Calculation of the maximum temperature on the carbon stripping foil of the Spallation Neutron Source

The maximum temperatures expected on both 220 μg/cm² and 400 μg/cm² carbon foils, used to strip the 1 GeV H beam at injection into the accumulator ring of the Spallation Neutron Source (SNS), were determined by finite-element analysis. This beam will have a pulse length of 1 ms with a repetition rate of 60 Hz and an average current over a single beam pulse of 18.2 mA. The foil size will be 10 mm×30 mm and will be mounted in a 20 cm diameter stainless steel beam pipe in the injection area of SNS. In the model, the heat generated in the foil was radiated to the wall of the beam pipe, which was exposed to ambient temperatures. The results showed that the maximum temperatures were 1728 K for the 400 μg/cm² case and 1574 K for the 220 μg/cm² case. A 225 μg/cm² thick commercial carbon foil was tested to verify the analysis. The experiment used the 750 keV H beam at the AGS Linac, which has a pulse length of 0.5 ms and a repetition rate of 7.5 Hz. By using the same mathematical model as described above, the maximum temperatures on the foil corresponding to various energy depositions were calculated and were compared against the carbon melting temperature (3973 K). The results showed that: 1. When the predicted maximum temperature was above the carbon melting temperature, the foil failed within 1 minute of running time. 2. When the predicted maximum temperature was below the carbon melting temperature, the performance of the foil was not affected up to the end of our 10 minutes tests