[Bornagain-announcements] bug warning: incorrect intensities of source or detector is below horizon (z<0, alpha<0)

[Joachim Wuttke]

Dear BornAgain users,

please be warned the BornAgain generates wrong intensities
if either the source or the detector is below the horizon
(z<0, alpha<0). The erroneous intensity diverges with the
depth of buried particles. More dangerous is the case of
shallow particles as simulations may look unsuspicious.

Many thanks to Karolina Mothander of Lund University for
pointing us to this issue.

Per today, the bug is corrected in our 'develop' branch.

Unfortunately though, unrelated other changes in this branch
prevent us from releasing a new BornAgain version any soon.

For the time being, we can only advise you to make sure that
always alpha_i>0 and alpha_f>0.

If you urgently need to simulate transmission GISAS, or worse,
if you already published BornAgain simulations for that case,
then please contact us.

There is no issue with BornAgain for SAS; the bug only
concerns multi-layer samples under grazing incidence.

Sorry for these bad news, Joachim

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