class AliTPCSpaceCharge: public AliTPCCorrection
AliTPCSpaceCharge class
The class calculates the space point distortions due to a rotational symmetric space charge distribution with the TPC drift volume.The class uses the PoissonRelaxation2D to calculate the resulting electrical field inhomogeneities in the (r,z)-plane. Then, the Langevin-integral formalism is used to calculate the space point distortions.
The class assumes, that the distortions scales linearly with the magnitude of the space charge distribution $\rho(r,z)$. The in here assumed distribution is $$\rho(r,z) = \frac{(A-B\,z)}{r^2} $$ wherein the factors A and B scale with the event multiplicity and the interaction rate.
The scaling factor can be set via the function SetCorrectionFactor. An example of the shape of the distortions is given below. MI modification - 22.05.2013 As an optional input the Space charge histogram RZ is used in case it is provided - using the SetInputSpaceCharge function
{
gROOT->SetStyle("Plain"); gStyle->SetPalette(1);
TCanvas *c2 = new TCanvas("cAliTPCSpaceCharge","cAliTPCSpaceCharge",500,300);
AliTPCSpaceCharge sc;
sc.SetOmegaTauT1T2(-0.32,1,1); // B=0.5 Tesla
sc.SetCorrectionFactor(0.0015);
sc.CreateHistoDRinZR(0.)->Draw("surf2");
return c2;
}
Date: 23/08/2010
Authors: Jim Thomas, Stefan Rossegger
Function Members (Methods)
public:
protected:
Data Members
public:
| enum { | kRows | |
| kColumns | ||
| kIterations | ||
| }; | ||
| enum AliTPCCorrection::CompositionType { | kParallel | |
| kQueue | ||
| }; | ||
| enum AliTPCCorrection::[unnamed] { | kNR | |
| kNPhi | ||
| kNZ | ||
| }; | ||
| enum TObject::EStatusBits { | kCanDelete | |
| kMustCleanup | ||
| kObjInCanvas | ||
| kIsReferenced | ||
| kHasUUID | ||
| kCannotPick | ||
| kNoContextMenu | ||
| kInvalidObject | ||
| }; | ||
| enum TObject::[unnamed] { | kIsOnHeap | |
| kNotDeleted | ||
| kZombie | ||
| kBitMask | ||
| kSingleKey | ||
| kOverwrite | ||
| kWriteDelete | ||
| }; |
protected:
| Int_t | AliTPCCorrection::fILow | |
| Bool_t | AliTPCCorrection::fIsLocal | switch to indicate that the distortion is a local vector drphi/dz, dr/dz |
| Int_t | AliTPCCorrection::fJLow | |
| Int_t | AliTPCCorrection::fKLow | variable to help in the interpolation |
| TString | TNamed::fName | object identifier |
| Double_t | AliTPCCorrection::fT1 | tensor term of wt - T1 |
| Double_t | AliTPCCorrection::fT2 | tensor term of wt - T2 |
| TString | TNamed::fTitle | object title |
| static TObjArray* | AliTPCCorrection::fgVisualCorrection | array of orrection for visualization |
| static const Double_t | AliTPCCorrection::fgkCathodeV | Cathode Voltage (volts) |
| static const Double_t | AliTPCCorrection::fgkEM | charge/mass in [C/kg] |
| static const Double_t | AliTPCCorrection::fgkGG | Gating Grid voltage (volts) |
| static const Double_t | AliTPCCorrection::fgkIFCRadius | Mean Radius of the Inner Field Cage ( 82.43 min, 83.70 max) (cm) |
| static const Double_t | AliTPCCorrection::fgkOFCRadius | Mean Radius of the Outer Field Cage (252.55 min, 256.45 max) (cm) |
| Double_t | AliTPCCorrection::fgkPhiList[181] | points in the phi direction (for the lookup table) |
| Double_t | AliTPCCorrection::fgkRList[72] | points in the radial direction (for the lookup table) |
| static const Double_t | AliTPCCorrection::fgkTPCZ0 | nominal gating grid position |
| Double_t | AliTPCCorrection::fgkZList[166] | points in the z direction (for the lookup table) |
| static const Double_t | AliTPCCorrection::fgkZOffSet | Offset from CE: calculate all distortions closer to CE as if at this point |
| static const Double_t | AliTPCCorrection::fgkdvdE | [cm/V] drift velocity dependency on the E field (from Magboltz for NeCO2N2 at standard environment) |
| static const Double_t | AliTPCCorrection::fgke0 | vacuum permittivity [A·s/(V·m)] |
private:
| Float_t | fC0 | coefficient C0 (compare Jim Thomas's notes for definitions) |
| Float_t | fC1 | coefficient C1 (compare Jim Thomas's notes for definitions) |
| Float_t | fCorrectionFactor | Space Charge Correction factor in comparison to initialized |
| Bool_t | fInitLookUp | flag to check it the Look Up table was created |
| Double_t | fLookUpDeltaEz[166][72] | Array to store electric field integral (int Delta Ez) |
| Double_t | fLookUpErOverEz[166][72] | Array to store electric field integral (int Er/Ez) |
| TH2* | fSpaceChargeHistogram | Histogram with the input space charge histogram - used as an optional input |
Class Charts
| Inheritance Chart: | ||||||||||||
|
Function documentation
void GetCorrection(const Float_t* x, const Short_t roc, Float_t* dx)
Calculates the correction due the Space Charge effect within the TPC drift volume
void InitSpaceChargeDistortion()
Initialization of the Lookup table which contains the solutions of the poisson problem
void Print(Option_t* option = "") const
Print function to check the settings of the boundary vectors option=="a" prints the C0 and C1 coefficents for calibration purposes
void SetOmegaTauT1T2(Float_t omegaTau, Float_t t1, Float_t t2)
common setters and getters for tangled ExB effect
void SetCorrectionFactor(Float_t correctionFactor)
setters and getters for conical
{fCorrectionFactor=correctionFactor;}