Notes on presentations for the detector review

[Elton Smith <elton@jlab.org>]

Notes taken on the subsystem talks and comments
-----------------------------------------------
Disclaimer: Notes may not be complete or impartial, but hopefully useful
as we prepare for the detector review.



General:

- Outline of CDC talk is a good one for most talks at the review:
1. Physics requirements
2. Design choices
3. Prototyping activities
4. Final design
   - issues which still require study
5. Manpower, schedule and cost
6. Summary
A template like this might be suggested for most speakers.

- At the review we need an overview talk to go over the physics and
requirements for physics quantities, such as momentum resolution, energy
resolution, angular resolution, etc. These can then be taken as motivating
e.g. position resolution in the drift chambers. This needs to be done
ahead of individual subsystem talks, since it clearly spans more than one
system. For example momentum resolution is obtained by the combined
analysis of the FDC and CDC.

---------

Specifics:

o Barrel.
- Readout needs clear development. If the SiPMs are considered a leading
contender, a straw proposal for segmentation, and estimates for the
amount of light collected need to be developed.
- Fiber size? My guess is that the 1 mm fibers can be defended empirically
based on existing detectors, but it is worth preparing a paragraph with
appropriate references.

o LGD.
- Requires physics justification for resolution (energy and position)
- Show that the Pb detector can achieve those goals.
- Establish comparison of E852 quoted resolutions with those of Radphi
* Use Radphi resolutions to simulate quantitities of interest e.g. pi0 and
eta mass widths, etc.
* Prepare a proposal for how to handle radiation damage surrounding
beampipe.
* Preliminary evaluation of FEU pmts is very important, since it will
determine if they can be reused for the experiment.
- Design for magnetic shielding of pmts needs to be described.

o CDC.
* Consider track finding: number of planes per superlayer (>6?)
- Resolution of physics quantities needs to be given, namely dp/p, dtheta,
dphi, etc. -> position resolution.
- dE/dx must be addressed in a little more detail, either here or in the
PID section.
- rate capability?
- ageing?
- Need picture/description of tube assembly.
- Elliott had many suggestions.

0 FDC
- Need a physics justification.
- Describe motivation of choice of technology (e.g. wires and cathode
strips)
* Material in beam. Need initial estimate for total thickness and a
proposed scheme for how to mitigate this.
* Consider pattern recognition issues as the motivation for design.
- Understand why cathode strip signal seems to be narrower than anode
signal.

o Solenoid
- For the review, we need a general intro into the magnet before detailed
breakdown of refurbishment effort.

o Target
* Obtain a nominal target diameter based on minimum t to target proton.
- Develop nominal design based on Hall B target.

o PID
- Quote 3sigma nominal separations for particles (not 1sigma)
- Note that Figure 6.44 was created assuming 50% efficiency on top of the
  N0 = 90 cm-1.

o TOF
* Length of bars needs to reflect actual acceptance of charge particles
  coming out of magnet. (Preliminary discussions this was 250 cm).
- Concept for hole for beamline needs to be added. How does this affect
  actual performance near the center?

o DIRC
- Note that considerable data would be added to the DAQ rate. A number for
  the data rate (MB/s) needs to estimated for input to DAQ.
- Excellent start on a preliminary conceptual design

See below for discussion

o Tagger
- Needs to provide and motivate design parameters:
  - energy resolution
  - length of focal plane motivated by crystal alignment
  - justify such a small bend angle (10 deg) by cost?
- For the design review, the nominal design should be presented, and
  options (single magnet, superconducting magnet, etc) only mentioned and
  then left for questions.
- Increase gap height?
- Concept for tagging detector needs to be presented at review
- Realistic simulation of backgrounds in tagging spectrometer required
  before final design (probably not necessary for review).
- Alignment of two magnets relative to one another.
- Distorsions of gap due to vacuum, Bfield, etc.?

o DAQ
- Clear design requirements need to be presented at the detector review
- Estimates of work division between GlueX and JLab DAQ group should be
  developed.

o Start Counter
- Use of SiPMs?
- Embedded wavelength shifters (as in tile calorimeter designs)?
- See separate notes on start counter goals.

o Trigger
- Backward veto in trigger?

o Infrastructure
- Fringe fields of magnet a the position of the tof pmts and LGD pmts.
  - Paul will appoach this in a two step process: a) include bulk size and
    weight of cellular wall into model to obtain fields at TOF pmts,
    b) create a model for small section of cellular wall and create an
    external field to match original estimate. Use the distorted field in
    the wall to provide better estimate of field at location of LGD tubes.
- Study Bcal insertion mechanism options in more detail (George with Ravi
  and Paul)
- Finalize positions and sizes of all detectors (Curtis and Zisis may be
  close to this already) and disseminate this info.
- Obtain a total rack count for electronics and review power budget (Paul
  Smith to look at estimates by Chris)

o Electronics
- Pipeline issues: Fallen between the cracks?

o Cerenkov/DIRC counter Discussion
- No champion for gas Cerenkov design
- New group willing to take on responsibility for DIRC
- Make physics case for DIRC (pro/con list)
  - Richard to review options of gas, gas/Aerogel, etc,
- Proposal to concentrate first few years on plhysics with pions.
- Consider DIRC as an upgrade to basic detector design

o Preparations for Review
- Allison and Larry to address committee
- Larry will be the formal (JLab) contact to review committee. Elton will
  be the conduit between the collaboration and Larry.
- Alex will give the PID and LGD talks
- Split DAQ and Electronics into two talks
- David Lawrence will give the software talk





Elton Smith
Jefferson Lab
elton@jlab.org
(757) 269-7625