Abstract:The SPARC tokamak project, currently in engineering design, aims to achieve breakeven and burning plasma conditions in a compact device, thanks to new developments in high-temperature superconductor technology. With a magnetic field of 12.2 T on axis and 8.7 MA of plasma current, SPARC is predicted to produce 140 MW of fusion power with a plasma gain of Q ≈ 11, providing ample margin with respect to its mission of Q > 2. All tokamak systems are being designed to produce this landmark plasma discharge, thus … Show more
“…2011) and SPARC (Rodriguez-Fernandez et al. 2020, 2022 a ). Figure 2.EPED predictions of ( a ) pedestal pressure and ( b – d ) temperature as a function of ( a , b ) pedestal density, ( c ) triangularity and ( d ) normalized pressure in the inductive UCR-P use case (, blue) and steady-state UCR-SS scenario (, red).…”
The OMFIT STEP (Meneghini et al., Nucl. Fusion, vol. 10, 2020, p. 1088) workflow has been used to develop inductive and steady-state H-mode core plasma scenario use cases for a
$B_0 = 8 \, {\rm T}$
,
$R_0 = 4 \, {\rm m}$
machine to help guide and inform future higher-fidelity studies of core transport and confinement in compact tokamak reactors. Both use cases are designed to produce 200 MW or more of net electric power in an up-down symmetric plasma with minor radius
$a = 1.4 \, {\rm m}$
, elongation
$\kappa = 2.0$
, triangularity
$\delta = 0.5$
and effective charge
$Z_{{\rm eff}} \simeq 2$
. Additional considerations based on the need for compatibility of the core with reactor-relevant power exhaust solutions and external actuators were used to guide and constrain the use case development. An extensive characterization of core transport in both scenarios is presented, the most important feature of which is the extreme sensitivity of the results to the quantitative stiffness level of the transport model used as well as the predicted critical gradients. This sensitivity is shown to arise from different levels of transport stiffness exhibited by the models, combined with the gyroBohm-normalized fluxes of the predictions being an order of magnitude larger than other H-mode plasmas. Additionally, it is shown that although heating in both plasmas is predominantly to the electrons and collisionality is low, the plasmas remain sufficiently well coupled for the ions to carry a significant fraction of the thermal transport. As neoclassical transport is negligible in these conditions, this situation inherently requires long-wavelength ion gyroradius-scale turbulence to be the dominant transport mechanism in both plasmas. These results are combined with other basic considerations to propose a simple heuristic model of transport in reactor-relevant plasmas, along with simple metrics to quantify coupling and core transport properties across burning and non-burning plasmas.
“…2011) and SPARC (Rodriguez-Fernandez et al. 2020, 2022 a ). Figure 2.EPED predictions of ( a ) pedestal pressure and ( b – d ) temperature as a function of ( a , b ) pedestal density, ( c ) triangularity and ( d ) normalized pressure in the inductive UCR-P use case (, blue) and steady-state UCR-SS scenario (, red).…”
The OMFIT STEP (Meneghini et al., Nucl. Fusion, vol. 10, 2020, p. 1088) workflow has been used to develop inductive and steady-state H-mode core plasma scenario use cases for a
$B_0 = 8 \, {\rm T}$
,
$R_0 = 4 \, {\rm m}$
machine to help guide and inform future higher-fidelity studies of core transport and confinement in compact tokamak reactors. Both use cases are designed to produce 200 MW or more of net electric power in an up-down symmetric plasma with minor radius
$a = 1.4 \, {\rm m}$
, elongation
$\kappa = 2.0$
, triangularity
$\delta = 0.5$
and effective charge
$Z_{{\rm eff}} \simeq 2$
. Additional considerations based on the need for compatibility of the core with reactor-relevant power exhaust solutions and external actuators were used to guide and constrain the use case development. An extensive characterization of core transport in both scenarios is presented, the most important feature of which is the extreme sensitivity of the results to the quantitative stiffness level of the transport model used as well as the predicted critical gradients. This sensitivity is shown to arise from different levels of transport stiffness exhibited by the models, combined with the gyroBohm-normalized fluxes of the predictions being an order of magnitude larger than other H-mode plasmas. Additionally, it is shown that although heating in both plasmas is predominantly to the electrons and collisionality is low, the plasmas remain sufficiently well coupled for the ions to carry a significant fraction of the thermal transport. As neoclassical transport is negligible in these conditions, this situation inherently requires long-wavelength ion gyroradius-scale turbulence to be the dominant transport mechanism in both plasmas. These results are combined with other basic considerations to propose a simple heuristic model of transport in reactor-relevant plasmas, along with simple metrics to quantify coupling and core transport properties across burning and non-burning plasmas.
“…Recent advances in high-field large bore High Temperature Superconducting (HTS) magnets for fusion devices [10] suggest that the LTS outsert can now be built with HTS. The advantages of an HTS-based solution would be the reduction of the radiation shield thickness, profiting from the large temperature margin of HTS, leading to a smaller diameter SC coil, of lower mass and, possibly, cost.…”
The renewed interest for a muon collider has motivated a thorough analysis of the accelerator technology required for this collider option at the energy frontier. Magnets, both normal and superconducting, are among the crucial technologies throughout the accelerator complex, from production, through acceleration and collision. In this paper we initiate a catalog of magnet specifications for a muon collider at 10TeV center-of-mass. We take the wealth of work performed within the scope of the US-DOE Muon Accelerator Program as a starting point, update it with present demands for the increased energy reach, and focus on the magnet types and variants with the most demanding performance. These represent well the envelope of issues and challenges to be addressed by future design and development. We finally give a first and indicative selection of suitable magnet technology, taking into account both established practices as well as the perspective evolution in the field of accelerator magnets.
“…operation. High-Z metallic environments are planned for next generation tokamaks [1][2][3] and material limitations on incident excess heat fluxes will likely require high impurity seeding for safe power exhaust [4], with high core radiative power fractions (f rad ≡ P rad /P heat > 50%) envisioned for reactor scenarios [5][6][7][8]. At the same time, core contamination with heavy impurities can lead to unacceptable radiative losses of plasma energy, while light impurities can dilute the fuel to insufficient levels for economical fusion power generation [9].…”
An integrated framework that demonstrates multi-species, multi-channel modelling capabilities for the prediction of impurity density profiles and their feedback on the main plasma through radiative cooling and fuel dilution is presented. It combines all presently known theoretical elements in the local description of quasilinear turbulent and neoclassical impurity transport, using the models TGLF-SAT2 and FACIT. These are coupled to the STRAHL code for impurity sources and radiation inside the ASTRA transport solver. The workflow is shown to reproduce experimental results in full-radius L-mode modelling. In particular, a set of ASDEX Upgrade L-modes with differing heating power mixtures and plasma currents are simulated, including boron (B) and tungsten (W) as intrinsic impurities. The increase of predicted confinement with higher current and the reduction of core W peaking with higher central wave heating are demonstrated. Furthermore, a highly radiative L-mode scenario featuring an X-point radiator (XPR) with two intrinsic (B, W) and one seeded argon (Ar) species is simulated, and its measured radiated power and high confinement are recovered by the modelling. The stabilizing effect of impurities on turbulence is analyzed and a simple model for the peripheral X-point radiation is introduced. A preliminary full-radius simulation of an H-mode phase of this same discharge, leveraging recent work on the role of the E×B shearing at the edge, shows promising results.
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