Helping Other People Do Physics: A Story About Circuit Design

The Light Lab is currently studying the breakdown of polyfluoroalkyl substances (PFAS) and the modification of surface chemistry using plasma jets. My role was to design and build electronic devices for use in these plasma experiments. A high-speed transimpedance amplifier for a photodiode array, a kilohertz plasma jet driver, and a frequency-doubling clock circuit. These all required very different kinds of attention and design, from intensive considerations taken in the PCB architecture to ensure stability, to cost-saving measures to allow for ease of implementation. All devices required bespoke designs to address lab-specific instrumentation and financial challenges. We seek to resolve the rate of injected solvated electrons at the water plasma interface by extracting a trace modulation in the absorption spectrum of water, using a pulsed white laser. Our amplifier must be sensitive and fast, resolving the nature of the laser pulses. To ensure we are not measuring induced EMI signals, our timing scheme must be precise and in phase with the laser’s driving signal. It is crucial that the instruments I designed can be relied on to be stable and consistent. I outline how I designed the three aforementioned devices to address these concerns and the results of their implementation. I also suggest further research and design that could build on the solutions I have devised.