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Kondo (chair); Alexander, Bob, Craig, Marcus, Martin
Next EIC Detector R&D Committee Meeting
- Participants exchanged opinions about the snowstorm, which plagued US East coast last week.
- Then we started discussing the presentation at the meeting in January 2018. Kondo expects they will give us 30 minutes for the presentation. Draft slides provided by the groups (maximum of 5 slides per group) are discussed for the rest of the meeting.
Slides from BNL (Bob)
- slide#1: Bob reminds us the X-ray scan results comparison between old and new Somacis zigzag PCBs. He shows correlation plots and residuals. In general the new PCB results look much better. DNL is smaller, the neighbouring strips have better overlap, amount of single hit events is small.
- slide#2: BNL is moving forward with the PCB design. Will use laser ablation process, which allows one to go down to ~1mil strip-to-strip distances (compared to ~3mil with the chemical etching). They are ordering the multi-pattern board with several zigzag geometries in one go (100 1cm^2 regions). The idea behind this is to scan the parameter space experimentally and pick up the best configuration. They hope to have the board ready for the March test beam at FNAL. Otherwise will test the old Somacis zigzag board, which have never been installed in the beam so far.
- slide#3: Bob mentions BNL work on the TPC prototype. The design is completed. They are planning to try out various gas mixtures and be ready to study the prototype at FNAL in July. 4-layer cosmic ray telescope is almost complete. It will feature COMPASS XY-readout with the expected spatial resolution of ~60um per layer in 2D.
- slide#4: The new X-ray scanner with a more powerful (40W vs 3W) gun is installed. It has a travel of 15" in XY (compared to 6" before). The actual rate however is smaller than expected because of the absorption in the exit window material. They are going to explore curved diffractive crystal optics to somewhat circumvent this.
- slide#5: Future plans - proceed with the laser etching, perform beam tests, make use of the cosmic ray stand, investigate TPC gas mixtures.
- Craig asks about communication with Stony Brook guys concerning the TPC prototype work (readout pad design in particular). Bob says there was no follow up to the conversation we had with Klaus last month.
- Craig asks how realistic would the July beam test be for the other groups. Kondo replies that for UVa and FIT groups the participation in this test run is definitive, and the more groups join the better. Marcus reminds everybody that they count on BNL for providing the cosmic ray telescope as a reference tracker. Craig asks whether one could use the TPC prototype or the FTBF silicon tracker for these purposes. Marcus replies that they are testing large area chambers, which requires large travel. Kondo also mentions that silicon telescope synchronization has proven to be a problem, so the second tracker system is probably not an option. Martin points out that the second tracker is needed anyway. Kondo replies that this second tracker will be read out by the same SRS electronics, which simplifies things (the idea is to integrate the cosmic ray tracker in the UVa DAQ).
- Marcus suggests Bob to add zigzag concept introduction to the slides. Bob agrees it is a good idea.
Slides from FIT (Marcus)
- slide#1: Marcus reminds us that FIT is building a large trapezoidal prototype, similar to CMS modules. No spacers, no PCB, 3/1/2/1 mm spacing, zigzag strips with electronics on the wide end.
- slide#2: Test assembly pictures: pull-out ports, carbon fiber frame. The new feature is that part of the assembly is 3D printed.
- slide#3: Picture of the kapton foils glued onto the frames.
- slide#4: Marcus shows the estimated radiation length budget. There is a factor of ~7 reduction with the new design, compared to CMS modules (~0.6% vs >4% per module).
- slide#5: Future plans - finalize the assembly, bring the prototype to FNAL in July, perform the simulations (send student to BNL some time in May-July). Marcus mentions that there is a significant slowdown in the FIT activities since Aiwu left the group.
Slides from UVa (Kondo)
- slide#1: Kondo reminds us that UVa works on a large GEM prototype with the design much different compared to the FIT one. They received UV-foils and zebra-style connector parts (?) and designed high cost (with spacers; external company) and low cost (without spacers; UVa production) frames.
- slide#2: Pictures with optical and SEM inspection results of the Cr-GEM foils. Kondo says that the recent work with Bernd and Matt at Temple was hampered by a fact that outer hole diameter could not be measured reliably (not enough reflection from Cromium, so no contrast). Optical inspection reveals that even the good foils have a second peak in the pitch distribution (although the inner hole diameter itself looks fine). Several foils were sent to CERN for the SEM inspection. One obvious outcome was that the Cromium thickness on the foils is 200nm rather than 100nm as it was expected (not that it really matters for the overall material budget).
- slide#3: SEM pictures of a foil damaged after the high rate test show that the bottom side Cr layer is almost gone while there is no apparent damage to kapton and also the top side looks good.
- slide#4: SEM technique has an interesting issue when taking images of a dielectric material (the image effectively becomes distorted in a funny way). They had to apply a conductive tape on top of the surface in order to avoid charging up effect. Kondo mentions that in view of the observed damage one may consider a "hybrid" approach for the high rate applications (remove copper from the top GEM foil surface, but leave it there on the bottom side).
- slide#5: Future planes - assembly the prototype, perform the QA, bring the prototype to FNAL in July, participate in the simulation effort (in June?). Kondo also mentions that they are working on the 10x10cm^2 2D uRWELL detector prototype and started writing the Cr-GEM paper (to be submitted to either NIM or TNS later this year).
- Marcus notices that UVa design is still using spacers while FIT one is focused on removing everything from the active area. Kondo also confirms that in one of the designs the frames are made of pieces (in order to save on the material costs).
- Concerning the presentation, Marcus suggests that one can spend less time on slide#4 and concentrate on more important slide#5.
- Alexander asks how does Kondo arrange the SEM inspection of the foils. Kondo says this was done through the personal contact at CERN who submitted the request to the respective CERN department on their behalf.
- Kondo suggests to have the next Monday meeting for a practise talk. He also says Thomas Ullrich gives us 5 more minutes on the agenda to address the critique made by Silvia.
- Marcus says that his student (Matt) is going to visit BNL for as long as 2 weeks (if needed), some time in May-June. In reply to the Alexander's question he agrees that it would be very reasonable to communicate with both UVa and FIT students "in sync" on the simulations.
- Kondo suggests to Bob that one can improve APV25 performance by using the non-trivial configuration settings. In particular it turns out that setting the largest dynamic range is not necessarily the best way to avoid saturation. The subject it then taken offline.
- Marcus suggests that we may want to change the meeting time in order to better accommodate the Stony Brook people schedules. Martin however says that this time it was a one-time conflict. Kondo will still try to check other time slots for the meeting.
- The meeting adjourns