Minutes:  FPS Meeting at USB:  (Oct. 13, 1998: 9-10:15 AM)

In attendance: M. Zdrazil, P. Yamin, S. Desai, A. Talalaevskii, J. Kotcher,
               A. Patwa (*), J. Steffens, M. Liu

(*)=scribe
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We held a brief (~1 hr.) FPS meeting at Stony Brook to go over status/progress
reports on a.) calibration system (from Talalaevskii/Steffens/Rijssenbeek)
and b.) optical light connectors (from A. Patwa) that are being molded 
by M. Chung at UIC, Chicago.

A. Talalaevskii reminded the group of some of the pros/cons in using LEDs 
pulsed from the outside world (i.e the platform) and carrying ligth to the
modules by fibers.  He has also taken a short clear fiber (Kuraray,
multiclad) and coupled it to the blue LED on one side and to the
cylinder block on the other.  A WLS fiber then is coupled along the 
length of the cylinder block and signals from the pulsed LED/clear-fiber 
can be measured via PMT.  He has commented that relatively low signals
are observed from this setup than those measured from having the LED 
mounted directly within the cylinder.  The primary reason is believed to be 
from the coupling of the LED to the clear fiber.  Perhaps, a tapped hole in the
LED dome wall which allows a direct fiber-to-diode coupling might help.  This, 
as well as using optical glue might yield reasonably higher signals.

A. Talalaevskii also presented a slide prepared by M. Rijssenbeek on the 
requirements for LED light injection and multiplexing electronics.  For reference,
the type of system is listed below:

	o   LED + In-Module Electronics Option:
            	- Single LED per cylinder (connector) only
		- control electronics: FPGA
		- Inputs:
			- LEMO trigger pulse deterimining LED pulse width and
			  timing
			- 2x4 pin twist and flat connector	
			- V(led) determines LED pulse height
			- Data-In: address information
			- Mode: load-address / ready for pulsing
			- Clock: slow address shift clock signal
			- grounds for above
		- PC Board:
			- 20 x 100 sq. mm
			- space limited but not impossible
			- needs 10 mm height over 12 x 100 sq. mm in area directly
			  inside center edge of module, and 8 mm more (at 3.3 mm 
			  height) over scintillator itself; perhaps placed also in-
			  between location of WLS fibers and support ribs.  

   	o   Injection via clear fibers:
		- easier installation; needs 16+2 clear fiber (2 reg. connectors per
		  large module, 1 per small module)
		- needs "one splice per cylinder" inside the module to hook-up the
		  cylinder fiber pigtails to the pigtails from the blue light input
		  connector.
		- Fused silica fiber (atten. length: 5-10 dB/km at 470 nm); projected
		  cost: ~$2/m;  ship/ordered ~100 m to SB for mock-up and tests.

J. Kotcher also mentioned that if clear fibers were brought in from an outside source, 
then it might require considering the extra 10% variation that is built-in
to the 16-channel FPS connectors (i.e. channel-to-channel uniformity) when
designing the calib. system.  This is mainly because the clear fibers
would require use of a FPS connector at the outer ring to pulse the
cylinders located within individual modules.  Further, strain
relieving and installation issues must also be carefully modeled.  

It was agreed that since very limited time was available at this meeting, the group would 
meet in the afternoon at BNL (~2:30 pm);  this would be mainly a "working" meeting where 
a sense of the space available for any type of LED system can be observed from the completed
layer 1 & 2 FPS support structure nesting at the BNL lab.  

Finally, A. Patwa discussed the status of the FPS connector: M. Chung has made considerable
progress on the light yields.  The connector pins were electroplated as to compensate a mis-
alignment that was introduced in the 4x4 grid pattern; also pins 8 & 16 were adjusted for
axial alignment.  As a result, there is still a 12-13% variation after this process which is
presumed to be due to pin no. 8 (i.e. the variation drops to 8.7% if one excludes this
channel).  Therefore, the next step is to adjust pin 8 and measure two-three connectors to not
only fix this effect but also observe whether the adjustment on pin 16 after electroplating 
still is intact.  This will be done in the next week and results will follow shortly thereafter.

The meeting adjourned at 10:15 am and would reconvene at BNL around 2:30 pm later in the day to
work on the calibration system.