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March 20, 2000 -- Some of this week's stories:
Argonne physicists test supernova theories
ISM mugs are ready for pickup
Argonne-East to host Toastmasters area contest
Softball league needs teams, players, umps
Applications accepted for MBA program
AEGL league seeks golfers

Argonne physicists test supernova theories

In 1054, Chinese astronomers noted a brilliant new star appearing in the eastern sky. The "guest star" was visible for weeks, even during the day. Almost a thousand years later, the Crab Nebula marks the spot where a giant star blew itself to shreds in a supernova explosion.

The Crab Nebula is bright enough to spot in a small backyard telescope, but astronomers suspect many more supernova remnants lie in the center of our Milky Way galaxy, where only gamma rays can penetrate intervening clouds of dust and gas and reveal their presence. In an attempt to find them, an international effort will send the European Space Agency's "Integral" orbiting gamma-ray telescope aloft in 2001. How far into our galaxy it will be able to detect supernova remnants hinges on an exotic material called titanium-44 and recent research conducted at Argonne.

'Freeze-out' at 4 billion degrees

A supernova occurs when a very large star uses up all its fuel and suddenly blows off most of its matter, radiating more energy than a billion suns for a short time(see sidebar story).

In the millions of years before its final flash of glory, the star cooks up all of the elements from helium to iron. The supernova creates many elements heavier than iron and blasts them all out into the universe, where they may later condense to form planets -- and the ingredients of life.

In the supernova's multi-billion-degree inferno, much of the store of lighter elements built up by the star over millions of years are "melted" into alpha particles, clusters of two protons and two neutrons. As the supernova expands and cools, the alpha particles begin coalescing to form heavier elements, including titanium-44.

This form of titanium has 22 neutrons, as opposed to the 24 in the atoms of the nearest stable titanium isotope (like those in the titanium oxide in white interior house paint, for example). Titanium-44 has a half-life of 60 years -- in that time half of the atoms in a sample will decay into calcium-44 and emit gamma rays, a high-frequency form of light, with exactly 1.157 million electron-volts of energy.

"That energy is a fingerprint of this particular isotope," said Ernst Rehm (PHY). "If you find a source of gamma rays in the sky at 1.157 MeV, you're looking at a young supernova remnant."

Limited by the sensitivity of present orbiting gamma-ray detectors, astronomers have so far found only two gamma-ray-emitting supernova remnants.

The amount of titanium-44 produced in a supernova is governed by a subtle interplay between the reactions that produce it and those that destroy it, Rehm said.

"A whole network of reactions is occurring," he said. "About 95 percent of these reactions have been calculated, but never experimentally measured."

Rehm and his team decided to focus their experiment on a reaction predicted to be the biggest destroyer of titanium-44, a reaction that would limit the amount produced in a supernova explosion. In this reaction, a nucleus of titanium-44 absorbs an alpha particle and releases a proton, to form vanadium-47. It was the first time this reaction was ever experimentally measured.

Team effort

The titanium-44 was produced at Argonne's Intense Pulsed Neutron Source, a process overseen by Frank Brumwell and Gerald McMichael (both IPNS). A sample of scandium was bombarded with protons for three days to produce 1.3 millionths of a gram of titanium-44.

"The first test samples ended up as a puddle of molten metal," Rehm said, due to the intensity of the proton beam. John Greene and Bruce Zabransky (both PHY) designed a sophisticated liquid-cooled sample holder that prevented the sample from melting under the intense proton beam.

The sample was then sent to Argonne's Analytical Chemistry Group, where chemist Del Bowers (CMT) dissolved and precipitated the microscopic amount of titanium-44 from the surrounding scandium. The 10 quadrillion atoms of titanium-44 were mixed with titanium oxide, packed into a bullet-sized sample case and transported to Building 203, which contains the Argonne Tandem Linac Accelerator System (ATLAS).

Simulating the alpha-particle environment inside the supernova explosion required a target made of helium gas (alpha particles are helium nuclei). The gas, confined behind metal foil, was cooled to liquid nitrogen temperatures to make it a denser target and prevent overheating. Zabransky designed the target.

The sample was loaded into the ATLAS ion source and titanium-44 ions fired at the gas cell target. Behind the target lay the Fragment Mass Analyzer, a sensitive detector that captured the reaction products and detected the vanadium-47 produced in the reactions.

Good news, bad news

Argonne research associate A. A. Sonzogni did much of the analysis of the experimental results, which showed the alpha-capture process agreed with predictions at higher energies. However, at the critical lower energies, the titanium-destroying process turned out to be a good deal more efficient than expected. Supernovas, it turns out, probably produce about 25 percent less titanium-44 than previously thought.

The good news: the experiment refined the knowledge of an important astrophysical process.

The bad news: The Integral satellite may see fewer supernova remnants than had been hoped.

The lower amount of titanium means that supernova remnants aren't as bright in gamma-ray light. This knocks about 12 percent off the distance at which the satellite will be able to detect an object. It also means Integral will miss older objects in which the titanium-44 has decayed to undetectability.

Argonne's study of this reaction will be taken into account as new spaceborne gamma-ray telescopes are designed.

-- Dave Jacqué

Death agonies of huge stars
create elements of planets

The sunshine that makes a spring day so enjoyable begins its life deep in the heart of the sun, where huge pressures and temperatures force hydrogen nuclei to fuse, forming helium nuclei. The fusion process releases large amounts of energy. The outward radiation pressure of this ongoing thermonuclear reaction supports the star's outer layers.

When a star uses up its supply of hydrogen, it begins to fuse helium into carbon, carbon into neon, and so on up the periodic table. These elements build up until the interior of the star resembles an onion, with layers of progressively lighter elements.

This process continues until the star tries to fuse silicon and sulfur into iron. But as the iron builds up, the process begins to break down because converting iron into cobalt consumes energy. The process abruptly stops, and the star, unable to support itself any more, collapses in a heap.

The star's outer layers drop into the star's core at an appreciable fraction of the speed of light, hammering the core into a solid ball of neutrons. The outer-layer materials rebound from this ultimately solid object, and with a massive shove from behind by a blast of neutrinos, explode outward into the universe.

The ejected material contains all the elements built up over millions of years by the original star, and much heavier elements synthesized by the ten-billion-degree blast. For a few days, the explosion can blaze brighter than the entire galaxy in which the star once shone.

Over the eons, these elements drift through the cosmos, and some find their way into nearby star-forming regions. The elements join condensing disks of gas that form new solar systems. Supernovae that occurred eons ago are the source of the carbon in our bodies, the gold in our tooth fillings, and the calcium ions that transmit the complex nervous signals that create consciousness.

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ISM mugs are ready for pickup

All employees who won Integrated Safety Management coffee mugs can pick up their prizes at Building 202, Room E125, during regular business hours.

Argonne-West winners will receive their mugs this week.

Employees who answered a short quiz on Integrated Safety Management in each special issue of ESH Focus were awarded the prize.

Final winners

The final winners of the Integrated Safety Management mug contest are:


John Ahrens RA
Dorthy Andrews PFS
Valerie Bell ESH
Kurt Boerste AOD
Barbara Burke ECT
Debbie Busch ER
Glenn Cain PFS-SS
Dick Combs ITD
Mary Fremarek IPD
Jeff Gaffney ER
Paul Ganz PFS-US
Elizabeth Gardner CMT

Jeff Goetzen APS
Patty Gutzeit OP
Jenny Hill OCF-BUD
Andy Jansen CMT
Mark Kamiya ESH
Lindy Keller BIO
Jim Klick AOD
Don Le Buis BIO
Qing'an Li MSD
Jay Liaw TD
Beverly Malak ET
Pam Malhotra ET


Dan McNamee PFS
Nazarali Merchant CMT
Ali Nassiri ASD
Rob Piorkowski ESH
Kalimullah RA
Jim Regis RE
Laura Reigle ASD
Lillian Ruscic CMT Suntharalingam
Skanthakumar CHM
Leland Sprouse ESH
Sherry Strahla HR
Virginia Strezo CMT
Jug A. Uppal PFS-FEC

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Argonne-East to host Toastmasters area contest

The laboratory's Toastmasters Club will host the Southwest 3 Area speech contests at Argonne-East Friday, March 24. All employees are invited to hear the presentations and learn more about Toastmasters.

The competition will be held at 7 p.m. in the Advanced Photon Source Conference Center Auditorium, Building 402. Argonne will be represented by:

Miriam Bretscher (ECT), competing in the "table topics" speech contest in which the speaker responds to an unannounced topic.

Jill Morgenthaler (ECT), selected for colonel in the U.S. Army Reserves, will speak about her experience in Bosnia in the international speech (motivational) competition.

The club meets the second and fourth Wednesdays of each month from noon to 1 p.m. in Building 201, Room 190A. The next meeting will be March 22.

For more information, call Betty Iwan (HR) at ext. 2-3410.

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Softball league needs teams, players, umps

Argonne's 16-inch softball league is looking for players, teams and umpires for the upcoming 2000 season, which begins Wednesday, May 10, at Argonne Park.

The mixed leagues are sponsored by the Argonne Club, and games are Wednesday or Thursday evenings at 5:30 p.m. The season usually runs through August, depending on the game schedule.

There were nine teams last year; each team can have up to 25 players on its rooster, providing plenty of room for new and returning players.

For more information, contact league president Jack Burke: page ext. 4-7296, or send e-mail to burke@aps.anl.gov.

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Applications accepted for MBA program

Applications are now being accepted for the 2000 University of Chicago Executive Master of Business Administration Program.

This year Argonne management will select one employee to participate in this high-caliber program offered through the university's Graduate School of Business.

The program is designed for middle- and upper-level managers who are expected to retain full job responsibilities while attending classes in advanced studies in management every other Friday and Saturday beginning in July. The entire program spans twenty months.

Applications are available online or by calling Human Resources at ext. 2-3410. The deadline for returning completed applications to Human Resources is Monday, April 17.

Call John Hyzer, (HR) at ext. 2-3410 for more information.

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AEGL league seeks golfers

The Argonne Engineering Golf League wants golfers for the 2000 season.

The league plays Wednesday afternoons, teeing off between 4 p.m. - 4:30 p.m. at Carriage Greens Golf Course in Darien.

For more information, see the league's Web page, or contact one of the league's officers:

Jeff Goetzen (ASD), ext. 2-9608 or goetzen@aps.anl.gov.

Marge Collins (HR), ext. 2-3013 or mcollins@anl.gov.

Frank Rotella (BIO), ext. 2-3830 or fjrotella@anl.gov.

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Tax seminar to be held March 22

"Tax Strategies For the Year 2000," a seminar presented by Ken Small of Retirement Advisers, will be held in Argonne-East's Building 362 Auditorium Wednesday, March 22, from noon to 1 p.m.

Student research program applications due

Applications for the summer research participation program for college-bound students are due by Friday, March 31.

Students can participate in laboratory research under the direction of Argonne-East scientists in the eight-week summer program, conducted by the Division of Educational Programs.

Students must have a grade point average of at least 3.0 on a four-point scale, be U.S. citizens or permanent resident aliens, graduated from high school in May or June 2000 and enrolled to attend college in fall 2000.

Participants receive a stipend of $300 per week. The program begins June 12 and ends Aug. 4.

Applications are available from Lisa Reed (DEP) at ext. 2-3366, or send e-mail to lreed@dep.anl.gov.

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