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Exploring Performance Scaling Properties of Local Helicity Injection Plasma Startup on Pegasus-III
Exploring Performance Scaling Properties of Local Helicity Injection Plasma Startup on Pegasus-III
상세정보
- 자료유형
- 학위논문 서양
- 최종처리일시
- 20260202103523
- ISBN
- 9798314872796
- DDC
- 530
- 서명/저자
- Exploring Performance Scaling Properties of Local Helicity Injection Plasma Startup on Pegasus-III
- 발행사항
- [Sl] : The University of Wisconsin - Madison, 2025
- 발행사항
- Ann Arbor : ProQuest Dissertations & Theses, 2025
- 형태사항
- 191 p
- 주기사항
- Source: Dissertations Abstracts International, Volume: 86-11, Section: B.
- 주기사항
- Advisor: Diem, Stephanie J.
- 학위논문주기
- Thesis (Ph.D.)--The University of Wisconsin - Madison, 2025.
- 초록/해제
- 요약Solenoid-free tokamak startup techniques can simplify the design and reduce the cost of tokamak-based fusion energy systems. The newly commissioned Pegasus-III spherical tokamak provides a dedicated platform for developing a scalable solenoid-free startup approach. Local helicity injection (LHI) is one promising technique being developed on Pegasus-III which uses compact edge current sources to drive open field line current Iinj which is redistributed via helicity-conserving instabilities and subsequently relaxes to a tokamak-like state with plasma current Ip far greater than Iinj. Validated predictive models are needed to accurately project LHI performance on Pegasus-III and beyond. This work advances this goal by characterizing the scaling of a fundamental global Ip limit, referred to as the Taylor limit ITL, and helicity dissipation during LHI discharges in the expanded operating space provided by Pegasus-III. These experiments illustrate that increasing the Taylor limit leads to more effective utilization of the available helicity input and higher Ip plasmas. Further, they verify the expected ITL∝(Iinj BT )1⁄2 scaling holds for toroidal field BT and Iinj up to 0.3 T on axis and 12 kA, respectively. Additionally, data from different injector arrays show that the width of the injector aperture directly alters ITL and can be leveraged for future injector design optimization. Discharges over-driven at Ip=ITL experienced more frequent bursts of n=1 magnetic activity consistent with large scale reconnection events. These reconnection events appear to drive magnetic relaxation in these discharges as indicated by a flattening of the λ=μ0 J∥⁄|B| profile, where J∥ is the parallel current density. When operating with IpITL, the Ip is dictated by the balance of magnetic helicity input and dissipation. Parametric BT and density scans were assessed in the context of global energy confinement models to characterize the scaling of helicity dissipation during LHI. Relatively high amounts of radiated power attributed to plasma-material interactions appear to be dominating the power balance in these discharges and may mask the behavior of the underlying energy confinement properties. Still, interpretive analysis with an extended 0-D power balance model suggests that the experimental trends may be described by linear ohmic energy confinement scaling estimates.
- 일반주제명
- Plasma physics
- 일반주제명
- Nuclear physics
- 일반주제명
- Applied physics
- 키워드
- Fusion
- 키워드
- Pegasus-III
- 기타저자
- The University of Wisconsin - Madison Nuclear Engineering & Engineering Physics
- 기본자료저록
- Dissertations Abstracts International. 86-11B.
- 전자적 위치 및 접속
- 로그인 후 원문을 볼 수 있습니다.
MARC
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■00520260202103523
■006m o d
■007cr#unu||||||||
■020 ▼a9798314872796
■035 ▼a(MiAaPQ)AAI32039047
■040 ▼aMiAaPQ▼cMiAaPQ
■0820 ▼a530
■1001 ▼aWeberski, Justin Daniel.
■24510▼aExploring Performance Scaling Properties of Local Helicity Injection Plasma Startup on Pegasus-III
■260 ▼a[Sl]▼bThe University of Wisconsin - Madison▼c2025
■260 1▼aAnn Arbor▼bProQuest Dissertations & Theses▼c2025
■300 ▼a191 p
■500 ▼aSource: Dissertations Abstracts International, Volume: 86-11, Section: B.
■500 ▼aAdvisor: Diem, Stephanie J.
■5021 ▼aThesis (Ph.D.)--The University of Wisconsin - Madison, 2025.
■520 ▼aSolenoid-free tokamak startup techniques can simplify the design and reduce the cost of tokamak-based fusion energy systems. The newly commissioned Pegasus-III spherical tokamak provides a dedicated platform for developing a scalable solenoid-free startup approach. Local helicity injection (LHI) is one promising technique being developed on Pegasus-III which uses compact edge current sources to drive open field line current Iinj which is redistributed via helicity-conserving instabilities and subsequently relaxes to a tokamak-like state with plasma current Ip far greater than Iinj. Validated predictive models are needed to accurately project LHI performance on Pegasus-III and beyond. This work advances this goal by characterizing the scaling of a fundamental global Ip limit, referred to as the Taylor limit ITL, and helicity dissipation during LHI discharges in the expanded operating space provided by Pegasus-III. These experiments illustrate that increasing the Taylor limit leads to more effective utilization of the available helicity input and higher Ip plasmas. Further, they verify the expected ITL∝(Iinj BT )1⁄2 scaling holds for toroidal field BT and Iinj up to 0.3 T on axis and 12 kA, respectively. Additionally, data from different injector arrays show that the width of the injector aperture directly alters ITL and can be leveraged for future injector design optimization. Discharges over-driven at Ip=ITL experienced more frequent bursts of n=1 magnetic activity consistent with large scale reconnection events. These reconnection events appear to drive magnetic relaxation in these discharges as indicated by a flattening of the λ=μ0 J∥⁄|B| profile, where J∥ is the parallel current density. When operating with IpITL, the Ip is dictated by the balance of magnetic helicity input and dissipation. Parametric BT and density scans were assessed in the context of global energy confinement models to characterize the scaling of helicity dissipation during LHI. Relatively high amounts of radiated power attributed to plasma-material interactions appear to be dominating the power balance in these discharges and may mask the behavior of the underlying energy confinement properties. Still, interpretive analysis with an extended 0-D power balance model suggests that the experimental trends may be described by linear ohmic energy confinement scaling estimates.
■590 ▼aSchool code: 0262.
■650 4▼aPlasma physics
■650 4▼aNuclear physics
■650 4▼aApplied physics
■653 ▼aFusion
■653 ▼aLocal helicity injection
■653 ▼aPegasus-III
■653 ▼aSolenoid-free startup
■653 ▼aSpherical tokamak
■653 ▼aTaylor relaxation
■690 ▼a0759
■690 ▼a0756
■690 ▼a0215
■71020▼aThe University of Wisconsin - Madison▼bNuclear Engineering & Engineering Physics.
■7730 ▼tDissertations Abstracts International▼g86-11B.
■790 ▼a0262
■791 ▼aPh.D.
■792 ▼a2025
■793 ▼aEnglish
■85640▼uhttp://www.riss.kr/pdu/ddodLink.do?id=T17357519▼nKERIS▼z이 자료의 원문은 한국교육학술정보원에서 제공합니다.
