The Charge Rate Correction (QRC) uses the Random Access Analyser (RAA) to cycle through the events within a run and generate a crosstalk-based correction which removes channel-to-channel rate-dependence of charge. Once the correction is generated, it is packed into an extended zdab and can be accessed by calling UPK and then CAL.
The QRC processor looks at crosstalk activity in each channel in a certain time window, and uses channel charge values and card hit rates (hits/sec/card) to determine the charge correction. Since the correction is based on crosstalk (/noise) it is necessary to run QRC with no other cuts applied in order to take into account all activity present in a channel or card. QRC should be OK to run with other subprocessors as long as this no-cuts guideline is followed.
The application of QRC relies on a word that is set in TCAL (_QRC_MODE); if the word is set to 1, the correction will be unpacked from the xzdab in UPK and then stored as a word in the PMT bank (KPMT_QRC). If the word is set to 0, no QRC info will be unpacked.
Once the information has been unpacked, another set of words in TCAL (_QRC_Qxx) specifies to which charges (QHS, QHL, QLX) the correction should be applied. If the correction is desired, it will be applied to the charge (in cal_calibration_pmt.for) which will then be placed back in KPMT_Qxx.