Stellarator-tokamak energy confinement comparison based on ASDEX Upgrade and Wendelstein 7-X hydrogen plasmas

Stroth, U.; Fuchert, G.; Beurskens, M.; Birkenmeier, G.; Schneider, P. A.; Scott, E. R.; Brunner, K. J.; Günzkofer, Florian; Hacker, P.; Kardaun, O.; Knauer, J.; Zhang, D.; Team, Mst

doi:10.1088/1741-4326/abbc4a

Cited by 10 publications

(8 citation statements)

References 38 publications

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“…As the plasma volume decreases from V max to V min (with fixed absorbed power), the power deposition to the electrons increases in proportion to the volume ratio V max /V min . At the same time, the energy confinement worsens in the same ratio [3], and this experimental fact coincides with the predictions of the STMCP model. As a result, both processes compensate mutually and the electron temperature remains unchanged (in normalized coordinates, of course).…”

Section: Discussionsupporting

confidence: 87%

“…Indeed, using the ratio q(a) = 1/ι -(a) in the scaling law, one can see that the stellarator transport is much worse than the tokamak one. Analysis of the energy transport in a tokamak using a critical gradient transport model [2] showed that the right hand side of this ratio should be increased by some factor [3]. In [4] we determine this factor and use the following relation:…”

Section: Introductionmentioning

confidence: 99%

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Absorption efficiency of the second harmonic ECRH waves and comparative plasma transport simulation in the TJ-II stellarator and T-10 tokamak

Dnestrovskij¹,

Melnikov²,

López‐Bruna³

et al. 2022

Plasma Phys. Control. Fusion

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The concept of equivalent tokamak and stellarator discharges with the same electron and ion temperatures and with full absorption of the injected ECRH power was introduced in Dnestrovskij Yu N et al 2021 Plasma Phys. Control. Fusion 63 055012. In the present paper, the concept of the discharges equivalence is extended to the case of partial ECRH power absorption. The conditions of discharges equivalence for this case are formulated. It is shown that in equivalent discharges not only the electron temperatures, but also the absorbed powers are the same. Examples of equivalent experimental discharges of the TJ-II stellarator and simulated discharges of the T-10 tokamak with partial ECRH power absorption are studied. Absorbed ECRH power and energy confinement time are found for TJ-II low-density shots heated with ECRH only.

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Section: Discussionsupporting

confidence: 87%

Section: Introductionmentioning

confidence: 99%

Absorption efficiency of the second harmonic ECRH waves and comparative plasma transport simulation in the TJ-II stellarator and T-10 tokamak

Dnestrovskij¹,

Melnikov²,

López‐Bruna³

et al. 2022

Plasma Phys. Control. Fusion

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“…Consequently, whether the aforementioned dissimilarities are the result of different optimisation procedures or are inherent to the physics of the two magnetic configurations remains to be established. On the other hand, the obtained results and the comparison with the L mode Tokamak support the opinion that turbulence transport is the dominant effect in determining the Stellarator energy confinement time, once the devices are reasonably optimised for neoclassical transport [32].…”

Section: Comparison With the Tokamak In L Mode Of Confinementsupporting

confidence: 68%

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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“…The small difference is that the power degradation α P of metallic devices is not in the range between −0.60 and −0.53 (−0.66 in NBI-LHW and −0.67 in ECRH-LHW). The true dependence of plasma confinement on plasma shape and configuration has been studied for many years [31][32][33]. The κ a dependency in most of single devices was not given in [23], except 1.112 in JET-C and 0.86 in NSTX.…”

Section: Comparison With Recent Scalings From the Itpa Global H-mode ...mentioning

confidence: 99%

The scalings of the thermal energy confinement time in EAST H-mode plasmas

et al. 2023

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TThis paper describes scalings of the H-mode confinement database of NBI-LHW and ECRH-LHW plasmas in the EAST tokamak. The fundamental information of the EAST H-mode database and the details of calculation of the thermal energy confinement time in EAST are presented. The result of the scaling model τ_(E,EASTS,H,NBI-LHW) of the thermal energy confinement time in NBI-LHW plasmas with root-mean-square-error RMSE=5.5%, compared with the multi-machine scaling model τ_(th,98y2) derived from the multi-machine database (mainly NBI heating) with RMSE=12.9%, is obtained. The scaling τ_(E,EAST,H,NBI-LHW) presents a similar dependency on plasma current and power loss and a lower dependency on plasma density and elongation, but stronger dependency on toroidal field on the contrary to the positive dependency in τ_(th,98y2). The scaling τ_(E,EAST,H,ECRH-LHW) demonstrates a similar dependency on power loss and plasma current and lower dependency on plasma density, but a negative dependency with large error bars on elongation compared with τ_(E,EAST,H,NBI-LHW) in NBI-LHW plasmas. The comparison of EAST models with the latest model ITPA20-IL shows a similar engineering dependency on plasma current, power loss and plasma density, but opposite dependency on toroidal field.

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Stellarator-tokamak energy confinement comparison based on ASDEX Upgrade and Wendelstein 7-X hydrogen plasmas

Cited by 10 publications

References 38 publications

Absorption efficiency of the second harmonic ECRH waves and comparative plasma transport simulation in the TJ-II stellarator and T-10 tokamak

Absorption efficiency of the second harmonic ECRH waves and comparative plasma transport simulation in the TJ-II stellarator and T-10 tokamak

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

The scalings of the thermal energy confinement time in EAST H-mode plasmas

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