abstract: Space exploration is a large field that requires high performing circuitry due to the harsh environment. Within a space environment one of the biggest factors leading to circuit failure is radiation. Circuits must be robust enough to continue operation after being exposed to the high doses of radiation. Bandgap reference (BGR) circuits are designed to be voltage references that stay stable across a wide range of supply voltages and temperatures. A bandgap reference is a piece of a large circuit that supplies critical elements of the large circuit with a constant voltage. When used in a space environment with large amounts of radiation a BGR needs to maintain its output voltage to enable the rest of the circuit to operate under proper conditions. Since a BGR is not a standalone circuit it is difficult and expensive to test if a BGR is maintaining its reference voltage. This thesis describes a methodology of isolating and simulating bandgap references. Both NPN and PNP bandgap references are simulated over a variety of radiation doses and dose rates. This methodology will allow the degradation due to radiation of a BGR to be modeled easily and affordably. It can be observed that many circuits experience enhanced low dose rate sensitivity (ELDRS) which can lead to failure at low total ionizing doses (TID) of radiation. A compact model library demonstrating degradation of transistors at both high and low dose rates (HDR and LDR) will be used to show bandgap references reliability. Specifically, two bandgap references being utilized in commercial off the shelf low dropout regulators (LDO) will be evaluated. The LDOs are reverse engineered in a simulation program with integrated circuit emphasis (SPICE). Within the two LDOs the bandgaps will be the points of interest. Of the LDOs one has a positive regulated voltage and one has a negative regulated voltage. This requires an NPN and a PNP based BGR respectively. This simulation methodology will draw conclusions about the above bandgap references, and how they operate under radiation at different doses and dose rates. / Dissertation/Thesis / Masters Thesis Electrical Engineering 2019

In this study three polymers, namely poly(carbonate urethane), poly(bisphenol-a-epichlorohydrin) and poly(methyl methacrylate), were selected and change of properties with gamma treatment were studied. Two different dose rates were used for irradiations and the properties of the irradiated polymers exposed to same total absorbed dose were compared. In addition, long irradiations of up to about six months with high dose rate were done in order to understand the radiation stability of the polymers, which may be possible candidates for embedding media for low and intermediate level radioactive (nuclear) waste before their final disposal. Tensile, DSC, DMA, TGA, FTIR-ATR, FTIR tests were completed to understand the degradation of the polymers as a function of dose rate and total absorbed dose. The DSC and FTIR results showed that there was not much structural chemical changes in polymer chains with irradiation. However, the changes in mechanical properties were recorded. It was concluded that poly(carbonate urethane) and poly(bisphenol-aepichlorohydrin) can possibly be used in conditioning of radioactive waste, as they are radiation stable polymers. However, due to the moderate resistance of poly(methyl methacrylate) to ionizing radiation, it can be used for low level radioactive waste conditioning.

Within the theoretical part of the diploma thesis, a list of the main types of accelerated tests designed for the resistance of metal and polymer surface finishes. In the experimental part of diploma thesis, the rate of biological resistance of wood-based board materials is evaluated. Furthermore, the resistance of coating systems is assessed by means of accelerated tests. Resistance of modular building shells is primarily focused on degradation of coatings applied primarily on metal materials and wood materials. The tested coating systems analyze the influence of the materials and chemical base on the final weather resistance.