McStas

[Kristian Nielsen]

Dear John,

> Date: Mon, 23 Aug 1999 13:09:46 -0400
> From: John Copley <john.copley at nist.gov>

> I'm not sure whether your colleagues got a copy of your message.  The CC
> line read as follows:
>         CC: kim.lefmann at risoe.dk.kurt.clausen@risoe.dk
> (note the . between dk and kurt)

> Let me tell you a little bit about MSCAT.

Thanks a lot for the information on MSCAT. I would be grateful for a
copy of the paper you mentioned, which does not seem to be available
from our library (though they could probably obtain it from somewhere
else for me it that is more convenient). We are slowly starting to look
in more detail on simulating scattering kernels, and we should clearly
try to build as much as possible on previous work.

As regards different techniques for sampling, this is also something
that we have given much thought, though more so for general instrument
simulation and less for what happens inside samples. It sounds like your
ideas are quite similar to ours. Usually, we try to sample in a way that
is reasonably easy to implement and which ensures good (if not perfect)
variance of the results. The weight assigned to the individual event is
then adjusted to make the result match the physical model. I think this
is what you meant when you described your selection of outgoing wave
vector?

We have even experimented with making the sampling strategy variable,
adapting itself to the individual simulation, with surprisingly good
results. On the other hand the problem of sampling based on an arbitrary
user-supplied S(Q,omega) sounds quite hard, and I am sure that we could
benefit from some discussion on this. So yes, I would be very interested
in more information on this.

> With regard to simulating the optical filter at my instrument, I propose
> to send you a fax containing a description of the geometry of the guide,
> plus a measured reflectivity curve. What is your fax number?

That sounds fine. My fax number is +45 4677 4790 (the +45 is the code
for Denmark, as you probably know). I will be happy to look at it and
work something out, it shouldn't be very difficult.

 - 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