Neutronics calculation, dosimetry analysis and gas measurements of the first SINQ target irradiation experiment, STIP-I

To precisely determine the damage, helium and hydrogen production in the specimens irradiated in Swiss Spallation Neutron Source Target-3, calculations with the MCNPX code, dosimetry analysis and helium/hydrogen measurements have been performed. The MCNPX calculations agree well with the former calculations performed with the LAHET code. The preliminary analysis of dosimetry foils demonstrates that the unfolded proton and neutron spectra at limited positions are close to calculated values. In general the measured He concentrations were consistent with the calculated values. Some discrepancy between the measured and calculated values is believed due to the actual proton beam geometry being different from that used for the calculation. The hydrogen concentration measured in samples irradiated at <∼100 °C is close to the calculated. The differences between the measured and calculated values for samples irradiated at higher temperatures can be attributed largely to the effects of hydrogen diffusion. The results indicate that at >∼250 °C, only a small amount of hydrogen remains in the samples.