Eliminating Parasitic Slit Scattering in Small Angle Xray Diffractometers

1
Eliminating Parasitic Slit Scattering in Small
Angle X-ray Diffractometers Cyrus R. Safinya,
UC Santa Barbara, DMR 0619171
Our instrumentation development effort has led to
a new hybrid design of x-ray aperture slits,
which has been demonstrated to almost completely
eliminate the detrimental parasitic slit
scatterings in small angle x-ray scattering
(SAXS) instruments. Parasitic slit scattering is
one of the most difficult-to-overcome
resolution-limiting factors in current SAXS
instrument design. The simple, yet effective
hybrid slit design combines a highly polished
single crystalline (Si) slit edge bonded to a
Tungsten base (inset in C). By using a polished
(1 0 0) Si slit edge that generates no SAXS
signal, most of the parasitic slit scattering due
to the polycrystallinity of the slit material
can be eliminated, as shown in the experimental
data (A, B, C) collected and analyzed by our 2007
summer RISE (Research In Science and Engineering)
intern Thomas Huang (Grinnell College, Iowa)
mentored by Co-PI Y. Li (UCSB MRL Summer RISE
Intern Report, 2007)
A
B
This broadly applicable design concept represents
a very cost-effective way to significantly
upgrade the performance of a large number of
existing and future SAXS instruments, which are
essential tools used widely for nanoscale
characterization in broad areas of research.
Figure (A, B) Slit scattering images from a
traditional Tungsten slit (A) and a Si-W hybrid
slit (B). The intensity profiles (C) across the
beam stop (centered at X0) show the dramatic
reduction of parasitic scattering to the
background level with the hybrid Si-W slit (inset)
2
MRI Development of an Ultra-High Resolution
Small Angle X-Ray Scattering Instrument for
Characterizing Supramolecular Assemblies Cyrus
R. Safinya, UC Santa Barbara, DMR-0619171
Education Multidisciplinary teams comprised of
undergraduate and graduate students, and
postdocs, with backgrounds in materials, physics
and engineering, are educated in x-ray
instrumentation science and SAXS methods for
nanoscale characterization of supramolecular
assemblies. These skills are essential to
successful careers in a broad range of areas
including nanoscience and nanotechnology, polymer
physics and chemistry, chemical and biomedical
engineering.
Outreach The PIs actively participate in
multiple outreach programs at UCSB for
undergraduate and high school teacher research
internships. Thomas (Tuo) Huang (Top photo,
presenting at UCSB summer research interns
conference), a MRL RISE Intern (2007) from
Grinnell College, Iowa, worked directly with
mentor and Co-PI Dr. Youli Li to develop the
scatter-free hybrid x-ray slit (see research
highlights). Thomas worked closely with UCSB
mechanical engineering undergraduate students
Nicholas Judy (bottom photo, left), Eric Walsh,
and staff research associate Morito Divinagracia
(bottom photo, right), who are actively working
on the MRI project together with other graduate
students and postdoctoral researchers.