Neutron Scattering

G.k=zGz . (11)
This case is fulfilled if- as shown in Fig . 5) - the projection of the wave vectors onto
Cz is just equal to 1 / 2 - G .
Fig 5)
illustration for the
selecticn of scattered
wave vectors and
1/2G = k . sinO
their divergence as
determined by the
k ` k` modulus G and the
- - 2- - scattering angle .
- - - - - - - k-AG/G °G/ G is of the order
of 10-4 and is thus
negligible for tripleaxis
spectrcmeters .
k . cot 0
The variance of a selected k -vector is given by the derivative of Yz G= k sin0 , or
4k - 4Z - 1 4E - OG + cot0 - 40 .
k Z 2 E G
With increasing wavelength ofthe neutron the energy resolution will be improved.
2 .0
n É
m
w 1 :0
m
x
C
O
(12)
c 0 .5
Fig . 6) schematicrepresentation of the variance 4~.
as a fonction of scattering angle and material
9- 7
1 2 3 A 5 6 7 8
neutron wave vector k ,(A 1 )
Fig . 7) monochromatic flux at the
IN8 (ILL) for various materials as
afonction of k [3]