Hamamatsu professor invents speedy radiation detector

November 19, 2011

By SHINICHI KAWARADA / Staff Writer

A researcher in Hamamatsu has created a postcard-sized device that can continuously take readings of radiation (gamma ray) levels caused by elements such as cesium at a rate of 40 measurements per second, even while the device is moving.

By combining the reading with locational data it can display a map with precise information on contamination.

"I hope it will help in evacuating residents and contribute to the recovery from the Great East Japan Earthquake," says Yoshihiro Takiguchi, 53, the device's inventor.

Takiguchi is a professor at the Graduate School for the Creation of New Photonics Industries, a school established by a group of founding partners led by Hamamatsu Photonics K.K., a company in possession of the latest optical technology. After studying nuclear engineering at Nagoya University's graduate school, Takiguchi was involved in projects such as laser development.

His box-shaped radiation meter is roughly 4 centimeters thick and smaller than a postcard. The user carries the lightweight 320-gram device while it is connected to a laptop computer.

According to Takiguchi, most conventional radiation meters, which measure the amount of electrical discharge caused when radiation passes through a tube filled with an element such as helium, take around a minute to get an accurate measurement for one location only. One commonly used device is known as a Geiger counter.

Taking a different approach, Takiguchi's device detects blue light emitted when gamma rays pass through a transparent plate made of metal oxide crystals and displays the results as a graph on the computer's screen, allowing for accurate, real-time measurements that are continuously updated as the user moves. The raw data is saved on the computer.

The crystal plates are produced by manufacturers in places such as Namie, Fukushima Prefecture, which make them for positron emission tomography (PET), a technique used for detecting cancer.

Takiguchi built a prototype of his device in May. After putting it in his car, he drove from Hamamatsu through the disaster area in Fukushima Prefecture, taking continuous measurements for 24 hours to collect data.

Efforts are now under way in the prefecture to remove contamination, which involves scraping away irradiated topsoil. Meanwhile, more residents in the Tokyo area are worried about abnormal radiation levels following the accident at the Fukushima No. 1 nuclear power plant and pockets with higher readings have been discovered in the metropolis.

"The national and local governments need to accumulate data on becquerel levels in topsoil and watch those levels for the next 100 years or more," Takiguchi says. "In addition, the figures in the data will be unreliable if we do not take precise measurements with a uniform method. This is why I wanted to provide a device that can take accurate readings in real time."

The device was exhibited at the Messe Nagoya trade fair held at Port Messe Nagoya through Nov. 12. Takiguchi says inquiries have already come from places such as Tochigi Prefecture. Due to the high cost of the crystal plates, he expects to sell the meters for about 350,000 yen ($4,500) each, but intends to provide it at cost in the disaster areas.

Inquiries can be made by calling the TAK System Initiative Corp. at 053-484-2010.

By SHINICHI KAWARADA / Staff Writer
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When a vial containing soil from the disaster area was placed near the device, the line on the graph on the computer moved up and to the right. (Shinichi Kawarada)

When a vial containing soil from the disaster area was placed near the device, the line on the graph on the computer moved up and to the right. (Shinichi Kawarada)

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  • When a vial containing soil from the disaster area was placed near the device, the line on the graph on the computer moved up and to the right. (Shinichi Kawarada)

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