Calibration Description#

Introduction#

LST-1 PMT signals are :

  • amplified in two gain channels : High Gain ~ 17 x Low Gain

  • buffered in 4096 capacitors per channel: 4 DRS4 rings of 1024 capacitors

  • read at 1 GHz: 40 capacitors/pixel per trigger and per channel

Hence, one raw (R0) waveform corresponds to 40 samples of 1 ns per channel for each channel.

The R0 waveform must be :

  1. corrected by several DRS4 systematics effects [1]-[2]

  2. calibrated to photo-electron counts and flat-fielded in charge and time [3].

We distinguish two categories of coefficients :

  1. Cat-A coefficients : are provided to the EventBuilder to correct and calibrate the R0 waverform in order to upgrade to R1 level

  2. Cat-B coefficients : are produced offline using interleaved calibration events and used by the offline code to improve the Cat-A calibration

The target of this package is the production and bookkeeping of LST Cat-A pixel calibration data. It includes however also some preliminary tools for performing Cat-B calibrations, which will be in future provided by the DPPS system of CTAO.

Calibration coefficients are :

  1. Produced by command-line tools on the base of calibration data (flat-field and pedestal events)

  2. Stored in files (fits or hdf5 format) inside a structured data-tree

  3. Bookkept in a Mongo database, through the use of well targeted meta-data.

In the following sections we describe all types of corrections/calibrations and how to produce and bookkeep them.

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