Oct 22, 2009 Readout

Teleconference Time: 11:00 a.m. EST

• ESNET and EVO session
• Phone:
  • +1-800-377-8846 : US
  • +1-888-276-7715 : Canada
  • +1-302-709-8424 : International
  • then enter participant code: 77438230# (remember the "#"). Phone connection only upon request.

Items for followup from previous meeting

1. Ship Baby Bcal to USM.
2. Alam (Pedro) to post files for new geometry of light guides.

Documents to Review

1. Media:Draw trigs 38deg.pdf Media:Draw trigs 73deg.pdf for segment #2.
   • Entrance rectangle is 3.01x4.0 cm. Exit radius is 1.35 cm. Length of trapezoid/cone is 60 cm, and length of torus is also 60 cm.
   • This configuration should be comparable to Alam's "cylindrical cone" geometry.
2. See also Effective diameter vs B field and angle from Antonelli et al., NIMA 368 (1996) 628-634.
3. Magnetic field plots
   • Media:Plot bfield tot downstream.png
   • Media:Plot bfield theta downstream.png
   • Media:Plot bfield tot upstream.png
   • Media:Plot bfield theta upstream.png
4. Light guide prototypes. See Quote from Plastic Craft and Ray tracing through light guides

Tentative Agenda

1. Announcements
2. Review of Action Items
3. Plan for SiPM Testing (Carl and Fernando)
4. USM report
5. Light Guide Geometry
6. Light Guide Simulations
7. Discussions on MOU with USM

Minutes

Attending: Elton, Beni, John, Tim, Sascha, Fernando, Eugene (JLab); Zisis, Andrei (UofR); Will, Alam (USM)

1. Announcements
2. Review of Action Items
   • Alam sent an e-mail this morning to Zisis and Will indicating that payment has been made for the shipment of the Baby Bcal. Zisis will check on the shipment itself and send an e-mail confirmation.
3. Plan for SiPM Testing (Carl and Fernando)
   • Fernando has assembled boards for the Hamamatsu units and has taken a first look at output signals.
   • Using a 5 ns LED (1ns rise time), SiPM output has a rise time of about 15 ns and total length of 90 ns. Bias voltage is set according to Hamamatsu corresponding to a gain of 7.5x10^5 (about 70.5 V for this SiPM).
   • Fernando will distribute a brief report by tomorrow on initial look at the Hamamatsu sensors.
   • Elton reported that Carl Jackson from SensL communicated that they believe they have fixed their packaging problem and will have units to verify the new process by today. After confirming the fix to the problem, they will send us a schedule for the 10 units that were ordered.
   • Carl is traveling to the IEEE conference next week and will meet with Hamamatsu and SensL representatives, and report on preliminary look at the Hamamatsu units.
   • Eugene: One test that should be included in the plan is to use two independent LED pulsers and check the linearity of response when they come close together in time.
4. USM report
   • None, beyond progress on shipping the Baby Bcal
5. Light Guide Geometry
   • The mechanical design from Pedro was read into the Hall D detector model. It was discovered that he was using the sizes for the Bcal before machining (unclear why this file was provided initially). This changes some of the dimensions.
   • In the meantime, Chuck (Hutton) here at JLab is making a drawing of a "typical" light guide which could be used to test light guide prototypes. The light guide chosen was segment #8, with dimensions similar to the ones in Pedro's model, but adjusted to actual dimensions.
6. Light Guide Simulations
   • Elton has modeled this "typical" light guide and obtains an efficiency of 60% (using lambda=240cm) and 98.3% geometrical efficiency. Results of the simulations will be posted on GlueX-doc-1367 along with the other simulation plots for ease of comparison.
   • Vitaly Baturin, who is working on CLAS12 central TOF counters, has kindly simulated (using his own GUIDE7 program) a light guide with dimensions for segment 7, except that it does not have a bend. It is straight with an overall length of 120 cm (60 cm in the conical conversion of rectangle to round, and 60 cm of cylindrical pipe.
   • Vitaly gets an efficiency of 49% (lambda=240 cm), and 96% geometrical efficiency. This is to be compared with 56% of Elton's simulations (includes bending of pipe). This confirms the basic conclusion that the a) geometrical acceptance is very high, b) for typical effective attenuation lengths the efficiency is about 50% or greater and c) measuring the transmission of an actual light guide is needed to gain confidence in the acceptance for production setups.
7. Ordering prototype light guides
   • We propose to order light guides with the geometry of the "typical" #8 guide, described above. We should also order several lucite rods to check and experiment with surface treatment to study reflection losses. May wish to split shipment of prototypes for tests at JLab and USM.
   • USM is also investigating sources of pure acrylic in Chile, as well as investigating possible collaboration with the USM Chemistry department.
8. Discussions on MOU with USM