BMAD based g-2 tracking code

Running g2_tracking

• Running g2_tracking interactively

  • Field maps, geometry, detector layout, etc. are accessed via additional files. The files are in the Cornell svn repository. Check out the files that you will need to run g2_tracking. You will probably want to create a new directory as the top of the g-2 directory tree. A good name for the directory is < bmad_dist >
    Go to bmad_dist and type svn co https://accserv.lepp.cornell.edu/svn/trunk/src/g-2/ (Here is a description of the g-2/ directory tree)
  • Create a working directory. Let's call is <bmad_work> in <bmad_dist>
  • go to <bmad_work> and type ../bmad_dist/g-2/files/softlink_lnx . This will create a soft link to all but two of the files you will need. It includes, lattice file extensions, field maps as well as various muon distributions etc, and the executable. Here is the list:

    ln -s /home/dlr/development9_linux/g-2/files/pulse_127cm.dat
    ln -s /home/dlr/development9_linux/g-2/magneticfield/ring_inject_bfield3d_wuzheng_extended.dat 
    ln -s /home/dlr/development9_linux/g-2/magneticfield/inf_field_alone.dat 
    ln -s /home/dlr/development9_linux/g-2/files/muons/VDstop_DS_436_12000.dat 
    ln -s /home/dlr/development9_linux/g-2/files/muons/particles_endm4m5_100.txt
    ln -s /home/dlr/development9_linux/g-2/files/muons/particles_M4M5End_400_mod.txt
    ln -s /home/dlr/development9_linux/g-2/files/KICKER_E989_NoRolledEdges.dat 
    ln -s /home/dlr/development9_linux/g-2/files/quads/
    ln -s /home/dlr/development9_linux/g-2/files/quad_curvilinear/
    ln -s /home/dlr/development9_linux/g-2/files/quad_curvilinear_single_plate/ 
    ln -s /home/dlr/development9_linux/g-2/files/calorimeter_lattice.
    ln -s /home/dlr/development9_linux/g-2/files/fiber_monitor_lattice.
    ln -s /home/dlr/development9_linux/g-2/files/walls_free.bmad
    ln -s /home/dlr/development9_linux/g-2/files/walls_quads2-4.bmad
    ln -s /home/dlr/development9_linux/g-2/files/backleg/
    ln -s /home/dlr/development9_linux/g-2/files/bmad_all_configs_fringe_inf_grid.
    ln -s /home/dlr/development9_linux/g-2/files/bmad_grid_fringe_inf.bmad
    ln -s /home/dlr/development9_linux/g-2/files/bmad_grid_fringe_inf_custom.bmad
    ln -s /home/dlr/development9_linux/g-2/magneticfield/BrFourier2016.dat
    ln -s /home/dlr/development9_linux/g-2/magneticfield/BzFourier20170628_LogID983.dat
    ln -s /home/dlr/development9_linux/g-2/files/g-2_FFT_04032015.lat
    ln -s /home/dlr/development9_linux/g-2/files/g-2_FODO_04032015.lat
    ln -s /home/dlr/development9_linux/g-2/files/parameters_g-2_03112015.lat
    ln -s /home/dlr/development9_linux/g-2/field_maps/kicker1data.txt
    ln -s /home/dlr/development9_linux/g-2/field_maps/kicker1data_halftail.txt
    ln -s /home/dlr/development9_linux/g-2/field_maps/kicker1data_05_tail.txt
    ln -s /home/dlr/development9_linux/g-2/field_maps/kicker1data_flattop.dat
    ln -s /home/dlr/development9_linux/g-2/files/pulse_shapes/
    ln -s /home/dlr/development9_linux/g-2/files/fiber_energy_loss/eloss.dat
    ln -s /home/dlr/development9_linux/g-2/field_maps/v0/
    ln -s /home/dlr/development9_linux/g-2/files/pulse_shapes/avgBeamPulsePDF.txt
    ln -s /home/dlr/development9_linux/production/bin/g2_tracking
    

  • The main lattice file is bmad_all_configs_fringe_inf_grid. It is the starting point for essentially all studies. By commenting (uncommenting) various calls it can be configured to
    • Begin tracking in M5 line, or at the entrance to the backleg iron, or at the inflector exit
    • Use alternative representations of the quad fields
      • Cartesian 2-D map
      • Cartesian multipoles (with or without fringe fields)
      • Cylindrical 2-D map
      • Cyindrical multipoles (with or without fringe fields)
    • Record fiber harp hits
    • Record calorimeter hits
    • Define various apertures
    • etc.
    If you choose to modify the basic lattice then copy the file to <bmad_work/> from ../bmad_dist/g-2/files/. For example if you want to collect fiber harp hits, the find the line !call, file = fiber_monitor_lattice. and remove the ! There are several example configurations in /bmad_dist/g-2/examples/ with lattice and input file that you can use as a starting point. See Examples .
  • Edit the input.dat file as you like. See Input for details.
  • Assuming there is a locally compiled executable available now is the time to run it.
    • Type /whatever the path is/bin/g2_tracking (If you are at Cornell you can use /home/dlr/development9_linux/production/bin/g2_tracking. If you are at Fermilab try /gm2/app/users/drubin/bmad_dist_fix/production/bin/g2_tracking. Anywhere else and you will have to build your own executable. See Acquiring g-2 (and bmad) code.)
    • A new subdirectory is created named with date and time of start of the run and all of the output files are written into that directory.
    • Description of the Output is here.
    • And some gnuplot plotting_scripts are listed here.
    • The standard output can be directed as you prefer.

  ---

• Running g2_tracking on the Fermi grid.

  • Here are the instructions

Suggestions, hints, commentary
• The input file is fortran namelist format and is not particularly good at identifying typos. When the program starts, it reads input.dat and then prints what it read to the terminal. It is good practice to compare the terminal output to the input. If they do not agree there is probably a typo in the input.dat file

---

Bmad code development

You can download all of the bmad and g-2 code and build locally. That way you can tailor the code to your requirements.

• Acquiring g-2 (and bmad) code.

  g-2/ directory tree
  • programs subdirectory - main programs (tracking_master,analyze_harp, analyzer_Time_dep)
  • code subdirectory - subroutines
  • files subdirectory - data files
  • Field maps
  • plotting_scripts subdirectory - plotting_scripts
  • documentation subdirectory - This file, tex document, Dependence of spin on energy, etc.
  • Example input files
  • test subdirectory - Everything you need for a test run
• Executables: In addition to the main g-2 ring simulation program called g2_tracking there are a few other programs for various analysis tasks
  • g2_tracking
    • Input
    • Output
    • Test Run
    • Example input files
    • Things you can calculate
  • analyze_harp
    • Input
    • Output
    • Example Test Run

  ---

• Other stuff
  • Environment Variables
  • Structures
  • Bmad references. Includes links to BMAD manual, etc.

Acquisition Within Wilson Lab of code from the Wilson accelerator code repository

1. If you have not done this already, make a directory for your local copy of the Bmad (g-2) distribution, programs, etc. Henceforth this directory will be referred to as < DIR >. A possible name might be: "root_dir". Substitute the appropriate directory name for " < DIR >" in the following steps.

2. To make a local copy of a directory, the commands:
   

      cd < DIR >
      svn co https://accserv.lepp.cornell.edu/svn/<REPOS_PATH>.
   

   To find the correct < REPOS_PATH >, use the repository web viewer. For example. to make a local copy of the bmad library, use the commands:

   
     cd <DIR>
     svn co https://accserv.lepp.cornell.edu/svn/trunk/src/g-2
   

   This will create the directory <DIR>/g-2

3. To update your local copy of a library and/or executable so that it has all the revisions that have been introduced into the repository, go to the directory containing the library and/or executable and use the command:
   

      svn update

4. To compile the library: (see Environment Variables)
   

   cd <DIR>/g-2
   mk          # Produces production libraries and/or executables

   
   Or use "mkd" instead of "mk" if you want to the debug versions of the libraries and/or executables.
   

   Production libraries and executables are put in the directory:
   

   <DIR>/production
   

   and debug libraries and executables are put in:
   

   <DIR>/debug

For offsite acquisition and installation see

g-2/ directory tree

• cmake.g2_tracking - program that tracks a distribution of muons through final focus, injection channel and into ring
• cmake.ering - program for testing energy dependence of omega a
• cmake.EnergyDispersion - for computing sums in g-2 E989 Note 86 GM2-doc 4098-v2
• cmake.fieldmap_test - program with all standard bmad routines to parse lattice with quad grid fields like g-2/files/quads/bmad_test.
• cmake.read_quad_grid - program to read FEMME file of potentials and to compute gradient and write bmad readable grid file
• cmake.analyze_harp - program to analyze harp data. Reads harp_plane_hits.dat which is generated by g2_tracking, computes beam moments vs time and FFT of moments. Some sample output fiber harp data

The executables are: g2_tracking, analyze_harp, EnergyDispersion, fieldmap_test, read_quad_grid, and a few others  

• /programs Back
  The main program for the g2_tracking executable tracking_master.f90 is here. This program attempts to incorporate all of the physics of the g-2 storage ring including
  • Generating the phase space of a muon distribution
  • Tracking through the injection channel, hole through iron, then fringe field and inflector with scattering in inflector windings etc. Magnetic fields in the injection line (fringe and inflector) are based on fields maps.
  • Computing Jacobian of the mapping through the injection channel and propagating twiss parameters
  • Propagation into the storage ring and through the pulsed kicker magnets and then around the ring.
    • Quads fields are represented as a 2D map or in terms of multipole expansion.
    • Kicker field is based on a map.
    • The field of the g-2 magnet is assumed uniform to lowest order. Measured field errors can be incorporated as fourier expansion.
    • The one turn map is computed by tracking.
    • Closed ring twiss parameters are computed or twiss parameters at inflector exit are propagated.
    • Spin tracking is enabled as an option
    • Muon decay is also optionally enabled.
    • Tracking of decay positrons to calorimeter or tracker planes is optionally enabled
  The program analyze_harp.f90 is for post-processing fiber harp data from g2_tracking.
• /ering
  Main program ering.f90 and related subroutines for the ering executable for simulation of a ring with uniform vertical magnetic field and radial electric field and no quadrupoles to test spin tracking is here.
• /code Back
  
  • Muon decay
    • DecayElectron.f90
    • MuonDecayInterface.f90 ---
    • compute_decayTime.f90 ----
    • muondecay.f90 ---
    • rotations.f90 ---
    • track_electron.f90 ---
    • transform_muon.f90 ---
  • Phase space
    • compute_moments.f90 --- Calculates average positions, standard deviations and corresponding twiss aprameters
    • create_phase_space.f90 ---
    • plot_twiss_data_mod.f90 ---
    • qp_read_twiss_data.f90 ---
    • twiss_propagate_cm.f90 ---
  • Magnetic and electric fields
    • track1_preprocess.f90 --- Quad ramping, apertures for positrons vs muons, etc.
    • em_field_custom.f90 ---
    • em_field_custom_inj.f90 ---
    • em_field_interface.f90 ---
    • fieldMaps.f90 ---
    • fields.f90 --- Returns dipole and kicker magnetic fields and quadrupole electric fields as a function of position (and time for the kicker)
    • get_g2_fields_new.f90 ---
    • interpolate_field.f90 ---
    • magfield_interface.f90 ---
    • magfield_mod.f90 ---
    • quadratic_fit.f90 ---
    • read_field.f90 ---
    • sum_fields.f90 ---
  • Transfer matrices
    • create_taylor_ele.f90 ---
    • get_branch_inv_matrix.f90 ---
    • write_transfermatrix.f90 ---
    • get_quad_locs.f90 ---
  • Scattering
    • materials_mod.f90 ---
    • wall_hit_handler_custom.f90 ---
  • Optimization
    • optimize_incident.f90 ---
    • optimize_twiss.f90 ---
  • IO
    • create_gnu_input.f90 ---
  • Modules
    • muon_interface.f90 --- Subroutine interface blocks
    • muon_mod.f90 --- Structures defined
    • parameters_bmad.f90 --- Defines global parameters
  • Miscellaneous
    • rotate_ring.f90 ---
    • track1_custom.f90 ---
• files/ Back
  
  • bmad_all_configs_fringe_inf_grid. --- Lattice file that is parsed by the bmad_parser. The file defines the layout of the components of the injection line and ring, (quadrupoles, dipole, kicker) - lengths, strengths, location, also beam energy and initial twiss parameters. Also defined are the apertures for many of the elements. There are currently two branches. branch=0 corresponds to the injection line, from 30cm upstream, or to start of M5
  • calorimeter_lattice. Call, file=calorimeter_lattice. g2_tracking will write calorimeter hits to a file
  • fiber_harp_lattice. Call, file=fiber_harp_lattice. g2_tracking will write fiber harp hits to a file
  • walls_free.bmad Defines apertures in ring where there are no quads, collimators, kickers
  • walls_quads2-4.bmad Defines apertures as quad plates for quads 2-4
  • x_injection.lat M5 beamline This lattice file adds planes for the tracker chambers.
  • input.dat -- Initialization parameters: number of turns, number of muons, beam emittances, initial offsets (angles and displacements at the inflector exit with respect to the closed orbit.), inflector end coil scattering flag. Other examples with instructions are in /g-2/examples/example#.
  • README.txt --- Commentary
  • muons/ --- Muon distributions.
• Field maps/ Back
  
  • Cartesian Quadrupole maps [x - radial, y-vertical, z-longitudindal. Satisfies Maxwell equations in cartesian coordinates.]
    Quad_multipoles.bmad

    • Defines quad field in terms of multipole expansion assuming cartesian coordinates (no quad plate curvature). BMAD standard multipoles

    custom_quad_multipole.bmad

    • Defines quad field in terms of multipoles, no curvature, BMAD custom implementation

    quad1_long_combined.bmad

    • Quad 1 long field map. 2D with FEMME. No fringe. The file contains four distinct maps for the each of the four quad plates. Voltage on each plate can be different (for simulating scraping ramp). BMAD standard grid_field

    quad1_short_combined.bmad

    • Quad 1 long field map. 2D with FEMME. No fringe. The file contains four distinct maps for the each of the four quad plates. Voltage on each plate can be different (for simulating scraping ramp). BMAD standard grid_field

    quad2_long_combined.bmad

    • Quad 2 long field map. 2D with FEMME. No fringe. The file contains four distinct maps for the each of the four quad plates. Voltage on each plate can be different (for simulating scraping ramp). BMAD standard grid_field

    quad2_short_combined.bmad

    • Quad 2 short field map. 2D with FEMME. No fringe. The file contains four distinct maps for the each of the four quad plates. Voltage on each plate can be different (for simulating scraping ramp). BMAD standard grid_field

    quad3_long_combined.bmad

    • Quad 3 long field map. 2D with FEMME. No fringe. The file contains four distinct maps for the each of the four quad plates. Voltage on each plate can be different (for simulating scraping ramp). BMAD standard grid_field

    quad3_short_combined.bmad

    • Quad 3 short field map. 2D with FEMME. No fringe. The file contains four distinct maps for the each of the four quad plates. Voltage on each plate can be different (for simulating scraping ramp). BMAD standard grid_field

    quad4_long_combined.bmad

    • Quad 4 long field map. 2D with FEMME. No fringe. The file contains four distinct maps for the each of the four quad plates. Voltage on each plate can be different (for simulating scraping ramp). BMAD standard grid_field

    quad4_short_combined.bmad

    • Quad 4 short field map. 2D with FEMME. No fringe. The file contains four distinct maps for the each of the four quad plates. Voltage on each plate can be different (for simulating scraping ramp). BMAD standard grid_field

    quad_cartesian_grid.bmad

    • Compiles field maps for each of the eight quads defined above. BMAD standard

    quad_cartesian_multipole.bmad

    • Incorporates quads defined by cartesian multipole expansion. BMAD standard

    quad_long.bmad

    Same as quad_long_a.bmad BMAD standard grid_field

    quad_long_a.bmad

    Long quad field map. Based on 2D FEMME map. Includes all four plates BMAD standard grid_field

    quad_long_combined.bmad

    Quad long field map. 2D with FEMME. No fringe. The file contains four distinct maps for the each of the four quad plates. Voltage on each plate can be different (for simulating scraping ramp). BMAD standard grid_field

    quad_short.bmad

    Same as quad_short_a.bmad BMAD standard grid_field

    quad_short_a.bmad

    Short quad field map. Based on 2D FEMME map. Includes all four plates

    quad_short_combined.bmad

    Quad short field map. 2D with FEMME. No fringe. The file contains four distinct maps for the each of the four quad plates. Voltage on each plate can be different (for simulating scraping ramp). BMAD standard grid_field

  • Curvilinear maps - [Coordinates are r, y, s - cylindrical coordinates. r: radial, y: vertical, s: cylindrical. Satisfies Maxwell in cylindrical coordinates.]
    dipole.bmad

    • Main dipole - uniform

    quad_curvilinear.dat

    • Central azimuthal section of 3D map. BMAD grid_field element

    quad_curvilinear_grid.bmad

    • Combine curvilinear maps. BMAD standard

    quad_curvilinear_long.bmad

    • Central azimuthal section of Wanwei's 3D Opera calculation. Long quad. BMAD grid_field element

    quad_curvilinear_multipole.bmad

    • Multipole description of central 2D section of 3D map. BMAD multipole element

    quad_curvilinear_short.bmad

    • Central azimuthal section of Wanwei's 3D Opera map. Short quad. BMAD grid_field element

  • Dipole maps
    dipole.bmad

    Cartesian dipole (uniform vertical field) map. BMAD standard grid_field

    dipole_maxwell.bmad

    Cylindrical dipole field map. BMAD standard grid_field

  • Injection line maps - Internally to code referred to as branch 0
    fringe_and_inflector.bmad

    Fringe field map includes region through hole in iron and along the trajectory to the inflector exit. The inflector map (part of this same file) is just that. Inflector maps and fringe maps are superimposed so that particles see the total field. The inflector map can be oriented (tilted) independently and the inflector field can be scaled independently. BMAD standard grid_field

    inf_field_alone.bmad

    Inflector field map. (Combined with fringe in fringe_and_inflector.bmad.) BMAD standard grid_field

    inf_field_alone_custom.bmad

    Inflector field map. BMAD custom grid_field

    ring_inject_bfield3d_wuzheng_extended.bmad

    Fringe field through injection channel (Combined with inflector in fringe_and_inflector.bmad). BMAD standard gridfield

    ring_inject_bfield3d_wuzheng_extended_custom.bmad

    Fringe field through injection channel (Combined with inflector in fringe_and_inflector.bmad). BMAD custom gridfield

  • Kicker field maps
    KICKER_E821.dat --- Magnetic field map for e821 kicker geometry. Files are read with custom routine. BMAD custom

    KICKER_E989.dat --- Magnetic field map for e989 kicker geometry with rolled edges. Files are read with custom routine. BMAD custom

    KICKER_E989_NoRolledEdges.dat --- Magnetic field map for e989 kicker geometry with no rolled edges. Files are read with custom routine. BMAD custom

  • Kicker pulse shape - temporal maps
    Ideal pulse

    Generated analytically in fields.f90

    kicker1_pulse (pdf) and kicker1data.txt (txt)

    Magnetometer measurement of kicker field.

    half tail (pdf) and kicker1data_halftail.txt (txt)

    Magnetometer measurement of kicker field with amplitude of the tail reduced by 1/2

    5% tail (pdf) and kicker1data_05_tail.txt (txt)

    Magnetometer measurement of kicker field with amplitde of tail reduced to 5%.

• plotting_scripts/ Back
  gnuplot scripts
• documentation/
  
  List Back

Executables

• g2_tracking :

  Function: Generate and track a distribution of muons from the inflector, through the quad plates, kicker plates, passed pulsed kicker, around ring, muon spin tracking, muon decay and propagation of decay positrons

  Input Back

  • input.dat -- Namelist formatted file with parameters that determine muon distribution, kicker and quad parameters, scan definities, field maps, etc. i.e.
  • files/input.dat
  • Bmad formatted lattice filed that defines geometry of injection channel and layout of ring elements, i.e. i.e.
  • files/bmad_short_kickers.
  • Field and temporal maps
    • g-2/files/pulse_127cm.dat Kicker pulse shape
    • g-2/magneticfield/ring_inject_bfield3d_wuzheng_extended.dat Field map of main dipole through the injection channel
    • g-2/magneticfield/inf_field_alone.dat Field map of the inflector
    • g-2/files/muons/VDstop_DS_436_12000.dat Distribution of muons generated by proton target to ring
    • g-2/files/KICKER_E989_NoRolledEdges.dat Kicker field map

  Output Back

  All output files are written to subdirectory names date_time = i.e. 20160708_112120 July 8, 2016, 11:21:20
  • input_data.dat --- All of the parameter values in the input namelist
  • Beam_moments_tbt.dat, Beam_moments_by_element.dat --- Averages and standard deviations of each of the 6 phase space coordinates of the distrubution computed at the end of each turn (Beam_moments_tbt.dat), or each element (Beam_moments_by_element.dat) respectively. Element by element information is saved if if the flag save_element_by_element_info = T in the input file. Includes <x>,<y>,<px>,<py>,<t>,<p>, and <(x-<x>)^2>, etc. and the number of muons remaining.
    
  • Debug mode. If <nmuons=1> in the input.dat then the reference coordinates are propagated through the injection channel and around the ring and the phase space coordinates for that trajectory
    • at the end of are written to fort.19
    • and at the end of each element to fort.29
  • muons_vs_time.dat --- Number of muons per unit time interval vs turn.
    
  • NAME//'_phase_space.dat' --- Phase space coordinates of all muons in the distribution at the location NAME. The file(files) are generated by calls to subroutine write_phase_space if the flag write_phase_space_file = T in the input file. If the NAME refers to an element, the phase space is for the distribution on the first turn. If NAME = EndOfTracking, the phase space is for the distribution at the end of all tracking.
    
  • Time_Dep_Moments_at_END.dat Moments of the distribution as measured in a single detector located at the end of the ring in time bins. The width of the time bin is set in the input file by the parameter. <time_bin_width>. If <time_bin_width> = 1.e-9 corresponds to 1ns bins. <time_bin_width> <= zero, the file is not created. harp_plane_hits.dat If there are fiber harps in the lattice file (call fiber_monitor_lattice. ) then the phase space coordinates and the time that each muon hits a fiber is recorded in harp_plane_hits.dat. (If FiberScatter0 = T in input.dat then muons will scatter when they hit the fibers as appropriate).
  • VparamDependence.dat (used to be fort.32) --- Summary of averages, standard deviations, lost particles at the end of tracking.
    
  • lost_muons.dat --- Phase space coordinates of lost muons: muon #, s, vec(6), ele_name. For determining where muons are being lost
  • twiss_file.dat --- Twiss parameters of the ring. Initalized by g2twiss struct twiss values in input.dat file if "twiss at start" is commented out in tracking_master.
  • fort.51 --- Change in phase space coordinates due to scattering in upstream end of inflector
  • fort.52 --- Change in phase space coordinates due to scattering in downstream end of inflector
  • fort.53 --- Change in phase space coordinates due to scattering in wall_hit_handler
  • fort.71 --- Trajectory through injection channel in 10cm steps. Computed when nmuons=1.
  • fort.72 --- Twiss parameters through injection channel at 10cm steps. Computed along trajectory through injection channel when nmuons=1. (Not sure what initiaizes twiss)
  • gnu_input.dat --- Summary of data in input.dat that is read by plotting scripts

  Test Run Back

  After building an executable with the mk command in the < DIR > /g-2 directory, the program is almost ready to run.
  1. cd test/ --- The test/ subdirectory has almost everything you need for a test run
  2. From the test/ subdirectory create soft links to the field maps for the injection (fringe) line field, inflector field, and kicker fields as follows:

     ln -s ../../g-2/files/pulse_127cm.dat
     ln -s ../../g-2/magneticfield/ring_inject_bfield3d_wuzheng_extended.dat 
     ln -s ../../g-2/magneticfield/inf_field_alone.dat 
     ln -s ../../g-2/files/muons/VDstop_DS_436_12000.dat 
     ln -s ../../g-2/files/muons/particles_endm4m5_100.txt
     ln -s ../../g-2/files/KICKER_E989_NoRolledEdges.dat 
     ln -s ../../g-2/files/quads/
     ln -s ../../g-2/files/calorimeter_lattice.
     ln -s ../../g-2/files/fiber_monitor_lattice.
     ln -s ../../g-2/files/walls_free.bmad
     ln -s ../../g-2/files/walls_quads2-4.bmad
     ln -s ../../g-2/files/backleg/
     ln -s ../../g-2/files/bmad_all_configs_fringe_inf_grid.
     ln -s ../../g-2/files/bmad_grid_fringe_inf.bmad
     ln -s ../../g-2/magneticfield/BrFourier2016.dat
     ln -s ../../g-2/magneticfield/BzFourier20170628_LogID983.dat
     ln -s ../../g-2/files/g-2_FFT_04032015.lat
     ln -s ../../g-2/files/g-2_FODO_04032015.lat
     ln -s ../../g-2/files/parameters_g-2_03112015.lat							  
     

     The command /g-2/softlink (or softlink_lnx, or softlink_gm2) depending on what machines you are running will create all the links
  3. You will find an example input.dat and the lattice file bmad_all_configs_fringe_inf_grid_calo. already in the test/ subdirectory.
  4. To execute - On the command line type < DIR >/production/bin/g2_tracking < CR >

  ExamplesBack

  There are many input parameters specified in the input.dat file. Example input files can be found in the examples subdirectory g-2/examples/ along with explanatory documentation in each of the 4 example subdirectories. examples/README.txt gives a summary of what you will find in each of the 5 directories
  • example1/README.txt
  • example2/README.txt
  • example3/README.txt
  • example4/README.txt
  • example5/README.txt
  • example6/README.txt
  • example7/README.txt
  • example8/README.txt
  • example9/README.txt

  • Moments Input files for calculating moments of the muon distribution and complete set of output files and plots

  Things you can calculateBack

  Injection channel

  The injection channel branch <start_tracking_at_inflector_exit> = F begins just upstream of the hole in the backleg iron and extends through the fringe field of the main dipole, and through the inflector. The magnetic field is represented as maps computed with the OPERA code. There are separate maps for main dipole fringe field and inflector field. The reference trajectory for this branch is the line tangent to the main ring at a circumference of R + d, where R is the radius of the closed orbit of the magic momentum muon and d =77mm is the displacement of the axis of the inflector from the closed orbit. The initial coordinates (that is at the start of the branch) of the trajectory magic momentum muons that exits the inflector on its axis depends on the fringe field map (presumably fixed) and the inflector map, which can be scaled, <inflector_field>.

  • The <initial offsets> of the ideal trajectory can be determined automatically by setting <opt_incident> = T and <nmuons> = 1.
  • <bmad> computes a 6X6 transfer matrix for each of the elements in the injection branch, based on tracking. These matrices are essential for propagating twiss parameters through the branch

  • Muon distribution
    For historical reasons, the twiss parameters that defined the muon distribution are specified <twiss> at the inflector exit <twiss_ref>='end' or halfway through the inflector. The branch transfer matrices are then used to propagate the twiss parameters back to the start of the branch at the hole in the iron. <wiss_ref>=center. Call the set of twiss parameters at the input to the injection branch twiss_in

    The phase space distribution of muons is generated according to specified parameters, or read from a file. The distribution is adjusted to match the twiss parameters computed in the previous step according to the following procedure:

    • Compute the twiss parameters for the muon distribution from the moments (i.e. <xx>,<xp>, . . .). Call them twiss_0
    • Construct a matrix that is a function of twiss_0 and twiss_in to propagate from one set to the other. There is an undetermined (and irrelevant) phase.
    • Use the matrix to propate each muon in the distribution with twiss_0 to twiss_in
    • The new distribution when transported through the injection branch, will exit the inflector with the twiss parameters specified by <twiss>.

  • <inj_matrix_tracking> ==T/F if true the muons are propagated through the injection branch using the 6X6 matrices. If false, by runge_kutta integration through the maps.

  • Twiss parameters through the injection channel are written to injection_line_twiss.dat if <nmuons> = 1.
  • Trajectory through the injection channel is written to injection_line_trajetory.dat if <nmuons> = 1.

  Ring

  • Twiss parameters
  • Muon distribution
  • Kickers
  • Quadrupoles
  • Muon decay
  • Spin tracking
  • Decay positrons

• ering:

  Function: The ering executable tracks muons around a ring with radius of 7.112 m. There is a uniform vertical magnetic field and uniform radial electric field. Muon phase space and muon spin are tracked by runge kutta integration

  Input Back

  • ering_input.dat -- Namelist formatted file in which electric and magnetic fields are specified, offset of initial phase space coordinates and number of turns to track i.e.
  • files/ering_input.dat
  • Bmad formatted lattice filed that defines ring geometry and muon reference energy and trajectory i.e.
  • files/bmad_ering.

  Output Back

  • phase_space_spin.dat -- Phase space coordinates and polarization vs element name, turn, and time
  • floor_plan.dat -- Ring geometry

  Example - test run Back

  • There is an example ering_input.dat file and a bmad lattice file bmad_ering. in directory g-2/ering_example
  • Type <../production/bin/ering bmad_ering.> to run the program in this directory