Neutron Scattering

For any practical application the imite lifetime of the neutron has no consequence . At neutron
velocities in the order of 1000m/s and distances in experiments up te,
are negligible .
100m lifetime effects
The neutron cames a spin of 1/2 which is accompanied by a magnetic dipole moment
Ii" = -1 .913 p,, (2 .2)
where uN is the nuclear magneton . The kinetic energy of the neutron E n = z ni, - un
may be
given in différent units as follows
1 meV = 1 .602 - 10 -22 J =:> 8.066 cm- '
since E = hv 1 meV=> 0.2418 . 10 12 Hz
since E = kBT : 1 meV=> 11 .60 K
The neutron wavelengths is obtained from the de Broglie relation
_ h h
m n Un =/( 21n E" )1i2
(2 .3)
According to the conditions for moderation, neutrons in different wavelength regimes are
separated into different categories as displayed in Fig .2 .3 . They are produced by moderation
in particular moderators which are kept at different temperatures .
hot thermal cold very cold ultra cold
AM
102
v v v
10 -2 10-4 10 -6
E [eV]
Figure 2 .3 : Relation between neutron wavelength and their corresponding kinetic energies .
2-4