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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 ////////////////////////////////////////////////////////////////////////////
38 #include "AliTPCExBBShape.h"
40 AliTPCExBBShape::AliTPCExBBShape()
41 : AliTPCCorrection("exb_bshape","ExB B-shape"),
46 // default constructor
50 AliTPCExBBShape::~AliTPCExBBShape() {
56 void AliTPCExBBShape::Init() {
58 // Initialization funtion (not used at the moment)
61 // Set default parameters
62 // FIXME: Ask the database for these entries
65 AliMagF * mag = new AliMagF("mag","mag"); // from database (GRP?)
68 Double_t vdrift = 2.6; // [cm/us] // From dataBase: to be updated: per second (ideally)
69 Double_t bzField = -0.5; // [Tesla] // From dataBase: to be updated: per run
71 Double_t ezField = 400; // [V/cm] // to be updated: never (hopefully)
72 Double_t wt = -10.0 * (bzField*10) * vdrift / ezField ;
74 // Correction Terms for effective omegaTau; obtained by a laser calibration run
75 Double_t t1 = 0.9; // ideally from database
76 Double_t t2 = 1.5; // ideally from database
78 SetOmegaTauT1T2(wt,t1,t2);
83 void AliTPCExBBShape::Update(const TTimeStamp &/*timeStamp*/) {
88 Double_t vdrift = 2.6; // [cm/us] // From dataBase: to be updated: per second (ideally)
89 Double_t bzField = -0.5; // [Tesla] // From dataBase: to be updated: per run
91 Double_t ezField = 400; // [V/cm] // to be updated: never (hopefully)
92 Double_t wt = -10.0 * (bzField*10) * vdrift / ezField ;
94 // Correction Terms for effective omegaTau; obtained by a laser calibration run
95 Double_t t1 = 0.9; // ideally from database
96 Double_t t2 = 1.5; // ideally from database
98 SetOmegaTauT1T2(wt,t1,t2);
105 void AliTPCExBBShape::GetCorrection(const Float_t x[],const Short_t roc,Float_t dx[]) {
107 // Calculates the space point corrections of the B field inperfections (B field shape)
111 for (Int_t j=0;j<3;++j) dx[j]=0.;
115 const Double_t xStart[3]={ x[0], x[1], x[2] };
116 const Double_t xEnd[3]={ x[0], x[1], roc%36<18?fgkTPC_Z0:-fgkTPC_Z0 };
118 Double_t intBStart[3];
121 fBField->GetTPCRatInt(xStart,intBStart);
122 fBField->GetTPCRatInt(xEnd, intBEnd );
124 const Float_t intBxOverBz=(intBEnd[0]-intBStart[0]);
125 const Float_t intByOverBz=(intBEnd[1]-intBStart[1]);
127 dx[0]=fC2*intBxOverBz-fC1*intByOverBz;
128 dx[1]=fC1*intBxOverBz+fC2*intByOverBz;
134 void AliTPCExBBShape::GetBxAndByOverBz(const Float_t x[],const Short_t roc,Float_t BxByOverBz[]) {
136 // This function is purely for calibration purposes
137 // Returns the via AliMagF obtaind B field integrals
141 for (Int_t j=0;j<3;++j) BxByOverBz[j]=0.;
145 const Double_t xStart[3]={ x[0], x[1], x[2] };
146 const Double_t xEnd[3]={ x[0], x[1], roc%36<18?fgkTPC_Z0:-fgkTPC_Z0 };
148 Double_t intBStart[3];
151 fBField->GetTPCRatInt(xStart,intBStart);
152 fBField->GetTPCRatInt(xEnd, intBEnd );
154 const Float_t intBxOverBz=(intBEnd[0]-intBStart[0]);
155 const Float_t intByOverBz=(intBEnd[1]-intBStart[1]);
157 BxByOverBz[0]=intBxOverBz;
158 BxByOverBz[1]=intByOverBz;
162 void AliTPCExBBShape::Print(Option_t* option) const {
164 // Print function to check the settings (e.g. voltage offsets)
165 // option=="a" prints details of the B field settings and the
166 // C0 and C1 coefficents (for calibration purposes)
168 TString opt = option; opt.ToLower();
169 printf("%s\n - B field settings:\n",GetTitle());
170 fBField->Print(option);
171 // printf(" - B field: X-Twist: %1.5lf rad, Y-Twist: %1.5lf rad \n",fBField->Print(option));
172 if (opt.Contains("a")) { // Print all details
173 printf(" - C1: %1.4f, C2: %1.4f \n",fC1,fC2);