Hu Jing, Rovey Joshua L
Aerospace Plasma Laboratory, Mechanical and Aerospace Engineering, Missouri University of Science and Technology, Rolla, Missouri 65409, USA.
Rev Sci Instrum. 2011 Jul;82(7):073504. doi: 10.1063/1.3610649.
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.
本文描述了一种结构简单、阻抗可调的可移动法拉第杯设计。该法拉第杯具有用于自偏置测量设置的外部可调分流电阻，以及50Ω的特性阻抗，以匹配50Ω标准BNC同轴电缆和用于纳秒级脉冲信号测量的真空馈通。可调分流电阻允许快速获取自偏置测量结果，以确定电子能量分布函数。通过对输出信号的响应时间和幅度进行测试，验证了法拉第杯的性能。与参考源相比，当下降时间大于10 ns时，法拉第杯信号下降时间的百分比差异小于10%。当脉冲宽度大于10 ns时，法拉第杯信号脉冲宽度的百分比差异低于6.7%。使用伪火花产生的电子束将法拉第杯信号的幅度与校准后的F-70商用电流互感器进行比较。对于4 - 14 kV的测试伪火花电压，法拉第杯输出幅度的误差低于10%。通过调节外部分流电阻并采用自偏置方法来获取电子能量分布函数，证明了这种法拉第杯的主要优势。4 kV伪火花放电的结果表明存在“双峰”能量分布。
