Material Test Diffractometer
Instrument responsible: László Temleitner
The M(aterial) TEST neutron diffractometer is a general-purpose neutron powder diffractometer. It covers the range of medium-resolution powder, liquid and amorphous total diffraction (Bragg and diffuse scattering) measurements. The available sample environments allow to perform powder studies between 77K — 1273K. Spinning the samples is possible only at room temperature.
The MTEST diffractometer is installed on axial thermal channel No. 6 of the reactor. The maximum flux can be obtained at a neutron wavelength of 0.144 nm. A sapphire single crystal, positioned deep inside the beam shutter, filters out the epithermal neutrons. The neutron flux at the sample table is 2*106 neutrons/(cm2*sec) at a wavelength of 0.133 nm. The standard size of the beam is 10 mm (width) x 40 mm (height), which can be adjusted by slits to the required size.
The instrument is equiped with a monochromator changer which uses 3 crystals: Ge(111), Cu(111) and Cu (220), allowing to tailor the beam for the required Q-range and resolution even during data collection on a sample (see Table 1).
|Setup||Monochromator||Wavelength [Å]||Q-range [Å-1]||Intensity|
|"Disordered crystal"||Cu(111)||1.45||0.35 - 8.2||100%|
|"Medium resolution crystal"||Cu(220)||1.35||0.4 - 8.8||40%|
|"Liquid/amorphous"||Cu(111)||1.11||0.45 - 10.7||85%|
|"Medium-Q liquid/amorphous"||Cu(220)||0.89||0.55 - 13.3||10%|
|"Low-Q liquid/amorphous"||Ge(111)||2.27||0.25 - 5.2||6.5%|
A low efficiency fission chamber monitor and a position sensitive detector system serve for data collection. The detector sytem consists of three banks whose centers spaced by 33 degrees. The low angle bank currently contains 3 pieces of 1 inch and 1 piece of half inch diameter, whereas the high angle bank contains 5 pieces of 1 inch diameter, 60 cm long Reuter-Stokes linear position sensitive 3He detectors placed typically 800 mm from the sample, covering +/-19.6 degrees. In the middle bank, an Ordela 2 inch high, 20 cm wide linear position sensitive 3He detector is installed 780 mm from the sample, covering +/-6.85 degrees. Although, the ultimate angular upper limit is 153.6 degrees, the arrangement allows to record the total scattering powder diffraction pattern from 4.5 to 142.6 degrees in 2Theta by only two positions of the system by 0.6 degrees as best resolution.
To mount samples for room temperature measurements, standard O-ring sealed vanadium cans (6 and 8 mm in diameter) are available.
Additional sample enviromnents (contact the instrument responsible and discuss their actual availability):
- low background vanadium vacuum furnace (RT-1000°C)
- aluminium-shielded cryostat (77K-RT)
In publications involving MTEST please refer to:
Kőszegi, L. "New Outlook of a Strain Scanner Neutron Diffractometer at the Budapest Research Reactor" Journal of Neutron Research. 9(2001) 381-384. DOI: 10.1080/10238160108200166
Further improvements of the instrument have been mentioned in:
K. Karalis, L. Temleitner, G.S.E. Antipas, L. Pusztai, A. Xenidis: "Experimentally constrained atomic order probing of a Si–Al composite glass", Philosophical Magazine 94(2014) 792-800
Our group collaborates with the users, by taking part in the experiemntal work, through data evaluation, simulation to publication of the results.
|Figure 1. MTEST overview: the thermal neutron white beam is monochromatized by crystals (inside the blue colored cylindrical object on the right). The monochromatic beam passes through the collimators (inside horizontal metal cylinder), monitor counter and hits the sample (Eulerian craddle at center). Scattered neutrons are detected by the position sensitive detectors placed at the end of the fan-shaped wooden block (shielding).|
|Figure 2. Downstream view of the room temperature sample changer setup of MTEST.|