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Characterization of Plasma Impurities During Local Helicity Injection Discharges at the Pegasus-III Experiment
Characterization of Plasma Impurities During Local Helicity Injection Discharges at the Pegasus-III Experiment
상세정보
- 자료유형
- 학위논문 서양
- 최종처리일시
- 20260202105302
- ISBN
- 9798270220174
- DDC
- 530
- 서명/저자
- Characterization of Plasma Impurities During Local Helicity Injection Discharges at the Pegasus-III Experiment
- 발행사항
- [Sl] : The University of Wisconsin - Madison, 2025
- 발행사항
- Ann Arbor : ProQuest Dissertations & Theses, 2025
- 형태사항
- 165 p
- 주기사항
- Source: Dissertations Abstracts International, Volume: 87-06, Section: B.
- 주기사항
- Advisor: Diem, Stephanie.
- 학위논문주기
- Thesis (Ph.D.)--The University of Wisconsin - Madison, 2025.
- 초록/해제
- 요약The majority of current tokamaks initiate and drive the plasma current inductively with an Ohmic solenoid. This approach is not compatible with steady-state operations, due to the limited volt-seconds available. Future experiments and fusion plants will benefit from non-solenoidal startup, which brings engineering, economic, and performance advantages. The new Pegasus-III experiment offers a unique opportunity to investigate viable solenoid-free plasma initiation techniques. The ohmic solenoid was completely removed, allowing for a stronger toroidal field magnetic assembly capable of producing magnetic fields up to 0.6 T at Rmaj~0.45 m.Local Helicity Injection (LHI) is a promising non-solenoidal startup technique and a major research thrust of the Pegasus-III Experiment. LHI employs small, high-power electrodes located at the scrape-off layer that inject helicity into the plasma, initiating and driving. a toroidal current. Impurity production during the start-up phase can negatively impact helicity efficiency by increasing plasma resistivity and may prevent handoff to a sustainment current drive technique.This work presents the initial measurements and analysis of impurity behavior during LHI obtained with a new impurity diagnostic suite that is compatible with Pegasus-III plasma parameters Tahot 10 ms, (n) ~1x1019 m³, and (T)~50 eV. Impurity species are determined by recording time-evolving, single line-of-sight spectra at 1.25 kfps using a vacuum ultraviolet spectrometer. The spectrometer is equipped with two interchangeable gratings to cover spectral ranges 10110 nm, useful to identify light impurities and 10-32 nm for metallic impurities. An absolutely calibrated spectrometer that collects light from the plasma at Rtan 15.9 cm and At ≥ 2 ms is used as a visible survey spectrometer and for continuum measurements. The radiated power from the plasma is estimated with a photodiode-based diagnostic. Two 16-channel absolute extreme ultraviolet diode arrays are placed behind pinhole apertures, resulting in 32 lines of sight at Z= 0, with a spatial resolution of 2-3 cm and a time response of 60 kHz.The typical impurity species identified are low-Z nitrogen and oxygen impurities, most likely residual atmospherics, but metallic impurities have been identified such as titanium, iron or molybdenum, especially during abnormal operations like plasma-material interaction or cathode spots. Impurity transport simulations with the code Aurora constrained with experimental measurements in these initial experimental campaigns of Pegasus-III, result in transport coefficients at neoclassical levels in the core but anomalous levels at the edge. The impurity concentrations inferred through this modeling are small, but can still produce significant radiation losses, comparable to the coupled input power, due to the low charge states reached at these modest temperatures (T 50 eV), significantly impacting LHI performance.
- 일반주제명
- Plasma physics
- 일반주제명
- Nuclear engineering
- 일반주제명
- Engineering
- 일반주제명
- Applied physics
- 키워드
- Fusion plants
- 키워드
- Impurity species
- 키워드
- Plasma
- 기타저자
- The University of Wisconsin - Madison Nuclear Engineering & Engineering Physics
- 기본자료저록
- Dissertations Abstracts International. 87-06B.
- 전자적 위치 및 접속
- 로그인 후 원문을 볼 수 있습니다.
MARC
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■00520260202105302
■006m o d
■007cr#unu||||||||
■020 ▼a9798270220174
■035 ▼a(MiAaPQ)AAI32281783
■040 ▼aMiAaPQ▼cMiAaPQ
■0820 ▼a530
■1001 ▼aRodriguez Sanchez, Cuauhtemoc.
■24510▼aCharacterization of Plasma Impurities During Local Helicity Injection Discharges at the Pegasus-III Experiment
■260 ▼a[Sl]▼bThe University of Wisconsin - Madison▼c2025
■260 1▼aAnn Arbor▼bProQuest Dissertations & Theses▼c2025
■300 ▼a165 p
■500 ▼aSource: Dissertations Abstracts International, Volume: 87-06, Section: B.
■500 ▼aAdvisor: Diem, Stephanie.
■5021 ▼aThesis (Ph.D.)--The University of Wisconsin - Madison, 2025.
■520 ▼aThe majority of current tokamaks initiate and drive the plasma current inductively with an Ohmic solenoid. This approach is not compatible with steady-state operations, due to the limited volt-seconds available. Future experiments and fusion plants will benefit from non-solenoidal startup, which brings engineering, economic, and performance advantages. The new Pegasus-III experiment offers a unique opportunity to investigate viable solenoid-free plasma initiation techniques. The ohmic solenoid was completely removed, allowing for a stronger toroidal field magnetic assembly capable of producing magnetic fields up to 0.6 T at Rmaj~0.45 m.Local Helicity Injection (LHI) is a promising non-solenoidal startup technique and a major research thrust of the Pegasus-III Experiment. LHI employs small, high-power electrodes located at the scrape-off layer that inject helicity into the plasma, initiating and driving. a toroidal current. Impurity production during the start-up phase can negatively impact helicity efficiency by increasing plasma resistivity and may prevent handoff to a sustainment current drive technique.This work presents the initial measurements and analysis of impurity behavior during LHI obtained with a new impurity diagnostic suite that is compatible with Pegasus-III plasma parameters Tahot 10 ms, (n) ~1x1019 m³, and (T)~50 eV. Impurity species are determined by recording time-evolving, single line-of-sight spectra at 1.25 kfps using a vacuum ultraviolet spectrometer. The spectrometer is equipped with two interchangeable gratings to cover spectral ranges 10110 nm, useful to identify light impurities and 10-32 nm for metallic impurities. An absolutely calibrated spectrometer that collects light from the plasma at Rtan 15.9 cm and At ≥ 2 ms is used as a visible survey spectrometer and for continuum measurements. The radiated power from the plasma is estimated with a photodiode-based diagnostic. Two 16-channel absolute extreme ultraviolet diode arrays are placed behind pinhole apertures, resulting in 32 lines of sight at Z= 0, with a spatial resolution of 2-3 cm and a time response of 60 kHz.The typical impurity species identified are low-Z nitrogen and oxygen impurities, most likely residual atmospherics, but metallic impurities have been identified such as titanium, iron or molybdenum, especially during abnormal operations like plasma-material interaction or cathode spots. Impurity transport simulations with the code Aurora constrained with experimental measurements in these initial experimental campaigns of Pegasus-III, result in transport coefficients at neoclassical levels in the core but anomalous levels at the edge. The impurity concentrations inferred through this modeling are small, but can still produce significant radiation losses, comparable to the coupled input power, due to the low charge states reached at these modest temperatures (T 50 eV), significantly impacting LHI performance.
■590 ▼aSchool code: 0262.
■650 4▼aPlasma physics
■650 4▼aNuclear engineering
■650 4▼aEngineering
■650 4▼aApplied physics
■653 ▼aFusion plants
■653 ▼aImpurity species
■653 ▼aNon-solenoidal startup
■653 ▼aPegasus-III Experiment
■653 ▼aPlasma
■690 ▼a0759
■690 ▼a0552
■690 ▼a0537
■690 ▼a0215
■71020▼aThe University of Wisconsin - Madison▼bNuclear Engineering & Engineering Physics.
■7730 ▼tDissertations Abstracts International▼g87-06B.
■790 ▼a0262
■791 ▼aPh.D.
■792 ▼a2025
■793 ▼aEnglish
■85640▼uhttp://www.riss.kr/pdu/ddodLink.do?id=T17360087▼nKERIS▼z이 자료의 원문은 한국교육학술정보원에서 제공합니다.
