I attended the 11th IAEA Technical Meeting on Energetic Particles in Magnetic Confinement Systems to present a talk on the transport of fast ions due to microturbulence in tokamaks. The presentation can be downloaded from here. This topic is of great interest given the need to confine alpha particles in burning plasmas like ITER. Recent theory work suggests that microturbulence (i.e., long wavelength non-coherent instabilities, which are a focus of their own research endeavors) contributes to the radial transport of energetic ions. My experimental talk is primarily motivated by the following two theory results:

• C. Estrada-Mila, J. Candy, and R. E. Waltz, Phys. Plasmas 13, 112303 (2006): fusion α particles are found, through gyrokinetic simulation, to interact with ion-temperature-gradient (ITG) turbulence. This paper also includes estimates for the resulting perturbation to the α density profile.
• W. Zhang, Z. Lin, and L. Chen, Phys. Rev. Lett. 101, 095001 (2008): shows that the effect of microturbulence on energetic ions can be described as a diffusive process that becomes less important as the ion energy increases well beyond that of the background plasma. This paper also provided a predicted diffusivity for turbulent transport that is a function of the energetic ion pitch angle and energy distribution. Applying this diffusivity improved the agreement between our experimentally measured energetic ion profiles and those expected from modeling.

Group Photo. See also: Official Website Album or Full Size [new window]

The conference was held in Kiev, Ukraine at the Ukrainian House (“Ukrains'kyj Dim”). This is a type of Hall of Fame for Ukraine. The photo below shows the room in which the oral presentations were made. The walls are covered with portraits of famous Ukrainians. I gave the first talk of the meeting (after the opening welcome) and you might be able to see me in the upper-right of the photo.

Presentation room for the conference. If you look very closely, you might see me in the upper-right as I make my presentation. Also, notice the toroidal light fixtures.

My research group at UC Irvine is heavily involved in this area. Further information regarding the experimental results like those mentioned in my IAEA presentation may be found in the following publications:

• W. W. Heidbrink, et al., Plasma Phys. Control. Fusion 51, 125001 (2009): a thorough overview of neutral beam injection (NBI) in tokamaks. The injected particles ionize and become the energetic ion population. Microturbulence enhancements to energetic ion transport are investigated as a mechanism to explain disagreements between observed profiles and NBI theory.
• W. W. Heidbrink, et al., Phys. Rev. Lett. 103, 175001 (2009): initial reporting of experimental evidence for microturbulence enhanced transport of energetic ions. The experimental evidence is from fast-ion D-α measurements of the core energetic ion density which show deviations from classical (i.e., collision dominated) theory. Expected diffusivities as calculated in the theory work of W. Zhang, et al. (see reference above) are used to adjust theoretical predictions. The resulting adjustment is closer to the experimental observations, but a significant disagreement remains.

Fountain in a large public square of Kiev.