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Timing, Gain Calibration, Error Banks. K. Akiba. Commissioning. The software developments/issues reported here are dedicated towards the commissioning of the Velo. Timing affects directly the quality of the data: precision is required.

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Timing, Gain Calibration, Error Banks

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  • The software developments/issues reported here are dedicated towards the commissioning of the Velo.
    • Timing affects directly the quality of the data: precision is required.
    • The calibration of the gain and eventual equalization of the system were never tried.
    • It is also the first attempt to understand the sources of DAQ (Tell1) errors and develop methods to correct it.
  • The tasks involve the combination of PVSS – Vetra – Macros, and eventually an optimisation procedure is developed.

Kazu Akiba



Sadia Khalil*, Ivan Mous★

*Syracuse, ★Nikhef

Kazu Akiba

adc digitisation sampling
ADC digitisation sampling
  • TELL1 setting, per link granularity == 5.4 k Parameters
  • Defines the time to digitise the beetle outputs.
  • Independent of the beam: adjusted with test pulses.
  • Method to optimise implemented, and checked.

Kazu Akiba

digitisation sampling scan
Digitisation sampling scan:
  • Takes the Beetle analogue signals links
    • 64 links/Tell1, 84 Tell1s.
  • ADC digitisation scan (DELAYSCAN) runs on the Tell1 with steps of 25/16 ns – Corresponding Vetra job makes the histograms.
  • Macro analyses the resulting histograms per link basis and sets the optimal delay settings.

Kazu Akiba

digitisation sampling phase
Digitisation sampling phase:
  • An xml file is produced and uploaded to the Tell1 recipes.
  • A set of macros is used to cross-check the optimized values with the expected noise/TP height.

TP Value on the optimal delay compared to TP run.

Kazu Akiba

pulse shape sampling
Pulse Shape Sampling
  • To be adjusted to the beam: affects the S/N, spillover and pre-spill.
  • Velo wrt LHC clock, LHCb trigger
  • Each sensor wrt to the Velo: time of flight, cable lengths.
  • Method of time alignment relies on the synchronous modifications of the TTC to each sensor-Tell1.
  • Mechanism for the determination under development.
  • Tests using test pulses as “fake beam”:
    • PVSS scan implemented.
    • Vetra Analysis in place: pulse shape plot, pulse shape fit.
  • Under current development:
    • Cross check and tests with previous TED data.
    • Implementation of the optimised settings on the PVSS recipes.

Kazu Akiba

pulse shape the plan
Pulse shape: the plan
  • Use Test pulses to measure the pulse shape.
  • Determine peak time for each sensor:
    • Minimal data sample approach: event by event fitting with coarse (25 ns) samples.
    • NZS data analysis.
  • Fitting with an analytical function as well as a template histogram are under studies.

Kazu Akiba

proof of principle
Proof of principle.

Peak (ns)


Credits to Ivan Mous

Width 2

Width 1



Spillover (ns)

Kazu Akiba

checking the method
Checking the Method
  • Based on sets of 100 events spaced by 25 ns.
  • Using the Function approach, the Optimum time can be reconstructed for any phase (time shift).
  • Systematic error in determining the peak time under investigation

Kazu Akiba

applying to the ted run preliminary
Applying to the TED run:PRELIMINARY

TELL1 29

TELL1 30

Kazu Akiba



Grant McGregor


Kazu Akiba

measure calibrate
Measure  Calibrate
  • First attempt to measure the Gain of different Links.
  • Current method uses the ADC of the headers (NZS data) as an estimate of gain.
  • Crosscheck to be done with TP data: needs (both) Timing to be adjusted first. Should be available in the next weeks.

Kazu Akiba

first results fhs
First Results: FHS
  • Separate measurement of the header high value and header low, using last 2 beetle bits: HH-HL = FHS, a pedestal independent quantity.

Full Header Swing (FHS)

“Header-High” distribution

“Header-Low” distribution

Kazu Akiba

variation across links sensors
Variation across links/sensors

Low gain/dead links

Kazu Akiba

towards calibration
Towards Calibration
  • Currently the study was performed only with the header ADCs.
  • Next natural comparison would be with the TP Data.
  • PVSS scan over the Tell1 gain (Arx DAC) was recently created: to be tested and tuned.
  • Gain vs step will give the setting to be used.

Kazu Akiba

error banks

Error Banks

Ann Van Lysebetten ★, Chiara Farinelli ★, Tomasz Szumlak*

★ Nikhef, *Glasgow

Kazu Akiba

chasing the tell1 errors
Chasing the TELL1 Errors
  • Decoder: working, to be debugged further
  • Pseudo header error:
    • thresholds determined from Grant’s analysis
  • PCN errors under investigation: behaviour of the FEM beetle compared to the module.

Kazu Akiba

pseudo header errors
Pseudo Header Errors

Def: Failure to determine the header state…

Thresholds as they were: almost 0 Pseudo headers.

Thresholds 450/550

We can induce errors

 So can get rid of them as well

ultimate erroneous goals
Ultimate Erroneous Goals
  • Understanding errors: sources and how to fix them based on the error banks solely.
  • Tuning up the Velo – Eventually export the settings necessary for no Errors.
  • Error monitoring package: plots and debugging tools.

Kazu Akiba

  • Timing:
    • Digitisation timing under control.
    • Pulse shape under tests: Uploading procedure being developed, parameters for the TED to be calculated.
  • Gain:
    • First measurements show a spread of ~20%
    • Scan procedure and analysis under development
  • Error Banks:
    • Progress towards understanding and adjusting the TELL1.
    • Set of useful plots to be determined.

Kazu Akiba