BEAMAXES

    defines the axes used for a beam reference frame different from the geometry
    frame

    See also BEAM, BEAMPOSit, POLARIZAti, SOURCE, SPECSOUR

     
WHAT(1)
 = cosine of the angle between the x-axis of the beam reference
               frame and the x-axis of the geometry frame
               
Default
: no default

     
WHAT(2)
 = cosine of the angle between the x-axis of the beam reference
               frame and the y-axis of the geometry frame
               
Default
: no default

     
WHAT(3)
 = cosine of the angle between the x-axis of the beam reference
               frame and the z-axis of the geometry frame
               
Default
: no default

     
WHAT(4)
 = cosine of the angle between the z-axis of the beam reference
               frame and the x-axis of the geometry frame
               
Default
: no default

     
WHAT(5)
 = cosine of the angle between the z-axis of the beam reference
               frame and the y-axis of the geometry frame
               
Default
: no default

     
WHAT(6)
 = cosine of the angle between the z-axis of the beam reference
               frame and the z-axis of the geometry frame
               
Default
: no default

     
SDUM
    : not used

     
Default
 (option BEAMAXES not requested): the beam frame coincides with the
             geometry frame

     
Notes:
         1) Option BEAM describes a simple pencil beam, or also a beam simply
            distributed in space (angular divergence and transversal profile),
            provided the beam axis coincides with the z-axis of the input
            geometry. Also a possible beam polarisation described by option
            POLARIZAti refers to a beam with its axis coinciding with the
            geometry z-axis.
            The purpose of option BEAMAXES is to allow the user to define
            direction, angular divergence, transversal profile and polarisation
            for a beam of arbitrary orientation, as defined by options
            BEAMPOSit and BEAMAXES together. For this purpose, the user can
            define direction, divergence, profile and polarisation in a beam
            reference frame. Option BEAMAXES establishes the correspondence
            between beam and geometry reference frame.

         2) The origin of the beam reference frame coincides always with that of
            the geometry frame.

         3) The user needs to input only the direction cosines of the x- and of
            the z-axis of the beam frame. The direction of the y-axis is
            determined by the program as the vector product z X x.

         4) If the x- and z-axes defined with BEAMAXES are not exactly
            perpendicular (in double precision!) the program forces
            perpendicularity by adjusting the cosines of the x-axis.

         5) The direction cosines of the x- and z-axes do not need to be exactly
            normalised to 1. The code takes care of properly normalising all
            cosines.

    
Example:
 *  The next option cards describe a 10 GeV proton beam with a divergence of
 *  50 mrad and a gaussian profile in the "beam x"-direction and in the
 *  "beam y"-direction described by standard deviations sigma_x = 1. cm
 *  (FWHM = 2.36 cm) and sigma_y = 0.5 cm (FWHM = 1.18 cm). The beam starts
 *  from point (0,0,0) and is directed along the "beam y" axis. The "beam x"
 *  and "geometry x" axis coincides, while the "beam z" axis is at 45 degrees
 *  with both the "geometry y" and "geometry z" axes. The resulting beam
 *  direction in the geometry frame is at 45 degrees with respect to the
 *  "geometry y" axis and at -45 degrees with respect to the "geometry z"
 *  one. The "beam x" axis has cosines 1,0,0 and the "beam z" axis has
 *  cosines 0, cos(pi/4), cos(pi/4)
 *...+....1....+....2....+....3....+....4....+....5....+....6....+....7....+...
 BEAM           -10.0       0.0      50.0     -2.36     -1.18      1.0 PROTON
 BEAMPOS          0.0       0.0       0.0       0.0       1.0       0.0
 BEAMAXES         1.0       0.0       0.0       0.0 0.7071068 0.7071068

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