Crow Radio and Plasma Science Publications

1. "Simulations of the lower-hybrid antenna in the Madison Symmetric Torus reversed-field pinch" (official version and cheap substitute). The paper has a page on ResearchGate, which has some nice figures and a Comments box, if you have questions about it. This work was done to analyze the exotic interdigital line slow-wave antenna that was used to launch lower-hybrid waves at 800 MHz in the MST RFP magnetic-fusion experiment. Using FDTD 3D simulations with the VORPAL code we found that the antenna design had neglected to take into account the effect of an aperture, which undesirably increased the parallel (to the confining magnetic field) wavelength of the electric wave. Based on further simulations we proposed two solutions. Plan A was the proper solution, but required the antenna to removed from inside the vacuum vessel to have the interleaved digits shortened by 1.3 mm. Plan B was the quick and dirty solution of retuning the transmitter to 786 MHz. As far as I know, neither of the two proposed solutions was ever implemented. This was a fun project funded by ORNL that landed on my lap when Mark Carter left for Ad Astra. The interdigital line is difficult to simulate, but a really interesting launch structure. One could even claim that it's a meta material.
2. "Phase coherence of parametric-decay modes during high-harmonic fast-wave heating in the National Spherical Torus Experiment" (official version and cheap substitute). This paper also has a page on ResearchGate with a Comments box for any questions. This project started out as an SBIR proposal that was rejected by the program manager for being unresponsive to the solicitation. Also a second attempt to get it funded failed, but the third time was indeed the charm and I got a small subcontract from NSTX for doing parts of the original proposal. The project was to reprocess old probe data using more advanced signal-processing algorithms (third-order spectral analysis to complement the second-order methods previously used), and also to evaluate if the GNU Radio software toolkit could be useful for such analysis. The paper demonstrates that the bicoherence is a very good complement to the power spectrum for analyzing parametric-decay instability, as it tells you quantitatively how closely suspected daughter waves are related to a pump wave. I hope to be able to continue work in this area at some low level in 2017.
3. "Validation and benchmarking of two particle-in-cell codes for a glow discharge" (official version, cheap substitute and page on ResearchGate). The paper demonstrates the importance of code validation, benchmarking and uncertainty quantification to correctly simulate plasma devices with gas pressures of a few Torr and strong electric fields (kV/cm). It also defines a set of benchmark problems to test various anisotropic-collision models for these types of plasmas. The work was done as part of a collaborative effort with GE Global Research to simulate a gas switch with power-electronics applications and was funded by ARPA-E. Here are the slides for my ICOPS 2017 talk that presented the main findings of the paper.

Select Publications Under Other Affiliations