john.worden@LIGO.ORG - posted 16:39, Wednesday 21 October 2015 - last comment - 10:00, Thursday 22 October 2015(22736)
MIDY vacuum leak
Kyle will report more but here is a plot of pressure for the last 4 hours. We are not sure how permanent this "fix" might be but the magnitude of recovery suggests that this is the dominant or only leak in this volume.
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This morning the pressure is at 1.6e-9 torr. We had been at 4.6e-9 torr. At these pressures the main ion pump may have 1000 l/s pumping speed (guess) for air. Given this the air leak was on the order of 3e-6 tl/s.
The largest signal seen on the helium leak detector was ~ 1e-7 tl/s for helium. However, the leak detector was only sampling a fraction of the helium as we are open to the beam tube on both sides.