As part of the NIST on a Chip program, the Photonic Dosimetry project is set to develop in-situ sub-micrometer ionizing-radiation dosimetry and calorimetry leading to new chip-based metrology for industrial and medical applications. Increased sensitivity, spatial resolution, optical readout and multiplexing capabilities could fill measurement gaps for industrial processing using electron and photon beams, enable new portable sensors, and quantify dose delivered to patients in radiation-treatment procedures.
Our goal is to facilitate the rapidly-growing use of spatially localized radiation beams for precision medicine and for more efficient manufacturing. NIST is responding to industry requests to create measurement solutions for new applications. The sensors we are developing are also of great interest for use in harsh environments, such as space or energy-generation.
Presently, there is only limited traceability to national standards for measuring radiation dose at the very small length scales where industry is pushing, and NIST is investing in new technology to meet this need. Now is a critical time for U.S. manufacturing in the large and growing markets for precise delivery of radiation for uses such as:
To remain competitive in these fields, U.S. manufacturers are expanding capabilities in machine-based electron and ion beams, which are effective, efficient, and secure. However, the newer techniques such as low-energy electron irradiation and ion therapy deliver dose gradients over very short distances (microns), and therefore require high resolution absorbed-dose sensors for irradiation planning, validation, and quality assurance.
No sensors are currently able to meet all industrial and medical needs for these new techniques, but the NIST on a Chip program is researching a solution based on commercial silicon chip fabrication and telecommunications photonics technology. The goal of this program is not only to create a new sensor that is miniaturized for NIST calibrations, but to partner with industry to make the technology deployable in the field.
To this end, NIST has begun measuring the impact of ionizing radiation on the performance of silicon photonic devices. In the first round of testing, the team irradiated chips with up to 1 MGy dose—well beyond the dose required for many industrial applications, and several thousand times higher than most medical radiation treatment levels--- with little to no damage to the photonic devices. These early results indicate that such photonic devices are robust enough to serve as an integral component in future calorimeter designs. Studies are ongoing of in-beam irradiation effects on photonic devices and material and device designs for ionizing radiation applications.