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Entry  Wed May 12 15:43:30 2021, Aidan, Summary, 2um Photodiodes, Chamber is leaking 
    Reply  Wed May 26 18:38:25 2021, Aidan, Summary, 2um Photodiodes, Chamber is leaking 
       Reply  Fri Jun 11 07:42:54 2021, Stephen, Summary, 2um Photodiodes, Chamber is leaking IMG_8865.JPGIMG_8881.JPG
          Reply  Fri Jun 11 16:48:31 2021, Aidan, Stephen, Summary, 2um Photodiodes, Chamber is leaking IMG_3002.jpgIMG_3001.jpg
Message ID: 2578     Entry time: Wed May 26 18:38:25 2021     In reply to: 2568     Reply to this: 2586
Author: Aidan 
Type: Summary 
Category: 2um Photodiodes 
Subject: Chamber is leaking 

I tried Krytox around the O-ring and also tightening the screws around the valve. The leaking persists at roughly the same rate.

Quote:

I tried pumping down the JPL PD chamber to test the new PD at cryo temperatures. Unfortunately, the chamber can;t get past about 6E-3 Torr with the pump on. As soon as I turned off the pump the pressure rose to around 2 Torr over 20 minutes or so.

I extricated the chamber from the pedestals, flipped it and removed the bottom plate. I cleaned the O-ring with isopropanol and wiped down the mating surface on the chamber (also with iso). I replaced the plate and tightened the screws. Then I returned the chamber to the table and reconnected it to the vacuum system. I tried pumping down once again but I saw pretty much exactly the same situation as before (pressure bottoming out around 6E-3 Torr and then rising quickly again when the pump was turned off).

I guess it's possible that the O-ring is damaged - although I couldn't see anything obivous. We didn't mess around with the viewport (when we replaced the diode a few weeks ago) so I'm hoping there is no issue there.

 

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