Material Test Diffractometer
Instrument responsible: László Temleitner
The M(aterial) TEST neutron diffractometer is a general-purpose powder diffractometer: it covers the area of medium-resolution powder, liquid and amorphous total (Bragg and diffuse) scattering diffraction measurements, as well. The instrument obtains various sample environments allowing to perform studies on powder samples between 77K — 1273K and spinning, scanning or orienting (by Eulerian-craddle) the samples at room temperature.
The MTEST diffractometer is installed on the 6th axial thermal channel of the reactor. The maximum flux can be obtained at a wavelength of 0.144 nm. A sapphire single crystal is used, deep inside the beam shutter, to filter out epithermal neutrons. The neutron flux at the sample table is 2*106 neutron/(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 adjusted by slits for the required size.
The instrument is equiped with a monochromator changer that uses 3 crystals: Ge(111), Cu(111) and Cu (220), allowing to tailor the beam for the required Q-range and resolution even during the measurement period of one sample (see Table 1).
|Setup||Monochromator||Wavelength [Å]||Q-range [Å-1]||Best resolution||Intensity|
|"Disordered crystal"||Cu(111)||1.45||0.45 - 8.1||0.6°||100%|
|"Medium resolution crystal"||Cu(220)||1.35||0.5 - 8.5||0.6°||40%|
|"Liquid/amorphous"||Cu(111)||1.11||0.65 - 10.6||1.2°||85%|
|"Medium-Q liquid/amorphous"||Cu(220)||0.89||1.0 - 13.1||1.0°||10%|
|"Low-Q liquid/amorphous"||Ge(111)||2.27||0.25 - 5.1||1.2°||6.5%|
A low efficiency fission chamber monitor and an Ordela position sensitive detector (with two sample/detector positions) serve data collections. The ultimate angular upper limit of the detector in "near position" is 141°, whereas 151° at "far position". However, practically the pattern from 7° to 138° can be recorded by 5 positions in the "near" and from 6° 139° by 12 positions in the "far" positions. The current level of background in “near” position equals to the scattered intensity from a 6 mm diameter, 0.05 mm thick, 40 mm long vanadium sample holder.
To mount samples standard O-ring sealed vanadium cans (6 and 8 mm in diameter) are available for room temperature measurements.
- low background vanadium vacuum furnace (RT-1000°C)
- aluminium-shielded cryostate (77K-RT)
- X,Y scanning table for residual stress measurements
Our group is ready to help users, starting from measurements, through data evaluation, simulation and publication.
Figure 1. MTEST overview: sample changer with the "near" position of the detector in the center and vacuum furnace on the left. The width of the dark foot at the left bottom corner corresponds to about 12 cm.
Figure 2. Side view of the sample changer RT setup.