Hi:
Problems found in calibration runs 10952
SM1/2 LED
problem associated with LED fake box not appearing on some LED
events is still present. Until fixed, LED calibrations are
useless. There have been repeated messsages about this. It is
a waste of everyone's time to analyze LED calibrations until
someone looks into this. It also looks as if the timing
of the fake box when it does appear is wrong - the fake box
must appear prior to the LED signals into the ADC for this calibration
to work properly. It looks as if this is not happening. The timing
should be such that the fake box signal appears first, so that it
makes the stop, and the normal box signals appear later, but on
scale on the TDCs (ie less than 0.5 microsec later). This should
be checked on the scope for a full LED calibration for a box
in the lower and attico sections for all SMs. All cal settings
will not satisfy the above requirement, but with proper delay setting
enough do to get a good calibration. At present, the delay is
completely off here, in addition to the missing fake box
problem.
SM 1/2 laser
pedestal calibration looks good on SM1/2
NO time walk calibration was performed for SM1. This is a probably
because these events are not being flagged as laser events for some
reason. We will check more on this.
Time walk calib on SM2 ok, except timing jitter is larger
than software cuttoff in most cases. This indicated an aging
problem on the laser. For now, we will loosen the jitter
threshold.
SM 3/4 LED
See above
SM 3/4 Laser
Reference ADC is reading pedestal for all events on lower SM3
On SM4/SM3 attico, the pedestal for the reference ADC have become
very large. (~ 400) because this is obtained in the LED calibrations
and we are not loading them due to problems above, the pedestal
subtraction is not correct, leading to large negative erp ADC
pedestals. This is not a hardware problem.
time walk calibration ok.
SM 5/6 LED
See above.
SM5/6 Laser
Same problem with ref ADC pedestal subtraction as on SM4.
This is not a hardware problem
SM6 the ref adc value is too low for erp ADC values in the range
used in the pedestal calibration. that is, ref adc doesn't come off
pedestal until the ERP adc is roughly half full scale. This must
be fixed before useful pedestal calibrations can be done on SM6.
Time walk calibrations on SM5, no time walk cal on SM6. probably
the same problem as appears on SM1.
Action Items:
Italy: look into fake box timing on LED calib on all SM. This has
gotten munged up, probably by the Bari box mod, and needs to
be fixed before LED calibrations are useful. To reiterate, it
is not useful to do this calibrations until this is fixed.
look into ref ADC on SM3 and SM6.
longer term, replace lasers with large TDC jitter.
US: make cut on TDC jitter looser
replace ref ADC pedestals
determine which no time walks cals on SM1 and SM6.