200 Hz and an rms deviation of the output-signal amplitude of ～2–5%, is given.     

An antenna-feed system with an RF drive source for a Cherenkov maser—an antenna-amplifier

The microwave transmission system of an X-band antenna-amplifier (a relativistic traveling-wave tube intended for operation in the fundamental nonaxisymmetric HE ₁₁ mode of a dielectric rod) has been investigated. A specially designed two-frequency tunable resonance microwave pulse compressor is used as an RF drive source. The microwave transmission system is incorporated into a hollow high-voltage electrode of a linear induction accelerator. It is shown that this transmission system can be reasonably matched in a frequency band of about 700 MHz, and microwave pulses with a duration of ～4 ns and a peak power of at least up to 1.6 MW can be transmitted via it without substantial losses and envelope distortions. It is also shown that the actual configuration of the device virtually does not affect the angular distribution of the far-field radiation pattern of the rod antenna, which is an extension of the slow-wave structure of the amplifier.     

A laser system for the parametric amplification of electromagnetic fields in a microwave cavity

We describe recent improvements in the development of the high power laser system used in the motion induced radiation (MIR) experiment to amplify electromagnetic fields inside a microwave cavity. The improvements made on the oscillator stabilization, the pulse train shaping device, and the spatial beam uniformity are reported.     

The Ring Dye Laser as a Source for Two-Photon Excited Fluorescence

ABSTRACT

The near-Gaussian beam profile, low pulse-to-pulse amplitude fluctuation and amenability to simple signal processing make synchronously-pumped dye lasers, both continuous and cavity-dumped, excellent sources for two-photon spectroscopy. In recent years attention has shifted from the more common standing wave configuration to a traveling wave ring laser of synchronous length. The continuous variant has proven to be a source with a detectivity for two-photon excited fluorescence equal to the cavity-dumped, standing wave laser but without the added optical and electronic complexity of the Bragg cell. However, cavity gain/loss, bandwidth and length changes influence pulse characteristics to a different extent than in standing wave lasers. These effects are discussed relative to both the two-color, two-photon experiment and overall instrumental design considerations.     

Optimization of high-voltage devices for energy compression of nanosecond pulses

Designs of compact converters intended for compression of high-voltage pulses with durations of a few nanoseconds and operating in a traveling wave mode were examined. The energy compression unit contained two lines-high-impedance and forming-with a high -pressure gas spark discharger used as a switch. A traditional serial connection of lines was replaced by a parallel connection to increase the energy compression efficiency. The power of the initial pulse (amplitude, 145 kV; half-height duration, 4 ns; and rise time, 1.5 ns) at a load of 45 Ω was increased by a factor of 1.8, while the calculated value was 2.5. The amplitude was as great as -195 kV, and the power was 17% higher relative to the circuit with a serial connection of lines. When shaped, the pulse was compressed in time to 0.8 ns. Two modifications of devices converting the initial pulse with an amplitude of -160 kV and a rise time of 0.3 ns into pulses with amplitudes of -210 and -250 kV and durations of 0.80 and 0.45 ns, respectively, were tested. Waveguide components of the converters were developed, with which it was possible to minimize the dimensions of the device in order to avoid excitation of higher harmonics while maintaining the electric strength.     

基于非线性复杂测度的往复压缩机故障诊断

往复压缩机以多源非线性冲击振动信号为主,应用传统方法难以从振动信号中提取故障特征,为此提出一种基于非线性复杂测度的往复压缩机故障诊断方法。以气阀正常、阀片有缺口、阀片断裂及弹簧损坏4种状态下往复压缩机气阀振动信号为分析数据,在小波阈值降噪处理的基础上,采用均值符号化方法计算信号的归一化Lempel-Ziv复杂度(Lempel-Zivcomplexity,LZC)指标,分别给出各状态相应的LZC特征区间,利用BP人工神经网络对各状态信号的有效值特征、功率谱能量特征及LZC特征分别进行训练和测试,结果表明LZC更能准确区分不同状态的往复压缩机气阀故障,为往复压缩机故障诊断和维修决策提供了一种有效方法。     

A nanosecond SOS-generator with a 20-kHz pulse repetition rate

A nanosecond SOS-generator with a 20-kHz pulse repetition rate in the continuous operating mode and with a 100-kHz pulse repetition rate in the pulse burst mode is described. The generator contains a low-voltage module with a primary capacitive storage and a transistor switch, and a high-voltage module with a magnetic compressor and a semiconductor opening switch (SOS diode). The generator forms pulses with amplitudes of 40–100 kV with a 20- to 30-MW peak power and a 10- to 14-ns duration across a 50- to 500-Ω external load. The output average power in the continuous operating mode is 5 kW. The electric circuit, principle of operation, and design of the generator’s elements are described. The test results are given.     

A compact semiconductor opening swith-based generator with a 300-kV output voltage and up to 2-kHz pulse repetition rate

A compact generator with a semiconductor opening switch (SOS-diode) shaping across resistive load pulses with an amplitude of up to 300 kV, duration of 30–50 ns, and a 300-Hz pulse repetition under uninterrupted operation and up to 2 kHz in a 30-s burst mode is described. The generator contains a thyristor charging device, magnetic compressor, and inductive storage with a semiconductor opening swith based on SOS-diodes. The average output power at a maximum pulse repetition rate and a 250kV-voltage is 16 kW. The overall dimensions of the generator are 0.85×0.65×0.42 m, the weight is about 115 kg.     

Stable microwave coaxial cavity plasma system at atmospheric pressure

We present a systematic study of the development of a novel atmospheric microwave plasma system for material processing in the pressure range up to 760 torr and the microwave input power up to 6 kW. Atmospheric microwave plasma was reliably produced and sustained by using a cylindrical resonator with the TM(011) cavity mode. The applicator and the microwave cavity, which is a cylindrical resonator, are carefully designed and optimized with the time dependent finite element Maxwell equation solver. The azimuthal apertures are placed at the maximum magnetic field positions between the cavity and the applicator to maximize the coupling efficiency into the microwave plasma at a resonant frequency of 2.45 GHz. The system consists of a magnetron power supply, a circulator, a directional coupler, a three-stub tuner, a dummy load, a coaxial cavity, and a central cavity. Design and construction of the resonant structures and diagnostics of atmospheric plasma using optical experiments are discussed in various ranges of pressure and microwave input power for different types of gases.     

A broadband Fourier transform microwave spectrometer based on chirped pulse excitation

Designs for a broadband chirped pulse Fourier transform microwave (CP-FTMW) spectrometer are presented. The spectrometer is capable of measuring the 7-18 GHz region of a rotational spectrum in a single data acquisition. One design uses a 4.2 Gsampless arbitrary waveform generator (AWG) to produce a 1 mus duration chirped pulse with a linear frequency sweep of 1.375 GHz. This pulse is sent through a microwave circuit to multiply the bandwidth of the pulse by a factor of 8 and upconvert it to the 7.5-18.5 GHz range. The chirped pulse is amplified by a traveling wave tube amplifier and broadcast inside the spectrometer by using a double ridge standard gain horn antenna. The broadband molecular free induction decay (FID) is received by a second horn antenna, downconverted, and digitized by a 40 Gsampless (12 GHz hardware bandwidth) digital oscilloscope. The second design uses a simplified pulse generation and FID detection scheme, employing current state-of-the-art high-speed digital electronics. In this spectrometer, a chirped pulse with 12 GHz of bandwidth is directly generated by using a 20 Gsampless AWG and upconverted in a single step with an ultrabroadband mixer. The amplified molecular emission is directly detected by using a 50 Gsampless digital oscilloscope with 18 GHz bandwidth. In both designs, fast Fourier transform of the FID produces the frequency domain rotational spectrum in the 7-18 GHz range. The performance of the CP-FTMW spectrometer is compared to a Balle-Flygare-type cavity-FTMW spectrometer. The CP-FTMW spectrometer produces an equal sensitivity spectrum with a factor of 40 reduction in measurement time and a reduction in sample consumption by a factor of 20. The CP-FTMW spectrometer also displays good intensity accuracy for both sample number density and rotational transition moment. Strategies to reduce the CP-FTMW measurement time by another factor of 90 while simultaneously reducing the sample consumption by a factor of 30 are demonstrated.     

基于UCC3895的行波型超声波电机驱动器设计

以往的基于非智能芯片的超声波电机驱动器往往存在电路复杂,调相困难等不足,因而限制了其使用范围。针对这一问题,首先简要介绍了行波型超声波电机驱动电路基本原理和性能要求;在比较以往驱动器优缺点的基础上提出了一种基于UUC3895的多功能可调节的行波型超声波电机驱动器,该驱动器基于BiCMOS相移谐振脉宽调制（PWM）控制原理,具有调频、调压和调相功能,并可扩展外部控制器;最后,给出了实验数据与波形图。实验结果验证了该设计的可行性。     

An Injection and Acceleration System of a Pulsed Race-Track Microtron

A pulsed race-track microtron (RTM) with a maximum beam energy of 70 MeV [1] is described. This device was developed at the Research Institute of Nuclear Physics of Moscow State University (Russia) in cooperation with World Physics Technologies Inc. (USA). For this project, several new elements, including bending magnets (based on rare-earth permanent magnets) [2], a system for injection of the bunched electron beam through a compact -magnet (also based on permanent magnets [3]), and a rectangular cavity biperiodic structure (RCBS) [4, 5], were developed. Unlike axially symmetric accelerating structures, the RCBS has small transverse dimensions and, as a result, does not present an obstacle for the electron beam traveling in the first orbit. Moreover, the RCBS possesses a quadrupole focusing with the value and sign of the focal power depending on the relationship between the size of the drift aperture and the dimensions of the microtron cavity and on the phase of the microwave field. These properties substantially simplify the RTM design and tuning. Tests, the tuning procedure, and measured characteristics of the injection and acceleration systems of the race-track microtron are described.     

Linear induction accelerators made from pulse-line cavities with external pulse injection

Two types of linear induction accelerator have been reported previously. In one, unidirectional voltage pulses are generated outside the accelerator and injected into the accelerator cavity modules, which contain ferromagnetic material to reduce energy losses in the form of currents induced, in parallel with the beam, in the cavity structure. In the other type, the accelerator cavity modules are themselves pulse-forming lines with energy storage and switches; parallel current losses are made zero by the use of circuits that generate bidirectional acceleration waveforms with a zero voltage-time integral. In a third type of design described here, the cavities are externally driven, and 100% efficient coupling of energy to the beam is obtained by designing the external pulse generators to produce bidirectional voltage waveforms with zero voltage-time integral. A design for such a pulse generator is described that is itself one hundred percent efficient and which is well suited to existing pulse power techniques. Two accelerator cavity designs are described that can couple the pulse from such a generator to the beam; one of these designs provides voltage doubling. Comparison is made between the accelerating gradients that can be obtained with this and the preceding types of induction accelerator.     

Microwave Diagnostics for Studies of Electromagnetic Scattering by Fluorescent Lamp Plasma

This paper reports a related microwave diagnostic method that measures both the electron number density and the electron-neutral collision frequency,which are crucial to understand the behavior of microwave traveling in plasma.Arrays of standard commercial fluorescent lamp placed directly against each other in two rows are used to produce a plasma layer.Attenuations of microwave by plasma layer are studied experimentally in the frequencies of 1～8 GHz using a synthesized signal generator and a spectrum analyzer.Two wave-polarizations are under investigation:electric field of the wave is either parallel(E-wave)or perpendicular(H-wave)to the fluorescent lamp axis.The electron number density and the electron-neutral collision frequency of fluorescent lamp plasma are obtained by microwave diagnostics,for the purpose of analyzing microwave scattering characteristics by plasma.     

High-efficiency coaxial relativistic backward wave oscillator

This paper studies the coaxial relativistic backward wave oscillator (CRBWO) through analytical, numerical, and experimental methods. This new type of device is remarked by its high efficiency of more than 35%, which is predicted by the theoretical calculation and the numerical simulation and validated by experiment. The two primary hindrances preventing CRBWO from achieving the expected high efficiency, the poor coaxiality and the power capacity, are discussed in detail and some advanced methods are developed. The theoretical and numerical conclusions agree with the experiment results, which are obtained from the electric probe and the calorimeter simultaneously for each shot of CRBWO. Employing the electron beam pulse of the full width at half maximum 28 ns, a microwave pulse of the width about 20 ns is generated in the experiment; the power is 710 MW and the efficiency is higher than 33%.     

储罐抗震计算模型的简化

针对立式钢制储罐抗震计算的模型简化问题,将储罐简化为三质点体系,即晃动质点、液固耦合质点、刚性脉冲质点。液体的晃动频率远低于罐壁的频率,所以可以忽略液体的晃动和壳体振动的耦合,将储罐简化为液固耦合质点、刚性脉冲质点的二质点体系。通过数值分析发现可将储罐简化为单质点体系,即只考虑液固耦合质点。与规范算法（只能计算出最大值）相比,误差不大。因此,可采用单质点体系计算得出储罐在任意地震波输入下任意时刻的地震时程响应,从而大大减少了计算工作量。