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Characterization of Momentum and Heat Flow in Hall Thrusters With Laser Scattering
Characterization of Momentum and Heat Flow in Hall Thrusters With Laser Scattering
상세정보
- 자료유형
- 학위논문 서양
- 최종처리일시
- 20260202103640
- ISBN
- 9798314874196
- DDC
- 629.1
- 서명/저자
- Characterization of Momentum and Heat Flow in Hall Thrusters With Laser Scattering
- 발행사항
- [Sl] : University of Michigan, 2025
- 발행사항
- Ann Arbor : ProQuest Dissertations & Theses, 2025
- 형태사항
- 352 p
- 주기사항
- Source: Dissertations Abstracts International, Volume: 86-11, Section: B.
- 주기사항
- Advisor: Jorns, Benjamin.
- 학위논문주기
- Thesis (Ph.D.)--University of Michigan, 2025.
- 초록/해제
- 요약Non-invasive measurement techniques are leveraged to investigate the electron and ion flows in Hall thruster and hollow cathode discharges, for the purpose of informing models that can predict performance and lifetime of these devices. Recent developments in incoherent Thomson scattering for low-density plasmas are combined with a laser-induced fluorescence velocimetry diagnostic to obtain direct, kinetic, and non-intrusive measurements of both the electron and ion properties in electric propulsion plasmas.The Thomson scattering diagnostic is used to directly measure the axial Mach number of the current-carrying electrons in a cathode plume for the first time. An empirical relationship between the Mach number and the background plasma properties is found, which is consistent with marginally stable ion acoustic turbulence in the hollow cathode plume. This finding provides a constraint from which to model hollow cathode turbulence from first principles within a fluid framework for electron particle, momentum, and energy conservation.These combined electron and ion diagnostics are applied to make spatially resolved measurements of the sparser electron population in the near-field plume of a 9-kW, magnetically shielded Hall thruster. A theoretical method is developed to infer from these measurements the anomalous transport profile, a representation of unknown forces from turbulent electron scattering which underlies the essential physics of Hall thruster operation. This technique is validated against anomalous transport estimations from models, and parametric studies of anomalous transport as a function of propellant, discharge voltage, and discharge current are carried out. It is confirmed non-intrusively that the electrons flow across field lines with Bohm scaling downstream of the ion acceleration region in Hall thrusters, but are trapped in a high-confinement region with reduced transport that drives up the electric field and temperature.An analysis of the electron temperature profile in the Hall thruster plume is carried out based on these new measurements, and it is found that the peak electron temperature measured with Thomson scattering is proportional to the discharge voltage, but with an increased scaling constant than traditionally expected by a factor of 2.5. This finding reproduces the high electron temperatures which were previously measured with a similar diagnostic in a low-power Hall thruster. These high temperatures alter the expected force balance in the Hall thruster, implying that pressure effects have been underestimated in past studies. In order to investigate the heat flow conditions leading to these high temperatures, a two-dimensional mapping of the electron and ion properties is subsequently carried out with ITS and LIF. It is found that the widely held assumption that electron temperatures are constant along magnetic field lines does not hold. Rather, the electron temperature and plasma potential vary significantly along the magnetic field - with a hot-spot of 40-100 eV electrons present in the center of the Hall thruster channel. A collisional argument is used to explain this thermal gradient in terms of restrictions on the heat flux term which are not currently captured by fluid models of these devices. To search for a low-fidelity approximation to this heat flow physics, the value of the effective polytropic index for thermodynamic electron expansion along magnetic field lines is investigated. and it is found that in the far-field plume, where plasma turbulence causes Bohm-like transport, the electron heat flux progresses from adiabatic to isothermal scaling.In addition to these time-averaged studies, time-resolved extensions of the LIF and ITS diagnostics investigated in Hall thruster plasmas, and an algorithm is presented for using "Shadow Manifold Interpolation" based on Takens's Theorem to map noisy pulsed diagnostics such as Thomson scattering to a noise-free reference signal, such as the discharge current, which globally represents the state of the thruster as a dynamical system. This nonlinear algorithm is validated against results using transfer function estimation, a standard linear method for reconstructing noisy datasets. Preliminary time-resolved Thomson scattering measurements show small fluctuations in the electron velocity distribution function, but more signal is necessary to truly resolve oscillations in the plasma to a useful degree. Time-resolved methods are leveraged for LIF investigations of the azimuthal ion waves which grow near the cathode of Hall thrusters, and the potential of these waves to cause erosion by energizing the ions is addressed.These results compose a series of novel insights about electron and ion flow physics both in the channel and cathode region of Hall thrusters. They are discussed in the context of present efforts to model Hall thruster particle flows with fluid-averaged approximations, and recommendations are made for capturing the electron physics reflected by these new diagnostic capabilities. Validation and comparisons are made between the Thomson scattering results and other methods to infer the electron temperatures, including estimation and Langmuir probe injection. Reasons for discrepancies between these high temperature measurements and past estimates of the electron temperature are discussed.
- 일반주제명
- Aerospace engineering
- 일반주제명
- Plasma physics
- 키워드
- Cathode region
- 기타저자
- University of Michigan Aerospace Engineering
- 기본자료저록
- Dissertations Abstracts International. 86-11B.
- 전자적 위치 및 접속
- 로그인 후 원문을 볼 수 있습니다.
MARC
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■00520260202103640
■006m o d
■007cr#unu||||||||
■020 ▼a9798314874196
■035 ▼a(MiAaPQ)AAI32092524
■035 ▼a(MiAaPQ)umichrackham006135
■040 ▼aMiAaPQ▼cMiAaPQ
■0820 ▼a629.1
■1001 ▼aRoberts, Parker J.
■24510▼aCharacterization of Momentum and Heat Flow in Hall Thrusters With Laser Scattering
■260 ▼a[Sl]▼bUniversity of Michigan▼c2025
■260 1▼aAnn Arbor▼bProQuest Dissertations & Theses▼c2025
■300 ▼a352 p
■500 ▼aSource: Dissertations Abstracts International, Volume: 86-11, Section: B.
■500 ▼aAdvisor: Jorns, Benjamin.
■5021 ▼aThesis (Ph.D.)--University of Michigan, 2025.
■520 ▼aNon-invasive measurement techniques are leveraged to investigate the electron and ion flows in Hall thruster and hollow cathode discharges, for the purpose of informing models that can predict performance and lifetime of these devices. Recent developments in incoherent Thomson scattering for low-density plasmas are combined with a laser-induced fluorescence velocimetry diagnostic to obtain direct, kinetic, and non-intrusive measurements of both the electron and ion properties in electric propulsion plasmas.The Thomson scattering diagnostic is used to directly measure the axial Mach number of the current-carrying electrons in a cathode plume for the first time. An empirical relationship between the Mach number and the background plasma properties is found, which is consistent with marginally stable ion acoustic turbulence in the hollow cathode plume. This finding provides a constraint from which to model hollow cathode turbulence from first principles within a fluid framework for electron particle, momentum, and energy conservation.These combined electron and ion diagnostics are applied to make spatially resolved measurements of the sparser electron population in the near-field plume of a 9-kW, magnetically shielded Hall thruster. A theoretical method is developed to infer from these measurements the anomalous transport profile, a representation of unknown forces from turbulent electron scattering which underlies the essential physics of Hall thruster operation. This technique is validated against anomalous transport estimations from models, and parametric studies of anomalous transport as a function of propellant, discharge voltage, and discharge current are carried out. It is confirmed non-intrusively that the electrons flow across field lines with Bohm scaling downstream of the ion acceleration region in Hall thrusters, but are trapped in a high-confinement region with reduced transport that drives up the electric field and temperature.An analysis of the electron temperature profile in the Hall thruster plume is carried out based on these new measurements, and it is found that the peak electron temperature measured with Thomson scattering is proportional to the discharge voltage, but with an increased scaling constant than traditionally expected by a factor of 2.5. This finding reproduces the high electron temperatures which were previously measured with a similar diagnostic in a low-power Hall thruster. These high temperatures alter the expected force balance in the Hall thruster, implying that pressure effects have been underestimated in past studies. In order to investigate the heat flow conditions leading to these high temperatures, a two-dimensional mapping of the electron and ion properties is subsequently carried out with ITS and LIF. It is found that the widely held assumption that electron temperatures are constant along magnetic field lines does not hold. Rather, the electron temperature and plasma potential vary significantly along the magnetic field - with a hot-spot of 40-100 eV electrons present in the center of the Hall thruster channel. A collisional argument is used to explain this thermal gradient in terms of restrictions on the heat flux term which are not currently captured by fluid models of these devices. To search for a low-fidelity approximation to this heat flow physics, the value of the effective polytropic index for thermodynamic electron expansion along magnetic field lines is investigated. and it is found that in the far-field plume, where plasma turbulence causes Bohm-like transport, the electron heat flux progresses from adiabatic to isothermal scaling.In addition to these time-averaged studies, time-resolved extensions of the LIF and ITS diagnostics investigated in Hall thruster plasmas, and an algorithm is presented for using "Shadow Manifold Interpolation" based on Takens's Theorem to map noisy pulsed diagnostics such as Thomson scattering to a noise-free reference signal, such as the discharge current, which globally represents the state of the thruster as a dynamical system. This nonlinear algorithm is validated against results using transfer function estimation, a standard linear method for reconstructing noisy datasets. Preliminary time-resolved Thomson scattering measurements show small fluctuations in the electron velocity distribution function, but more signal is necessary to truly resolve oscillations in the plasma to a useful degree. Time-resolved methods are leveraged for LIF investigations of the azimuthal ion waves which grow near the cathode of Hall thrusters, and the potential of these waves to cause erosion by energizing the ions is addressed.These results compose a series of novel insights about electron and ion flow physics both in the channel and cathode region of Hall thrusters. They are discussed in the context of present efforts to model Hall thruster particle flows with fluid-averaged approximations, and recommendations are made for capturing the electron physics reflected by these new diagnostic capabilities. Validation and comparisons are made between the Thomson scattering results and other methods to infer the electron temperatures, including estimation and Langmuir probe injection. Reasons for discrepancies between these high temperature measurements and past estimates of the electron temperature are discussed.
■590 ▼aSchool code: 0127.
■650 4▼aAerospace engineering
■650 4▼aPlasma physics
■653 ▼aHall thruster plasmas
■653 ▼aLow-density plasmas
■653 ▼aHall thruster operation
■653 ▼aCathode region
■690 ▼a0538
■690 ▼a0759
■71020▼aUniversity of Michigan▼bAerospace Engineering.
■7730 ▼tDissertations Abstracts International▼g86-11B.
■790 ▼a0127
■791 ▼aPh.D.
■792 ▼a2025
■793 ▼aEnglish
■85640▼uhttp://www.riss.kr/pdu/ddodLink.do?id=T17358079▼nKERIS▼z이 자료의 원문은 한국교육학술정보원에서 제공합니다.
