Reports until 17:13, Monday 14 April 2025
Vacuum Systems General (GQuEST)
Daniel Grass - posted 17:13, Monday 14 April 2025 (12244)
Rate of (Pressure) Rise Test for Laser Filter Cavity Performed

[Jeff, Daniel]

We performed a rate of rise test for the Laser Filter Cavity (LFC) to determine the outgassing/leak rate (it's hard to experimentally differentiate without a bakeout or measurment over time). I turned off the Ion Pump and the pressure rose from 2.2E-7 Torr to 1.5E-6 Torr in 3 minutes from the ion pump releasing some gas. The pressure then rose linearly at 6E-10 Torr/s. Assuming the volume is ~33 liters, this gives a leak rate + outgassing of 2.7E-8 mbar*L/s. The surface area is around 1 m^2 = 1E4 cm^2. Assuming the leak rate is negligible, the desorption rate is 3E-12 L*mbar/(cm^2*s), which is excellent (almost unbelivable). There are calculations that can be made from this data to access the performance of the vacuum pumps. I might do that later. See below for the raw data and graphs.

Time (minutes) Time (seconds) Pressure (Torr)
0 0 2.2E-07
0.666666667 40 7.5E-07
3 180 1.5E-06
3.5 210 1.6E-06
7.5 450 1.7E-06
8 480 1.8E-06
11 660 1.9E-06
18 1080 2.0E-06
20 1200 2.1E-06
24.5 1470 2.2E-06
32.5 1950 2.6E-06
35.7 2142 2.7E-06
38.25 2295 2.8E-06
Images attached to this report