Improved system for energy-dispersive x-ray diffraction with synchrotron radiation

Abstract

A number of improvements in a facility developed over the past three years at the Stanford Synchrotron Radiation Laboratory for the study of pressure and/or temperature effects on materials are described. These include improved beam collimation to both reduce background and eliminate gasket scatter, a remote, pneumatically operated pressurizer, and introduction of a variety of electronics hardware to allow both computer control of experiments and on-line data analyses. Considerations are given to the possible effects of heating of the pressure cavity by the incident beam and to possible fluctuations of the incident beam intensity/energy profile. In both cases, there was no evidence to indicate that these phenomena warranted any further consideration, i.e., they are not considered to be problems in terms of analyzing the data. Extended measurements of a well-defined diffraction peak indicated that a considerable improvement over our earlier work has been realized in terms of the precision in the determination of the energy of the peak, viz., a precision of better than 0.04% for measurement periods as short as 10 s; the estimated precision in the net peak area is less than 3%. The system was used to examine the kinetics of the B1-to-B2 pressure-induced phase transition in KBr. The volume change in the two-phase region is measured to be 10.41%±0.10%, in excellent agreement with most of the previous measurements. A plot of the time dependence of the growth rate of the high-pressure phase indicates that the phase transformation can be described by the Avrami equation. Constants for the phase transition kinetics are given.

High-pressure X-ray science on the ultimate storage ring

“…High-pressure researchers utilized DACs for X-ray diffraction studies on second-generation synchrotron storage rings from the late 1970s at DESY (Buras et al, 1977), and also at CHESS (Baublitz et al, 1981) and SSRL (Skelton et al, 1983), typically using energy-dispersive (ED) diffraction techniques, which utilized the full white beam from the synchrotron in order to overcome the problems of a weak signal from the very small sample. The 1980s also saw the development of high-pressure X-ray spectroscopy techniques (principally EXAFS) to probe the local environment of atoms in the crystalline, amorphous and liquid phases at high pressure (Shimomura et al, 1978;Ingalls et al, 1980;Itie et al, 1989;Polian et al, 1989), although the limited intensity from secondgeneration sources restricted the maximum pressure at which data could be attained, while the limited range of accessible X-ray energies narrowed the number of absorption edges that could be studied.…”

High pressure x-ray diffraction techniques with synchrotron radiation

“…[3][4][5][6][7] The first HP XRD experiment integrated with synchrotron technique was pioneered at Hasylab in 1977 by Buras et al [8] Since then the XRD using SR has become the main means of pressure-induced structural phase transition studies. In the 1980s, a number of beamlines at the firstgeneration or second-generation synchrotron facilities, such as DESY (Deutsches Elektronen Synchrotron), [9] CHESS (Conrell High Energy Synchrotron Source), [10,11] SSRL (Stanford Synchrotron Radiation Lightsource), [12,13] photon factory, [14] SRS (Synchrotron Radiation Source, Daresbury), [15] were reported to work for HP XRD studies. The energy dispersive x-ray diffraction (EDXRD) mode was mainly used in these beamlines and the synchrotron x-ray was incoming from the banding magnets.…”

The present status of high-pressure research at Beijing Synchrotron Radiation Facility

“…Because of the extreme spectral brilliance, small divergence, and wide range of wavelengths, synchrotron radiation (SR) has come to be considered the ideal x-ray source for EDXD. Since the first experiment by Buras [1] at DESY, several kinds of EDXD apparatus for DACs have been developed at SR facilities, e.g., CHESS at Cornell University (Baublitz [2], Bassett [3]), SPEAR at Stanford University (Skelton [4,5]), and NSLS at Brookhaven National Laboratory (Jephcoat [6], Hu [7]). Recently, great developments have been achieved by combining a laser heated DAC with in situ x-ray diffraction at thirdgeneration SR sources [8][9][10][11][12], which expanded the range of research under high pressure and high temperature.…”