GlueX Start Counter Meeting, November 17, 2011

From GlueXWiki
Jump to: navigation, search

GlueX Start Counter Meeting
Thursday, November 17, 2011 10 am EST
JLab: CEBAF Center, Room F326/7


  1. Announcements
  2. Review minutes from previous meeting
  3. Prototype Report
  4. SiPM configuration
  5. Contract Status
  6. Simulation Status [1]

Communication Information

Video Conferencing


Talks can be deposited in the directory /group/halld/www/halldweb/html/talks/2011-4Q on the JLab CUE. This directory is accessible from the web at . You have to be a member of the "halld" Unix group to put files in this directory.



  • FIU: Lei Guo, Puneet Khetarpal
  • JLab: Eugene Chudakov, Chuck Hutton, Mark Ito (chair), Tim Whitlatch

Prototype Report

Lei reports that they got the scintillators back from Plastic Craft after re-polishing. Three of them came back badly crazed. One was OK. He says they made two mistakes:

  1. They ignored the recommendation to only use isopropyl alcohol to clean the surfaces. Instead they used a solution of isopropyl alcohol and naphtha. The naphtha is petroleum based and attacked the scintillator surface.
  2. They processed the counters in the following order: bend, machine, then polish. Preferred is: machine, polish, then bend.

Plastic Craft has agreed to replace the scintillator and will try again with the new pieces. They will place an order with Eljen.

FIU will test the undamaged piece. Its surface quality seems to have improved after re-polishing.

SiPM configuration

Puneet reported that Werner has given it some thought and is considering a 1x4 or 1x5 array of 3 mm×3 mm devices. He is thinking of using these in a 30-paddle arrangement.

We need to find out what is available from Hamamatsu. It is looking like the geometry will be driven by how we arrange the SiPM's, with a scintillator/light-guide geometry constrained by that arrangement. It would be preferable to have flat light guides with no bend.

Simulation Status

Puneet showed further progress understanding the output of the start counter hits in the Monte Carlo. See his slides for details. He generated γp to nπ+π+π events, and from those showed single particle energy and direction distributions and hit location distributions. The latter revealed an overlap of the scattering chamber with the nose section of the start counter in the default geometry. He has also looked a deposited energy and detection time. The start counter geometry used has 24 paddles.

The drawings and Monte Carlo need to be updated. Sashca Somov may be able to help with the Monte Carlo.

There seems to be some feature in the hit location distribution in the barrel section. Puneet will run more statistics to see what is going on there.

Puneet and Werner are also working on rate and radiation dose studies using GEANT4

Action Items

  1. Test re-polished counter. -> Eric Pooser
  2. Research different SiPM arrangements from Hamamatsu. -> Mark, Werner
  3. Update drawings of target/start-counter region. -> Tim, Chuck
  4. Update Monte Carlo geometry. -> Puneet, Sascha