Weekly JLC Physics Group Meeting

Place: 3F Bldg 3, KEK
Time:  10:30, 98/06/26

[0] Agenda
   0.1) General Notifications
   0.2) CDC R&D Status
[1] General Notifications

[1-1] Member List (A.Miyamoto)

The JLC member list format has changed.
This is to integrate various member lists (acfahep, jlc, mailing lists,
etc.) into a single data base built on Macintosh's File Maker Pro.
Machinery to automatically propagate any changes in the master data base
to mailing lists, web pages, etc. is now being developed.

[2] CDC R&D Status (Norik Khalatyan)

[2-1] Lorentz Angle Measurement

Lorentz angle measurement is scheduled in mid July. Major concern in the
measurement is the system stability, since the candidate chamber gas 
(CO2 iso-butane) has a very small Lorentz angle, thereby requiring high
accuracy as well as resolution.
Some calibration data were thus taken at Noko University (TAT) in order
to clarify potential sources of instability and to establish methods to 
avoid them. The list of the potential sources includes:
(i) instability in the laser system itself, combined with inhomogeneity
    in the mirror surface.
(ii) pedestal drift.

Preliminary results from the analysis of the calibration data show
that the present measurement system is capable of achieving 1 percent
or better Lorentz angle measurement.

[2-2] Study of Stereo Wire Configurations

As announced before, the CDC subgroup is now preparing a paper 
describing general design principle for stereo wire chambers.

Norik Khalatyan explained the cell deformation due to stereo wire
geometry as well as gravitational and electrostatic sags, and its
effect on gas gain variation along anode wires.

The net effect can be understood as coming from the variation of 
the cell size as a function of z (the distance from an endplate).
With the Garfield program, he calculated surface field on anode
wires as functions of z. The expected surface field variation
for the innermost stereo superlayers is around 0.4% from the
stereo wire effect. It was pointed out that the field variation
from electrostatic sags was comparable, as far as the 4.6m test
chamber was concerned. This calculation combined with the gas
gain measurement using a single wire cylindrical counter suggests
a gain variation of order 10 percents.

Gas gain remeasurements are planned for the two-track separation
test chamber which has a jet cell structure.