HPCAT

Based on the high brightness third generation synchrotron sources and development of tunable monochromators with sub-meV resolution, nuclear resonant X-ray spectroscopy has become a relatively new spectroscopic method in recent years and widely used to study materials under extreme conditions. Nuclear resonant X-ray spectroscopy can be divided into two methods: nuclear resonant inelastic X-ray scattering (NRIXS) and nuclear forward scattering (NFS). From NRIXS, density of states can be acquired and important dynamic, thermodynamic, and elastic information derived such as vibrational kinetic energy, vibrational entropy, Debye temperature and sound velocities. From NFS, hyperfine interaction parameters can be acquired giving information on spin state, oxidation state and magnetic ordering.

57Fe nuclear resonant x-ray spectroscopy has attracted particular attention among physicists and geophysicists because Fe is an archetypal transition element and is a dominant component in the cores of the Earth and other terrestrial planets. At HPCAT, a 2-meV high resolution monochromator (HRM) is used for 57Fe and consists of 2 channel cut silicon crystals (Si( 4 4 0) and Si (9 7 5)). We can now routinely measure NRIXS under high pressures using panoramic DACs and two or three APD detectors in close proximity and NFS while under high pressure and low temperature.

During NRS experiments, the bandwidth of the undulator beam is reduced to ~1eV by a liquid N2-cooled Si (1 1 1) double crystal monochromator (DCM) in 16 ID-A. After going through HRM in IDC, the bandwidth of X-ray beam is further reduced to ~2meV. The beam then is focused by KB mirrors hitting the sample in IDD. NRS signals are collected by one avalanche photodiode detector (APD) at the forward direction for an NFS experiment or multiple APDs  which are put as close as possible to the sample for NRIXS experiments.

In an XRS experiment, the incident beam hits the sample, scattered x-ray is collected by spherically-bent single-crystal analyzers and focused to the solid state detector in a nearly backscattering geometry. The incident x-ray energy is scanned relative to the elastic line to determine the inelastic shift. Using the same experimental setup of XRS, we can do an inelastic x-ray scattering experiment to get electronic band structure, excitions, plasmons, and their dispersions under high pressure.  During IXS experiments, both incident x-ray energy and scattering angle need to be scanned to obtain the dielectric function and the dynamic structure factor.

To improve the collection efficiency, we have designed, tested and finished commissioning a 17-element analyzer array.  The array consists of three columns of 2-inch diameter bent silicon (111) analyzers from NJ-XRSTech in a vertical Rowland circle backscattering geometry. The energy resolution of the instrument is 1.0 eV.To reduce the scattering from the surrounding gasket, at the end of 2016, we have made a comparison of x-ray Raman spectra using post-sample slits versus that of a polycapillary optic.  The advantage of the polycapillary is that its field of view is about 50 um, so it does not ‘see’ as much of the gasket scattering.  The tradeoff is that the polycapillary has about a 20% transmission efficiency but a wider acceptance angle of collected scattering.   The results of our comparison show a significant improvement in the signal/background ratio using the polycapillary.  For the same sample and counting times, the background is reduced by an about a factor of 5 using the polycapillary.  This is essential to be able to measure samples at mega-bar pressures.

X-ray emission spectroscopy (XES) provides a unique probe for the diagnosis of pressure-induced spin transition in materials. HP XES experiments have become a routine technique at 16IDD and have been applied to both 3d transition and rare earth metals and their compounds (Mn, Fe, Co, Ce, Gd, etc.).

Resonant X-ray emission spectroscopy (R-XES) studies of transition-metal and rare-earth systems give us important information on electronic states, such as intra-atomic multiplet coupling, electron correlation, and inter-atomic hybridization. In HP R-XES experiments, we use the same setup for XES, but also scan the incident energy across the absorption edge and for each incident energy, fluorescence spectra are collected by scanning analyzers.

Recently, we developed a new cryostat used to measure Fe K-beta XES spectra under different pressures and low temperatures. New Fe-based superconductors were successfully measured. This new development will allow us to study magnetic properties and spin transitions of many functional materials (colossal magnetoresistance material, high temperature superconductor etc.) under high pressure and low temperature.

During XES experiments, emitted photons are collected at 90 degrees from the incident beam by a 4-inch analyzer, which focuses and energy analyzes the emitted photons.  A range of elements can be studied by selecting from Si(111), Si(220), Si(422), Si (331),Si(620) or Si(400) analyzers. 

To improve collection efficiency of the XES experiments, we have begun to commission a seven-analyzer XES spectrometer in Aug 2015. The spectrometer is shown in Figure below. The spectrometer has seven 4-inch spherical bent analyzers arranged in a hexagonal pattern to make it compact and accommodate the opening of the most used 2-inch symmetric diamond anvil cells. Fluorescence from the sample is spectrally analyzed and reflected to a Pilatus 100K position sensitive detector by these analyzers. Right now, only 6 pre-aligned emission line can use all 7 analyzers. We are in the process to motorize angle and radial motions of all analyzers to use 7 analyzers for every emission line.

Falling sphere viscosity measurement was developed using white X-ray radiography with high-speed camera (>1000 frame/second). The high-speed white x-ray radiography setup enables us to investigate viscosity of a wide range of materials including very low viscos liquids (around 1 mPa s or less). Figure 1 shows an example of X-ray radiography images of falling of WC sphere in liquid sulfur in PE cell at high pressure recorded with 5000 frames/second and 0.2 ms exposure time.   In addition, the viscosity measurement can be combined with liquid structure measurement to investigate in situ correlation between structure and viscosity of liquids at high pressures.

This report documents the proceedings of the workshop, "Advances in Matter Under Extreme Conditions", held at the APS in October 2012.  A retrospective of the successes of HPCAT over the past 10 years, as well as opportunities for addressing key grand challenges in future of extreme conditions science were discussed by over 120 people from the US and abroad.  Emerging from the workshop and its discussions is a clear signal of the outstanding opportunities for the future of extreme conditions science at the APS in the years to come.

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HPCAT-Workshop2012-Report-May14-2013_0.pdf11.04 MB 11.04 MB

A Workshop on high-pressure time-resolved synchrotron techniques was held on September 25-27, 2014 at the Advanced Photon Source Conference Center and HPCAT, Argonne National Laboratory. More than 100 participants attended this two-and-a-half-day workshop. The attendees represented a diverse group of researchers at various career stages from different countries (US, Canada, Europe, China, Japan, India, and Australia) and different research environments (universities, national labs, research institutions and user facilities). Attendance of 32 young career scientists (students and postdocs) was made possible through generous travel grants from COMPRES and CDAC.

The workshop purpose and goals included:

  • Identifying scientific goals and associated technical challenges for time-resolved studies using synchrotron radiation and laser driven sources
  • Presenting recent results of time-resolved high pressure research carried out at HPCAT and other facilities
  • Demonstrating available facilities and software during hands-on sessions
  • Motivating students and early career researchers to pursue time-resolved research programs

The workshop focused on novel and emerging techniques and capabilities, and the presentations were mostly given by known experts in the related fields in order to provide a balanced representation and coverage in specified sub-fields. The plenary part of the workshop consisted of one general overview and perspectives session and four topical sessions with 28 talks covering:

  • Time-resolved high-pressure x-ray imaging
  • X-ray micro-diffraction with fast compression and decompression
  • Pulsed/ramped laser heating and x-ray micro-diffraction
  • New time-resolved high-pressure X-ray techniques and directions and related topics (including time-resolved Laue techniques, time-resolved inelastic techniques, laser based dynamic compression of materials and an overview of current status and new developments in fast detectors)

There were 39 posters in the poster session, including techniques and instrumentation posters from HPCAT and contributed posters from attendees (mostly young career scientists).

On the third day, attendees participated in four parallel hands-on / demonstration sessions. These sessions were held at HPCAT and covered:

  • Fast (de) compression and cyclic pressure generation and control in DAC,
  • Pulsed and ramped laser heating in DAC,
  • Fast imaging,
  • Large-volume data reduction and analysis.

The hands-on / demonstration sessions were followed by tours of HPCAT experimental facilities.

Workshop organizing committee: Stas Sinogeikin (CIW), Tom Duffy (Princeton), Will Evans (LLNL), John Tse (USASK), Nenad Velisavljevic (LANL), Choong-Shik Yoo (WSU)

Local Organizing committee (HPCAT/CIW): Stas Sinogeikin, Yoshio Kono, Yue Meng, Dmitry Popov, Guoyin Shen, Jesse Smith, Yuming Xiao, and Freda Humble (local administrator).

Workshop was sponsored by HPCAT, COMPRES and CDAC

The PDF file with complete program, abstracts, and list of participants is attached.

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HPTR_Workshop_2014_Program_Abstracts.pdf3.03 MB 3.03 MB

HPCAT hosted a group of eight graduate students as part of the 2018 Neutron and X-ray School on July 26-27, 2018. Beamline scientists, Dr. Changyong Park and Dr. Dmitry Popov, gave hands-on training for high-pressure X-ray diffraction experiment at 16-BM-D using a diamond anvil cell and a practical guide to the data analysis to the students during the two-day classes.

The main purpose of the National School on Neutron and X-ray Scattering  is to educate graduate students in the use of major neutron and X-ray facilities. Students conduct short experiments at Argonne's Advanced Photon Source and at Oak Ridge National Laboratory's Spallation Neutron Source and High Flux Isotope Reactor, which provides hands-on experience for using neutron and synchrotron sources.

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GSECARS, HPCAT and Barnett Technical Services hosted a hands-on workshop on May 10, 2018 dedicated to demonstrating the techniques and future developments of micro-manipulation work using the Axis Pro Micromanipulation System.  

This workshop provided a collaborative interaction between scientists throughout the U.S. to share best practices in their micro-manipulation work.   Users learned about valuable techniques from others who perform the art and discussed future developments to provide for additional sampling modalities that will allow for extensions of their research.

The morning session was comprised of presentations on methods and procedures, followed by an afternoon session with hands-on experience with these tools.  Applied techniques demonstrated the use of the micromanipulator in loading DACs. 

HPCAT beamline scientist, Ross Hrubiak, was a presenter and co-organizer.

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On April 19, 2018, HPCAT hosted Chicago-area High School girls for the Science Careers in Search of Women Conference (SCSW) at Argonne National Laboratory. The young women attend the conference to learn about the research conducted at the laboratory, to network with professional women scientists and engineers, and to learn about careers in science and technology.  The students were given a presentation by Beamline Scientist Yue Meng on the basics of high pressure science, and the high pressure research conducted at HPCAT.  They were given a tour of HPCAT facilities and the ID-B experiment station.  The students asked thoughtful questions and held and examined a diamond anvil cell. HPCAT enjoys the opportunity to participate in S.T.E.M. outreach activities each year.

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Itaru Ohira is a visiting scientist to HPCAT for the next year from Tohoku University, Japan, where he recently completed his Ph.D.  His research focuses on the stability and elastic properties of hydrous minerals, and the structure of silicate glasses at the lower mantle conditions.

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