The input data card file

A simple problem like the one chosen for this example can be managed by means of a simple data card file like the following one, that we shall name as seamu.inp. It can be noticed that the NEW-DEFA set of defaults has been chosen, the main reason being a reasonably low value of energy thresholds. However other features are implies, as here summarized:

• EMF on, with electron and photon transport thresholds equal to those defined in the PEMF file

• Inelastic form factor corrections to Compton scattering activated (no need for EMFRAY)

• Low energy neutron transport on (no need for LOW-NEUT). The neutron high energy threshold is set at 19.6 MeV.

• Non analogue absorption for low energy neutrons with probability 0.95 for the last (thermal) group

• Particle transport threshold set at 10 MeV, except for neutrons (19.6 MeV), antineutrons (50 MeV), and (anti)neutrinos (0, but they are discarded by default anyway)

• Multiple scattering threshold for secondary charged particles lowered to 20 MeV (equal to that of the primary ones)

• Delta ray production on with threshold 1 MeV (see option DELTARAY)

• Restricted Landau fluctuations on both for hadrons/muons and EM particles (see option LANDAU)

• Heavy particle e+/e- pair production activated with full explicit production (0 threshold -> 2 m_electron)

• Heavy particle bremsstrahlung activated with explicit photon production above 1 MeV

• Muon photonuclear interactions activated with explicit generation of secondaries

We do not need all these feature, and some of them must be over-written. The critical parts of this file will be examined in detail in the next sections.

Here is the full listing of seamu.inp:

TITLE
	 Test of Muon Propagation in sea water
*
*	Sets the standards defaults of FLUKA (see user manual)
*
DEFAULTS                                                              NEW-DEFA
*
*	Here sets muon energy. (1 TeV in this example)
*
BEAM       1000.                                                      MUON+
*
*	Here sets initial coordinates of muons. They are assumed to go
* 	along the +Z axis. Muons are injected just before the water layer
*       in a vacuum layer (see description of geometry below)
*
BEAMPOS    0.0       0.0       -50.0
*
*	Switching off Electromagnetic Showering
*
EMF                                                                   EMF-OFF
*
*	Do not transport electrons, positrons, photons, all charged and 
*       neutral hadrons, neutrinos
*
DISCARD   3.        4.        7.        218.      223.
DISCARD   5.        6.        27.       28.  
*
*	Starts description of geoemtry: a large box of water delimited
*       by vacuum layers at the top and bottom. Here depth is fixed
*       at 1 km. Muons are injected in the initial vacuum.
*
GEOBEGIN             0.01                                             COMBINAT
                         water layer
  SPH    1       0.0       0.0       0.0+5000000.0
  RPP    2-1000000.0+1000000.0-1000000.0+1000000.0    -100.0+1001000.0
  XYP    3       0.0
  XYP    4  100000.0
  END
* black hole
    1    5      1     -2
* vacuum at the beginning
    2    5      2      3    
* water layer
    3    5      2      4     -3
* vacuum at the end
    4    5      2     -4
  END
GEOEND
*
*	Here defines materials and Compounds of sea water (Antares 1)
*
* 1) Hydrogen
MATERIAL  1.0       1.0079    .0000899  3.0                   1.0     HYDROGEN
* 2) Oxygen
MATERIAL  8.0       15.999    0.001429  8.0                           OXYGEN
* 3) Magnesium
MATERIAL  12.0      24.305    1.738     9.0                           MAGNESIU
* 4) Potassium
MATERIAL  19.0      39.102    0.031165  11.0                          POTASSIU
* 5) Calcium
MATERIAL  20.0      40.08     1.54      12.0                          CALCIUM
* 6) Sodium
MATERIAL  11.0      22.990    0.038349  13.0                          SODIUM
* 7) Chlorine
MATERIAL  17.0      35.4529   0.0029947 14.0                          CHLORINE
* 8) Sulphur
MATERIAL  16.       32.066    2.070     15.0                          SULFUR
* 9) Sea water compound (Antares 1) using atom relative contents
MATERIAL                      1.0341    18.0                          SEAWATER
COMPOUND   2.00000    3.0      1.008800  8.0       0.00943    13.0    SEAWATER
COMPOUND   0.000209  11.0      0.001087  9.0       0.000209   12.0    SEAWATER
COMPOUND   0.01106   14.0      0.005820  15.0                         SEAWATER
*
* Here assigns materials to regions
* Sea Water in region 3 
ASSIGNMAT 18.0      3.0       
*  External Black Hole in region 1
ASSIGNMAT 1.0       1.0
*  Vacuum at beginning (region2)
ASSIGNMAT 2.0       2.0
*  Vacuum at end (region 4)
ASSIGNMAT 2.0       4.0       
*
*	Setting SCORE and Ouptut levels.
* 
SCORE     208.0     211.0     
OUTLEVEL  1.0       7.0            
*
*       Activates the routine  MGDRAW (what(1) = or > 100.)  
*       if what(3)=2 the entry BXDRAW in MGDRAW routine is activated
*
*
USERDUMP     101.               2.0                                   SEAMU
*
*	Activates Random Number initialization
*
RANDOMIZE  1.
*
*	Activates user dependent initialization
*
USRICALL
*
*	Starts Job asking for a given number of events
*
START     5000.     99999999.           0.0        0.0
*
*	Activates user dependent output
*
USROCALL
STOP

We draw the attention on the activation of a USERSUMP card with what(3)=2. As remarked in the comments, this is mandatory to enable the call to the ENTRY BXDRAW in the MGDRAW routine, where we introduce our specific code lines. Warning: at present the FLUKA manual is not clear enough how to activate the BXDRAW entry and the present instructions are meant to clarify this issue.