Researchers at Colorado State University have developed a novel mechanism to quantify the level of radiation exposure on a SRAM chip without any active power requirement. This mechanism can be utilized to allow devices containing SRAM chips to act as real-time dosimeters. This can eliminate the time-delay between exposure and detection that occurs with traditional dosimeters and allow already ubiquitous devices, such as smartphones, to be used for radiation monitoring and tracking.
It has been previously identified that the power-up state of SRAM chips yields a random, unpredictable signature, which can be used as a digital fingerprint or Physical Unclonable Function (PUF), which can be used to differentiate, identify, and authenticate chips and devices. When a device is turned off and then powered-up again, the unpredictable signature generated in the newly powered-up state of the chip is similar, but not identical as electronic noise will cause some instability and changes. The amount of change/instability can be calculated and is referred to as the Hamming Distance (HD). We’ve now identified that ionizing radiation also creates instability and changes to the unpredictable signature and this additional change in the HD can be evaluated and used to quantify radiation exposure.
Researchers calculated a baseline HD for silicon SRAM chips and then exposed them to gamma radiation. They then calculated the change in the HD seen after the exposure, compared to the baseline. There is a correlation between the change in HD and the total ionizing dose of radiation (Figure 1). The chips remained fully functional even after a dose of 350 kilorad. The change in HD is significant at high radiation doses, but still quantifiable at lower radiation doses (Figure 2). SRAM chips are widely used in many phones and devices. Utilizing the correlation between change in HD and radiation exposure can enable portable personal electronics to function as dosimeters, and allow radiation tracking overtime in a passive and non-invasive manner that requires no additional equipment.
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TRL: 3
US Provisional Patent
Biswajit Ray
Jessy McGowan
Jessy.McGowan@colostate.edu
970-491-7100