There is only one copy of QRT, MPS and Helicity signals in GeN experiment, that could be used to got the helicity information on event-by-event bases. And we have 3 redundant copies of 105 kHz clock signal. Helicity signal comes in quad structure either ~043~ ~045~ ~045~ ~043~ or ~045~ ~043~ ~043~ ~045~. Each helicity cycle (time between 2 helicity switches) is 33.3msec. There is 0.5msec blank-off period for each cycle which is necessary for Pockel cell changing and settling. Due to that dead period we have about 1.5% events with unknown helicity, which is shown in data as helicity = 0. Except that we have unknown helicity period at the start of each run, because of prediction algorithm need to collect enough information before it starts work.
- Helicity information (MPS, QRT and Helicity signals) comes from TIR (i/o registers) in ROC 28. They appear in in the hexadecimal dump in the 3-rd word (firs word is a header: 0xfadcb0b9, second word is event number): />7-th bit contains MPS(Gate), 6-th bit contains QRT and 5-th bit contains helicity itself.
+ Helicity information (MPS, QRT and Helicity signals) comes from TIR (i/o registers) in ROC 28. They appear in in the hexadecimal dump in the 3-rd word (firs word is a header: 0xfadcb0b9, second word is event number): 7-th bit contains MPS(Gate), 6-th bit contains QRT and 5-th bit contains helicity itself.
- Software code responsible for decoding helicity information is in the AGEN library: GenHelicity.cxx />Three functions in the code - ReadData(), QuadCalib() and QuadHelicity() are handling three main steps of decoding: reading helicity signals as well as 105 kHz clock signals, initializing of prediction algorithm, using of prediction algorithm to got helicity information.
+ Software code responsible for decoding helicity information is in the AGEN library: GenHelicity.cxx Three functions in the code - ReadData(), QuadCalib() and QuadHelicity() are handling three main steps of decoding: reading helicity signals as well as 105 kHz clock signals, initializing of prediction algorithm, using of prediction algorithm to got helicity information.
;: 1. On the first step of decoding program reads 3 bits from the data-file: QRT, MPS and Helicity and also the 105kHz clock information. 3 main helicity signals has only one read out source in GeN experiment. However 105 kHz clock information read out from 3 different scalers. Due to high radiation sometimes one of the scalers give wrong information. As final 105 kHz clock read out program takes the read out from at least two scalers that match each other.
;: 2. On the second step code collecting enough helicity data to figure out where we are in the sequence and make helicity prediction for following events. For that part of run helicity is unknown.
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