<* $Id: xnd_faq.html,v 1.1.1.1 2001/02/05 11:30:00 berar Exp $ *>
<em>xnd</em> F A Q.
xnd_faq F A Q.
To be filled
It is easy to have an idea of the intensity received by the sample when
we known the scale factor. Following Suorti (Acta Cryst 85, A41 p413)
and knowning expression used in xnd, the number of photons received by the sample
for measuring each data point is :
No = 32 Scale Pi^2 Mu Vc^2 / (180 Eff RSlits VDiv Re^2 Lamda^3)
in which (using Al(OH)3 measured on a laboratory difractometer as an exemple ) :
| Re | 2.82 e-15 m | electron radius
|
| Vc | 425 e-30 m^3 | cell volume
|
| Lambda | 1.54 e-10 m | wave length
|
| RSlits | 5 e-4 rad | receiving slits
|
| VDiv | 4 e-2 rad | vertical (axial) divergency
|
| Eff | ~1 | counter efficiency, air absorption
|
| Mu | 5.7 e3 m^-1 | sample absorption length
|
| Scale | 1 e-6 | xnd scale factor
|
| No | 3.10 e6 | Number of incoming photons on the sample
|
Assuming that we can neglect correction associated micro-absorption. We can
calculate the amount of each phase in a mixture. In the above formula, there
is only two coefficients which depend on the phase : the cell volume and the
scale factor. Then in volume the amount of each phase in the sample is proportional
to Scale Vc^2.
JFB March 5th, 2001