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D17 Neutron reflectometer with horizontal scattering geometry

Characteristics

Sample Environment
Heater stage < 400ºCWater bath, -10 < T < 80ºC5 (solid/liquid) - 7 (solid/air) position sample changerLiquids changerHumidity chamberOff-line Langmiur-Blodgett preparationQuartz window vertical cryomagnet < 7 T, 1.5 - 300 K(Maximum 25 mm sample size w. sample changer for 4 samples, can take dilution insert down to 50 mK)Quartz window horizontal field cryomagnet < 8 T, 1.5 - 300 K(Maximum 20 mm sample size, can take dilution insert down to 50 mK)Electromagnet, B < 1 Telsa for 15 mm pole separation (w. 360º phi sample rotation in-situ)XYZ coils (B < 0.01 Tesla)Contact theinstrument teamfor special requirements or equipment not in the list

Location: Guide hall ILL7, Cold guide H18
Layout for maximum flux:Horizontal scattering geometry, vertical surfaces
Time-of-Flight
Chopper spinning at 550 - 3000 rpmChopper separation  75 mmChopper phase 0-20 deg0.002 Å-1 < q < 2 Å-1Resolution 0.5-20% (wavelength dependent, FWHM)Chopper stopped with windows open for monochromatic modes
Polarised Time-of-Flight
Fe/Si polarising multilayer S-bender (up to 99.9% efficient, wavelength dependent)0.002 Å-1 < q < 2 Å-1
Non-polarised monochromatic
Ni/Ti multilayer stackWavelength 5.5 Å0.005 Å-1 < q < 1.5 Å-1Resolution Δλ/λ = 4% (FWHM)
Polarised monochromatic
Fe/Si multilayer stack (98.7% efficient)Wavelength 5.5 Å0.005 Å-1 < q < 1.5 Å-1Resolution Δλ/λ = 4% (FWHM)
Polarisation analysis
Polarizing Fe/Si mirror analyzer for specular reflection (up to 99.9% efficient, wavelength dependent)3He gas cell polarizing analyzer (covering the detector solid angle) for off-specular reflectionRadio Frequency primary flipper (up to 99.9% efficient, wavelength dependent)Radio Frequency secondary flipper (up to 99.9% efficient, wavelength dependent)
Collimation
Slit separation 3.4 mMaximum slit width 10 mmPrecision 10 µmParabolic guide between the slits to focus the beam vertically
Sample position
White beam flux 9.6x109n/cm2/sVertical sample geometryBeam area at sample 6 x 50 mm (width x height)High precision goniometer for rotation, translation and height
Detector
ILL monoblock tube detector, filled with3He gasMax. count rate 0.75 MHz (measured in monochromatic mode with 5.6 Å neutrons)Translation 1.0-3.1 mRotation -2 to +45 deg.Size 250x480 mm2Resolution 2.2 x 4.8 mm2(width x height FWHM)

Instrument description

D17 is the first ILL dedicated reflectometer and it has been designed to be as flexible as possible in resolution and modes of operation. The supermirror-coated guide provides the highest white beam flux at the sample position in the ILL of 9.6x109 n/s/cm2. This flux, combined with the low instrumental background, allows reflectivities down to 10-7 to be measured.

D17 operates in four modes, time-of-flight, polarised time-of-flight, monochromatic and polarised monochromatic. The time-of-flight modes are realised by a double chopper system with variable phase. The useful wavelength range is from 2-30 Å; the upper limit set by a frame overlap mirror. In the case of the polarised TOF mode a wavelength range of 4-20 Å is polarised by a S-bender. For monochromatic operation, a fixed wavelength of 5.5 Å with a base resolution of 4% (FWHM) is transmitted using multilayer monochromators (polarising or non-polarising) followed by a composite Ni mirror device to remove long wavelength contamination. Changing between time-of-flight and monochromatic modes takes approximately 30 minutes so users are free to change within a single experiment.

The wide angle multidetector allows the simultaneous measurement of background and off-specular scattering, spanning from 4o at sample-detector distance 3.1 m to 13o at 1.1 m.

When operating in time-of-flight mode, a reflectivity curve over an order of magnitude in scattering vector may be measured without moving the sample or detector. The time-of-flight resolution, due to a double chopper system, is entirely flexible and may be selected to maximise flux. In addition, the coherent summation method (ILL15CU401) allows the use of divergent beams without loss of resolution, thus further increasing the usable flux on the sample, meaning that useful reflectivity curves may be measured in less than a minute.  Kinetic measurements, where the sample changes with time, are therefore entirely feasible.  This flexibility in resolution is not available at pulsed sources.

D17 has a wide variety of sample environments, however if you cannot find what you require or want more information on the capabilities of D17, please contact the instrument team who will be happy to provide information and help develop new equipment in collaboration.

The instrument is suitable for the analysis of structural and magnetic properties of surfaces, buried interfaces and in-plane correlations at solid and solid/liquid interfaces. Horizontal surface experiments, such as free liquids, will suffer from a severe restriction in Q-range and flux and are thus not recommended for this instrument. These experiments must be done on the FIGARO reflectometer.

More details in:

Recent upgrades of the neutron reflectometer D17 at ILL, T. Saerbeck, R. Cubitt, A. Wildes, G. Manzin, K. H. Andersen and P. Gutfreund, J. Appl. Cryst. (2018) 51, 249-256

An improved algorithm for reducing reflectometry data involving divergent beams or non-flat samples, R. Cubitt, T. Saerbeck, R.A. Campbell, R. Barker,P. Gutfreund, J. Appl. Cryst. (2015) 48, 2006-2011