The Surface Diffraction Beamline consists of two stations focusing on different samples.Hutch 1 is designed as a general purpose surface diffraction station that can perform a variety of surface and interface diffraction experiments for thin film and solid-solid interface structural studies, with enough space to install specially designed in-situ equipment. Hutch 2 is a station specifically designed for structural studies of liquid surfaces, solid-liquid, and liquid-liquid interfaces. Hutch 2 is an experimental station for liquid surface, solid-liquid, and liquid-liquid interfaces. Experimental Station.
General arrangement of the endstations
The Hutch 1 is equipped with a high-precision multipurpose diffractometer. The diffractometer has 4 sample circles + 2 detector circles + 3 analyzing crystal circles, and the high-resolution positioning of the rotational axes permits a range of 2θ up to 170° with a step accuracy of 0.0005. The diffractometer has a double detector arm with a scintillation detector and a small surface detector (Eiger 500k) that can be rotated around its plane. The total load capacity of the detector arms is up to 150 kg. The scintillation detector-to-sample distance is manually adjustable between 700 mm and 1100 mm. The small surface detector system can be adjusted manually by 520 mm and electrically by an additional 400 mm. The diffractometer is also equipped with a high-precision translation stage, a telephoto microscope, a goniometer head, a slit, a cryogenic holder and an adjustable attenuator. At the end of Hutch 1, a Pilatus 2M (1000 μm Si) large surface detector was also installed. The pixel size of the large surface detector is 172 × 172 μm. For maximum flexibility in detector position, the detector is mounted on an xyz displacement stage of the specified design. Typical sample-to-detector distances range from 150 mm to 400 mm for reflectance (including GIXRD) and transmission modes as well as for X-ray diffraction measurements in in-situ experiments.
Experimental station layout. Hutch 1 Equipment:(a) Multi-purpose diffractometer system. (1) Sample stage. (2) Eiger 500K. (3) Point detector. (b) Large surface detector system. (1) Pilatus 2M. (2) Detector Positioning Stage - Sample Stage. Hutch 2 Equipment: (c) Liquid Diffraction System (1) Bicrystal Deflector, (2) Diffractometer. (d) Bicrystal deflector schematic.
The diffractometer in Hutch 2 is dedicated to liquid-oriented surface X-ray diffraction experiments. The diffractometer has 4 sample circles (2 horizontal and 2 vertical) + 2 detector circles + double crystal deflector. In particular, a bicrystal deflector placed upstream of the diffractometer and a companion Eiger 4M 2D surface detector were designed for the study of liquid surfaces and liquid-liquid interfaces. By adjusting the direction of the incident beam, reflectance and grazing incidence diffraction measurements of liquid surfaces and interfaces can be realized. For example, for a 10 keV incident beam, the horizontally incident beam is deflected by Ge(111) and Ge(220) crystals, and the beam can be bent downward by up to 14.2°，enabling structural characterization under sample horizontal conditions.
The BL02U2 beamline also offers a wide range of experimental environments. Nitrogen/Argon, high temperature (up to 1500 K) and cryogenic (down to the liquid nitrogen range) thin film in-situ devices are available for use on the diffractometer of the Hutch 1, and the Hutch 2 offers an LB tank for liquid scattering. The in-situ electric field unit provides a voltage source (0-3000 V) for investigating the structure of thin film samples under an electric field.
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