Production of Sub-MeV Positive Gold Ion Beams with Various Gas Targets to Improve the Tandem Accelerator of the LHD-HIBP

概要

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To expand the application range of heavy ion beam probe measurement in the Large Helical Device (LHD), it is important to increase the probing beam current. The current can be increased by improving the charge exchange efficiency in a gas cell. Experiments were conducted on a tandem accelerator at Kobe University, 5SDH-2, which allows various experimental conditions such as gas species, gas pressure, and beam energy to be selected. Initially, the gas thickness was determined by a beam attenuation method with a He+ ion beam. Next, the dependence of the positive beam current on the gas thickness was measured. The ionic charge fraction of the accelerated beam was measured and compared with the value calculated using the ionization cross section calculated in [M. Nishiura et al., NIFS Report, NIFS-884 (2008)]. The dependence of the Au+ fraction on the target gas thickness shows good qualitative agreement with the experimental value. However, the cross sections obtained experimentally are several times larger than those calculated.