Transcript C-side: status and plans for current week

ECAL: status and plans
Outline:
 Some results from last LED data;
 Requests;
LED data (Friday afternoon –
Saturday morning)
 Run 026308 - nominal LED / HV from
DB, 10k events
 Run 026340 – nominal LED / HV from
DB, 60 points 1600 events each, 1 point /
10 minutes;
Time alignment problems (according
to the 026308)
C-side: 66 LEDs are not in T0
8 LEDs – no data
A-side: 5 LEDs are not in T0
5 LEDs – no data ( + the
area with damaged bundles, 3 LEDs)
Run 026340-I
(trends are provided by Yu. Guz)
It seems that in runs
026340 and earlier 025041
all PMs behave like that!!!
Run 026340-II
(trends are provided by Yu. Guz)
??? And also some PINs ???
But not all of them.
Run 026308
(trends are provided by Yu. Guz)
!!! Looks like the
stabilization effect !!!
From old (May 2006) slides:
“ At the condition LED is stable
(according to the PIN readings):
some PMs have certain
stabilization time after
photocathode illumination begins
(~1-2minutes at LED fire frequency
300Hz). During that time PM signal
drift could reach 4-5%. This
observation is taken into account in
test procedure: first 20K of events
in any data sample are not
analyzed “
(To be honest, I forgot this
observation too :)
It means that:
For reliable stability studies:
! much more LED events per point should be
acquired !
! First few K’s of events should be excluded from
analysis. Otherwise the major contribution to
the width of LED signal will not come from
photo-statistics!
There should be no “stabilization” effect during
normal data taking (to be checked, of course)
What else can be learned from the
data, which are acquired?
(prelim, more results in one week)
1) No readings from several LEDs. Bad time alignment or real
hardware problem? C-side is checked today. One flat cable
transporting LED voltage is found to be damaged during last
intervention (serves 2 LEDs, connector is to be replaced). The rest
of LEDs are operational, though RJ-45 LED fire signal transporting
cables are still to be checked. Access to the platform is needed. Is
it OK for tomorrow?
2) On both sides: a lot of channels with LED signal in saturation – LED
intensities should be corrected (more details few minutes later);
3) List of cells with no LED signal :
~ 30 cells - C-side
~ 40 cells - A-side, but more then half of them – due to
damaged optical bundles
To be cross-checked with the cosmic data. C-side I can also check
with the scope during next few days.
What can be learned from the
data, which are acquired? (cont)
4) There are VERY unstable channels. If plot the maximal
observed variation of the LED amplitude, normalized
on the mean LED value (here I took the signal not from
T0, but from the BX with maximal LED amplitude):
Y-axis:
LOG scale
C-side
A-side
Unstable cells (worse than 6%)
HV box #4
C-side
Power lines
A-side
Control box #4: unstable LV
behavior
According to the
LED, by DAQ
Positive LV,
by DCU
Dependence of the gain on LV
for ECAL C-W (lab tests)
Negative LV
Positive LV
Power Line O 37/6…57
All channels show
similar behaviour
Positive/Negative LV OK by DCU
According to the
LED, by DAQ
What can we do?
1) Control box #4 – check the connector between
LV bus and control box. If does not help – try to
change mezzanine…
2) The rest of unstable power lines: try to replace
connector on the power line (control box side)
3) If it will not help – try to swap problematic line
with the neighboring good one and see the
result
4) For the rest of unstable channels, not related to
power lines – try to check signal connectors on
the FEB side (access to platform is needed.
Next weekend?)
Requests for this week
1) Before adjusting of LED intensity: once
again change the HV settings to account
for the spread in PMs quantum
efficiencies (r.m.s.~6%)
2) Take several data sets
to adjust LED intensities