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Implemented proper beam direction and beam spot rotation as determined by /gun/direction command.

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This commit is contained in:
salman
2011-01-04 12:14:01 +00:00
parent 117790a661
commit dcc8c6119d
1 changed files with 23 additions and 3 deletions
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26
src/musrPrimaryGeneratorAction.cc
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@ -271,8 +271,10 @@ void musrPrimaryGeneratorAction::GeneratePrimaries(G4Event* anEvent)
G4double px, py, pz;
px = p*sin(xangle);
py = p*sin(yangle);
// works for beam along +-z only for now
pz = zDirection * std::sqrt(p*p - px*px - py*py);
pz = std::sqrt(p*p - px*px - py*py);
// Now rotate so that beam propagates along /gun/direction
// Proper rotation of beam direction as follows:
// hat{n} is beam direction unit vecrot and vec{p} is momentum vector
@ -280,7 +282,25 @@ void musrPrimaryGeneratorAction::GeneratePrimaries(G4Event* anEvent)
// where R is a rotation matrix around (hat{z} x hat{n}) - cross product
// with an angle of acos(hat{z} dot hat{n}) - dot product
// i.e. R is a rotation around (-n_y, n_x, 0) with angle acos(n_z).
// G4RotationMatrix* R = new G4RotationMatrix(G4ThreeVector(-nx,ny,0),acos(nz)*deg);
if (xDirection == 0 & yDirection == 0) {
// Rotation does not work for beam direction along z.
pz = zDirection * pz;
// No change to the beam spot...
} else {
G4ThreeVector* PVec = new G4ThreeVector(px,py,pz);
PVec->rotate(std::acos(zDirection),G4ThreeVector(-yDirection,xDirection,0));
px = PVec->x();
py = PVec->y();
pz = PVec->z();
// Rotate also beam spot
G4ThreeVector* RVec = new G4ThreeVector(x-x0,y-y0,z-z0);
RVec->rotate(std::acos(zDirection),G4ThreeVector(-yDirection,xDirection,0));
x = x0+RVec->x();
y = y0+RVec->y();
z = z0+RVec->z();
}
// Assign spin
G4double xpolaris=0, ypolaris=0, zpolaris=0;