MultipoleTStraight.cpp

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/*
 *  Copyright (c) 2017, Titus Dascalu
 *  Copyright (c) 2018, Martin Duy Tat
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#include "gsl/gsl_sf_gamma.h"
#include "gsl/gsl_sf_pow_int.h"
#include "MultipoleTStraight.h"

using namespace endfieldmodel;

MultipoleTStraight::MultipoleTStraight(const std::string &name):
    MultipoleTBase(name),
    straightGeometry_m(getLength()) {
}

MultipoleTStraight::MultipoleTStraight(const MultipoleTStraight &right):
    MultipoleTBase(right),
    straightGeometry_m(right.straightGeometry_m) {
    RefPartBunch_m = right.RefPartBunch_m;
}


MultipoleTStraight::~MultipoleTStraight() {
}

ElementBase* MultipoleTStraight::clone() const {
    return new MultipoleTStraight(*this);
}

void MultipoleTStraight::transformCoords(Vector_t &R) {
    //R[2] += getBoundingBoxLength();
}

void MultipoleTStraight::setMaxOrder(const std::size_t &maxOrder) {
    MultipoleTBase::setMaxOrder(maxOrder);
}

double MultipoleTStraight::getBx(const Vector_t &R) {
    double Bx = 0.0;
    for(std::size_t n = 0; n <= getMaxOrder(); n++) {
        double f_n = 0.0;
        for(std::size_t i = 0; i <= n; i++) {
            f_n += gsl_sf_choose(n, i) * getTransDeriv(2 * i + 1, R[0]) *
                   getFringeDeriv(2 * n - 2 * i, R[2]);
        }
        f_n *= gsl_sf_pow_int(-1.0, n);
        Bx += f_n * gsl_sf_pow_int(R[1], 2 * 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 <= getMaxOrder(); n++) {
        double f_n = 0.0;
        for(std::size_t i = 0; i <= n; i++) {
            f_n += gsl_sf_choose(n, i) * getTransDeriv(2 * i, R[0]) *
                   getFringeDeriv(2 * n - 2 * i + 1, R[2]);
        }
        f_n *= gsl_sf_pow_int(-1.0, n);
        Bs += f_n * gsl_sf_pow_int(R[1], 2 * n + 1) / gsl_sf_fact(2 * n + 1);
    }
    return Bs;
}

double MultipoleTStraight::getFn(const std::size_t &n,
                                 const double &x, 
                                 const double &s) {
    if (n == 0) {
        return getTransDeriv(0, x) * getFringeDeriv(0, s);
    }
    double f_n = 0.0;
    for (std::size_t i = 0; i <= n; i++) {
        f_n += gsl_sf_choose(n, i) * getTransDeriv(2 * i, x) *
               getFringeDeriv(2 * n - 2 * i, s);
    }
    f_n *= gsl_sf_pow_int(-1.0, n);
    return f_n;
}