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The Laboratory
in the News

New tools counter biological and chemical terrorism
In the November 21, 2003, issue of Science, three Livermore researchers discussed the recent progress in technology development to counter biological and chemical terrorism. The scientists noted that although important challenges remain, new detection systems show increased sensitivity, greater automation, and fewer false alarms.
In their paper, Pat Fitch and Dennis Imbro, who work in Livermore’s Chemical and Biological National Security Program, and Ellen Raber, who leads the Environmental Protection Department, say that technologies for countering bioterrorist agents are approaching the sophistication of technologies for fighting chemical warfare agents. Nevertheless, improvements are still needed for sensors to meet the high level of sensitivity needed to protect civilians and to reduce the high rates of false alarms.
The researchers also describe a decision-making framework of four phases to guide response activities following a terrorist attack: notification, first responder, characterization, and restoration (or decontamination and remediation). During the initial notification phase, an operations center identifies an event using data from sensors and intelligence analysis as well as information on casualties. The first-responder phase is likely to include such actions as isolating or stabilizing hazardous materials or taking care of casualties. The characterization phase focuses on determining key site parameters, including time since release, extent of contamination, and potential risks to human health and the environment. The final restoration phase involves selecting site-specific decontaminating reagents, if required, and sampling to verify that all long-term environmental issues have been addressed and the solutions meet regulatory standards.
The scientists cite several reasons for the substantial improvement in biological detection. For example, polymerase chain reaction can be used to amplify DNA for rapid analysis, and the development of very specific DNA signatures for pathogens provides more accurate identification. Another factor for success is that many tests and controls can be conducted simultaneously. The researchers caution that despite these advances, technical and logistical challenges still exist to effectively prevent or combat chemical and biological terrorism.
Contact: Pat Fitch (925) 422-3276 (jpfitch@llnl.gov).

Another view of black hole phenomena
When most people think of black holes, they think of an area of space where matter can disappear. But that view is inconsistent with quantum mechanics.
In 1991, Laboratory physicist George Chapline suggested that this inconsistency could be avoided if the vacuum state of ordinary space–time is assumed to be a kind of superfluid. The formation of black holes would correspond to a “squeezing” of the vacuum—a quantum process roughly analogous to the compression of an ordinary fluid.
More recently, Chapline and colleagues at Stanford University have extended this idea to account for the event horizon of a black hole. They proposed that near the event horizon surface of a black hole, ordinary space undergoes a continuous phase transition to a phase with a much larger vacuum energy than the cosmological vacuum energy inferred from observations of distant supernovae. The physicists have predicted that near the surface of a black hole, matter behaves in a markedly different way from what is predicted by classical general relativity.
Black holes are generally believed to be remnants of stars that have collapsed into themselves. This gravity can pull in and obliterate objects that approach the surface. Chapline’s group believes that black holes are actually extended bodies made up of “dark energy.” In this view, matter doesn’t disappear when it falls inside the event horizon surface of a black hole, but it can be transformed when it crosses the surface.
Chapline notes that the behavior of sound waves crossing a critical surface in a vertical column of a superfluid model provides the necessary insight into what happens to relativistic particles when they approach an event horizon. “The energy of the relativistic particles will become a quadratic function of momentum as they approach the surface,” he says. “Above a certain energy, the particles will become unstable as they cross the surface.”
As a result of this instability, a star falling onto the surface of a large black hole or a massive star undergoing gravitational collapse will emit pulses of radiation with characteristics that are similar to those of some cosmic gamma-ray bursts. An article about this work appeared in the July 2003, issue of Scientific American.
Contact: George Chapline (925) 422-4106 (chapline1@llnl.gov).

Search for planets yields shock-wave breakthrough
A small, inexpensive interferometer developed to help astrophysicists search for planets is also being used to boost the time resolution and stability of streak cameras that record high-speed phenomena, such as those that occur in shock-wave physics experiments. The externally dispersed interferometer (EDI) was first proposed in 1998 in a project led by Livermore physicist David Erskine. The system combines the white-light velocity interferometry techniques used on the Laboratory’s two-stage gas guns with an external grating spectrograph for astronomical imaging.
The EDI can be used to precisely measure small shifts in Doppler velocity. These shifts in the wavelength of starlight are caused by the motion of a planet around a star. Light passing through the periodic fringes of an interferometer and into the spectrograph creates a moiré pattern. This moiré pattern shifts transversely in proportion to the Doppler velocity. The EDI eliminates atmospheric distortions, which can reduce the precision in Doppler or spectroscopic measurements.
In 1999, when Erskine and his team tested the system at the University of California’s Lick Observatory on Mount Hamilton, they found that the EDI reduces the distortion of starlight. More recently, using information in the moiré patterns with special software, they demonstrated that the EDI can boost the spectrograph resolution at Lick by two times.
Erskine realized the EDI could also be used to improve the time resolution and stability of streak cameras, such as those used in experiments at the National Ignition Facility. Such a boost in time resolution is analogous to the increase in spectral resolution for astrophysical measurements.
Other potential applications for the EDI include high-resolution spectroscopy over a broad bandwidth, boosting the resolution and stability performance of existing spectrograph facilities, and searching for exoplanets by measuring stellar angular positions. More information on the improved spectral resolution from the EDI is available in the August 1, 2003, issue of Astrophysical Journal Letters.
Contact: David Erskine (925) 422-9545 (erskine1@llnl.gov).

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UCRL-52000-04-3 | March 3, 2004