Notes on Bcal Action Item Review

[Elton Smith <elton@jlab.org>]

Hi All,

I have input my notes on our meeting this morning to the wiki at
http://www.jlab.org/Hall-D/software/wiki/index.php/Bcal_Action_Item_Tracker

Zisis: Please feel free to edit "to your heart's content", especially
correct any misunderstandings.

I copy them below into this message for conveninece.

Cheers, Elton.

------------------------------------

The following persons connected to a phone conference to review the action
items that need to be tracked in preparation for CD-3

Online: Kathryn, George Lolos, Zisis, Andrei, Elton, Elke, George Biallas,
Chuck, Tim, Christine, Pavols, George Voulgaris.

The [http://www.jlab.org/~elke/ActionItemTrackerHallD.xls Action Item
Tracker] will be kept up-to-date and used to list items that need
attention, goals for addressing them, and when they are closed out. We
went over the list and discussed the time scale for addressing them:

* Installation [Jlab]
** The current plan is to assemble the Bcal outside the magnet and then
slide it into the magnet.
** Dec 1: for Hall D engineering to develop this concept. This will
include the concept for how to connect one module to the next.
** Ideas:
*** (George) Use an O-ring groove in the Al plate to seal light.
*** Tongue and groove technique with screws to pull them together / use a
strap to pull the entire ring together.
*** (George) Use Teflon pieces to cover the iron "filler" pieces in the
magnet for the support. Can use similar type supports on the outside to
create a supporting craddle. Slipping the Bcal into place would not
require matching two different schemes for the support.

* Winston cone geometry [Regina]
** Dec 1: To provide a concept for matching the light guides to the
trapezoidal area of a Bcal module, and to consider how to make the
assembly light-tight.
** Next week: Mail a sample Winston light guide to Tim for reference (Tim
will send precise address to George).

* Eddy Currents in Bcal (during magnet quench) [Jlab]
** Need to break the connection around the circumpherence in at least one
place (likely the "keystone" module)
** Dec 1: This will be developed along with the installation procedure.

* Attachement of SiPMs to Winston Cone [Regina]
** Date? Concept by Regina

* Fiber Specifications [Regina and JLab]
** Next week: George and Christina will send Elton specifications already
written as a basis for the document. (See also one of the Tables in
[http://argus.phys.uregina.ca/gluex/DocDB/0008/000866/003/halld_specs.pdf
GlueX-doc-866].

* Light Guide Design for Outer Layers [Elton]
** Next Week: Blake will send Elton code for light guide collection
** Dec 31: Proposal to include shape and connections to PMTs.

* Length of Bcal
** Decision to keep length at 390 cm.

* Bcal Timing [Regina]
** Alex has shown that even sigma=400 ps is useful for pi/p identification
for momenta ~ 500 MeV/c <br> [[Image:Bcal Tdiffpip.jpg]] <br>
** Jan 15: Single channel diagram for electronics including splitting of
signals
** Jan 15: Determination of least count needed in TDC (F1 TDC options are
64 channels of 60 ps, or 32 channels of 120 ps).
** Jan 31: Determination of suitability of CFD or LE discrimination
** Jan 31: Testing of CFDs using cosmic-ray setup. Note: Alberta CFDs do
not use NIM levels and a converter is required. JLab will provide
converters for common signal levels.

* Increased Sampling Fraction [Regina]
** Can increase number of p.e. in the shower. However, simulations need to
show that increased shower leakage does not negate this effect.
** Jan 15: Study option of using 3mm Pb Sheets in the front of the
calorimeter and 5mm Pb sheets in the back part (precise division to be
determined)
** Christina: Questioned the availability of uniform 3mm Pb sheets.
George: These are difficult to obtain in US, but are available from
Europe. If the thickness allows for swagging the uniformity is determined
by the machine (George/Zisis, please check this statement).
** George: At the same time the physics impact needs to be carefully
checked.

* Impact of energy near threshold and number of p.e. in Bcal [Regina]
** Jan 15: Will be considered along with the previous item.

* Temperature stabilization of SiPMs [Jlab]
** Jan 31: At the collaboration meeting the question was raised as to
whether Peltier junctions could (should?) be used to stabilize the
temperature (not cool) to about 70 deg.
** George: Questioned whether cooling of large area (i.e. arrays) had been
looked at from a technical point of view.
** Bill Crahan and Fernando will be tasked with addressing the
cooling/temp stabilization of the Bcal reaout.


* SiPMs - Statement of Work
** George has provided a draft. Elton and Elke need to give feedback

* Calibration system [Athens]
** Need concept to determine location and impact on spacial constraints.
** Christina: Would like to keep the options for the laser and photo-diode
systems.
** Christina: The specs for the IU laser were checked and will meet their
requirements. They will contact Matt to determine shipping details.

* Fabrication/QA plan [All]
** February: Will revisit in Jan.