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Description of the problem:

Description of the problem: Humidity levels inside the pixel volume are strongly dependent on the status of the CMS magnet. Humidity is higher with Magnet ON than with Magnet OFF. The problem is asymmetric : Minus side is affected more than the plus side.

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Description of the problem:

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  1. Description of the problem: Humidity levels inside the pixel volume are strongly dependent on the status of the CMS magnet. Humidity is higher with Magnet ON than with Magnet OFF. • The problem is asymmetric: Minus side is affected more than the plus side. • The problem is there since pixel installation • This is not an instrumentation problem. • Verified with two kind of sensors (HMX and HS2000) readout by two different PLC in two different locations. • The problem is repeatable and reversible. • With time (magnetic field cycles) it get worse • All other humidity volumes that concern the pixel have already been certified as good for running at minus 10 deg C. • This problem is the show stopper. • With the humidity of now we cannot go lower than 0 deg C.

  2. The potential source of the problem: The silicon ring that is attached to the endcap “pushes” into the Aluminum ring at the bulkhead. This is by design in order to seal the bulkhead from the UXC cavern (that comes in along the beam pipe from larger Z) The “push” opens up the seal of the pixel volume.

  3. The potential source of the problem (hypothesis) : The silicon ring that is attached to the endcap “pushes” into the Aluminum ring at the bulkhead. As of now this is the only mechanism we came up with that can open the pixel volume.

  4. The first challenge: • At the first time we open CMS we should verify if the hypothesis is correct or not. • It is unreasonable to ask for the experiment to be closed and the magnet to be ramped up just to understand this problem. • Build the tools to generate the “push” with CMS open and without the presence of the magnetic field. • This group can help on this (technical work) • These tools should be ready by November (the sooner the better) • Between now and than: • Keep scratching our head and understand if this is really the only hypothesis. • Work with the assumption that this hypothesis is correct • We should come up with potential solution/s. • Such solution/s should be tried in situ (when CMS open) • The effectiveness of the solution/s should be verified with the same tools described above.

  5. FPIX Total of 14 panels out of 192 (7.3%) is not functioning. 2 Of them not worth touching (same decision was taken in 2009) 6 of these are being recovered with special “tricks”. 6 others can be recovered with a Hardware intervention on the auxiliary electronic (far away from any wirebond) NEED TO OPEN CMS to fix this one No signal output: 1/192 (0.5%) Too Low signal amplitude (TBM): 1/192 (0.5%) Slow panels: 5/192 (2.6%) One ROC no-signal: 1/192 (0.5%) Recoverable with software effort. No I2C communication with AOH: 6/192 (3.1%) 5

  6. BPIX About 1.5% broken but scattered all over. Not worth touching in a short intervention. There is another 1% where we have a remote sensing wire that is broken but the detector is still fully efficient (tricks applied to get this parts back in shape). I would not pull BPIX out. But fixing the remote sensing wire is tempting Broken remote sensing wire. Note: the hole is artificially added being the modules are working ~fine. 7

  7. Options: • Option 1: we do not open CMS • Pros: no work, no risk, • Cons: we will be limited to run with the coolant above freezing point untill we Open CMS (this can be critical depending on the integrated luminosity). • Option 2: We open CMS but we do not pull out any part of the pixel detector • We just deal with the humidity problem • Option 3: We Open CMS we deal with humidity problem and • Perform minimum needed maintenance associated with auxiliary electronic . • Pull out FPIX PLUS only and recover the 45˚ sector on a disk. • Option 4: We Open CMS we deal with humidity problem and • Perform all needed maintenance associated with auxiliary electronic in FPIX. • Pull out FPIX PLUS only and recover the 45˚ sector on a disk. • Pull out FPIX MINUS and fix (different than workaround) the problem with the slow channels. • Option 5: We Open CMS we deal with humidity problem and • Perform all needed maintenance associated with auxiliary electronic . • Pull out FPIX PLUS only and recover the 45˚ sector on a disk. • Pull out FPIX MINUS and fix (different than workaround) the problem with the slow channels. • Pull out inner BPIX to fix (different than workaround) the remote sensing wire • Other Options (fixing single channels) likely unfeasible with the time constrains we have. 8

  8. Stop here for now

  9. Detector maintenance: Reminder: in 2009 we did not tackled single channel problems (risk was considered too high even than with only 2-3 weeks available with the detector out)

  10. Detector Status: Several scattered holes Some of them might be recovered in the next couple of months.Reminder: in 2009 we did not tackled single channel problems (risk was considered too high even than with only 2-3 weeks available with the detector out)

  11. Detector maintenance: Reminder: in 2009 we did not tackled single channel problems (risk was considered too high even than with only 2-3 weeks available with the detector out)

  12. The “push” takes place on a area full with “tape”.

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