With the world still shaking from terror attacks, governments around the world are constantly focusing their energies into developing various ways to alert them of unusual activity. The nightmare of bombings continue even as time passes as events such as these not only cost human lives but cover the area with radiation leaving it inhospitable.
The terror of these events encourages researchers around the world to come up with new ways and technologies to prevent such occurrences. And a research team at Purdue University did just that by proposing the fitting of mobile phones with small radiation detectors.
These detectors would be sensitive enough to pick up low levels of gamma rays emitted by radioactive devices. The exact levels of which could be relayed to a central computer which then would use the position of the phone to build up a radiation map of the city.
Andrew Longman, a physicist specializing in instrumentation and currently working under contract for Purdue, said that the system could pinpoint the location of any dangerous radioactive device.
“If every cell phone user in the country were participating, it would be very hard to move any kind of serious nuclear device into a city. Right now, it is effortlessly easy.”
A small number of detectors positioned throughout a city would stand little chance of detecting a radioactive device, unless one came in very close proximity. To be effective, the system would make use of a large number of detectors in the busiest areas.
Although there would be a relatively large background noise of gamma rays from other sources, Longman said that his team adapted a technique from gamma-ray astronomy to make the signal from a radioactive device more visible.
Longman was reluctant to divulge how this technique works in detail for fear that people might figure out a way to “defeat it”. Normally in gamma-ray astronomy the signal is improved either by limiting the detector to a certain energy band or by orienting it to exclude noisy sources.
Tony Dean, an astrophysicist at the University of Southampton in the UK contradicting the proposal said that focusing on one energy band would not work because dirty bombs could contain isotopes emitting gamma rays at different energies.
Moreover, mobile phones are always moving and so could never be oriented in a set direction. This would imply that Purdue’s system relies on statistics to find a more radioactive, localized source in the map that is characteristic of a bomb.
Dean also thought that silicon would be the most likely choice for the detector. Other materials, such as cadmium-zinc-telluride are unlikely to operate at the low voltages found in mobile phones, while germanium needs cryogenic cooling. “A silicon detector could be made quite small — say 5 mm2 — with the entire circuitry ready on the back,” he adds.
The team, which along with Longman includes Ephraim Fischbach and Jere Jenkins from Purdue, have already tested the system on the Purdue campus. The researchers found that it could spot a test radiation source much weaker than a dirty bomb that was being carried around by one them and are now trying to commercialize the design.
Even if they are successful, however, it will be difficult to persuade mobile phone companies to integrate detectors within their products because it will add to both weight and cost.
“They need encouragement to be good corporate citizens,” says Longman, who thinks that “government moribundness” will be an issue. “[The US] spent less than $100m last year to solve the number one existential threat to the country. They need public pressure and interest to focus on things that could actually prevent nuclear terrorism at the level we did the Manhattan [atomic bomb] project in World War II.”