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Re: fadc dynamic range of FCAL




HI Mark and Beni,

We have to be careful. If the flash is 10 bit, then if we set the max
(1024) to correspond to 9 GeV (sum measured with effective 12 bits), then
1 bit corresponds to 8.8 MeV. Therefore, without saturating the maximum
pulses, the resolution on the lowest values suffers. It is true, however,
that 30 MeV would have about 4 samples with values of about 1 bit each.
Not too good.

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 Sun, 3 Feb 2008, Mark M. Ito wrote:

> If you have a 10-bit flash, and your pulses show up in 4 time slices,
> then you have roughly a 12-bit dynamic range. That is a factor of 4096.
> If you set the top at 9 GeV then the least count is 2 MeV. So you
> measure your 30 MeV in about 4-bits, which is not bad.
>
> 9 GeV is probably more than you will ever see, so that spec can probably
> be relaxed. Plus there is the trick Elliott mentions for the rare whopper.
>
> Note also that we are not talking about firing a discriminator with a
> threshold. The FADC info will be there, it is just a matter of how quiet
> the pedestal is.
>
>