Opticks : JUNO PMT Modelling Issue

• Hamamatsu PMT Solid breaking Opticks
  • CSG tree height 8 : TOO DEEP
  • PROFLIGATE : G4ItersectionSolid Z-Cut
  • SOLUTION : ZSolid::ApplyZCutTree : Actually Cut the CSG Tree
• Tools for development of solution ZSolid::ApplyZCutTree
  • PMTSim::GetSolid PMTSim::GetPV
  • X4IntersectTest
  • ZSolid::ApplyZCutTree algorithm
• new Opticks pkg : GeoChain
  • single executables handle full chain of geometry conversions

Hamamatsu PMT Solid breaking Opticks : CSG tree height 8 : TOO DEEP

ZSolid::Draw [-1] nameprefix _body_solid_  NODE:19 PRIM:10 UNDEFINED:19 EXCLUDE:0 INCLUDE:0 MIXED:0 Order:IN                            Int
                                                                                                                                        U
                                                                                                                                        17

                                                                                                                        Uni                     Pol
                                                                                                                        U                       U
                                                                                                                        15                      18

                                                                                                        Uni                     Pol
                                                                                                        U                       U
                                                                                                        13                      16

                                                                                        Uni                     Pol
                                                                                        U                       U
                                                                                        11                      14

                                                                        Uni                     Ell
                                                                        U                       U
                                                                        9                       12

                                        Uni                                     Pol
                                        U                                       U
                                        5                                       10

                        Uni                             Sub
                        U                               U
                        3                               7

        Uni                     Ell             Pol             Tor
        U                       U               U               U
        1                       4               6               8

Ell             Pol
U               U
0               2

0.0             -2.5            -5.0            -179.2          -210.0          -242.5          -275.0          -385.0          -420.0          3.4     zdelta

190.0           0.0             -5.0            -148.4          -130.0          -210.0          -275.0          -350.0          -420.0          190.0   az1
0.0             -5.0            -195.0          -210.0          -290.0          -275.0          -365.0          -420.0          -450.0          -183.2  az0

I       1_2     II      1_3     III     1_4     IV_tub  IV      IV_tor  1_5     V       1_6     VI      1_8     VIII    1_9     IX      cut     intubs

• ZSolid::Draw Uni:Union Ell:Ellipsoid Pol:Polycone Tor:Torus Int:Intersection Sub:Subtraction
• 19 Nodes, 10 prims, depth 8 Use of G4IntersectionSolid to make z-cut prevents tree balancing

Hamamatsu PMT Solid : PROFLIGATE G4ItersectionSolid Z-Cut

Using G4IntersectionSolid to apply Z-cut to PMT

• very convenient cut solid definition
• BUT EXCEEDINGLY EXPENSIVE (PROFLIGATE) : and it breaks Opticks geometry
• every single intersect must traverse CSG tree checking intersects with multiple cutaway constituent primitives
• -> pay the price of convenient solid definition easily millions of times per event

485     // Reduce the size when real surface is enabled.
486     // Tao Lin, 09 Aug 2021
487     if (m_useRealSurface ) {
...
546         const double body_height = m_pmt_h;
547         const double body_half_height = body_height / 2;
548         const G4ThreeVector cut_body_displacement(0., 0., m_z_equator-pmt_half_height);
549         G4VSolid* cut_body_solid = new G4Tubs( GetName() + "_body_solid_intubs",
550                                               0.,
551                                               helper_sep_tube_r+1E-9*mm,
552                                               body_half_height,
553                                               0., 360.*degree);
554         body_solid = new G4IntersectionSolid( GetName() + "_body_solid_cut",
555                                                 body_solid,
556                                                 cut_body_solid,
557                                                 NULL,
558                                                 cut_body_displacement);

SOLUTION ACTUALLY CUT THE CSG TREE using https://github.com/simoncblyth/j/blob/main/PMTSim/ZSolid.hh

G4VSolid* ZSolid::ApplyZCutTree( const G4VSolid* original, double zcut)

j/PMTSim : Standalone Provider of JUNO PMT Solids and Volumes

• https://github.com/simoncblyth/j/tree/main/PMTSim
• Extracted just the offline code needed to create materials, Hamamatsu PMT solids+volumes

G4VSolid* body_solid = PMTSim::GetSolid("body_solid");
G4VSolid* inner1_solid = PMTSim::GetSolid("inner1_solid");

G4VPhysicalVolume* body_phys = PMTSim::GetPV("body_phys");

• convenient standalone access to solids and volumes
• easy to change modelling and check results

X4IntersectSolidTest : Geant4 2D cross-sections of single G4VSolid

• https://bitbucket.org/simoncblyth/opticks/src/master/extg4/xxs.sh
• https://bitbucket.org/simoncblyth/opticks/src/master/extg4/tests/X4IntersectSolidTest.cc
• https://bitbucket.org/simoncblyth/opticks/src/master/extg4/tests/X4IntersectSolidTest.py

1. get G4VSolid from j/PMTSim with PMTSim::GetSolid
2. SEvent::GenerateCenterExtentGenstepsPhotons creates grid of 2D planar "rays"
3. X4Intersect::scan uses X4Intersect::Distance and collects intersect positions into NP array
4. X4IntersectSolidTest.py presents the intersect positions with scatter plots

G4double X4Intersect::Distance(const G4VSolid* solid,
          const G4ThreeVector& pos, const G4ThreeVector& dir)
{
    EInside in =  solid->Inside(pos) ; G4double t = kInfinity ;
    switch( in ) {
        case kInside:  t = solid->DistanceToOut( pos, dir ) ; break ;
        case kSurface: t = solid->DistanceToOut( pos, dir ) ; break ;
        case kOutside: t = solid->DistanceToIn(  pos, dir ) ; break ; }
    return t ;
}

body_solid

• default G4Tubs-G4Torus neck has spurious G4 intersects

body_solid_nurs

• still spurious neck intersects after G4IntersectionSolid cut

body_solid_nurs_pcnk

• G4Polycone neck avoids the spurious intersects

body_solid_pcnk

j/PMTSim : ZSolid::ApplyZCutTree

G4VSolid* ZSolid::ApplyZCutTree(const G4VSolid* orig, double zcut)

G4BooleanSolid* src = dynamic_cast<G4BooleanSolid*>(node) ;
G4String name = src->GetName() ;
G4VSolid* left = src->GetConstituentSolid(0) ;

G4SolidStore::GetInstance()->DeRegister(src);

src1 = new (src) G4UnionSolid(name, left, new_right)
assert( src1 == src );

https://github.com/simoncblyth/j/blob/main/PMTSim/ZSolid.hh

Applying Z-cut to G4VSolid CSG Tree

1. classify tree nodes INCLUDE/EXCLUDE against Z-cut
2. identify "crux" nodes dividing INCLUDE/EXCLUDE subtrees
3. prune at crux nodes by tree surgery reconnections
4. repeat until all tree nodes are INCLUDE

Pruning and Reconnection

• pruning at non-root "crux" node
  • identify surviving child
  • change crux parent Left/Right to the survivor
• pruning at root "crux" node
  • identify surviving child
  • change root to the survivor

ZSolid::ApplyZCutTree classify tree nodes against Z-cut

ZSolid::apply_cut before prune [ 0] nameprefix maker_body_solid_zcut-183.2246_  NODE:15 PRIM:8 UNDEFINED:0 EXCLUDE:4 INCLUDE:7 MIXED:4 Order:IN
                                                                                                        Uni
             I : include                                                                                IE
                                                                                                        13
             E : exclude
                                                                                        Uni                     Pol
             IE: mixed include/exclude                                                  IE                      E
                                                                                        11                      14
             X : "crux" node
                                                                        Uni                     Pol
             S : survivor node                                          IE                      E
                                                                        9                       12

                                                        Uni                     Ell
                                                        IE                      E
                                                        7                       10
                                                        X
                                        Uni                     Pol
                                        I                       E
                                        5                       8
                                        S
                        Uni                     Pol
                        I                       I
                        3                       6

        Uni                     Ell
        I                       I
        1                       4

Ell             Pol
I               I
0               2

0.0             -2.5            -5.0            -179.2          -242.5          -275.0          -385.0          -420.0  zdelta

190.0           0.0             -5.0            -162.0          -210.0          -275.0          -350.0          -420.0  az1
0.0             -5.0            -183.2          -183.2          -275.0          -365.0          -420.0          -450.0  az0

I       1_2     II      1_3     III     1_4     IV      1_5     V       1_6     VI      1_8     VIII    1_9     IX

ZSolid::ApplyZCutTree : (2) prune + reconnect tree

tree::apply_cut after prune and re-classify [ 3] nameprefix maker_body_solid_zcut-183.2246_  NODE:7 PRIM:4 UNDEFINED:0 EXCLUDE:0 INCLUDE:7 MIXED:0 Order:IN

                                        Uni
                                        I
                                        5
                                        S

                        Uni                     Pol
                        I                       I
                        3                       6


        Uni                     Ell
        I                       I
        1                       4


Ell             Pol
I               I
0               2


0.0             -2.5            -5.0            -179.2  zdelta

190.0           0.0             -5.0            -162.0  az1
0.0             -5.0            -183.2          -183.2  az0
I       1_2     II      1_3     III     1_4     IV

• MAJOR SIMPLIFICATION tree cut from (node:15, prim:8, height:7) -> (node:7, prim:4, height:3)
• "cutting" with G4IntersectionSolid increases tree to (node:17, prim:9, height:8 )

maker_body_solid_zcut-500.0

maker_body_solid_zcut-400.0

maker_body_solid_zcut-350.0

maker_body_solid_zcut-300.0

maker_body_solid_zcut-200.0

maker_body_solid_zcut-183.25

maker_body_solid_zcut-100.0

maker_body_solid_zcut-0.0

maker_body_solid_zcutp100.0

X4IntersectVolumeTest : Geant4 2D cross-sections of G4VPhysicalVolume

• https://bitbucket.org/simoncblyth/opticks/src/master/extg4/xxv.sh
• https://bitbucket.org/simoncblyth/opticks/src/master/extg4/tests/X4IntersectVolumeTest.cc
• https://bitbucket.org/simoncblyth/opticks/src/master/extg4/tests/X4IntersectVolumeTest.py

G4VPhysicalVolume has no convenient "Distance" methods ... so scan solids individually and present together after applying structure transforms.

1. get G4VPhysicalVolume from j/PMTSim with PMTSim::GetPV
2. collect and save structure transforms PMTSim::SaveTransforms for each solid
3. X4Intersect::Scan each solid and persist in NP arrays
4. present together using X4IntersectVolumeTest.py

• Gives rapid 2D cross-sections of G4PhysicalVolume (very little Opticks code used)

Usage of xxv.sh script which runs executable and ipython:

cd ~/opticks/extg4
./xxv.sh
GEOM=body_phys ./xxv.sh

body_phys_nurs

• spurious Geant4 intersects from G4Tubs-G4Torus neck

body_phys

• spurious Geant4 intersects from G4Tubs-G4Torus neck

body_phys_nurs_pcnk

• G4Polycone neck : simpler, faster, no-spurious intersects

body_phys_nurs_pcnk_pdyn

• with dynode geometry included and G4Polycone neck

body_phys_nurs_pdyn

• with dynode geometry and default G4Tubs-G4Torus neck

body_phys_pdyn

• with dynode geometry and default G4Tubs-G4Torus neck

body_phys_pdyn_pcnk

GeoChainSolidTest : single solid full chain of geometry conversions

opticks/GeoChain

new package for fast iteration geometry debugging by doing all geometry conversions in single executables

• https://bitbucket.org/simoncblyth/opticks/src/master/GeoChain/tests/GeoChainSolidTest.cc

The solid to create is controlled by the name string obtained from envvar GEOM

1. creates G4VSolid directly or from j/PMTSim
2. invokes GeoChain::convert
   • (x4) X4PhysicalVolume::ConvertSolid : G4VSolid -> nnode -> GMesh/GPts
     • X4Solid::Convert converts G4VSolid into npy/nnode tree
     • NTreeProcess<nnode>::Process balances the nnode tree when that is configured
     • NCSG::Adopt wrap nnode tree enabling it to travel
     • X4Mesh::Convert converts G4VSolid into GMesh which has above created NCSG associated
   • (this) using placeholder GVolume the GMesh is added to a test GGeo
   • (cg) CSG_GGeo_Convert GGeo -> CSGFoundry
3. saves geometry to $TMP/GeoChain/$GEOM/CSGFoundry/ (OptiX 7 compatible)

Subsequently can render this geometry, eg with CSGOptiX/cxs.sh using just the path to the CSGFoundry directory.

GeoChainVolumeTest : volume full chain of geometry conversions

• volume could be single PMT or full geometry
• https://bitbucket.org/simoncblyth/opticks/src/master/GeoChain/tests/GeoChainVolumeTest.cc
• using existing opticks/extg4/X4PhysicalVolume functionality

WIP : Integrating ZSolid with j/PMTSim and then offline/PMTSim

• tidy up ZSolid and j/PMTSim
• integrate ZSolid into j/PMTSim in a manner appropriate for use from actual offline/PMTSim (much faster to test in j/PMTSim so keep development there until close to finalization)

DONE

• returned Hamamatsu_R12860_PMTSolid to minimally changed state
• add NNVT PMT to j/PMTSim
• move to STANDALONE being used just for making the class usable in standalone fashion
• review diffs between PMT classes in j and offline
• added jdiff for getting diff commands
• remove the tubs minus torus by making polycone neck non-optional
• stagger the zcut for the layers of PMT volume (via "thickness" offset) to avoid ambiguous edge
• renamed IGeomStandalone.h to IGeomManager.h as the simple protocol base could be useful beyond just STANDALONE testing
• removed polycone neck control as now standard
• DECIDED : j/PMTSim class is just for testing, but should it be in offline anyhow ? Hmm uses NP, so NO for now.
• DECIDED : OK for Opticks API export stuff needed for om-compilation to be hidden behind STANDALONE within offline code
• DECIDED : useful functionality should not be hidden behind STANDALONE

TODO

• check compilation of updated PMT geometry code + ZSolid etc within offline/PMTSim environment
• check Opticks operation with the simplified PMT CSG
• what/where to switch to new PMT geometry, how much backward test support
  • jgr HamamatsuR12860PMTManager
  • suggests trying to switch between Old and New versions of a manager would be difficult because the name string is hardcoded all over the place : so that means that if want to support switching between old and new geometry approaches, then need to do it within the manager