Timing, Gain Calibration, Error Banks

1Kazu Akiba

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.– 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.

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Timing

Sadia Khalil*, Ivan Mous★

*Syracuse, ★Nikhef

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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.

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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.

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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.

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TP Value on the optimal delay compared to TP run.

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.

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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.

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Width 1 Width 2

Amplitude

Peak (ns)

Constant(offset)

25 ns 25 ns

Spillover (ns)

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Proof of principle.

Credits to Ivan Mous

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

•

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Applying to the TED run:PRELIMINARY

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TELL1 29 TELL1 30

Gain

Grant McGregorManchester

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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.

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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.

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“Header-High” distribution“Header-Low” distribution

Full Header Swing (FHS)

Variation across links/sensors

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Low gain/dead links

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.

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Error Banks

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

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Chasing the TELL1 Errors

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• 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.

Thresholds as they were: almost 0 Pseudo headers.

Thresholds 450/550

We can induce errors

So can get rid of them as well

Pseudo Header ErrorsDef: Failure to determine the header state…

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.

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Summaries• 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.

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