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当物质受到电子轰击时,离开物质表面的电子(二次电子)数与轰击物质的电子(一次电子)数之比,称该物质的二次电子发射系数δ。亦可表为:δ=I_s/I_p.式中I_p为一次电流,I_s为二次电流。实际测量中,样品输出电流为I_(?),而I(?)=I_3-I_p由于电荷的积累效应,在进行二次电子发射系数测定时只能采用存贮示波器。但存贮示波器不具有计算及自动记录结果的功能。在一般情况下,实验室测试时,先发一个单次脉冲到电子发射系统,触发其产生I_p和I_s,转换成电压再在示波器上读出其幅度,由于I_p和I_s很微弱(约10nA),由人眼观测波形幅直不可避免会有误差,作者设计了一种高灵敏度的数据处理和采集系统为解决这一问题提供了一条途径,它包括:灵敏电流放大器、A/D转换器、并行PIO输入接口、TP-801单板机、示波器和TP-801P打印机等部分构成。数据采集过程是将灵敏电流放大器输出的电压信号经A/D转换后存入的过程,高灵敏电流放大器实际是一个由高输入阴抗的电流-电压变换器和四级电压放大器组成的复合放大器。整套装置已在二次电子系数测试台上调试通过。
When a substance is bombarded by electrons, the ratio of the number of electrons (secondary electrons) leaving the surface of the substance to the number of electrons (primary electrons) of the bombardment substance is referred to as the secondary electron emission coefficient δ of the substance. Can also be expressed as: δ = I_s / I_p Where I_p is a primary current, I_s secondary current. The actual measurement, the sample output current I_ (?), And I (?) = I_3-I_p due to the accumulation of the charge effect, the secondary electron emission coefficient measurement can only be used when the storage oscilloscope. However, the storage oscilloscope does not have the function of calculating and automatically recording the result. Under normal circumstances, the laboratory test, the first issue of a single pulse to the electron emission system, triggering it to produce I_p and I_s, converted to voltage and then read the amplitude of the oscilloscope, I_p and I_s very weak (about 10nA) , It is inevitable that there will be some errors in the amplitude of the waveform observed by the human eye. The author designed a high-sensitivity data processing and acquisition system to provide a solution to this problem. It includes sensitive current amplifier, A / D converter, Parallel PIO input interface, TP-801 single board machine, oscilloscope and TP-801P printer and other components. Data acquisition process is the sensitive current amplifier output voltage signal after the A / D conversion into the process, high sensitive current amplifier is actually a high-input anti-current current-voltage converter and four voltage amplifier composed of composite amplifier . The whole set of devices has been debugged in the secondary electronic coefficient test bench.