Single- and two-photon absorption laser-induced fluorescence spectroscopy in rare gases for gridded ion thruster diagnostics

Eichhorn, Christoph; Pietzonka, Lukas; Scholze, Frank; Bundesmann, Carsten; Spemann, D.; Neumann, H.; Leiter, Hans

doi:10.1140/epjti/s40485-022-00077-y

Cited by 7 publications

(2 citation statements)

References 79 publications

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“…The baseline is then subtracted from the averaged PMT trace. After baseline subtraction, the PMT trace is numerically integrated to form the TALIF signal, which is linearly proportional to the neutral Kr number density [26][27][28][29]. By examining these TALIF signals versus their assigned phase we can measure neutral density variation across a breathing mode cycle.…”

Section: Discussionmentioning

confidence: 99%

“…The present work extends our past use of two photon absorption laser induced fluorescence (TALIF) for reliable measurement of neutral populations [25][26][27] -by probing the ground state -but now for temporally resolved measurements relative to the breathing mode oscillation. The main advantage of TALIF for density measurements is that by using two-photon absorption we can access the relatively large energy gaps between the ground state and excited states, thereby accessing ground state transitions with available tunable laser systems typically operating in the range of ∼ 200-250 nm [25][26][27][28][29][30][31][32][33]. Two general disadvantages of TALIF detection are that signal-to-noise can be poor owing to small two-photon absorption cross-sections (and competing luminosity from the same emission lines) and that data is generally collected with low repetition-rate pulsed lasers (∼ 10-20 Hz).…”

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confidence: 99%

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Temporally resolved relative krypton neutral density during breathing mode of a hall effect thruster recorded by TALIF

Gottfried,

Antozzi,

Stienike

et al. 2024

J Electr Propuls

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A key issue in the development of theory and models for plasma propulsion devices is to describe the instabilities and fluctuations of the devices. It has been widely recognized that many Hall effect thrusters (HETs) exhibit oscillations at frequencies in the range of ∼ 20 kHz. These ionization-related oscillations are generally referred to as Breathing Mode oscillations and have been the subject of considerable research. Here, for the first time, we report direct temporally resolved measurements of the ground state neutral density variation during the period of the oscillation. We used the laser-based Two-Photon Absorption Laser Induced Fluorescence (TALIF) technique to measure neutrals within the plume of a 1.5 kW HET operating on krypton (Kr). Our TALIF scheme employs a frequency-doubled, pulsed dye laser operating at ∼ 212 nm to probe ground state Kr atoms. A novel phase-binning approach is used to recover the time-dependent signal by assigning the timing of each collected TALIF signal (laser shot) relative to the phase of the discharge current. We find that the neutral density fluctuates quite strongly over the period of the oscillation, and that this fluctuation leads the current fluctuation as expected.

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Section: Discussionmentioning

confidence: 99%

mentioning

confidence: 99%

Temporally resolved relative krypton neutral density during breathing mode of a hall effect thruster recorded by TALIF

Gottfried,

Antozzi,

Stienike

et al. 2024

J Electr Propuls

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Laser-induced fluorescence spectroscopy for kinetic temperature measurement of xenon neutrals and ions in the discharge chamber of a radiofrequency ion source

et al. 2023

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Application of single-photon absorption laser-induced fluorescence (LIF) spectroscopy for non-intrusive measurement of neutral xenon and singly charged xenon ion kinetic temperatures in the discharge chamber of a gridded radiofrequency ion source is demonstrated. A LIF spectrum analysis approach including hyperfine structure reconstruction and inverse filtering (Fourier deconvolution) is outlined. Special focus is set on optimization of post-deconvolution filtering as well as retracing of deconvolution result imperfection due to hyperfine structure parameter uncertainty, incorrect natural linewidth, and saturation of the LIF signal. The corresponding contributions to the kinetic temperature estimation error are quantified via simulation of spectral lineshapes. Deconvolution of almost unsaturated LIF spectra recorded in the center of the ion source discharge chamber reveals that the neutral xenon and xenon ion kinetic temperatures range between approximately 500 and 700 K and, respectively, 700 and 1000 K depending on the radiofrequency power supplied to the discharge.

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Diagnostics for electric propulsion systems

Kersten

2023

EPJ Techn Instrum

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Plasma-based electric propulsion (EP) by various kinds of thrusters is a rapidly growing technology for engines of satellites and space probes for near-Earth and space exploration. In order to optimize such propulsion systems in different regimes (from a few μN to several N of thrust), the availability of suitable and proper diagnostics as well as modelling is of fundamental importance. The diagnostics include, for example, electric, spectroscopic, calorimetric and momentum measurements during the development and design in the lab and during real operation under space conditions.Plasmas are generated by supplying energy to a volume containing a neutral gas, so that a certain fraction of free electrons and ions are generated from the neutral constituents. In technical plasma devices, the plasma is mostly generated in electrical discharges and the input energy is supplied in the form of electrical energy. The properties of non-equilibrium plasmas are discussed in many books and publications (see e.g. [1-5] and references therein), to which we refer the interested reader for further details. The generation and acceleration of ions away from the spacecraft to drive or affect it by momentum conservation are the crucial principles. Hence, topics of interest in this field of plasma research and application include aspects such as thrust measurements, plasma diagnostics, modelling and simulation of the involved species.The topical collection "Diagnostics for electric propulsion systems" which was launched in 2021 contains eight original articles. This collection is a current review of design and operating experience of related diagnostics and control systems of various thruster concepts and missions. One paper describes "Global models for radio-frequency ion thrusters" by P. Dietz et al. [6] and one (more general) paper is on perspectives of "Cluster of Electric Thrusters for Astronautic and Robotic INPPS Flagship Space Flights to Mars and Europa moon" by F. Jansen et al. [7]. In the other six papers, which are related to suitable diagnostics for EP, optical methods are discussed in the article "Non-invasive assessment of plasma parameters inside an ion thruster combining optical emission spectroscopy and principal component analysis" by B.T. Nauschütt et al. [8] and in the paper "Single-and two-photon laser-induced fluorescence spectroscopy in rare gases for gridded ion thruster diagnostics" by C. Eichhorn et al. [9]. Furthermore, common and novel probe diagnostics in typical test environments are studied in the work "Thrust measurement and thrust balance development at DLR's electric propulsion test facility" by A. Neumann et. al. [10] as well as in the paper "Force probes for the development and testing of different elec-

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Single- and two-photon absorption laser-induced fluorescence spectroscopy in rare gases for gridded ion thruster diagnostics

Cited by 7 publications

References 79 publications

Temporally resolved relative krypton neutral density during breathing mode of a hall effect thruster recorded by TALIF

Temporally resolved relative krypton neutral density during breathing mode of a hall effect thruster recorded by TALIF

Laser-induced fluorescence spectroscopy for kinetic temperature measurement of xenon neutrals and ions in the discharge chamber of a radiofrequency ion source

Diagnostics for electric propulsion systems

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