He gas charge stripper for high-intensity uranium beam

In the present study, a high-beam-transmission charge stripping system employing high-flow circulating He gas (∼200 L/min) for 238U35+ beams injected at 10.8 MeV/u has been developed and successfully demonstrated for the first time. He gas is confined in differentially-pumped target room: 10 mm entrance and exit apertures, a target pressure of 7.5 kPa, and a length of 50 cm. Because of the high gas leakage rate via the apertures, high-performance differential pumping and high-flow and clean gas recycling are required at the same time. To realize these, we developed multi-stage mechanical booster pump array having a nominal total pumping speed of 1.2×104 m3/h. The recycling rate of He gas of approximately 99.5% was achieved. Purification and heat removal of the target are also important subjects to sustain the charge stripping performance. The system performance has been checked irradiating 238U35+ beams with the present maximum beam current up to 13 euA (∼1 kW beam power). (author)