----------------------------------------- The FLUKA geometry, described in Chap. 8}, and all particle space coordinates (position x, y, z, and corresponding direction cosines) are based on a right-handed Cartesian reference frame. The origin of the frame (0, 0, 0) and the direction of the three perpendicular axes can be chosen arbitrarily by the user, but by default a particle beam and its space characteristics (angular divergence, transversal profile, polarisation) are referred to a beam direction coincident with the z-axis of the geometry frame of reference. A different beam direction can be specified by means of command BEAMAXES: see a description of the command and especially the corresponding Notes. Also some scoring structures (binnings, see command USRBIN) are defined as meshes parallel to the reference axes, and in the case of cylindrical binnings the basic axis is again the z-axis. In a similar way, some geometrical bodies (planes, parallelepipeds, infinite cylinders) are described by their orientation with respect to the axes. But rototranslation transformations, defined by commands ROT-DEFIni and ROTPRBIN, allow the user to input binnings and geometrical bodies with arbitrary orientation with respect to axes.
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