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All sourcesNASA NTRSDOE OSTI
DOE OSTI2025

Transport and confinement physics: Chapter 2 of the special issue: on the path to tokamak burning plasma operation

Progress in physics understanding and theoretical model development of plasma transport and confinement (TC) in the ITPA TC Topical Group since the publication of the ITER Physics Basis (IPB) document (Doyle et al 2007 Nucl. Fusion 47 S18) was summarized focusing on the contributions to ITER and burning plasma prediction and control. This paper provides a general and streamlined overview on the advances that were mainly led by the ITPA TC joint experiments and joint activities for the last 15 years (see JEX/JA table in appendix). This paper starts with the scientific strategy and scope of the ITPA TC Topical group and overall picture of the major progress, followed by the progress of each research field: particle transport, impurity transport, ion and electron thermal turbulent transport, momentum transport, impact of 3D magnetic fields on transport, confinement mode transitions, global confinement, and reduced transport modeling. Cross references with other Topical Groups are given in order to highlight overlapped topics, such as the 3D effect on the plasma transport in the edge and L-H transition physics. The increasing overlap between the topical groups is a reflection of the progress on integrating the known physics into comprehensive models that are better and better able to reproduce the plasma transport. In recent years, such integration has become increasingly prevalent when considering transport from the SOL, through the edge pedestal, and into the plasma core. In the near future, increased collaboration also with the magneto-hydrodynamic and energetic particles community will be important as we approach burning plasma conditions in next-step fusion devices. A summary of remaining challenges and next steps for each research field is given in the Summary section.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2025

Entanglement, trace anomaly, and confinement in QCD

We formulate confinement in quantum chromodynamics (QCD) as an entropic surface phenomenon. Quark and gluon quantum information is localized on a transverse, entangling two-sphere of radius 𝑅 𝐸⁢𝐸 ; at this radius the QCD vacuum—partitioned by a hadron into interior and exterior regions—reaches its maximal entanglement entropy. Lattice-QCD determinations of the scalar (trace) gravitational form factors fix both 𝑅 𝐸⁢𝐸 and the transverse trace-anomaly density 𝜌 ℎ ⁡(𝑅 𝐸⁢𝐸 ), yielding a parameter-free slope 𝑐 ℎ = 8⁢𝜋 2 ⁢𝑅𝑆$^2_{𝐸⁢𝐸}$𝜌 ℎ ⁡(𝑅 𝐸⁢𝐸 ) and a mechanical entropy 𝑆 𝐸⁢𝐸 ⁡(𝑦) = 𝑐 ℎ ⁢𝑦 that grows linearly with rapidity 𝑦. The entropy gradient ∂ 𝑅 𝑆 𝐸⁢𝐸 changes sign at 𝑅 𝐸⁢𝐸 : it pushes colored degrees of freedom outward for 𝑟 <𝑅 𝐸⁢𝐸 and pulls them inward for 𝑟 >𝑅 𝐸⁢𝐸 , thereby localizing them on the codimension-2 entangling two-sphere Σ ⊥ = 𝑆$^2_{𝑅_{𝐸⁢𝐸}}$ (which, in the infinite-momentum frame (IMF), projects onto the transverse plane)—the “information wall.” This provides a high-energy (large-𝑦) entropic confinement diagnostic that complements—rather than replaces—Wilson’s area-law criterion, which probes long-distance dynamics near the rest frame (𝑦 → 0). Imposing unitarity on an entropic ansatz for the amplitude yields 𝜎⁡(𝑠) ∝ 𝑦 𝛿 . World data favor 𝛿 = 2 for elastic 𝑝⁡𝑝⁡($𝑝\bar{⁡𝑝}$) scattering and heavy-quark photoproduction, whereas 𝜙 photoproduction favors a softer 𝛿 = 0.387. All extracted cross sections remain well below the Froissart-Martin bound. These results provide a confinement criterion quantified directly from nonperturbative QCD inputs, unifying the trace anomaly, entanglement entropy, and high-energy scattering within a single quantitative framework.

Color confinement↗
DOE OSTI2025

2D Vacancy Confinement in Anatase TiO 2 for Enhanced Photocatalytic Activities

Abstract Light‐driven energy conversion devices call for the atomic‐level manipulation of defects associated with electronic states in solids. However, previous approaches to produce oxygen vacancy (V O ) as a source of sub‐bandgap energy levels have hampered the precise control of the distribution and concentration ofV O . Here, a new strategy to spatially confineV O at the homo‐interfaces is demonstrated by exploiting the sequential growth of anatase TiO 2 under dissimilar thermodynamic conditions. Remarkably, metallic behavior with high carrier density and electron mobility is observed after sequential growth of the TiO 2 films under low pressure and temperature (L‐TiO 2 ) on top of high‐quality anatase TiO 2 epitaxial films (H‐TiO 2 ), despite the insulating properties of L‐TiO 2 and H‐TiO 2 single layers. Multiple characterizations elucidate that theV O layer is geometrically confined within 4 unit cells at the interface, along with low‐temperature crystallization of upper L‐TiO 2 films; this 2DV O layer is responsible for the formation of in‐gap states, promoting photocarrier lifetime (≈300%) and light absorption. These results suggest a synthetic strategy to locally confine functional defects and emphasize how sub‐bandgap energy levels in the confined imperfections influence the kinetics of light‐driven catalytic reactions.

Chemistry↗
DOE OSTI2026

Effect of Sample Mass, Confinement, and Preheating Time on the Thermal Response of LLM‐105: Experiments and Kinetic Analysis

Various small-scale experiments were performed to provide data for developing a model to predict the thermal response of LLM-105 over a wide range of conditions. The thermal decomposition of LLM-105 was studied as a function of sample mass, confinement of volatile products, and preheating time in both isothermal and ramped heating experiments. The thermal decomposition of LLM-105 is a two-step process, as shown by the two exothermic peaks in the heat flow profiles, which were fitted to two nth-order autocatalytic reaction models with a similar activation energy of ∼289 kJ/mol. The magnitude and shape of these peaks varied with sample mass and confinement. Increasing sample mass enhanced the second exotherm with respect to the first one, while increasing the level of confinement promoted a transition from a sublimation-dominated regime towards thermal decomposition. The effect of LLM-105 particle size on the rate of weight loss was evident for open-pan experiments, where bigger particles sublimed at lower temperatures than smaller particles. Thermal response and solid residue composition of LLM-105 samples were analyzed following preheating for different durations. Longer preheating times caused a shift of the second exotherm to lower temperatures and a decrease in the reaction enthalpy, confirming that LLM-105 decay is a consecutive reaction mechanism, probably autocatalytic. In conclusion, the kinetic model derived from ramped experiments was validated against the measured LLM-105 fraction remaining and the enthalpy remaining of the solid residue as a function of preheating times and showed good agreement.

Chemistry - Chemical explosives↗
DOE OSTI2026

Disentangling interlayer confinement and pore surface adsorption in functionalized smectites for tunable ethylene gas capture

Smectite-based adsorbents are increasingly being studied as sustainable packaging materials for scavenging ethylene, a plant hormone that accelerates fruit ripening. However, the mechanisms governing their uptake and retention remain poorly understood. Here, to tackle this question we systematically investigate ethylene gas-solid interactions in pristine, acid-activated, and choline-functionalized montmorillonites using a complementary combination of structural, gravimetric, and spectroscopic techniques, including inelastic neutron scattering. We experimentally distinguish ethylene populations associated with interlayer confinement, mesopore, and external surface adsorption. We show that chemical functionalization distinctly controls adsorption pathways: acid activation enhances total uptake by generating mesoporous adsorption sites and promoting partial interlayer intercalation, yielding capacities comparable to those of leading smectite-based adsorbents, while choline functionalization promotes preferential confinement and stabilization of guest molecules within the interlayer galleries. Advanced spectroscopic analysis provides molecular-level insight into confinement environments and interaction strengths. We also establish clear structure-property relationships by correlating uptake values derived from independent techniques, linking chemical modification, accessible adsorption domains, and retention behavior. These findings provide general design principles for tuning gas-solid interactions in functionalized layered silicates and highlight their potential as adaptable platforms for sustainable ethylene gas capture and selective adsorption technologies.

Ethylene adsorption mechanism↗
DOE OSTI2026

Confinement-Controlled Rearrangements in Dioxolane Upgrading on H-ZSM-5 Revealed by Periodic DFT

Zeolitic Brønsted acid sites catalyze carbocation rearrangements central to upgrading biomass-derived oxygenates. Here we elucidate the mechanism of dioxolane conversion to methyl ethyl ketone and isobutanal on H-ZSM-5 using periodic density functional theory on the MFI model, complemented by ab initio molecular dynamics to probe confinement effects. Dioxolane adsorption at the Brønsted site is followed by protonation-assisted ring opening to form an oxocarbenium intermediate stabilized by the deprotonated framework. From this common intermediate, selectivity is governed by two competing rearrangements, namely, the 1,2-hydride shift with a free-energy barrier of 18.05 kcal mol –1 at 498 K leading toward MEK, and the 1,2-methyl shift with a higher barrier of 25.40 kcal mol –1 leading toward isobutanal. The hydride-shift channel is kinetically preferred over the methyl-shift channel, lowering the isobutanal/MEK ratio below the 3:1 limit expected for equal branching. Adsorption thermodynamics further indicate stronger stabilization of MEK than isobutanal within ZSM-5 channels, suggesting that confinement-controlled binding can bias product distributions in addition to intrinsic rearrangement barriers. These results highlight how Brønsted acidity and pore confinement jointly shape the rearrangement landscape in MFI zeolites.

adsorption↗
DOE OSTI2025

Impact of Arsenic- and Indium-Terminated InGaAs Stressors on Carrier Confinement, Strain, Defects, and Transport Properties of Tensile-Strained Ge

Device-quality tensile-strained Ge (ε-Ge) grown on a large bandgap semiconductor with superior electrical and optical carrier confinement is essential for group-IV-based optoelectronics. Properties of ε-Ge active layers synthesized on In 0.24 Ga 0.76 As buffers with two different surface terminations─arsenic-rich and indium-rich─were experimentally demonstrated, highlighting the factors not considered in theoretical calculations. High-resolution X-ray diffraction and Raman spectroscopy analyses of these ε-Ge/In 0.24 Ga 0.76 As heterostructures confirmed the fully strained (1.6%) and partially relaxed (0.82%) nature of the ε-Ge bonded with arsenic-terminated (Ge As-terminated ) and indium-terminated (Ge In-terminated ) In 0.24 Ga 0.76 As stressors, respectively. High-resolution cross-sectional transmission electron microscopy showed a coherent, sharp, and fully strained ε-Ge/In 0.24 Ga 0.76 As heterointerface in the Ge As-terminated heterostructure, whereas microtwin defects were present in the Ge In-terminated heterostructure. These heterostructures were further characterized by evaluating the minority carrier lifetimes, high for Ge As-terminated (525 ns) and low for Ge In-terminated (69 ns), using the photoconductive decay technique. Moreover, band alignment was constructed using X-ray photoelectron spectroscopy, where the Ge As-terminated heterostructure revealed that both holes and electrons were confined within the ε-Ge active layer as a type-I band alignment with ΔE V, As-terminated = 0.22 eV and ΔE C,As-terminated = 0.38 eV. On the other hand, the Ge In-terminated heterostructure exhibited a type-II band alignment with ΔE V,In-terminated = – 0.02 eV and ΔE C,In-terminated = 0.53 eV. Furthermore, the magnetotransport properties revealed high mobility (321 cm 2 /(V s)) with single-electron transport in Ge As-terminated heterostructure and low mobility (3.34 cm 2 /(V s)) with multihole transport in the Ge In-terminated heterostructure. Therefore, preferring the ε-Ge on the arsenic-rich surface of In 0.24 Ga 0.76 As stressor over the indium-rich surface during material synthesis offers device-quality materials with high carrier lifetime and superior carrier confinement, which can provide an opportunity to fabricate efficient group-IV-based optoelectronic devices.

36 MATERIALS SCIENCE↗
DOE OSTI2026

Carrier Dynamics of Strongly Confined CsPbI 3 Nanowires

Here, we investigate the carrier dynamics of strongly confined cesium lead iodide (CsPbI 3 ) nanowires and compare them with weakly confined quantum dots (QDs) to understand how dimensionality affects recombination processes. Using time-resolved photoluminescence and ultrafast transient absorption spectroscopy, we find that nanowires exhibit a 5× faster recombination rate and more rapid carrier cooling than QDs. These differences are attributed to enhanced carrier interactions with trap states. Although nanowires exhibit slightly enhanced radiative rates as a result of confinement, their photoluminescence quantum yield remains relatively low, 23 ± 8%, due to competition from nonradiative recombination processes that occur at a faster rate. These findings highlight a dimensionality-dependent trade-off between radiative efficiency and nonradiative losses, providing insight into the limitations and opportunities for low-dimensional perovskite nanostructures. Our results establish design principles for tailoring CsPbI 3 nanocrystal dimensionality to optimize optical performance in optoelectronic applications such as LEDs and solar cells.

Oddo, Alexander M. [University of California, Berk↗
DOE OSTI2025

Crystallization of nanopore-confined imidazolium ionic liquids probed by temperature-resolved in situ grazing-incidence wide angle X-ray scattering (GIWAXS)

The crystallization behavior of ionic liquids (ILs) 1-butyl-3-methylimidazolium [BMIM] hexafluorophosphate [PF 6 ] and chloride [Cl] is investigated upon confinement in 2.3 or 8.2 nm diameter silica nanopore arrays, along with the effects of covalently modifying the pore walls with 1-(3-trimethoxysilylpropyl)3-methylimidazolium [TMS-MIM] + groups. In situ grazing-incidence wide angle x-ray scattering (GIWAXS) is performed during heating from as low as -110 °C to room temperature. Partially ordered “nanodomains” are observed in both ILs in the bulk molten state, but they are disrupted by nanoconfinement. Melting point depression consistent with capillary effects is observed for [BMIM][PF 6 ] in 2.3 nm pores. However, the melting point is elevated for [BMIM][PF 6 ] in 8.2 nm pores, which provide sufficient space to stabilize the crystalline phase. For [BMIM][Cl], crystallization is observed only in 8.2 nm bare silica pores, but the melting point is severely depressed. Tethering with IL-like [TMS-MIM + ] also promotes the crystallization of [BMIM][PF 6 ], resulting in elevated melting points. The combined effects of a larger pore size and pore surface tethering on [BMIM][PF 6 ] result in a single stable crystal phase that persists from -140 °C to 25 °C (vs. the bulk melting point of -11 °C). These results show that when ILs are used in confined systems, complex crystallization behavior can emerge depending on the counterion, pore size, and surface modification that require consideration of ion layering in the confined space in addition to surface free energy effects.

He, Yuxin [University of Kentucky, Lexington, KY (↗
DOE OSTI2024

Fast ion confinement in the presence of core magnetic islands in Wendelstein 7-X

The effect of magnetic islands in the core region of Wendelstein 7-X (W7-X) on fast ion confinement is explored through simulations with the BEAMS3D code. A magnetic configuration where the n/m = 5/5 island chain is shifted to r/a ~ 0.7 allows the exploration of core island physics in W7-X. The control coil system on W7-X allows the tuning of the island size either increasing the island width or decreasing it. A coupling of the BEAMS3D code to the FIELDLINES code provides a versatile mechanism for incorporating magnetic islands and stochastic regions into the BEAMS3D code. Collisionless simulations suggest that the presence of core islands degrade the confinement of passing particles in the region of the island chain. Full neutral beam simulations of W7-X show a similar behavior with confinement decreasing as the island width is increased. Comparisons between a vacuum magnetic field and low beta HINT2 simulation are made showing similar fast ion behavior. Measurements of lost fast ions in W7-X confirm this trend with the control coil suppressed island configuration showing lower losses than that with no control coils applied. Simulations of fast ion wall loads are performed suggesting no drastic change in loss pattern and a slight reduction in losses with minimized islands.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2026

Achievement of a high-density, high-confinement, and high-beta tokamak plasma regime in DIII-D, and implications for a lower-current path for ITER and FPP

Experiments on DIII-D have demonstrated a density-confinement synergy that enables sustainment of high performance in a previously unattained parameter regime of simultaneous very high energy confinement quality (H 98y2 ≥ 1.5), very high line-average density Greenwald fraction (ƒ Gr = πa 2 < n >/I P ≥ 1.4), and high toroidal beta (β T ≥ 3%). Tokamak operation in this regime is essential for a compact steady-state FPP, as well as for Q=10 with 500 MW of fusion power in ITER at I P << 15 MA. These experiments leveraged the knowledge that, in the high-poloidal-beta (β P ) regime, impurity and density gradients can enhance turbulence stabilization caused by high α MHD (α MHD ~(dβ P )⁄dr). This was described by theoretical predictions and gyrokinetic transport simulations [M.T. Kotschenreuther et al, 2024 Nucl. Fusion, 64 076033], and later confirmed by experiments on DIII-D [S. Ding et al, 2024 Nature 629 555]. To increase both β P and β T , the new experiments increased the ideal-wall stability β N -limit by using a smaller plasma-outer wall distance and higher triangularity in the plasma cross section (top/bottom average δ~0.9), enabled by the recent “shape & volume rise” (SVR) modification to the DIII-D divertor. The higher triangularity also contributed to achieving higher ƒ Gr by enabling higher pedestal density. At high density, the pedestal is ballooning limited and exhibits small and frequent ELMs, while the divertor is near detachment even without any impurity seeding. High plasma performance was attained and sustained reproducibly, with the eventual terminations brought about by an MHD mode destabilized as the current profile slowly continued to evolve. A path to stationary fully noninductive operation might include ECH injection to reduce both core impurity accumulation and the electron collisionality, thus increasing the bootstrap current. These experiments provide the first experimental demonstration of the ƒ Gr , H 98y2 , and β T values required simultaneously for ITER Q = 10 at I P < 10 MA, pointing to practical ways to improve the energy confinement in a fusion reactor.

Garofalo, Andrea M. [General Atomics, San Diego, C↗
DOE OSTI2025

Software For Advanced Large-scale Analysis Of Magnetic Confinement For Numerical Design, Engineering & Research (salamander)

As magnetic confinement fusion energy gains traction internationally to enable abundant energy production, designing components for fusion systems is a pressing challenge. During the planned lifetime of a fusion device, components evolve in extreme environments and must withstand large, repeated thermal loads and bombardment by 14 MeV neutrons, plasma ions, and neutral particles (deuterium, tritium, and helium), corrosive conditions, etc. All these physical processes take place simultaneously, interact in intricate ways, and impose important constraints that can affect performance. Experimental data is rare and costly to obtain, making design particularly challenging. Predictive computational frameworks must be an integral part of an accelerated and cost-effective design process by modeling fusion system performance in simulated environments. To better understand component degradation and operational impacts on their performance, the Software for Advanced Large-scale Analysis of MAgnetic confinement for Numerical Design, Engineering & Research (SALAMANDER) is designed as an open-source, fully integrated, multiphysics, multiscale, NQA-1 compliant framework facilitating 3D, high-fidelity fusion system modeling. To that end, SALAMANDER is a MOOSE-based framework, and therefore leverages MOOSE upstream libraries such as PETSc and libMesh to deliver sophisticated finite element, finite volume, and nonlinear solver technology for fusion energy simulations. SALAMANDER couples MOOSE physics module capabilities—such as thermal hydraulics, heat conduction, Navier-Stokes, and thermomechanics—with tritium transport via TMAP8, neutronics via Cardinal, and nascent particle-in-cell capabilities. Direct simulation Monte Carlo methods will be used to address neutral transport near the walls. By coupling all these physics in an integrated application, SALAMANDER will enable high-fidelity modeling of irradiation levels and plasma exposure conditions of plasma facing components and their impact on heat and tritium distributions, as well as the resulting mechanical constraints experienced by the plasma facing components and performance of blanket systems. Furthermore, SALAMANDER will be particularly suited for engineering studies thanks to the stochastic tool module readily available in MOOSE, allowing for extended uncertainty quantification and risk analysis studies. It is also able to use computer-aided design (CAD) meshes to model complex geometries, which is indispensable for fusion systems. SALAMANDER therefore supports design, safety, engineering, and research projects for magnetic confinement fusion systems

Simon, Pierre-Clement [Idaho National Laboratory (↗
DOE OSTI2024

Higgs-confinement transitions in QCD from symmetry protected topological phases

In gauge theories with fundamental matter there is typically no sharp way to distinguish confining and Higgs regimes, e.g. using generalized global symmetries acting on loop order parameters. It is standard lore that these two regimes are continuously connected, as has been explicitly demonstrated in certain lattice and continuum models. We point out that Higgsing and confinement sometimes lead to distinct symmetry protected topological (SPT) phases -- necessarily separated by a phase transition -- for ordinary global symmetries. We present explicit examples in 3+1 dimensions, obtained by adding elementary Higgs fields and Yukawa couplings to QCD while preserving parity P and time reversal T. In a suitable scheme, the confining phases of these theories are trivial SPTs, while their Higgs phases are characterized by non-trivial P- and T-invariant theta-angles θ f , θ g = π for flavor or gravity background gauge fields, i.e. they are topological insulators or superconductors. Finally, we consider conventional three-flavor QCD (without elementary Higgs fields) at finite U(1) B baryon-number chemical potential μ B , which preserves P and T. At very large μ B , three-flavor QCD is known to be a completely Higgsed color superconductor that also spontaneously breaks U(1) B . We argue that this high-density phase is in fact a gapless SPT, with a gravitational theta-angle θ g = π that safely co-exists with the U(1) B Nambu-Goldstone boson. We explain why this SPT motivates unexpected transitions in the QCD phase diagram, as well as anomalous surface modes at the boundary of quark-matter cores inside neutron stars.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2025

Confined and deconfined chaos in classical spin systems

Weakly perturbed integrable many-body systems are typically chaotic, and thermal at late times. However, there are distinct relationships between the timescales for thermalization and chaos. The typical relationship is confined chaos: when trajectories are still confined to regions in phase space with constant conserved quantities (actions), the conjugate angle variables are already unstable. Chaotic instabilities thus far precede thermalization. In a different relationship, which we term deconfined chaos, chaotic instabilities and thermalization occur on the same timescale. We investigate these two qualitatively distinct scenarios through numerical and analytical studies of two perturbed integrable classical spin models: the Ishimori spin chain (confined chaos), and the central spin model with XX interactions (deconfined chaos). We analytically establish (super)-integrability in the latter model in a microcanonical shell. Deconfined chaos emerges through the separation of phase space into large quasi-integrable regions and a thin chaotic manifold. The latter leads to chaos and thermalization on the fastest possible timescale, which is proportional to the inverse perturbation strength. This behavior is reminiscent of the quantum SYK models and strange metals.

Chaotic Dynamics (nlin.CD)↗
DOE OSTI2024

Lateral Confinement in 2D Nanoplatelets: A Strategy to Expand the Colloidal Quantum Engineering Toolbox

Among colloidal nanocrystals, 2D nanoplatelets offer a unique set of properties with exceptionally narrow luminescence and low lasing thresholds. Furthermore, their anisotropic shape expands the playground for the complex design of heterostructures where spectra but also scattering rates can be engineered. A challenge that still remains is to combine shell growth which makes NPLs stable, with spectral tunability. Indeed, most reported shelled nanoplatelets end up being red emitters due to a loss of quantum confinement. Here, the combination of both lateral and in-plane confinements within a single heterostructure is explored. A CdS/CdSe/CdS/CdZnS core–crown–crown shell structure that enables yellow emission is grown and that is responsive to a large range of excitation including visible photons, X-ray photons, electron beams, and electrical excitations. k.p simulations predict that emission tunability of up to several 100 s of meV can be obtained in ideal structures. This material also displays stimulated emission resulting from bi-exciton emission with a low threshold. Once integrated into an LED stack, this material is compatible with sub-bandgap excitation and exhibits high luminance. Scaling of the electroluminescence properties by downsizing the pixel size is also investigated.

2D materials↗
DOE OSTI2025

Confinement performance predictions for a high field axisymmetric tandem mirror

This paper presents a Hammir tandem mirror confinement performance analysis based on Realta Fusion’s first-of-a-kind model for axisymmetric magnetic mirror fusion performance. This model uses an integrated end plug simulation model including, heating, equilibrium and transport combined with a new formulation of the plasma operation contours (POPCONs) technique for the tandem mirror central cell. Using this model in concert with machine learning optimization techniques, it is shown that an end plug utilizing high temperature superconducting magnets and modern neutral beams enables a classical tandem mirror pilot plant producing a fusion gain Q > 5. The approach here represents an important advance in tandem mirror design. The high-fidelity end plug model enables calculations of heating and transport in the highly non-Maxwellian end plug to be made more accurately. The detailed end plug modelling performed in this work has highlighted the importance of classical radial transport and neutral beam absorption efficiency on end plug viability. The central cell POPCON technique allows consideration of a wide range of parameters in the relatively simple near-Maxwellian central cell, facilitating the selection of more optimal central cell plasmas. These advances make it possible to find more conservative classical tandem mirror fusion pilot plant operating points with lower temperatures, neutral beam energies and end plug performance requirements than designs in the literature. Despite being more conservative, it is shown that these operating points have sufficient confinement performance to serve as the basis of a viable fusion pilot plant provided that they can be stabilized against magnetohydrodynamic and trapped particle modes.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2026

Non-dimensional confinement scaling in similar negative triangularity plasmas on the DIII-D and TCV tokamaks

Similarity experiments were performed on the DIII-D and TCV tokamaks to explore the scaling of energy confinement in negative triangularity (NT) plasmas using non-dimensional variables. Near up-down symmetric plasmas with large top-bottom averaged NT were created in a lower single null configuration, with the shape of the separatrix being closely matched between the two devices. The normalized energy confinement is found to weakly improve at increasing collisionality and, between the two devices, shows a machine size scaling behavior between Bohm and gyro-Bohm. Engineering scaling on a large DIII-D dataset is in agreement with the non-dimensional experiment.

confinement scaling↗
DOE OSTI2025

Inertial Confinement Fusion: Status and Challenges

While a variety of laboratory-based fusion schemes have been studied for decades, the only fusion scheme yet to demonstrate fusion ignition and significant energy gain has been X-ray-driven inertially confined fusion. Ignition was demonstrated to occur at the thermodynamic conditions where it had long been expected, but the energy required for the implosion system to reach these conditions was more than projected years ago. This short review gives a status update on the three principal inertial confinement fusion schemes and research challenges going forward.

gain↗