Study on space charge effect in an electrostatic ion analyzer applied to measure laser produced ions.
The abundance of different ions produced by laser ion sources is usually analyzed by an electrostatic ion analyzer (EIA). Ion current intensities in the range of several mA/cm(2) at the position of the EIA have been achieved from the laser ion source developed by the Institute of Modern Physics; this indicates that a noticeable influence of space charge effect during the ion transmission will occur. Hence, while the parameters of the EIA or the beams are changed, such as ion species, current intensity, the ions' transmission efficiency through the EIA is different, which will result in an uncertainty in the estimation of the ions' yields. Special attention is focused on this issue in this paper. Ion's transmissions through the EIA under different circumstances are studied with simulations and experiments, the results of which are consistent with each other.
Ion charge state and energy distributions of laser produced plasma from pure metals and their alloy.
A high intensity highly charged laser ion source has been studied at the Institute of Modern Physics for the last few years. In order to investigate the processes of plasma heating and expansion of laser produced plasma, the charge state and energy distributions of the ions from pure copper, silver, and copper-silver alloy, in which the atom number ratio between copper and silver is 2:3, were measured with a 90° cylindrical electrostatic ion analyzer. It was shown that the yields of highly charged copper ions from the pure copper target are higher compared with those of the alloy target. In contrast, higher yields of highly charged silver ions were obtained from the copper-silver alloy target. Moreover, the ion energy distributions were derived from the time-of-flight spectra for the ions with different ion charge states and compared between the pure metal and alloy targets.
Secondary electron emission from 0.5–2.5‐MeV protons and deuterons
Measurement of the secondary electron currents leaving Al, V, Fe, 316 stainless steel, Nb, and Mo foils undergoing 0.5–2.5‐MeV proton and deuteron bombardment were made to determine the secondary electron emission ratios for these ions. The measured secondary electron yields were of the order of 1.0, with the deuterons producing generally higher yields than the protons.