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Results for “production of ions”

Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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At least 19 records
All sourcesNASA NTRSDOE OSTI
NASA NTRS1992

An experimental study of impingement-ion-production mechanisms

A simple model for the production of ions that impinge on and sputter erode the accelerator grid of an ion thruster is presented. Charge-exchange and electron-impact ion production processes are considered, but experimental results show the charge-exchange process dominates. Additional experimental results show the effects of changes in thruster operating conditions on the length of the region from which these ions are drawn upstream into the grid. Results which show erosion patterns and indicate molybdenum accelerator grids erode more rapidly than graphite ones are also presented.

Monheiser, Jeff M.↗
DOE OSTI2025

Product ion distributions using H 3 O + proton-transfer-reaction time-of-flight mass spectrometry (PTR-ToF-MS): mechanisms, transmission effects, and instrument-to-instrument variability

Abstract. Proton-transfer-reaction mass spectrometry (PTR-MS) using hydronium ion (H3O+) ionization is widely used for the measurement of volatile organic compounds (VOCs) both indoors and outdoors. H3O+ ionization, as well as the associated chemistry in an ion–molecule reactor, is known to generate product ion distributions (PIDs) that include other product ions besides the proton-transfer product. We present a method, using gas-chromatography pre-separation, for quantifying PIDs from PTR-MS measurements of nearly 100 VOCs of different functional types including alcohols, ketones, aldehydes, acids, aromatics, organohalides, and alkenes. We characterize instrument configuration effects on PIDs and find that reactor reduced electric field strength (E/N), ion optic voltage gradients, and quadrupole settings have the strongest impact on measured PIDs. Through an interlaboratory comparison of PIDs measured from calibration cylinders, we characterized the variability of PID production from the same model of PTR-MS across seven participating laboratories. Product ion variability was generally smaller (e.g., < 20 %) for ions with larger contributions to the PIDs (e.g., > 0.30) but less predictable for product ions formed through O2+ and NO+ reactions. We present a publicly available library of H3O+ PTR-MS PIDs that will be updated periodically with user-provided data for the continued investigation into instrument-to-instrument variability of PIDs.

Link, Michael F. (ORCID:0000000218412455)↗
NASA NTRS1981

Meteoric ion production near Jupiter

Meteoric ion layer formation within the Jovian atmosphere is examined with attention to metallic ion production in the lower ionosphere. The Fe(+) impact ionization rate within the Jovian atmosphere peaks above the mesopause with a magnitude of approximately 0.5 cu cm/sec and is much less than the ambient ionosphere photoionization rates near the late afternoon Pioneer 10 ionosphere occultation. Charge exchange of the ablated neutral Fe atoms with ambient ions can result in an Fe(+) production rate of about 10 cu cm/sec. Ignoring transport, steady state Fe(+) density maxima of about 10,000 or 1,000,000 cu cm can be maintained when Fe(+) loss is through radiative association or radiative recombination respectively. Even if an estimated lower limit to the incident meteoroid flux is used based on a meteoroid spatial density which does not vary with distance from the sun, the corresponding Fe(+) peak densities are 1,000 and 500,000 cu cm, respectively. Meteoric ion densities may thus be important in the Jovian lower ionosphere.

Grebowsky, J. M.↗
NASA NTRSDate not supplied

DDFRG: Double Differential FRaGmentation Models for Proton and Light Ion Production in High Energy Nuclear Collisions: Closed Form, Analytic Formulas for Transport Codes and other Applications

New models for Double-Differential FRaGmentation (DDFRG) cross sections for proton and light ion production from high energy nucleus-nucleus collisions are developed. The proton model employs thermal production from the projectile, central fireball and target sources, and also quasi-elastic direct knockout production. Light ion production cross sections employ a hybrid coalescence model. The models are able to describe a wide range of experimental data with only a limited set of model parameters. Closed form analytic formulas for double-differential cross sections as well as single-differential energy cross sections are developed. The analytic formulas enable highly efficient computation for space radiation transport codes and other applications.

John W Norbury↗
DOE OSTI2023

Investigating radioactive negative ion production via double electron capture

The relative cross sections for radioactive negative ion production via double electron capture have been measured for collisions between a 40 keV projectile beam of uranium-238 and potassium vapor. This was performed at the collinear resonance ionization spectroscopy (CRIS) experiment at CERN-ISOLDE and is a step towards measuring the electron affinities (EAs) of elements that cannot be efficiently produced in negative ion sources at radioactive ion beam (RIB) facilities. This includes short-lived radioactive isotopes that have low production quantities and heavy and superheavy elements that systematically have smaller EAs than work functions of available ion source materials. Negative ions are particularly sensitive to electron–electron correlation effects, which make such studies ideal for benchmarking atomic structure models that go beyond the independent particle model. While the EAs of most light elements have been measured, experimental investigations on heavier elements, namely the actinides, remain scarce due to their radioactive nature and production difficulty. By developing negative ion production by charge exchange, we aim to make these studies feasible at RIB facilities.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
NASA NTRS2007

Potential Fluctuations and Energetic Ion Production in Hollow Cathode Discharges

Ions with energies significantly in excess of the applied discharge voltage have been reported for many years in hollow cathode discharges. Models of dc potential hills downstream of the cathode and instabilities in postulated double layers in the cathode orifice have been proposed to explain this, but have not been substantiated. Measurements of the dc and rf plasma density and potential profiles near the exit of hollow cathodes by miniature fast-scanning probes suggests that turbulent ion acoustic fluctuations and ionization instabilities in the cathode plume significantly increase the energy of the ions that flow from this region. Increases in the discharge current and/or decreases in the cathode gas flow enhance the amplitude of the fluctuations and increase the number and energy of the energetic ions, which increases the erosion rate of the cathode electrodes. The transition from the quiescent 'spot mode' to the noisy 'plume mode' characteristic of these discharges is found to be a gradual transition of increasing fluctuation amplitudes.

keeper↗
DOE OSTI2021

Heavy-ion production of 77 Br and 76 Br

Many radioisotopes with potential medical applications are difficult to produce routinely, especially those on the proton-rich side of the valley of stability. Current production methods typically use light-ion (protons or deuteron) reactions on materials of similar mass to the target radioisotope, which limits the elemental target material available and may require the use of targets with poor thermal properties (as is the case for the production of radiobromine). These reactions may also create significant amounts of proton-rich decay products which require chemical separation from the desired product in a highly radioactive environment. A promising alternative method using heavy-ion fusion-evaporation reactions for the production of the medically relevant bromine radioisotopes 76 Br (t 1/2 = 16.2 h) and 77 Br (t 1/2 = 57.0 h) is presented. Heavy-ion beams of 28 Si and 16 O were used to bombard natural chromium and copper targets just above the Coulomb barrier at the University of Notre Dame's Nuclear Science Laboratory to produce these bromine and precursor radioisotopes by fusion-evaporation reactions. Production yields for these reactions were measured and compared to PACE4 calculations. In addition to using more robust targets for irradiation, a simple physical–chemical separation method is proposed that will lead to very high radiopurity yields. A summary of accelerator facility requirements needed for routine production of these radioisotopes is also presented.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
NASA NTRS2005

Energetic ion production and electrode erosion in hollow cathode discharges

Ions with energies significantly in excess of the discharge voltage have been reported in high current hollow cathode discharges. Models of DC potential hills downstream of the cathode and ion acoustic instabilities in a double layer postulated in the cathode orifice have been proposed to explain these energetic ions, but have not been substantiated in experiments.

ion thruster↗
DOE OSTI2021

Role of Decomposition Product Ions in Hysteretic Behavior of Metal Halide Perovskite

Ion migration is one of the most debated mechanisms and credited with multiple observed phenomena and performance in metal halide perovskites (MHPs) semiconductor devices. However, to date, the migration of ions and their effects on MHPs are not still fully understood, largely due to a lack of direct observations of temporal ion migration. In this work, using direct observation of ion migration in-operando, we observe the hysteretic migration behavior of intrinsic ions (i.e., CH 3 NH 3 + and I – ) as well as reveal the migration behavior of CH 3 NH 3 + decomposition ions. We find that CH 3 NH 3 + decomposition products can be affected by light and accumulate at the interfaces under bias. These MHP decomposition products are tightly related to the device performance and stability. Complementary results of time-resolved Kelvin probe force microscopy (tr-KPFM) demonstrate a correlation between dynamics of these interfacial ions and charge carriers. Overall, we find that there are a number of mobile ions including CH 3 NH 3 + decomposition products in MHPs that need to be taken into account when measuring MHP device responses (e.g., charge dynamics) and should be considered in future optimization studies of MHP semiconductor devices.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
NASA NTRS1976

Double ion production in mercury thrusters

The development of a model which predicts doubly charged ion density is discussed. The accuracy of the model is shown to be good for two different thruster sizes and a total of 11 different cases. The model indicates that in most cases more than 80% of the doubly charged ions are produced from singly charged ions. This result can be used to develop a much simpler model which, along with correlations of the average plasma properties, can be used to determine the doubly charged ion density in ion thrusters with acceptable accuracy. Two different techniques which can be used to reduce the doubly charged ion density while maintaining good thruster operation, are identified as a result of an examination of the simple model. First, the electron density can be reduced and the thruster size then increased to maintain the same propellant utilization. Second, at a fixed thruster size, the plasma density, temperature and energy can be reduced and then to maintain a constant propellant utilization the open area of the grids to neutral propellant loss can be reduced through the use of a small hole accelerator grid.

Peters, R. R.↗
NASA NTRS2006

Description of Light Ion Production Cross Sections and Fluxes on the Mars Surface using the QMSFRG Model

The atmosphere of Mars significantly attenuates the heavy ion component of the primary galactic cosmic rays (GCR), however increases the fluence of secondary light ions (neutrons, and hydrogen and helium isotopes) because of particle production processes. We describe results of the quantum multiple scattering fragmentation (QMSFRG) model for the production of light nuclei through the distinct mechanisms of nuclear abrasion and ablation, coalescence, and cluster knockout. The QMSFRG model is shown to be in excellent agreement with available experimental data for nuclear fragmentation cross sections. We use the QMSFRG model and the space radiation transport code, HZETRN to make predictions of the light particle environment on the Martian surface at solar minimum and maximum. The radiation assessment detector (RAD) experiment will be launched in 2009 as part of the Mars Science Laboratory (MSL). We make predictions of the expected results for time dependent count-rates to be observed by RAD experiment. Finally, we consider sensitivity assessments of the impact of the Martian atmospheric composition on particle fluxes at the surface.

Cucinotta, Francis A.↗
DOE OSTI2021

A heavy-ion production channel of 149 Tb via 63 Cu bombardment of 89 Y

We report the radionuclide 149 Tb (t 1/2 = 4.1 h) is a potential theranostic isotope which can simultaneously be used for targeted-alpha-particle therapy and positron-emission tomography. Feasibility experiments were performed to test a near-symmetric heavy-ion reaction of 63 Cu bombardment on monoisotopic 89 Y. The indirect reaction was studied to avoid isomer production. Offline gamma spectroscopy was used to quantify thick-target physical yields and experimental results show modest agreement to the fusion-evaporation code PACE4. A near-symmetric fission yield was also observed.

149Tb↗