Neutron guides allow the transmission of neutrons from the reactor away to the monochromators, or velocity selectors on the instruments. They use the principle of total reflection on glass or metallic surfaces, with nickel or multilayer supermirror coatings. The glancing angle depends on the coating and the wavelength of the neutrons. It is 0.1 times for natural nickel surfaces, e.g. 1 degree for 10 Å neutrons from a cold source. With supermirror coatings this angle becomes greater by a factor m=2 or m=3. Neutrons propagate by multiple reflection over lengths greater than 50 m.

The ILL guides are curved with radii between 10 and 27000 m. This allows instruments to be installed outside of the direct view of the radiation from the reactor core, giving a better signal to noise ratio. Also it cuts down the transmitted spectrum, in function of the guide geometry at the lower end of wavelengths.

Cold neutron guide H53

The neutron guides labeled H5x refer to its neutrons originating from the horizontal cold source (HCS).

H53 feeds the three axis spectrometer ThALES, the diffractometer D16 and the backscattering spectrometer IN16.

Note that this model does not show with LEDs the guide H52 in between H511/5112 and H53. H52 feeds the reflectometer SuperADAM and the spin echo spectrometer WASP.