Hydrogen Line Shapes in Plasmas with Large Magnetic Fields

We report on hydrogen line shape calculations in the presence of an external magnetic field, at conditions such that the quadratic Zeeman effect is important. The latter is described through a term proportional to B2 in the Hamiltonian, accounting for atomic diamagnetism. It provides a shift and an asymmetry on Lorentz triplets, and it leads to the occurrence of forbidden components. Motivated by investigations performed at the fifth edition of the Spectral Line Shape in Plasmas (SLSP5) code comparison workshop, we perform new calculations of hydrogen Lyman line profiles. Field values representative of magnetized white dwarf atmosphere conditions are taken. The calculations are done using a computer simulation technique, designed for Stark broadening modeling. A discussion of the results is done in the framework of plasma diagnostics.

Plasma Temperature and Electron Density Determination Using Laser-Induced Breakdown Spectroscopy (LIBS) in Earth’s and Mars’s Atmospheres

The purpose of this study was to calculate and compare the plasma temperatures and electron densities from the laser-induced breakdown spectroscopy (LIBS) data collected by NASA’s Martian rover and compare them to samples measured in Earth’s atmosphere. Using the Boltzmann plots, LIBS plasma temperatures were obtained for each site. The analysis focused on titanium lines that were located in the spectral region between 300 and 310 nm. The electron density was measured using the Stark broadening of the hydrogen line at 656.6 nm; the full width at half maximum (FWHM) of this line can be measured and correlated to the electron density of the plasma. Due to a neighboring carbon peak with the hydrogen line seen in many of the spectra from the Martian sites, the FWHM needed to be calculated using a computer program that completed the other side of the hydrogen line and then it calculated the FWHM for those data samples affected by this. The plasma temperatures and electron densities of the Martian sites were compared to LIBS samples taken on Earth.

Searching for ZZ Ceti white dwarfs in the Gaia survey

The Gaia satellite recently released parallax measurements for nearly 400,000 white dwarf stars, allowing for precise measurements of their physical parameters. By combining these parallaxes with Pan-STARRS and CFIS-u photometry, we measured the effective temperatures and surface gravities for all white dwarfs within 100 pc and identified a sample of ZZ Ceti white dwarf candidates within the instability strip. We report the results of a photometric follow-up, currently under way, aimed at identifying new ZZ Ceti stars among this sample using the PESTO camera attached to the 1.6-m telescope at the Mont Mégantic Observatory. Our goal is to verify that ZZ Ceti stars occupy a region in the logg-Teff plane where no nonvariable stars are found, supporting the idea that ZZ Ceti pulsators represent a phase through which all hydrogen-line (DA) white dwarfs must evolve.

Comparison of MC Geant4 simulation with the measurements of gamma photons produced by neutrons

In this work, we have focused on results of measurements of the hydrogen line 2223 keV and compared them with the results of Geant4 simulations. The paraffin containing hydrogen was irradiated by neutrons produced by the weak AmBe source. Produced gammas were measured with the germanium detector. The experimental setup was placed inside a carbon chamber which provided the shielding from the external neutrons. The measurements were performed for different amounts of paraffin. The processes playing a role in the description of our measurements are transport and moderation of neutrons, production of gamma rays in neutron-hydrogen interactions, transport and detection of gamma rays. It has been shown that the correctly carried out Monte Carlo simulations reproduced the measured values of the intensity of the observed gamma line 2223 keV from the neutron capture on hydrogen. The absorption of gamma rays is also described correctly. This has been shown in comparing the measurements of gamma line 322 keV from [Formula: see text]Pb with the simulations.