Moderator

Target Station 2 moderator

Coupled moderator

The coupled moderator is a composite hydrogen/solid-methane system without a decoupler or poisoning layer, that generates an intense, long-wavelength flux with broad pulse shapes from two distinct faces.

A solid-methane face with a deep, narrow groove giving high brightness and a cold spectrum has been designed for small angle scattering and reflectometer instrumentsthat view only a small area of the moderator surface. A flat hydrogen face has a slightly warmer spectrum and a much larger flux integrated over the whole face. It has a complex pulse shape at long wavelengths.

The flux per accelerator pulse for this moderator is more than 15 times that of the existing decoupled hydrogen moderator at long wavelengths.This means that whilst the proton power is 4 times lower, the total number of neutrons produced will be over 4 times greater than that of the existing ISIS hydrogen moderator when running at 200 µAmps proton current.

 Grooved faceHydrogen face
Area of face8.3 cm wide x 3 cm high12 cm wide x 11 cm high
MaterialSolid methaneHydrogen
Temperature26 K26 K

 

Decoupled moderator

The decoupled solid-methane moderator has multi-vane gadolinium poisoning and will give a similar flux to the existing ISIS water or liquid-methane moderators, but with a muchcolder spectrum.

One face has a narrow pulse shape similar to the existing liquid methane moderator although with a much cooler spectrum, whilst theother has a broader pulse shape similar to the existing hydrogen moderator.

 Broad pulse faceNarrow pulse face
Area of face12 cm x 12 cm12 cm x 12 cm
MaterialSolid methaneSolid methane
Temperature26 K26 K
DecouplerCadmium
PoisonGadolinium vanes

 

Moderator performance

Intensity vs Energy

Intensity vs Energy

Pulse Width vs Wavelength

Pulse Width vs Wavelength

Intensity vs Wavelength

Intensity vs Wavelength

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