Fusion burn equilibria sensitive to the ratio between energy and helium transport

Jakobs, MA Merlijn; Cardozo, NJ Niek Lopes; Jaspers, Rje Roger

doi:10.1088/0029-5515/54/12/122005

Cited by 14 publications

(11 citation statements)

References 15 publications

(26 reference statements)

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“…The self-consistent numerical investigations of the effect of helium in burning plasmas and its removal are reported in Refs. [4][5][6][7][8][9][10]. There are He confinement regimes for which the net output power is tightly circumscribed [3].…”

Section: Introductionmentioning

confidence: 99%

Analyses of the influence of the recycling coefficient on He confinement in DEMO reactor

Ivanova‐Stanik

Poradziński

Zagórski

et al. 2019

Fusion Engineering and Design

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This work describes integrated numerical modelling applied to DEMO discharges with tungsten wall and divertor, using the COREDIV code, which self-consistently solves 1D radial transport equations of plasma and impurities in the core region and 2D multi-fluid transport in the SOL. The model is self-consistent with respect to both the effects of impurities on the α-power level and the interaction between seeded (Ar) and intrinsic impurities (tungsten, helium). This work is to analyse the influence of the helium and hydrogen recycling on the He confinement time in DEMO reactor. Simulations have been done for argon seeding puff 5.0x10 21 1/s. It is found that recycling coefficient of helium have strong influence on the He confinement time, which increases from 7.25s to 26.9s going from lowest to highest recycling coefficient, but it has small influence on the effective charge state and radiation in the SOL. Alpha power decreases only by about 20%, which is the effect of main plasma dilution.

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Section: Introductionmentioning

confidence: 99%

Analyses of the influence of the recycling coefficient on He confinement in DEMO reactor

Ivanova‐Stanik

Poradziński

Zagórski

et al. 2019

Fusion Engineering and Design

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“…These results assure confidence on the current line-ratio diagnostic model where electron-excitation emission is assumed to be dominant 4 , and recombination effects are eliminated by emission background subtraction. 7,23 However, due to the higher contribution to the neutral helium population that CX makes compared to electron recombination, CX must be included as an important source in plasma ionic fractional abundance calculations, as well as in heliumash transport studies in fusion reactors, 24 and helium removal in tokamaks. 25…”

Section: Discussionmentioning

confidence: 99%

Evaluation of emission contributions from charge-exchange between the excited states of deuterium with He+ during diagnostic of thermal helium gas beam injection and laser-induced fluorescence

et al. 2019

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Emission contributions from charge-exchange of excited deuterium (n = 2, 3) with He + are evaluated in a 1-D kinetic collisional radiative model (CRM) in order to analyze their effects on the Thermal Helium Beam (THB) line-ratio diagnostic on ASDEX Upgrade (AUG), and Laser Induced Fluorescence (LIF) He I density measurements in ITER. Recent charge-exchange calculations show that cross-sections from excited deuterium (n = 2, 3) with He + are over 4-orders of magnitude higher than those from the ground state (n = 1), and occur at very low energies where they are more likely to interact with the thermal He + ions introduced by ionization of the diagnostic helium gas-puff injection. Higher densities of excited deuterium are typically present in the Scrape-Off Layer (SOL), Divertor, and Edge regions of Tokamaks, where the LIF and THB helium diagnostic are typically used for n HeI and simultaneous determination of electron temperatures and densities, and where contributions from charge-exchange emission may offset these values if not taken into account. The analysis presented in this work shows that due to the higher density of deuterium in the ground rather than in excited states, and the divergent behavior of deuterium and He + density profiles along the SOL and Edge regions, the deuterium-He + charge-exchange contributions to the helium puff emission are 3-orders of magnitude lower than those from electron-impact excitation. Similar plasma conditions are expected in the ITER divertor, with the exception that in the area near the strike-points and targets the electron temperature is not high enough to excite from the ground state but, deuterium, electron, and He + densities are high enough to dominate the emission from charge-exchange and recombination. These findings strengthen the assumption made in the present line-ratio model that helium emission from gas-puff into plasma is mainly dominated byelectron-excitation. It is also shown that in general, charge-exchange helium emission is 2-orders of magnitude higher than emission due to recombination. These findings suggest the importance of including charge-exchange processes as a source of neutrals in ionic fractional abundance calculations in plasmas, and helium-ash transport modeling in fusion reactors.

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“…For increases in H 98 factor above design expectations the fusion power is not greatly increased. However, if in practice the H 98 factor achieved is below the design specification, the plasma loses energy faster than it is supplied, energy confinement is lost [151] and the plasma burn cannot be maintained for the required 2 hours. As a result the fusion power collapses, resulting in negative net electricity production.…”

Section: Rebco Tokamaks With Training Magnetsmentioning

confidence: 99%

Training and Upgrading Tokamak Power Plants with Remountable Superconducting Magnets

L.¹,

Surrey²,

Naish³

et al. 2022

Preprint

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All high field superconductors producing magnetic fields above 12 T are brittle. Nevertheless, they will probably be the materials of choice in commercial tokamaks because the fusion power density in a tokamak scales as the fourth power of magnetic field. Here we propose using robust, ductile superconductors during the reactor commissioning phase in order to avoid brittle magnet failure while operational safety margins are being established. Here we use the PROCESS systems code to inform development strategy and to provide detailed capital-cost-minimised tokamak power plant designs. We propose building a 'demonstrator' tokamak with an electric power output of 100 MW e , a plasma fusion gain Q plasma = 17, a net gain Q net = 1.3, a cost of electricity (COE) of $ 1148 (2021 US) per MW h (at 75 % availability) and high temperature superconducting operational TF magnets producing 5.4 T on-axis and 12.5 T peak-field. It uses Nb-Ti training magnets and will cost about $ 9.75 Bn (2021 US). An equivalent 500 MW e plant has a COE of $ 608 per MW suggesting that large tokamaks may eventually dominate the commercial market. We consider a range of designs optimised for capital cost (as the reactors considered are pilot plants) consisting of both 100 MW e and 500 MW e plants with each of two approaches for the magnets: training and upgrading. With training magnets, the plant is cost-optimised for REBCO TF magnets. For a 100 MW e plant, the Nb-Ti training magnets typically produce 70 % peak field on the toroidal field coils compared to REBCO magnets, 65 % peak field on the central solenoid and cost ≈ 10 % of the total machine cost. Training magnets could in principle be reused for each of say 10 subsequent (commercial) machines and hence at 1 % bring only marginal additional cost. With upgrade magnets the plant is more expensive -first it is cost-optimised for Nb-Ti and then upgraded to REBCO coils. The upgrade increases the net electrical output from 100 to 280 MW e with an ≈ 25 % increase in reactor capital cost. We also evaluate likely advances in fusion technology and find that technologies on the horizon will probably not bring further large reductions in capital cost, and that REBCO magnets are generally stress-limited rather than current density limited. We conclude that: the fusion community should develop high B c2 alloys specifically for fusion applications; superconductors should be tested under operational-like radiation at cryogenic temperatures; and that we should proceed now with detailed design and construction of a prototype fusion power plant that integrates and de-risks all the key technologies including high temperature superconducting cables and joints using remountable training magnets, and hence is the last tokamak before commercialisation of fusion energy.

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Fusion burn equilibria sensitive to the ratio between energy and helium transport

Cited by 14 publications

References 15 publications

Analyses of the influence of the recycling coefficient on He confinement in DEMO reactor

Analyses of the influence of the recycling coefficient on He confinement in DEMO reactor

Evaluation of emission contributions from charge-exchange between the excited states of deuterium with He+ during diagnostic of thermal helium gas beam injection and laser-induced fluorescence

Training and Upgrading Tokamak Power Plants with Remountable Superconducting Magnets

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