Low-Temperature, High-Pressure X-Ray Diffraction Equipment

◆Equipment overview

This system consists of a horizontal, single-axis, swingable goniometer, and two types of two-dimensional X-ray detectors, an imaging plate and a flat panel detector, all installed in the GM freezer.

◆Features of the Equipment

Diffractometer
This equipment is an X-ray diffractometer equipped with a GM freezer and a diamond anvil high-pressure device (Diamond anvil cell, DAC). A high-load-bearing precision stage for positioning can be set with the freezer, which has a high-precision 1-axis rotation stage installed vertically. By adjusting the precision XYZ stage, the high-pressure sample can be matched to the center of rotation of the diffractometer. The accuracy of the center of rotation (eccentricity) in the horizontally aligned freezer sample is less than 5 microns. Diffraction experiments are possible while vertically swinging the freezer ±30 degrees.

Detector
Imaging Plate (IP) X-ray detector: This detector has a large area, wide dynamic range, with a wide measurable X-ray energy range. It is mainly used to observe reciprocal lattice space and acquire accurate diffraction line strength through precise crystal structure analysis. When measuring, the camera length between the detector and the sample can be moved in a range of 220~540 mm depending on the measurement angle range and the angular resolution. When the camera length is 500mm, the angular resolution is 0.001 degrees. If the camera length is set to 220mm and offset horizontally, the observable diffraction angle can be spread to 45 degrees or more. The IP detector is an R-AXIS IV⁺⁺ detector manufactured by Rigaku, with an area of 300×300 mm², a read resolution of 0.10mm and a dynamic range of 20 bits.
Flat Panel X-Ray Detector (FPD): This detector is a two-dimensional, high-energy X-ray detector with CsI:Tl directly deposited. It is possible to read two-dimensional diffraction images at high speeds, but it is also used for measuring time decomposition measurements for real-time monitoring. When measuring the camera length between the sample and the detector, it is possible to move within a range of 200~450 mm. The FPD is a XRD0822 CP23 detector manufactured by Perkin Elmer, with 1024×1024 pixels, a 0.20 mm pixel pitch, a dynamic range of 16 bit, and a frame rate of 25 fps.

Control Software
The control of the IP detector is a dedicated software developed by Rigaku. The FPD detector is operated from measurement software programmed by LabVIEW and manufactured by National Instruments. Various stages are controlled by Tsuji Electronics steppe motor PM16C and operated by software programmed by VB or LabVIEW.

Available Electric Field: 14.4~61 keV
Energy Resolution: ΔE/E~10^-4
Beam Size: φ0.01~1.0 mm (FWHM)
Beam Intensity at Sample Position: : 1×10¹¹ photons/sec (30 keV, Beam Size φ0.01 mm), 5×10¹⁰ photons/sec (61 keV, Beam Size φ0.01 mm)

◆Equipment accessories

Online Raman Scattering Spectrometer
・Excitation Light Source: CW (continuous) oscillating DPSS laser 532 nm (100 mW)
・Splitter: Teledyne Princeton Instruments SP2500i
・Grating: 1200 gr/mm, 1800 gr/mm，f = 500 mm
・Detector: Electric Cooling mechanism CCD (Teledyne Princeton Instruments PIXIS）
・Control and Measurement Software: Teledyne Princeton Instruments Light Field
・Raman Probe Unit (Object Lens: ×20，WD95mm; Glassy Carbon Mirror use can be monitored at all times)

Resistivity Measurements: For simultaneous measurement of low-temperature, high-pressure X-ray diffraction and resistivity
In the freezer system, the signal wire (lead wire) is necessary for the resistivity measurements using the four-terminal method.

◆Experiment / sample preparation

・Low-temperature, high-pressure experiments are based on the use of a high-pressure device that can be mounted in the permanent freezer, a Diacell®Bragg-LT type CuBe system diamond anvil cell (DAC). However, if the appearance size (including the fixed screw position) is the same as the DAC, it can be incorporated into the freezer.
・Prepare the gasket material for sample enclosure in Rhenium or stainless steel (SUS301) but do not use Tungsten as it becomes very brittle at low temperatures.
・When drilling the gasket materials, do not leave burrs in the holes.
・The opening angle of the diamond anvil should be selected considering the X-ray wavelength and diffraction angle measuring range.
・When filling the sample chamber with rubies (Al₂O³: Cr³⁺）as pressure markers, please set a small grain of ruby at the anvil tip, in the incident direction of the excitation laser.
・If you would like to use the diamond anvil cell high-pressure device installed in the beamline, please contact us in advance.
・Please contact us if you wish to use a glovebox for experiments under quasi-hydrostatic conditions using a Helium pressure medium for sample preparation.

◆Experimental procedure / precautions

Basic Experimental Procedures
・Using standard substances, determine the incident X-ray wavelength and camera length (distance between the sample and the detector).
・Confirm the departure substances diffraction pattern.
・Enclose the sample in the high-pressure diamond anvil cell (DAC) (optionally, for using Helium as the pressure medium for high-pressure gas filling, use the glovebox).
・For low-temperature pressurization, the DAC Helium gas driving force is replaced.
・Assemble the freezer and the vacuum chamber
・Complete pressure measurement in the DAC sample chamber (ruby fluorescence or diamond raman method)
・Transfer samples in the DAC to the X-ray irradiation position
・Adjust the X-ray beam stopper position and complete X-ray diffraction measurements
・Cool in the freezer
・Acquire X-ray diffraction measurements at the intended temperature and pressure, as DAC pressurization occurs at constant temperature, and after heating up and cooling down (Change the temperature and pressure course according to the experimental objective).

Notes
・DAC equipment has matching parts (for example, piston and cylinder matching parts) that need to be wiped clean to remove all oil, dirt and other impurities when assembling the DAC.
・Diamond anvils used in the DAC may be destroyed when under high load during pressurization.
・At the end of the experiment, please lower the pressure at low temperatures and raise the temperature of the freezer. If increasing the pressure is required under pressure, please monitor the pressure in the DAC sample chamber and perform the heat rise while adjusting the pressure.

◆Contact

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◆List of representative treatises

Crystal Structure of the Superconducting Phase of Sulfur Hydride
M. Einaga, M. Sakata, T. Ishikawa, K. Shimizu, M. I. Eremets, A. P. Drozdov, I. A. Troyan, N. Hirao, Y. Ohishi
Nature Physics, 12, (2016) 835?838.
DOI:10.1038/nphys3760

High Pressure-Low Temperature Phase Diagram of Barium: Simplicity Versus Complexity
S. Desgreniers, J. S. Tse, T. Matsuoka, Y. Ohishi, Q. Li, Y. Ma
Applied Physics Letters, 107, (2015) 221908.
DOI : 10.1063/1.4936849

Superconducting state of Ca-VII below a critical temperature of 29 K at a pressure of 216 GPa
M. Sakata, Y. Nakamoto, K. Shimizu, T. Matsuoka, Y. Ohishi
Physical Review B, 83, (2011) 220512(R).
DOI: 10.1103/PhysRevB.83.220512

Evidence from x-ray diffraction of orientational ordering in phase III of solid hydrogen at pressures up to 183 GPa
Y. Akahama, M. Nishimura, H. Kawamura, N. Hirao, Y. Ohishi, K. Takemura
Physical Review B, 82, (2010) 060101(R).
DOI: 10.1103/PhysRevB.82.060101

Direct Observation of a Pressure-Induced Metal-to-Semiconductor Transition in Lithium
M. Takahiro, K. Shimizu
Nature, 458, (2009) 186?189.
DOI : 10.1038/nature07827