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ECHIDNA - High Resolution Powder Diffractometer
The instrument serves to determine the crystalline structures of materials using neutron radiation analogical to X-ray techniques.
It will operate with thermal neutrons. One of the main features is the array of 128 collimators and position sensitive detectors for rapid data acquisition. ECHIDNA will allow structure determinations, texture measurements and reciprocal space mapping of single crystals in most different sample environments serving the physics, chemistry, materials, minerals and earth-science communities. ECHIDNA is part of the Bragg Institute's park of neutron scattering instruments.
The Australian instrument, mother of all monsters, is named after the Australian monotreme echidna. Spiny peaks allude to the high resolution of the instrument.
Additional recommended knowledge
The sample is supported by a heavy load goniometer consisting of a 360° vertical omega rotation axis, x-y translation tables and a chi - phi cross tilt stage of +/-20° range. It can hold a few hundred kilograms in order to support heavier sample environment, such as cryostats, furnaces, magnets, load frames, reaction chambers and others. A typical powder sample is filled into vanadium cans which give little, unstructured background. The mentioned sample environment allows to measure changes of the sample as a function of external parameters, like temperature, presser, magnetic field, etc. The goniometer stage is redundant for most powder diffraction measurements, but will be important for single crystal and texture measurements, where the orientation of the sample plays a role.
A set of 128 detectors each equipped which a 5' collimator in front are arranged in a 160° sector focusing to the sample. The collimators select the scattered radiation into the well defined ranges of 128 angular positions. All the collimator and detector setup is mounted on a common table which is scanned in finer steps around the sample, to be combinded further to a continuous diffraction pattern.
The 128 linear position sensitive 3He gas detector tubes cover the full opening height of 300 mm behind the collimators. They determine the position of the neutron event by charge division over the resistive anode towards each end of the detector. Overall and local count rates lie in the several 10000 Hz range.
|This article is licensed under the GNU Free Documentation License. It uses material from the Wikipedia article "ECHIDNA_-_High_Resolution_Powder_Diffractometer". A list of authors is available in Wikipedia.|