TPC/AliTPCExBFirst.cxx

   1 /**************************************************************************
   2  * Copyright(c) 1998-1999, ALICE Experiment at CERN, All rights reserved. *
   3  *                                                                        *
   4  * Author: The ALICE Off-line Project.                                    *
   5  * Contributors are mentioned in the code where appropriate.              *
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  10  * copies and that both the copyright notice and this permission notice   *
  11  * appear in the supporting documentation. The authors make no claims     *
  12  * about the suitability of this software for any purpose. It is          *
  13  * provided "as is" without express or implied warranty.                  *
  14  **************************************************************************/
  15
  16 //
  17 // This implementation AliTPCExB is using an aproximate calculation of the ExB
  18 // effect. Therefore the drift ODE is Taylor expanded and only the first
  19 // order part is taken.
  20 //
  21 //
  22 // The ExB correction map is stored in the calib DB
  23 // To test current version:
  24 /*
  25   char *storage = "local://OCDBres"
  26   Int_t RunNumber=0;
  27   AliCDBManager::Instance()->SetDefaultStorage(storage);
  28   AliCDBManager::Instance()->SetRun(RunNumber)
  29   AliTPCExBFirst * exb = AliTPCcalibDB::Instance()->GetExB();
  30
  31   //  exb->TestExB("exb.root");
  32   // TFile f("exb.root");
  33   //positions->Draw("drphi");
  34 */
  35
  36
  37
  38 #include "TMath.h"
  39 #include "AliFieldMap.h"
  40 #include "AliMagF.h"
  41 #include "TTreeStream.h"
  42 #include "AliTPCExBFirst.h"
  43
  44 ClassImp(AliTPCExBFirst)
  45
  46 const Double_t AliTPCExBFirst::fgkEM=1.602176487e-19/9.10938215e-31;
  47 const Double_t AliTPCExBFirst::fgkDriftField=40.e3;
  48
  49 AliTPCExBFirst::AliTPCExBFirst()
  50   : fDriftVelocity(0),
  51     fkNX(0),fkNY(0),fkNZ(0),
  52     fkXMin(-250.),fkXMax(250.),fkYMin(-250.),fkYMax(250.),
  53     fkZMin(-250.),fkZMax(250.),
  54     fkNMean(0),
  55     fkMeanBx(0),fkMeanBy(0),fkMeanBz(0.) {
  56   //
  57   // purely for I/O
  58   //
  59   SetInstance(this);
  60 }
  61
  62 AliTPCExBFirst::AliTPCExBFirst(const AliMagF *bField,
  63                                Double_t driftVelocity,
  64                                Int_t nx,Int_t ny,Int_t nz)
  65   : fDriftVelocity(driftVelocity),
  66     fkNX(nx),fkNY(ny),fkNZ(nz),
  67     fkXMin(-250.),fkXMax(250.),fkYMin(-250.),fkYMax(250.),
  68     fkZMin(-250.),fkZMax(250.),
  69     fkNMean(0),
  70     fkMeanBx(0),fkMeanBy(0),fkMeanBz(0.) {
  71   //
  72   // The constructor. One has to supply a magnetic field and an (initial)
  73   // drift velocity. Since some kind of lookuptable is created the
  74   // number of its meshpoints can be supplied.
  75   //
  76   ConstructCommon(0,bField);
  77   SetInstance(this);
  78 }
  79
  80 AliTPCExBFirst::AliTPCExBFirst(const AliFieldMap *bFieldMap,
  81                                Double_t driftVelocity)
  82   : fDriftVelocity(driftVelocity),
  83     fkNX(0),fkNY(0),fkNZ(0),
  84     fkXMin(-250.),fkXMax(250.),fkYMin(-250.),fkYMax(250.),
  85     fkZMin(-250.),fkZMax(250.),
  86     fkNMean(0),
  87     fkMeanBx(0),fkMeanBy(0),fkMeanBz(0.) {
  88   //
  89   // The constructor. One has to supply a field map and an (initial)
  90   // drift velocity.
  91   //
  92   SetInstance(this);
  93   fkXMin=bFieldMap->Xmin()
  94     -TMath::Ceil( (bFieldMap->Xmin()+250.0)/bFieldMap->DelX())
  95     *bFieldMap->DelX();
  96   fkXMax=bFieldMap->Xmax()
  97     -TMath::Floor((bFieldMap->Xmax()-250.0)/bFieldMap->DelX())
  98     *bFieldMap->DelX();
  99   fkYMin=bFieldMap->Ymin()
 100     -TMath::Ceil( (bFieldMap->Ymin()+250.0)/bFieldMap->DelY())
 101     *bFieldMap->DelY();
 102   fkYMax=bFieldMap->Ymax()
 103     -TMath::Floor((bFieldMap->Ymax()-250.0)/bFieldMap->DelY())
 104     *bFieldMap->DelY();
 105   fkZMin=bFieldMap->Zmin()
 106     -TMath::Ceil( (bFieldMap->Zmin()+250.0)/bFieldMap->DelZ())
 107     *bFieldMap->DelZ();
 108   fkZMax=bFieldMap->Zmax()
 109     -TMath::Floor((bFieldMap->Zmax()-250.0)/bFieldMap->DelZ())
 110     *bFieldMap->DelZ();
 111
 112   fkNX=static_cast<Int_t>((fkXMax-fkXMin)/bFieldMap->DelX()+1.1);
 113   fkNY=static_cast<Int_t>((fkYMax-fkYMin)/bFieldMap->DelY()+1.1);
 114   fkNZ=static_cast<Int_t>((fkZMax-fkZMin)/bFieldMap->DelZ()+1.1);
 115
 116   ConstructCommon(bFieldMap,0);
 117 }
 118
 119 AliTPCExBFirst::~AliTPCExBFirst() {
 120   //
 121   // destruct the poor object.
 122   //
 123   delete[] fkMeanBx;
 124   delete[] fkMeanBy;
 125 }
 126
 127 void AliTPCExBFirst::Correct(const Double_t *position,Double_t *corrected) {
 128   //
 129   // correct for the distortion
 130   //
 131   Double_t bx,by;
 132   GetMeanFields(position[0],position[1],position[2],&bx,&by);
 133   if (position[2]>0.) {
 134     Double_t bxe,bye;
 135     GetMeanFields(position[0],position[1],250.,&bxe,&bye);
 136     if (position[2]!=250.) {
 137       bx=(500.*bxe-(position[2]+250.)*bx)/(250.-position[2]);
 138       by=(500.*bye-(position[2]+250.)*by)/(250.-position[2]);
 139     }
 140     else {
 141       bx=bxe;
 142       by=bye;
 143     }
 144   }
 145
 146   Double_t mu=fDriftVelocity/fgkDriftField;
 147   Double_t wt=mu*fkMeanBz;
 148
 149   corrected[0]=mu*(wt*bx-by)/(1.+wt*wt);
 150   corrected[1]=mu*(wt*by+bx)/(1.+wt*wt);
 151
 152   if (position[2]>0.) {
 153     corrected[0]*=(250.-position[2]);
 154     corrected[1]*=(250.-position[2]);
 155   }
 156   else {
 157     corrected[0]*=(-250.-position[2]);
 158     corrected[1]*=(-250.-position[2]);
 159   }
 160
 161   corrected[0]=position[0]-corrected[0];
 162   corrected[1]=position[1]-corrected[1];
 163   corrected[2]=position[2];
 164 }
 165
 166 void AliTPCExBFirst::TestThisBeautifulObject(const char* fileName) {
 167   //
 168   // well, as the name sais...
 169   //
 170   TTreeSRedirector ts(fileName);
 171   Double_t x[3];
 172   for (x[0]=-250.;x[0]<=250.;x[0]+=10.)
 173     for (x[1]=-250.;x[1]<=250.;x[1]+=10.)
 174       for (x[2]=-250.;x[2]<=250.;x[2]+=10.) {
 175         Double_t d[3];
 176         Correct(x,d);
 177         Double_t r=TMath::Sqrt(x[0]*x[0]+x[1]*x[1]);
 178         Double_t rd=TMath::Sqrt(d[0]*d[0]+d[1]*d[1]);
 179         Double_t dr=r-rd;
 180         Double_t phi=TMath::ATan2(x[0],x[1]);
 181         Double_t phid=TMath::ATan2(d[0],d[1]);
 182         Double_t dphi=phi-phid;
 183         if (dphi<0.) dphi+=TMath::TwoPi();
 184         if (dphi>TMath::Pi()) dphi=TMath::TwoPi()-dphi;
 185         Double_t drphi=r*dphi;
 186         Double_t dx=x[0]-d[0];
 187         Double_t dy=x[1]-d[1];
 188         Double_t dz=x[2]-d[2];
 189         ts<<"positions"
 190           <<"x0="<<x[0]
 191           <<"x1="<<x[1]
 192           <<"x2="<<x[2]
 193           <<"dx="<<dx
 194           <<"dy="<<dy
 195           <<"dz="<<dz
 196           <<"r="<<r
 197           <<"phi="<<phi
 198           <<"dr="<<dr
 199           <<"drphi="<<drphi
 200           <<"\n";
 201       }
 202 }
 203
 204 void AliTPCExBFirst::ConstructCommon(const AliFieldMap *bFieldMap,
 205                                      const AliMagF *bField) {
 206   //
 207   // THIS IS PRIVATE! (a helper for the constructor)
 208   //
 209   fkNMean=fkNX*fkNY*fkNZ;
 210   fkMeanBx=new Double_t[fkNMean];
 211   fkMeanBy=new Double_t[fkNMean];
 212
 213   Double_t x[3];
 214   Double_t nBz=0;
 215   fkMeanBz=0.;
 216   for (int i=0;i<fkNX;++i) {
 217     x[0]=fkXMin+i*(fkXMax-fkXMin)/(fkNX-1);
 218     for (int j=0;j<fkNY;++j) {
 219       x[1]=fkYMin+j*(fkYMax-fkYMin)/(fkNY-1);
 220       Double_t r=TMath::Sqrt(x[0]*x[0]+x[1]*x[1]);
 221       Double_t bx=0.,by=0.;
 222       for (int k=0;k<fkNZ;++k) {
 223         x[2]=fkZMin+k*(fkZMax-fkZMin)/(fkNZ-1);
 224         Float_t b[3];
 225         // the x is not const in the Field function...
 226         Float_t xt[3];
 227         for (int l=0;l<3;++l) xt[l]=x[l];
 228         // that happens due to the lack of a sophisticated class design:
 229         if (bFieldMap!=0)
 230           bFieldMap->Field(xt,b);
 231         else
 232           bField->Field(xt,b);
 233         bx+=b[0]/10.;
 234         by+=b[1]/10.;
 235         fkMeanBx[(k*fkNY+j)*fkNX+i]=bx;
 236         fkMeanBy[(k*fkNY+j)*fkNX+i]=by;
 237         if (90.<=r&&r<=250.) {
 238           fkMeanBz+=b[2]/10.;
 239           ++nBz;
 240         }
 241       }
 242     }
 243   }
 244   fkMeanBz/=nBz;
 245 }
 246
 247 void AliTPCExBFirst::GetMeanFields(Double_t rx,Double_t ry,Double_t rz,
 248                                    Double_t *Bx,Double_t *By) const {
 249   //
 250   // THIS IS PRIVATE! (calculates the mean field utilising a lookup table)
 251   //
 252   Double_t x=(fkNX-1)*(rx-fkXMin)/(fkXMax-fkXMin);
 253   Int_t xi1=static_cast<Int_t>(x);
 254   xi1=TMath::Max(TMath::Min(xi1,fkNX-2),0);
 255   Int_t xi2=xi1+1;
 256   Double_t dx=(x-xi1);
 257   Double_t dx1=(xi2-x);
 258
 259   Double_t y=(fkNY-1)*(ry-fkYMin)/(fkYMax-fkYMin);
 260   Int_t yi1=static_cast<Int_t>(y);
 261   yi1=TMath::Max(TMath::Min(yi1,fkNY-2),0);
 262   Int_t yi2=yi1+1;
 263   Double_t dy=(y-yi1);
 264   Double_t dy1=(yi2-y);
 265
 266   Double_t z=(fkNZ-1)*(rz-fkZMin)/(fkZMax-fkZMin);
 267   Int_t zi1=static_cast<Int_t>(z);
 268   zi1=TMath::Max(TMath::Min(zi1,fkNZ-2),0);
 269   Int_t zi2=zi1+1;
 270   Double_t dz=(z-zi1);
 271
 272   double s0x=fkMeanBx[yi1*fkNX+xi1]*dx1*dy1
 273             +fkMeanBx[yi2*fkNX+xi1]*dx1*dy
 274             +fkMeanBx[yi1*fkNX+xi2]*dx *dy
 275             +fkMeanBx[yi2*fkNX+xi2]*dx *dy1;
 276   double s0y=fkMeanBy[yi1*fkNX+xi1]*dx1*dy1
 277             +fkMeanBy[yi2*fkNX+xi1]*dx1*dy
 278             +fkMeanBy[yi1*fkNX+xi2]*dx *dy
 279             +fkMeanBy[yi2*fkNX+xi2]*dx *dy1;
 280   Int_t zi0=zi1-1;
 281   double snmx,snmy;
 282   if (zi0>=0) {
 283     snmx=fkMeanBx[(zi0*fkNY+yi1)*fkNX+xi1]*dx1*dy1
 284         +fkMeanBx[(zi0*fkNY+yi2)*fkNX+xi1]*dx1*dy
 285         +fkMeanBx[(zi0*fkNY+yi1)*fkNX+xi2]*dx *dy
 286         +fkMeanBx[(zi0*fkNY+yi2)*fkNX+xi2]*dx *dy1;
 287     snmy=fkMeanBy[(zi0*fkNY+yi1)*fkNX+xi1]*dx1*dy1
 288         +fkMeanBy[(zi0*fkNY+yi2)*fkNX+xi1]*dx1*dy
 289         +fkMeanBy[(zi0*fkNY+yi1)*fkNX+xi2]*dx *dy
 290         +fkMeanBy[(zi0*fkNY+yi2)*fkNX+xi2]*dx *dy1;
 291   }
 292   else
 293     snmx=snmy=0.;
 294   double snx=fkMeanBx[(zi1*fkNY+yi1)*fkNX+xi1]*dx1*dy1
 295             +fkMeanBx[(zi1*fkNY+yi2)*fkNX+xi1]*dx1*dy
 296             +fkMeanBx[(zi1*fkNY+yi1)*fkNX+xi2]*dx *dy
 297             +fkMeanBx[(zi1*fkNY+yi2)*fkNX+xi2]*dx *dy1;
 298   double sny=fkMeanBy[(zi1*fkNY+yi1)*fkNX+xi1]*dx1*dy1
 299             +fkMeanBy[(zi1*fkNY+yi2)*fkNX+xi1]*dx1*dy
 300             +fkMeanBy[(zi1*fkNY+yi1)*fkNX+xi2]*dx *dy
 301             +fkMeanBy[(zi1*fkNY+yi2)*fkNX+xi2]*dx *dy1;
 302   double snpx=fkMeanBx[(zi2*fkNY+yi1)*fkNX+xi1]*dx1*dy1
 303              +fkMeanBx[(zi2*fkNY+yi2)*fkNX+xi1]*dx1*dy
 304              +fkMeanBx[(zi2*fkNY+yi1)*fkNX+xi2]*dx *dy
 305              +fkMeanBx[(zi2*fkNY+yi2)*fkNX+xi2]*dx *dy1;
 306   double snpy=fkMeanBy[(zi2*fkNY+yi1)*fkNX+xi1]*dx1*dy1
 307              +fkMeanBy[(zi2*fkNY+yi2)*fkNX+xi1]*dx1*dy
 308              +fkMeanBy[(zi2*fkNY+yi1)*fkNX+xi2]*dx *dy
 309              +fkMeanBy[(zi2*fkNY+yi2)*fkNX+xi2]*dx *dy1;
 310   *Bx=0.5*(((snpx-2.*snx+snmx)*dz+2.*(snx-snmx))*dz+snx-s0x+snmx);
 311   *By=0.5*(((snpy-2.*sny+snmy)*dz+2.*(sny-snmy))*dz+sny-s0y+snmy);
 312   //TODO: make this nice
 313   if (TMath::Abs(z)>0.001) {
 314     *Bx/=z;
 315     *By/=z;
 316   }
 317 }