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Matthew Bales edited this page Nov 29, 2016 · 9 revisions

mrkgeant

("Matt/Michigan" Runge Kutta with Geant4)

Simulation for RDK II experiment.

Summary

For simulating particle transport and material interaction in the RDK II experiment which measured radiative neutron decay. The simulation focuses on the RDK II apparatus and simulates electrons, protons, and photons from neutron decay or calibration isotopes. The results of a simulation is a ROOT file which typically contains a single ROOT tree. The tree is an event by event representation of the detection by the surface barrier detector (SBD), bismuth germanium oxide (BGO) detectors, and bare avalanche photo-diode (bAPD) detectors.

Features

  • Models for complete RDK II geometries, calibration geometries, and simplified test geometries.
  • Various integrators such as Fourth Order Runge Kutta to precess charge particles in electromagnetic fields.
  • Variable geometry settings can be adjusted dynamically such as thicknesses of various SBD layers.
  • Interpolated (linear or cubic) fields in txt and ROOT formats for:
    • Magnetic solenoid field
    • Electrostatic mirror field
    • Electric bias on SBD
  • Neutron event generation using von Neuman rejection (rejection sampling) and JTW/Gapanov equations for non-radiative (3 body) and radiative (4 body) decays.
  • Model for bAPD energy response to photons
  • Model for positional BGO energy response to photons
  • All standard physical modes and settings available to Geant4

Dependencies

  1. Geant4
  • Tested with versions 4.9.6.p02 - 4.10.02.p01. Download.
  • The simulation originated from heavily modified Geant4 examples.
  • This product includes software developed by Members of the Geant4 Collaboration ( http://cern.ch/geant4 ).
  1. ROOT
  • Tested with version 5.34.36.
  • Utilized for file input and output.

Operation Instructions

To run a simulation in interactive mode simply run:

mrkgeant

To run a simulation based on a macro file:

mrkgeant <ASCII txt file>

Example macro files can be found in the macros directory of this repository. In addition to standard Geant4 macro commands, MRK specific commands are defined within the various "Messenger" classes.

Geometry

Simple diagram cross section of the RDK II

Example neutron decay event with electron, proton, and photon tracks.

Blown-up surface barrier detector (SBD)

Simulation workflow

This diagram shows the typical process of using mrkgeant to investigate questions in the RDK 2 experiment.

Analysis code

Analysis of the result ROOT files generated by mrkgeant was primarily performed using rdk2analysis code.

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