MTEST diffractometer

László Temleitner, László KőszegiLiquid Structure Research Group, Complex Liquids Department,Institute for Solid State Physics and Optics, Wigner Research Centre for Physics

The M(aterial)TEST diffractometer originally designed to study internal stress of alloys. Recently, upgrade procedure started, which targets the development of the instrument for high-resolution diffractometer with various available sample environment. At the present status, it makes possible to perform total (Bragg and diffuse) scattering measurements on powder, liquid and amorphous materials. The four-circle goniometer makes also the chance for texture measurements as well.

MTEST diffractometer is installed on the 6th axial thermal channel of the reactor with maximal flux at 0.144 nm. A sapphire single crystal is used, deep inside the beam shutter, to avoid the epithermal neutrons. The flux of neutron at the sample table is 2*106 neutron/(cm2*sec) at 0.133 nm.

To produce monochromatic beams various single crystals are available (Table 1.) at the beamline. To make the change of the wavelength easy, monochromator changer has been designed with 3 crystals (Ge(111), Cu(111) and Cu (220)) making possible to change the wavelength during the reactor cycle.

The diffractometer equipped with air cushions to achieve the necessary flexibility for a continuously variable wavelength. Thus, monochromator take-off angle is able to be change from 15° to 90° degrees, which allows to produce neutron beams from 0.065 nm to 0.35 nm wavelength. Although, this option is available, we keep the take-off angle around 40° degrees to achieve the highest flux on Cu (111).

From the monochromator to the sample various Soller-type collimators are able to be set up (1°, 40', 30' and 12').

Low efficiency fission chamber monitor and a BF3 single detector serve the data collections and various sample-detector collimators are available. Ordela position sensitive detector installed with 2 available distances from the sample. Its commissioning is in progress (scheduled to end in July of 2013). The diffraction spectra can be measured up to 144º by single detector, to 142° by “close position” and to 150° by “far position” of the position sensitive detector. The angular range from 7 degrees to the end point can be covered by 6 (“close”) and 14 (“far”) angular positions of the position sensitive detector

At sample stage, the next options are available over four-circle goniometer:Automatic X, Y sample displacements, manual Z displacement.Automatic sample changer is available for 4 samples. (only with four-circle goniometer)Sample environment: vacuum-furnace (RT-1000ºC) (available) and liquid N2 cryostate (scheduled to be installed in 2013 and commissioned in the first half of 2014).

Our department is ready to help users from measurements, through data evaluation, simulation and publication.

Instrument responsible: László Temleitner

Table 1. Available monochromatorsMonochromator Ge(111) Cu(111) Ge(220) Cu(220)

Wavelength at 40° take-off angle (nm) 0.223 0.143 0.137 0.087

Q-range (Å-1) 0.25~5.35 0.4~8.35 0.4~8.7 0.65~13.7

Figure 1.

Thermal neutrons

Shieldings

Sapphiresingle crystal

Monochromator

2 movement (from 0° to 141°)Θ

Sample and its rotation

Air cushions

Detector

MTESTDiffractometer

a. Top - view of the whole system

b. Side - view of the 4 - circle diffractometer

Detector

Tilting (from -13° to +38°)

Sample position

Sample table

Connection to themonochromator

shielding

channel No.6.

Reactor

Figure 2. MTEST diffractometer with the goniometer option together with the vacuum-furnace (RT-1000ºC)

Figure 3. MTEST diffractometer with the automatic X, Y sample displacements.