VME: Is that the typical system configuration: One of these betavoltaics connected to a lithium ion battery to power the circuitry?


CABAUY: That’s one configuration. The central application we’ve been looking at is to take the betavoltaic battery and use it to power up FPGA encryption keys held in SRAM – at an y temperature. Nano- amps is typically sufficient and it can easily be provided by the NanoT ritium battery. Furthermore, the NanoT ritium battery can reliably withstand e xtreme temperature conditions.


Battery-backed SRAM power is extremely important in fielded military applications such as a UAV, when it’s flying about 30-40,000 feet at -60 ˚C, then comes back down and lands in a very hot desert. Chem- ical batteries can see failure pretty quickly in a case like that. And when you’re deal- ing with encryption k eys, failure is not something you want to happen lest the system go brain dead upon power failure.


VME: Do you have an off-the-shelf version in existence yet?


CABAUY: We’re finalizing the design components and assemblies for the EOL200Y20 series, which is the FPGA encryption key battery and the first COTS betavoltaic battery. We’re projecting a summer release.


And I’d like to point out that the betavoltaic battery is nothing new. This idea has been around since Paul Rappaport, one of the fathers of solar cells, did his groundbreak- ing solar cell development [in the 1950s].


VME: It sounds like these advancements have been a long time coming.


CABAUY: Yes. It took decades of research and work for people to figure out the most viable candidates for radioisotopes: tri - tium, promethium, and Nickel 63.


Promethium is interesting; only has a half-life of 2.6 years, and it’ s very diffi- cult to get these days. Promethium 147 requires a bit of metal to be able to shield out the radiation coming out of it.


On the other hand, nickel is expensive and the flux is very, very low, so the usable power that comes out of it is not as good. Of the three, tritium is the preferred choice to generate betas.


VME: Let’s talk about the coming COTS betavoltaic battery you men- tioned earlier, the EOL200Y20 Series. “EOL” can have a negative connotation in the defense industry.


VME and Critical Systems / Spring 2011 17


CABAUY: It actually does stand for “end-of-life,” yes, but what we’re basi- cally saying is that at end-of-life, it will have 200 nanowatts at year 20. That’s why our NanoTritium betavoltaic battery is called “EOL200Y20.”


VME: What are the negatives of this technology? Does it outgas? Does it tend to be explosive?


CABAUY: I think the only ne gative is that it’s taken this long to commercialize a betavoltaic battery. As I mentioned, this idea came out in the 1950s and it seems like it’s only now at the point of usabil - ity, mostly because the FPGA and micro- electronics industries have lowered their


power requirements to start using long- term power like this.


VME: Which other applications do you foresee for betavoltaic batteries?


CABAUY: Within the defense industry, we see specifics with security supervi - sors, low-power microcontrollers lik e the MSP430 from Texas Instruments, or even ubiquitous computing. For instance, they’re usable for these v ery low-power microprocessors that can sleep on pico - watts and operate at nanowatts.


Also, these batteries could power the Uni- versity of Michig an’s Phoenix Proces - sor, a very low-power device implanted


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