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[Xu Sun <sunxuhit AT gmail.com>]

Hi Flemming,

The bias voltage is different in two tests.

For the test on 08/11/2021, the bias voltage is 50V for both inner and outer. This is because the detector is only half way in and we couldn't block the light.

For the test on 08/17/2021, the bias voltage is 140V for inner and 160V for outer.

Best,

Xu

On Tue, Aug 17, 2021 at 7:34 PM videbaek <videbaek AT bnl.gov> wrote:

Hi Xu,

a question were the bias voltage the same in the two tests or did you go
to 140 for the outer. Just want to make sure I understand what you did.
I am coming in to the lab tomorrow as already planned and will see you
in the hall

flemming

On 2021-08-17 19:11, Xu Sun wrote:
> Hi All,
>
> We ramped the whole FST detector to the working HV last night and did
> a readout test for all the modules.
> There are two modules located at Disk 1 position 7 and Disk 1 position
> 11 (all belong to RDO2) showing an abnormal noise than the previous
> test. The RO test results can be found in the attached file
> (RDO2_140V_08172021.png).
>
> Both modules 1-7 and 1-11 were tested with 50V while the FST was half
> way in the cone on 08/11/2021. The results then were quite normal and
> could be found in the attached file (RDO2_50V_08112021.png).
> The only difference between two tests, as far as we are aware, is the
> position of the detector: on 08/11/2021 detector was half way in the
> cone and on 08/17/2021 detector was at final position.
> We have made sure the issue is on the purple cable and module side by
> swapping connections through the readout chain.
> Similar problems were found in the clean room RO test and were fixed
> by adding grounding to the aluminum ring or replacing the purple
> cable.
>
> We plan to pull the FST out tomorrow morning and check what happened.
> We also plan to add additional grounding of 1-7 and 1-11 to the
> aluminum ring instead of  only grounding to the T-board since it is
> almost impossible to change the purple cable for Disk 1 (most inner
> disk) on the scaffolding.
>
> Best,
>
> Xu
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--
Flemming Videbaek
senior scientist
videbaek @ bnl.gov
Brookhaven National Lab
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