[mcstas-users] Rotating polarising mirror components

[Robert Dalgliesh - UKRI STFC]

Peter, Erik,
I apologise, I've just noticed the note in the component description regarding the hard coding of the polarisation direction.
I will modify my simulations accordingly.

Sorry everyone

Rob

From: mcstas-users <mcstas-users-bounces at mcstas.org> On Behalf Of Robert Dalgliesh - UKRI STFC
Sent: 29 May 2020 15:25
To: McStas <mcstas-users at mcstas.org>
Subject: [mcstas-users] Rotating polarising mirror components

Hi Peter, Erik,
I've been looking in more detail at what happens when I rotate a polarising mirror or v-mirror in mcstas as a result of getting repeated assert errors from the polarisation being greater than 1.
I am having trouble working out if the polarisation vector is rotated correctly if e.g. Pol_mirror is rotated by 90deg to be in a horizontal rather than vertical geometry. The code performs a calculation of probabilities based on the sy component (GetMonoPolRefProb(FN, FM, sy, &refWeight)) but if I have a polarisation in the x-z plane prior to the component I have been unable to determine what is happening.
In order to makes things correct the incoming spin vector would need to be rotated by 90 degrees on entering the pol_mirror component. Is this done in some hidden way or do I need to rewrite the components to deal with this?

Thanks

Rob

===================================
Dr. Robert Dalgliesh
ISIS Neutron and Muon Source
STFC Rutherford Appleton Laboratory
R3 1.29
Harwell Oxford
Didcot
OX11 0QX
Office Tel: +44 (0) 1235 445687
Internal Mobile Extension: 1176


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