This instrument is operational .
Inside the Wish instrument
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Wish is a long-wavelength diffractometer primarily designed for powder diffraction at long d-spacing in magnetic and large unit cell systems, with the option of enabling single-crystal and polarised beam experiments.
In complex systems, the magnetic structure has a large number of degrees of freedom (typically the three components of the magnetic moment on several inequivalent atoms), and the d-spacing range available to observe Bragg peaks is limited due to fall-off of the magnetic form factor.
High-resolution cold-neutron powder diffraction excels when multiple nearly overlapping Bragg peaks occur at long d-spacing. In this case, sheer flux is not sufficient to extract all the available information, and much better results can be obtained with a high-resolution diffractometer such as Wish, even at the cost of losing some flux.
Wish provides high resolution data over ad-spacing range from 0.7-17 Å with a single frame bandwidth of 8 Å. Wish uses pixellated 3He detectors covering scattering angles from 10 to 170 degrees.
For further information please see: LC Chapon, P Manuel et al, Neutron News 22 (2011) 22-25.
On Wish, the good resolution reveals previously unseen details and the high count rate allows a wide range of parameters relevant to the function of the material to be studied.
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