During simulation: fill STU region w/ non null time sums
[u/mrichter/AliRoot.git] / TPC / AliTPCSpaceCharge.cxx
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c9cbd2f2 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. *
6 * *
7 * Permission to use, copy, modify and distribute this software and its *
8 * documentation strictly for non-commercial purposes is hereby granted *
9 * without fee, provided that the above copyright notice appears in all *
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
b4caed64 16// _________________________________________________________________
17//
18// Begin_Html
19// <h2> AliTPCSpaceCharge class </h2>
20// The class calculates the space point distortions due to a rotational
21// symmetric space charge distribution with the TPC drift volume.
22// <p>
23// The class uses the PoissonRelaxation2D to calculate the resulting
24// electrical field inhomogeneities in the (r,z)-plane. Then, the
25// Langevin-integral formalism is used to calculate the space point distortions.
26// <p>
27// The class assumes, that the distortions scales linearly with the magnitude
28// of the space charge distribution $\rho(r,z)$. The in here assumed distribution is
29// $$\rho(r,z) = \frac{(A-B\,z)}{r^2} $$ wherein the factors A and B scale with the
30// event multiplicity and the interaction rate.
31// <p>
32// The scaling factor can be set via the function SetCorrectionFactor. An example of
33// the shape of the distortions is given below.
34// End_Html
35//
6a1caa6b 36// Begin_Macro(source)
b4caed64 37// {
38// gROOT->SetStyle("Plain"); gStyle->SetPalette(1);
6a1caa6b 39// TCanvas *c2 = new TCanvas("cAliTPCSpaceCharge","cAliTPCSpaceCharge",500,300);
b4caed64 40// AliTPCSpaceCharge sc;
41// sc.SetOmegaTauT1T2(-0.32,1,1); // B=0.5 Tesla
42// sc.SetCorrectionFactor(0.0015);
43// sc.CreateHistoDRinZR(0.)->Draw("surf2");
44// return c2;
45// }
46// End_Macro
47//
48// Begin_Html
49// <p>
50// Date: 23/08/2010 <br>
51// Authors: Jim Thomas, Stefan Rossegger
52// End_Html
53// _________________________________________________________________
54
55
c9cbd2f2 56
57#include "AliMagF.h"
58#include "TGeoGlobalMagField.h"
59#include "AliTPCcalibDB.h"
60#include "AliTPCParam.h"
61#include "AliLog.h"
62#include "TMatrixD.h"
63
64#include "TMath.h"
65#include "AliTPCROC.h"
66#include "AliTPCSpaceCharge.h"
67
68ClassImp(AliTPCSpaceCharge)
69
70AliTPCSpaceCharge::AliTPCSpaceCharge()
71 : AliTPCCorrection("SpaceCharge2D","Space Charge 2D"),
72 fC0(0.),fC1(0.),fCorrectionFactor(0.001),
73 fInitLookUp(kFALSE)
74{
75 //
76 // default constructor
77 //
78
79}
80
81AliTPCSpaceCharge::~AliTPCSpaceCharge() {
82 //
83 // default destructor
84 //
85}
86
87
88
89void AliTPCSpaceCharge::Init() {
90 //
91 // Initialization funtion
92 //
93
94 AliMagF* magF= (AliMagF*)TGeoGlobalMagField::Instance()->GetField();
95 if (!magF) AliError("Magneticd field - not initialized");
96 Double_t bzField = magF->SolenoidField()/10.; //field in T
97 AliTPCParam *param= AliTPCcalibDB::Instance()->GetParameters();
98 if (!param) AliError("Parameters - not initialized");
99 Double_t vdrift = param->GetDriftV()/1000000.; // [cm/us] // From dataBase: to be updated: per second (ideally)
100 Double_t ezField = 400; // [V/cm] // to be updated: never (hopefully)
101 Double_t wt = -10.0 * (bzField*10) * vdrift / ezField ;
102 // Correction Terms for effective omegaTau; obtained by a laser calibration run
103 SetOmegaTauT1T2(wt,fT1,fT2);
104
105 InitSpaceChargeDistortion(); // fill the look up table
106}
107
108void AliTPCSpaceCharge::Update(const TTimeStamp &/*timeStamp*/) {
109 //
110 // Update function
111 //
112 AliMagF* magF= (AliMagF*)TGeoGlobalMagField::Instance()->GetField();
113 if (!magF) AliError("Magneticd field - not initialized");
114 Double_t bzField = magF->SolenoidField()/10.; //field in T
115 AliTPCParam *param= AliTPCcalibDB::Instance()->GetParameters();
116 if (!param) AliError("Parameters - not initialized");
117 Double_t vdrift = param->GetDriftV()/1000000.; // [cm/us] // From dataBase: to be updated: per second (ideally)
118 Double_t ezField = 400; // [V/cm] // to be updated: never (hopefully)
119 Double_t wt = -10.0 * (bzField*10) * vdrift / ezField ;
120 // Correction Terms for effective omegaTau; obtained by a laser calibration run
121 SetOmegaTauT1T2(wt,fT1,fT2);
122
123 // SetCorrectionFactor(1.); // should come from some database
124
125}
126
127
128
129void AliTPCSpaceCharge::GetCorrection(const Float_t x[],const Short_t roc,Float_t dx[]) {
130 //
131 // Calculates the correction due the Space Charge effect within the TPC drift volume
132 //
133
134 if (!fInitLookUp) {
135 AliInfo("Lookup table was not initialized! Perform the inizialisation now ...");
136 InitSpaceChargeDistortion();
137 }
138 Int_t order = 1 ; // FIXME: hardcoded? Linear interpolation = 1, Quadratic = 2
139
140 Double_t intEr, intEphi, intdEz;
141 Double_t r, phi, z ;
142 Int_t sign;
143
144 r = TMath::Sqrt( x[0]*x[0] + x[1]*x[1] ) ;
145 phi = TMath::ATan2(x[1],x[0]) ;
146 if ( phi < 0 ) phi += TMath::TwoPi() ; // Table uses phi from 0 to 2*Pi
147 z = x[2] ; // Create temporary copy of x[2]
148
149 if ( (roc%36) < 18 ) {
150 sign = 1; // (TPC A side)
151 } else {
152 sign = -1; // (TPC C side)
153 }
154
155 if ( sign==1 && z < fgkZOffSet ) z = fgkZOffSet; // Protect against discontinuity at CE
156 if ( sign==-1 && z > -fgkZOffSet ) z = -fgkZOffSet; // Protect against discontinuity at CE
157
158
159 if ( (sign==1 && z<0) || (sign==-1 && z>0) ) // just a consistency check
160 AliError("ROC number does not correspond to z coordinate! Calculation of distortions is most likely wrong!");
161
162 // Efield is symmetric in phi - 2D calculation
163 intEphi = 0.0;
164 // Get the E field integrals
165 Interpolate2DEdistortion( order, r, z, fLookUpErOverEz, intEr );
166 // Get DeltaEz field integral
167 Interpolate2DEdistortion( order, r, z, fLookUpDeltaEz, intdEz );
168
169
170 // Calculate distorted position
171 if ( r > 0.0 ) {
172 phi = phi + fCorrectionFactor *( fC0*intEphi - fC1*intEr ) / r;
173 r = r + fCorrectionFactor *( fC0*intEr + fC1*intEphi );
174 }
175 Double_t dz = intdEz*fCorrectionFactor;
176
177 // Calculate correction in cartesian coordinates
752b0cc7 178 dx[0] = - (r * TMath::Cos(phi) - x[0]);
179 dx[1] = - (r * TMath::Sin(phi) - x[1]);
180 dx[2] = - dz; // z distortion - (internally scaled with driftvelocity dependency
181 // on the Ez field
c9cbd2f2 182
183}
184
185void AliTPCSpaceCharge::InitSpaceChargeDistortion() {
186 //
187 // Initialization of the Lookup table which contains the solutions of the
188 // poisson problem
189 //
190
191 const Float_t gridSizeR = (fgkOFCRadius-fgkIFCRadius) / (kRows-1) ;
192 const Float_t gridSizeZ = fgkTPCZ0 / (kColumns-1) ;
193
194 TMatrixD voltArray(kRows,kColumns); // dummy boundary vectors
195 TMatrixD chargeDensity(kRows,kColumns); // charge
196 TMatrixD arrayErOverEz(kRows,kColumns); // solution in Er
197 TMatrixD arrayDeltaEz(kRows,kColumns); // solution in Ez
198
199 Double_t rList[kRows], zedList[kColumns] ;
200
201 // Fill arrays with initial conditions. V on the boundary and ChargeDensity in the volume.
202 for ( Int_t j = 0 ; j < kColumns ; j++ ) {
203 Double_t zed = j*gridSizeZ ;
204 zedList[j] = zed ;
205 for ( Int_t i = 0 ; i < kRows ; i++ ) {
206 Double_t radius = fgkIFCRadius + i*gridSizeR ;
207 rList[i] = radius ;
208 voltArray(i,j) = 0; // Initialize voltArray to zero - not used in this class
209 chargeDensity(i,j) = 0; // Initialize ChargeDensity to zero
210 }
211 }
212
213 // Fill the initial conditions
214 for ( Int_t j = 1 ; j < kColumns-1 ; j++ ) {
215 Double_t zed = j*gridSizeZ ;
216 for ( Int_t i = 1 ; i < kRows-1 ; i++ ) {
217 Double_t radius = fgkIFCRadius + i*gridSizeR ;
218
219 Double_t zterm = (fgkTPCZ0-zed) * (fgkOFCRadius*fgkOFCRadius - fgkIFCRadius*fgkIFCRadius) / fgkTPCZ0 ;
220 // for 1/R**2 charge density in the TPC; then integrated in Z due to drifting ions
221 chargeDensity(i,j) = zterm / ( TMath::Log(fgkOFCRadius/fgkIFCRadius) * ( radius*radius ) ) ;
222 }
223 }
224
225
226 // Solve the electrosatic problem in 2D
227
228 PoissonRelaxation2D( voltArray, chargeDensity, arrayErOverEz, arrayDeltaEz, kRows, kColumns, kIterations ) ;
229
230 //Interpolate results onto standard grid for Electric Fields
231 Int_t ilow=0, jlow=0 ;
232 Double_t z,r;
233 Float_t saveEr[2], saveEz[2] ;
234 for ( Int_t i = 0 ; i < kNZ ; ++i ) {
235 z = TMath::Abs( fgkZList[i] ) ; // assume symmetric behaviour on A and C side
236 for ( Int_t j = 0 ; j < kNR ; ++j ) {
237
238 // Linear interpolation !!
239 r = fgkRList[j] ;
240 Search( kRows, rList, r, ilow ) ; // Note switch - R in rows and Z in columns
241 Search( kColumns, zedList, z, jlow ) ;
242 if ( ilow < 0 ) ilow = 0 ; // check if out of range
243 if ( jlow < 0 ) jlow = 0 ;
244 if ( ilow + 1 >= kRows - 1 ) ilow = kRows - 2 ;
245 if ( jlow + 1 >= kColumns - 1 ) jlow = kColumns - 2 ;
246
247 saveEr[0] = arrayErOverEz(ilow,jlow) +
248 (arrayErOverEz(ilow,jlow+1)-arrayErOverEz(ilow,jlow))*(z-zedList[jlow])/gridSizeZ ;
249 saveEr[1] = arrayErOverEz(ilow+1,jlow) +
250 (arrayErOverEz(ilow+1,jlow+1)-arrayErOverEz(ilow+1,jlow))*(z-zedList[jlow])/gridSizeZ ;
251 saveEz[0] = arrayDeltaEz(ilow,jlow) +
252 (arrayDeltaEz(ilow,jlow+1)-arrayDeltaEz(ilow,jlow))*(z-zedList[jlow])/gridSizeZ ;
253 saveEz[1] = arrayDeltaEz(ilow+1,jlow) +
254 (arrayDeltaEz(ilow+1,jlow+1)-arrayDeltaEz(ilow+1,jlow))*(z-zedList[jlow])/gridSizeZ ;
255
256
257 fLookUpErOverEz[i][j] = saveEr[0] + (saveEr[1]-saveEr[0])*(r-rList[ilow])/gridSizeR ;
258 fLookUpDeltaEz[i][j] = saveEz[0] + (saveEz[1]-saveEz[0])*(r-rList[ilow])/gridSizeR ;
15687d71 259
260 if (fgkZList[i]<0) fLookUpDeltaEz[i][j] *= -1; // C side is negative z
c9cbd2f2 261 }
262 }
263
264 fInitLookUp = kTRUE;
265
266}
267
268void AliTPCSpaceCharge::Print(const Option_t* option) const {
269 //
270 // Print function to check the settings of the boundary vectors
271 // option=="a" prints the C0 and C1 coefficents for calibration purposes
272 //
273
274 TString opt = option; opt.ToLower();
275 printf("%s\n",GetTitle());
276 printf(" - Space Charge effects assuming a radial symmetric z over r^2 SC-distribution.\n");
277 printf(" SC correction factor: %f \n",fCorrectionFactor);
278
279 if (opt.Contains("a")) { // Print all details
280 printf(" - T1: %1.4f, T2: %1.4f \n",fT1,fT2);
281 printf(" - C1: %1.4f, C0: %1.4f \n",fC1,fC0);
282 }
283
284 if (!fInitLookUp) AliError("Lookup table was not initialized! You should do InitSpaceChargeDistortion() ...");
285
286}