Astrophysical Device Will Sniff Out Terrorism (Forwarded)

Media Relations
Caltech

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Mike Rogers, (626) 395-6083

January 18, 2006

Astrophysical Device Will Sniff Out Terrorism

PASADENA, Calif. -- Astrophysicists spend most of their time looking for
objects in the sky, but 9/11 changed Ryan McLean's orientation.

Right after the terrorist attacks, the Caltech staff scientist began
applying his knowledge about detectors that study galaxies to the design
of new sensors for detecting radioactive materials near possible terrorist
targets. A few months ago, the U.S. Department of Homeland Security
awarded McLean the first phase of a $2.2 million contract to develop a
radiation-detection module.

"Before 9/11, I had a safe feeling that life was great," says McLean, who
came to Caltech in 1999 to work for Professor of Physics Christopher
Martin, developing projects in which rockets were launched with
instruments that, during their five minutes above the atmosphere, observed
the dust and hot gases in the Milky Way. "But I have two young kids, and
now I realize that things may not be so stable."

The first part of McLean's project is to create a specialized chip that
turns a semiconducting crystal into a detector that can find a radiation
source up to 100 meters away and tell whether it's harmful radiation from
a dirty bomb, or harmless radiation from, say, a truckload of fertilizer.
In the second phase, which could begin by the middle of 2006, he'll build
a workable device.

The problem with current detectors is that they are often set off by
essentially benign materials. They also tend to be large pieces of
equipment located only at the nation's entry points, such as ports.

McLean wants to make detectors that will ignore natural radiation sources
like fertilizer and that will also be small and mobile, so that security
officers can take them anywhere and target any ship, truck, or building.

McLean, who has also contributed to a project at the Lawrence Livermore
National Laboratory (LLNL) to build a radiation detector the size of a
cell phone, plans to use a sensor made of cadmium zinc telluride, which
has been used in telescopes to detect gamma rays and X rays. The advantage
of these crystals is that they work at room temperature, unlike other
sensors that work only at very low temperatures.

To accomplish this, McLean teamed with the X-ray/gamma-ray group at
Caltech's Space Radiation Laboratory (SRL), which is led by Professor of
Physics Fiona Harrison. The SRL has been developing cadmium zinc telluride
gamma-ray sensors, as well as custom, low-noise, low-power electronic
chips for X-ray and gamma-ray instruments, for more than 10 years. While
SRL's efforts have largely focused on developing these sensors for space
missions, after 9/11 SRL teamed with LLNL to develop a chip for a handheld
radiation monitor for Homeland Security.

Surprisingly, looking for radiation on the ground is not much different
from searching for it in space. "What we are doing with Ryan is taking the
best of what we developed for the previous Homeland Security device, and
combining it with the best of what we developed for our space
instruments," says senior SRL engineer Rick Cook. Everything SRL has
learned about the pros and cons of the cadmium zinc telluride itself will
also be key to making this project a success.

McLean says that he does not expect the project to put Caltech into the
antiterrorism radiation-detection business. If his device shows promise,
the technology could be licensed to a company that would manufacture a
range of detection products at relatively low cost, making widespread use
feasible.

"The idea is that if you could have lots of small detectors, you might
have a better chance of detecting harmful nuclear material than if you're
stationed only at central locations, like bridges and ports," he says.

Given government officials' warnings that it is only a matter of time
before the next terrorist attack in the United States, McLean says that
there is a lot of pressure to complete the work quickly. "It helps push
the project along."