[Sbs_gems] [Revised Logentry] Access for INFN J0 evaluation

[ewertz at jlab.org]

Logentry Text:
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Got called for a brief escorted access to take a look at INFN J0 GEM. Got approval from RadCon to briefly enter the radiation area under the front of the BB spectrometer. My main points of interest were to evaluate the gas line and to try and see if there was any clear indicator near the HV dividers. I was unable to get onto the BigBite platform near the GEMs, so I tried my best to make an assessment from the ground. The gas line for INFN J0 is connected at the detector and the gas distribution panel, there was also no impediment to the output line for the gas. It did not seem like there were any issues with the gas line going from the distribution panel to the detector, but I was not able to evaluate every piece of the tube. I tried to get a good look at the HV dividers from underneath, not an easy task as there are some coverings in the way. From the ground it did not seem like there were any clear indications that the area near the HV dividers had been tampered with or da!
 maged. Ideally, and if able, one would want to get next to the detector and more closely evaluate the HV dividers. Probably before any sort of swap occurs, but this can of course be done at a later time. I will post a follow-up entry with the pictures I took. At this point there is no clear indication of what suddenly caused these problems for the middle and bottom modules of INFN J0, other than beam-on conditions.

Moving forward, we will plan to do a check of the HV to a couple hundred volts when there is some downtime and we are not collecting production data. We will also develop a plan to swap this layer and hopefully better understand what happened to J0. We will also coordinate removal of both INFN J0 and J2 from Hall A.



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