An Introduction to Neutron Scattering - Spallation Neutron Source

A Comparison of Neutron Flux Calculations for the ESS SPSS (50 Hz, 5 MW)
& LPSS (16 Hz, 5W) With Measured Neutron Fluxes at the ILL
Instantaneous flux [n/cm 2 /s/str/Å]
Flux [n/cm 2 /s/str/Å]
10 17
10 16
10 15
10 14
10 13
10 12
10 11
10 10
2.0x10 14
1.5x10 14
1.0x10 14
5.0x10 13
ILL hot source
ILL thermal source
ILL cold source
0 1 2 3 4
Wavelength [Å]
0.0
0 500 1000 1500 2000 2500 3000
Time [μs]
l = 4 Å
poisoned moderator
decoupled moderator
coupled moderator
long pulse
peak flux
poisoned m.
decoupled m.
coupled m.
long pulse
Flux [n/cm 2 /s/str/Å]
10 17
10 16
10 15
10 14
10 13
10 12
10 11
10 10
ILL hot source
ILL thermal source
ILL cold source
average flux
poisoned m.
decoupled m.
coupled m.
and long pulse
0 1 2 3 4
Wavelength [Å]
Pulsed sources only make sense if
one can make effective use of the
flux in each pulse, rather than the
average neutron flux