chandra.romel@LIGO.ORG - posted 09:21, Wednesday 25 April 2018 - last comment - 17:06, Wednesday 25 April 2018(41657)
CP4 GN2 heat
The GN2 temp was running low at around 120C. I raised the variac from 60% to 64%. As we run the Dewar dry, we will try to maintain a temperature around 180C. Dewar is currently 43% full, with a ~7%/day consumption. Flow is 40-50 scfhx100.
I valved out the UHP GN2 from the turbo foreline; foreline pressure is back to 7.1e-3 Torr.
GN2 temps rising over 200C this afternoon, so I a) lowered the variac from 64% to 60% and b) opened the pressure build valve by another 1/8 turn + 1/4 turn (I believe it's open 1/2 turn total now). The Dewar head pressure has fallen today from 17 to 16 psig. The late afternoon sun adds a variable. Flow was low ~20 scfhx100.