john.worden@LIGO.ORG - posted 15:46, Tuesday 14 May 2013 - last comment - 10:19, Wednesday 15 May 2013(6362)
LVEA Pumpdown
15 days of pumping is shown in the attached plot.
Several annuli remain to be pumped down.
HAM1, HAM2 - since HAM 1 is vented this annulus system(HAM1/HAM2) cannot be evacuated. Provided there are no big leaks this should be ok.
HAM 4 septum - liikewise HAM4 is vented so the septum annulus cannot be evacuated. Same comment as above - ok but not optimum.
BSC1, 2, 3 not yet evacuated.
Images attached to this report
Comments related to this report
A comparison of the pumpdown curve for the yend and the LVEA which both have a full
test mass chamber assembly give the following pressure vs time dependences on the
assumption of a 1/t water emission law:
2.3 x 10^-5
LVEA P(tdays) = ----------- torr
t(days)
5.0 x 10^-6
Yend P(tdays) = ----------- torr
t(days)
The pumping speed ratio for water and hydrocarbons becomes
F(LVEA)
-------- ~ 1/4
F(Yend)
The LVEA volume includes one ITM/ISI assembly, one BSC/ISI assembly, and two HAM ISI assemblies with all their optics and cabling. HAM1 is NOT part of this volume due to the septum in place.
ENDY has the one ETM/ISI assembly.