The Nobel Prize in Physics 2023 and its potential connections to fusion plasmas

Congratulations to the winners of the Nobel Prize in Physics 2023 who created experimental methods for generating attosecond pulses of light! An accessible introduction to the physics behind this prize can be found here.

For a sense of scale, my doctoral thesis work used laser pulses that were nanoseconds, picoseconds, and femtoseconds long, corresponding to one billionth, one trillionth, and one quadrillionth of a second respectively. I used these lasers to create small plasmas (millimeter-sized) in gases, which I would then send a microwave beam to observe, for diagnosing both the gas and plasma (e.g., remote measurements of vector magnetic fields). Attosecond (one quintillionth of a second!) pulses get down to the fastest timescales in atoms, with the potential to track movements and transitions of the electron clouds.

The plasmas I work with nowadays are larger, closer to 10’s of centimeters, in the Princeton Field-Reversed Configuration-2 (PFRC-2) experiment. A femtosecond laser has been applied to the PFRC-2 for measurement of the neutral (non-ionized) atomic hydrogen by Dr. Arthur Dogariu, one of my Ph.D. advisors, see the paper here. Many of the plasma dynamics are closer to micro- and millisecond time-scales, at least a trillion times longer than an attosecond! As plasmas achieve higher temperatures, they gain a large number of fast particles, so we could anticipate some applications of attosecond diagnostics in very high temperature plasmas.

Although it might be a while before we would see attosecond lasers applied in plasma fusion experiments, it is important to think about the possibilities. One paper discusses using high intensity light from packing energy into such a short time for proton-boron fusion generation from a solid. More generally, there are many processes that occur in a plasma which are based in quantum mechanics (ionization, photo-emission, recombination) and a deeper understanding of these processes using attosecond diagnostics can certainly spill over into plasma physics by improving the models of these processes.

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