Weekly JLC Physics Group Meeting
Place: Fuji F2, KEK
Time: 10:30, 97/04/25
0.1) General Notifications
0.2) IR Study Status
0.2) CDC R&D Status and Plan for FY97
 General Notifications
1.1) New faces
CDC group announced new members joining the CDC R&D:
Hirotoshi Kuroiwa from TAT (M1)
Hideki Okuno from KEK Tanashi
Norik Khalatyan from KEK Tanashi
 IR Study Status (T.Tauchi)
2-1) Present Status
T.Tauchi showed the outline of the recent design of the
JLC FF and IR region. What follows is a rondom list of
some points of interest. More details will be available
from the LC desing study report.
a) 1.5 TeV Option
The FF will be 1.6 km long. In the new design the
collimator section which is 1.2 km long will be
shared by the two 1.6km long FF systems delivering
beams to two IP's.
b) Mask System
The superconducting compensation magnets are 15 cm
thick requring 40 cm ourter radius, which is somewhat
bigger than the original 30 cm.
The minimum veto angle will be 50 mrad with the help
of a veto system sitting inside the mask system.
The beam-induced background has been reevaluated with
the new mask system.
The key results can be summarized as
3.6 pixels/mm^2 for 1st VTX layer (2.5cm)
0.1 for 2nd VTX layer (5.0cm)
0.01 for 3rd VTX layer (7.0cm)
10^6 neutrons/pulse ---> 5x10^9 n/year*cm^2
for 1st VTX layer.
 CDC R&D Status and Plan (Norik)
As reported at the last meeting of this series, we have
decided to build new test chambers for stereo wire R&D.
Norik-san started design studies for the new test chambers
and explained major R&D issues.
a) Stereo angles
100 mrad stereo angle is incompatible with radius
any shorter than 125 cm, as long as we insert a
shielding wire layer in every layer-to-layer gap
of 5cm wide.
This suggest using r-dependent stereo angles and
necessitates their optimization.
We should also consider the use of stereo shielding
b) Chamber stability
The wire spacing will be z-dependent, which will be most
prominent for the innermost layer. This will result in
a z-dependent gas gain. If the gain variation is too big
stable operation of the chamber will be impossible.
c) Tension problem
The tension problem is one of the most serious and
long standing problems in the CDC R&D. Norik-san
suggested reducing the number of field wires by
increasing the number of sense wires per cell.
This optin has to be seriously considered since now
we know that the electrostatic sag is significant
anyway and built-in zigzag wire configuration will
be necessary from the begining to achieve stability.
Once we decide to use the zigzag wire structure, we
can solve the left-right ambiguity within a single
cell, reducing the necessity to have a log of cells
in the radial direction.
c) Test chamber design
Norik-san is designing test stereo chambers to study
the above listed R&D items.