Pedestal estimation tool#

The pedestal estimation tool processes pedestal calibration data (dedicated pedestal runs or runs containing interleaved pedestal events) and returns estimates of the pedestal in ADC counts as a function of gain channel/pixel/sample within the readout window.

Run the tool locally#

To use the pedestal estimation tool, first activate the nectarchain environment:

$ mamba activate nectarchain

The user script nectarchain/user_scripts/ltibaldo/example_pedestal.py showcases the usage of the tool.

The input data are identified by run number. See Environment variables to set up the $NECTARCAMDATA environment variable. Events in the selected runs are processed in slices with a fixed number of events set by the events_per_slice parameter (see EventsLoopNectarCAMCalibrationTool).

The pedestal estimation tool inherits the configurable parameters of the PedestalEstimationComponent. The data can be filtered based on time using the ucts_tmin and ucts_tmax parameters and to eliminate outlier waveforms using the filter_method parameter. Two different methods to exclude outlier waveforms are implemented:

  • WaveformsStdFilter discards waveforms with a standard deviation exceeding the threshold value defined by the parameter wfs_std_threshold;

  • ChargeDistributionFilter discards waveforms with a total charge integrated over the entire readout window in the tails of the charge distribution, either below charge_sigma_low_thr or above charge_sigma_high_thr.

To run the example script:

$ python -i example_pedestal.py

Inspect the results#

The results are stored in a NectarCAMPedestalContainer. The results include information on pixels that were flagged as having an abnormal behavior during the computation of the pedestals. The flags are defined in in PedestalFlagBits. The results are accessible on the fly if the tool is run interactively (as in the example above) and stored in a h5 file.

The user script nectarchain/user_scripts/ltibaldo/show_pedestal_output.py provides an example of how to access the results from disk and produce some plots:

$ python -i plot_pedestal_output.py