Radiation Hardened Infrared Focal Plane Arrays

Next generation rare isotope beam facilities require new and improved techniques, instrumentation and strategies to deal with the anticipated high radiation environment in the production, stripping and transport of ion beams. Radiation tolerant infrared video cameras using sensors with 5 µm and longer cut-off wavelength are needed for beam delivery and remote handling operations because they provide optimal sensitivity at the typical temperatures (300°C) encountered in these applications. In response to the DOE’s requirements, EPIR Inc. proposes to fabricate and deliver HgCdTe-based focal plane arrays and infrared cameras that are neutron radiation tolerant. We chose a material system (HgCdTe) that is relatively insensitive to radiation effects, and we propose to optimize the device processes to mitigate expected changes in material properties under irradiation. High sensitivity HgCdTe detector arrays can be tailored for response across the entire infrared spectrum and are commonly utilized at EPIR for the fabrication of infrared cameras. During the Phase 1 of the project we demonstrated in collaboration with Fermilab, material, device and camera stability under 108 neutrons/cm2/s irradiation flux, which is three orders of magnitude higher than the typical fluxes encountered in the isotope beam facilities. We also demonstrated material and device-level stability under 100 krad(Si) and 63 MeV proton irradiation. Irradiation causes progressive degradation of devices, which can be minimized by camera and detector design. We expect device performance degradation can be mitigated by our proposed optimization of the pixel geometry to reduce the effect of radiation-induced changes in carrier diffusion length. Such geometry optimization is one thrust of our proposed effort. We will also optimize 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. Our camera will be capable of operating at standard frame rates with video graphics array sensor resolutions, with a radiation tolerance for prolonged operation in the presence of neutron fluxes higher than 105 neutron/cm2/s and a total absorbed dose of ~ 1MRad/yr. We initially plan to use the 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. With the maturation of the technology, our products will also become relevant in environmental protection, consumer industrial production, scientific applications and instruments.