PHYSICS NEWS UPDATE
The American Institute of Physics Bulletin of Physics News
Number 647  July 23, 2003   by Phillip F. Schewe, Ben Stein, and
James Riordon

THE PROTON HAS A DIFFERENT SIZE IN DIFFERENT NUCLEI.   The electron,
which is mostly impervious to the nuclear forces, can penetrate deep
inside a nucleus.  Therefore, scattering high energy electrons from
a nucleus is an excellent way of exploring the electric and magnetic
properties of the nucleus as a whole and of its constituent protons
and neutrons, especially when the electron transfers some of its
spin to a proton in a telltale way.  For example, recent results
from such an experiment, conducted at the Jefferson Lab, gave
evidence that the proton is not necessarily spherical.  Now a new
experiment at Jlab, comparing electrons scattering from single
protons (a hydrogen nucleus) with electron scattering from helium
nuclei, suggests that each nucleus "kneads" its protons in a
different way (see figure at www.aip.org/mgr/png/2003/197.htm ).
The kneading allows the constituent quarks inside the proton to
spread out a bit at time, perhaps into a peanut shape, even though
its average shape is round.  (Strauch et al., Physical Review
Letters, upcoming article)

NMR WITHOUT THE MAGNET OR RF COILS.  To image an object's interior
with nuclear magnetic resonance (NMR) a magnetic field of several
tesla (1 T =10,000 gauss) is usually required to polarize protons in
the sample and then radio waves are used to tip the protons and to
detect a weak signal as they upright themselves again.  The strength
of the signal depends on the size of the magnetic field and the
degree of polarization, which is often only one part in 10^5, and
somewhat limits the use of NMR (including its medical application,
MRI) because of the need for a bulky, expensive magnet.  One way of
improving things is to use laser light to produce a polarization as
high as 10% in a gas of xenon atoms.  The Xe atoms can then be
injected into an empty space, such as lungs, and used to image their
interior, which couldn't be done using conventional NMR (see Update
398, http://www.aip.org/enews/physnews/1998/split/pnu398-1.htm ).
Another NMR advance has been the use of ultrasensitive SQUID
detectors for picking up the magnetic fields produced by protons,
greatly reducing the need for large magnets (see Update 528,
http://www.aip.org/enews/physnews/2002/split/582-1.html ) but at the
expense of weak signals, with a proton polarization of only one part
in 10^8.
Now, Princeton physicist Michael Romalis and co-workers, while
studying whether the Xe nucleus is slightly nonspherical (equivalent
to saying that the nucleus possesses a nonzero electric dipole
moment, which would imply the existence of "new physics" beyond the
Standard Model), have worked out a way to combine different
techniques to obtain a strong NMR signal in a very weak 1
micro-tesla magnetic field. They transfer polarization from
laser-polarized Xe to protons in an organic liquid and then use
SQUID detectors to measure the magnetic field produced by the
polarized protons. Romalis (romalis{at}princeton.edu, 609-258-5586)
expects that this low-field NMR technique would work for any
sample---whether liquid, surface, or biological tissue---with good
solubility for xenon.  (Heckman et al., Physical Review Letters,
upcoming article; see also website atomic.princeton.edu/romalis )

MILLING DIAMOND FILMS can be performed with gallium beams.  Diamond
films, created by first installing tiny diamonds in a pitted silicon
surface and then laying down subsequent atoms to form a near-planar
diamond surface, have many of the electrical properties of
semiconductors, but can operate at much higher temperatures,
voltages, and power.  Because of its resistance to hostile
environments and its bio-compatibility, diamond films are also
expected to be act as handy protective coatings in microfluidic
research   Because of its hardness, however, diamond films are
difficult to sculpt through micromachining, during which stresses on
the sample can crack the film.  Now scientists at the Nanyang
Technological University in Singapore have devised a versatile way
of making possible micro-optical elements out of diamond films by
wielding a carefully focused gallium ion beam.  Optical tests of the
resultant structures show that such properties as transmission and
index of refraction were not distorted by the milling process. By
the way, this research was undertaken as part of the Singapore-MIT
Alliance, an innovative engineering education and research
collaboration established in 1998 among three top engineering
research universities: National University of Singapore (NUS),
Nanyang Technological University (NTU), and Massachusetts Institute
of Technology (MIT). (Fu et al., Review of Scientific Instruments,
August 2003; contact Yongqi
Fu, yqfu{at}ntu.edu.sg )

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PHYSICS NEWS UPDATE is a digest of physics news items arising
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