BDSCavityFactoryElliptical.cc

/* 
Beam Delivery Simulation (BDSIM) Copyright (C) Royal Holloway, 
University of London 2001 - 2023.
 
This file is part of BDSIM.
 
BDSIM is free software: you can redistribute it and/or modify 
it under the terms of the GNU General Public License as published 
by the Free Software Foundation version 3 of the License.
 
BDSIM is distributed in the hope that it will be useful, but 
WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
GNU General Public License for more details.
 
You should have received a copy of the GNU General Public License
along with BDSIM.  If not, see <http://www.gnu.org/licenses/>.
*/
#include "BDSCavity.hh"
#include "BDSCavityFactoryElliptical.hh"
#include "BDSCavityInfo.hh"
 
#include "globals.hh"
#include "G4LogicalVolume.hh"
#include "G4Polycone.hh"
#include "G4SubtractionSolid.hh"
#include "G4Tubs.hh"
#include "G4VisAttributes.hh"
#include "G4VSolid.hh"
 
#include "CLHEP/Units/SystemOfUnits.h"
 
#include <cmath>
#include <vector>
 
BDSCavityFactoryElliptical::BDSCavityFactoryElliptical()
{;}
 
BDSCavityFactoryElliptical::~BDSCavityFactoryElliptical()
{;}
 
G4double BDSCavityFactoryElliptical::CreateSolids(G4String             name,
                                                  G4double             totalChordLength,
                                                  const BDSCavityInfo* info)
{
  G4double chordLength = totalChordLength;
  // Elliptical Cavity Parameters
  // irisRSemiAxis    --> Semi-axis of the iris ellipse perpendicular to the length of the cavity.
  // irisZSemiAxis    --> Semi-axis of the iris ellipse along the length of the cavity.
  // equatorRSemiAxis --> Semi-axis of the equator ellipse perpendicular to the length of the cavity.
  // equatorZSemiAxis --> Semi-axis of the equator ellipse along the length of the cavity.
  // tangentAngle     --> Angle between the line vertical to the z-axis and the line tangent to both ellipses.
  // irisRadius       --> Radius of the iris.
  // noPoints         --> Number of points used to define the shape.  This is divided up between
  //                     the 3 constituent shapes, 1/4 in each iris ellipse and 1/2 in central dome.
  // length           --> Length of the cell.
  // equatorRadius    --> Radius at the equator.
  G4double equatorRadius    = info->equatorRadius;
  G4double irisRSemiAxis    = info->irisVerticalAxis;
  G4double irisZSemiAxis    = info->irisHorizontalAxis;     //iris ellipse horizontal semiaxis
  G4double equatorRSemiAxis = info->equatorVerticalAxis ;   //equator ellipse vertical semiaxis
  G4double equatorZSemiAxis = info->equatorHorizontalAxis;  //equator ellipse horizontal semiaxis
  G4double tangentAngle     = info->tangentLineAngle;
  G4double irisRadius       = info->irisRadius;
  G4double thickness        = info->thickness;
  unsigned int noPoints     = info->numberOfPoints;
 
  // calculate cartesian coordinates (z, r) from parameters.
  // 2D cylindrical coordinates, z along the beamline:
  G4double zi = chordLength * 0.5;                // z coord of iris ellipse centre
  G4double ri = irisRadius + irisRSemiAxis;       // r coord of iris ellipse centre
  G4double ze = 0.0;                              // z coord of equator ellipse centre
  G4double re = equatorRadius - equatorRSemiAxis; // r coord of equator ellipse centre.
  // gradient of line connecting the ellipses.
  // Add a pi/2 because angle is defined from the vertical, clockwise.
  G4double m = std::tan(tangentAngle + CLHEP::halfpi); 
   
  // Gradient from tangentAngle. Find the derivative of ellipses. Equate
  // and solve for the parameter.
  // atan finds solution in the first quadrant.
  G4double equatorParameterTangentPoint = std::atan(-equatorRSemiAxis/(m*equatorZSemiAxis));
  // Add pi to get desired solution (third quadrant)
  G4double irisParameterTangentPoint = std::atan(-irisRSemiAxis/(m*irisZSemiAxis)) + CLHEP::pi; 
 
  // Rounding down to a multiple of 4. This is so that number of points are
  // share equally and consistently between the constituent ellipses.
  noPoints = noPoints - (noPoints % 4);  
 
  // Vector Definitions:
  // Parametric equation parameters:
  // equatorParameter --> the values of a parameter  for generating the central ellipses
  // irisParameter    --> the values of a parameter  for generating the iris ellipse
  
  //The Cartesian coordinates to be calculated from above parameters:
  //rInnerCoord      --> the values of radius for the inner geometry
  //rOuterCoord      --> the values of radius for the outer geometry
  //zInnerCoord      --> the values of z for the inner geometry
  //zOuterCoord      --> the values of z for the outer goemetry
  
  //Vector declaration:
  std::vector<G4double> equatorParameter;
  std::vector<G4double> irisParameter;
  std::vector<G4double> rInnerCoord;
  std::vector<G4double> rOuterCoord;
  std::vector<G4double> zInnerCoord;
  std::vector<G4double> zOuterCoord; 
    
  // Generate values for the parameters used to define the ellipse shapes
    
  // Vector of parameter values for generating the iris ellipse.  This can then be
  // reflected to find the iris ellipse on the other side.
  for (unsigned int i = 0; i < noPoints/4; i++) //iris allocated one quarter of points.
    {irisParameter.push_back(1.5*CLHEP::pi + (1.5*CLHEP::pi - irisParameterTangentPoint )*i/((noPoints/4)-1));}
 
  //Vector of parameter values for generating the equator ellipse
  for (unsigned int i = 0; i < noPoints/2; i++) //equator ellipse allocated half of the points
    {
      G4double term1 = CLHEP::pi - equatorParameterTangentPoint;
      G4double term2 = CLHEP::pi - 2*equatorParameterTangentPoint;
      G4double term3 = (noPoints*0.5) - 1;
      G4double value = term1 - term2 * i  / term3;
      equatorParameter.push_back(value);
    }
  
  // Calculate the coordinates of the inner cavity shape, starting from -z through
  // to +z, in 3 sections: -z iris ellipse -> equator ellipse -> +z iris ellipse.
  // Geant requires the coordinates to be done in this (negative to positive)
  
  // -z iris ellipse:
  // noPoints/4 because of the total noPoints, the iris ellipse in -z is allocated a quarter of points.
  for (unsigned int i = 0; i < noPoints/4; i++) 
    {
      // An extra point at the very start for unambigious boolean subtraction later on.
      // Will not actually be part of the final geometry.
      if (i == 0) 
        {
          //-10mm so boundaries don't lay upon each other when using boolean operation
          zInnerCoord.push_back(- zi + irisZSemiAxis * std::cos(irisParameter[i]) - 10*CLHEP::mm); 
          rInnerCoord.push_back(ri + irisRSemiAxis * std::sin(irisParameter[i]));
        }
      zInnerCoord.push_back(- zi + irisZSemiAxis * std::cos(irisParameter[i]));
      rInnerCoord.push_back(ri + irisRSemiAxis * std::sin(irisParameter[i]));
    }
  
  //equator ellipse (middle):
  for (unsigned int i = 0; i < noPoints/2; i++)  //central ellipse is allocated half the total points.  
    {
      zInnerCoord.push_back(ze + equatorZSemiAxis * std::cos(equatorParameter[i]));
      rInnerCoord.push_back(re + equatorRSemiAxis * std::sin(equatorParameter[i]));
    };
  
  //+z iris ellipse:
  for (unsigned int i = 0; i < noPoints/4; i++)  //the +z iris ellipse is allocated noPoints/4.
    {
      zInnerCoord.push_back(zi + irisZSemiAxis * std::cos(CLHEP::pi - irisParameter[noPoints/4 - 1 - i]));
      rInnerCoord.push_back(ri + irisRSemiAxis * std::sin(CLHEP::pi - irisParameter[noPoints/4 - 1 - i]));       
      //If last point, add an extra point purely for unambigious boolean subtraction later.
      if (i == (noPoints/4 - 1))
        {
          //+10mm so boundaries don't lay upon each other
          zInnerCoord.push_back(zi + irisZSemiAxis * std::cos(CLHEP::pi - irisParameter[noPoints/4 - 1 - i]) + 10*CLHEP::mm); 
          rInnerCoord.push_back(ri + irisRSemiAxis * std::sin(CLHEP::pi - irisParameter[noPoints/4 - 1 - i]));
        }
    }  
  
  // Generating points for the entire outer cavity shape by using the inner cavity
  // vector of coordinates--- This works by calculating the gradient at each point on the curve.
  // It then finds a unit vector pointing perpendicularly outwards from this point and multiplies
  // by the thickness.  This creates a second vector of points for the outer geometry.
  //starting from 1 and ending at n-1 so that the coordinates used for the boolean subtraction are excluded.
  for (unsigned int i = 1; i < zInnerCoord.size() - 1; i++)
    {
      //calculate the gradient at point i
      G4double gradientAt_i = (rInnerCoord[i-1]-rInnerCoord[i+1])/(zInnerCoord[i-1]-zInnerCoord[i+1]);
 
      // Since the calculation relies on using the two points either side, and the
      // ends have only one coordinate either side, take the ends as having gradient = 0.
      // So that the vector points vertically upwards.  Otherwise just do the calculation described above.
      if (i == 1 || i == (zInnerCoord.size() - 2))
        {
          zOuterCoord.push_back(zInnerCoord[i]);
          rOuterCoord.push_back(rInnerCoord[i] + thickness);
        }
      else
        {
          zOuterCoord.push_back(- gradientAt_i*thickness * std::pow( (gradientAt_i * gradientAt_i + 1), -0.5) + zInnerCoord[i]);
          rOuterCoord.push_back(+ thickness * std::pow( (gradientAt_i*gradientAt_i + 1), -0.5) + rInnerCoord[i]);
        }
    }
 
#ifdef BDSDEBUG
  G4cout << "Now printing the values of (zInnerCoord,rInnerCoord):" << G4endl;
  G4cout << "Length of zInnerCoord = " << zInnerCoord.size() << G4endl;
  G4cout << "Length of rInnerCoord = " << rInnerCoord.size() << G4endl;
  for (G4int i = 0; i < (G4int)zInnerCoord.size(); i++)
    {G4cout << "(" << zInnerCoord[i] << "," << rInnerCoord[i] << ")" << G4endl;};
  
  G4cout << "Now printing the values of (zOuterCoord,rOuterCoord):" << G4endl;
  G4cout << "Length of zOuterCoord = " << zOuterCoord.size() << G4endl;
  G4cout << "Length of rOuterCoord = " << rOuterCoord.size() << G4endl;
  for (G4int i = 0; i < (G4int)zOuterCoord.size(); i++)
    {G4cout << "(" << zOuterCoord[i] << "," << rOuterCoord[i] << ")" << G4endl;};
#endif
 
  // Array of inner r coordinates.  zeroes ensures the polycone will be solid.
  std::vector<G4double> solidArrayOuter(noPoints, 0.0); 
  // Array of inner r coordinates.  zeroes ensures the polycone will be solid. 1 extra
  // point either side for unambiguous  boolean subtraction.
  std::vector<G4double> solidArrayInner(noPoints+2, 0.0); 
 
  // Define the inner solid which is to be subtracted from the outer and also used to
  // define the vacuum.
  G4VSolid* innerSolid = new G4Polycone(name + "_inner_solid", //name
                                        0.0,                   //start angle
                                        CLHEP::twopi,          //sweep angle
                                        zInnerCoord.size(),
                                        zInnerCoord.data(),
                                        solidArrayInner.data(),
                                        rInnerCoord.data());   //r coordinates
 
  // Define the outer solid from which the inner is subtracted.
  G4VSolid* outerSolid = new G4Polycone(name + "_outer_solid", // name
                                        0.0,                   // start angle
                                        CLHEP::twopi,          // sweep angle
                                        zOuterCoord.size(),    // number of corners
                                        zOuterCoord.data(),    // zOuterCoord array of points
                                        solidArrayOuter.data(),// array of zeroes for solid shape
                                        rOuterCoord.data());   // rOuterCoord array of points.
  allSolids.insert(innerSolid);
  allSolids.insert(outerSolid);
  
  // Do the subtraction
  cavitySolid = new G4SubtractionSolid(name + "_cavity_solid",  // name
                                       outerSolid,              // solid1
                                       innerSolid);             // minus solid2
 
  // Delete first and last elements of the InnerCoord Vectors, as these entries.
  // The reason we need to do this is the same vector is also used for making the
  // vacuum filling the cavity, but without the extra points for subtraction.
  rInnerCoord.erase (rInnerCoord.begin());
  rInnerCoord.pop_back();
  zInnerCoord.erase (zInnerCoord.begin());
  zInnerCoord.pop_back();
  
  //Take lengthsafety from all r points and the end z points, to avoid overlap with the cavity.
  for (unsigned int i = 0; i < noPoints; i++)
    {rInnerCoord[i] = rInnerCoord[i] - lengthSafetyLarge;}
  
  zInnerCoord[0]                    = zInnerCoord[0] + 2*lengthSafety;
  G4int lastInd = (G4int)zInnerCoord.size() - 1;
  zInnerCoord[lastInd] = zInnerCoord[lastInd] - 2*lengthSafety; // last element
  
  vacuumSolid = new G4Polycone(name + "_inner_solid", //name
                               0.0,                   //start angle
                               CLHEP::twopi,          //sweep angle
                               zInnerCoord.size(),
                               zInnerCoord.data(),
                               solidArrayInner.data(),
                               rInnerCoord.data());   //r coordinates
  allSolids.insert(vacuumSolid);
 
  G4double containerRadius = equatorRadius + thickness + lengthSafetyLarge;
  containerSolid = new G4Tubs(name + "_container_solid",   // name
                              0.0,                         // innerRadius
                              containerRadius,             // outerRadius
                              chordLength*0.5,             // half length
                              0.0,                         // starting angle
                              CLHEP::twopi);               // sweep angle
  return containerRadius;
}
 
void BDSCavityFactoryElliptical::SetVisAttributes(G4String /*colourName*/)
{
  BDSCavityFactoryBase::SetVisAttributes("srfcavity");
}