ERich_geo.cpp

//----------------------------------
//  eRICH: Electron endcap RICH
//  Author: C. Dilks
//----------------------------------

#include "DD4hep/DetFactoryHelper.h"
#include "DD4hep/OpticalSurfaces.h"
#include "DD4hep/Printout.h"
#include "DDRec/DetectorData.h"
#include "DDRec/Surface.h"
#include "GeometryHelpers.h"
#include "Math/Point2D.h"
#include "TMath.h"
#include "TString.h"
#include <XML/Helper.h>

using namespace dd4hep;
using namespace dd4hep::rec;

// create the detector
static Ref_t createDetector(Detector& desc, xml::Handle_t handle, SensitiveDetector sens)
{
  xml::DetElement detElem = handle;
  std::string     detName = detElem.nameStr();
  int             detID   = detElem.id();

  DetElement            det(detName, detID);
  xml::Component        dims    = detElem.dimensions();
  OpticalSurfaceManager surfMgr = desc.surfaceManager();

  // attributes -----------------------------------------------------------
  // - vessel
  double vesselLength    = dims.attr<double>(_Unicode(length));
  double vesselZmin      = dims.attr<double>(_Unicode(zmin));
  double vesselZmax      = dims.attr<double>(_Unicode(zmax));
  double vesselRmin0     = dims.attr<double>(_Unicode(rmin0));
  double vesselRmin1     = dims.attr<double>(_Unicode(rmin1));
  double vesselRmax0     = dims.attr<double>(_Unicode(rmax0));
  double vesselRmax1     = dims.attr<double>(_Unicode(rmax1));
  double wallThickness   = dims.attr<double>(_Unicode(wall_thickness));
  double windowThickness = dims.attr<double>(_Unicode(window_thickness));
  auto   vesselMat       = desc.material(detElem.attr<std::string>(_Unicode(material)));
  auto   gasvolMat       = desc.material(detElem.attr<std::string>(_Unicode(gas)));
  auto   vesselVis       = desc.visAttributes(detElem.attr<std::string>(_Unicode(vis_vessel)));
  auto   gasvolVis       = desc.visAttributes(detElem.attr<std::string>(_Unicode(vis_gas)));
  // - radiator (applies to aerogel and filter)
  auto   radiatorElem       = detElem.child(_Unicode(radiator));
  double radiatorRmin       = radiatorElem.attr<double>(_Unicode(rmin));
  double radiatorRmax       = radiatorElem.attr<double>(_Unicode(rmax));
  double radiatorPhiw       = radiatorElem.attr<double>(_Unicode(phiw));
  double radiatorPitch      = radiatorElem.attr<double>(_Unicode(pitch));
  double radiatorFrontplane = radiatorElem.attr<double>(_Unicode(frontplane));
  // - aerogel
  auto   aerogelElem      = radiatorElem.child(_Unicode(aerogel));
  auto   aerogelMat       = desc.material(aerogelElem.attr<std::string>(_Unicode(material)));
  auto   aerogelVis       = desc.visAttributes(aerogelElem.attr<std::string>(_Unicode(vis)));
  double aerogelThickness = aerogelElem.attr<double>(_Unicode(thickness));
  // - filter
  auto   filterElem      = radiatorElem.child(_Unicode(filter));
  auto   filterMat       = desc.material(filterElem.attr<std::string>(_Unicode(material)));
  auto   filterVis       = desc.visAttributes(filterElem.attr<std::string>(_Unicode(vis)));
  double filterThickness = filterElem.attr<double>(_Unicode(thickness));
  // - sensor module
  auto   sensorElem      = detElem.child(_Unicode(sensors)).child(_Unicode(module));
  auto   sensorMat       = desc.material(sensorElem.attr<std::string>(_Unicode(material)));
  auto   sensorVis       = desc.visAttributes(sensorElem.attr<std::string>(_Unicode(vis)));
  auto   sensorSurf      = surfMgr.opticalSurface(sensorElem.attr<std::string>(_Unicode(surface)));
  double sensorSide      = sensorElem.attr<double>(_Unicode(side));
  double sensorGap       = sensorElem.attr<double>(_Unicode(gap));
  double sensorThickness = sensorElem.attr<double>(_Unicode(thickness));
  // - sensor plane
  auto   sensorPlaneElem = detElem.child(_Unicode(sensors)).child(_Unicode(plane));
  double sensorPlaneDist = sensorPlaneElem.attr<double>(_Unicode(sensordist));
  double sensorPlaneRmin = sensorPlaneElem.attr<double>(_Unicode(rmin));
  double sensorPlaneRmax = sensorPlaneElem.attr<double>(_Unicode(rmax));
  // - debugging switches
  int debug_optics_mode = detElem.attr<int>(_Unicode(debug_optics));

  // if debugging optics, override some settings
  bool debug_optics = debug_optics_mode > 0;
  if (debug_optics) {
    printout(WARNING, "ERich_geo", "DEBUGGING ERICH OPTICS");
    switch (debug_optics_mode) {
    case 1:
      vesselMat = aerogelMat = filterMat = sensorMat = gasvolMat = desc.material("VacuumOptical");
      break;
    case 2:
      vesselMat = aerogelMat = filterMat = sensorMat = desc.material("VacuumOptical");
      break;
    default:
      printout(FATAL, "ERich_geo", "UNKNOWN debug_optics_mode");
      return det;
    };
    aerogelVis = sensorVis;
    gasvolVis = vesselVis = desc.invisible();
  };

  // BUILD VESSEL //////////////////////////////////////
  /* - `vessel`: aluminum enclosure, the mother volume of the eRICh
   * - `gasvol`: gas volume, which fills `vessel`; all other volumes defined below
   *   are children of `gasvol`
   */

  // tank solids
  double boreDelta = vesselRmin1 - vesselRmin0;
  Cone vesselTank(vesselLength / 2.0, vesselRmin1, vesselRmax1, vesselRmin0, vesselRmax0);
  Cone gasvolTank(vesselLength / 2.0 - windowThickness, vesselRmin1 + wallThickness, vesselRmax1 - wallThickness,
                  vesselRmin0 + wallThickness, vesselRmax0 - wallThickness);

  //  extra solids for `debug_optics` only
  Box vesselBox(1001, 1001, 1001);
  Box gasvolBox(1000, 1000, 1000);

  // choose vessel and gasvol solids (depending on `debug_optics_mode` (0=disabled))
  Solid vesselSolid, gasvolSolid;
  switch (debug_optics_mode) {
  case 0:
    vesselSolid = vesselTank;
    gasvolSolid = gasvolTank;
    break; // `!debug_optics`
  case 1:
    vesselSolid = vesselBox;
    gasvolSolid = gasvolBox;
    break;
  case 2:
    vesselSolid = vesselBox;
    gasvolSolid = gasvolTank;
    break;
  };

  // volumes
  Volume vesselVol(detName, vesselSolid, vesselMat);
  Volume gasvolVol(detName + "_gas", gasvolSolid, gasvolMat);
  vesselVol.setVisAttributes(vesselVis);
  gasvolVol.setVisAttributes(gasvolVis);

  // reference positions
  // - the vessel is created such that the center of the cylindrical tank volume
  //   coincides with the origin; this is called the "origin position" of the vessel
  // - when the vessel (and its children volumes) is placed, it is translated in
  //   the z-direction to be in the proper ATHENA-integration location
  // - these reference positions are for the frontplane and backplane of the vessel,
  //   with respect to the vessel origin position
  auto originFront = Position(0., 0., vesselLength / 2.0);
  auto originBack  = Position(0., 0., -vesselLength / 2.0);

  // sensitive detector type
  sens.setType("photoncounter");


  // BUILD RADIATOR //////////////////////////////////////

  // attributes
  double airGap = 0.01*mm; // air gap between aerogel and filter (FIXME? actually it's currently a gas gap)

  // solid and volume: create aerogel and filter
  Cone aerogelSolid(
      aerogelThickness/2,
      radiatorRmin + boreDelta * aerogelThickness / vesselLength, /* at backplane */
      radiatorRmax,
      radiatorRmin, /* at frontplane */
      radiatorRmax
      );
  Cone filterSolid(
      filterThickness/2,
      radiatorRmin + boreDelta * (aerogelThickness + airGap + filterThickness) / vesselLength, /* at backplane */
      radiatorRmax,
      radiatorRmin + boreDelta * (aerogelThickness + airGap) / vesselLength, /* at frontplane */
      radiatorRmax
      );
  Volume aerogelVol(detName + "_aerogel", aerogelSolid, aerogelMat);
  Volume filterVol(detName + "_filter", filterSolid, filterMat);
  aerogelVol.setVisAttributes(aerogelVis);
  filterVol.setVisAttributes(filterVis);

  // aerogel placement and surface properties
  // TODO [low-priority]: define skin properties for aerogel and filter
  auto radiatorPos = Position(0., 0., radiatorFrontplane - 0.5 * aerogelThickness) + originFront;
  auto aerogelPV = gasvolVol.placeVolume(
      aerogelVol,
      Translation3D(radiatorPos.x(), radiatorPos.y(), radiatorPos.z()) // re-center to originFront
          * RotationY(radiatorPitch) // change polar angle to specified pitch // (FIXME: probably broken, currently not in use)
  );
  DetElement aerogelDE(det, "aerogel_de", 0);
  aerogelDE.setPlacement(aerogelPV);
  // SkinSurface aerogelSkin(desc, aerogelDE, "mirror_optical_surface", aerogelSurf, aerogelVol);
  // aerogelSkin.isValid();

  // filter placement and surface properties
  if (!debug_optics) {
    auto filterPV = gasvolVol.placeVolume(
        filterVol,
        Translation3D(0., 0., -airGap) // add an airgap (FIXME: actually a gas gap)
            * Translation3D(radiatorPos.x(), radiatorPos.y(), radiatorPos.z())  // re-center to originFront
            * RotationY(radiatorPitch) // change polar angle
            * Translation3D(0., 0., -(aerogelThickness + filterThickness) / 2.) // move to aerogel backplane
    );
    DetElement filterDE(det, "filter_de", 0);
    filterDE.setPlacement(filterPV);
    // SkinSurface filterSkin(desc, filterDE, "mirror_optical_surface", filterSurf, filterVol);
    // filterSkin.isValid();
  };


  // BUILD SENSORS ///////////////////////

  // solid and volume: single sensor module
  Box    sensorSolid(sensorSide / 2., sensorSide / 2., sensorThickness / 2.);
  Volume sensorVol(detName + "_sensor", sensorSolid, sensorMat);
  sensorVol.setVisAttributes(sensorVis);

  // sensitivity
  if (!debug_optics)
    sensorVol.setSensitiveDetector(sens);

  // sensor plane positioning: we want `sensorPlaneDist` to be the distance between the
  // aerogel backplane (i.e., aerogel/filter boundary) and the sensor active surface (e.g, photocathode)
  double sensorZpos     = radiatorFrontplane - aerogelThickness - sensorPlaneDist - 0.5 * sensorThickness;
  auto   sensorPlanePos = Position(0., 0., sensorZpos) + originFront; // reference position
  // miscellaneous
  int    imod    = 0;           // module number
  double tBoxMax = vesselRmax1; // sensors will be tiled in tBox, within annular limits

  // SENSOR MODULE LOOP ------------------------
  /* cartesian tiling loop
   * - start at (x=0,y=0), to center the grid
   * - loop over positive-x positions; for each, place the corresponding negative-x sensor too
   * - nested similar loop over y positions
   */
  double sx, sy;
  for (double usx = 0; usx <= tBoxMax; usx += sensorSide + sensorGap) {
    for (int sgnx = 1; sgnx >= (usx > 0 ? -1 : 1); sgnx -= 2) {
      for (double usy = 0; usy <= tBoxMax; usy += sensorSide + sensorGap) {
        for (int sgny = 1; sgny >= (usy > 0 ? -1 : 1); sgny -= 2) {

          // sensor (x,y) center
          sx = sgnx * usx;
          sy = sgny * usy;

          // annular cut
          if (std::hypot(sx, sy) < sensorPlaneRmin || std::hypot(sx, sy) > sensorPlaneRmax)
            continue;

          // placement (note: transformations are in reverse order)
          auto sensorPV = gasvolVol.placeVolume(
              sensorVol, Transform3D(Translation3D(sensorPlanePos.x(), sensorPlanePos.y(),
                                                   sensorPlanePos.z()) // move to reference position
                                     * Translation3D(sx, sy, 0.)       // move to grid position
                                     ));

          // generate LUT for module number -> sensor position, for readout mapping tests
          // printf("%d %f %f\n",imod,sensorPV.position().x(),sensorPV.position().y());

          // properties
          sensorPV.addPhysVolID("module", imod);
          DetElement sensorDE(det, Form("sensor_de_%d", imod), imod);
          sensorDE.setPlacement(sensorPV);
          if (!debug_optics) {
            SkinSurface sensorSkin(desc, sensorDE, "sensor_optical_surface", sensorSurf,
                                   sensorVol); // TODO: 3rd arg needs `imod`?
            sensorSkin.isValid();
          };

          // increment sensor module number
          imod++;
        };
      };
    };
  };
  // END SENSOR MODULE LOOP ------------------------
  //
  // Add service material if desired
  if (detElem.child("sensors").hasChild("services")) {
    xml_comp_t x_service = detElem.child("sensors").child(_Unicode(services));
    Assembly   service_vol("services");
    service_vol.setVisAttributes(desc, x_service.visStr());

    // Compute service total thickness from components
    double     total_thickness = 0;
    xml_coll_t ci(x_service, _Unicode(component));
    for (ci.reset(), total_thickness = 0.0; ci; ++ci) {
      total_thickness += xml_comp_t(ci).thickness();
    }

    int    ncomponents   = 0;
    double thickness_sum = -total_thickness / 2.0;
    for (xml_coll_t ci(x_service, _Unicode(component)); ci; ++ci, ncomponents++) {
      xml_comp_t x_comp    = ci;
      double     thickness = x_comp.thickness();
      Tube       c_tube{sensorPlaneRmin, sensorPlaneRmax, thickness/2};
      Volume     c_vol{_toString(ncomponents, "component%d"), c_tube, desc.material(x_comp.materialStr())};
      c_vol.setVisAttributes(desc, x_comp.visStr());
      service_vol.placeVolume(c_vol, Position(0, 0, thickness_sum + thickness / 2.0));
      thickness_sum += thickness;
    }
    gasvolVol.placeVolume(service_vol,
                          Transform3D(Translation3D(sensorPlanePos.x(), sensorPlanePos.y(),
                                                    sensorPlanePos.z() - sensorThickness - total_thickness)));
  }

  // place gas volume
  PlacedVolume gasvolPV = vesselVol.placeVolume(gasvolVol, Position(0, 0, 0));
  DetElement   gasvolDE(det, "gasvol_de", 0);
  gasvolDE.setPlacement(gasvolPV);

  // place mother volume (vessel)
  Volume       motherVol = desc.pickMotherVolume(det);
  PlacedVolume vesselPV  = motherVol.placeVolume(vesselVol, Position(0, 0, vesselZmin) - originFront);
  vesselPV.addPhysVolID("system", detID);
  det.setPlacement(vesselPV);

  return det;
};

// clang-format off
DECLARE_DETELEMENT(athena_ERICH, createDetector)