used to identify the radioactive isotopes producing those gamma rays.
The catch is that due to the semiconductor physics of germanium, the material can only be used when cryogenically cooled, either with liquid nitrogen or a large mechanical refrigeration unit. This means workers must begin the cool-down process many hours before any measurement can be taken. (It’s possible to have a large, cooled spectrometer on hand with perpetually refreshed liquid nitrogen, and that method is used, but H3D says it’s impractical, especially during emergencies.) Researchers knew that CZT could theoretically substitute for germanium, while operating at room temperature. But for decades, no one could make CZT detectors work—and some scientists thought it might actually be impossible to build a practical device using the material.
H3D, apparently, has done something unprecedented: It has come up with a way to make CZT competitive with germanium for almost all applications where high energy precision is needed. How? The trick was figuring out how to sense the 3D position of radiation using a single crystal of CZT. Zhong He did that by charting exactly where every gamma ray interacts in the crystal and how much energy the ray deposits with each interaction. He also developed a way to get 3D information on the locations of multiple sources of radiation using the timing of signals from the crystal. Still, it took He more than a decade to understand and make sense of the details of the readout from the CZT crystal, and to improve the electronics and calibration process enough to provide the precision needed.
“The Polaris-H can tell not only the presence of radiation, but also what kind of radiation,” Kaye says, adding that the ability to differentiate the type is key in homeland security applications. “Plus, it allows us to have [the detector] all in one battery-operated package that weighs less than 10 pounds.”
Kaye calls the core team behind H3D—himself, He, chief technical officer Feng Zhang, and sales director Weiyi Wang—remarkable. “Dr. He tries to pull top nuclear physicists,” he says. “The talent has grown in over time, so it can’t be replicated. It takes a very long, dedicated effort.”
Kaye says H3D wouldn’t exist without Zhang’s contributions in particular to developing the technology, and Zhang says his work with H3D suits him very well, as it also requires strong skills in computer programming.
In 1998, Zhang invented the legendary Proxy Hunter software to help Chinese Internet users tunnel through China’s Great Firewall without detection. Kaye says Zhang is so humble, it took his colleagues a long time to figure out his contribution to Chinese Internet freedom. (Someone in the lab finally noticed Zhang used a @proxyhunter e-mail address and asked him about it.)
“I haven’t followed Proxy Hunter for 10 years, but I imagine it’s still useful,” Zhang says. “I love this job [at H3D] because it’s the same as Proxy Hunter—we’re addressing a need that can improve lives and security. This is very new technology, not available before, with many different capabilities. Like Proxy Hunter, once it gets in people’s hands, it might do something very different.”
Zhang agrees with claims that H3D’s technology has the potential to revolutionize nuclear detection. “I’ve been working on this technology for 14 years,” he says. “I believe in it very much.”
Kaye is also a true believer. He grew up in Oregon and was working at the Pacific Northwest National Laboratory as an undergraduate when his boss introduced him to He. Kaye was already familiar with U-M thanks to its reputation as a top university for nuclear engineering, so working with He wasn’t a tough sell.
Though the research behind H3D’s devices was supported by nearly $20 million in grants to U-M from the Department of Energy, the Department of Homeland Security, and the Department of Defense, Kaye says H3D has been bootstrapped from its inception. (H3D has, however, won cash awards from the Accelerate Michigan business competition and the iCorps program.)
The H3D team is comprised of seven people, and it has begun to market its devices more aggressively now that its prototypes have been sold and are drawing praise from industry leaders like Bill Hagen. In addition to the Polaris-H, H3D has sold prototypes to NASA for use in studying radiation coming from space, and to researchers at the University of Maryland who are working on proton therapy, a highly accurate form of radiation treatment, for cancer patients.
And because H3D’s technology is able to detect what kind of isotopes are present in a truckload of radioactive material—and whether those isotopes are coming from, say, clay or kitty litter or a dirty bomb—Hagen expects that the company will have an enormous impact on homeland security, particularly at border crossings and international weapons inspections.
“The application H3D is going after first is nuclear power, but in the long run, I’m looking forward to it becoming viable and incredible for security applications,” Hagen says. (I called Ortec, a leading Tennessee-based nuclear detection company and maker of germanium-based devices, to hear their opinion on the promise of CZT, but Ortec did not respond.)
In addition to the markets that company officials have laid out in H3D’s carefully constructed business plan, the company is also excited about the potential of the technology in defense applications. “This is not a speed play,” Kaye says, in reference to H3D’s methodical approach to market capture. “We want to make sure our technology works.”
