An Introduction to Neutron Scattering - Spallation Neutron Source

Only Those Thermal or Cold Neutrons With Very Low
Velocities Perpendicular to a Surface Are Reflected
α
α’
nickel
for
)
(
1
.
0
)
(
:
Note
quartz
for
)
(
02
.
0
)
(
sin
)
/
2
(
A
10
05
.
2
quartz
For
4
is
reflection
external
for total
of
value
critical
The
4
or
4
sin
'
sin
i.e.
4
)
sin
(cos
)
'
sin
'
(cos
4
Since
Law
s
Snell'
obey
Neutrons
'
/cos
cos
n
i.e
'
cos
'
cos
cos
:
so
surface
the
to
parallel
locity
neutron ve
the
change
cannot
surface
The
/
critical
critical
critical
1
-
3
0
0
2
0
2
2
2
0
2
2
2
2
2
0
2
2
2
2
0
2
0
0
0
0
0
A
A
k
x
k
k
k
k
k
k
k
k
k
k
k
n
k
k
k
n
k
k
o
o
critical
critical
z
z
z
z
zl
zl
λ
α
λ
α
α
λ
π
πρ
πρ
πρ
α
α
πρ
α
α
α
α
πρ
α
α
α
α
α
≈
≈
⇒
=
=
=
−
=
−
=
−
+
=
+
−
=
=
=
=
=
−