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Venting/pumping Intermediate Image box and filling PPACs with gas
The procedures to vent/pump the S800 Intermediate Image box, and/or filling the PPAC detectors with gas must be done carefully to ensure that the PPACs are not damaged. For instance, before venting the chamber, we have to make sure that the PPACs are empty and equalized with respect to the vacuum in the chamber. In order to avoid errors, an automated gas handling system (II-GHS) was designed to perform these tasks safety. The system is schematically illustrated in the figure below. It shows the status of the valves (red: closed, white: open) when the intermediate image chamber is under vacuum and the PPACs are filled with gas:
The II-GHS equipment (valves, flow-meter, pipes, etc.) are located on the west balcony of the top level in the S3 vault (see figure below):
Vent focal-plane chamber
- Open the HV Remote Control GUI and ensure that the focal-plane detectors are unbiased
- Open the Labview gas handling system and verify that there is no gas in the CRDCs and IC. Open valves 4 (IC supply), 5 (IC bypass), 6 (IC focal-plane bypass), 20 (CRDC supply), 21 (CRDC bypass), and 22 (CRDC focal-plane bypass). The rest of the valves should be closed
- Ensure that the manual venting valve located on the south side of the chamber is closed (see figures below)
- Ensure that the FP ion gauge (I264IG) is off (see details here)
- Open PanelMate and select S800vac file in directory \\exp\files\control\ncsdata\General\Qt\Templates. Go to page 07, click on the VENT STATUS window and begin the venting procedure. The VENT VALVE I260VV window will turn red and display “OPEN”. The pressure should remain constant because the manual venting valve is still closed
- Gently open the manual venting valve until the pressure displayed in the Pirani Gauge (see figure below) increases by ~1 torr every 15 seconds (see figures below)
- Wait until the chamber is vented (few hours). The I261PG Pirani Gauge should read slightly above atmospheric pressure (due to the dry N2 flow pumped to the chamber). The window VENT STATUS in PanelMate should display “VENT VALVE OPEN”. The window PUMPDOWN STATUS should display “PUMPDOWN STOPPED”
