defines the axes used for a beam reference frame different from the
geometry frame
See also BEAM, BEAMPOS, POLARIZAti, SOURCE
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
angular divergence, transversal profile and polarisation for a beam
of arbitrary direction, either constant as defined by option
BEAMPOS, or not necessarily known in advance as provided by a user
SOURCE routine. For this purpose, the user can define 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 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 in a direction perpendicular to the
* "geometry x" axis, at 45 degrees with respect to both "geometry y" and
* "geometry z". 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 0.7071068 0.0
BEAMAXES 1.0 0.0 0.0 0.0 0.7071068 0.7071068
