exoticphysics/ucn/README.md

0001 \page Exampleucn Example ucn
0002
0003 \author Peter Gumplinger - TRIUMF, Vancouver, Canada \n
0004  gum@triumf.ca
0005
0006 This example demonstrates how ultra-cold neutrons (UCN) propagate
0007 in a guide pipe and how this can be simulated in Geant4.
0008
0009 ## INTRODUCTION
0010
0011 This example exhibits the functionality of UCN physics
0012
0013
0014 ## GEOMETRY
0015
0016   The geometry consists of a single hollow pipe (cylinder)
0017   placed in a world.
0018
0019   Default World Size: G4Box - 1m x 1m x 100m
0020
0021   The pipe wall is made of G4_Ni while the world and, hence,
0022   the inside of the pipe is made from G4_Galactic
0023
0024   The G4UCNMaterialPropertiesTable properties are:
0025 ```
0026   "REFLECTIVITY" = 1
0027   "DIFFUSION" = 0.1
0028   "FERMIPOT" = 252.0 neV
0029   "SPINFLIP"= 0.
0030   "LOSS" = 12.5e-5
0031   "LOSSCS" = 0.
0032   "ABSCS"= 4.49    // 1/v loss cross-section  at room temp.
0033   "SCATCS" = 18.5  // (incoherent) "elastic" scattering cross-section
0034 ```
0035
0036   The MicroRoughnessParameters are:
0037 ```
0038   Roughness correlation length w = 30nm
0039   Surface roughness b = 1nm
0040   # of angles theta_i in the look-up tables: 180
0041   # of energie bins in the look-up tables: 1000
0042   min. and max. values of theta_i: 0*degree and 90*degree
0043   min. and max values of Energy: 1neV and 1000neV
0044   # of angles theta_o in the look-up table calculation: 15
0045   # of angels phi_o   in the look-up table calculation: 15
0046   angular cut: 0.01*degree
0047 ```
0048
0049   The default step limits in the vacuum is 1mm and maxTime is 100s
0050
0051   The simulation is in a G4UniformGravityField
0052
0053 ## PHYSICS LIST
0054
0055   The ExUCNPhysicsList defines only
0056   - G4Neutron, G4Proton, G4Electron, G4AntiNeutrinoE, G4MuonPlus, G4MuonMinus and
0057     G4GenericIon
0058
0059   Through ExUCNExtraPhysics the following processes are instantiated:
0060   -  G4StepLimiter
0061   -  G4UserSpecialCuts
0062
0063   and in ConstructUCN()
0064   -  G4UCNLoss
0065   -  G4UCNAbsorption
0066   -  G4UCNMultiScattering
0067
0068 ## THE PRIMARY GENERATOR
0069
0070   The primary kinematic consists of a single ultra-colde neutron
0071   (uniform between 1neV and 100neV from the origin uniform into 4pi
0072
0073   A RUN is a set of events.
0074
0075
0076 ## VISUALIZATION
0077
0078   The Visualization Manager is set in the main() for interactive session.
0079   The initialisation of the drawing is done via the command
0080
0081 ```
0082 /control/execute vis.mac
0083 ```
0084
0085 ## TESTING
0086
0087    This example handles the program arguments in a new way.
0088    It can be run with the following optional arguments:
0089
0090 ```
0091 % ./ExUCN [-m macro ] [-u UIsession] [-t nThreads]
0092 ```
0093
0094   The -t option is available only in multi-threading mode
0095   and it allows the user to override the Geant4 default number of
0096   threads. The number of threads can be also set via G4FORCENUMBEROFTHREADS
0097   environment variable which has the top priority.
0098
0099   Execute ExUCN in 'batch' mode from macro files e.g.
0100
0101 ```
0102 % ./ExUCN -m ExUCN.in > ExUCN.out &
0103 ```
0104
0105   Execute ExUCN in 'interactive' mode with visualization e.g.
0106
0107 ```
0108 % ./ExUCN
0109 Idle> type your commands, for example:
0110 Idle> run/beamOn 1
0111 ...
0112 ```