About spin ?

[Kristian Nielsen]

Hi Emmanuel,

Thanks a lot for the Latex manual entries. I will look closer at them
and include them the next time I revise the manual.

I just finished a new version of mcgui which integrates the mcdoc stuff
so that components can be used in a "user-friendly" graphics dialog
(also works for the users own components in the current
directory). While I am not completely satisfied with it yet, I think it
is promising and will be quite useful. I have put an "alpha" release up
for you on the web page at

    http://neutron.risoe.dk/mcstas/support/farhi/mcstas-1.23A.tar.gz

in case you want to try it out and have some comments. It also has the
new string instrument parameters and optional component parameters, but
be careful about using them since your code will then not work in McStas
1.2! To see the new mcgui stuff you need to open the integrated editor
window and use the new "Insert" menu.

About the neutron spin: When I visited ILL last year, I had some
discussions with Trefor, and we agreed that the polarisation needed to
have three components (though I can no longer remember why). However,
that is not the reason for having a separate "POLARISATION PARAMETERS"
statement instead of using the STATE PARAMETERS. Rather, the reason is
to provide a way for components to advertise that they know how to
propagate the neutron spin through the guide field properly. Just
mentioning the spin in the STATE PARAMETERS without doing anything about
them does not properly handle polarisation in all cases! Therefore the
warning is telling the user that the component completely ignores
polarisation, which was probably not intended. If it is useful, we can
allow two-component polarisation, but that will also use the
POLARISATION PARAMETER syntax, not STATE PARAMETER. The s1 and s2 STATE
PARAMETERS will soon be removed (but still ignored if present for
backward compatibility).

I am now planning to release the next version of McStas at the SCANS
meeting at the ILL on May 18.

 - Kristian.

--
Kristian Nielsen        kristian.nielsen at risoe.dk
Risø National Laboratory
Condensed Matter Physics and Chemistry Department
Tel. +45 4677 5515   Fax +45 4677 4790
Encryption PGP key http://neutron.risoe.dk/kn.txt