We cleaned all TWINAMP windows, filled 400mbar F2 + 1400mbar He for leakage detection last night. We found the pressure was dropped by 50mbar for the long tube, and we could smell pungently. Because the o-rings for window and PVDF plate were changed last month, maybe the gas leak came from the aluminum box connected to the window frame. We found some black grain in the aluminum box. The o-ings were changed immediately.