Simulations and Backgrounds

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GEANT4 vs. Experimental Data

  • Benchmarking of monte carlo simulation of bremsstrahlung from thick targets at radiotherapy energies

B. A. Faddegon, M. Asai, J. Perl, C. Ross, J. Sempau, J. Tinslay, and F. Salvat. Med. Phys. 35 (2008) 4308 media:MedPhys.35.4308.pdf


GEANT4 Geometry

  • Using github.com to manage the simulation software: /group/bubble/
  • The current geometry for the Bubble Chamber is in gdml and is shown below:

BCjul7.jpeg


BC1jul7.jpeg


  • To-do List:
  1. Geometry is in gdml format, need to get correct Radiator, Collimator, Beamline, PhotonDump geometry.
  2. Add sweep magnet and electrondump geometry in gdml format.
  3. Complete: Include the Bubble Chamber geometry using the Bubble Chamber STEP file (change .txt to .stp): media:BubbleChamber.txt.
    1. Geometry has been created and is on github, BubbleMother.gdml and all daughter files
  4. The beamline STEP file will be ready very soon. When? Last file recieved was BubbleChamber again 6_24_2014.
  5. GEANT4 uses models that calculate wrong photo–nuclear cross sections (see below). GEANT4 does not allow for user’s cross sections. What to do?
    1. Use GEANT4 to produce the photon spectra impinging on the superheated liquid.
    2. Fold the above photon spectra with our cross sections in stand-alone codes.
    3. Could we not create a correct physicslist.cc in geant4 instead?
  • GEANT4 Photon-Inelastic Model: CHIPS Gamma Nuclear has this cross section for our reaction:

G4 CrossSection.gif

  • The simulation below is outdated and doesnt work with gdml. See github for correct version.
  • Quick start for the simulation: media:G4_BubbleEx_README.txt. There is also a README file that comes with the example.
  • Bubble Chamber GEANT4 Example (change .txt to .tar): media:BubbleEx96.txt

Compiling/Running Simulation (BubbleEx)

  • Using the ifarm or jlabl1 nodes
  • Login remotely to the JLab gateway: $ ssh login.jlab.org
  • Connect to either ifarm or Jlabl4:
  1. $ ssh ifarm
  2. $ ssh jlabl4
  • Load Geant4 and ROOT Environments by running the following commands: (needed every login)
  1. $ setenv JLAB_VERSION 1.0 (or 1.1)
  2. $ setenv JLAB_ROOT /site/12gev_phys
  3. $ source ${JLAB_ROOT}/${JLAB_VERSION}.csh
  • Should see a short list of programs such as ROOT and Geant4 listed
  1. $ mkdir /group/bubble/<user>
  2. $ cd /group/bubble/<user>
  3. $ git clone https://github.com/JeffersonLab/BubbleEx.git
  4. $ cd BubbleEx
  5. $ git pull (to update files from github)
  6. $ mkdir build
  7. $ cd build
  8. $ use cmake (only if using JLab nodes)
  9. $ cmake ..
  10. $ make
  11. $ cd ..
  • Running the simulation
  • In the install directory
  1. $ build/BubbleEx (remember to run the source command before running)
  • Terminal will list what has been loaded and then display output command box
  • In session run:
  1. $ /vis/open OGL
  2. $ /run/beamOn 100
  • Initial run of the simulation is shown:

BubbleEx Output.jpg



Relevant Cross Sections

  • Photo-Nuclear Cross Sections:
CrossSections.gif
  1. 16O(γ,α)12C media:cs16Oga.txt (Eg (MeV), Cross Section (b))
  2. 17O(γ,α)13C media:cs17Oga.txt
  3. 18O(γ,α)14C media:cs18Oga.txt
  4. 14N(γ,p)13C media:cs14Ngp.txt


  • Neutron Elastic Cross Sections:
  1. 16O(n,n) media:cs16Onn.txt (En (MeV), Cross Section (b))
  2. 14N(n,n) media:cs14Nnn.txt
Cs16Onn.gif
Cs14Nnn.gif