Gabriele Cosmo
100 lines
3.8 KiB
C++
100 lines
3.8 KiB
C++
//
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// ********************************************************************
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// * License and Disclaimer *
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// * *
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// * The Geant4 software is copyright of the Copyright Holders of *
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// * the Geant4 Collaboration. It is provided under the terms and *
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// * conditions of the Geant4 Software License, included in the file *
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// * LICENSE and available at http://cern.ch/geant4/license . These *
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// * include a list of copyright holders. *
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// * *
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// * Neither the authors of this software system, nor their employing *
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// * institutes,nor the agencies providing financial support for this *
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// * work make any representation or warranty, express or implied, *
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// * regarding this software system or assume any liability for its *
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// * use. Please see the license in the file LICENSE and URL above *
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// * for the full disclaimer and the limitation of liability. *
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// * *
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// * This code implementation is the result of the scientific and *
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// * technical work of the GEANT4 collaboration. *
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// * By using, copying, modifying or distributing the software (or *
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// * any work based on the software) you agree to acknowledge its *
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// * use in resulting scientific publications, and indicate your *
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// * acceptance of all terms of the Geant4 Software license. *
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// ********************************************************************
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//
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//
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// $Id: G4DELPHIMagField.cc 96751 2016-05-04 09:39:38Z gcosmo $
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// -------------------------------------------------------------------
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#include "G4DELPHIMagField.hh"
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#include "globals.hh"
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#include "G4SystemOfUnits.hh"
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G4DELPHIMagField::G4DELPHIMagField()
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{
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}
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G4Field* G4DELPHIMagField::Clone() const
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{
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return new G4DELPHIMagField;
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}
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////////////////////////////////////////////////////////////////////////
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G4DELPHIMagField::~G4DELPHIMagField()
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{
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}
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///////////////////////////////////////////////////////////////////////
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void G4DELPHIMagField::GetFieldValue( const G4double yTrack[7],
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G4double B[3] ) const
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{
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G4int i, n = 8 ;
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G4double a = 0.001 ; // mm -> m
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G4double x = a*yTrack[0], y = a*yTrack[1], z = a*yTrack[2] ;
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G4double x2 = x*x, y2 = y*y, z2 = z*z, r2 = x2 + y2 ;
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G4double r4 = r2*r2, z4 = z2*z2, r6 = r4*r2, z6 = z4*z2 ;
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G4double r8 = r4*r4, z8 = z4*z4, r10 = r8*r2, z10 = z8*z2 ;
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G4double rz = z*std::sqrt(r2), r = std::sqrt(r2+a*a) ;
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G4double Br ;
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G4double P[8], Q[8] ;
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static G4ThreadLocal G4double c[8] = {
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-9.26e-5, -3.51e-5, 2.94e-6, -1.10e-6,
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6.25e-8, -1.77e-8, -6.88e-10, -7.52e-11
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} ;
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P[0] = 2*rz ;
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P[1] = 4*rz*(r2 - 4.0*z2/3.0) ;
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P[2] = 6*rz*(r4 - 4*r2*z2 + 1.6*z4) ;
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P[3] = 8*rz*(r6 - 8*r4*z2 + 9.6*r2*z4 - 64.0*z6/35.0) ;
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P[4] = 10*rz*(r8 - 40.0*r6*z2/3.0 + 32*r4*z4
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- 128.0*r2*z6/7.0 + 128.0*z8/63.0);
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P[5] = 0 ;
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P[6] = 0 ;
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P[7] = 0 ;
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Q[0] = r2 - 2*z2 ;
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Q[1] = r4 - 8*r2*z2 + 8.0*z4/3.0 ;
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Q[2] = r6 - 18*r4*z2 + 24*r2*z4 - 3.2*z6 ;
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Q[3] = r8 - 32*r6*z2 + 96*r4*z4 - 51.2*r2*z6 +128.0*z8/35.0 ;
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Q[4] = r10 - 50*r8*z2 + 800.0*r6*z4/3.0 - 320*r4*z6
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+ 640.0*r2*z8/7.0 - 256.0*z10/63.0 ;
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Q[5] = 0 ;
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Q[6] = 0 ;
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Q[7] = 0 ;
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Br = 0 ;
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B[2] = 1.2*tesla ; // the principal Bz value of DELPHI detector
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for(i=0;i<n;i++)
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{
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Br += c[i]*P[i] ;
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B[2] += c[i]*Q[i] ;
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}
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B[0] = Br*x/r ;
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B[1] = Br*y/r ;
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return ;
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}
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// -----------------------------------------------------------------
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