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Physics
NIST/CU Scientists
First to Observe New Quantum Gas
Researchers
at JILA, a joint research
institute of NIST and the University of Colorado at Boulder, reported
in the Sept. 10, 1999, Science that they have achieved
the first Fermi degenerate gas of atoms.
Similar
to experiments in 1995 that first created a new state of matter—the
Bose-Einstein condensation—the
NIST-led group at JILA cooled a gas of potassium atoms to ultralow
temperatures where the quantum (most basic) nature of gas is dominant
(reaching a state known as “quantum degeneracy”).
However,
while the B-E experiments used one class of quantum particles
known as bosons, the JILA group cooled atoms that are fermions,
the other class of quantum particles found in nature. Using laser
cooling and magnetic confinement, they cooled about a million
potassium atoms to temperatures less than one-third of a millionth
of a degree above absolute zero.
When
gas is cooled to near absolute zero, each atom stops behaving
as a point-like particle and instead behaves like a wave, with
the wavelength of each atom overlapping those of neighboring atoms.
When bosonic atoms reach this regime, they all fall in step with
each other, resulting in a B-E condensate or “super-atom.” As
the JILA group cooled fermionic atoms to quantum degeneracy, they
found instead—as predicted—that the atoms began to avoid each
other, resulting in an “excess” energy in the gas.
Study
of the Fermi degenerate gas will increase our knowledge about
and understanding of fermions, which are important throughout
physics since the basic building blocks of matter—electrons, protons
and neutrons—are all fermions. In addition, the unique properties
of the fermionic atoms could be exploited for improving atomic
clock technology. Future work also will explore the possibility
of achieving a fermionic superfluid state in the gas, which ultimately
could shed light on the physics of superconductivity.
Authors
of the Science paper are NIST physicist Deborah Jin and
CU-Boulder graduate student Brian DeMarco.
Media
Contact:
Collier Smith (Boulder),
(303) 497-3198 
Electricity
A Capacitance
Standard by Tallying Electrons? You Can Count on It!
NIST
researchers announced in the Sept. 10, 1999, issue of Science
magazine that they have developed the first working prototype
of a new standard for measuring the storage of electrical energy—known
as capacitance—based on a means of manipulating and counting electrons
one at a time.
The
new standard is the latest to rely on a fundamental property of
nature and not be determined by a constructed artifact, classical
physics or a combination of both. Nature-based standards currently
in use include length (the meter) and time (the second), both
defined by precise measurements of the vibrations of the cesium
atom.
The
work on the capacitance standard depends on two technologies developed
at NIST. The first is an electron pump, based on ultra-small electrical
devices called tunnel junctions. Operating at temperatures less
than one-tenth of a degree above absolute zero, the pump passes
and counts individual electrons with an uncertainty of 0.01 parts
per million. In other words, the pump would miss tallying only
one electron in every 100 million passing through.
The
second NIST-developed technology is a cryogenic, vacuum-gap capacitor.
The capacitor is designed so that very few of the electrons placed
upon it “leak out,” dramatically improving the accuracy of the
capacitance measurement. In addition, it does not contain the
dielectric materials (which are good but imperfect electrical
insulators) that lessen the effectiveness of ordinary capacitors.
The
capacitance measurement is made after the cryogenic pump places
about 100 million electrons on the capacitor. The resulting voltage
generated across the capacitor is determined, and the capacitance
is then calculated as the ratio of pumped charge to measured voltage.
NIST’s
present primary capacitance standard has been measured to an uncertainty
level of 0.01 parts per million. Although very accurate, the measurement
requires complex calculations, takes months to complete and is
best done at a national measurement laboratory such as NIST. The
system for the prototype standard, the researchers believe, will
be simpler to use, should make measurements faster and could be
set up at any site with the necessary equipment.
For
technical information, contact Mark
W. Keller (Boulder, Colo.), (303) 497-5430; or Neil
Zimmerman (Gaithersburg, Md.), (301) 975-5887.
Media
Contact:
Fred McGehan (Boulder),
(303) 497-3246
Michael
E. Newman, (301) 975-3025
Manufacturing
President
Honors Small Manufacturers with Special Week
President
Clinton declared the week
of Sept. 19-25, 1999, as Small Manufacturing Week, saying,
“Let us pay tribute to America’s more than 385,000 small manufacturing
firms whose unfailing commitment to hard work and excellence has
helped set our country on a steady course for continued growth
and prosperity.”
Earlier
this year, Commerce Secretary William Daley declared 1999 as the
Year of the Small Manufacturer. In addition, the National Governors’
Association passed a resolution in support of the year and 12
states have issued proclamations recognizing small manufacturers.
During
Small Manufacturing Week on Sept. 21 and 22, hundreds of small
manufacturers, policy makers, leaders in industry and academia,
and others will convene at a National Manufacturing Summit in
Washington, D.C., to recognize and honor small manufacturers.
The attendees will discuss ways to improve the performance of
small manufacturers in four key areas: supplier relationships,
e-commerce, workforce and international trade.
As
part of the summit, an exhibit of more than 200 products made
by small manufacturers from every state, the District of Columbia
and Puerto Rico will be displayed. The summit is sponsored by
the NIST Manufacturing Extension Partnership, the National Association
of Manufacturers and the Modernization Forum.
For
further information, see www.mep.nist.gov
on the World Wide Web.
Media
Contact:
Jan Kosko, (301)
975-2767
Chemistry
Trace Gas
Method Boosts Sensitivity
Bigger
isn’t always better. A team of NIST chemists recently proved this
is true for trace gas measurements of water vapor or oxygen. The
team found they could make measurements of gas concentrations
that are 100 times more sensitive with a testing chamber that
is one-tenth the size of previous models.
The
semiconductor industry has rigorous requirements for the purity
of gases used in the fabrication of integrated circuits. One way
to test for impurities such as water vapor or oxygen is a technique
known as cavity ring-down spectroscopy. The conventional implementation
of this technique involves putting a sample of the gas to be tested
into a chamber about one meter long and shining an infrared laser
into the enclosure. The infrared light bounces back and forth
between two mirrors at the ends of the chamber. The laser light
is tuned to a wavelength that is absorbed by the molecule to be
detected. By measuring the rate that light leaks from the chamber,
scientists can determine the concentration of the contaminant.
Conventional
wisdom has held that longer chambers should provide better sensitivity.
Longer chambers leak light at a slower rate, so small changes
in light levels should be easier to detect. However, the NIST
group observed that light wave interactions within meter-long
chambers compli-cated the detected signals.
To
eliminate these interactions, the NIST researchers used a pulsed
laser and made a chamber only 10 centimeters long. They found
that tiny changes in the distance between the two mirrors in the
chamber generated distinct wave patterns.
By
carefully controlling the laser wavelength and cavity length to
produce the simplest pattern, the unwanted interactions were eliminated
and sensitivity of the method was enhanced greatly.
For
technical information, contact Roger
van Zee, (301) 975-2363.
Media
Contact:
Linda Joy, (301)
975-4403
Trade
NIST Center
Distributes Draft Technical Regulations
Draft
technical regulations concerning toys, electrical appliances,
chemicals, dyes and telecommunications equipment topped the list
of inquiries that NIST fielded last year in its role as the U.S.
inquiry point for questions on proposed domestic and foreign rules
that may affect international trade.
Under
the World Trade Organization’s Agreement on Technical Barriers
to Trade, governments of the international body’s 133 member countries
are required to notify the WTO of prospective regulatory measures
that may pose obstacles to market entry. The WTO, in turn, makes
these one-page notifications available to NIST’s National Center
for Standards and Certification Information and to other inquiry
points around the globe. NCSCI and its counterparts distribute
the notifications to domestic industrial organizations, government
agencies and other groups to encourage review and comment. NCSCI
also provides full-text copies of the draft regulations.
To
allow for adequate review, NCSCI explains in its newly issued
annual report, the WTO recommends a comment period of at least
60 days. In 1998, the average was 36 days for the 615 notifications
issued by 39 WTO members. At 89, the Netherlands issued the largest
number, followed by Belgium (49), Israel (46) and Brazil (43).
Twelve U.S. agencies notified the WTO of a total of 33 proposed
regulations in areas ranging from children’s sleepwear to spark
ignition engines. The comment period for these proposals averaged
49 days.
In
1998, NCSCI staff responded to 240 inquiries on U.S. and foreign
proposed regulations. The NIST center also provides translation
services and transmits U.S. industry comments on proposed regulations
to foreign governments. The center offers a WTO Hotline, which
provides a recorded summary of the latest notifications of proposed
foreign regulations. The number is (301) 975-4041.
For
more information on NCSCI and its responsibilities under the TBT
Agreement, contact JoAnne
Overman, Standards Information Program, (301) 975-4037. To
get a copy of NCSCI’s annual report on TBT Agreement activities,
contact NCSCI, (301) 975-4040, ncsci@nist.gov.
Media
Contact:
Mark Bello, (301)
975-3776
Editor:
Michael Newman
HTML conversion: Crissy
Wines
Last updated: September 13, 1999
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