Working pressure ≤4 mpa (designed according to the user's actual requirements) design temperature-196 ° C vacuum interlayer leakage rate PA · m 3/s ≤1X10-10 vacuum interlayer leakage rate PA · m 3/s ≤1X10-8 sealing vacuum degree Pa ≤5X10-2 liquid nitrogen temperature Pa ≤5X10-3 ambient temperature-40 ° C ~ 60 ° C interlayer amperage, vacuum interlayer leakage rate PA · m 3/s ≤1X10-10 vacuum degree PA · m 3/s ≤1X10-8 sealing vacuum degree Pa ≤5X10-2 liquid nitrogen temperature, the opening pressure of the whole unit is 0.2 mpa