An oil-free vacuum system for vacuum plume and thermal vacuum experiments was established.The composition of vacuum system

scheme design and working modes were described in detail.The vacuum pumping time under different working modes was calculated.The vessel ultimate pumping speed tests were conducted on the roots pump

molecular pump and cryopump

respectively.The test results show that the technical indexes of the instruments are attained.Finally

the pressure maintenance ability of the vacuum vessel was measured.The average pressure rise rate of the vessel is 0.111Pa/h

corresponding to an average leakage rate of 7.24Pa·L/s

which demonstrates that the vacuum vessel has achieved a high process level.According to the experimental requirements and the selection of failure mode

the vacuum system has several working modes to choose

which increases the practicality and economy of the vacuum plume investigation experiment system.