**Research Activity: X-ray and Neutron Scattering**

Division: Materials Sciences and Engineering

Primary Contact(s): Helen M. Kerch (<Helen.Kerch@science.doe.gov>;
301-903-2346)

Team Leader: William Oosterhuis

Division Director: Patricia Dehmer, Acting

**Portfolio Description:**

This activity supports basic research in condensed matter and materials
physics using neutron and x-ray scattering capabilities primarily at
major BES-supported user facilities. Research is aimed at achieving a
fundamental understanding of the atomic, electronic, and magnetic
properties of materials and their relationship to the physical
properties of materials. Both ordered and disordered materials are of
interest as are strongly correlated electron systems, surface and
interface phenomena, and behavior under environmental variables such as
temperature, pressure, and magnetic field. Development of neutron and
x-ray instrumentation is a major component of the portfolio.

**Unique Aspects:**

The Department's history and mission has played an important role in
BES's current position as the Nation's steward of major neutron and
x-ray facilities. Historically, neutron sources descended from the
neutron reactors that were constructed in the early 1940s as part of the
U.S. Atomic Energy Program. Similarly, synchrotron facilities stemmed
from particle accelerators that were developed for high-energy physics
research. As part of its stewardship responsibilities, BES maintains
strong fundamental research programs in materials and related
disciplines that are carried out at these facilities by the laboratory,
university, and industrial communities. This activity has evolved from
the pioneering, Nobel prize-winning efforts in materials science to the
current program that encompasses multiple techniques and disciplines.
The activity also supports the research that has motivated the largest
BES construction projects in recent years - the ALS, APS, and SNS. BES
is a major supporter of both the research and the instrumentation at
these and other facilities.

Neutron and x-ray scattering are well-established techniques for
investigating the microscopic properties of materials. With the advent
of both high brightness x-ray beams produced by third generation
synchrotron radiation facilities and intense pulsed neutron beams
provided by accelerator-based neutron sources, a number of totally new
capabilities will become possible.

***Neutron Scattering.*** Neutron scattering provides information on the
positions, motions, and magnetic properties of solids. With unique
characteristics such as sensitivity to light elements, neutron
scattering has proven to be invaluable to polymer and biological
sciences. The high penetrating ability of neutrons allows property
measurements and nondestructive evaluation deep within a specimen.
Neutrons have magnetic moments and are thus uniquely sensitive probes of
magnetic interactions. The wavelength of neutrons used in scattering
experiments is commensurate with interatomic distances, and their energy
(meV) is comparable to both lattice and magnetic excitations (phonons
and magnons) making them an ideal probe for both structure and dynamics.

***X-ray Scattering.*** The unique properties of synchrotron radiation
-- high flux and brightness, tunability, polarizability, high spatial
and temporal coherence, along with the pulsed nature of the beam- afford
a wide variety of experimental techniques in diffraction and scattering,
spectroscopy and spectrochemical analysis, imaging, and dynamics.

**Relationship to Others:**

This activity interacts closely with neutron and x-ray scattering
research programs supported at other federal agencies, especially in the
funding of beamlines whose cost and complexity require multi-agency
support. The activity works in concert with the Instrumentation for
Materials Research Program (IMR) at the National Science Foundation and
the NIST Center for Neutron Research (NCNR) in the Department of
Commerce to develop instruments and capabilities that best serve the
national user facility needs of the nation. A coordinated effort between
the Department of Energy (DOE) and the National Science Foundation (NSF)
is ongoing to facilitate the full utilization of the SNS under the
auspices of the Office of Science and Technology Policy's Interagency
Working Group on Neutron Science. Interaction with ISIS and ILL in the
training of post-doctoral fellows and neutron detector development is
also underway. In FY2002, the program coordinated with the DOE's
SBIR/STTR Program which resulted in 4 Phase I and Phase II awards each
in the area of neutron detectors, monochromators and other scattering
instrumentation.

**Significant Accomplishments:**

***Neutron Scattering.*** This activity supported the research of
Clifford G. Shull at Oak Ridge National Laboratory that resulted in the
1994 Nobel Prize in Physics for the development of the neutron
diffraction technique. Shull's work launched the field of neutron
scattering, which has proven to be one of the most important techniques
for elucidating the structure and dynamics of solids and fluids. The
program supports major efforts in neutron scattering centered primarily
at the DOE laboratories- Ames, ANL, BNL, ORNL, LANL- and these groups
have pioneered virtually all the instruments and techniques in neutron
scattering, spectroscopy, and imaging.

***X-ray Scattering.*** As in the neutron scattering effort, the program
supports large research groups that utilize synchrotron radiation to
understand the intrinsic properties of materials. These groups have
contributed to the development of such powerful techniques as magnetic
x-ray scattering, inelastic x-ray scattering, extended x-ray absorption
fine structure (EXAFS), x-ray microscopy, microbeam diffraction,
time-resolved spectroscopy and others.

Recent accomplishments include first evidence via x-ray microdiffraction
of electromigration induced plastic deformation, development of COBRA-
coherent Bragg Rod Analysis for the direct determination of epitaxial
structures using x-rays, first light at HPCAT, development of a 3-D
x-ray structural microscope with submicron resolution, the observation
of zeolite expansion with pressure, and the discovery of
superconductivity in both simple systems (lithium) and exotic compounds
(Pu-based).

**Mission Relevance:**

To understand the physical properties of any material, one needs to
begin with its structure. The fundamental understanding of the structure
and behavior of matter contributes to the Nation's science base and
underpins DOE's broad energy and environmental mission and
responsibilities. X-ray and neutron scattering are the primary tools for
characterizing the atomic, electronic and magnetic structures and
excitations of materials. The increasing complexity of such
energy-relevant materials as superconductors, semiconductors, and
magnets requires ever more sophisticated, specific, and sensitive X-ray
and neutron scattering techniques to extract new and useful knowledge
and develop new theories for the behavior of new materials. The
scientific importance of x-ray and neutron science has been broadly
recognized as some 15 Nobel Prizes (14 in x-rays; 1 in neutrons) have
been based on research utilizing these tools.

**Scientific Challenges:**

[Programmatic Challenges]{.underline}:

***Neutron Scattering.*** The ongoing enhancements at the HFIR and the
LANSCE will not only increase the nation's neutron scattering capacity,
but, in many cases, will provide instruments with resolution and flux on
sample that is equal to or greater than existing benchmark instruments.
The SNS will push instrument capacity and performance even further. One
challenge for this activity will be to support an increased research
effort in neutron scattering to take full advantage of the improved
sources and to prepare for the SNS. Another includes maintaining the
strength of the DOE lab-based neutron scattering groups and rebuilding
strength in neutron sciences in the academic community. Education and
training of the next generation of neutron scientists - especially those
familiar with instrumentation and performance of TOF methods - remains a
high priority.

***X-ray scattering.*** Major instruments at the synchrotron light
sources have a lifetime of 7-10 years. Thus a challenge to the program
is to provide support for the 10-15% of the instruments which must be
upgraded or replaced each year to keep the facility at the forefront of
science.

[Scientific Challenges]{.underline}*:*

*Correlated Electron Systems:* The effects of strong electron-electron
interactions give rise to a remarkable range of anomalous behavior in
condensed matter systems, producing phenomena as varied as
metal-insulator transitions, colossal magnetoresistance, and high
temperature superconductivity in heavy fermion metals, insulators and
magnets. In particular, high-temperature superconductivity is a
singularly spectacular example of the cooperative macroscopic phenomena
such as the interplay of charge, spin, and lattice degrees of freedom
that can arise from correlated electron behavior. Techniques such as
inelastic x-ray scattering and neutron diffraction, among others, have
enabled scientists to unravel the crystallographic and microscopic
electronic structure of these materials, including stripes. This
information will ultimately be used to answer questions such as what is
the mechanism for superconductivity, how high can the temperature be for
materials to remain superconducting, and will that temperature ever be
room temperature.

*Matter Under Extreme Conditions*: Opportunities in high pressure
research address a broad range of new scientific problems involving
matter compressed to multimegabar pressures. Extreme pressures provide a
fertile ground for the formation of new materials and novel physical
phenomena as compression changes the chemical bonds and affinities of
otherwise familiar elements and compounds. Highly collimated and intense
synchrotron beams provide the ideal source for ultrafine and sensitive
x-ray diffraction microprobes necessary to measure concentrated high
stresses in a very small area. With the development of the SNS,
innovative focusing optics, more sensitive detectors and emerging
next-generation pressure cells, high pressure research at neutron
sources can approach the routine pressure ranges available with diamond
anvil cells at synchrotron x-ray sources. With the dramatic advances in
techniques for preparing and investigating single crystals, studies of
more complex materials become tractable. Similarly, scattering
experiment performed in the presence of magnetic fields can be used to
study materials during phase transitions (magnetic, structural,
superconducting) thus allowing researchers to segregate magnetic field
effects or to simulate effects normally observed via doping (for
example).

*In-situ Studies of Complex Materials:* Recent advances in both sources
and instrumentation have yielded gains in intensity on sample
facilitating rapid experiments and in-situ configurations. Smaller
samples can be probed with unprecedented resolution, accuracy, and
sensitivity under various parametric conditions. In-situ synchrotron
radiation techniques provide real-time observations of atomic
arrangements with high spatial sensitivity and precision, which are
important features in the development of novel processing techniques and
in the search for new exotic materials. In-situ studies of complex
materials including those undergoing time-dependent structural or
magnetic phase transformations, disordered systems such as alloys and
amorphous materials, organic thin films and self-assembled systems, and
other condensed matter systems can be probed with a variety of
scattering, reflectivity and spectroscopic techniques.

**Funding Summary:**

**Dollars in Thousands**

**[FY 2002]{.underline} [FY 2003 Request]{.underline} [FY 2004
Request]{.underline}**

35,032 54,277 54,277

> **[Performer]{.underline} [Funding Percentage]{.underline}**
>
> DOE Laboratories 72%
>
> Universities 28%

\*Includes \$12.3M for Enhanced Research Capabilities at DOE X-ray and
Neutron Facilities Initiative.

Major DOE laboratory performers include Ames, ANL, BNL, ORNL, LANL,
SSRL.

This activity also provides support for the construction of two
instruments at the SNS including the High-Resolution Chopper
Spectrometer (ARCS), P.I.: Brent Fultz/CalTech, and the Cold Neutron
Chopper Spectrometer, P.I.: Paul Sokol/Penn State. Also under
construction at the APS are the Inelastic X-ray Scattering Beamline,
P.I.: Clement Burns/Western Michigan, and the High Pressure Beamline,
P.I.: David Mao/Carnegie Institute of Washington.

**Projected Evolution:**

Advances in neutron and x-ray scattering will continue to be driven by
the scientific opportunities presented by improved source performance
and instrumentation optimized to take advantage of that performance. The
x-ray and neutron scattering activity will continue in fully developing
the capabilities at the DOE facilities by providing instrumentation and
research support. A continuing theme in the scattering program will be
the integration and support of materials preparation (especially single
crystals) as this is a core competency that is vital to US interests.