[Halld-pid] Minutes, GlueX Start Counter Meeting, November 17, 2011

[Mark M. Ito]

Folks,

Find the minutes at 
https://halldweb1.jlab.org/wiki/index.php/GlueX_Start_Counter_Meeting,_November_17,_2011 
and below as text.

-- Mark
______

GlueX Start Counter Meeting, November 17, 2011

Minutes

Present:
* 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 [29]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

Retrieved from
"https://halldweb1.jlab.org/wiki/index.php/GlueX_Start_Counter_Meeting,_November_17,_2011"

References

29. 
https://halldweb1.jlab.org/talks/2011-4Q/start_counter/khetarpal_sc_hdgeant2.pdf