RE: Status of aerogel as of Oct/6, 0amEST.

["Susumu SATO" <ssato@bnl.gov>]

Dear Edoward,
 
 We have measured the ADC for different choice of combination,
they vary, depending on which divider output you use and which cable you
use,
they are varying in 2 - 3 order of magnitude. Why do not we discuss
at highbay, so that you may know how difficult the control is.

Sincerely, Susumu SATO.

> -----Original Message-----
> From: owner-phenix-highpt-l@bnl.gov 
> [mailto:owner-phenix-highpt-l@bnl.gov] On Behalf Of Edouard Kistenev
> Sent: Monday, October 06, 2003 8:47 AM
> To: phenix-highpt-l@bnl.gov
> Subject: RE: Status of aerogel as of Oct/6, 0amEST.
> 
> 
> Dear Susumu,
> we always wanted to know also if light yield seen by 
> different PMT's (16 PMT's in 8 boxes triggered by the same 
> LED driver) is close or differ a lot. Do we have any answers 
> to this question now?  The x 1000 variation in the light 
> yeild tells us - we are at the start of the threshold curve 
> and it it very steep. Smoothening it can be done (SB) but 
> first we really need to know if all our LED's are close in 
> the light yield.
> 			Edward
> 
> -----Original Message-----
> From: owner-phenix-highpt-l@bnl.gov 
> [mailto:owner-phenix-highpt-l@bnl.gov]On Behalf Of Susumu SATO
> Sent: Monday, October 06, 2003 12:56 AM
> To: phenix-highpt-l
> Cc: .__Susumu SATO
> Subject: Status of aerogel as of Oct/6, 0amEST.
> 
> 
> Dear All,
> 
>   The followings are status as of Oct/06 for the aerogel 
> counter. Sincerely, Susumu SATO.
> 
> 
> --- beginning of the status ---
> 
> (1) PMT cathode
> 
> The problem found about 10 days ago, i.e. (i) most of the
> PMT cathode requiring additional insulation btw.
> mu-metal and (ii) large number of the soldering points
> on the lid (PC-board side) of HV cable requiring
> clean-up of flux, are urgently being cured, and about 65
> boxes out of 80 boxes has been fixed. Still the works are 
> needed for remaining boxes.
> 
> (2) LED
> 
> The LED test is tried for the 8 boxes, and
> a large problem has been observed today.
> 
> (2-terminology)
>  For each one of output of "LED driver",
> we use two bundle of cables (I here call "A"), and
> each of which carries 4 cables (I here call "B") inside.
> Namely 8 boxes are driven by one output of LED driver,
> and each output of LED driver has a variable resistance
> to change its output. Therefore,
> 1 "LED driver" with 1 variable resistance --> 2 "cable-A"s 
> --> 8 "cable-B"s --> 8 box(16 PMTs)
> 
> (2-problem)
>  If we pull off one of "cable A"s out of two,
> the out put of light (amplitude of PMT output)
> on the LED connected on the other one of
> "cable A" became some thousands times larger
> than the case where two "cable A"s.
> 
> (2-action item)
>  We need to consult with John and Steve
> to modify the divider output (one-set-of-eight
> in stead of two-sets-of-four).
> 
> (3) Light leak
> 
> The light leak of the boxes seems to require the tapes
> along the lid from outside. As the number of
> boxes we check increases, the leak is seen not only
> at the corner (also the leak at the corner needs
> additional shielding from outside).
> 
> (4)
> 
> The N2 leak shield seems to require the taping along
> the lid from outside. In the situation where no taping
> is done, large fraction of the gas is lost on the paths. 
> Considering from the lifetime of the tape, the black-cloth 
> tape for the gas shielding seems to be the best. Also 
> parallel input for each box is needed. The output line is 
> better to be daisy-chained for each column (10 boxes) in 
> order to see whether the output is there. The effect of 
> shielding with black-cloth tape needs to be tested.
> 
> --- end of status, and end of email ---
> 
> 
>