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Feature Extractor

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Feature Extractor

The future is here

Dima Chirkin, LBNL

Given an ATWD or FADC waveform, determine arrival times of all photons which contributed:

- hit series (DisableHitSeries)
- FEInfo: combination or leading edge, width, charge (or amplitude)
- reco pulse series:
- Timestamp
- Charge

undershooting: 1 mV for 50 mV pulse (due to transformer droop; corrected by the fat-reader and DOMCalibrator)

pedestal drift (corrected for by the fat-reader)

Plots by Kael and Nobuyoshi

pedestal found dynamically from data

temperature from monitoring data

permeability scaled to match measurements at +25 and –45 C.

FADC is feature extracted and results match those from ATWDs

The offset between FADC and ATWD:

- 5 (FADC pipeline stages) * 25 ns (FADC bin size)
- + 2.4 ns (FADC aperture time)
- - 75.4 ns (delay line time)
- 4 (number of ATWD pre-bins) * ~3.5 ns (ATWD bin size)
Comes up to 5.2 ns + 4*ATWD bin size ~ 19 ns

The 4.68 ns is mostly due to the uncertainty in the FADC timing for ATWD (scaling this down a factor 25/3.5) we get 0.65 ns

- A correction proportional to high-voltage needs must made to describe high-voltage-dependent delay of the developing signal in the PMT
- Laser DFL calibration should be sufficient?
- also estimated by the domcal in ice, provides somewhat less precise results (higher timing rms with the flasher data)

poor resolution in flasher runs (double or even triple peak structures) were a result of false maximum estimation in the saturated wavefroms or fitting of prepulses. This is corrected by choosing the first saturated point when looking for a maximum. Then the leading edge is well defined.

bit[0]=0

A multitude of the fast first peak options were implemented:

FastFirstPeak is a 0-7: bitmask, bits 0-2 are used:

* bit[0]=0 (values of 0,2): largest peak and its charge

1. look for the first time bin, which value is 1022 in ATWD counts of the ATWD channel, which was used for this bin (normally the highest channel available).

2. find the bin where the waveform reaches its maximum among bins from 0 to the one found in step 1 (or, if it was not found, all bins), which are above the threshold (set with ADCThreshold).

3. from the maximum found in step 2 go downhill to the beginning of the waveform and find the pair of bins between which the increment (i.e., the estimate of the derivative) is the largest.

4. draw a line though these two points and find its intersection with the baseline; that's an estimate of the LE. Fit a parabola in the vicinity of the bin corresponding to the waveform maximum, found in step 2, to get an estimate on the location and amplitude at the maximum; assuming a standard pulse shape (which depends on the 3 parameters and the baseline) find the charge estimate Q contained in the part of the waveform, which is closest to the found LE and maximum.

* bit[0]=1 (values of 1,3): first peak above the threshold and the total waveform charge

1. Advancing through the waveform (from the first time bin), find the first pair of bins with values above the threshold, for which the increment is locally at maximum (i.e., it gets smaller for the next pair, and was smaller for the pair before the found one).

2. draw a line through these two points and find its intersection with the baseline; that's an estimate of the LE. Sum all bin values in the waveform, which are above the threshold; this is an estimate of charge Q.

bit[0]=1

- bit[2]:
0: default.

1: enforce the total above the baseline charge calculation when bit[0]=0 (as is done for bit[0]=1).

- bit[3]:
0: default.

1: Feature-extract FADC.

MaxNumHits [default=0]: Maximum number of SPE-like fits to combine. Set to 0 to perform a fast le fit and charge estimate only (w/o root fit). Set to 1 to refine this result with the root fit (still only one pulse per waveform is fit). DO NOT USE: mostly obsolete

MinSPEWidth [default=4]: Minimum SPE-like pulse width in [ns]

MaxSPEWidth [default=20]: Maximum SPE-like pulse width in [ns]

InitialHitSeriesReco [default="InitialHitSeriesReco"]: The name of the produced hit series in the RecoHitSeriesData

DataReadoutName [default="ATWDReadout"]: The name to be used for reading the datareadout from the event

FeatureExtractor [default="FeatureExtractor"]: The name of the analog Info produced by FeatureExtractor

- FastFirstPeak [default=0]: select the initial solution method (or the only solution if both of the multi-peak reconstruction methods are disabled
- ADCThreshold [default=0.4]: ADC Threshold in terms of SPE discriminator threshold
- FastPeakUnfolding [default=-1]: Fast fit unfolding: set to 0 to enable. This can be used as the only multi-peak extraction algorithm, or in a combination with the root fits. The latter is enabled if FastPeakUnfolding is positive and MaxNumHits is not 0. If the total charge in the waveform is less than FastPeakUnfolding, the fast unfolding is performed, otherwise the root fits are used.
- PMTTransient [default=2]: Add PMT transient time to extracted hit times if 1 (linear with Voltage) or 2 (wider range sqrt fit). Use 0 to disable.
- DisableHitSeries [default=0]: Disable hit series generation - use to speed up processing of waveforms with very large charge.