cost estimates

[Elke-Caroline Aschenauer <elke@jlab.org>]

Dear George and Zisis,

by trying to come up with the final numbers for the budget, we over run by
2M$ in procurement and an other 1.5M$ worse of manpower some questions
came up.

And please don't count any of my questions as an attack against SiPMTs or
the bcal or ....
I only try to get numbers straight and answers to unpleasant questions
which will come.

1. do we really need CFDs for the outer barrel, what is the advantage for
   the TOF

2. currently we instrument the bcal with 4224 channels SiPMTs 1920 in the
   inner and 2304 in the outer,
   we say we combine 2 channels in the other for the electronics so we
   have
   1920 + 1152 channels of CFD (100$/ch), F1TDC(100$/ch) and FADC (250$/ch)
   of course combining things even more in the outer BCAL, will safe
   money, but of course and I know we don't have a good answer yet what is
   possible.

3. now the LV for the SiPMTs, we need bias voltage LV<50V and 10-20 nuA/ch
   the questions to answer are do we need in individual bias for each
   SiPMT array?
   if no how many can we combine, are there measurements which show gain
   for several individual SiPMTs?
   If we could combine LV-channels what is the granularity? do we need
   a resistor change to correct for different bias voltages needed, do the
   gains change with time, so we have to adjust the adjustments.

---> I know that are a lot of questions and I appreciate answers are very
     difficult to give but the LV is worse 4224*150=634k$

4. there is also the question where to but the cfds and where to do the
   summing. Cables are also an issue.
   If we would but the CFDs next to the SiPMTs we need double the amount
   of cables 8000 instead of 4000, I think that is not an option, summing
   the outer BCAL channels by 2 directly next to the SiPMTs will only safe
   1000 cables.
   ----> so I think we have to put the CFDs after the cables
   ----> comments

I appreciate any additional thoughts on this.

Cheers elke


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