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CORNELL LABORATORY FOR ACCELERATOR-BASED SCIENCES AND EDUCATION — CLASSE

XDL2011 Workshop 4

High-pressure Science at the Edge of Feasibility
Thursday, June 23rd - Friday, June 24th, 2011


Organizers: Russell J. Hemley (Carnegie Institute of Washington), Neil Ashcroft (Cornell University), Roald Hoffmann (Cornell University), John Parise (SUNY Stony Brook), Zhongwu Wang (Cornell University)

Workshop Agenda (html)
Workshop Poster (pdf)


Purpose: The purpose of the workshop is to assess the state-of-the-art in the use of synchrotron x-ray diffraction and other x-ray related spectroscopic techniques to (1) determine the structures and properties of materials at extreme conditions, and (2) to explore the time-resolved dynamics and kinetics of the nucleation, growth and transformation of materials under extreme conditions of pressure, temperature and strain rate etc. There is special interest in exploring scientific breakthroughs that may be enabled by the Energy Recovery Linac (ERL) or Ultimate Storage Ring (USR) sources that are under development.

Description: (1) In-situ synchrotron x-ray diffraction and spectroscopes of materials under extreme conditions. The structural, physical, and chemical properties of materials change dramatically under high pressure, e.g., graphite transforms to diamond and much of the elements on the periodic chart become superconductors. The novel structures and manifested properties of materials at extreme conditions have already had dramatic impact on a variety of scientific fields and technological applications. These include synthesis of novel high energy metastable materials and superhard phases and nanocomposites with enhanced toughness and strength, energy storage and industry technologies, reaction chemistry and transition kinetics of energetic materials, and environmental and planetary sciences.

Currently developed synchrotron light sources like CHESS, NSLS, APS, ESRF and Spring-8 have enable in-situ x-ray diffraction and spectroscopic measurements to monitor the pressure-tuned structure and properties of materials. However, experiments at the most extreme conditions at these sources are almost always photon starved. For example, while heavy element compounds may be studied to a maximum static pressure of 300 GPa, it is difficult to study low-Z elements and compounds at even 100 GPa. At the highest attainable static pressures samples are invariably tiny, subject to strain gradients, and the resultant quality of the x-ray signals tends to be poor.

The ERL source being developed at Cornell is a next generation x-ray source that promises to deliver ultra-bright x-ray beams that can increase the flux in submicron beams by many orders of magnitude over existing sources. USR, such as the PEP-X project being suggested at SLAC would likewise have potential to deliver beams of unprecedented quality. As we approach submicron and nanosize x-ray beams, a wide range of x-ray diffraction and related spectroscopes will become possible with these machines on materials under extreme conditions. For example, temporally and spatially resolved diffraction and imaging can be used to exploit structure change, deformation, and tuning mechanisms of materials under extreme compression and at high strain rate.

This workshop will bring together practitioners of newly developing and proposed x-ray related areas with researchers from a wide spectrum of scientific fields using single and multiple techniques to exploit frontier science under extreme pressure conditions. The ultimate goal is to map out future developments and frontier research directions using x-ray related techniques for in-situ measurements of structure and properties of materials under extreme conditions, and thus to extend the already successful and robust high pressure scientific field.

(2) Time-resolved in-situ synchrotron x-ray diffraction and spectroscopy under extreme conditions. Most studies of materials under extreme pressure conditions are static because it is very challenging to investigate materials in time-varying extreme environments. There is great interest in studying physical and chemical phenomena on time scales shorter than those relevant to material nucleation and growth, phase and electronic transitions, heat transport, atomic diffusion, and fast chemical reactions. These will require new ways of generating and using x-ray beams consisting of temporally short pulse x-ray pulses.

Many time-varying processes at high pressure are hidden because they occur on sub-nanosecond time scales. Single-shot experiments will benefit from the very short, ultra-intense pulses from x-ray free electron lasers, such as the LCLS at SLAC. However, many experiments require repetitive interrogation of single samples. ERLs and USRs have potential to deliver very high repetition rate x-ray pulses, ranging in duration from picoseconds to under 100 femtoseconds, into submicron-sized beams. When coupled with feasible pixel array detectors it should be possible to record successive snap shots, e.g., “movies” of x-ray signals from dynamically evolving systems. One can envision, for example, coupling trains of short x-ray pulses with rapid laser, temperature, pressure, strain rate or magnetic field variations to perform time-dependent x-ray diffraction and spectroscopy movies on single samples on time scales ranging from <100 fs to many seconds.

Time-resolved x-ray diffraction and spectroscopes promise to open new windows into the study of materials under extreme conditions. Many technical hurdles will have to be overcome, including the development of the x-ray sources and optics, fast detectors, and programmable control of laser and other excitation mechanisms and sample environments.

The premise of this workshop is that many of the hurdles will be overcome in the coming years, and that this process proceeds most usefully when guided by specific experimental goals. Thus, the workshop will be devoted to “brainstorming” and indentifying experiments that are now beyond the present edge of feasibility, but would be feasible by coupling new technologies with the tremendous capabilities of ERL and/or USR sources.

Workshop contributions: Presentations will focus on the issues of in-situ measurements by x-ray diffraction and spectroscopy of materials under extreme conditions of, e.g., pressure, temperature, strain rate, magnetic field, and others, and on the best ways to utilize ERLs or USRs for such experiments.

Method: The workshop will occur at Cornell’s Robert Purcell Center on June 23-24, 2011 and is open to anyone who may be interested. The workshop will start with a short overview of ERL and USR specifications and capabilities for frontier science with nanometer hard x-ray beams (see accompanying attachment for some ERL/USR background). The program, outlined below, will then continue with a core group of invited world-leaders to give short talks and lead the discussion in the relevant science areas. In order to allow time for discussion after each talk, speakers are asked to rigorously adhere to the 30 minute time limit. There will be ample additional time for open discussion and poster sessions. Workshop participants are especially encouraged to be inventive and explore unorthodox ideas.

Poster Session: There will be space to put up poster of up to 4’(height) x 6’(width) [1.2 x 1.8 meters]. If you plan to have a poster, please submit a ˝ page abstract to Laura Houghton at lab49@cornell.edu and she will try to compile them into the program. There is a specific poster session time shown in the program, but they can remain up for the entire duration of the workshop.

Workshop Results: Our goal is to communicate the possibilities for science with an ERL or USR, as well as with other sources, and engage the community in developing ideas for the science case. Imaginative thinking will be required -- that's why we are assembling this workshop group! Documenting the results of the workshop is essential. We hope to explore compelling science that is uniquely enabled by an ERL or USR. Accordingly, each invited participant will be asked to present at least one novel experiment of interest (described by a 1-3 paragraphs of text, an appropriate graphic, and relevant references) that would be very difficult to perform without the capabilities of an ERL or USR. Time will be provided towards the end of the workshop to summarize results and conclusions.

Of particular importance is the group discussion at the end of the meeting. It is therefore very important that all invited workshop attendees stay through to the end of the workshop. It is in this period that our discussion leaders will try to pull all the good ideas generated into a summary and we need your very active participation to do this well. As a motivator to stay through to the end and to further the development of “community” for this brief several day period, we have arranged a series of excursions. Depending on the workshop these include, for example, Cayuga Lake Boat dinner cruises, local winery tours, visits to Ithaca’s local spectacular gorge parks, etc.