| 1. |
- Fenstermacher, M.E., et al.
(författare)
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DIII-D research advancing the physics basis for optimizing the tokamak approach to fusion energy
- 2022
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Ingår i: Nuclear Fusion. - : IOP Publishing. - 0029-5515 .- 1741-4326. ; 62:4
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Tidskriftsartikel (refereegranskat)abstract
- DIII-D physics research addresses critical challenges for the operation of ITER and the next generation of fusion energy devices. This is done through a focus on innovations to provide solutions for high performance long pulse operation, coupled with fundamental plasma physics understanding and model validation, to drive scenario development by integrating high performance core and boundary plasmas. Substantial increases in off-axis current drive efficiency from an innovative top launch system for EC power, and in pressure broadening for Alfven eigenmode control from a co-/counter-I p steerable off-axis neutral beam, all improve the prospects for optimization of future long pulse/steady state high performance tokamak operation. Fundamental studies into the modes that drive the evolution of the pedestal pressure profile and electron vs ion heat flux validate predictive models of pedestal recovery after ELMs. Understanding the physics mechanisms of ELM control and density pumpout by 3D magnetic perturbation fields leads to confident predictions for ITER and future devices. Validated modeling of high-Z shattered pellet injection for disruption mitigation, runaway electron dissipation, and techniques for disruption prediction and avoidance including machine learning, give confidence in handling disruptivity for future devices. For the non-nuclear phase of ITER, two actuators are identified to lower the L-H threshold power in hydrogen plasmas. With this physics understanding and suite of capabilities, a high poloidal beta optimized-core scenario with an internal transport barrier that projects nearly to Q = 10 in ITER at ∼8 MA was coupled to a detached divertor, and a near super H-mode optimized-pedestal scenario with co-I p beam injection was coupled to a radiative divertor. The hybrid core scenario was achieved directly, without the need for anomalous current diffusion, using off-axis current drive actuators. Also, a controller to assess proximity to stability limits and regulate β N in the ITER baseline scenario, based on plasma response to probing 3D fields, was demonstrated. Finally, innovative tokamak operation using a negative triangularity shape showed many attractive features for future pilot plant operation.
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| 2. |
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| 3. |
- Järleblad, H., et al.
(författare)
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A framework for synthetic diagnostics using energetic-particle orbits in tokamaks
- 2024
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Ingår i: Computer Physics Communications. - : Elsevier. - 0010-4655 .- 1879-2944. ; 294
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Tidskriftsartikel (refereegranskat)abstract
- In fusion plasma physics, the large-scale trajectories of energetic particles in magnetic confinement devices are known as orbits. To effectively and efficiently be able to work with orbits, the Orbit Weight Computational Framework (OWCF) was developed. The OWCF constitutes a set of scripts, functions and applications capable of computing, visualizing and working with quantities related to fast-ion (FI) orbits in toroidally symmetric fusion devices. The current version is highly integrated with the DRESS code, which enables the OWCF to compute and analyze the orbit sensitivity for arbitrary neutron- and gammadiagnostics. However, the framework is modular in the sense that any future codes (e.g. FIDASIM) can be easily integrated. The OWCF can also compute projected velocity spectra for FI orbits, which play a key role in many FI diagnostics. Via interactive applications, the OWCF can function both as a tool for investigative research but also for teaching. The OWCF will be used to analyze and simulate the diagnostic results of current and future fusion experiments such as ITER. The orbit weight functions computed with the OWCF can be used to reconstruct the FI distribution in terms of FI orbits from experimental measurements using tomographic inversion.
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| 4. |
- Järleblad, H., et al.
(författare)
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Fast-ion orbit origin of neutron emission spectroscopy measurements in the JET DT campaign
- 2024
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Ingår i: Nuclear Fusion. - : Institute of Physics Publishing (IOPP). - 0029-5515 .- 1741-4326. ; 64:2
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Tidskriftsartikel (refereegranskat)abstract
- In the JET DTE2 deuterium-tritium campaign, neutron diagnostics were employed to measure 14 MeV neutrons originating from D(T,n)4He reactions. In discharge 99965, a diamond matrix detector (KM14) and a magnetic proton recoil (MPRu) detector with a vertical and an oblique line-of-sight were used, respectively. At the timepoints of interest, a significant decrease in the expected diagnostic signals can be observed as electromagnetic wave heating in the ion cyclotron range of frequencies (ICRF) is switched off. Utilizing only TRANSP simulation data, the fast-ion distribution is found to have been likely composed mostly of trapped orbits. In contrast, analysis performed using orbit weight functions revealed that the majority of neutrons in the KM14 MeV and MPRu cm measurement bins are to have originated from fast deuterium ions on co-passing orbits. This work explains the perhaps surprising results and shows that the relative signal decrease as ICRF heating is switched off is largest for counter-passing orbits. Finally, for the magnetic equilibria of interest, it is shown how stagnation orbits, corresponding to % of the fast-ion distribution, were completely unobservable by the KM14 diagnostic.
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| 5. |
- Järleblad, H., et al.
(författare)
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Fast-ion orbit sensitivity of neutron and gamma-ray diagnostics for one-step fusion reactions
- 2022
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Ingår i: Nuclear Fusion. - : Institute of Physics (IOP). - 0029-5515 .- 1741-4326. ; 62:11
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Tidskriftsartikel (refereegranskat)abstract
- Fast ions in the MeV-range can be diagnosed by neutron emission spectroscopy (NES) and gamma-ray spectroscopy (GRS). In this work, we present orbit weight functions for one-step fusion reactions, using NES and GRS diagnostics on perpendicular and oblique lines-of-sight (LOS) at Joint European Torus (JET) as examples. The orbit weight functions allow us to express the sensitivities of the diagnostics in terms of fast-ion (FI) orbits and can be used to swiftly reproduce synthetic signals that have been computed by established codes. For diagnostically relevant neutron energies for the D(D, n)He-3 reaction, the orbit sensitivities of the NES diagnostics follow a predictable pattern. As the neutron energy of interest increases, the pattern shifts upwards in FI energy. For the GRS diagnostic and the T(p,gamma)He-4 reaction, the orbit sensitivity is shown to be qualitatively different for red-shifted, blue-shifted and nominal gamma birth energies. Finally, we demonstrate how orbit weight functions can be used to decompose diagnostic signals into the contributions from different orbit types. For a TRANSP simulation of the JET discharge (a three-ion ICRF scenario) considered in this work, the NES signals for both the perpendicular and oblique LOS are shown to originate mostly from co-passing orbits. In addition, a significant fraction of the NES signal for the oblique LOS is shown to originate from stagnation orbits.
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| 6. |
- Järleblad, H., et al.
(författare)
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Fast-ion orbit sensitivity of neutron emission spectroscopy diagnostics
- 2021
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Ingår i: Review of Scientific Instruments. - : American Institute of Physics (AIP). - 0034-6748 .- 1089-7623. ; 92:4
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Tidskriftsartikel (refereegranskat)abstract
- Fast ions in fusion plasmas often leave characteristic signatures in the plasma neutron emission. Measurements of this emission are subject to the phase-space sensitivity of the diagnostic, which can be mapped using weight functions. In this paper, we present orbit weight functions for the TOFOR and NE213 neutron diagnostics at the Joint European Torus, mapping their phase-space sensitivity in 3D orbit space. Both diagnostics are highly sensitive to fast ions that spend a relatively large fraction of their orbit transit times inside the viewing cone of the diagnostic. For most neutron energies, TOFOR is found to be relatively sensitive to potato orbits and heavily localized counter-passing orbits, as well as trapped orbits whose "banana tips" are inside the viewing cone of TOFOR. For the NE213-scintillator, the sensitivity is found to be relatively high for stagnation orbits.
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| 7. |
- Rud, M., et al.
(författare)
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Diagnostic weight functions in constants-of-motion phase-space
- 2024
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Ingår i: Nuclear Fusion. - : Institute of Physics Publishing (IOPP). - 0029-5515 .- 1741-4326. ; 64:3
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Tidskriftsartikel (refereegranskat)abstract
- The fast-ion phase-space distribution function in axisymmetric tokamak plasmas is completely described by the three constants of motion: energy, magnetic moment and toroidal canonical angular momentum. In this work, the observable regions of constants-of-motion phase-space, given a diagnostic setup, are identified and explained using projected velocities of the fast ions along the diagnostic lines-of-sight as a proxy for several fast-ion diagnostics, such as fast-ion D alpha spectroscopy, collective Thomson scattering, neutron emission spectroscopy and gamma-ray spectroscopy. The observable region in constants-of-motion space is given by a position condition and a velocity condition, and the diagnostic sensitivity is given by a gyro-orbit and a drift-orbit weighting. As a practical example, 3D orbit weight functions quantifying the diagnostic sensitivity to each point in phase-space are computed and investigated for the future COMPASS-Upgrade and MAST-Upgrade tokamaks.
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| 8. |
- Schmidt, B. S., et al.
(författare)
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4D and 5D phase-space tomography using slowing-down physics regularization
- 2023
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Ingår i: Nuclear Fusion. - : Institute of Physics (IOP). - 0029-5515 .- 1741-4326. ; 63:7
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Tidskriftsartikel (refereegranskat)abstract
- We compute reconstructions of 4D and 5D fast-ion phase-space distribution functions in fusion plasmas from synthetic projections of these functions. The fast-ion phase-space distribution functions originating from neutral beam injection (NBI) at TCV and Wendelstein 7-X (W7-X) at full, half, and one-third injection energies can be distinguished and particle densities of each component inferred based on 20 synthetic spectra of projected velocities at TCV and 680 at W7-X. Further, we demonstrate that an expansion into a basis of slowing-down distribution functions is equivalent to regularization using slowing-down physics as prior information. Using this technique in a Tikhonov formulation, we infer the particle density fractions for each NBI energy for each NBI beam from synthetic measurements, resulting in six unknowns at TCV and 24 unknowns at W7-X. Additionally, we show that installing 40 LOS in each of 17 ports at W7-X, providing full beam coverage and almost full angle coverage, produces the highest quality reconstructions.
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