OpalScalingFFAMagnet.cpp

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/* 
 *  Copyright (c) 2017, Chris Rogers
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#include "Attributes/Attributes.h"  // used?
#include "Utilities/OpalException.h"  // used?
 
#include "AbsBeamline/EndFieldModel/Tanh.h" // classic
#include "AbsBeamline/ScalingFFAMagnet.h" // classic
#include "Elements/OpalScalingFFAMagnet.h"
 
extern Inform *gmsg;
 
OpalScalingFFAMagnet::OpalScalingFFAMagnet() :
    OpalElement(SIZE, "SCALINGFFAMAGNET",
             "The \"ScalingFFAMagnet\" element defines a FFA scaling magnet with zero or non-zero spiral angle.") {
    itsAttr[B0] = Attributes::makeReal
                              ("B0", "The nominal dipole field of the magnet [T].");
    itsAttr[R0] = Attributes::makeReal("R0", "Radial scale [m].");
    itsAttr[FIELD_INDEX] = Attributes::makeReal("FIELD_INDEX",
      "The scaling magnet field index.");
    itsAttr[TAN_DELTA] = Attributes::makeReal("TAN_DELTA",
      "Tangent of the spiral angle; set to 0 to make a radial sector magnet.");
    itsAttr[MAX_Y_POWER] = Attributes::makeReal("MAX_Y_POWER",
      "The maximum power in y that will be considered in the field expansion.");
    itsAttr[END_LENGTH] = Attributes::makeReal("END_LENGTH",
                                          "The end length of the spiral FFA [m].");
    itsAttr[HEIGHT] = Attributes::makeReal("HEIGHT",
                                       "Full height of the magnet. Particles moving more than height/2. off the midplane (either above or below) are out of the aperture [m].");
    itsAttr[CENTRE_LENGTH] = Attributes::makeReal("CENTRE_LENGTH",
                                       "The centre length of the spiral FFA [m].");
    itsAttr[RADIAL_NEG_EXTENT] = Attributes::makeReal("RADIAL_NEG_EXTENT",
                                       "Particles are considered outside the tracking region if radius is greater than R0-RADIAL_NEG_EXTENT [m].");
    itsAttr[RADIAL_POS_EXTENT] = Attributes::makeReal("RADIAL_POS_EXTENT",
                                       "Particles are considered outside the tracking region if radius is greater than R0+RADIAL_POS_EXTENT [m].");
    itsAttr[MAGNET_START] = Attributes::makeReal("MAGNET_START",
                                          "Determines the position of the central portion of the magnet field relative to the element start (default is 2*end_length). [m]");
    itsAttr[MAGNET_END] = Attributes::makeReal("MAGNET_END",
                                       "Offset to the end of the magnet, i.e. placement of the next element. Default is centre_length + 4*end_length.");
    itsAttr[AZIMUTHAL_EXTENT] = Attributes::makeReal("AZIMUTHAL_EXTENT",
                                       "The field will be assumed zero if particles are more than AZIMUTHAL_EXTENT from the magnet centre (psi=0). Default is CENTRE_LENGTH/2.+5.*END_LENGTH [m].");
    registerOwnership();
 
    ScalingFFAMagnet* magnet = new ScalingFFAMagnet("ScalingFFAMagnet");
    magnet->setEndField(new endfieldmodel::Tanh(1., 1., 1));
    setElement(magnet);
}
 
 
OpalScalingFFAMagnet::OpalScalingFFAMagnet(const std::string &name,
                                             OpalScalingFFAMagnet *parent) :
    OpalElement(name, parent) {
    ScalingFFAMagnet* magnet = new ScalingFFAMagnet(name);
    magnet->setEndField(new endfieldmodel::Tanh(1., 1., 1));
    setElement(magnet);
}
 
 
OpalScalingFFAMagnet::~OpalScalingFFAMagnet() {
}
 
 
OpalScalingFFAMagnet *OpalScalingFFAMagnet::clone(const std::string &name) {
    return new OpalScalingFFAMagnet(name, this);
}
 
 
void OpalScalingFFAMagnet::update() {
    ScalingFFAMagnet *magnet = dynamic_cast<ScalingFFAMagnet*>(getElement());
 
    // use L = r0*theta; we define the magnet ito length for UI but ito angles
    // internally; and use m as external default unit and mm internally
    double metres = 1e3;
    // get r0 in m
    double r0 = Attributes::getReal(itsAttr[R0]);
    magnet->setR0(r0*metres);
    // get B0 in T
    magnet->setDipoleConstant(Attributes::getReal(itsAttr[B0]));
 
    // dimensionless quantities
    magnet->setFieldIndex(Attributes::getReal(itsAttr[FIELD_INDEX]));
    magnet->setTanDelta(Attributes::getReal(itsAttr[TAN_DELTA]));
    int maxOrder = floor(Attributes::getReal(itsAttr[MAX_Y_POWER]));
    magnet->setMaxOrder(maxOrder);
 
    // get centre length and end length in radians
    endfieldmodel::Tanh* endField = dynamic_cast<endfieldmodel::Tanh*>(magnet->getEndField());
    double end_length = Attributes::getReal(itsAttr[END_LENGTH])/r0;
    double centre_length = Attributes::getReal(itsAttr[CENTRE_LENGTH])/2./r0;
    endField->setLambda(end_length);
    // x0 is the distance between B=0.5*B0 and B=B0 i.e. half the centre length
    endField->setX0(centre_length);
    endField->setTanhDiffIndices(maxOrder+2);
 
    // get rmin and rmax bounding box edge in mm
    double rmin = r0-Attributes::getReal(itsAttr[RADIAL_NEG_EXTENT]);
    double rmax = r0+Attributes::getReal(itsAttr[RADIAL_POS_EXTENT]);
    magnet->setRMin(rmin*metres);
    magnet->setRMax(rmax*metres);
    Vector_t centre(-r0*metres, 0, 0);
    magnet->setCentre(centre);
 
    // we store maximum vertical displacement (which is half the height)
    double height = Attributes::getReal(itsAttr[HEIGHT])*metres;
    magnet->setVerticalExtent(height/2.);
 
    // get default length of the magnet element in radians
    // total length is two end field lengths (e-folds) at each end plus a
    // centre length
    double defaultLength = (endField->getLambda()*4.+2.*endField->getX0());
 
    // get end of the magnet element in radians
    if (itsAttr[MAGNET_END]) {
        double phi_end = Attributes::getReal(itsAttr[MAGNET_END])/r0;
        magnet->setPhiEnd(phi_end);
    } else {
        magnet->setPhiEnd(defaultLength);
    }
 
    // get start of the magnet element in radians
    // setPhiStart sets the position of the magnet centre relative to start (!)
    if (itsAttr[MAGNET_START]) {
        double phi_start = Attributes::getReal(itsAttr[MAGNET_START])/r0;
        magnet->setPhiStart(phi_start+centre_length);
    } else {
        magnet->setPhiStart(defaultLength/2.);
    }
    // get azimuthal extent in radians; this is just the bounding box
    double defaultExtent = (endField->getLambda()*5.+endField->getX0());
    if (itsAttr[AZIMUTHAL_EXTENT]) {
        magnet->setAzimuthalExtent(Attributes::getReal(itsAttr[AZIMUTHAL_EXTENT])/r0);
    } else {
        magnet->setAzimuthalExtent(defaultExtent);
    }
    magnet->initialise();
    setElement(magnet);
 
}