How to set the beamaxes card to rotate the beam direction consistented with geometry?

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Dear FLUKA and Flair experts,
I try to define a rectangular plane beam that starts from point (0,0,0) ，and is directed in a direction perpendicular to the “geometry z” axis, at 30 degrees with respect to “geometry x” and “geometry y”. But the scoring of ursbin is different from that expected. In order to figure out this problem, I have done the following work:

  1. disenable beamaxes card

  2. enable beamaxes card

  3. test the excerise in FLUKA manual beamaxes
    Unfortunately， I still don’t understand how to set the beamaxes card to rotate the beam direction consistent with the geometry. Could you please help me to figure out this puzzling problem?beam_shape_test_with_beamaxes.inp (2.3 KB) beam_shape_test_with_FLUKAmanual_beamaxes.inp (2.3 KB) beam_shape_test_without_beamaxes.inp (2.2 KB) beam_shape_test_xyplane.flair (5.2 KB) .

Thanks！

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Dear @liuqy,

It seems to me, based on your Flair project, that your issue is the interaction between the direction set on the BEAMPOS card and the BEAMAXES card.

If you set your BEAMAXES card as the new Z axis is pointing in the desired beam direction (usually this is the case if you want to use the beam shape options on the BEAM card), then you have to leave the direction values on the BEAMPOS card empty (or set them to 0.0) to prevent rotating the beam twice.

For reference see slides 17-20 of this lecture:

One more tip: You can use #define directives and Flair expressions to set up a rotation by defining an angle diectly. This way you don’t have to worry about the precision of the direction cosines. See the modified input: beam_shape_test_xyplane_dh.flair (3.8 KB)

Cheers,
David

1 Like
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Thank you very much for helping me solve this problem！Could you please check the example of beamaxes in the manual, it seems to be somewhat misleading to rookie.