Experiments

PAPYRUS, formerly PAPOL, is a spectrometer that has been modified to perform Grazing Incidence Small Angle Neutron Scattering (GISANS). It is primarily devoted to the study of surface and interface at the nanometer scale. GISANS (and SANS) can be performed using a 0.8nm wavelength neutron beam with polarization option (94% polarization, 45% transmission). It allows to work in the Q-range 0.02-2.4 nm^-1 thanks to a 64x64 cm BF3 detector grid (128x128 cells) and an adjustable sample-to-detectors distance (min=1m,  max=4 m). PAPYRUS can also be used as a standard polarised neutron reflectivity instrument, probing structural and magnetic depth profile.

The GISANS configuration, schematically represented above, is particularly useful for the study of domain formation in magnetic thin films, organized nanostructures (nanowires, nanodots) and soft matter materials.
By detecting off-specular scattering perpendicular to the incident plane (q_Y direction, green area) one can bring information on the lateral (planar) correlations between nanometer scale objects deposited on a surface or confined at interfaces with typical size between 5 and 100 nm.
Off specular scattering in the incident plane (light blue area) also brings information about lateral structures (in the plane of the surface) but with typical length scales from 600nm to 60mm.

                                                          Flat mirrors in reflection geometry

                                                         The polarisation option can be switched off to run in unpolarized mode.

Superconducting Horizontal magnet:5T Oxford Instruments split coil

with high homogeneity (5 10^-5), horizontal access parallel (diameter 89 mm)
and perpendicular to the field (diameter 42 mm)
Dilution insert to cool the 4He-filled sample holder to T = 0.2 K

maximum angle  = 17.7^o  (D=1 m)
                         = 4.57^o (D=4 m)

D₀=1 m        0.008 Å^-1 < Q < 0.24 Å^-1
D₀=4 m        0.002 Å^-1 < Q < 0.06 Å^-1

PAPYRUS uses a monochromatic beam of wavelength 0.8±0.05nm on the lower part of the G5 guide . The monochromator is a Ni-Ti multilayer on Si substrate. The polarised neutron beam size is 25x25 mm2.  For topological reasons the detector array is placed outside the vaccum tank. For this reason, the sample-to-detector distance can only be changed by increments of 1 m between 1m and 4m.

Polarizer

Adiabatic Flipper



Collimation and slits





There are two Cadmium slits (F1 and F2) separated by 4m. The first slit F1 is located between the 3m neutron guide and the adiabatic flipper. The F2 slit is right before the sample area. A sliding device allows to adjust the distance bewteen F2 and the sample position according from a few cm up to 30-50cm.


The resolution is, roughly speaking, given by R=(W1+W2)/2L where W1 and W2 are the slits openings and L is the slit separation (see figure)/
For W1=W2=2 mm and L=3 m, we have R=0.04 degrees.


Sample environment

       

Detector tank
   

The lenght of the detector tank is ajustable from 1m to 4m by chunks of 1m. To maximise transmission, the tank is under vacuum. The direct beam is blocked before hitting the detcctors by an absorber (Cadmium plate).

The neutron detection is obtained by an XY BF3-type detector. The detection coverage is 64x64 cm and each cell is 0.5x0.5cm (128x128 pixels).

Scattering Length Densities for some usual materials: doc file