rounding errors?

[Dr. Georg Artus]

Hello,

> You set the Q value for the monochromator to 8.88577. At 45 degrees I
> calculate this to correspond to 81.8 meV, and both plots are nicely
> centered around this value. Did you calculate another energy for this Q?
> Then perhaps either the constants for unit conversion in McStas are
> wrong, or you made an error?

Your plots in fact look much better than mine. Conversion between k, Q,
v, E and lambda seems to be the problem.
Which formula do you use for calculating Q? For Q=8.88577 I calculate an
energy of 81.0425meV at 45°? I calculate it with
Q=4*PI*sin(theta)/lambda 
with E(meV)=81.80425/lamda(AA)**2. 
Do I have the wrong formula? 81.80425 is correct.

Georg
-- 
*********************************************

Dr. Georg Artus
Technische Universitaet Muenchen
Neue Forschungsneutronenquelle Garching
D-85747 Garching

Tel: +49 (0)89/289-14675
Fax: +49 (0)89/289-14666 or 12112
E-mail: gartus at ph.tum.de