HEP-17 calibrations
Martin Kirakosyan, Danila Tlisov, Alexey Kalinin.
Individual QIE calibrations
 Previously in our SiPM calibrations averaged conversion from ADC to fC has been used
 Now (thanks to Danni) we have individual conversion for each capid of each channel of
each QIE in HEP 17 RBX.
 Now we are able to calibrate our gain and breakdown voltage measurements using this
calibrations.
Individual QIE conversion vs averaged one.
Thus, for our SiPM calibrations that is crucial to apply ADC->fC conversion for each
channel.
SiPM calibration, low LED. Reminder.
• For the moment for our gain
measurements with SPE we use
low LED setting.
• Advantage in comparison to
pedestal: better resolution of
SPE. Pedestal tail doesn’t shift
SPE peak to the left.
• Provided we have bias voltage
scan, all gains may be tuned
(<1%, as has been done in 904).
Right now we don’t have low
LED scan configuration in P5.
Should be ready soon.
Low LED calibration. 904
 In 904 we had this RBX (HEM 14 there) calibrated (tuned via Ped scan). We
use this tune as a reference:
Without outliers
Low LED calibration. P5.
 Took run with a same BV settings as in 904 on P5 and
analyzed it using same ADC2QIE conversion table (some
old one).
 Only thing that changed – low voltage panel and our
pedestals aren’t evened at P5 (may cause some small
bin migrations, unlikely). lso probably humidity, however
SiPM characteristics don’t depend on it strongly).
 This means we shouldn’t expect changes in gain
distribution.
Low LED, P5. Results
Without outliers
• As it may be seen our distribution is even slightly better (<1% acccuracy)
• However we have a shift of 1.7 fC ~ 150 mV ~ 3 C of unknown origin.
• Also we checked that our result doesn’t depend on a voltage applied to low
voltage panel, tested different settings – nothing changes.
this is strange
Closer look on outliers (one example).
We see this only at P5 (firmware version changed). Pulse shape looks fine.
Slightly bigger pedestal for oulier channels, however we should collect all of the
signal (4 TS, starting from TS # 4), also this have slightly lower pedestal. Neighbor
channel has corrupted 0 TS.
Breakdown voltage. Procedure,
reminder.
We take a sequence run changing bias voltage with a step ≈ 40 mV
(proportional to DAC setting), from 61.5 – 66.5 (to be sure that every ):
 First 1000 events -- pedestal.
 At each sequence point we take 300 fake events (put -1. in slow data).
This is done to give a 1 sec. for the new voltage settings to stabilize.
 Then we take 5000 events at each sequence point of actual data.
 Take a mean of a signal at each sequence point.
 Calculate logarythmic derivative:
1 𝑑 𝑀𝑒𝑎𝑛
.
𝑀𝑒𝑎𝑛 𝑑 𝑉
 Take out all bad points from (big rms, sudden jumps)
 Fit the derivative (see next slides). And find the maximum of it.
Breakdown voltage. How it looks.
Breakdown voltage + 3V overvoltage, corrected
to CC calibrations by Nikita and Oxana.
2 %, don’t what this value should be (ask Iouri, Arjan). This should get better.
Somehow distribution is better if we take difference (2PE – SPE) as a gain, no o-s
Breakdown voltage. Results.
Shunt 1 vs Shunt 6
Max Amplitude LED vs half amplitude
As we can see there is no more than 40 mV difference for breakdown voltage.
This prove that we have stable procedure, that does not depend on ADC 2 fC
conversion.
Breakdown voltage. Individual QIE calibrations.
 It may not look perfect for some channels (as far as I am concerned there are some problems
Second maximum, because o poor ADC2QIE conversion
with offsets in range 1).
ect of QIE to fC conversion. Range0->Range1
Significant amount of such chnnels.
Conclusion
 We have individual calibrations of ADC 2 fC.
 There is a procedure to tune gains using Low LED bias
voltage scan that seem to work fine on P5 setting.
 Still some problems in ADC to fC conversion in the region
between two ranges.
 Breakdown voltage doesn’t depend on a conversion table
provided it us smooth enough.
 It seems reasonable for the time being run our breakdown
voltage measurement algorithm using some good smooth
conversion table, while for Low LED we should obviously
use individual QIE calibration (see slide #3)