Weekly JLC Physics Group Meeting
Place: Fuji F2, KEK
Time:  10:30, 97/04/25

[0] Agenda
   0.1) General Notifications
   0.2) IR Study Status
   0.2) CDC R&D Status and Plan for FY97
[1] 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

[2] 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.
	c) Background
   	   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.
[3] 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.