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KAGRA VIS Operations Manual - Pumpdown and Venting Procedure
Pumpdown of the vacuum chambers causes large mechanical stresses which tilt the IPs and cause them to drift. Also, loss of buoyancy from the air on the suspended masses causes the GAS filters to sag. Similar changes happen in reverse on venting. Therefore it is necessary to monitor the suspensions during pumpdown and venting to correct any alignment issues before they lead to problems. See detailed procedures below.
- Allocate each of the four desktop workspaces of a control room workstation to a different suspension, e.g., BS=1, SR2=2, SR3=3 and SRM=4.
- On the first workspace, bring up:
- The sitemap.
- The VIS_ALL screen. Open all four TOP screens and drag them to the appropriate workspaces.
A terminal window. In the terminal window, log into k1script. Start the drivers for BS_IP, SR2_IP, SR3_IP, SRM_IP with commands like step_start BS_IP. Check that you get the Testing connection: ...ok message for each.
- The STEP_MASTER screen. Open the screens for the BS_IP, SR2_IP, SR3_IP, SRM_IP steppers and drag them to the appropriate workspaces.
- For each suspension, on its allocated workspace, bring up the following screens:
- The OVERVIEW screen.
- The Guardian screen.
A StripTool set to display the three IP LVDT coil outputs on a scale of ±5000: K1:VIS-BS_IP_COILOUTF_H1_OUTPUT, K1:VIS-BS_IP_COILOUTF_H2_OUTPUT, K1:VIS-BS_IP_COILOUTF_H3_OUTPUT or the like.
Optionally also display the three GAS LVDT outputs: K1:VIS-BS_F0_COILOUTF_GAS_OUTMON, K1:VIS-BS_F1_COILOUTF_GAS_OUTMON, K1:VIS-BS_BF_COILOUTF_GAS_OUTMON or the like.
Type Bp suspensions have traversers rather than IPs, and are not too badly affected by buoyancy, so it's fine just to put them to the SAFE state with the Guardian.