BLFieldMap Class Reference

#include <BLFieldMap.hh>

List of all members.

---

Detailed Description

class BLFieldMap implements a general field map, both B and E.

Initially this class simply reads an input file to define the map. Eventually it will also generate a map automatically from a BLCoil, and from an arbitrary collection of magnets (to improve tracking efficiency for a large number of overlapping solenoids).

Field components are interpolated in the map; the values used are: Bx = (interpolated value)*normB*(element_current/current_param) Ex = (interpolated value)*normE*(element_gradient/gradient_param) [other components are similar] where element_current and element_gradient are from the element definition command in the input file, and normB, normE, curren_param, and gradient_param come from the input file. The presence of both norm and current/gradient in the input file is to accommodate diverse sources of input files and units.

Outside the map the fields are zero, so if the map is truncated you should ensure that no particles are tracked outside the map in that region. This happens, for instance, for a beam solenoid truncated in radius to the inside of the coil -- particles which enter the coil will see a zero field, so the coil should be set to kill them; particles outside the map along z but inside the bore will also see a zero field, but that is usually OK as long as the map extends far enough along Z to include the nonzero field region.

Input File format: Blank lines, and lines beginning with # or * are comments. Lines beginning with * are printed to stdout. Units are mm for coordinates, Tesla for B, and MegaVolts/meter for E; use normB and normE if the data points use different units.

The input file starts with a set of commands to define the parameters of the map, followed by blocks of lines containing the values of the field components. The field component names depend on the type of map (grid: Bx,By,Bz,Ex,Ey,Ez; cylinder: Br,Bz,Er,Ez). Each command has a specific list of arguments to define parameters of the map.

BEWARE: the parsing is not exhaustive. For instance, invalid arguments are silently ignored (which means you must verify the spelling and capitalization of argument names). Correct inputs will yield correct results, but invalid inputs may not be detected and may yield seemingly-correct but unintended results.

The first command is usually a param command, which has the following arguments: maxline The maximum number of characters per line (default=1023) current The current corresponding to this map (default=1.0) gradient The gradient corresponding to the map (default=1.0) normE A normalization factor for E components (default=1.0) normB A normalization factor for B components (default=1.0)

Two types of maps are implemented: grid and cylinder.

grid maps are a 3-D grid, with each block of data being a single X-Y plane; within a block the lines are Y and the columns of each line are values along X. The grid command has the following arguments: X0 The X value for the first value in each line Y0 The Y value for the first line in each block Z0 The Z value for the first block of each field component nX The number of columns per line nY The number of lines per block nZ The number of blocks per field component dX The X increment between values in each line dY The Y increment between lines dZ The Z increment between blocks tolerance The tolerance for pointwise data (default=0.01 mm) After the grid command, the following optional commands can be given: extendX flip=... extendY flip=... extendZ flip=... These commands permit a half-map to be extended to the full map around X=0, Y=0, or Z=0 respectively. The optional flip argument is a comma-separated list of field components whose signs will be inverted for negative values of the coordinate. For example, "extendZ flip=Bx,Ex" means the map from Z=0 to Z=(nZ-1)*dZ is extended symmetrically around Z=0 to negative Z values, flipping the signs of Bx and Ex when Z<0. This could be followed by "extendX flip=Bx,Ex", and the field flips will be the products of both commands.

cylinder maps are a 2-D map with rotational symmetry around the Z axis. Each field component has a single block with lines being Z and the columns being R. The cylinder command has the following arguments: Z0 The Z value for the first line in each block nR The number of columns per line nZ The number of lines per block dR The R increment between colums dZ The Z increment between lines tolerance The tolerance for pointwise data (default=0.01 mm) After the cylinder command, the following optional commands can be given: extendZ flip=... This command behaves the same as for the grid map.

After the commands, each block consists of a line containing the name of the field component, followed by the lines of the block. The values within a line can be separated by whitespace or a ',' followed by optional whitespace. Field components that are not given are set to 0.0 everywhere. Missing values will be considered to be 0.0. For grid maps the first block is for Z=Z0, and successive blocks increment Z by dZ; the first line in a block is for Y=Y0 and the first column in each line is for X=X0. For cylinder maps, the first line in each block is for Z=Z0 and the first column in each line is for R=0.

Instead of the blocked input format, a pointwise data format can be used. This is introduced by a line containing the command "data", followed by the individual points of the map, one per line. for a grid field, each line contains values for X,Y,Z,Bx,By,Bz,Ex,Ey,Ez separated by either a comma and optional whitespece or by whitespace. for a cylinder field each line contains values for R,Z,Br,Bz,Er,Ez. The order of the points does not matter; omitted grid points will be 0.0, and for duplicates the last entry wins. If there is no E field, the Ex,Ey,Ez or Er,Ez entries should be omitted on every line. NOTE: every line's X,Y,Z or R,Z must be on a grid point as specified by the arguments to the grid or cylinder commands, to within the tolerance specified; if not, an error message is printed and the input line is ignored.

For time=dependent fields, the "time" command is used: time [period=12] period, if given, is in nanoseconds, and causes the interval [0,period) to be extended forever (before and after the values given). Because of the interpolation used, at least two points beyond the interval boundaries should be provided; there need not be a point at either boundary (but usually there are). Following the time command are lines containing 2 or 3 doubles: t B E where t is the time (nanoseconds), and B and E are factors for the fields. If E is omitted, the value for B is used. These values will be interpolated in time with a cubic spline that can handle either uniform or non-uniform spacing of points along t. The time command can come either before or after the cylinder or grid commands, but not within either of their sequences. Note a cubic spline is used to interpolate between points, and that can cause over/under-shoot near an abrupt change. Combined with period= this gives an excellent representation of sinewave/cosinewave.

Note that time dependence can currently only be specified via the time command in an input file (i.e. not programmable method exists).

Example block input file: * this is an example BLFieldMap input file, suitable for a solenoid # grid interval is 1 cm. # The region of validity is -390<=Z<=390 and 0<=R<=90 param normB=1.0 current=1.0 cylinder Z0=0.0 nR=10 nZ=40 dR=10.0 dZ=10.0 extendZ flip=Br Bz ... 40 lines of 10 values, Z=0 thru Z=390 Br ... 40 lines of 10 values, Z=0 thru Z=390 --EOF--

Example pointwise input file: * this is an example BLFieldMap input file, suitable for a solenoid # grid interval is 1 cm. # The region of validity is -390<=Z<=390 and 0<=R<=90 param normB=1.0 current=1.0 cylinder Z0=0.0 nR=10 nZ=40 dR=10.0 dZ=10.0 extendZ flip=Br data ... 400 lines of 4 values, giving R,Z,Br,Bz --EOF--

Public Member Functions
	BLFieldMap ()
	default constructor.
virtual	~BLFieldMap ()
	destructor.
bool	readFile (G4String filename)
	readFile() reads a file to initialize the map. Returns true if OK, false on error.
bool	writeFile (G4String filename, G4String comment="")
	writeFile() writes the map to a file. Returns true if OK, false on error.
void	getFieldValue (const G4double local[4], G4double field[6], G4double current=1.0, G4double gradient=1.0)
	getFieldValue() gets the map's field to the field[] array. local[] must be LOCAL coordinates; local[3] (time) is ignored unless there is a time dependence specified. (elements using BLFieldMap perform the global->local conversion)
void	getFieldValueNoTimeNoScale (const G4double local[4], G4double field[6])
	getFieldValueNoTimeNoScale() as above, except no time dependence is applies, and no scaling is performed.
void	getBoundingPoint (int i, G4double point[4])
	getBoundingPoint() returns the i-th bounding point of the map.
bool	hasB ()
	hasB() returns true if this map has a nonzero B field.
bool	hasE ()
	hasE() returns true if this map has a nonzero E field.
bool	createGridMap (G4double X0, G4double Y0, G4double Z0, G4double dX, G4double dY, G4double dZ, int nX, int nY, int nZ, class G4ElectroMagneticField *field)
	createGridMap() will create a 3-d map from a pre-defined field. returns false if error.
bool	createCylinderMap (G4double Z0, G4double dR, G4double dZ, int nR, int nZ, class G4ElectroMagneticField *field)
	createCylinderMap() will create a 2-d map from a pre-defined cylindrically-symmetric field. NOTE: cylindrical symmetry is ASSUMED; the field in the Y=0,X>=0 half-plane is used (Bx->Br...). returns false if error.
bool	createTimeDependence (int n, G4double t[], G4double b[], G4double e[]=0, G4double period=-1.0)
	createTimeDependence() will apply the time dependence given. n is the # elements in the arrays; t[] is the time value for each point, b[] is the factor for B, and e[] is the factor for E. returns false if error.
bool	getTimeFactor (G4double t, G4double *b, G4double *e)
	getTimeFactor() returns the time factors for B and E at time t. returns false if error.
Private Attributes
G4int	maxline
G4double	current
G4double	gradient
G4double	normB
G4double	normE
class FieldMapImpl *	impl
class TimeImpl *	time
Friends
class	FieldMapPlacement

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Constructor & Destructor Documentation

BLFieldMap::BLFieldMap

(

)

default constructor.

References current, gradient, impl, maxline, normB, normE, and time.

{
        maxline = 1024;
        current = 1.0;
        gradient = 1.0;
        normB = 1.0;
        normE = 1.0;
        impl = 0;
        time = 0;
}

BLFieldMap::~BLFieldMap

(

)

[virtual]

destructor.

References impl, and time.

{
        if(impl) delete impl;
        impl = 0;
        if(time) delete time;
        time = 0;
}

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Member Function Documentation

bool BLFieldMap::readFile

(

G4String

filename

)

readFile() reads a file to initialize the map. Returns true if OK, false on error.

References argDouble(), argInt(), InputFile::close(), current, InputFile::filename(), InputFile::getline(), InputFile::good(), gradient, FieldMapImpl::handleCommand(), impl, InputFile::linenumber(), maxline, normB, normE, BLCommand::parseArgs(), BLCommand::printError(), TimeImpl::readTime(), InputFile::setMaxline(), and time.

Referenced by BLCMDrfdevice::command(), BLCMDpillbox::command(), and BLCMDfieldmap::command().

{
        InputFile in(filename,maxline);
        if(!in.good()) {
                BLCommand::printError("BLFieldMap Cannot open file '%s'",
                                in.filename());
                return false;
        }
        printf("BLFieldMap: reading file '%s'\n",in.filename());

        bool retval = true;

        char *line;
        while((line=in.getline()) != 0) {
                BLArgumentVector argv;
                BLArgumentMap namedArgs;
                if(BLCommand::parseArgs(line,argv,namedArgs) < 0)
                        goto invalid;
                if(argv[0] == "") continue;
                if(argv[0] == "param") {
                        argInt(maxline,"maxline",namedArgs);
                        argDouble(current,"current",namedArgs);
                        argDouble(gradient,"gradient",namedArgs);
                        argDouble(normB,"normB",namedArgs);
                        argDouble(normE,"normE",namedArgs);
                        in.setMaxline(maxline);
                } else if(argv[0] == "grid") {
                        if(impl) goto invalid;
                        impl = new GridImpl(argv,namedArgs);
                } else if(argv[0] == "cylinder") {
                        if(impl) goto invalid;
                        impl = new CylinderImpl(argv,namedArgs);
                } else if(argv[0] == "time") {
                        if(time) goto invalid;
                        time = TimeImpl::readTime(in,argv,namedArgs);
                        if(!time) goto invalid;
                } else if(impl) {
                        if(!impl->handleCommand(in,argv,namedArgs))
                                goto invalid;
                } else {
invalid:                BLCommand::printError("BLFieldMap file '%s' line %d invalid command '%s'\n",
                                        in.filename(),in.linenumber(),
                                        argv[0].c_str());
                        retval = false;
                        break;
                }
        }
        in.close();

        return retval;
}

bool BLFieldMap::writeFile	(	G4String	filename,
		G4String	comment = ""
	)

writeFile() writes the map to a file. Returns true if OK, false on error.

References current, gradient, impl, maxline, normB, normE, and FieldMapImpl::writeFile().

Referenced by BLCMDprintfield::do_cylinder(), and BLCMDprintfield::do_grid().

{
        if(!impl) return false;

        FILE *f = fopen(filename.c_str(),"r");
        if(f) {
                fclose(f);
                G4Exception("BLFieldMap","Output File Exists",FatalException,
                                                        filename.c_str());
        }

        f = fopen(filename,"w");
        if(!f) {
                fprintf(stderr,"BLFieldMap::writeFile CANNOT WRITE file '%s'\n",
                                filename.c_str());
                return false;
        }

        fprintf(f,"# %s\n",comment.c_str());
        fprintf(f,"param maxline=%d current=%g gradient=%g normB=%g normE=%g\n",
                maxline,current,gradient,normB,normE);

        bool retval = impl->writeFile(f);

        fclose(f);
        return retval;
}

void BLFieldMap::getFieldValue	(	const G4double	local[4],
		G4double	field[6],
		G4double	current = 1.0,
		G4double	gradient = 1.0
	)

getFieldValue() gets the map's field to the field[] array. local[] must be LOCAL coordinates; local[3] (time) is ignored unless there is a time dependence specified. (elements using BLFieldMap perform the global->local conversion)

References current, TimeImpl::factorB(), TimeImpl::factorE(), FieldMapImpl::getFieldValue(), gradient, impl, normB, normE, and time.

Referenced by PillboxField::addFieldValue(), FieldMapPlacement::addFieldValue(), FieldExprPlacement::addFieldValue(), BLCMDfieldexpr::maxError(), and RFdeviceField::UserSteppingAction().

{
        if(!impl)
                throw "BLFieldMap::getFieldValue called, no implementation";

        G4double thisField[6];
        impl->getFieldValue(local,thisField);
        G4double timeB=1.0, timeE=1.0;
        if(time) {
                timeB = time->factorB(local[3]);
                timeE = time->factorE(local[3]);
        }
        field[0] = thisField[0] * normB * timeB * _current/current;
        field[1] = thisField[1] * normB * timeB * _current/current;
        field[2] = thisField[2] * normB * timeB * _current/current;
        field[3] = thisField[3] * normE * timeE * _gradient/gradient;
        field[4] = thisField[4] * normE * timeE * _gradient/gradient;
        field[5] = thisField[5] * normE * timeE * _gradient/gradient;
}

void BLFieldMap::getFieldValueNoTimeNoScale	(	const G4double	local[4],
		G4double	field[6]
	)

getFieldValueNoTimeNoScale() as above, except no time dependence is applies, and no scaling is performed.

References FieldMapImpl::getFieldValue(), and impl.

Referenced by RFdeviceField::addFieldValue().

{
        if(!impl)
                throw "BLFieldMap::getFieldValueNoTimeNoScale called, no implementation";

        impl->getFieldValue(local,field);
}

void BLFieldMap::getBoundingPoint	(	int	i,
		G4double	point[4]
	)

getBoundingPoint() returns the i-th bounding point of the map.

References FieldMapImpl::getBoundingPoint(), and impl.

Referenced by FieldExprPlacement::FieldExprPlacement(), and FieldMapPlacement::FieldMapPlacement().

{
        impl->getBoundingPoint(i,point);
}

bool BLFieldMap::hasB

(

)

hasB() returns true if this map has a nonzero B field.

References FieldMapImpl::hasB(), and impl.

Referenced by FieldMapPlacement::addFieldValue(), and FieldExprPlacement::addFieldValue().

{
        return impl->hasB();
}

bool BLFieldMap::hasE

(

)

hasE() returns true if this map has a nonzero E field.

References FieldMapImpl::hasE(), and impl.

Referenced by FieldMapPlacement::addFieldValue(), and FieldExprPlacement::addFieldValue().

{
        return impl->hasE();
}

bool BLFieldMap::createGridMap	(	G4double	X0,
		G4double	Y0,
		G4double	Z0,
		G4double	dX,
		G4double	dY,
		G4double	dZ,
		int	nX,
		int	nY,
		int	nZ,
		class G4ElectroMagneticField *	field
	)

createGridMap() will create a 3-d map from a pre-defined field. returns false if error.

References current, d2string(), gradient, i2string(), impl, maxline, normB, normE, and GridImpl::setField().

Referenced by BLCMDfieldexpr::command(), and BLCMDprintfield::do_grid().

{
        if(impl) {
                delete impl;
                impl = 0;
        }
        maxline = 128;
        current = 1.0;
        gradient = 1.0;
        normB = 1.0;
        normE = 1.0;

        BLArgumentVector argv;
        BLArgumentMap args;
        args["X0"] = d2string(X0);
        args["Y0"] = d2string(Y0);
        args["Z0"] = d2string(Z0);
        args["dX"] = d2string(dX);
        args["dY"] = d2string(dY);
        args["dZ"] = d2string(dZ);
        args["nX"] = i2string(nX);
        args["nY"] = i2string(nY);
        args["nZ"] = i2string(nZ);

        GridImpl *grid = new GridImpl(argv,args);
        impl = grid;

        bool retval = true;
        G4double pos[4], field[6];
        pos[3] = 0.0;
        for(int i=0; i<nX; ++i) {
                pos[0] = X0 + i*dX;
                for(int j=0; j<nY; ++j) {
                        pos[1] = Y0 + j*dY;
                        for(int k=0; k<nZ; ++k) {
                                pos[2] = Z0 + k*dZ;
                                emField->GetFieldValue(pos,field);
                                if(!grid->setField(pos[0],pos[1],pos[2],
                                            field[0],field[1],field[2],
                                            field[3],field[4],field[5],0))
                                        retval = false;
                        }
                }
        }

        return retval;
}

bool BLFieldMap::createCylinderMap	(	G4double	Z0,
		G4double	dR,
		G4double	dZ,
		int	nR,
		int	nZ,
		class G4ElectroMagneticField *	field
	)

createCylinderMap() will create a 2-d map from a pre-defined cylindrically-symmetric field. NOTE: cylindrical symmetry is ASSUMED; the field in the Y=0,X>=0 half-plane is used (Bx->Br...). returns false if error.

References current, d2string(), gradient, i2string(), impl, maxline, normB, normE, and CylinderImpl::setField().

Referenced by BLCMDfieldexpr::command(), and BLCMDprintfield::do_cylinder().

{
        if(impl) {
                delete impl;
                impl = 0;
        }
        maxline = 128;
        current = 1.0;
        gradient = 1.0;
        normB = 1.0;
        normE = 1.0;

        BLArgumentVector argv;
        BLArgumentMap args;
        args["Z0"] = d2string(Z0);
        args["dR"] = d2string(dR);
        args["dZ"] = d2string(dZ);
        args["nR"] = i2string(nR);
        args["nZ"] = i2string(nZ);

        CylinderImpl *cyl = new CylinderImpl(argv,args);
        impl = cyl;

        // use the Y=0 plane for the R,Z plane
        bool retval = true;
        G4double pos[4], field[6];
        pos[3] = 0.0;
        for(int i=0; i<nR; ++i) {
                pos[0] = 0.0 + i*dR;
                pos[1] = 0.0;
                for(int k=0; k<nZ; ++k) {
                        pos[2] = Z0 + k*dZ;
                        emField->GetFieldValue(pos,field);
                        if(!cyl->setField(pos[0],pos[2],field[0],field[2],
                                            field[3],field[5],0))
                                retval = false;
                }
        }

        return false;
}

bool BLFieldMap::createTimeDependence	(	int	n,
		G4double	t[],
		G4double	b[],
		G4double	e[] = 0,
		G4double	period = -1.0
	)

createTimeDependence() will apply the time dependence given. n is the # elements in the arrays; t[] is the time value for each point, b[] is the factor for B, and e[] is the factor for E. returns false if error.

References TimeImpl::setPeriod(), and time.

Referenced by BLCMDfieldexpr::handleTimeDependence().

{
        if(time) return false;
        time = new TimeImpl(n,t,b,e);
        if(period > 0.0)
                time->setPeriod(period);
        return true;
}

bool BLFieldMap::getTimeFactor	(	G4double	t,
		G4double *	b,
		G4double *	e
	)

getTimeFactor() returns the time factors for B and E at time t. returns false if error.

References TimeImpl::factorB(), TimeImpl::factorE(), and time.

{
        if(b) *b = (time ? time->factorB(t) : 1.0);
        if(e) *e = (time ? time->factorE(t) : 1.0);
        return true;
}

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Friends And Related Function Documentation

friend class FieldMapPlacement [friend]

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Member Data Documentation

G4int BLFieldMap::maxline [private]

Referenced by BLFieldMap(), createCylinderMap(), createGridMap(), readFile(), and writeFile().

G4double BLFieldMap::current [private]

Referenced by BLFieldMap(), createCylinderMap(), createGridMap(), getFieldValue(), readFile(), and writeFile().

G4double BLFieldMap::gradient [private]

Referenced by BLFieldMap(), createCylinderMap(), createGridMap(), getFieldValue(), readFile(), and writeFile().

G4double BLFieldMap::normB [private]

Referenced by BLFieldMap(), createCylinderMap(), createGridMap(), getFieldValue(), readFile(), and writeFile().

G4double BLFieldMap::normE [private]

Referenced by BLFieldMap(), createCylinderMap(), createGridMap(), getFieldValue(), readFile(), and writeFile().

class FieldMapImpl* BLFieldMap::impl [private]

Referenced by BLFieldMap(), createCylinderMap(), createGridMap(), getBoundingPoint(), getFieldValue(), getFieldValueNoTimeNoScale(), hasB(), hasE(), readFile(), writeFile(), and ~BLFieldMap().

class TimeImpl* BLFieldMap::time [private]

Referenced by BLFieldMap(), createTimeDependence(), getFieldValue(), getTimeFactor(), readFile(), and ~BLFieldMap().

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The documentation for this class was generated from the following files:

• BLFieldMap.hh
• BLFieldMap.cc