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I am a PhD Student at Vanderbilt University studying the effects of radiation on electronics.


Radiation is everywhere . . . so what exactly is it? And more importantly, can it hurt us?

The short answer: Our trusty pal Wikipedia tells us that radiation is the transmission of energy through space in the form of waves or particles. Lots of phenomena we encounter in everyday life are forms of radiation. Like what? Most people know that when they get an X-ray from a doctor, that’s a form of radiation. However, the light coming from your computer screen, the WiFi signal connecting to the internet, and even the sound of your fingers on your keyboard are all forms of radiation. Radiation can be broken down into waves and particles. Particulate radiation is made up of subatomic particles like protons, neutrons, or electrons. Particulate radiation typically comes from nuclear processes, whether that’s the atoms of a small sample of Po-210 decaying in a physics lab or a full-scale nuclear reaction. Most people don’t directly interact with particulate radiation in the course of a normal day. Radiation made up of waves is a different story. A wave is what happens whenever a medium vibrates. A water wave is water vibrating, a sound wave is the air vibrating, and electromagnetic waves are electric and magnetic fields vibrating. One familiar example of electromagnetic radiation would be X-rays. So then what are X-rays? Pose this question a different way and the answer may surprise you. What’s the difference between X-rays and radio waves? Because both X-rays and radio waves are types of electromagnetic radiation, they differ only in their wavelength (and energy). Is radiation dangerous? Good question. The answer is complicated, but what’s most important is the distinction between ionizing and non-ionizing radiation. Ionizing radiation carries enough energy to change the material it hits. This is why ionizing radiation can cause cancer by damaging your DNA. Ionizing radiation can also damage or disrupt electronics, which is a significant reliability issue in space. Examples of ionizing radiation include X-rays, gamma rays, and UV light. Non-ionizing radiation doesn’t carry enough energy to change materials. It can warm a material up, but in order for this to be noticeable, let alone harmful, you need a whole lot of it focused down to a tiny space (this is how microwave ovens work). So unless you spend a lot of time inside kitchen appliances, non-ionizing radiation can’t hurt you. Examples of non-ionizing radiation include visible light, microwaves, radio (which includes WiFi and cellphone signals), and heat.


Formal analysis of SEU mitigation for early dependability and performability analysis of FPGA-based space applications

Abstract: SRAM-based FPGAs are increasingly popular in the aerospace industry due to their field programmability and low cost. However, they suffer from cosmic radiation induced Single Event Upsets (SEUs). In safety-critical applications, the dependability of the design is a prime concern since failures may have catastrophic consequences. An early analysis of the relationship between dependability metrics, performability-area trade-off, and different mitigation techniques for such applications can reduce the design effort while increasing the design confidence. This paper introduces a novel methodology based on probabilistic model checking, for the analysis of the reliability, availability, safety and performance-area tradeoffs of safety-critical systems for early design decisions. Starting from the high-level description of a system, a Markov reward model is constructed from the Control Data Flow Graph (CDFG) and a component characterization library targeting FPGAs. The proposed model and exhaustive analysis capture all the failure states (based on the fault detection coverage) and repairs possible in the system. We present quantitative results based on an FIR filter circuit to illustrate the applicability of the proposed approach and to demonstrate that a wide range of useful dependability and performability properties can be analyzed using the proposed methodology. The modeling results show the relationship between different mitigation techniques and fault detection coverage, exposing their direct impact on the design for early decisions.

Pub.: 04 Mar '17, Pinned: 14 Apr '17