For emergency measures,

• close GV_ixa around 8:30, and GV_exa around 8:50 (Miyoki)
• GV between the main duct and the T tube for the pumping unit was closed (Kimura-san, M.Takahashi-san)

At X-27, TMP was found to stop, while the dry pump was working, in spite of the TMP interlock system. The reason for the accidental stop was still unknown. Actually, this TMP has several time malfunctions in the past. Kimura-san contacted the Edwards staff and they will come on Monday to take a log. 

Fig.1 shows the vacuum level changes around the accident.

• EXA reached 7x10^-5 Pa. Duct shield temps in IXC were around 160K - 210K. So water absorption was partially happened on the duct shields and cold heads of cryocoolers for the duct shields.
• X-27 vacuum level reached 10^-3 Pa. After closing GV between the main duct and the T tube, the shown value does not show the actual vacuum level in the X-arm. be careful, please.
• X-15 vacuum level reached 2x10^-5 Pa. Around 12:00, 5x10^-6 Pa that should be 1.2x10^-6 Pa before the accident.
• IXA shows a vacuum level increase from 4 to 4.2 10^-6 Pa with "a delay of 3 hours". But I cannot judge weather this is due to today's accident or not because IXA vacuum level is now increasing by 0.5x10^-7 Pa for 1 month (Fig.2).

>Actually, the IXA vacuum level is now 4.2x10^-4 Pa.

Probably, 4.2×10^-6 Pa.
An order of 10^-4 Pa is too bad vacuum level.

Around 13:30, X-2 vacuum level was 2x10^-6 Pa by the Kimura-san eyeball check. Before this accident and closing GV_ixa( the data on Tuesday for the weekly maintenance), the vacuum level was 3.6x10^-6 Pa!

Actually, the IXA vacuum level is now 4.2x10^-6 Pa. This means that IXA/(IXC side) itself is now a rather outgas source and the arms side has a function to reduce this level.

So today's accident seems not to affect on IXC/IXA area. Rather, it might be better to open GV_ixa to obtain a better vacuum level.

Sorry, I corrected it.

We opened the GV_ixa around 15:20 because the closing condition was verified to enhance the vacuum level at IXA by ~ 10%. On the other hand, we should wait until the next morning to open the GV_exa because the X-27 vacuum level is 4 time worse than that before this accident.

----

Sept 28th around 15:00

  GV_ixa Close
  Total press. 6.4 x 10^-6 Pa
  H2O 1.6 x10^-6 Pa

Sept 28th around 15:20
  GV_ixa Open
  Total press.5.85 x 10^-6 Pa
  H2O 1.45 x10^-6 Pa

Sept 28th 04:36 (just before this accident)
  Total press.5.85 x 10^-6 Pa
  H2O 1.43 x10^-6 Pa

Operation record of the gate valve at X-27 (September 28)
First, the turbomolecular pump at site X-27 was confirmed to be in steady state.
At this time, the gate valve between the turbomolecular pump and the T-shape tube was "Open"
and the gate valve between the X-arm duct and the T-shape tube was "Close".
The pressure in the T-shape tube was 1.5 x 10^-6 Pa.
At 13:41, the gate valve between the X-arm duct and the T-shape tube was opened.
Next, the gate valve between the turbo molecular pump and the T-shape tube was then closed.
The pressure gauge reading changed from 1.5 x 10^-6 Pa to 6.1 x 10^-6 Pa.