Re: Pulse height amplitude (fwd from George)

[Elton Smith <elton@jlab.org>]

---------- Forwarded message ----------
Date: Sun, 06 Apr 2008 08:56:30 -0600
From: George Lolos <George.Lolos@uregina.ca>
To: barbosa@jlab.org
Cc: carl.zorn@jlab.org, elke@jlab.org, elton@jlab.org, janzen2k@uregina.ca
Subject: Re: Pulse height amplitude

Hi Fernando:

Thanks for the info.  If the fADC can accommodate up to -2V input, it
would make sense to take advantage of the whole dynamic range available
at the input level.  When we post the results, you'll see that there's a
small pulse following around 40 ns after the peak of the proper pulse.
The ratio of amplitudes is around 1% (eyeball integration) and it's not
due to reflection, thus giving me the impression that it's amplifier or
board generated but my knowledge of such systems is poor so it will be
another issue to ponder about....

My luck over the years with passive splitters has been an unhappy one.
Losing a large fraction of pulse height if you don't have much to begin
with leaves me worried. Also, we never really managed to have passive
splitters in banks of rack mounted units that did not pick up RF no
matter what shielding we tried.  Mind you, that was at TRIUMF that is an
RF bomb...

Cheers,

George

>>> "Fernando J. Barbosa" <barbosa@jlab.org> 04/05/08 4:21 PM >>>
Hi George,

Thanks for the information. The pulse amplitudes seem reasonable. It may

be possible to increase the range if these amplifiers are being fed from

+/- 5V supplies - something to discuss with SensL after all the tests
are performed.

The fADC has been designed for -0.5, -1 and -2 V amplitude ranges.
Eventually, we will also need to consider the issue of the splitters
(passive of active buffer) and their impact on amplitudes and S/N.

Regards,
Fernando


George Lolos wrote:
> Hi Fernando:
>
> I talked to Kethryn and we looked at the oscilloscope traces of the
> signals from the SiPMPlus illuminated with BCF-20 light being excited
> with the 375 nm laser.   We know that at ~1.2 V we see the saturation
> of the amplifier.  On the other hand, pulses up to ~ 800 mV are
> perfectly shaped.  Once Kathryn finishes this round of scanning
> individual cells within the 16-cell array, we'll map the range of
> amplitudes to determine more accurately the onset of saturation.
>
> Cheers,
>
> George
>