Radiation Hardened Infrared Focal Plane Arrays

Radiation tolerant infrared focal plane arrays (FPAs) and video cameras are needed for beam delivery and remote handling operations in the next-generation rare isotope beam facilities under high radiation environments. EPIR has been designing and fabricating the neutron radiation-tolerant HgCdTe- based FPAs and assembling infrared cameras for use in nuclear reactors and the next-generation rare isotope beam facilities. The material system (HgCdTe) that we chose for the fabrication of the FPAs is relatively insensitive to radiation effects, and we additionally optimized the device processes to mitigate expected changes in material properties under irradiation. During Phase I and II of the project we demonstrated in collaboration with Fermilab material, device and FPA imaging stability after 9.3×1011 neutrons/cm2 accumulated dose under 2.6×108 neutrons/cm2/s flux, and up to 66MeV neutron energy irradiation. Recently, we also tested EPIR’s components together with the radiation-hardened electronics fabricated by the DoE contractors for R&D radiation-hardened electronics (AlphaCore, Nalu Scientific), as well as commercial ROIC vendor Senseeker, under higher than 2×109 neutrons/cm2/s irradiation. The total dose was larger than the one expected for 1×105 neutrons/cm2/s continuous exposure over two years. We are currently testing these components and electronics. Irradiation causes displacement damage and progressive degradation of devices, which can be minimized by the camera and detector design. The device performance degradation can be mitigated by our optimization of the pixel geometry to reduce the effect of radiation-induced changes in carrier diffusion length. In the current program, we demonstrated progress in material growth and device processing development. In addition, we optimized the design of the camera architecture and shielding, so that the detectors and electronics are exposed to only a small fraction of the total neutron flux while maintaining a distortion-free infrared imaging functionality. The camera designed in Phase II uses commercial read-out-integrate-circuit (ROIC) and can operate at standard frame rates with Video Graphics Array (VGA) sensor resolutions. In phase IIA, we will design and fabricate FPAs that can be seamlessly hybridized with ROICs incorporating advanced radiation-hardened designs supported by parallel DOE/NP programs. To better work with the ROICs, we will modify our detector design and increase image resolution up to Extended Graphics Array formats or higher to match the ROICs. Subsequently, we will integrate the hybridized FPAs into the camera system designed in Phase II. In addition, with the anticipated future availability of the new radiation-hardened ROICs fabricated under DOE/NP funded programs, EPIR will further modify our FPA footprint to accommodate these new ROICs. As part of the Phase IIA program, we will continue our collaboration with Fermilab to test the camera’s imaging capability under prolonged strong neutron flux (>2×109 neutron/cm2/s) and we will demonstrate operability of our cameras in current and new DOE isotope beam facilities. While radiation hardness has been required for specialized DOD and NASA detector applications and is needed for future DOE applications such as in next-generation rare isotope beam facilities, radiation-hardened focal plane arrays and cameras such as those proposed here by EPIR are currently not commercially available. We initially plan to use the newly developed technology for remote monitoring of nuclear reactor and particle accelerator facilities (routine operation or accident mitigation). Numerous future applications include space-based sensors with improved performance for surveillance, weather monitoring, planetary science, and missile defense. Non-space applications of radiation hard cameras include remote monitoring of nuclear reactor facilities and high altitude aircraft.