Characterization of an in-core irradiator for testing of microelectronics in a mixed radiation environment



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In recent years, the space industry is increasingly in search of easily available commercial and emerging technology devices in order to meet rigorous spacecraft requirements such as weight, power, and cost. Before an electronic device is put in a radiation environment, it is pre-tested and certified for space applications. This process of radiation testing and certification is costly and time intensive. Development of a test methodology and a facility to perform these tests quickly and cost effectively would facilitate the radiation effects community and NASA to fulfill the “Faster, Better, Cheaper”. With the rapid developments in the field of satellitebased telecommunications, the move from analog to digital controls for all electronic devices is imminent; hence, the need for radiation-hardened mixed signal processing devices is obvious. Digital-to-Analog Converters (DAC) are of particular interest due to their complex design and performance and their importance in digital signal processing. Limited literature exists for radiation effects on DAC. Most of these studies were performed with γ-ray irradiations (Total Ionization Dose, TID) but the much needed displacement damage data is absent. In the first phase of this work, an in-core mixed radiation (neutron and γ-ray) test facility at the University of Texas at Austin TRIGA Mark II nuclear research reactor was fully characterized. Further, a test methodology to perform radiation testing on complex “off-the-shelf” semiconductor circuits in a time and cost effective manner was developed. In the second phase, the characterized test facility and the methodology were then employed to successfully assess performance degradation of three commercially available DAC circuits: DAC 0808, MC 1408 (DIP package) and MC 1408 (SOIC package). This research has resulted in the development of a unique in-core fast neutron irradiation facility from a research reactor source. The average fast flux of 1.2E9 n/ cm 2 -s at 1 kW enables the generally desired 1E14 neutron fluence by the radiation testing community in a 1 hour irradiation. This facilitates the radiation effects community with a much desired cost- and time-effective neutron displacement damage test facility. The test facility was successfully used to determine neutron displacement damage in all three DAC circuits. The experimentally observed performance degradation curves for DAC shows that all three DAC performed within the company specifications at 1 MeV neutron fluence of 1.5E14 n/cm2 -s. It also demonstrated a test methodology that can be employed to analyze performance degradation in DAC and other complex semiconductor circuits using neutron and γ- ray irradiations.