Assessment of Global Stellarator Confinement: Status of the International Stellarator Confinement Database

Dinklage, A.; Ascasíbar, E.; Beidler, C. D.; Brakel, R.; Geiger, J.; Harris, J. H.; Kus, A.; Murakami, S.; Okamura, S.; Preuss, R.; Sano, F.; Stroth, U.; Suzuki, Y.; Talmadge, J. N.; Tribaldos, V.; Watanabe, K. Y.; Weller, A.; Yamada, H.; Yokoyama, M.

doi:10.13182/fst07-a1281

Cited by 15 publications

(22 citation statements)

References 20 publications

(23 reference statements)

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“…Second, the TJ-II central electron temperature in that density range is lower than in the ECRH phase, and ranging between 400 and 250 eV, which is very convenient since the C 4+ ion emits from the plasma interior and is consequently a good probe of this effect in the core. During the ECRH phase it is indispensable to invert the chord averaged results in order to obtain local values, increasing the error propagation in the determination of the turbulence level through (1). At central electron temperatures ≤ 100 eV the effect is difficult to observe.…”

Section: Correlation With Confinement Featuresmentioning

confidence: 99%

“…The confinement scaling laws in stellarators depict general trends [1], which need to be understood from basic mechanism accounting for them. Global confinement time studies in TJ-II permits its parameterization in the same way as data from other devices, but as anywhere, its behavior with density, absorbed power etc., is difficult to understand from the point of view of neoclassical or any other theory.…”

Section: Introductionmentioning

confidence: 99%

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The Level of Non‐Thermal Velocity Fluctuations Deduced From Doppler Spectroscopy and their Role on TJ‐II Confinement

Zurro¹,

Baciero

Liniers

et al. 2010

Contrib. Plasma Phys.

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The goal of this investigation is to study the level of velocity fluctuations in different scenarios of the TJ-II stellarator. The method consists in measuring the apparent Doppler temperature of C 4+ and protons with high spectral resolution techniques with spatial resolution. The level of turbulent velocities has been deduced from the difference observed between the apparent temperature of both species, following a method previously presented. The study of this difference, as a function of plasma density and injected power, provides a way to explore if this turbulence plays any role in the confinement of the hot TJ-II plasma.

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Section: Correlation With Confinement Featuresmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

The Level of Non‐Thermal Velocity Fluctuations Deduced From Doppler Spectroscopy and their Role on TJ‐II Confinement

Zurro¹,

Baciero

Liniers

et al. 2010

Contrib. Plasma Phys.

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“…The International Stellarator Confinement DB comprises entries from the eight most relevant machines operated in the world at the time of its constitution: ATF, CHS, Heliotron E, Heliotron J, LHD, TJ-II, W7-A, and W7-AS. For the sake of comparison with the literature and with specific experiments [20,21], the same variables and selection criteria reported in [22] for the derivation of the ISS04 scaling have been adopted (ISHCDB 26). An overview of the analysed database is provided in Table 1.…”

Section: The International Stellarator Confinement Database and The I...mentioning

confidence: 99%

Considerations on Stellarator’s Optimization from the Perspective of the Energy Confinement Time Scaling Laws

et al. 2022

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The Stellarator is a magnetic configuration considered a realistic candidate for a future thermonuclear fusion commercial reactor. The most widely accepted scaling law of the energy confinement time for the Stellarator is the ISS04, which employs a renormalisation factor, fren, specific to each device and each level of optimisation for individual machines. The fren coefficient is believed to account for higher order effects not ascribable to variations in the 0D quantities, the only ones included in the database used to derive ISS04, the International Stellarator Confinement database. This hypothesis is put to the test with symbolic regression, which allows relaxing the assumption that the scaling laws must be in power monomial form. Specific and more general scaling laws for the different magnetic configurations have been identified and perform better than ISS04, even without relying on any renormalisation factor. The proposed new scalings typically present a coefficient of determination R2 around 0.9, which indicates that they basically exploit all the information included in the database. More importantly, the different optimisation levels are correctly reproduced and can be traced back to variations in the 0D quantities. These results indicate that fren is not indispensable to interpret the data because the different levels of optimisation leave clear signatures in the 0D quantities. Moreover, the main mechanism dominating transport, in reasonably optimised configurations, is expected to be turbulence, confirmed by a comparative analysis of the Tokamak in L mode, which shows very similar values of the energy confinement time. Not resorting to any renormalisation factor, the new scaling laws can also be extrapolated to the parameter regions of the most important reactor designs available.

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“…Model plasma profiles Missing a complete model for particle and energy sources and transport, we fix the shape of the density Appendix A. 2…”

Section: Appendix a Definitions And Conventionsmentioning

confidence: 99%

Physics design point of high-field stellarator reactors

Alonso,

Calvo,

Carralero

et al. 2021

Preprint

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The ongoing development of electromagnets based on High Temperature Superconductors has led to the conceptual exploration of high-magnetic-field fusion reactors of the tokamak type, operating at on-axis fields above 10 T. In this work we explore the consequences of the potential future availability of high-field three-dimensional electromagnets on the physics design point of a stellarator reactor. We find that, when an increase in the magnetic field strength B is used to maximally reduce the device linear size R ∼ B −4/3 (with otherwise fixed magnetic geometry), the physics design point is largely independent of the chosen field strength/device size. A similar degree of optimization is to be imposed on the magnetohydrodynamic, transport and fast ion confinement properties of the magnetic configuration of that family of reactor design points. Additionally, we show that the family shares an invariant operation map of fusion power output as a function of the auxiliary power and relative density variation. The effect of magnetic field over-engineering is inspected and shown to alleviate some optimization requirements while toughening others. * The helically symmetric experiment (HSX) has been shown to possess a resilient localised pattern of field-line strike points [10], but a divertor was not foreseen in its construction. * This is not to say that deviations in particular parametric dependencies of the neoclassical and turbulence diffusivities with respect to the gyro-Bohm diffusivity are excluded. The neoclassical 1/ν limit discussed before is an example of this.

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Assessment of Global Stellarator Confinement: Status of the International Stellarator Confinement Database

Cited by 15 publications

References 20 publications

The Level of Non‐Thermal Velocity Fluctuations Deduced From Doppler Spectroscopy and their Role on TJ‐II Confinement

The Level of Non‐Thermal Velocity Fluctuations Deduced From Doppler Spectroscopy and their Role on TJ‐II Confinement

Considerations on Stellarator’s Optimization from the Perspective of the Energy Confinement Time Scaling Laws

Physics design point of high-field stellarator reactors

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