BDSCollimatorRectangular.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 "BDSCollimatorRectangular.hh"
 
#include "globals.hh"
#include "G4Box.hh"
#include "G4Trd.hh"
 
BDSCollimatorRectangular::BDSCollimatorRectangular(const G4String& nameIn,
                                                   G4double    lengthIn,
                                                   G4double    horizontalWidthIn,
                                                   G4Material* collimatorMaterialIn,
                                                   G4Material* vacuumMaterialIn,
                                                   G4double    xApertureIn,
                                                   G4double    yApertureIn,
                                                   G4double    xApertureOutIn,
                                                   G4double    yApertureOutIn,
                                                   G4Colour*   colourIn,
                                                   G4bool      circularOuterIn):
  BDSCollimator(nameIn, lengthIn, horizontalWidthIn, "rcol",
                collimatorMaterialIn, vacuumMaterialIn, xApertureIn,
                yApertureIn, xApertureOutIn, yApertureOutIn, colourIn, circularOuterIn)
{;}
 
void BDSCollimatorRectangular::BuildInnerCollimator()
{
  if (tapered)
    {
      // Make subtracted volume longer than the solid volume by extrapolating
      // linear gradient along 1% of the length of the element. May break down
      // in the case of extreme gradients for really short collimators.
      G4double xGradient = (xApertureOut - xAperture) / chordLength;
      G4double yGradient = (yApertureOut - yAperture) / chordLength;
      
      G4double deltam = 0.01 * chordLength; // +ve z here
      G4double deltax = xGradient * deltam;
      G4double deltay = yGradient * deltam;
 
      // sign in front of deltax -> +ve for +ve z from centre, -ve for -ve x from centre
      innerSolid  = new G4Trd(name + "_inner_solid",             // name
                              xAperture - deltax,                // X entrance half length
                              xApertureOut + deltax,             // X exit half length
                              yAperture - deltay,                // Y entrance half length
                              yApertureOut + deltay,             // Y exit half length
                              (chordLength + 2*deltam) * 0.5);   // Z half length
    
      vacuumSolid = new G4Trd(name + "_vacuum_solid",               // name
                              xAperture - lengthSafetyLarge,        // X entrance half length
                              xApertureOut - lengthSafetyLarge,     // X exit half length
                              yAperture - lengthSafetyLarge,        // Y entrance half length
                              yApertureOut - lengthSafetyLarge,     // Y exit half length
                              chordLength*0.5 - lengthSafetyLarge); // Z half length
    }
  else
    {
      innerSolid  = new G4Box(name + "_inner_solid",    // name
                              xAperture,                // x half width
                              yAperture,                // y half width
                              chordLength);             // z half length
      // z half length long for unambiguous subtraction
 
      vacuumSolid = new G4Box(name + "_vacuum_solid",   // name
                              xAperture - lengthSafety, // x half width
                              yAperture - lengthSafety, // y half width
                              chordLength*0.5);         // z half length
    }
    
  RegisterSolid(innerSolid);
  RegisterSolid(vacuumSolid);
}