Re: BCAL Threshold -- Input Needed

[Elton Smith <elton@jlab.org>]

Hi Mark, Matt,

For reference, the SiPM pulses are currently at least 80 ns long, so
counting single p.e. pulses in a 100 ns gate will not be easy. This is
especially true in the FADC micro code. I remind you that due to the
volume of data, despite many discussions, it is not clear that we will be
able to afford to readout much more than an integral and time for each
pulse that comes through. i.e. the FADC samples will not be available
offline.

Cheers, Elton.


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

On Fri, 8 Aug 2008, Mark M. Ito wrote:

> Matt,
>
> Better late than never(?).
>
> Matthew Shepherd wrote, way back in mid-July:
> > Do we agree that this seems reasonable?  One might hope that signal
> > processing in the FADC could suppress some of the 1 PE pulses.  This
> > would effectively lower the 1 PE rate and allow a lower threshold.
> I would also hope that there is some suppression. You are assuming the
> behavior of an integrating ADC in your estimate (conservatism, see your
> words below). The flash gives much more information. Another way of
> asking the question is whether the FADC can tell the difference between
> 8 randomly spaced single pe pulses in a 100 ns window from a real energy
> deposition that results in 8 pe's. It should be able to make the
> discrimination at the 80 to 90% level or so, I would think. And if it
> can, the effective threshold can be lower, as you point out.
> >   However, I'm sure overlooking things like electronics noise in this
> > estimate, make the estimate somewhat optimistic.  As I said we would
> > like to get as close as reasonable.
> >
>   -- Mark
>
>
>