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Jan. 24, 2000 -- Some of
this week's stories:
 'ATTA'
can trap, detect single atoms in samples
David
Lewis to head CMT
WIST
committee seeks new member
Expert
can help 'Win the Paper Chase'
Retirement
vendors available for questions |
A new ultra-sensitive trace analysis technique -- able to detect single atoms in a large sample -- has been developed by researchers at Argonne.
Called Atom Trap Trace Analysis, or ATTA for short, the technology holds promise for advancing the state of the art in many fields, from solar-neutrino research to groundwater studies and environmental monitoring. This method was first announced in Science magazine Nov. 5, 1999.
The Argonne team, including Kevin Bailey (PHY), Chun-Yen Chen (PHY), Xu Du (PHY), Yimin Li (PHY), Zheng-Tian Lu (PHY), Tom O'Connor (PHY), and Linda Young (CHM), has been able to count individual atoms of krypton-85 and krypton-81 isotopes in a sample of natural krypton gas. Krypton-85 atoms have one more, and krypton-81 three fewer, neutrons than the common krypton-84 atoms. The two isotopes are extremely rare: in a natural sample of the gas, every krypton-81 atom is mixed in with a trillion krypton-84 atoms that are chemically similar.
One of the first applications for ATTA may be dating ancient Greenland ice cores. While carbon-14 dating has been used to date ice up to about 50,000 years old, ages of older samples have to be inferred from circumstantial evidence, such as its depth. Trace analysis of krypton-81, which lives 40 times longer than carbon-14, can be used to date samples up to one million years old.
Until this development, ultrasensitive techniques capable of detecting trace isotopes at the parts-per-trillion level have fallen into two categories.
"Low-level counting," pioneered by Nobel Laureate Willard Libby at the University of Chicago, essentially detects radiation from a sample as radioactive isotopes decay. This method requires lots of shielding from cosmic rays and other environmental activities that generate "noise" in the detectors, and in the case of long-lived isotopes, a lot of patience while the atoms decay.
In "accelerator mass spectrometry," or AMS, atoms from a sample are sent through a particle accelerator, stripped of their electrons, and have their mass measured in a sensitive detector. Pioneering work on radio-krypton dating of groundwater with AMS was recently conducted by an international team including Argonne physicists Philippe Collon (PHY) and Richard Pardo (PHY). However, this approach is difficult in practice because it requires access to large accelerator facilities.
In contrast, the ATTA technique uses a table-top laser to slow, trap and count atoms of interest. In the ATTA device, a trickle of krypton gas enters a source and is directed into a one-meter-long tube. There the krypton atoms run into a laser beam shining at them head-on, tuned to their "resonant frequency."
Atoms can be compared to springs, with the positively-charged nucleus at one end and the negatively charged electron on the other. If the oscillating electric field of photons in a laser beam matches the frequency of this "spring," electrons will be excited to higher energy levels, just like well-timed pushes will make a playground swing go higher.
The atoms then emit photons as the electrons drop back to their usual places. Following Newton's third law, the atom gets a kick when a photon is absorbed or emitted -- a krypton atom changes its velocity by about 6 millimeters per second with each kick. This absorption-emission process occurs millions of times per second, so with a modest laser beam, researchers can push atoms in any chosen direction, and slow the atoms from a pace of a jet plane to a mere crawl within an arm's length.
There is about a one part-per million difference in the "resonant frequencies" of the various isotopes of krypton. "We can tune our laser to the resonant frequency of krypton-81," said Lu. "When we do that, we only trap krypton-81."
At the end of the tube lies the trap, where six laser beams -- one from each horizontal direction, plus above and below -- hold the atoms in place. Atoms can be kept in the center of a trap for many seconds -- an eternity in a science that usually measures times in billionths of a second.
While in the trap, a krypton atom scatters millions of photons per second from the laser beams, and appears as a bright dot, visible to the naked eye. A photon detector records the arrival and departure of individual atoms. In the current experiment, one krypton-81 atom is detected every 15 minutes or so.
Many applications
Although the Argonne team has only worked with krypton atoms so far, ATTA should apply to some other isotopes for applications in a range of scientific disciplines.
One possibility is using lead-205 to shed light on the "solar neutrino problem," Lu said. Neutrinos are ghostly subatomic particles produced by thermonuclear reactions in the sun's core. They only rarely interact with matter and most pass unhindered through the earth. Physicists using huge underground neutrino detectors are finding fewer particles than expected of the type predicted by current theories of how the sun produces energy.
Neutrinos produced by the sun will convert a small number of atoms in rocks to lead-205, an extremely long-lived isotope. Ancient, deeply buried rocks are shielded from cosmic rays that would produce spurious results.
By measuring the amount of lead-205 in these ancient rocks, scientists may be able to get an accurate measure of the sun's past activity. If more neutrinos were produced in the distant past, it may signal that the sun's core is currently in a relatively dormant phase, accounting for the dearth of neutrinos.
Another potential application is using calcium-41 as a medical tracer to monitor bone loss from osteoporosis. With the powerful detection abilities of ATTA, a patient can ingest just a small, non-harmful amount of the isotope, which would be taken up into the bones. Over the following years, ATTA could be used to detect minuscule amounts of calcium-41 in urine samples, which would signal the loss of calcium from bones. This method would give medical doctors a powerful new tool to diagnose and test treatments for the condition.
ATTA may also find use as an extremely sensitive leak sensor and environmental monitor at U.S. Department of Energy "legacy waste" cleanup projects. Besides krypton-85, some other fission-produced isotopes of strontium and cesium can be detected with ATTA at an unprecedented sensitivity.
-- Dave Jacqué
David Lewis has been appointed director of the Chemical Technology Division, one of Argonne's largest divisions and a leading center for research and development related to energy and environmental issues.
CMT conducts research and development on methods for disposing of radioactive and hazardous wastes and energy conversion processes, while improving efficiency, lowering costs, and reducing environmental impact.
Lewis has extensive management background in high technology development programs, including strategic planning, personnel management, team building, market development, and manufacturing startup.
He joined Amoco Corporation in Naperville in 1970, and was named Amoco's first corporate fellow. Lewis planned and initiated the company's corporate physical sciences research, which led to the formation of the Amoco Technology Company.
Lewis has studied catalysts used in petroleum processing, analyzed petroleum components and contributed to the understanding of stability in lubricating oils.
In 1984, Lewis was named manager of Amoco's Physical Technology Division, a 106-person, $16-million a year research department involved with integrated materials, lasers and optoelectronics. He was responsible for intellectual property management, including patents, publications and the transfer of technology between the central organization and the Amoco operating units.
Lewis left Amoco in 1994 to form his own management consulting and technology implementation company, providing advice to large corporations and small, technical start-up companies.
Argonne's Women in Science and Technology (WIST) steering committee has an opening for one representative from the laboratory's staff of women technical employees.
The group's charter includes recommending a WIST program initiator to lead the laboratory's efforts to recruit, retain and promote women. The committee also provides guidance during the initiator's two-year term and evaluates the WIST program's effectiveness.
Any interested regular, full-time employees should provide a curriculum vitae and cover memo listing prior experience with WIST activities and stating reasons for wanting to become a committee member.
This material should be sent to committee chairman Joe Asbury (OTD) by Friday, Feb. 4.
Members about to rotate off the committee and former members may apply for consideration.
Eileen Roth, nationally recognized organizational consultant and president of Everything in Its Place, will help employees get organized for the new millennium with two seminars at Argonne-East.
Win the Paper Chase (HR400) will help participants
set up a classification and label system to
achieve fingertip file management, saving time and
increasing productivity. Thursday, Jan. 27, 1 p.m.
- 5 p.m., Building 201, Room 190.
Desk for Success (HR401) is the companion class to
Win the Paper Chase. The course presents a proven
approach to regaining control of one's desk and
office. Participants learn six principles for
organizing their desktops, how to create an action
file, sort mail rapidly and create a personal
reference book. Thursday, Feb. 3, 1 p.m. - 5 p.m.,
Building 201, Room 190.
Both classes are sponsored by Human Resources. To enroll, contact a Training Management System representative.
For more information on these classes, call Betty Iwan (HR) ext. 2-3410.
Representatives of the laboratory's retirement vendors will be available during February to meet individually with Argonne-East employees and answer questions about retirement plans and retirement plan assets.
To schedule an appointment, call the number listed. Prudential appointments are for one-half hour each.
| Vendor | Day | For Appointments, call: |
| Prudential | Wednesday, Feb. 2, 9, and 16 | (847) 619-3519 |
| Fidelity | Tuesday, Feb. 8 and 15 | (800) 642-7131 |
| TIAA-CREF | Monday, Feb. 14 and Tuesday, Feb. 15 | (800) 842-2005 |
William A. Carswell, a retired stock handler with 18 years of service in Accelerator Systems, died Nov. 10. He is survived by his niece Althen Solomon.
Jessie P. Craig, a retired finisher I with 29 years of service in Media Services, died Oct. 18. She is survived by her husband Oliver and daughter.
Peter V. Dauzvardis, a retired engineering specialist with 35 years of service in Engineering Research Program, died Sept. 24. He is survived by his children.
Thomas Erickson, a retired technician senior with 31 years of service in Materials Science, died Oct. 21. He is survived by his wife Eleanore.
Joseph C. Florek, a retired technician senior with 29 years of service in Materials Science, died Nov. 6. He is survived by his wife Blanche.
Elmer R. Gunchin, a retired technician with 34 years of service in Reactor Analysis, died Sept. 28. His wife Helen and children survive him.
Thomas H. Hall, a retired line manager senior with 33 years of service in Plant Facility and Services, died Sept. 21. His wife Eleanor and children survive him.
Robert H. Land, a retired physicist with 31 years of service in Chemical Technology, died Oct. 6. He is survived by his nephew Alan Bloch.
Leroy P. Peterson, a retired instrument machinist with 27 years of service in Central Shops, died Oct. 27. His daughters survive him.
Charles A. Seils, a retired scientific associate with 40 years of service in Chemical Technology, died Oct. 18. He is survived by his wife, Laureen, his son, Carl, his daughter, Karen and his granddaughter, Kathryn.
Prince Walker, a retired staff assistant senior with 34 years of service, died Oct. 27. He is survived by his daughter, Karen Walker.
