In situ observations of ions and magnetic field around Phobos: the mass spectrum analyzer (MSA) for the Martian Moons eXploration (MMX) mission

The mass spectrum analyzer (MSA) will perform in situ observations of ions and magnetic fields around Phobos as part of the Martian Moons eXploration (MMX) mission to investigate the origin of the Martian moons and physical processes in the Martian environment. MSA consists of an ion energy mass spectrometer and two magnetometers which will measure velocity distribution functions and mass/charge distributions of low-energy ions and magnetic field vectors, respectively. For the MMX scientific objectives, MSA will observe solar wind ions, those scattered at the Phobos surface, water-related ions generated in the predicted Martian gas torus, secondary ions sputtered from Phobos, and escaping ions from the Martian atmosphere, while monitoring the surrounding magnetic field. MSA will be developed from previous instruments for space plasma missions such as Kaguya, Arase, and BepiColombo/Mio to contribute to the MMX scientific objectives.

MATHEMATICAL MODEL OF THE INTERACTION OF LOW-ENERGY INERT GAS IONS WITH POLYPROPYLENE IN RADIO-FREQUENCY PLASMA OF LOW PRESSURE

Results of the molecular dynamic simulation of the interaction of low-energy ions (from 10 to 100 eV) with the surface of polypropylene fibrous materials in low pressure radio-frequency (RF) argon plasma is presented. A full-atomic model using the LAMMPS classical molecular dynamics code was made. As a result of numerical calculations, it was found that argon ion bombardment initiates the breaking both of an intermolecular and intramolecular bond of polypropylene with sputtered particles being the hydrocarbon radicals and single atoms. The depth of implantation of the ion is determined, the change in the kinetic energy of the argon atom and the temperature of the simulated cell is obtained.

Flow directions of low-energy ions in and around the diamagnetic cavity of comet 67P

The flow direction of low-energy ions around comet 67P/Churyumov-Gerasimenko has previously been difficult to constrain due to the influence of the spacecraft potential. The Ion Composition Analyzer of the Rosetta Plasma Consortium (RPC-ICA) on Rosetta measured the distribution function of positive ions with energies down to just a few eV/q throughout the escort phase of the mission. Unfortunately, the substantial negative spacecraft potential distorted the directional information of the low-energy data. In this work, we present the flow directions of low-energy ions around comet 67P, corrected for the spacecraft potential using Particle-In-Cell simulation results. We focus on the region in and around the diamagnetic cavity, where low-energy ions are especially important for the dynamics. We separate between slightly accelerated “burst” features and a more constant “band” of low-energy ions visible in the data. The “bursts” are flowing radially outwards from the nucleus with an anti-sunward component while the “band” is predominantly streaming back towards the comet. This provides evidence of counter-streaming ions, which has implications for the overall expansion velocity of the ions. The backstreaming ions are present also at times when the diamagnetic cavity was not detected, indicating that the process accelerating the ions back towards the comet is not connected to the cavity boundary.

Chromatic Change in Copper Oxide Layers Irradiated with Low Energy Ions

The color of a thin copper oxide layer formed on a copper plate was transformed from reddish-brown into dark blue-purple by irradiation with 5 keV Ar+ ions to a fluence as low as 1 × 1015 Ar+ cm−2. In the unirradiated copper oxide layer, the copper valence state of Cu2+ and Cu+ and/or Cu0 was included as indicated by the presence of a shake-up satellite line in a photoemission spectrum. While for the irradiated one, the satellite line decreased in intensity, indicating that irradiation resulted in the reduction from Cu2+ to Cu+ and/or Cu0. Furthermore, nuclear reaction analysis using a 16O(d, p)17O reaction with 0.85 MeV deuterons revealed a significant loss of oxygen (5 × 1015 O atoms cm−2) in the irradiated layer. Thus, the chromatic change observed in the present work originated in the irradiation-induced reduction of a copper oxide.

Chromatic Change in Copper Oxide Layers Irradiated with Low Energy Ions

The color of a thin copper oxide layer formed on a copper plate was transformed from reddish-brown into blue-purple by irradiation with 5 keV Ar+ ions to a fluence as low as 1 1015 Ar+ cm–2. In the unirradiated copper oxide layer, the copper valence state of Cu2+ as well as Cu+ and/or Cu0 was included as indicated by the presence of a shake-up satellite line in a photoemission spectrum. While for the irradiated one, the satellite line decreased in intensity, indicating that irradiation resulted in the reduction from Cu2+ to Cu+ and/or Cu0. Furthermore, nuclear reaction analysis using a 16O(d, p)17O reaction with 0.85 MeV deuterons revealed a significant loss of oxygen (51015 O atoms cm–2) in the irradiated layer. Thus, the chromatic change observed in the present work originated in the irradiation-induced reduction of a copper oxide.