Abstract
The stability of the electron thermionic emission current is one of the most important requirements for electron sources used, inter alia, in evaporators, production of rare gas excimers, and electron beam objects for high energy physics. In emission current control systems, a negative feedback signal, directly proportional to the emission current is transferred from the high-voltage anode circuit to the low-voltage cathode circuit. This technique, especially for high-voltage sources of electrons, requires the use of galvanic isolation. Alternatively, a method of converting the emission current to voltage in the cathode power supply circuit was proposed. It uses a linear cathode current intensity distribution and multiplicative-additive processing of two voltage signals, directly proportional to the values of cathode current intensity. The simulation results show that a relatively high conversion accuracy can be obtained for low values of the electron work function of the cathode material. The results of experimental tests of the dynamic parameters of the electron source and the steady-state Ie-V characteristic of the converter are presented. The implementation of the proposed Ie-V conversion method facilitates the design of the emission current controller, especially for high-voltage sources of electrons, because a negative feedback loop between the anode and cathode circuits is not required, all controller sub-components are at a common electrostatic potential.
Highlights
Thermionic electron sources operated in temperature limited or space charge limited mode are a key component of vacuum devices, which use the interaction of the thermionic electron beam with matter, including evaporators [1], X-ray photoelectron spectroscopy [2], electron beam facilities for high energy physics [3], production of rare gas excimers [4], and others, e.g., electron beam inspection for integrated circuit manufacturing process monitoring [5]
The analysis of the results shows that the described Ie-V conversion method in the cathode power supply circuit is predestined for electron sources with low electron work function of the cathode material
In order to assess the influence of the sensing resistors on the dynamic properties of the thermionic electron source, the time constant Tc and the delay time T0 were determined using step response method [13]
Summary
Thermionic electron sources operated in temperature limited or space charge limited mode are a key component of vacuum devices, which use the interaction of the thermionic electron beam with matter, including evaporators [1], X-ray photoelectron spectroscopy [2], electron beam facilities for high energy physics [3], production of rare gas excimers [4], and others, e.g., electron beam inspection for integrated circuit manufacturing process monitoring [5].The stability of the emission current has a significant impact on the quality of electron beam devices. The measurement of the emission current is performed in the high-voltage anode power supply circuit and its result is transferred as a negative feedback signal to the cathode control circuit by means of an optical fiber.
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