一种诱导肿瘤细胞凋亡的多参数可调高压纳秒脉冲发生器

为了研究纳秒脉冲电场诱导肿瘤细胞的凋亡效应及其窗口参数选择规律,本文结合脉冲功率技术和Blumlein集中参数LC网络脉冲形成线原理,研制出了一台医用多参数可调、便携式、智能型高压纳秒方波脉冲发生器。该发生器主要由高压直流电源、纳秒脉冲形成系统和脉冲整形及计数系统三部分组成,输出脉冲幅值4～15kV连续可调,脉宽50～500ns可变,上升沿最小10ns,重复频率可调,治疗时间窗口可控,并具有液晶显示和保护功能。以人浆液囊腺性卵巢癌SKOV3为研究对象,正交设计出多种脉冲参数组合进行实验分析,探索出肿瘤细胞凋亡率较高的脉冲治疗窗口参数。医学实验表明:发生器紧凑、轻便、性能稳定,有效满足了纳秒脉冲电场诱导肿瘤细胞凋亡的机理及窗口参数选择的研究需要。     

可编程器件在纳秒级多通道数字延迟/脉冲发生器中的应用

研制了用于飞行时间质谱仪（TOF）的多通道数字延迟/脉冲发生器系统。介绍了复杂可编程器件（CPLD）和可编程数字延迟线（AD9501）在系统中的应用，讨论了高速数字系统中的定时误差问题。该系统的延迟分辨率达1ns，脉冲宽度分辨率为100ns，可同时控制五台设备工作。     

纳秒级脉冲电源的研制

根据微细电化学加工的工艺特点,采用FPGA和MOSFET设计了双MOSFET的电化学加工纳秒级脉冲电源。该脉冲电源可以提供脉宽和脉问以及占空比可调的纳秒级脉冲,输出脉宽最小可达40ns,提高了加工过程的稳定性和加工极限能力;并利用阳极腐蚀结合湿印章的“电化学湿印章技术”实现了微细电化学加工,获得了较高的分辨率。     

应用于磁光开关的纳秒脉冲发生器设计

探讨了一种可用于磁光开关的基于雪崩晶体管的纳秒脉冲发生器,对其电路及雪崩晶体管的工作原理进行了具体分析,并对纳秒脉冲发生器电路进行计算机仿真和实验验证.测试结果表明:这种纳秒脉冲发生器能够输出上升沿2～5ns、脉宽6～20ns和上升幅度30～100V的脉冲,很适合用于全光通信网络中的磁光开关.     

高频窄脉宽微细电火花加工用微能脉冲电源的研究

分析了微能脉冲电源的实现途径。采用开关管推挽工作原理设计出了具有高频窄脉宽的微细电火花加工用微能脉冲电源。并对具有陡上升沿和下降沿的高频脉冲电源工作时产生的电磁振荡现象的原因进行了深入的研究。在此基础上设计出的脉冲电源最小脉宽可达100ns，较好地满足了微细电火花加工的需要。     

基于Blumlein和TLT的模块化全固态纳秒脉冲发生器

为了研究高频纳秒脉冲电场治疗肿瘤的生物医学效应,需要一种能产生高频纳秒脉冲的紧凑型脉冲电场发生器。结合Blumlein脉冲形成线和传输线变压器(TLT)提出了一种新的模块化设计的高频纳秒脉冲发生器结构,发生器可以使用更少的开关数输出电压、频率可调的高频纳秒方波脉冲。对单级和多级发生器在阻抗匹配时的脉冲形成过程进行了理论分析,并分析了多级发生器在阻抗不匹配时负载波形的变化;使用微带线设计Blumlein脉冲形成线,介绍了微带线的设计过程,同时介绍了传输线变压器的设计以及固态开关的控制策略;研制了一台小型发生器对提出的拓扑结构进行验证。最后,三级发生器在匹配负载(300Ω)上,可以输出幅值0~3 kV可调,脉宽100 ns,重复频率0~10 kHz可调的高频纳秒脉冲。     

4.5兆伏单级静电加速器及其应用

北京大学新建成的单级静电加速器端电压在0．4—4．5MV范围内连续可调，稳定度在±1kV左右，可以加速氢、氘等轻离子及碳至氩等多电荷重离子，分析流强可到15—2μA（质子氘离子），建有两条束流输运线，能量分辨率分别可到1．3±10-3和4．2×10-4，传输效率高于90％，在加速器高压电极内有速流脉冲化装置，可在靶上提供脉冲宽度约1．6ns、平均流强1μA、重复频率为3MHz的脉冲束流。该器目前主要用于中子实验工作。     

可编程恒流脉冲的设计

介绍利用８０９８单片机控制的恒流，但电流、脉冲个数和脉冲宽度可调，脉冲上升、下降沿时间小于１０μＳ，恒流精度可达１％的恒流脉冲的实现方法。     

9500 1GHz程控示波器校准源

韦夫特克公司的9500型示波器校准源应用了独特的先进技术,具有其它示波器校准仪难以媲美的程控性、通用性和准确度.9500型可以校准1GHz以内的各种模拟式和数字式示波器及示波表.它采用独特的有源探头可保证所有校准信号在示波器输入端的准确度,精密的50Ω匹配更确保了波形的完善.有源探头技术是韦夫特克公司的专利技术.它克服了传统方法难以解决的快沿一致性问题,大大改善了电压驻波系数,减少了集肤效应和介质损耗,确保了高速脉冲和高精度高频正弦波信号的质量.9500型应用快速阶跃二极管和肖特基二极管,产生出幅值5mV至3V连续可调节的、固定延时150ps的快跳沿信号;幅值达±200V、10Hz～100kHz优于100ns的高压快跳沿信号.优异的砷化稼二极管为高频正弦波取样提供了良好的隔离,使9500型能输出连续可调的0.1Hz至1.1GHz的精密正弦波.9500型按正弦、方波、窄三角波和脉冲四种形式输出时标信号,     

用于半导体激光器的大电流纳秒级窄脉冲驱动电路

根据脉冲式半导体激光器对功率、脉宽、上升沿的要求,同时考虑电脉冲的注入便于测试激光器的各种性能,提出了一种以金属氧化物半导体场效应晶体(MOSFET)为开关器件,以雪崩晶体管为驱动器,可产生大电流、窄脉宽、陡上升沿脉冲的激光器驱动电路。讨论了预触发脉冲宽度和雪崩晶体管输出负载对MOSFET输出脉冲在幅度和波形上的影响以及如何通过调整耦合电阻来控制脉冲的"下冲"和振荡。实验结果表明:在0~200V供电电压下,该电路在1Ω电阻上产生了从0A到148A,具有陡上升/下降沿的10ns级电脉冲。通过调整电路参数,可输出脉冲宽度窄至8.6ns,幅度达到124A的电脉冲。该驱动电路满足了脉冲式半导体激光器的工作要求和对器件测试的要求。     

基于FPGA平台的窄脉冲大电流LED频闪光源设计

针对高频信号的特点,利用FPGA,设计了一种窄脉宽、大电流的LED频闪光源。通过FPGA平台上的编程控制,实现了满足频闪光源控制时序要求的窄脉宽信号。最后,将窄脉宽信号进行电流放大,获得脉宽为ns级,电流最大可达30A的LED驱动脉冲信号。     

水下自主航行器微光照相机驱动系统设计

提出了基于水下自主航行器的EMCCD微光照相机驱动系统设计方法。首先,分析了EMCCD输出噪声的组成,根据暗电流噪声和时钟感生噪声的关系,给出了常规功率驱动的器件选型原则和设计方法;讨论了使用图腾柱电路实现电子倍增驱动的功耗问题,并给出了改进方案;使用高频系统时钟实现了驱动相位和脉宽的微调,解决了驱动时序波形幅度重叠率不足的问题;最后,给出了使用CCD201-20搭建的水下相机结构和实验结果。实验结果表明,系统产生的常规驱动信号频率为时钟频率10 MHz,串行转移时钟的幅度重叠率优于50%,并行转移时钟的幅度重叠率优于90%,驱动信号的相位调整精度为18°,脉宽调整精度为5 ns,驱动波形稳定、平整,电子倍增驱动信号高电平可调,功耗相较于优化前降低7.2%。本文所介绍的EMCCD驱动系统设计方法充分兼顾了驱动系统的噪声、体积和功耗问题,可以广泛应用在水下微光成像乃至常规CCD领域。     

Faraday cup with nanosecond response and adjustable impedance for fast electron beam characterization

A movable Faraday cup design with simple structure and adjustable impedance is described in this work. This Faraday cup has external adjustable shunt resistance for self-biased measurement setup and 50 Ω characteristic impedance to match with 50 Ω standard BNC coaxial cable and vacuum feedthroughs for nanosecond-level pulse signal measurements. Adjustable shunt resistance allows self-biased measurements to be quickly acquired to determine the electron energy distribution function. The performance of the Faraday cup is validated by tests of response time and amplitude of output signal. When compared with a reference source, the percent difference of the Faraday cup signal fall time is less than 10% for fall times greater than 10 ns. The percent difference of the Faraday cup signal pulse width is below 6.7% for pulse widths greater than 10 ns. A pseudospark-generated electron beam is used to compare the amplitude of the Faraday cup signal with a calibrated F-70 commercial current transformer. The error of the Faraday cup output amplitude is below 10% for the 4-14 kV tested pseudospark voltages. The main benefit of this Faraday cup is demonstrated by adjusting the external shunt resistance and performing the self-biased method for obtaining the electron energy distribution function. Results from a 4 kV pseudospark discharge indicate a "double-humped" energy distribution.     

基于DDS相位差可调双通道信号发生器的设计

首先介绍了DDS（直接数字频率合成技术）的基本原理,之后给出基于FPGA器件实现相位可调双路同频正弦信号发生器的设计系统。采用VHDL实现了各个模块的功能,并同时在QuartusII中完成了设计与仿真,给出了软件仿真和试验的结果。实验结果表明,该系统生成的双路同频正弦信号具有波形失真小、频率和相位精度高、输出频率和相位可调等优点。     

High resolution heterodyne interferometer based on time-to-digital converter

A new heterodyne interferometer is presented, which adopts time-to-digital converter (TDC) measuring the time intervals of zero crossings of heterodyne signal for phase demodulation. Thanks to the 0.1 ns time resolution of TDC and linear phase demodulation, it can achieve high resolution and avoids nonlinear measuring distortion in other indirect high precise phase demodulation methods, such as pulse width modulation (PWM) and in-phase∕quadrature (I∕Q) method.     

Generation of electron beams with adjustable durations of 1.0–0.2 ns and current amplitudes more than 400 A

The conditions for forming subnanosecond electron beams with adjustable pulse durations in the vacuum-diode mode using a SLEP-150 generator were investigated. It was confirmed that the residual air pressure in the diode (～0.1 Torr or less) does not affect the amplitude and duration of the beam current when using a nanosecond voltage pulse. It was shown that increasing the air pressure in the diode from 0.1 to 6.0 Torr leads to a decrease in the full width at half-maximum (FWHM) duration of the electron-beam current from ～1.00 to 0.18 ns and a shorter delay of the beam generation moment relative to the voltage-pulse rise time. It was established that the amplitude of the first peak of the beam current behind the foil remained constant under these conditions. Its value was ≥400 A. It is shown that when the interelectrode gaps are optimal for vacuum diodes, the pulse duration at elevated pressures shortens due to the gap breakdown for a time of ≤200 ps.     

32 bin near-infrared time-multiplexing detector with attojoule single-shot energy resolution

We present two implementations of photon counting time-multiplexing detectors for near-infrared wavelengths, based on Peltier cooled InGaAs/InP avalanche photodiodes. A first implementation is motivated by practical considerations using only commercially available components. It features 16 bins, pulse repetition rates of up to 22 kHz, and a large range of applicable pulse widths of up to 100 ns. A second implementation is based on rapid gating detectors, permitting dead times below 10 ns. This allows one to realize a high dynamic-range 32 bin detector, able to process pulse repetition rates of up to 6 MHz for pulse widths of up to 200 ps. Analysis of the detector response at 16.5% detection efficiency reveals a single-shot energy resolution on the attojoule level.     

基于虚拟仪器的脉冲信号发生器

主要以定时/计数器卡PCI-TMC12A为例,介绍了以虚拟仪器技术为基础,实现输出脉冲周期、脉宽以及输出脉冲数可调的脉冲信号发生器的一种方法。     

Nanosecond gating of an optical multichannel analyzer

An optical gating pulse of 30 ns width combined with an electronic gating pulse of 50 ns width has been found to give a near perfect performance of a gated silicon intensified vidicon detector. The magnification as well as the focusing properties are found to be close to the real-time behavior and the small changes that do occur in the gated mode can be corrected for in the data analysis.