Mar 17, 2011 Calorimetry
From GlueXWiki
Teleconference Time: 11:00 a.m. EST
- ESNET (Number is 8542553) and EVO session (GlueX Calorimetry meeting room)
- JLab Phone: in CC F326 is 757-269-6337
- Regina Phone: in LB228 is 306-585-4204
- Athens Phone: in Christina's office is 011-30-210-727-6947
- Phone connection only upon request.
- +1-866-740-1260 : US+Canada
- +1-303-248-0285 : International
- then enter participant code: 3421244# (remember the "#").
- or www.readytalk.com (and code without the #)
Items for followup from previous meeting(s)
- Monitoring
- Fcal: check cross talk of calibration inputs across modules.
- Fcal construction
-
JLab to provide shipping guidelines to Matt
-
Tentative Agenda
- Announcements
- Starting next week, we will move the Bcal Readout meeting and Cal Working Group meetings to TUESDAY 11:00
- Review of Action Items
- Calibration
- BCAL
- Construction Status: builds, fibre QA
- First article testing (Yi) Result Page
- FCAL
- Construction Status: mechanical, bases - no report
- Drawings for Fcal structure (Tim) Sketches for comments on FCAL structure
- Simulations
- Readout segmentation (Andrei)
Minutes
Attending:Elton, Yi, Eugene, David, Tim, Beni, John (JLab); Zisis, Andrei (UofR); Will (USM); Christina (Athens),
- Announcements
- Starting next week, we will move the Bcal Readout meeting and Cal Working Group meetings to TUESDAY 11:00
- Review of Action Items
- Calibration
- Concept for Fcal settled
- Discussions on Bcal option underway
- Will present concept to this group at next meeting (Mar 29)
- Modifications include daisy-chaining LED boards together
- Use CAN bus to communicate with control boards
- Consideration for optimum placement of LED boards on detector, including possibly attaching 2 fibers to each LED
- UofR will come up with some sketches that can be passed on to our designers to verify geometry
- BCAL
- Construction Status: builds, fibre QA
- Construction proceeding well. Modules 33 and 34 are about 30-40% complete.
- Machining of Module 26 started Mar 15. Start delayed to allow large job from Alabama to be completed at Ross Machining.
- Schedule for shipping will be updated once two modules are finished. Expect two shipments, one at the beginning of April, one at the end.
- In view of the disaster in Japan, they have assessed the inventory of fibers. They have in hand 10 weeks of fibers in stock.
- First article testing (Yi) Result Page
- Received 80 first-article samples from Hamamatsu last Wed.
- To date 25 units have been tested, but results are still under evaluation
- Test use a calibrated LED and five light settings using a neutral density filter.
- Gain measurements are relative, absolute calibration not yet completed.
- Rates normalized to 25deg C (where Hamamatsu specifies the units). Dark rates are about 16 MHz/array, about 4 times lower than original samples. Eugene would like to know what has changed in the fabrication process.
- Tim: Have any dimensional checks been made?
- Zisis: Suggest that Yi add quick progress checklist on the wiki for easy reference of measurement status.
- Construction Status: builds, fibre QA
- FCAL
- Construction Status: mechanical, bases - no report
- Drawings for Fcal structure (Tim) Sketches for comments on FCAL structure
- Following the last meeting, Tim, Wayne, Matt and John met to go over details
- Decision to stiffen support structure. Tim and Wayne have had discussions with designers of the support frame for the JLab Big-Cal support structure, who provided feedback to our concept
- IU will build a prototype to test the layout with two rows of 20 bars, which will take 4 weeks.
- Fabrication of parts will follow after incorporating feedback from the prototype.
- Simulations
- Readout segmentation (Andrei)
- Study of energy resolution for different configurations, dividing the impact on the BCAL into upstream, middle and downstream.
- Use tagged version with fixes that Matt has made for including background. Some of the fixes do affect conclusions of results shown previously
- Tagged version assumes a occupancy fraction of 5%. To account for lower number of channels, Andrei has studied the resolution with 10% occupancy as well.
- Comparison of resolution between no summing and nominal summing scheme. Main difference shows the resolution degradation for large photon angles. Energy resolution at the center of the calorimeter and downstream are similar with and without summing.
- Study of a comparison between 2x2 outer and 4x1 outer segmentation. No difference found, confirming earlier result by IU.
- Energy resolution results depend critically on the implementation of noise into the software.
- (As seen in the previous report) the mean value of the reconstructed energy is systematically lower than the generated energy. The change in fractional energy depends on energy and location of impact on the detector. Any (empirical) compensation for this effect would be z and E dependent.
- Computing the energy resolution relative to the measured value, increases the stochastic term by about 1%.
- Beni: Is the bump at low energy understood? Andrei: No, except it may be correlated with the systematic shifts in energy, which are more pronounced at low energy
- Eugene: What is the efficiency for reconstruction, and is the bump at low energy a result of decreased efficiency? Andrei: Unclear at this point. He thought that the efficiency for high energy photons was between 50 and 70%. This seems to be inconsistent with the amount of material expected between the target and the BCAL.
- Eugene: Need to study the efficiency, as this parameter may be more important than resolution.
- David: Asked about usage of summing units in the software: Andrei promised to send instructions and configuration files.
- Will: Notice importance of noise to resolution. Can one optimize the BCAL by carefully placing SiPMs in the detector based on their dark rate? (Could be useful, especially if arrays show large differences in dark rate).
- Readout segmentation (Andrei)
