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---+ PIONEER Beamline Simulations
---+++ Intro to G4beamline

<span style="background-color: transparent;">The PIONEER beamline simulation is built using G4beamline (</span><span style="background-color: transparent;">G4BL</span><span style="background-color: transparent;">), a free open-source toolkit built on top of GEANT4. The latests (3.06) source and prebuilt binaries can be downloaded from </span><a href="http://www.muonsinternal.com/muons3/G4beamline" target="_blank">here</a><span style="background-color: transparent;">. Included in the download is the comprehensive user's guide (</span><span style="background-color: transparent;">G4beamlineUsersGuide</span><span style="background-color: transparent;">.pdf) that is immensely useful when getting started.</span>

An overview guide for the PIONEER simulation is available <a href="https://pioneer.npl.washington.edu/cgi-bin/private/ShowDocument?docid=75" target="_blank">here</a>.

Every G4beamline simulation script needs at minimum a physics definition and beam definition. Beyond that, the user can define their own parameters using the param keyword along with the -unset option to allow the param to be overriden later in the script. Users can also build assets using predefined devices or custom boolean geometries and place these in the world using the place command.
---+++ The &pi;E5 beamline in G4beamline

The &pi;E5 simulation in G4BL was originially developed for the Mu3e Compact Muon Beam Line (CMBL), and has been modified for use in the MEGII experiment, and now for the PIONEER experiment. The magenetic elements in the simulation (quadrupoles, dipoles, sextupoles) rely on either existing field maps or calculations from geometry and coil windings. The QSK and HSC elements do not have field maps, and the QSF elements use the QSM field map.

The simulation relies on several pre-defined files in the original piE5 simultion.
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   * Positions.txt &gt;
      * In world element positions
   * feldxxx.dat
      * Magnetic field maps, should not be edited
   * Scalefactors.txt
      * Current scaling and set values
   * DeltaCurrents.txt<br />
      * Current offsets, none used As well as one file for PIONEER specific placements: PositionsPIONEER.txt [[PositionsPIONEER][<br />]]
</div> <div title="Page 7">The &pi;E5 G4BL scripts and field maps are available <a href="https://gitlab.com/zhodge/pie5" target="_blank">here</a>.</div> <div title="Page 7">The PIONEER G4BL example scripts for pion production and pion transport simulations are available <a href="https://gitlab.com/zhodge/g4bl_pioneer_example" target="_blank">here</a>.</div>
---+++ Using the HiMB Pion Production Model

The HiMB Pion Production Model implemtents a parameterized production cross section the details of which are described <a href="https://journals.aps.org/prab/abstract/10.1103/PhysRevAccelBeams.19.024701" target="_blank">here</a>. G4Beamline must be built from source and the GEANT4 and G4Beamline source modification must be applied before building. The HiMB model source code is available <a href="https://gitlab.com/zhodge/g4bl_himbmodel" target="_blank">here</a>.

The model can be enabled through the physics command in G4BL.
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=physics QGSP_BIC_HIMB_HYBRID_HP_EMY=
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The model also provides a mechanism for biasing or splitting pions to generate a larger sample of pions and muons produced from proton interactions in the production target. This splitting can be enabled by the following command in the G4BL script:
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=physics QGSP_BIC_HIMB_HYBRID_HP_BIAS_EMY splittingFactor=100=

where the splitting factor can be defined by the user. A factor of N generates an additional N pions from proton interactions and N muons from pion decay.

<span style="background-color: transparent;">-- </span><span style="background-color: transparent;">%USERSIG{ZacharyHodge - 2022-03-04}%</span>
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---++ Comments

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Topic revision: r7 - 2022-03-04 - ZacharyHodge
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