Engineering topics

Ochs, Ian E. (ORCID:0000000260029169)

Publications and source records attributed to Ochs, Ian E. (ORCID:0000000260029169).

3 records

DOE OSTI2025

Preventing ash from poisoning proton–boron 11 fusion plasmas

Proton–boron 11 (pB11) fusion is safe and clean, but also difficult to harness for breakeven power production. Particularly deleterious are fusion-born alpha particles, which massively increase both plasma pressure and bremsstrahlung losses unless they are pulled promptly from the plasma. We show that even if one cannot extract the alphas quickly, one can still achieve net power production, by separating the plasma into two regions: a fusion region, accessible to all species, and an alpha storage region, accessible only to alphas and electrons. This new demixing strategy could make pB11 fusion much easier to achieve.

Ochs, Ian E. (ORCID:0000000260029169)↗

DOE OSTI2024

When do waves drive plasma flows?

Flows and rotation, particularly E×B rotation, are critical to improving plasma performance, and waves are a primary tool of plasma control. Thus, it is paramount to understand under what conditions waves can drive E×B flows in plasmas. In this didactic review, an invited paper accompanying the 2023 Marshall N. Rosenbluth Doctoral Thesis Award, this question is answered in the context of momentum-conserving quasilinear theory. There are two primary frameworks for momentum-conserving quasilinear theories that can handle both resonant and nonresonant particles: Eulerian averaging theories and oscillation-center Hamiltonian theories. There are also two different paradigmatic wave problems: plane-wave initial value problems, and steady-state boundary value problems. Here, it is shown that each of these frameworks “naturally” works better with a different problem type. By using these theories, one finds a great difference in the behavior of time- vs space-dependent waves. A time-evolving plane wave can only drive flow if the electromagnetic momentum of the wave, given by the Poynting flux, changes. This result precludes flow drive by any planar electrostatic wave. In contrast, a steady-state spatially evolving wave can drive flow whenever there is divergence in the flux of Minkowski momentum, a completely different physical quantity. This review aims to provide a high-level, intuitive understanding of the very different behaviors observed for these two types of problem.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗

DOE OSTI2024

Lowering the reactor breakeven requirements for proton–boron 11 fusion

Recently, it has been shown that altering the natural collisional power flow of the proton–boron 11 (pB11) fusion reaction can significantly reduce the Lawson product of ion density and confinement time required to achieve ignition. However, these products are still onerous—on the order of 7×1015 cm−3 s under the most optimistic scenarios. Fortunately, a breakeven fusion power plant does not require an igniting plasma, but rather a reactor that produces more electrical power than it consumes. Here, we extend the existing 0D power balance analysis to check the conditions on power plant breakeven. We find that even for the base thermonuclear reaction, modern high-efficiency thermal engines should reduce the Lawson product to 1.2×1015 cm−3 s. We then explore the impact of several potential improvements, including fast proton heating, alpha power capture, direct conversion, and efficient heating. We find that such improvements could reduce the required Lawson product by a further order of magnitude, bringing aneutronic fusion to target ITER ion densities and confinement times.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗