We have been operating the Princeton Field-Reversed Configuration-2 (PFRC-2) at the new, lower frequency of 1.8 MHz since mid-November. We have blogged about some developments towards operating at this new frequency including installation of the new capacitors as well as power supplies and holders for the belt coils.
The frequency we describe is that of the rotating magnetic field (RMF) which is generated by four radio-frequency antenna loops surrounding the machine. The RMF is responsible for creating a higher density field-reversed configuration plasma out of an initial lower density seed plasma and for heating the ions and electrons in the plasma.
The video below shows bright plasma pulses of increased density driven by RMF, now in various gases (argon, helium, and hydrogen):
Achieving bright plasma pulses is an important first step in operating at the new RMF frequency. This frequency will be within the range at which we expect ion heating to occur once we finish installation of the belt coils to increase magnetic field. We first observed bright plasma pulses at the new frequency of 1.8 MHz in argon gas due to its lower ionization potential in comparison to that of molecular hydrogen. In the experiment runs following the run with argon, we tuned parameters such as magnetic field, pressure, and seed plasma power until we began to see bright flashes in helium and hydrogen (where there is still a small percentage of argon). We are continuing work on optimizing the bright flashes for these gases.
In the next few months we plan to increase the magnetic field and measure the plasma with the ion energy analyzer built by the Princeton Plasma Physics Laboratory (PPPL) for this experiment with support from ARPA-E. This will show us how much plasma heating is happening!
In other good news, our two INFUSE awards with PPPL, which were announced this summer, have finally received all necessary approvals from DOE and are kicking off. Sangeeta and I (Chris) are at the lab helping to run the PFRC-2 experiment every week and will soon be running software simulations for the INFUSE projects. We will be studying plasma stabilization techniques and new antenna configurations, all to maximize plasma heating efficiency!
Stay tuned as we continue to update on our progress with the PFRC-2!