[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]
New Preamp Tests
Hi Yves,
I looked at your most recent tests and the pictures really helped.
It seems to me that all point to a ground problem - not easy to diagnose
remotely. In particular, connecting the shield to GND or the bypassed HV
causes oscillations is suggestive of noise being coupled from GND to the
preamp input. I also noticed that there may be a long path from the
end-plate (straw tube ground) to the preamp GND, although this is
something to consider later and not the cause of the oscillations at
this time.
I have a bit of great news from here. Simon and I got the new
preamps installed and running on the FDC prototype and the system is
very quite (~20 mV p-p noise floor) and with huge pulses (some >1.3V).
We looked at both anodes and cathodes with 18 m cables connected to
Gerard's shaper cards (these should not be a factor in the oscillations
you get, I think). Aside from a few things to check with Gerard
(polarity and gain), the system looks good.
Simon will send an email tomorrow to a link where all the pictures
and notes will be placed. I suggest looking at the overall ground
connections - a simple diagram illustrating every connection (shields,
cables, braids, power supplies) would be very helpful. Per your
suggestion, it would be great if Gerard could visit with you after the
collaboration meeting. If you are here for the collaboration, we could
also discuss this issue and go over the FDC set-up as a reference.
Best regards,
Fernando
begin:vcard
fn:Fernando J. Barbosa
n:Barbosa;Fernando J.
org:Jefferson Lab
adr:Suite #10, 12B3;;12000 Jefferson Ave.;Newport News;VA;23606;USA
tel;work:757-269-7433
version:2.1
end:vcard