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Remote Handling plus support groups are currently attempting to install and commission indium vacuum seals into the following M20 front-end joints:
- T2/Q1
- Q2/Scraper
- Scraper/T2
The first indium joint installed was at T2/Q1 during the week of May 14 to 18. Rubber seals were installed at the other two joints. The system was leak checked on Tuesday May 22 and a suspect leak response was detected.
The details of the installation and the leak check are in the attached .pdf e-mail dated 23 May 2012.
Today (Thursday 24 May 2012) the T2 volume and M20 front-end vacuum system were leaked checked with rubber seals in all aforementioned joints by RH group and Vacuum Group. The results are listed below:
The test equipment consisted of a long Remote Handling pole with a copper helium applicator line attached to the end, joined to a long plastic line extending up the pole to the RH operator above.
The plastic line was kinked with a zip-tie to cut off the flow. To engage the flow for each test, the zip-tie was removed and the kink was opened.
This would result in a burst of helium of a pressure you could feel easily on your face for approximately ~1s followed by a steady, very low flow just detectable on the cheek / tounge.
The Varian Leak Detector was used attached by Vacuum Group to the T2 and M20 front end volume. Edi Dalla Valle monitored the leak detector and communicated to Ron Kuramoto via headset radio.
The test started at 11:15 am, 1ACG4 20mT, 1AVA8 closed.
1) M20 Beam Blocker Top Flange (Top of T2 Monument)
11:15 am
Base leak rate 1.5 x 10-8 atmcc/sec
10 second spray of helium
No response after 2 min.
2) M8 T2 Blank-Off Flange
11:30 am
Base leak rate 1.5 x 10-8 atmcc/sec
5 second spray
First reponse after 30 seconds
Peak at 2 minutes, 4.1x10-8 atmcc/sec
3) M20 Q1/T2 Flange Top-Dead-Center
Base rate 1.7x10-8 atmcc/sec
5 second spray
First response after 40 seconds
After 60 seconds, 2.5x10-8 atmcc/sec
Peak at 2 minutes, 3.3x10-8 atmcc/sec
Recovery beginning after 2.5 minutes
4) M20 Q1/T2 Flange Bottom-Dead-Center
Base rate 1.7x10-8 atmcc/sec
5 second spray
First response at 45 seconds
Peak at 3 minutes 3.0x10-8 atmcc/sec
*1ACG4 read 16 mTorr at 11:55 am
5) M9 Q1/T2 Flange Top-Dead-Center
Base rate 1.6x10-8 atmcc/sec
5 second spray
No response after 3 minutes
6) Downstream T2 / 1AQ14 (Collimator B Area, see attached photo of Ron Kuramoto applying helium at this area)
Base rate 1.5x10-8 atmcc/sec
5 second spray
First response after 10 seconds
3.3x10-8 atmcc/sec at 1 minute
Peak at 1m 45 sec 3.6x10-8 atmcc/sec
7) M20 Q2/Scraper
Base rate 1.6x10-8 atmcc/sec
5 second spray
First response after 2 minutes 1.7x10-8 atmcc/sec
Peak at 2.5 minutes 1.8x10-8 atmcc/sec
This leak check confirmed suspicions of helium drift to the known leak at T2 / 1AQ14 joint on the T2 monument.
The delayed leak response seen on May 22nd at M20 T2/Q1 is very likely drift of helium to this known leak based on these measurements, and not an actual leak at T2/Q1.
Edi Dalla Valle re-confirmed these leak check results with standard remote helium line tests. His notes for these tests are scanned and attached.
We will proceed tomorrow to make up the T2/Q1 joint with the same ring and pin combination as used May 17 to May 22 2012.
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