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Investigating Density Fluctuations and Rotation in Tokamak Plasmas With Doppler Back-Scattering
Investigating Density Fluctuations and Rotation in Tokamak Plasmas With Doppler Back-Scattering
상세정보
- 자료유형
- 학위논문 서양
- 최종처리일시
- 20250211151518
- ISBN
- 9798382756127
- DDC
- 530
- 서명/저자
- Investigating Density Fluctuations and Rotation in Tokamak Plasmas With Doppler Back-Scattering
- 발행사항
- [Sl] : University of California, Los Angeles, 2024
- 발행사항
- Ann Arbor : ProQuest Dissertations & Theses, 2024
- 형태사항
- 221 p
- 주기사항
- Source: Dissertations Abstracts International, Volume: 85-11, Section: B.
- 주기사항
- Advisor: Carter, Troy A.
- 학위논문주기
- Thesis (Ph.D.)--University of California, Los Angeles, 2024.
- 초록/해제
- 요약This dissertation reports advancements in measuring density fluctuations and flow velocity in tokamak plasmas using the Doppler back-scattering (DBS) diagnostic. Two separate investigations are presented: measurements of the back-scattered power perpendicular wavenumber spectrum, and a thorough cross-diagnostic comparison of E x B rotation measurements. To measure the perpendicular wavenumber spectrum using DBS, the launch-angle(s) of the probing beam were scanned to probe different values of k⊥ at the cutoff layer. Measurements were made in RF-heated H-mode plasmas with low collisionality and dominant electron-heating - a regime expected to be relevant for future burning plasmas. The back-scattered power spectrum, Ps(k⊥), is found to exhibit exponential decay. In normalized wavenumbers, the exponential decay factor (Ps(k⊥) ∝ e−ζ(k⊥ρs)) was found to be ζ ≈ 1.7 over the majority of the spectrum and ζ ≈ 3.9 at high-k⊥ρs. Novel synthetic diagnostic modeling was performed to test models of plasma turbulence against the measured Ps(k⊥). DBS instrumental effects and the plasma density fluctuations, δn, were each modeled with varying levels of physics-fidelity. Reduced model beam-tracing and quasi-linear gyro-fluid results are compared with higher-fidelity full-wave and nonlinear gyrokinetics simulations. Ultimately, mixed-agreement between measurements and simulations across the wavenumber spectrum is found. At the lowest measured wavenumbers k⊥ρs ≤ 0.4 and for k⊥ρs ≥ 1.2 simulations and measurements agree as to the shape of the wavenumber spectrum. Over the range 0.4 k⊥ρs 1.2, simulations and measurements disagree as to the rate of spectral decay. Transport modeling found that while the reduced quasi-linear model can match the experimental fluxes, it does not reproduce the higher-fidelity nonlinear gyrokinetic behavior in the electron energy channel. In a separate investigation, rigorous cross-diagnostic comparisons were made between DBS and the charge-exchange recombination spectroscopy (CER) diagnostics. Measurements were made in an L-mode plasma where neutral beam injection (NBI) applied a variable external torque. In analyzing the DBS measurements, novel spectral fitting methods and uncertainty propagation were used to construct the DBS-CER comparison dataset. Statistical analysis suggests a tendency for DBS and CER to agree within their respective uncertainties. Across the comparison dataset, the average difference in ωExB was found to be |d| = 0.1 kRad/s. The 95% confidence interval for their agreement was found to be approximately 5 kRad/s in terms of ωExB. The phase velocity of δn fluctuations was estimated using linear gyro-fluid analysis and found to be negligible relative to vExB. The results of the rotation investigation provide a certain level of mutual-validation for DBS and CER in measuring E x B rotation.
- 일반주제명
- Plasma physics
- 일반주제명
- Physics
- 일반주제명
- Fluid mechanics
- 키워드
- Nuclear fusion
- 키워드
- Tokamak rotation
- 기타저자
- University of California, Los Angeles Physics 0666
- 기본자료저록
- Dissertations Abstracts International. 85-11B.
- 전자적 위치 및 접속
- 로그인 후 원문을 볼 수 있습니다.
MARC
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■00520250211151518
■006m o d
■007cr#unu||||||||
■020 ▼a9798382756127
■035 ▼a(MiAaPQ)AAI31301109
■040 ▼aMiAaPQ▼cMiAaPQ
■0820 ▼a530
■1001 ▼aPratt, Quinn Thomas.
■24510▼aInvestigating Density Fluctuations and Rotation in Tokamak Plasmas With Doppler Back-Scattering
■260 ▼a[Sl]▼bUniversity of California, Los Angeles▼c2024
■260 1▼aAnn Arbor▼bProQuest Dissertations & Theses▼c2024
■300 ▼a221 p
■500 ▼aSource: Dissertations Abstracts International, Volume: 85-11, Section: B.
■500 ▼aAdvisor: Carter, Troy A.
■5021 ▼aThesis (Ph.D.)--University of California, Los Angeles, 2024.
■520 ▼aThis dissertation reports advancements in measuring density fluctuations and flow velocity in tokamak plasmas using the Doppler back-scattering (DBS) diagnostic. Two separate investigations are presented: measurements of the back-scattered power perpendicular wavenumber spectrum, and a thorough cross-diagnostic comparison of E x B rotation measurements. To measure the perpendicular wavenumber spectrum using DBS, the launch-angle(s) of the probing beam were scanned to probe different values of k⊥ at the cutoff layer. Measurements were made in RF-heated H-mode plasmas with low collisionality and dominant electron-heating - a regime expected to be relevant for future burning plasmas. The back-scattered power spectrum, Ps(k⊥), is found to exhibit exponential decay. In normalized wavenumbers, the exponential decay factor (Ps(k⊥) ∝ e−ζ(k⊥ρs)) was found to be ζ ≈ 1.7 over the majority of the spectrum and ζ ≈ 3.9 at high-k⊥ρs. Novel synthetic diagnostic modeling was performed to test models of plasma turbulence against the measured Ps(k⊥). DBS instrumental effects and the plasma density fluctuations, δn, were each modeled with varying levels of physics-fidelity. Reduced model beam-tracing and quasi-linear gyro-fluid results are compared with higher-fidelity full-wave and nonlinear gyrokinetics simulations. Ultimately, mixed-agreement between measurements and simulations across the wavenumber spectrum is found. At the lowest measured wavenumbers k⊥ρs ≤ 0.4 and for k⊥ρs ≥ 1.2 simulations and measurements agree as to the shape of the wavenumber spectrum. Over the range 0.4 k⊥ρs 1.2, simulations and measurements disagree as to the rate of spectral decay. Transport modeling found that while the reduced quasi-linear model can match the experimental fluxes, it does not reproduce the higher-fidelity nonlinear gyrokinetic behavior in the electron energy channel. In a separate investigation, rigorous cross-diagnostic comparisons were made between DBS and the charge-exchange recombination spectroscopy (CER) diagnostics. Measurements were made in an L-mode plasma where neutral beam injection (NBI) applied a variable external torque. In analyzing the DBS measurements, novel spectral fitting methods and uncertainty propagation were used to construct the DBS-CER comparison dataset. Statistical analysis suggests a tendency for DBS and CER to agree within their respective uncertainties. Across the comparison dataset, the average difference in ωExB was found to be |d| = 0.1 kRad/s. The 95% confidence interval for their agreement was found to be approximately 5 kRad/s in terms of ωExB. The phase velocity of δn fluctuations was estimated using linear gyro-fluid analysis and found to be negligible relative to vExB. The results of the rotation investigation provide a certain level of mutual-validation for DBS and CER in measuring E x B rotation.
■590 ▼aSchool code: 0031.
■650 4▼aPlasma physics
■650 4▼aPhysics
■650 4▼aFluid mechanics
■653 ▼aDensity fluctuations
■653 ▼aDoppler back-scattering
■653 ▼aFluctuation diagnostics
■653 ▼aNuclear fusion
■653 ▼aTokamak rotation
■653 ▼aWavenumber spectrum
■690 ▼a0759
■690 ▼a0204
■690 ▼a0605
■71020▼aUniversity of California, Los Angeles▼bPhysics 0666.
■7730 ▼tDissertations Abstracts International▼g85-11B.
■790 ▼a0031
■791 ▼aPh.D.
■792 ▼a2024
■793 ▼aEnglish
■85640▼uhttp://www.riss.kr/pdu/ddodLink.do?id=T17162056▼nKERIS▼z이 자료의 원문은 한국교육학술정보원에서 제공합니다.
