Sep 29, 2008 Calorimetry
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Items for followup from Sep 2 calibration meeting
- Each subsystem must complete blanks in the Specification Table.
Items for followup from Sep 15 meeting
- George: report on trip to Edmonton
- Decision on Bcal sampling fraction needed by Sep. - Initial work by Stamatis was reported
- Resolution studies (Blake)
- Up-to-date geometry ONGOING.
- Decreased threshold for FM pmts. ONGOING
- Position resolution - understand dependence on granularity.
- Different segmentation for the outer section. - LOWER PRIORITY
- Study impact of inactive material at the end of Bcal on acceptance.
- Add F100 rad hard glass to simulation. - New graduate student has been assigned this project.
Documents to Review
- From Will Brooks: http://www.jlab.org/Hall-D/software/wiki/images/0/0c/Geometry_effect_timing.pdf
- Update on VLPCs (Werner) 
- Results on study of increased sampling in BCAL
- Systematics in Bcal timing (Will)
- Update on VLPCs (Werner)
- Decision on cell for SiPM arrays. The proposal is to use the A20HD Getter#1 devices in the array builds.
- Trip to Edmonton
- Roadmap to decision on Bcal readout e-mail
Attending: JLab: Elton, Beni, Elke; Athens: Christina; UofR: Zisis, George, Andrei, Stamatis; Santa Maria: Will, Sergei; FIU: Werner; IU: Matt, Mihajlo, Claire, Ryan
- Calibration (Christine)
- Constructing box to shield laser from RF noise to check stability of laser
- Looking to purchase more LEDs. The LED they are using does not presently give sufficent light.
- All groups are encouraged to fill in the Table of Specifications.
- Announcements (Elton and Elke)
- The latest news from DOE is that the 12 GeV project will not be considered a 'new start' under a continous resolution. This could allow placing orders for construction early in the fiscal year. However, budgets are still constrained by the 2008 ped funding profile.
- Increased sampling fraction (Zisis)
- Simulations are continuing. For thin lead sheets the energy resolution blows up.
- Hybrid solution results in non-uniformities and is discouraged as a general rule. Also complicates calibration. At the moment the simulation program does not lend itself directly to this option (Matt).
- Bcal timing and geometrical effects (Will)
- Study implications of timing resolution in a toy model, Look at position dependent changes in mean time as a function of position. Assumes low TDC thresholds.
- For charged particles and showers, RMS ~ 240/sqrt(12) = 80 ps. This dispersion migh in principle lend itself to software corrections for accurate modeling.
- For neutrons, RMS ~ 70 ps, intrinsic due to the unknown neutron interaction position. Distinguishing photons from neutrons is important especially for nuclear targets.
- Matt: mentioned that the resolution deltaZ which is required decreases at large Z for a fixed resolution in the polar angle. See, for example, Hall-B Collimators and Flux.
- Visible Light Photon Counters (VLPCs) (Werner)
- An old subject revisited. Current plans are for D0 to run till 2010, after which their VLPCs might become available to other DOE projects. Hall A is currently considering this as an option for a fiber tracker for polarimetry.
- Werner reviewed the characteristics of the VLPCs. They currently instrument about 100k channels. The active area is about 1mm2, coupled to 0.8 mm diameter green fibers, and very high quantum efficiency.
- Coupling to individual fibers in the Bcal would require about 800k channels.
- The start counter might be considered for such a readout.
- After a brief discussion, the proposal for using the A20H 3x3 mm2 Getter#1 devices was adopted. Elton would relay the information to SensL.
- There is a planned one full day meeting at Edmonton on Wed Oct 15 (U. of Alberta) to review construction plans for the Bcal. JLab (Elton, Elke and Tim), UofR (Zisis and George) have made travel arrangements. The tentative plan is to meet for dinner on Tuesday to prepare for meetings the following day.
- A detailed construction schedule continues to be developed, and a new iteration will be passed around.
- Fcal update (Matt)
- Timing studies continue and a few bugs have been discovered and data is being understood.
- Mijahlo has a short talk at the APS meeting, will give a dry run at the next working group meeting.
- Elke: updates to the construction schedule of order 6-9 months are being considered and will be passed on to Matt.