class AliTPCCalibPulser: public AliTPCCalibRawBase

Implementation of the TPC pulser calibration

Origin: Jens Wiechula, Marian Ivanov   J.Wiechula@gsi.de, Marian.Ivanov@cern.ch



 *                      Class Description                                  *
 ***************************************************************************

 The AliTPCCalibPulser class is used to get calibration data concerning the FEE using
 runs performed with the calibration pulser.

 The information retrieved is
 - Time0 differences
 - Signal width differences
 - Amplification variations

 the seen differences arise from the manufacturing tolerances of the PASAs and are very small within
 one chip and somewhat large between different chips.

 Histograms:
   For each ROC three TH2S histos 'Reference Histograms'  (ROC channel vs. [Time0, signal width, Q sum]) is created when
   it is filled for the first time (GetHisto[T0,RMS,Q](ROC,kTRUE)). The histos are stored in the
   TObjArrays fHistoT0Array, fHistoRMSArray and fHistoQArray.


 Working principle:
 ------------------
 Raw calibration pulser data is processed by calling one of the ProcessEvent(...) functions
 (see below). These in the end call the Update(...) function.

 - the Update(...) function:
   In this function the array fPadSignal is filled with the adc signals between the specified range
   fFirstTimeBin and fLastTimeBin for the current pad.
   before going to the next pad the ProcessPad() function is called, which analyses the data for one pad
   stored in fPadSignal.

   - the ProcessPad() function:
     Find Pedestal and Noise information
     - use database information which has to be set by calling
       SetPedestalDatabase(AliTPCCalPad *pedestalTPC, AliTPCCalPad *padNoiseTPC)
     - if no information from the pedestal data base
       is available the informaion is calculated on the fly ( see FindPedestal() function )

     Find the Pulser signal information
     - calculate  mean = T0, RMS = signal width and Q sum in a range of -2+7 timebins around Q max
       the Q sum is scaled by pad area
       (see FindPulserSignal(...) function)

     Fill a temprary array for the T0 information (GetPadTimesEvent(fCurrentSector,kTRUE)) (why see below)
     Fill the Q sum and RMS values in the histograms (GetHisto[RMS,Q](ROC,kTRUE)),

 At the end of each event the EndEvent() function is called

 - the EndEvent() function:
   calculate the mean T0 for each ROC and fill the Time0 histogram with Time0-<Time0 for ROC>
   This is done to overcome syncronisation problems between the trigger and the fec clock.

 After accumulating the desired statistics the Analyse() function has to be called.
 - the Analyse() function
   Whithin this function the mean values of T0, RMS, Q are calculated for each pad, using
   the AliMathBase::GetCOG(...) function, and the calibration
   storage classes (AliTPCCalROC) are filled for each ROC.
   The calibration information is stored in the TObjArrays fCalRocArrayT0, fCalRocArrayRMS and
   fCalRocArrayQ;



 User interface for filling data:
 --------------------------------

 To Fill information one of the following functions can be used:

 Bool_t ProcessEvent(eventHeaderStruct *event);
   - process Date event
   - use AliTPCRawReaderDate and call ProcessEvent(AliRawReader *rawReader)

 Bool_t ProcessEvent(AliRawReader *rawReader);
   - process AliRawReader event
   - use AliTPCRawStreamV3 to loop over data and call ProcessEvent(AliTPCRawStreamV3 *rawStream)

 Bool_t ProcessEvent(AliTPCRawStreamV3 *rawStream);
   - process event from AliTPCRawStreamV3
   - call Update function for signal filling

 Int_t Update(const Int_t isector, const Int_t iRow, const Int_t
              iPad,  const Int_t iTimeBin, const Float_t signal);
   - directly  fill signal information (sector, row, pad, time bin, pad)
     to the reference histograms

 It is also possible to merge two independently taken calibrations using the function

 void Merge(AliTPCCalibPulser *sig)
   - copy histograms in 'sig' if the do not exist in this instance
   - Add histograms in 'sig' to the histograms in this instance if the allready exist
   - After merging call Analyse again!



 -- example: filling data using root raw data:
 void fillSignal(Char_t *filename)
 {
    rawReader = new AliRawReaderRoot(fileName);
    if ( !rawReader ) return;
    AliTPCCalibPulser *calib = new AliTPCCalibPulser;
    while (rawReader->NextEvent()){
      calib->ProcessEvent(rawReader);
    }
    calib->Analyse();
    calib->DumpToFile("SignalData.root");
    delete rawReader;
    delete calib;
 }


 What kind of information is stored and how to retrieve them:
 ------------------------------------------------------------

 - Accessing the 'Reference Histograms' (Time0, signal width and Q sum information pad by pad):

   TH2F *GetHistoT0(Int_t sector);
   TH2F *GetHistoRMS(Int_t sector);
   TH2F *GetHistoQ(Int_t sector);

 - Accessing the calibration storage objects:

   AliTPCCalROC *GetCalRocT0(Int_t sector);   // for the Time0 values
   AliTPCCalROC *GetCalRocRMS(Int_t sector);  // for the signal width values
   AliTPCCalROC *GetCalRocQ(Int_t sector);    // for the Q sum values

   example for visualisation:
   if the file "SignalData.root" was created using the above example one could do the following:

   TFile fileSignal("SignalData.root")
   AliTPCCalibPulser *sig = (AliTPCCalibPulser*)fileSignal->Get("AliTPCCalibPulser");
   sig->GetCalRocT0(0)->Draw("colz");
   sig->GetCalRocRMS(0)->Draw("colz");

   or use the AliTPCCalPad functionality:
   AliTPCCalPad padT0(ped->GetCalPadT0());
   AliTPCCalPad padSigWidth(ped->GetCalPadRMS());
   padT0->MakeHisto2D()->Draw("colz");       //Draw A-Side Time0 Information
   padSigWidth->MakeHisto2D()->Draw("colz"); //Draw A-Side signal width Information