TO: Distribution
FROM: B. Mecking
SUBJECT: Hall B Upgrade Meeting Notes
DATE: 12-May-1998
MINUTES OF THE 8-MAY-1998 HALL B UPGRADE MEETING
Present: V. Burkert, D. Cords, A. Freyberger, H. Fenker, M. Ito,
F.-J. Klein, B. Mecking, C. Salgado, E. Smith, D. Sober,
and S. Stepanyan
Howard Fenker presented a review of tracking techniques that may be
appropriate for the CLAS inner tracking detector
1. Silicon detectors
300 microns typical thickness, may be able to get away with 200 microns
no amplification, S/N problem
2. PWC with strip readout
could orient strips at 45 degrees
3. Vertical drift chamber
ideal for focal plane detectors with limited angular range
4. Straw chambers
need several layers for redundancy
material in walls could be a problem (ATLAS is using 4 mm diameter straws
with 60 microns wall thickness)
practical problem: ensure uniform gas supply
5. Microstrip gas chamber (MSGC)
2-4 mm ionization region followed by 150 microns amplification region
200 microns separation between the strips, typically not making use of the
drift time
max. size of the glass substrate: 1 square foot, typical thickness 0.5 mm
6. Micro-gap chamber
7. Scintillating fibers
1.8 mm diameter is typical (1 mm may be doable in the future)
-> material thickness is a problem
need high efficiency photon counters (cryogenically cooled?)
8. Micro-mesh gas chamber (G. Charpak)
wire mesh supported by 50 micron diameter quartz fibers
could use strips for readout
difficult to use in non-planar structures
9. Micro-dot gas chamber
could be folded into curved sheets
10. Gas electron multiplier GEM (F. Sauli)
thin intermediate amplification sheet, can be combined with any readout
scheme
50 micron Kapton sheet covered with 5 micron Cu, with lots of chemically
etched 70 micron holes, electron transparency > 50%.
provides 20K gain @ 60kV/cm gradient (300 Volts across the foil)
advantage: ions have a short path, -> high rate capability
presently in the advanced R&D stage
Howard's personal favorite is a curved GEM.
Next upgrade meeting:
Friday, 15-May-1998 9:30 - 10.50 a.m. (Seminar at 11:00 a.m.)
Trailer City Room 84
Topic: Simulation results (Stepan Stepanyan)
Distribution: CLAS Collaboration