Design and operation of a retarding field energy analyzer with variable focusing for space-charge-dominated electron beams

Abstract

A retarding electrostatic field energy analyzer for low-energy beams has been designed, simulated, and tested with electron beams of several keV, in which space-charge effects play an important role. A cylindrical focusing electrode is used to overcome the beam expansion inside the device due to space-charge forces, beam emittance, etc. The cylindrical focusing voltage is independently adjustable to provide proper focusing strength. Single particle simulation and theoretical error analysis using beam envelopes show that this energy analyzer can get very high resolution for low-energy beams (up to 10 keV), which was found to be in good agreement with experimental results. The measured beam energy spectrum is both temporally and spatially resolved. In addition, a computer-controlled automatic system is developed and significantly improves the speed and efficiency of the data acquisition and processing. The measured beam energy spreads, are in remarkably good agreement with the intrinsic limits set by the effects of nonadiabatic acceleration in the electron gun and that of Coulomb collisions, as predicted by theory.

Charge resolved electrostatic diagnostic of colliding copper laser plasma plumes

“…The simplicity and robustness of a RFA has resulted in their proliferation in numerous areas of charge particle diagnostics such as semiconductors 46,47 , electron beam detection [48][49][50] , gaseous ion detection 51,52 , heavy metal ion detection 53,54 , high current discharge systems 55,56 and large volume plasma experiments including fusion studies [56][57][58] . repeller voltages +V r while the outer two are grounded.…”

Measurements of an expanding surface flashover plasma

“…Finally, the measurements could also be improved by the use of a well-designed retarding energy probe, such as that described in Ref. 39.…”

HIF research on the University of Maryland Electron Ring (UMER)

“…This experiment has been recently used for a dual purpose: (a) to develop and test a compact, high spatial and temporal resolution energy analyzer and (b) to investigate the evolution of beam energy spread. The energy analyzer used is a third-generation design based on a parallel-plate retarding-voltage concept, except that it introduces a collimating cylinder which improves the energy resolution by two orders of magnitude, without significantly impacting the temporal resolution [24]. This device has been used to measure the energy spread close to the LSE source and further downstream, after transport through a 1.5-m-long solenoid [12,13].…”