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Message ID: 2691     Entry time: Wed Oct 27 10:18:33 2021
Author: Aidan, Stephen 
Type: Summary 
Category: Cryo vacuum chamber 
Subject: Inspection of Megastat post 408K event and pumping timeline 

[Aidan]

I've attached a timeline of our inspection this afternoon along with today's pumping timeline,

Here is a brief summary of observations from previous pumping timelines. Today's pump down is consistent with previously observed timelines.


 

2:17PM – Assessing the impact of the 408K event in the MegaStat

Coldhead reached 363K (90C)

Innershield reached 403K (130C)

 

2:24PM – Aquadag E service temperature (149C)

https://www.laddresearch.com/index.php/lanotattachments/download/file/id/40/store/1/

Maximum service temperature in air* : 300°F (149°C) 

*Service temperature under vacuum conditions is significantly higher. Contact Acheson for specifics. 

2:25PM – Bringing Megastat back up to air for initial inspection

2:37PM – chamber is at air

 

2:41PM – removing bolts

 

 

3:13PM – initial inspection looks normal. No elevated amount of black particulates found on surfaces – consistent with or less than the amount seen last time we opened.

Stephen detected faint smell different from last time (“campfire”?)

  • One RTD connector did delaminate Aquadag from the inner shield

3:14PM - Stephen reattaching the RTD wiring that had delaminated. I wiped up visible particulates with isoproponal soaked wipe.

 

3:21PM – putting lid back on

3:30PM – lid on. Screws in finger tight

 

3:35PM – screws tight – ready to pump

3:40PM – pumping station on

 

Time (minutes) Pressure (Torr) Notes
0 7.5E2 Pirani gauge initially
1 7.5E2  
2 7.5E2  
4 7.5E2  
5 7.5E2  
7 7.5E2  
9 7.5E2  
10 7.5E2  
11 7.5E2  
12 4.3E2 Gauge starts reading decrease
13 2.2E2  
14 9.8E1  
15 5.5E1 Turbo ON
16 2.9E1  
17 1.6E1 Turbo at 44%
18 9.4E0  
19 4.9E0  
20 1.8E0 Turbo at 58%
21 3E-2 Turbo at 70%
22 1.1E-3 ION gauge readings from here. Turbo at 91%
23 7.5E-4 Turbo at 100%
24 6.3E-4  
25 5.9E-4  
26 5.5E-4

 (Cryo-cooler normally turned on around this time)

Not in this instance though

27 5.0E-4  
28 4.59E-4  
29 4.26E-4  
30 4.05E-4  
     

 

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