Analysis Electron Research Articles

Electron Temperatures in the Venusian Ionosphere From Parker Solar Probe Using Quasi‐Thermal Noise Spectroscopy

AbstractParker Solar Probe (PSP) uses Venus gravity assists (VGA) to achieve the closest orbits to the Sun by a spacecraft. During the third (VGA3) and fourth (VGA4) Venus gravity assists, the PSP entered the Venusian ionosphere. The core electrons could not be detected as they were below the SWEAP/SPAN electrostatic analyzer instrument energy threshold. However, there is another way to estimate the core temperature using quasi‐thermal noise (QTN) data measured by the PSP/FIELDS Radio Frequency Spectrometer instrument. QTN spectroscopy offers an effective tool for measuring electron temperature and density when the electrons are too cold for other instruments to measure, as is the case with VGA3 and VGA4. Low‐frequency plasma wave data from the closest approach during VGA3 and VGA4 was analyzed with the QTN spectroscopy technique to determine the density and first‐ever in‐situ thermal electron temperature of the Venusian ionosphere at solar minimum.

Spaceborne particle identification platform and its application based on convolutional neural network

The identification of particle types in space radiation particle detection is a problem of great concern in scientific research and engineering applications. At present, the particle types are mainly identified by the difference in energy deposition of particles in the sensor, the difference in waveform in the sensor, the flight time and energy of particles, and the difference in the deflection path of particles in the electric field, such as traditional telescope detectors, particle pulse waveform analysis, flight time TOF system and electrostatic analyzer. However, the current on-orbit particle identification logic is relatively simple and the identification accuracy is limited. Convolutional neural networks have powerful target classification capabilities and are good at capturing and extracting target feature details, which can improve the accuracy of particle energy measurement and identification. Based on the environment commonly used in space environment detection payloads, this paper proposes a method for building an on-orbit convolutional neural network particle identification platform to achieve particle type identification. The platform first constructs a multi-dimensional input data set, completes the model training and weight derivation with the help of the software platform, and completes the waveform inference and data set expansion through the hardware platform. The established identification platform is used to train and test the neutron and gamma waveform data obtained in actual tests, and the accuracy of the identification of the software and hardware platforms is analyzed, completing the verification of the platform. The establishment and application of this platform provides a new idea and method for particle measurement and identification in future space environment detection, and has strong engineering practice significance.

Research on a miniature Mattauch-Herzog mass spectrometer designed for space exploration

Mass spectrometers have gained increasing importance in recent space missions. This paper presents the development of a miniature Mattauch-Herzog mass spectrometer for mass analysis. The mass spectrometer consists of an electron ionization (EI) source, an electrostatic and magnetic mass analyzer, and a focal plane detector. The construction of the EI source is based on a study of the impact of electrode voltages on ion focusing performance and ion transmission efficiency using the phase space method in the SIMION-8.1 software. The SIMION model of the mass analyzer is utilized to analyze the effects of electrostatic field voltage and magnetic fringe field on the ion beam. Experimental results from the instrument prototype demonstrate that the ion beam is influenced by the electrostatic field in a manner consistent with the simulation results of the SIMION model. The theoretical mass-to-charge ratio range of this double focusing mass spectrometer (DFMS) is 8amu–300amu, and it is capable of distinguishing isotopes with mass differences larger than 0.3amu, such as Ne. The N2 peak width at Full Width Half Maximum (FWHM) is 0.4amu, the mass resolution is 70.0, and the minimum detectable pressure of N2 is 2.8 × 10−9Pa. The Xe peak width (FWHM) is 1.3amu, the mass resolution is 101.5, and the minimum detectable pressure of Xe is 4.4 × 10−9Pa.

On the reconstruction of LEIS spectra after distortion by an electrostatic energy analyzer

The study attempts to reveal the influence of the transmission function of electrostatic deflector analyzers with linear voltage scan on the shape of the LEIS energy spectra and the arising error in surface elemental composition and film thickness analysis. The practical applicability of several analytical and numerical approaches for reconstructing true energy distributions of particles is studied using examples of simulated LEIS spectra. The presented methodology can be extended to a wider range of applications involving electrostatic or magnetic analyzers of charged particles. The study proposesa freely available and ready-to-use tool for simulating distortions of spectra caused by the transmission function of spectrometers and for reconstructing true distributions of arbitrary spectra.

Energy-Resolving Time-of-Flight Mass Spectrometry for Bulk Plasma Analysis.

This work presents a newly designed energy-resolving time-of-flight mass spectrometer (E-TOFMS) for analysing the energy and mass of ions in bulk plasma. The system comprises an electrostatic sector analyser (ESA) for energy-to-charge (E/Q) ratio resolution and an orthogonal reflectron TOFMS for mass-to-charge (m/Q) ratio analysis. The design choices are explained, providing insight into electron and ion path simulations. The instrument was characterised using various ion generation sources, including an electron impact ion source, high power impulse magnetron sputtering, and microwave plasma electron cyclotron resonance sources. To validate its functionality, the energy-resolving data was compared with data obtained under the same conditions using a Langmuir probe and a retarding field energy analyser (RFEA). The benefits of the proposed E-TOFMS were demonstrated by sputtering highly alloyed steel with multiple isotope-rich elements, such as Mo or W. This technique offers an E/Q ratio resolution of up to 0.15 V for a range up to 125 V and a m/Q ratio resolution of at least 700 Th for a range up to 250 Th, with a temporal resolution of 10 μs.

Effect of external electric field on copper/silica contact electrification and adhesion: insight from first-principles and molecular mechanics investigations

The electrostatic force induced by charge transfer during contact electrification is one of the main components of adhesion force at the solid interface. Some studies found that the magnitude of charge transfer and the consequently electrostatic force can be tuned by the external electric field. However, the detailed mechanism is still lacking in understanding. In this study, the effect of external electric field on copper/silica contact electrification and adhesion is studied via first-principles and molecular mechanics calculations and the mechanism is revealed by electrostatic potential and adhesion energy analysis. It is proved that the external electric field can affect the contact potential difference, which is the driving force of contact electrification, thus influencing the magnitude of charge transfer and electrostatic force. When the electric field direction is the same as the electron transfer direction, the contact electrification can be suppressed, leading to the decrease in the ratio of electrostatic force to van der Waals force. In particularly, the contact electrification and electrostatic force can be completely eliminated when applying a specific electric field intensity. This can provide an inspiration for quantitatively studying the source of adhesion force at solid interface.

The investigation of traceable preparation technique of submicron particle number concentration standards in liquids

The concentration of particles at the nano- and submicron-meter scale in liquid is crucial in multiple fields including the biomedical and semiconductor industry. However, there is still a lack of metrological standards or Certified Reference Materials (CRMs) for liquid-borne particle number concentration (PNC) which could be traceable to the International System of Units (SI). To address this issue, a quantitative and value-traceable preparation technique for liquid-borne particle number concentration CRMs (PNC-CRMs) in a submicron-meter scale based on controllable aerosol generation and collection was developed in this study. In this technique, by using commercial differential electrostatic mobility analyzer (DMA) and calibrated condensation particle counter (CPC), monodisperse aerosol particle with known concentration was initially generated. Then for quantitatively transforming the aerosol particles to the liquid, an aerosol particle collection system was designed and developed by hydrodynamic (CFD) simulations and experiment conducting, and crucial parameters of the collection system, e.g. the nozzle diameter of the aerosol particle outlet, the distance from the nozzle to the liquid surface, and the state of the liquid interface, were investigated and optimized. Under the optimized collected parameters, the collection efficiency for aerosol particles of the newly-developed system could reach over 90%. Because the PNC in aerosol is SI-traceable, combined with the obtained collection efficiency and collection time, the PNC in the collection liquid with could be obtained finally and trace to SI unit. Using this technique, two kinds of PNC-CRMs with nominal sizes of 100 and 500 nm were developed successfully, where, certified values were (7–9) × 106 particles/mL and 1.7 × 106 particles/mL, and standard uncertainties are 4.2%.

Study of atoms and multiply charged ions features in the nanosecond laser produced Mo plasma in vacuum using optical emission spectroscopy and time-of-flight electrostatic energy analyzer

The species including atoms and multiply charged ions in the laser produced molybdenum (Mo) plasma are investigated in this work using optical emission spectroscopy and time-of-flight electrostatic energy analyzer (TOF-EEA). Nanosecond laser (5 ns, 1064 nm,) pulses were focused on the Mo target surface with a spot size of 0.4 mm2, energy of ∼150 mJ/pulse (corresponding to a power density of ∼7.5 GW cm−2) to generate the Mo plasma in vacuum environment. Time-resolved spectral analysis was carried out to investigate the temporal evolution of continuous background, atomic, and monovalent ionic spectral signals. The Saha–Boltzmann method is applied for spectral fitting, providing insight into the temporal evolution of electron temperature (T e) and electron density (n e). Over the time from 40 ns to 500 ns, the T e decreases from 3.6 eV to 0.52 eV, and the n e decreases from 2.5 × 1020 cm−3–1.0 × 1015 cm−3. Linear fitting extrapolation predicts the T e and n e could be even up to 6.3 eV and 2.5 × 1022 cm−3, respectively, at the early stage of 10 ns. This indicates the generation of multiply charged ions during the laser ablation process. The multiply charged ions up to 6 charge states were observed by the TOF-EEA and the energy distributions for the different charged ions were also obtained. It was found the ion kinetic energy is positively related to the number of charge state indicates the existence of acceleration electric field. The equivalent accelerating potential is determined as approximately 570 V at the current laser power density. This research provides a significant reference for the establishment of models for laser ablation plasmas and a profound understanding of the underlying physical processes.

The Vulcan Mission to Io: Lessons Learned during the 2022 JPL Planetary Science Summer School

A mission to Jupiter's moon Io, the most volcanically active body in the solar system, was suggested as a priority for the New Frontiers program in the 2013 Planetary Science Decadal Survey. We present a New Frontiers–class mission concept, Vulcan, that was designed as an educational exercise through the Jet Propulsion Laboratory’s 2022 Planetary Science Summer School. Vulcan would leverage an instrument suite consisting of wide- and narrow-angle cameras, a thermal infrared spectrometer, two fluxgate magnetometers, and ion and electron electrostatic analyzers to conduct the most thorough investigation of Io to date. Using 78 flybys over a 2 yr primary science mission, Vulcan would characterize the effects of tidal forces on the differentiation state, crustal structure, and volcanism of Io and investigate potential interactions between Io's volcanoes, surface features, and atmosphere. Although Vulcan was developed as an academic exercise, we show that a New Frontiers–class mission to Io could achieve transformative science in both geophysics and plasma physics, unifying typically disparate subfields of planetary science. A dedicated mission to Io, in combination with the Europa Clipper and Jupiter Icy Moons Explorer missions, would address fundamental questions raised by the 2023 Planetary Science Decadal Survey and could complete our understanding of the spectrum of planetary habitability. Lessons learned from Vulcan could be applied to a New Frontiers 5 Io mission concept in the near future.

Radiative emissions from charge exchange processes in collisions of 0.7–10.0 keV He[formula omitted] with N[formula omitted] and O2 molecules

We present an experimental study of the dissociative excitation in the collision of helium ions with nitrogen and oxygen molecules for collision energy of 0.7–10.0 keV. Absolute emission cross sections are measured and reported for the most pronounced nitrogen and oxygen atomic and ionic lines in vacuum ultraviolet (80–130nm) and visible (380–670nm) spectral regions. Remarkable similarities of the processes realized in He++N2 and He++O2 collision systems are observed. We present polarization measurements for He++N2 collision system.The emission of excited dissociative products was detected using an improved high-resolution optical spectroscopy method. This method incorporates the retarding potential method and a high resolution electrostatic energy analyzer to precisely measure the energy of incident particles and the energy of dispersion. The improvement in the optical sensitivity allows us to measure the cross section on the order of 10−19 cm2 or lower.

A Study of Ionospheric Heavy Ions in the Terrestrial Magnetotail Using ARTEMIS

AbstractIonospheric heavy ions in the distant tail of the Earth's magnetosphere at lunar distances are observed using the ARTEMIS mission. These heavy ions are originally produced in the terrestrial ionosphere. Using the ElectroStatic Analyzers (ESA) onboard the two probes orbiting the Moon, these heavy ions are observed as cold populations with distinct energies higher than the baseline energy of protons, with the energy‐per‐charge values for the heavy populations highly correlated with the proton energies. We conducted a full solar cycle survey of these heavy ion observations, including the flux, location, and drift energy, as well as the correlations with the solar wind and geomagnetic indices. The likelihood of finding these heavy ions in the preferred regions of observation called “loaded” quadrants of the terrestrial magnetotail is ∼90%, regardless of the z orientation of the IMF. We characterize the ratio of the heavy ion energy to the proton energy, as well as the velocity ratio of these two populations, for events from 2010 to mid‐2023. This study shows that the “common velocity” assumption for the proton and heavy ion particles, as suggested in previous work through the velocity filter effect, is not necessarily valid in this case. Challenges in the identification of the mass of the heavy ions due to the ESA's lack of ion composition discrimination are addressed. It is proposed that at the lunar distances the heavy ion population mainly consists of atomic oxygen ions (O+) with velocities ∼25% more than the velocity of the co‐located proton population.

Tandem Energy-Analyzer/Mass-Spectrometer Measurements of an Ionic Liquid Ion Source

Ionic liquid ion sources (ILISs) produce charged particle beams by using a strong electric field to extract and accelerate molecular ions and ion clusters from liquid propellant. The wide variety of emitted species and the fragmentation of metastable ion clusters lead to broad distributions of energy and mass among plume species. Quantifying those distributions is critical to understanding ILIS physics and ILIS performance in a particular application. Here, we use an electrostatic energy analyzer in tandem with a mass spectrometer (EA/MS) to measure mass spectra for various energy ranges in the plume of an ILIS operating with the electrospray propellant EMI-BF4. Those spectra were used to calculate energy distributions for major plume species, probed at the entrance of the EA/MS instrument. Those measurements suggest that 12% of the plume (by current fraction) is composed of species formed by ion clusters that fragment more than once prior to reaching the instrument. For the first time, we estimate the composition of the plume within the electric field of the ion source from experimental measurements. That analysis shows that at least 10% of plume current was emitted as trimers, and more than 3% was emitted as larger species.

A low-energy particle experiment for both ion and electron measurements using a single microchannel plate-based detector

We have developed a low-energy particle experiment that alternately measures ions and electrons in space. The ability to switch between ion and electron measurements is achieved by simply adding ultra-thin carbon foils and positive and negative outputs to a conventional top-hat electrostatic analyzer and a high-voltage power supply, respectively. The advantage of this experiment is that it can perform both ion and electron measurements using only one MCP-based detector for electrons, since it detects secondary electrons emitted from the carbon foils. For the SS520-3 sounding rocket program, we prepared two identical energy analyzers, one for ions and the other for electrons to demonstrate this technique. Laboratory tests confirmed that the performance of the two analyzers was comparable to that of conventional analyzers for ion and electrons. The SS520-3 rocket experiment in the high latitude auroral region yielded observations that captured typical features of ions and electrons, which were similar to previous observations.Graphical

Plasma Observations in the Distant Magnetotail During Intervals of Northward IMF

AbstractWe examine a 6‐day traversal of the magnetotail by the ARTEMIS satellites during an interval of prolonged northward IMF. The electrostatic analyzer (ESA) onboard the ARTEMIS spacecraft measures high ion and electron fluxes at approximately 60 RE downtail in regions of the magnetotail which would normally be the magnetotail lobe, containing open flux evacuated of plasma. We interpret these observations as trapped plasma on closed magnetic flux indicating that the magnetotail is closed or partially closed but extends at least as far as ∼60 RE downtail. We find that the occurrence of plasma in the magnetotail and the closure of the magnetosphere results in distinct changes to the magnetotail structure including a reduction in the magnetic field strength and pressure as well as a narrowing of the tail by approximately 20 RE.

Electrostatic Dust Analyzer for Dust Transport Measurements on the Lunar Surface

Lunar dust charging and transport is a more than five-decade-old problem. A high-fidelity and flight-qualified Electrostatic Dust Analyzer (EDA) has been developed to measure the charge, velocity, mass (size), and flux of electrostatically lofted dust particles on the lunar surface. Recent laboratory findings have greatly advanced our fundamental understanding of the dust-charging and -lofting mechanisms, providing critical constraints to the design of the EDA instrument. EDA consists of two identical dust trajectory sensor (DTS) units on both ends of the instrument with a deflection field electrode (DFE) unit lying in between. When a dust particle enters the instrument, charge signals induced on four arrays of wire electrodes in the two DTS units determine the total charge of the dust particle and its trajectory passing through the instrument from which the dust velocity vector is measured. The mass (size) is derived from the deflection of the dust trajectory by the DFE. A dust campaign was performed to characterize the instrument’s performance. The results meet or exceed the requirements. EDA has achieved high Technology Readiness Level 6. EDA measurements are important for assessing the dust environment on the lunar surface and its subsequent impact on crew safety and the operation of exploration systems. Additionally, EDA measurements are expected to have important implications for the surface evolution of all airless bodies, including the Moon and asteroids, in the solar system.

High-Resolving Conical Electrostatic Energy Analyzer for Plasma Flows Investigations

The paper presents numerically calculated model of the new electrostatic energy analyzer based on a bounded conical field, separating and focusing a flow of charged particles, having velocity parallel or nearly parallel to the axis of symmetry of the analyzer. The calculations show second order focusing with very large acceptance aperture, what is important for obtaining accurate data of intensity, energy characteristics, main direction of space particle flows, which are characterized by very low density. These data are important for monitoring and forecasting abnormal electromagnetic events over the Earth and nearEarth space which can effect on normal operation and even on the safety of the crew of space station. A combination of high energy resolution with large aperture, simple compact design and control and remote fine tuning makes the instrument very promising for space technologies

New Data on Autoionizing States of Ne Induced by Low-Energy Electrons from 45 to 64 eV

The lowest single and doubly excited autoionizing states of neon have been studied using a non-monochromatic electron beam and a high-resolution electrostatic analyzer at incident electron energies from 43.37 to 202 (±0.4) eV at three ejection angles, 40°, 90° and 130°. The 2s2p63s(3,1S) and 2s2p63p(3,1P) as well as the 2p43s3p doubly excited states have been observed and their energy determined. The influence of the PCI effect in the energy region of the 2s2p63s(3,1S) states has been investigated. New features in the ejected electron spectra in the low kinetic energy region 3–20 eV at 202 eV incident energy have been observed and assigned.

Demonstration of a Multi‐Layer, Lithographically Manufactured Plasma Spectrometer

AbstractDevelopment of new plasma instruments is needed to enable constellation‐ and small satellite‐based missions. Key steps in the development pathway of ultra‐compact plasma instruments employing lithographically patterned wafers are the implementation of layer‐to‐layer electrical interconnects and demonstration of massively parallel measurements, that is, simultaneous measurements through multiple identical plasma analyzer structures. Here we present energy resolved measurements of electron beams using a 5‐layer stack of wafer‐based, energy‐per‐charge, electrostatic analyzers. Each layer has eight distinct analyzer groups that are comprised of multiple micron scale energy‐per‐charge analyzers. The process of fabricating the electrical interconnects between the layers is described and the measured energy resolution and the angular resolution compared to theoretical predictions. The measurements demonstrate successful operation of 400 micron scale analyzers operating in parallel.

Time-varying mechanism of ion composition in a pulse-modulated Ar/C4F8/O2 dual-frequency capacitively coupled plasma

The time-varying mechanism of the positive-ion composition in a pulse-modulated Ar/C4F8/O2 dual-frequency capacitively coupled plasma was investigated in detail using a quadrupole mass spectrometer equipped with an electrostatic energy analyzer. Time-resolved measurements of the ion composition with respect to the pulse-off period ( Toff ) revealed that the electron temperature ( Te ) just after turning on the pulse is an important factor in determining the ratio of the ionization rates of the Ar+ and C x F y + ions. The time-varying phenomenon of the ion composition was also investigated through a numerical analysis based on the particle balance model, considering the production and loss rates of ions, ion–ion recombination processes, and ion–molecule reactions. When the VHF power ( PVHF ) was increased, a decrease in the ambipolar diffusion loss time constants of the ions ( τlossi ) was observed, and the change in electronegativity was pointed out as the cause of this phenomenon.

Ion concentration ratio measurements of ion beams generated by a commercial microwave electron cyclotron resonance plasma source.

A commercially available electron cyclotron resonance (ECR) plasma source (GenII Plasma Source, tectra GmbH) is widely used for surface processing. This plasma source is compatible with ultrahigh vacuum systems, and its working pressure is relatively low, around 10-6-10-4 Torr even without differential pumping. Here, we report ion flux concentration ratios for each ion species in an ion beam from this source, as measured by a mass/energy analyzer that is a combination of a quadrupole mass spectrometer, an electrostatic energy analyzer, and focusing ion optics. The examined beams were those arising from plasmas produced from feed gases of H2, D2, N2, O2, Ar, and dry air over a range of input power and working pressures. H2(D2) plasmas are widely used for nuclear fusion applications and, hence, the ion concentration ratios of H+, H2+, and H3+ reported here will be useful information for research that applies this plasma source to well-controlled plasma-material interaction studies. Ion energy distributions, stability of operation, and impurity concentrations were also assessed for each of the plasma species investigated.