Project Description
In this project, I played a key role in developing a cost-effective and high-resolution system for measuring the RF amplitude and phase in high-power RF heating systems, specifically for the DIII-D tokamak. The system aimed to improve the diagnostic capabilities of RF transmission lines, focusing on resolving phenomena like antenna arcing and plasma loading during edge localized modes (ELMs) on sub-millisecond timescales.
My work began by evaluating multiple approaches to the signal processing upgrade, considering factors such as cost, precision, dynamic range, and achievable temporal resolution. One of the main challenges I tackled was finding alternatives to expensive, high-speed digitizers like the NI PXI-5152, which would have made the project prohibitively costly due to the high number of channels (over 100) and data storage requirements.
To address these challenges, I contributed to developing and simulating burst subsampling techniques, which enabled us to sample RF signals in short bursts using multiplexers and sample-and-hold amplifiers. This method dramatically reduced the overall cost while still providing high accuracy (0.25 µs resolution with less than 6% fractional error). I also ensured that the system could reconstruct amplitude and phase information with minimal external circuitry, simplifying the design further.
Additionally, I designed and tested timing solutions to handle propagation delays that could cause out-of-order sampling, demonstrating the system’s viability through real-world simulations. My work culminated in a plan to implement the hardware, with all software—such as MATLAB code for converting I/Q data into amplitude and phase—already prepared for the next phase of development.
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