4D ellipsoid

[Kristian Nielsen]

> Date: Thu, 16 Sep 1999 13:24:58 +0200
> From: Farhi <farhi at ill.fr>

> I mean production of data. In fact it is just an inquiery of the (k,w)
> distribution around target (k,w), and possibly, a simple modelisation of
> this as a gaussian distribution (width and main ellipsoid axes))

Well, what we do to produce the 4-D resolution ellipsoid is to define an
inelastic scattering sample where S(Q,w) is a constant for all Q and
omega within a predefined 4-D volume. The detector then records the
initial and final k vector for every neutron that reach the detector,
together with the neutron weight p for that event. The expected value of
p (in the statistical sense) is then just the value of the resolution
function at the (Q,w) computed from the ki and kf. You can then either
do a 4D histogram of (qx,qy,qz,w), or (as we do) just store all the
events in a file for later processing and visualization.

> <br>Visualisation can be done through matlab, or whatever (PGPLOT ?)

Yes (we use both Matlab and PDL).

 - Kristian.