Minites of Cal Working Group meeting 10/27

[Elton Smith <elton@jlab.org>]

=Minutes=
Attending: UofR: George, Andrei, Zisis, Blake, Stamatis; IU: Matt, Claire,
Brad (studying radiation on blocks); JLab: Beni, Tim, Elton, Elke; TSM:
Will

# Calibration
#* Filling [[Sep 2, 2008 Calorimetry#Calibration Specifications Table |
Calibration Specification Table]].
#* Zisis and George have added entries to the table.
#* IU meet internally and is discussing best numbers for table. Claire is
studying how to calibrate the Fcal using pi0's. Based on results this will
have an impact on the frequency and accuracy needed of a monitoring system
#* The requirements should be reviewed in a future meeting when all input
is presented so that an informed decision can be made as to whether a
single or multiple monitoring systems are required for the scintillating
detector systems.
# Fcal
#* Progress on timing studies - Jake will report at the next meeting
#* Tim: Update on 64-block prototype? John has talked to local machine
shops and has been reviewing specifications and schedules.
#* A detailed schedule for construction is being generated with FASTTRACK.
Elke will send updated schedule with new procurement dates (which have
been changed).
#* Matt inquired about the status of the magnetic shield sent to JLab.
Tim' student will test in magnet, but will take a month or two. Matt's
main interest is in feedback about steel specifications in shield and
thickness requirement.
# Bcal
## Sipms: Decision on use of Getter#1 and no Getter units in the
construction of arrays. Discussion
##* [[Sep_15,_2008_Calorimetry#Post_Discussion_on_SiPMs | Summary of
delivered units]]
##* Original plan was all Getter#1 devices. Sensl now proposes a 50/50
split, Elke has proposed 80/20 plit.
##* Elton had a concern that there might be an 80/20 split might not have
sufficient statistics in the no Getter devices. Elke noted that for the
pixellated arrays, we will have a total of 16 3x3 units, which is plenty
of statistics.
##* Decision was made to request an 80/20 split. This implies that UofR
and JLab will each receive five pixellated arrays and five summed arrays.
For each set of five units, 4 will be fabricated with Getter#1 processing
and one will be with no Getter processing. Elton will send this request to
SensL.
## Bcal Sampling: Based on discussion, there will be no changes made to
the lead thickness for the bcal modules.
##* Sampling studies (Stamatis) [[Media:Meeting271008.pdf]]. Report of
work-in-progress. Three geometries studied:
##** Black: Thin lead
##** Blue: Hybrid (thin + nominal) lead
##** Pink: Nominal design lead
##* Resultion of hybrid module is about 15% lower than nominal at
threshold at 16 degrees, difference decreasing at higher energy
##* Resolution of hybrid module is larger than nominal ag 90 deg for Eg>
40MeV, difference increasing at higher energys.
##* Matt: Statistical gain is quantified, but systematic uncertainties are
introduced by having different sampling fractions.
##* Zisis: There is already a division between inner and outer readout
systems. The boundary between thin/thick lead would match a readout
boundary.
##* Elton asked what checks would have to be made if a hybrid cal were
selected. George and Zisis suggested the following minimal list:
##** Purcharse 3.5 mm lead sheets and verify that they can be properly
swaged.
##** Produce a short stack calorimeter to check fabrication proceedure.
Lead times for Pb could be minimized by ordering Pb from England at
slightly higher cost.
##** Delamination tests.
##* What is the downside to proceeding with the nominal design?
##** George: releave pressure on photodetection efficiency of readout
##** Will asked about threshold. Elton: The threshold of the hybrid design
should be able to be reduced by the improved resolution at threshold (~15%
at 16 deg, ~5% at 90deg).
##* Matt: Studies that need to be conducted before a change of design is
chosen:
##** Study systematics. Understand if different lead thicknesses lead to
increase of systematics beyond that introduced by inner/outer readout
sections
##** Study how the hybrid/nominal designs differ in reconstruction photons
in the gap between Fcal and Bcal.
##* Comments by Will Brooks on Hall B thesis (see above).
##** See Fig 3.7b corresponding to inner Hall B calorimeter (about 6 rad
lengths), 15 layers of 1 cm scint and 0.2 cm Pb. Thesis shows that for
that study that the derived sampling fraction was relatively flat near the
threshold of 100 KeV. We need to check what configuration (thresholds,
step sizes, stack? parameters for secondaries, etc) is being used for the
Hall D simulations.
## Readout: Serguei asked about the possibility of using APDs for the
Bcal.
##* George: This option was studied early on. Low gain, and temperature
stabilization were issues at that time.
##* It might be useful to see if any improvements in the technology change
the picture for readout. We will ask Serguei to present an update at the
next meeting.
## Resolution: Updates (Blake)
##* HDGEANT simulation of pi-'s, but have seg-faults. Elton indicated that
if there are areas where he can use help, he should request it.
##Magnetic field.  Zisis: Need to revisit the Bfield components in the
region of the readout. (This has fallen through the cracks).
## Construction MOUs: [[Oct 15, 2008 Calorimetry | Visit to Alberta]]
##* NSERC visits to Regina and Alberta this week.
##* Elton has a preliminary draft of a construction MOU. Will send to
Regina for feedback toward the end of the week. Zisis reminded us that he
and George will be at JLab Nov 6 and we can iterate on the MOU at that
time.
##* Zisis has obtained rates for COOP students and other financial data as
background information to the MOU.
##* Danny, Regina machinist, does not anticipate any difficulties in Ross
machining the ends (as well as sides) of Bcal modules. They will visit
Ross machining next week to review options. Requested that JLab make
updated drawings available (including O-ring) for discussions. Tim will
see if that can be fitted into designer tasks.


Elton Smith
Jefferson Lab MS 12H5
12000 Jefferson Ave
Suite # 16
Newport News, VA 23606
elton@jlab.org
(757) 269-7625
(757) 269-6331 fax