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M E M O R A N D U M
TO: Distribution
FROM: B. Mecking
SUBJECT: Hall B Upgrade Meeting Notes
DATE: 19-March-1998
MINUTES OF THE 13-MARCH-1998 HALL B UPGRADE MEETING
Present: V. Burkert, M. Khandaker, B. Mecking, M. Mestayer,
and R. Minehart
1. Large Angle Calorimeters
CLAS presently has calorimeter coverage in all six sectors up to 45
degrees, and additional coverage up to 75 degrees in two sectors. The
following processes would benefit from increased coverage (e.g. building 4
more units that could be used to complete coverage up to 75 degrees, or to
provide partial coverage to 105 degrees):
- meson decays (pi-zero, eta, and eta-prime detection)
- Compton scattering (increase kinematic coverage and detection
efficiency)
- Virtual Compton scattering (increase kinematic coverage and detection
efficiency)
- Hyperon radiative decays
- Neutron detection in elementary and nuclear processes ((increase
kinematic coverage and detection efficiency)
In order for the calorimeter upgrade project to proceed, we need to put a
document together that outlines the physics that increased calorimeter
coverage would allow to access. In addition, technical details, like cost,
manpower, schedule, and required funding will have to be documented.
2. Drift Chamber/Tracking Improvements
CLAS operation at higher energies would benefit from improved fractional
momentum resolution. The following possible improvements were discussed:
- implement helium bags (those were part of the original design, but were
never implemented)
- go to lighter drift chamber gas (especially important for Region II)
- install faster post-amplifiers
3. Magnetic Shielding of Inner Detector
There was some more discussion of the magnetic shielding required to
protect the inner detector from the flood of Moller scattered electrons.
Two different methods had been mentioned both providing longitudinal
magnetic field to contain the transverse motion of Moller electrons
- a thin, small diameter superconducting solenoid surrounding the target
and the beam line. Such as thin solenoid has been built for the Bonn
frozen spin polarized target. The solenoid is only about 1mm thick; it
uses a single layer of superconducting wire, and delivers a field of
about 4kG in a tube of about 5 cm diameter (numbers need to be
checked). Such an arrangement would not be too difficult to integrate
into the present cryo-target.
- a superconducting Helmholtz-type coil arrangement. A potential solution
might be the 5 Tesla polarized target magnet shifted upstream to avoid
blocking too much of the solid angle.
Ralph Minehart agreed to extend his present simulation of the eg1
shielding requirements to include the two magnet arrangements.
A useful formula for the momentum of Moller electrons (good for lab-
angles Theta above one degree):
p = 2 * m cos(Theta)/sin(Theta)
Other issues not discussed:
- upgrade to the tagged photon system
- virtual photon tagging.
Next upgrade meeting:
Friday, 20-March-1998 9:30 - 10.50 a.m. (max)
Trailer City Room 84
No more Samoa girl scout cookies left.
Distribution: CLAS Collaboration
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