Introducing radiation dose / fluence recording

[blackcathj]

Introduction

Geant4 tool kit has a built in tool, G4ScoringManager, to record radiation dose and fluence by analyzing passage and interaction of particle tracks with user defined x-y-z or cylindrical meshed volumes.

This pull request introduce interface to G4ScoringManager, configuring it to run with full sPHENIX/EIC simulation and record the result for further analysis.

In addition, related updates include:

• Added a switch to disable stepping actions with PHG4Reco::setDisableSteppingActions(). Stepping action produce the PHG4Hits which interface to the rest of Fun4All based analysis. Disabling it make dose focused simulation run much faster and use smaller memory foot print.
• Example macro to drive the dose simulation: https://github.com/blackcathj/macros/blob/dose_tests/macros/g4simulations/Fun4All_G4_sPHENIX.C
• Macros to plot the result: https://github.com/sPHENIX-Collaboration/analysis/blob/master/Fluence/DrawFluence.C

Tests

• This new feature is tested with 10k simulations of 0-20 fm sHIJING events, which produce an average dN_ch/deta of 170-180 in the central pseudorapidities:
  
• 30-cm wide vertex-z distribution is used. The test result used flat distribution and the example macro above is fixed with Gaussian distribution.
• The pre-packaged QGSP_BERT_HP physics list is used in Geant4. All currently implemented sPHENIX parts are enabled, including the forward plug door.
• All results are scaled up to 1.5 Trillion AuAu collisions, which corresponding to the AuAu portion of the five year sPHENIX operation as in sPH-TRG-2018-001

Please note the result is not yet verified with any existing RHIC background measurement. They just provide a preview for the new functionality, rather than radiation estimation for sPHENIX.

Radial-z graphs

From left top to right bottom:

• Right top: Total energy deposition in each radial-z bins. Bin size is 2x2 cm
• Right bottom: Radiation dose in rad
• Left top: charged particle fluence with minimal kinematic energy cut of 1 MeV
• Left bottom: neutron fluence with minimal kinematic energy cut of 0.1 MeV

Radial averages

In the central region, the dose and fluence is mostly radially dependent. Therefore, within |z|<30 cm, the average radial dependence is extracted:

Next

The most important steps prior to producing reliable result are verification and tuning.

Tuning include

• Try different physics list, with reference to radiation studies by other collaborations
• Add experimental hall and other known support structures such as beam and electronics elements in the vertex region.

Verification include

• Cross check with PHENIX radiation monitor data installed near the vertex region.
• Cross check with the STAR results: DOI:10.1016/j.nima.2014.04.035

It will also be nice to show it for sPHENIX-EIC setup too.

Suggestions and helps in carrying out such studies are welcomed.