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Souza LC, Sales MR, Mugnaine M, Szezech JD, Caldas IL, Viana RL. Chaotic escape of impurities and sticky orbits in toroidal plasmas. Phys Rev E 2024; 109:015202. [PMID: 38366399 DOI: 10.1103/physreve.109.015202] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/12/2023] [Accepted: 12/01/2023] [Indexed: 02/18/2024]
Abstract
We investigate chaotic impurity transport in toroidal fusion plasmas (tokamaks) from the point of view of passive advection of charged particles due to E×B drift motion. We use realistic tokamak profiles for electric and magnetic fields as well as toroidal rotation effects, and consider also the effects of electrostatic fluctuations due to drift instabilities on particle motion. A time-dependent one degree-of-freedom Hamiltonian system is obtained and numerically investigated through a symplectic map in a Poincaré surface of section. We show that the chaotic transport in the outer plasma region is influenced by fractal structures that are described in topological and metric point of views. Moreover, the existence of a hierarchical structure of islands-around-islands, where the particles experience the stickiness effect, is demonstrated using a recurrence-based approach.
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Affiliation(s)
- L C Souza
- Universidade Federal do Paraná, Departamento de Física, Curitiba, PR 81531-990, Brazil
| | - M R Sales
- Universidade Estadual de Ponta Grossa, Programa de Pós-Graduação em Ciências, Ponta Grossa, PR 84030-900, Brazil
| | - M Mugnaine
- Universidade de São Paulo, Instituto de Física, São Paulo, SP 05315-970, Brazil
| | - J D Szezech
- Universidade Estadual de Ponta Grossa, Programa de Pós-Graduação em Ciências, Ponta Grossa, PR 84030-900, Brazil
| | - I L Caldas
- Universidade de São Paulo, Instituto de Física, São Paulo, SP 05315-970, Brazil
| | - R L Viana
- Universidade Federal do Paraná, Departamento de Física, Curitiba, PR 81531-990, Brazil
- Universidade de São Paulo, Instituto de Física, São Paulo, SP 05315-970, Brazil
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Feng S, Peng X, Song Y, Liu P, Song W, Mao X, Qian X, Salman Khan M. Development of continuous V-shaped structure for high heat flux components of flat-type divertor. NUCLEAR MATERIALS AND ENERGY 2023. [DOI: 10.1016/j.nme.2023.101419] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 03/18/2023]
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Dependence of particle and power dissipation on divertor geometry and plasma shaping in DIII-D small-angle-slot divertor. NUCLEAR MATERIALS AND ENERGY 2022. [DOI: 10.1016/j.nme.2022.101301] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
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Février O, Reimerdes H, Theiler C, Brida D, Colandrea C, De Oliveira H, Duval B, Galassi D, Gorno S, Henderson S, Komm M, Labit B, Linehan B, Martinelli L, Perek A, Raj H, Sheikh U, Tsui C, Wensing M. Divertor closure effects on the TCV boundary plasma. NUCLEAR MATERIALS AND ENERGY 2021. [DOI: 10.1016/j.nme.2021.100977] [Citation(s) in RCA: 10] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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Real-time feedback control of the impurity emission front in tokamak divertor plasmas. Nat Commun 2021; 12:1105. [PMID: 33597525 PMCID: PMC7889616 DOI: 10.1038/s41467-021-21268-3] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/10/2020] [Accepted: 01/20/2021] [Indexed: 11/30/2022] Open
Abstract
In magnetic confinement thermonuclear fusion the exhaust of heat and particles from the core remains a major challenge. Heat and particles leaving the core are transported via open magnetic field lines to a region of the reactor wall, called the divertor. Unabated, the heat and particle fluxes may become intolerable and damage the divertor. Controlled ‘plasma detachment’, a regime characterized by both a large reduction in plasma pressure and temperature at the divertor target, is required to reduce fluxes onto the divertor. Here we report a systematic approach towards achieving this critical need through feedback control of impurity emission front locations and its experimental demonstration. Our approach comprises a combination of real-time plasma diagnostic utilization, dynamic characterization of the plasma in proximity to the divertor, and efficient, reliable offline feedback controller design. The exhaust of heat and particles is an important challenge in future nuclear fusion devices. Here the authors report the use of carbon emission as indicator for plasma detachment in a tokamak and its real-time feedback control.
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Pitts R, Bonnin X, Escourbiac F, Frerichs H, Gunn J, Hirai T, Kukushkin A, Kaveeva E, Miller M, Moulton D, Rozhansky V, Senichenkov I, Sytova E, Schmitz O, Stangeby P, De Temmerman G, Veselova I, Wiesen S. Physics basis for the first ITER tungsten divertor. NUCLEAR MATERIALS AND ENERGY 2019. [DOI: 10.1016/j.nme.2019.100696] [Citation(s) in RCA: 113] [Impact Index Per Article: 22.6] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/26/2022]
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The effect of neutrals in the new SAS divertor at DIII-D as modelled by SOLPS. NUCLEAR MATERIALS AND ENERGY 2019. [DOI: 10.1016/j.nme.2019.03.021] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
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Kuang A, Cao N, Creely A, Dennett C, Hecla J, LaBombard B, Tinguely R, Tolman E, Hoffman H, Major M, Ruiz Ruiz J, Brunner D, Grover P, Laughman C, Sorbom B, Whyte D. Conceptual design study for heat exhaust management in the ARC fusion pilot plant. FUSION ENGINEERING AND DESIGN 2018. [DOI: 10.1016/j.fusengdes.2018.09.007] [Citation(s) in RCA: 34] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
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Jaervinen AE, Allen SL, Eldon D, Fenstermacher ME, Groth M, Hill DN, Leonard AW, McLean AG, Porter GD, Rognlien TD, Samuell CM, Wang HQ. E×B Flux Driven Detachment Bifurcation in the DIII-D Tokamak. PHYSICAL REVIEW LETTERS 2018; 121:075001. [PMID: 30169054 DOI: 10.1103/physrevlett.121.075001] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/05/2017] [Revised: 06/21/2018] [Indexed: 06/08/2023]
Abstract
A bifurcative step transition from low-density, high-temperature, attached divertor conditions to high-density, low-temperature, detached divertor conditions is experimentally observed in DIII-D tokamak plasmas as density is increased. The step transition is only observed in the high confinement mode and only when the B×∇B drift is directed towards the divertor. This work reports for the first time a theoretical explanation and numerical simulations that qualitatively reproduce this bifurcation and its dependence on the toroidal field direction. According to the model, the bifurcation is primarily driven by the interdependence of the E×B-drift fluxes, divertor electric potential structure, and divertor conditions. In the attached conditions, strong potential gradients in the low field side (LFS) divertor drive E×B-drift flux towards the high field side divertor, reinforcing low density, high temperature conditions in the LFS divertor leg. At the onset of detachment, reduction in the potential gradients in the LFS divertor leg reduce the E×B-drift flux as well, such that the divertor plasma evolves nonlinearly to high density, strongly detached conditions. Experimental estimates of the E×B-drift fluxes, based on divertor Thomson scattering measurements, and their dependence on the divertor conditions are qualitatively consistent with the numerical predictions. The implications for divertor power exhaust and detachment control in the next step fusion devices are discussed.
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Affiliation(s)
- A E Jaervinen
- Lawrence Livermore National Laboratory, Livermore, California 94550, USA
| | - S L Allen
- Lawrence Livermore National Laboratory, Livermore, California 94550, USA
| | - D Eldon
- Lawrence Livermore National Laboratory, Livermore, California 94550, USA
| | - M E Fenstermacher
- Lawrence Livermore National Laboratory, Livermore, California 94550, USA
| | - M Groth
- Lawrence Livermore National Laboratory, Livermore, California 94550, USA
| | - D N Hill
- Lawrence Livermore National Laboratory, Livermore, California 94550, USA
| | - A W Leonard
- Lawrence Livermore National Laboratory, Livermore, California 94550, USA
| | - A G McLean
- Lawrence Livermore National Laboratory, Livermore, California 94550, USA
| | - G D Porter
- Lawrence Livermore National Laboratory, Livermore, California 94550, USA
| | - T D Rognlien
- Lawrence Livermore National Laboratory, Livermore, California 94550, USA
| | - C M Samuell
- Lawrence Livermore National Laboratory, Livermore, California 94550, USA
| | - H Q Wang
- Lawrence Livermore National Laboratory, Livermore, California 94550, USA
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SOL parallel momentum loss in ASDEX Upgrade and comparison with SOLPS. NUCLEAR MATERIALS AND ENERGY 2017. [DOI: 10.1016/j.nme.2017.01.026] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
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Umansky M, Rensink M, Rognlien T, LaBombard B, Brunner D, Terry J, Whyte D. Assessment of X-point target divertor configuration for power handling and detachment front control. NUCLEAR MATERIALS AND ENERGY 2017. [DOI: 10.1016/j.nme.2017.03.015] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/19/2022]
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Brunner D, Burke W, Kuang AQ, LaBombard B, Lipschultz B, Wolfe S. Feedback system for divertor impurity seeding based on real-time measurements of surface heat flux in the Alcator C-Mod tokamak. THE REVIEW OF SCIENTIFIC INSTRUMENTS 2016; 87:023504. [PMID: 26931846 DOI: 10.1063/1.4941047] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/18/2015] [Accepted: 01/16/2016] [Indexed: 06/05/2023]
Abstract
Mitigation of the intense heat flux to the divertor is one of the outstanding problems in fusion energy. One technique that has shown promise is impurity seeding, i.e., the injection of low-Z gaseous impurities (typically N2 or Ne) to radiate and dissipate the power before it arrives to the divertor target plate. To this end, the Alcator C-Mod team has created a first-of-its-kind feedback system to control the injection of seed gas based on real-time surface heat flux measurements. Surface thermocouples provide real-time measurements of the surface temperature response to the plasma heat flux. The surface temperature measurements are inputted into an analog computer that "solves" the 1-D heat transport equation to deliver accurate, real-time signals of the surface heat flux. The surface heat flux signals are sent to the C-Mod digital plasma control system, which uses a proportional-integral-derivative (PID) algorithm to control the duty cycle demand to a pulse width modulated piezo valve, which in turn controls the injection of gas into the private flux region of the C-Mod divertor. This paper presents the design and implementation of this new feedback system as well as initial results using it to control divertor heat flux.
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Affiliation(s)
- D Brunner
- Plasma Science and Fusion Center, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA
| | - W Burke
- Plasma Science and Fusion Center, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA
| | - A Q Kuang
- Plasma Science and Fusion Center, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA
| | - B LaBombard
- Plasma Science and Fusion Center, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA
| | - B Lipschultz
- Department of Physics, University of York, Heslington, York YO10 5DD, United Kingdom
| | - S Wolfe
- Plasma Science and Fusion Center, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA
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