Materials Science with Neutrons and X-Rays at FRM II:

The neutron/X-ray contrast reflectometer N-REX⁺

The Department Prof. Dosch of the Max-Planck-Institut für Metallforschung operates the combined neutron/X-ray reflectometer N-REX⁺ at the FRM II in Garching (near München). First standard user experiments have been conducted in May 2007. The instrument is designed to perform a variety of experiments, e.g.:

• specular and off-specular reflectivity measurements on surfaces and interfaces of solid and liquid samples
• grazing incidence / evanescent wave diffraction
• in-situ X-ray characterization
• neutron/X-ray contrast experiments
• experiments with polarized neutrons, including wide angle neutron spin analysis
• spin-echo resolved grazing incidence neutron scattering (SERGIS)

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Basic instrument features

N-REX⁺ is a "Tanzboden" instrument in the neutron guide hall of FRM II and uses a monochromatic beam extracted from the cold neutron guide NL-1.

The instrument is equipped with:

• a horizontally focussing HOPG monochromator
• a two-dimensional ³He wire chamber neutron detector
• a compact add-on X-ray reflectometer
• spin-echo equipment for diverse applications
• ³He cells for neutron spin analysis (link to HELIOS)
• facilities for on-line viewing and evaluation of the data

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Sample environments

Various different sample environments are available, e.g.:

• sample orientation: horizontal or vertical
• magnetic fields up to 7.5 T
• low temperatures down to 4 K or less
• low pressure atmosphere of various gases or vapours (T < 300 °C)
• large diameter (overall 100 mm) silicon liquid film cell (T < 100 °C)
• active anti-vibration device for experiments on free liquid surfaces
• liquid thermostat for cooling and heating to medium temperatures
• medium pressure (p < 10 bar) gas cell with silicon substrate

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Technical instrument parameters

Basic N-REX⁺ instrument parameters
(for liquid mode, HOPG monochromator, 20 MW reactor power):

• wavelength range: 2 - 6 Å
• max. incidence angle: 5°
• max. exit angle: 20°
• max. out-of-plane q (specular): 0.55 Å^-1
• max. q (within reflection plane): 1.35 Å^-1
• max. in-plane q (grazing angle diffraction): >5.4 Å^-1
• total flux at monochromator: 4·10⁹ neutrons/cm²s
• maximum flux at monochromator:
  4·10⁸ neutrons/cm²sÅ (at 4 Å)
• monochromatic flux for reflectometry at sample:
  3·10⁶ neutrons/cm²s (estimated)

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Beam-time application

Applications for beam-time at N-REX⁺ can be submitted here:
FRM II User Portal

N-REX⁺ user and visitor information:
German
English

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Links

To learn more about this project you can read the proposal for the Max-Planck reflectometer at FRM II (pdf-file, 568 kB) or the Max-Planck press release about the inauguration of the instrument.

You are also invited to visit the image gallery showing N-REX⁺ and some of its components during the construction phase.

The first "historic" reflectivity measurement performed in 2005 on a MgF2/Au/glass system is posted here.

Some more recent (2006) images of N-REX⁺ in the NRSE-SERGIS operation mode are available from here.

Neutron-related links.

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Contact

Beamline contact information
Beamline responsible
Dr. János Major	+49-711-689-1264
On-site staff
Dr. Adrian Rühm	+49-89-289-12184
Dr. Sergey Kozhevnikov	+49-89-289-14769
Jörgen Franke	+49-89-289-14732
Max Nülle	+49-711-689-1918
Beamline contact
Instrument area	+49-89-289-14878
Beamline office	+49-89-289-12184 or -14732
Beamline fax	+49-89-289-14989