Validation of the distribution of stripping loss neutrals in the accelerator of the negative ion source

The difference of the stripping loss between hydrogen and deuterium is examined using two approaches. The first is the measurement of the optical beam emission. The wavelength of beam emission spectrum reflects the energy distribution of beam particles by the Doppler effect. The low-energy stripping peak is observed in the energy band corresponding to the extraction voltage, and also a moderate shoulder is distributed in the lower energy region. Secondly, the spatial and the energy distribution in the accelerator is estimated by the attenuation calculation using the vacuum pressure distribution in the accelerator. Stripping neutrals are concentrated in the low energy region, and a peak is formed at 9 keV in the energy distribution due to stripping neutrals inside the extraction grid aperture. The total stripping loss inside the accelerator is 16% for hydrogen and 24% for deuterium. The calculated Doppler-shifted spectra for hydrogen and deuterium clearly show the peak with the moderate shoulder on the redshift side, which is consistent with the measured results.