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["Visser, Gerard" <gvisser AT indiana.edu>]

I think it is more likely that something deposited on there that we don't know about, than that radiation damage could cause visible macroscopic "rings" in certain places.

There's probably no point worrying about what it was though. I have no theories.

      Gerard

---

From: Star-fst-l <star-fst-l-bounces AT lists.bnl.gov> on behalf of Videbaek, Christian <cvidebaek AT bnl.gov>
Sent: Tuesday, May 31, 2022 11:24 AM
To: Ye, Zhenyu <yezhenyu AT uic.edu>
Cc: Star-fst L <star-fst-l AT lists.bnl.gov>
Subject: Re: [Star-fst-l] STAR FST Meeting May 30 8:30am EDT

 

Hey Zhenyu, Gerard,

Re: Thermal paste:
I was able to get a close look at the junction between the sensors and the cooling system and saw that there was an unbroken strip of thermal paste between the two.

Thermal paste is clingy stuff after it is heated, there would have been a visible seam if enough had run out to leave gaps between the components.

Re: Temperature readings:
Each T-board has a temperature sensor and the data from it is logged in the online status viewer.

Should one FEE have badly compromised cooling the corresponding T-board would (eventually) have gotten significantly warmer than the others.

I don't recall seeing this on any of the online plots.

Re: Possible radiation damage:

The rings appear to be perfectly flat and are about as reflective as the surrounding material.

Had some other material been deposited on the sensor it should look different.

Additionally, the IST sensors were mounted in such a way that nothing could have fallen on them.

I'm not sure what else could cause these features to appear.

I suppose it could be a cosmetic manufacturing defect, but why would it only appear after the run?

Christian

---

From: Ye, Zhenyu <yezhenyu AT uic.edu>
Sent: Tuesday, May 31, 2022 9:34 AM
To: Videbaek, Christian <cvidebaek AT bnl.gov>
Cc: Aschenauer, Elke <elke AT bnl.gov>; Star-fst L <star-fst-l AT lists.bnl.gov>
Subject: Re: [Star-fst-l] STAR FST Meeting May 30 8:30am EDT

 

Hi Christian

Thanks for the summary. Some of the info was also presented by Xu/Ziyue/Gavin at the previous meetings and the meeting yesterday, to which I have no question, except two

"There is enough thermal paste under the 12:00 and 3:00 heatsinks that no more needs to be added
These sensors do not exhibit unusual behavior, and the temperature sensors read higher than the others" 

-> How is the conclusion “… enough …” reached?

-> What is the evidence to support “…higher than the others … "

"The ring-shaped imperfections on the sensor surface are caused by radiation”

-> How is this conclusion made? 

-> Xu, can you check whether these channels behave differently in readout?

I agree with the plan to insert the FST back into the TPC cone now. After that we will check on readout and cooling to make sure there was no problem introduced.

P.S. for those who have not had a chance, you may find the slides by Te-Chuan presented at yesterday’s meeting useful:

https://drupal.star.bnl.gov/STAR/event/2022/05/30/STAR-Forward-Silicon-Tracker-Meeting/Shutdown-Report-0

Zhenyu

On May 31, 2022, at 7:22 AM, Videbaek, Christian <cvidebaek AT bnl.gov> wrote:

Hi Zhenyu,

I don't think we need to do anything about the thermal paste on the FST:

-The leak probably happened at the beginning of the last run, and didn't do any harm over the following weeks

-Thermal paste/grease is difficult to remove, even with solvents

The chance of spreading it around or damaging something while cleaning is too great to risk

We concluded the following after the inspection on Thursday:
-The streaks on the 6:00 sensor are thermal paste which dripped down the face of the 12:00 sensor

-There is enough thermal paste under the 12:00 and 3:00 heatsinks that no more needs to be added

These sensors do not exhibit unusual behavior, and the temperature sensors read higher than the others

-The ring-shaped imperfections on the sensor surface are caused by radiation

Similar structures can be seen on the IST sensors in the clean room

Additionally, Xu and Gavin tightened the heatsink screws on the modules which had leaked some thermal paste.

This should compensate for any lost material.

Would you like any additional information?

Christian

---

From: Star-fst-l <star-fst-l-bounces AT lists.bnl.gov> on behalf of Aschenauer Elke-Caroline <elke AT bnl.gov>
Sent: Monday, May 30, 2022 11:08 AM
To: Ye, Zhenyu <yezhenyu AT uic.edu>
Cc: Star-fst L <star-fst-l AT lists.bnl.gov>
Subject: Re: [Star-fst-l] STAR FST Meeting May 30 8:30am EDT

 

Zhenyu,

I think you should hear from Christian, but I think holding a meeting on one of the holidays in the US, you miss of course this opportunity.

I personally think ones in a while one need to respect holidays.

I have talked to christian and we all think what ever flow out is out and the situation is stable, there is now need to do anything, becuase the question would be what to do.

So I agree with FLemming the detector should be reinserted and but in a safe condition for the rest of the shutdown.

Cheers elke

On May 29, 2022, at 22:15, Ye, Zhenyu <yezhenyu AT uic.edu> wrote:

Flemming, thanks for sharing your input. 

Before inserting FST back, I think we need to understand a bit better about thermal grease. We shall hear more from Xu/Ziyue/Gain, and from Yi/Te-Chuan/Hao tomorrow. 

Zhenyu

On May 29, 2022, at 8:35 PM, videbaek <videbaek AT bnl.gov> wrote:

Hi
I won't attend tomorrow. I think we should insert FTS after what I saw last week.

F'



On 2022-05-29 18:17, Ye, Zhenyu wrote:

Dear all
Tomorrow is a national holiday in the US, but we will still have a FST
meeting starting at the regular time (8:30am BNL local time) to
discuss the shutdown activity status and plan.
Best
Zhenyu
Agenda
https://drupal.star.bnl.gov/STAR/event/2022/05/30/STAR-Forward-Silicon-Tracker-Meeting
Zoom meeting
https://urldefense.com/v3/__https://uic.zoom.us/j/87904302955?pwd=NENEZUFxVEFoN2dzUFNJdzJPN0p0QT09__;!!P4SdNyxKAPE!BFJhwVSLXSmqQpOn-XdDOhiwQvQ91KzzE_gzIlroylpTUeFQxuG6n-PWhTdN5B0XH681NYHLBc-N6o6XMePFHATmjA$ 
Meeting ID: 879 0430 2955
Passcode: fSTAR2021
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-- 
Flemming Videbaek
senior scientist, emeritus
videbaek @ bnl.gov
Brookhaven National Lab
Physics Department
Bldg 510D
Upton, NY 11973

phone: 631-344-4106
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