An Introduction to Neutron Scattering - Spallation Neutron Source

Neutron counts ( per 50 sec)
Neutron Polarization is Measured using an
Asymmetric Scan around the Echo Point
2000
1500
1000
500
0
0 1 2 3 4 5 6 7
Bd Current in coil 3
2 (Arbitrary Units)
Echo Point
The echo amplitude decreases
when (Bd) 1 differs from (Bd) 2
because the incident neutron
beam is not monochromatic.
For elastic scattering:
⎡γm
⎤
P ~ ∫ I(
λ) cos⎢
1 2 . d
h
⎥
⎣
⎦
{ ( Bd)
− ( Bd)
} λ λ
Because the echo point is the same for all neutron wavelengths,
we can use a broad wavelength band and enhance the signal intensity