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HIRFL has 2 cyclotrons: a sector focus cyclotron (SFC) and a separate sector cyclotron (SSC). SFC was built in 1957. In the past 50 years, the vacuum system of SFC has been upgraded for three times. The vacuum chamber was redesigned to double-deck at the third upgrade. The working pressure in beam chamber was improved from 10-6 mbar to 10-8 mbar. SFC has delivered Pb, Bi and U beams in the past few years since the last upgrading of its vacuum chamber. SSC began to operate in 1987. The vacuum chamber of SSC has a volume of 100m3. 8 cryopumps keep the pressure from 4×10-7 mbar to 8×10-8 mbar depending on the used pump numbers (2~8). In the past 20 years, because of the contamination of oil vapour and leaks occurred in some components inside the SSC vacuum chamber, the vacuum condition has worsened than the beginning. It is a big problem to accelerate the heavier ions. The upgrade for the SSC vacuum system will be an urgent task for us. The rough pumping system of both SFC and SSC will be rebuilt recently. The oil pump units will be changed by large dry mechanical pumps. As a result, the oil vapour in two cyclotrons will be eliminated and the vacuum condition of them will be improved.
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