Fermi National Laboratory

Volume 22  |  Friday, May 14, 1999  |  Number 10
In This Issue  |  FermiNews Main Page

The Talk of the Lab

Watch this space

Everyone who is anyone in the bustling field of particle astrophysics will be at Fermilab at the end of May for "Inner Space/Outer Space II," a symposium that will thoroughly explore, if not settle, such persistent questions as "Did the universe have a beginning?" and "How rare do you like your buffalo?" The four-day symposium, from May 26-29, will feature the early universe (How early? "Ridiculously early," according to symposium co-chair Rocky Kolb), a "major policy address" by NASA Director Dan Goldin, the latest on the cosmic hunt for that pesky missing energy, a buffalo banquet, an all-out confrontation between two eminent cosmologists about the beginning (or not) of the universe, and much, much more.

The Inner Space of the symposium’s title refers to the friendly confines of the subatomic world so familiar to particle physicists. Outer Space takes in the territory occupied by nature’s great particle accelerator in the sky, the source of the highest-energy particles ever; not to mention black holes; supernovae; dark matter; the cosmological constant—and everything else.

Inner Space/Outer Space II is aptly dedicated to the memory of David N. Schramm, the late University of Chicago astrophysicist who was among the earliest scientists to recognize that astrophysics and particle physics are two different ways of exploring the same fundamental questions about the nature and origin of the universe. Schramm was an articulate and energetic exponent of the view that the exploration of nature on the very smallest and the very largest scales in fact converge. His career at the frontiers of particle astrophysics was cut short when he died in a plane crash in 1997.

"The universe was in some sense an elementary particle physics laboratory," wrote Schramm and particle physicist Leon Lederman in From Quarks to the Cosmos, their 1989 book on the subject. "In fact the physics governing what was going on in the early universe is the physics of elementary particles."

There’s a whole lot of particle physics going on in today’s universe as well, according to Kolb and symposium co-chairs Josh Frieman and Mike Turner. There’s certainly a lot of it going on in the program they have planned, as a look at the Inner Space/Outer Space II Web page (www-astro-theory.fnal.gov/ISOSII/) will confirm. Speakers from corners of our local galaxy as far away as Tokyo and Stockholm will cover all that’s hot in particle astrophysics at the moment: inflation (down in the U.S. economy but still going strong in the universe); ultra-high energy cosmic rays (think Pierre Auger Project); neutrinos (particle of the year in 1998, but still very much au courant); dark matter (hot or cold, take your pick) and something called "Hot Results," speaker (presumably whoever arrives with the hottest of the hot) to be announced.

Friday’s midday session is a "Workshop on Future Missions," with heavy-hitting speakers Goldin, of NASA; Ernie Moniz, Under Secretary of the Department of Energy; and Bob Eisenstein, assistant director of the National Science Foundation. As noted, Goldin has said he will use the occasion for a major policy address. Come early for a good seat.

The undoubted highlight of the social program for Inner Space/Outer Space—perhaps of the entire season—will be Thursday evening’s Buffalo Banquet, in a tent in the Fermilab Village. No Fermilab buffalo will be harmed for this banquet. In fact, The ISOS Web site points out that May is a good time for viewing the adorable buffalo calves at Fermilab

as banqueters pass their pasture on the way to the feast. Vegetarian menu available on request. (That’s what the buffalo eat.)

Symposium organizers encourage members of the Fermilab community to attend Inner Space/ Outer Space. They hope for a high turnout from the Laboratory. Register on the Web site: http://fnpm27.fnal.gov/isos99/isos99registration.html

—Judy Jackson

Reversal of fortune

"Quench" is one of those words that accelerator physics turns into something other than it seems to be.

One common use of the word connotes satisfaction or fulfillment, as in quenching a thirst; another use describes cooling a hot metal by thrusting into water or another liquid.

But in dealing with the thousand superconducting magnets in Fermilab’s Tevatron, Mike Church recognizes a "quench" as something other than a cooling or satisfying experience: a quench is the highly unsatisfying phenomenon resulting when a deposit of energy results in an increase in temperature, transforming a superconducting material (which has virtually no resistance to an electric current) to a state of regular conductivity.

"We have them pretty routinely," said Church, commissioning chief for the Tevatron. "When one happens, we try to reduce the total amount of energy that is dumped into the magnet. If we don’t do that, we could possibly destroy the magnet. We try to avoid that scenario."

Church described three sources of quenching:

n A beam induced quench, when some fraction of the beam runs into the magnet, deposits energy into superconducting coils, raising their temperature and altering them to a state of regular conductivity;

n A component failure in the magnet itself, possibly a badly-soldered joint or some obstruction in the superconducting connections, generating resistance and raising the magnet’s temperature; or the motion of a mechanical component, generating enough heat from friction to raise the temperature and cause a quench.

n A rare failure of the Quench Protection Monitor system, which measures voltages across the magnets, power leads and other connections, determining whether the voltages are within the limits necessary for superconductivity. If the voltages are outside the limits, the system interprets that information as the start of a quench. The magnet heaters are then turned on, raising the entire magnet to normal conducting temperatures and spreading out the deposit of energy. All the energy from the magnet is then short-circuited into dumps and bypasses so current flows around the magnet instead of through it. All these steps are taken to reduce the total energy deposited into the magnet itself. As Church explained, dumping all the energy into a magnet could destroy the magnet.

The rise in temperature causes a major evaporation of the liquid helium used to cool the superconducting components near absolute zero (-273 degrees C). Church emphasized that the helium doesn’t vent into the accelerator tunnel, but remains in the system pipes and returns to the Central Utility Building compressor to be liquefied again.

"If the system works correctly, we don’t lose helium," he added.

If there is a helium loss, that leads to words unmistakable in their meaning, in or out of physics.

—Mike Perricone

last modified 5/14/1999   email Fermilab