WaveCalibrator¶
Calibrate DOMLaunches into waveforms, correcting for known issues in the electronics. This project is maintained by Jim Braun <jbraun@icecube.wisc.edu>.
About¶
I3WaveCalibrator is a module that applies calibration constants to transform the contents of raw DOMLaunches (ADC counts) into calibrated waveforms (mV), while correcting for known effects of the electronics. It is a reimplementation of an earlier module called I3DOMcalibrator.
The following transformations are applied to the digitized waveform to obtain the final calibrated output:
A baseline measured from beacon-launch data is subtracted from the ADC counts.
The baseline-subtracted ADC counts are multiplied by the bin-specific gain to obtain a voltage.
The PMT high voltage setting is used to correct the start time of the waveform for the transit time, the average time it takes a pulse to propagate through the entire PMT. Waveforms from the second ATWD chip and the FADC are corrected for their delay with respect to the first ATWD chip.
Finally, all waveforms are corrected for the effects of droop in the transformer that couples the mainboard to the PMT output. This is done by calculating the expected reaction voltage from the toroid at each time, and adding the reaction voltage to the calibrated waveform to compensate. The reaction voltages are made to decay exponentially according to a temperature-dependent model of the transformer’s behavior. When a readout contains consecutive launches from the same DOM, the reaction voltages at the end of the last launch are used to correct for the residual droop in the follow-on launch.
There are a few key differences between I3WaveCalibrator and its predecessor, I3DOMcalibrator:
I3WaveCalibrator uses the baseline measured in data-taking mode from beacon launches for voltage calibration. This is more reliable than the value measured by DOMCal and used by DOMcalibrator for voltage calibration.
I3WaveCalibrator keeps better records of what it’s done. Every waveform is tagged with the chip and channel it came from, so that the transformation can be inverted or checked for sanity by downstream modules.
I3WaveCalibrator outputs a single I3WaveformSeriesMap containing all the calibrated waveforms from its input. If separate maps for each digitizer/channel are needed, they can be extracted from the output with I3WaveformSplitter.
I3WaveCalibrator applies droop correction to all waveforms from a single readout in one pass, so that the residual droop in follow-on launches can be corrected as well. As such, no launch cleaning should be applied to the DAQ payload before calibration. If waveforms need to be separated by digitizer/chip or LC condition for later processing, this can be done using I3WaveformSplitter.
I3WaveCalibrator takes a different approach to droop correction for undershot or saturated waveforms. Instead of assuming a downward-ramping input voltage when the digitizer is floored at 0 counts, it assumes zero input voltage and allows the reaction voltages to decay until the end of the undershot region, where it resumes normal droop correction. When the FADC saturates within the ATWD window, the measured ATWD waveform is used to reconstruct what the FADC would have measured and calculate the appropriate droop correction. The same is done for high-gain ATWD channels (0 and 1) when they saturate. In the extremely rare cases where the FADC saturates outside the ATWD window or ATWD channel 2 saturates, all bets are off, and WaveCalibrator marks the waveform series for that DOM as unrecoverable.
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