Researchers in Institute of Modern Physics, Chinese Academy of Sciences (IMP) made progress in the research of electron emission on fusion-relevant tungsten and graphite surfaces induced by highly charged neon and xenon ions. The secondary electron yields were measuredat the surface physics terminal of the 320kV ECRIS Platform at IMP. From the experimental results, the contributions of the kinetic electron yield and the potential electron yield was separated.
Total electron emission yield 
as a function of available potential energy 
of the incident ions for normal impact of 40Neq+ (q = 3-8) on W and 129Xeq+ (q = 10-30) on HOPG are shown in Fig. (1a) and (2a). For a given impact energy the data points lie along a linear line and these lines are shifted to larger 
values for higher projectile energies, indicating that contribution of kinetic electron emission can be estimated from the data. The “pure” potential electron emission yields γPE obtained after subtracting the evaluated 
values are plotted versus 
in Figs. (1b) and (2b) respectively. γPE can be approximated as: 
The fraction of ion’s potential energy for potential electron emission 
is given as:
The values of k and 
for various ion-target combinations and ion impact energies obtained from Fig. (1b) and (2b) are given in Table 1. Roughly 10% of the potential energy is consumed in potential electron emission.
The result has been published in Nuclear Instruments and Methods in Physics Research B 269 (2011) 977-980.
Fig. 1. (a) Total secondary electron yield as a function of available potential energy for Neq+ impact of W. (b) True potential electron yield as a function of available potential energy for Neq+ impact of W.(Image by IMP)
Fig. 2. (a) Total electron yield as a function of available potential energy ofXeq+ impact onHOPG. (b) True potential electron yield as a function of available potential energy ofXeq+ impact onHOPG. (Image by IMP)
(Image by IMP)
Introduction
