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[Xu Sun <sunxuhit AT gmail.com>]

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

Attachment: RDO2_50V_08112021.png
Description: PNG image

Attachment: RDO2_140V_08172021.png
Description: PNG image