1 /**************************************************************************
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4 * Author: The ALICE Off-line Project. *
5 * Contributors are mentioned in the code where appropriate. *
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14 **************************************************************************/
16 ////////////////////////////////////////////////////////////////////////////
18 // AliExBBShape class //
19 // The class calculates the space point distortions due to the B field //
20 // shape imperfections using a second order technique based on integrals //
21 // over Bz (e.g. int By/Bz) obtained via the AliMagF class //
22 // The class allows "effective Omega Tau" corrections. //
24 // date: 27/04/2010 //
25 // Authors: Magnus Mager, Jim Thomas, Stefan Rossegger //
28 // AliMagF mag("mag","mag"); //
29 // AliTPCExBBShape exb; //
30 // exb.SetBField(&mag); // use Bfield from AliMagF //
31 // exb.SetOmegaTauT1T2(0.32,1.,1.); // values ideally from OCDB //
32 // // plot dRPhi distortions ... //
33 // exb.CreateHistoDRPhiinZR(0,100,100)->Draw("surf2"); //
34 ////////////////////////////////////////////////////////////////////////////
37 #include "TGeoGlobalMagField.h"
38 #include "AliTPCcalibDB.h"
39 #include "AliTPCParam.h"
42 #include "AliTPCExBBShape.h"
44 AliTPCExBBShape::AliTPCExBBShape()
45 : AliTPCCorrection("exb_bshape","ExB B-shape"),
50 // default constructor
54 AliTPCExBBShape::~AliTPCExBBShape() {
60 void AliTPCExBBShape::Init() {
62 // Initialization funtion
65 AliMagF* magF= (AliMagF*)TGeoGlobalMagField::Instance()->GetField();
66 if (!magF) AliError("Magneticd field - not initialized");
67 Double_t bzField = magF->SolenoidField()/10.; //field in T
69 AliTPCParam *param= AliTPCcalibDB::Instance()->GetParameters();
70 if (!param) AliError("Parameters - not initialized");
71 Double_t vdrift = param->GetDriftV()/1000000.; // [cm/us] // From dataBase: to be updated: per second (ideally)
72 Double_t ezField = 400; // [V/cm] // to be updated: never (hopefully)
73 Double_t wt = -10.0 * (bzField*10) * vdrift / ezField ;
74 // Correction Terms for effective omegaTau; obtained by a laser calibration run
75 SetOmegaTauT1T2(wt,fT1,fT2);
80 void AliTPCExBBShape::Update(const TTimeStamp &/*timeStamp*/) {
84 AliMagF* magF= (AliMagF*)TGeoGlobalMagField::Instance()->GetField();
85 if (!magF) AliError("Magneticd field - not initialized");
86 Double_t bzField = magF->SolenoidField()/10.; //field in T
88 AliTPCParam *param= AliTPCcalibDB::Instance()->GetParameters();
89 if (!param) AliError("Parameters - not initialized");
90 Double_t vdrift = param->GetDriftV()/1000000.; // [cm/us] // From dataBase: to be updated: per second (ideally)
91 Double_t ezField = 400; // [V/cm] // to be updated: never (hopefully)
92 Double_t wt = -10.0 * (bzField*10) * vdrift / ezField ;
93 // Correction Terms for effective omegaTau; obtained by a laser calibration run
94 SetOmegaTauT1T2(wt,fT1,fT2);
101 void AliTPCExBBShape::GetCorrection(const Float_t x[],const Short_t roc,Float_t dx[]) {
103 // Calculates the space point corrections of the B field inperfections (B field shape)
107 for (Int_t j=0;j<3;++j) dx[j]=0.;
111 const Double_t xStart[3]={ x[0], x[1], x[2] };
112 const Double_t xEnd[3]={ x[0], x[1], roc%36<18?fgkTPCZ0:-fgkTPCZ0 };
114 Double_t intBStart[3];
117 fBField->GetTPCRatInt(xStart,intBStart);
118 fBField->GetTPCRatInt(xEnd, intBEnd );
120 const Float_t intBxOverBz=(intBEnd[0]-intBStart[0]);
121 const Float_t intByOverBz=(intBEnd[1]-intBStart[1]);
123 dx[0]=fC2*intBxOverBz-fC1*intByOverBz;
124 dx[1]=fC1*intBxOverBz+fC2*intByOverBz;
130 void AliTPCExBBShape::GetBxAndByOverBz(const Float_t x[],const Short_t roc,Float_t BxByOverBz[]) {
132 // This function is purely for calibration purposes
133 // Returns the via AliMagF obtaind B field integrals
137 for (Int_t j=0;j<3;++j) BxByOverBz[j]=0.;
141 const Double_t xStart[3]={ x[0], x[1], x[2] };
142 const Double_t xEnd[3]={ x[0], x[1], roc%36<18?fgkTPCZ0:-fgkTPCZ0 };
144 Double_t intBStart[3];
147 fBField->GetTPCRatInt(xStart,intBStart);
148 fBField->GetTPCRatInt(xEnd, intBEnd );
150 const Float_t intBxOverBz=(intBEnd[0]-intBStart[0]);
151 const Float_t intByOverBz=(intBEnd[1]-intBStart[1]);
153 BxByOverBz[0]=intBxOverBz;
154 BxByOverBz[1]=intByOverBz;
158 void AliTPCExBBShape::Print(Option_t* option) const {
160 // Print function to check the settings (e.g. voltage offsets)
161 // option=="a" prints details of the B field settings and the
162 // C0 and C1 coefficents (for calibration purposes)
164 TString opt = option; opt.ToLower();
165 printf("%s\t%s\n - B field settings:\n",GetTitle(),GetName());
166 fBField->Print(option);
167 // printf(" - B field: X-Twist: %1.5lf rad, Y-Twist: %1.5lf rad \n",fBField->Print(option));
168 if (opt.Contains("a")) { // Print all details
169 printf(" - T1: %1.4f, T2: %1.4f \n",fT1,fT2);
170 printf(" - C1: %1.4f, C2: %1.4f \n",fC1,fC2);