Star-tpc-l mailing list

[videbaek <videbaek AT bnl.gov>]

As mentioned at today's 10 o'clock meeting the noise has again shown up 
with the same features as early in the week

The sequence was the following
good up until run 87017  8:26
then some misc activity in the hall

87013 was first pedestal run after the access.
87026 first cosmic run \ reasonable good but signs of noise apperent in 
RDObyte plot
by run 87039 really bad (2014):
stayed bad until morning when I requested a pedestal run at the meeting.
At the first run after the pedestal run it was ok. and still is now 
(16:30 Saturday).


I look a bit more and it seems it is not just noise in the adc spectrum, 
but gives rise to to incearsed #clusters as observed in some of the 
#clusters per sector (inner).This is unlikely a problem for lasers and 
cosmics.

We need to think about this and discuss how to isolate the problem.
Observations:
What is common for sector 3 and 4 as the seems to go bad together.
--- ideas RDO power supplies sharing
---  gating grid noise.
     Is it not true that for iTPC there is no timebin dependent pedestal 
so strange noise patterns could disturb values uploaded ?

Is there evidence from the data from the pedestal runs if it is a shift 
in pedestal, and increase width (i.e noise level).
It is spread out across all timebins, and we see it across all pads and 
rows.
A particular feature seems to be a peak in the middle of the time 
spectrum.




--
Flemming Videbaek
senior scientist, emeritus
videbaek @ bnl.gov
Brookhaven National Lab
Physics Department
Bldg 510D
Upton, NY 11973

phone: 631-344-4106
cell     :  631-681-1596