[Halld-cal] Pulsing of Fcal and Bcal monitoring systems

[Elton Smith]

Dear collaborators,

The cabling connections are being finalized and to complete design of 
distribution boxes and purchase necessary hardware we need to finalize 
some decisions regarding granularity of the pulsing and the bias supplies.

A quick reminder of what we have: The Bcal and Fcal LED biases, +5V 
power, and trigger signals are supplied externally to the control 
boards. Each trigger signal will pulse 10 LEDs at a time. For testing of 
the mini-Bcal, we have been providing the bias the Bcal monitoring 
strings with a single bias, single +5V and a single trigger signal to 
pulse one string at a time. The trigger pulse was generated using NIM 
logic to produce TTL pulses. The bias and power for the boards will be 
provided by the same modular supplies we are using for the SiPMs, but we 
need to decide on the granularity (i.e. how may strings do we power from 
a single channel). The pulse generator should be programmable, so we 
need to make a decision about which electronics to purchase, and also 
how many strings should be pulsed at the same time (i.e. how many 
independent trigger signals do we need for the entire detector). One 
possibility is to use the VME 1495 with A395D boards for TT output, 
which can be programmed via VME.

One final note about cabling distribution. For the Bcal, the voltages 
and triggers will be routed through distribution boxes, each box 
servicing one sector upstream or downstream. Therefore, the decision to 
be made is how many signals go to each distribution box, what cables are 
used and what electronics is used to generate the trigger signals.

I pass this on for people to start thinking about this. We can have a 
discussion at the Cal Working group meeting next Tuesday.

Cheers, Elton.


-- 
Elton Smith
Jefferson Lab MS 12H5
12000 Jefferson Ave
Postal Suite #16
Newport News, VA 23606
(757) 269-7625
(757) 269-6331 fax