MultipoleTStraight.cpp

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/*
 *  Copyright (c) 2017, Titus Dascalu
 *  Copyright (c) 2018, Martin Duy Tat
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 *     this list of conditions and the following disclaimer.
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 *     and/or other materials provided with the distribution.
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 *     endorse or promote products derived from this software without specific
 *     prior written permission.
 *
 *  THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
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#include "gsl/gsl_sf_gamma.h"
#include "gsl/gsl_sf_pow_int.h"
#include "MultipoleTStraight.h"
#include "MultipoleT.h"
 
MultipoleTStraight::MultipoleTStraight(MultipoleT* element) :
        MultipoleTBase(element){
}
 
void MultipoleTStraight::initialise() {
    straightGeometry_m.setElementLength(element_m->getLength());
}
 
double MultipoleTStraight::getBx(const Vector_t &R) {
    double Bx = 0.0;
    for(std::size_t n = 0; n <= element_m->getMaxFOrder(); n++) {
        double f_n = 0.0;
        for(std::size_t i = 0; i <= n; i++) {
            f_n += gsl_sf_choose(n, i) * element_m->getTransDeriv(2 * i + 1, R[0]) *
                   element_m->getFringeDeriv(2 * n - 2 * i, R[2]);
        }
        f_n *= gsl_sf_pow_int(-1.0, static_cast<int>(n));
        Bx += f_n * gsl_sf_pow_int(R[1], 2 * static_cast<int>(n) + 1) / gsl_sf_fact(2 * n + 1);
    }
    return Bx;
}
 
double MultipoleTStraight::getBs(const Vector_t &R) {
    double Bs = 0.0;
    for(std::size_t n = 0; n <= element_m->getMaxFOrder(); n++) {
        double f_n = 0.0;
        for(std::size_t i = 0; i <= n; i++) {
            f_n += gsl_sf_choose(n, i) * element_m->getTransDeriv(2 * i, R[0]) *
                   element_m->getFringeDeriv(2 * n - 2 * i + 1, R[2]);
        }
        f_n *= gsl_sf_pow_int(-1.0, static_cast<int>(n));
        Bs += f_n * gsl_sf_pow_int(R[1], 2 * static_cast<int>(n) + 1) / gsl_sf_fact(2 * n + 1);
    }
    return Bs;
}
 
double MultipoleTStraight::getFn(size_t n, double x, double s) {
    if (n == 0) {
        return element_m->getTransDeriv(0, x) * element_m->getFringeDeriv(0, s);
    }
    double f_n = 0.0;
    for (std::size_t i = 0; i <= n; i++) {
        f_n += gsl_sf_choose(n, i) * element_m->getTransDeriv(2 * i, x) *
               element_m->getFringeDeriv(2 * n - 2 * i, s);
    }
    f_n *= gsl_sf_pow_int(-1.0, static_cast<int>(n));
    return f_n;
}
 
Vector_t MultipoleTStraight::localCartesianToOpalCartesian(const Vector_t& r) {
    return {r[0], r[1], r[2] + element_m->getLength() / 2.0};
}
 
void MultipoleTStraight::transformCoords(Vector_t& R) {
    // Magnet origin at the center rather than entry
    R[2] += element_m->getLength() / 2.0;
}