HelicalHarmonicField Class Reference

Inheritance diagram for HelicalHarmonicField:

Detailed Description

HelicalHarmonicField represents one placement of a helicalharmonic magnet.


Public Member Functions
	HelicalHarmonicField (BLCoordinateTransform &_global2local, BLCMDhelicalharmonic *hh)
	constructor.
void	addFieldValue (const G4double point[4], G4double field[6]) const
	addFieldValue() adds the field for this hh into field[]. point[] is in global coordinates.
Private Attributes
G4double	radius
G4double	halflength
int	n
G4double	b
G4double	lambda
G4double	phi0
BLCoordinateTransform	global2local
G4RotationMatrix	rotation

Constructor & Destructor Documentation

HelicalHarmonicField::HelicalHarmonicField	(	BLCoordinateTransform &	_global2local,
		BLCMDhelicalharmonic *	hh
	)

constructor.

References BLCMDhelicalharmonic::b, b, BLCoordinateTransform::getGlobal(), BLCoordinateTransform::getRotation(), global2local, halflength, BLCMDhelicalharmonic::lambda, lambda, BLCMDhelicalharmonic::length, BLCMDhelicalharmonic::n, n, BLCMDhelicalharmonic::phi0, phi0, BLCMDhelicalharmonic::radius, radius, rotation, and BLElementField::setGlobalPoint().

00307                                                                   :
00308                                         BLElementField(), rotation()
00309 {
00310         radius = hd->radius;
00311         halflength = hd->length/2.0;
00312         n = hd->n;
00313         b = hd->b;
00314         lambda = hd->lambda;
00315         phi0 = hd->phi0;
00316         global2local = _global2local;
00317         rotation = global2local.getRotation().inverse();
00318 
00319         // set global bounding box
00320         G4double local[4], global[4];
00321         local[3] = 0.0;
00322         for(int i=0; i<2; ++i) {
00323                 local[0] = (i==0 ? -1.0 : 1.0) * radius;
00324                 for(int j=0; j<2; ++j) {
00325                         local[1] = (j==0 ? -1.0 : 1.0) * radius;
00326                         for(int k=0; k<2; ++k) {
00327                                 local[2] = (k==0 ? -1.0 : 1.0) * halflength;
00328                                 global2local.getGlobal(local,global);
00329                                 setGlobalPoint(global);
00330                         }
00331                 }
00332         }
00333 }

Member Function Documentation

void HelicalHarmonicField::addFieldValue	(	const G4double	point[4],
		G4double	field[6]
	)			const `[virtual]`

addFieldValue() adds the field for this hh into field[]. point[] is in global coordinates.

Implements BLElementField.

References B, b, BLCoordinateTransform::getLocal(), global2local, halflength, BLCoordinateTransform::isRotated(), lambda, n, phi0, radius, and rotation.

00336 {
00337         const char *CoDE="HelicalHarmonicField::addFieldValue";
00338         const int X=0,Y=1,Z=2;
00339         const int PHI=0,RHO=1;                      /* notation */
00340 
00341         G4ThreeVector global(point[X],point[Y],point[Z]);
00342         G4ThreeVector local;
00343 
00344         global2local.getLocal(local,global);   /*fetch local location in mm*/
00345         G4double phi = atan2( local[Y], local[X]);
00346         G4double rho = sqrt( local[X]*local[X] + local[Y]*local[Y] );  /*mm*/
00347   
00348         if( rho>radius || fabs(local[Z]) > halflength)  return;
00349 
00350         G4double cosphi = cos(phi); 
00351         G4double sinphi = sin(phi); 
00352         G4double k = 2*pi/lambda; 
00353         G4double kz = k*(local[Z]+halflength); 
00354         G4double psi = n*(phi-kz+phi0); 
00355         G4double cospsi = cos(psi); 
00356         G4double sinpsi = sin(psi); 
00357         G4double nkrho = n*k*rho;
00358         G4double Inm1=gsl_sf_bessel_In(n-1,nkrho); 
00359         G4double In=gsl_sf_bessel_In(n,nkrho); 
00360         G4double Inp1=gsl_sf_bessel_In(n+1,nkrho); 
00361         G4double bb=b*pow(2/(n*k),(n-1)); 
00362         double Bcyl_phi=bb*(Inm1-Inp1)*cospsi; 
00363         double Bcyl_rho=bb*(Inm1+Inp1)*sinpsi;
00364         G4ThreeVector B;
00365         B[Z]=-2*bb*In*cospsi; 
00366         B[X]=Bcyl_rho*cosphi-Bcyl_phi*sinphi; 
00367         B[Y]=Bcyl_rho*sinphi+Bcyl_phi*cosphi;
00368 
00369         /* Rotation if applicable */ 
00370         if(global2local.isRotated())  B = rotation * B;
00371   
00372         field[0] += B[X];        /* update the field */
00373         field[1] += B[Y];
00374         field[2] += B[Z];
00375 }