A Model of Spectral Line Broadening in Signal Forecasts for Line-intensity Mapping Experiments

Line-intensity mapping observations will find fluctuations of integrated line emission are attenuated by varying degrees at small scales due to the width of the line emission profiles. This attenuation may significantly impact estimates of astrophysical or cosmological quantities derived from measurements. We consider a theoretical treatment of the effect of line broadening on both the clustering and shot-noise components of the power spectrum of a generic line-intensity power spectrum using a halo model. We then consider possible simplifications to allow easier application in analysis, particularly in the context of inferences that require numerous, repeated, fast computations of model line-intensity signals across a large parameter space. For the CO Mapping Array Project and the CO(1–0) line-intensity field at z ∼ 3 serving as our primary case study, we expect a ∼10% attenuation of the spherically averaged power spectrum on average at relevant scales of k ≈ 0.2–0.3 Mpc−1 compared to ∼25% for the interferometric Millimetre-wave Intensity Mapping Experiment targeting shot noise from CO lines at z ∼ 1–5 at scales of k ≳ 1 Mpc−1. We also consider the nature and amplitude of errors introduced by simplified treatments of line broadening and find that while an approximation using a single effective velocity scale is sufficient for spherically averaged power spectra, a more careful treatment is necessary when considering other statistics such as higher multipoles of the anisotropic power spectrum or the voxel intensity distribution.

KAPPA: A Package for the Synthesis of Optically Thin Spectra for the Non-Maxwellian κ-distributions. II. Major Update to Compatibility with CHIANTI Version 10

KAPPA is a database and software for the calculation of the optically thin spectra for the non-Maxwellian κ-distributions that were recently diagnosed in the plasma of solar coronal loops, flares, as well as in the transition region. KAPPA is based on the widely used CHIANTI database and reproduces many of its capabilities for κ-distributions. Here we perform a major update of the KAPPA database, including a near-complete recalculation of the ionization, recombination, excitation, and deexcitation rates for all ions in the database, as well as an implementation of the two-ion model for calculations of relative-level populations (and intensities) if these are modified by ionization and recombination from or to excited levels. As an example of KAPPA usage, we explore novel diagnostics of κ, and show that O iii lines near 500 and 700 Å provide a strong sensitivity to κ, with some line intensity ratios changing by a factor of up to 2–4 compared to Maxwellian. This is much larger than previously employed diagnostics of κ.

Investigation of Shielding Effects on Picosecond Laser-Induced Copper Plasma Characteristics under Different Focusing Distances

In traditional laser-induced breakdown spectroscopy (LIBS) applications, the line intensity and analysis capability are susceptible to plasma shielding. To investigate the shielding effects on the characteristics of Cu plasma in air, a ~120-picosecond laser with a wavelength of 1064 nm was employed to produce plasma. The plasma temperature and electron density were calculated under the condition of local thermal equilibrium (LTE) and optically thin, while the relationships between the line intensity, plasma temperature and electron density were analyzed. Moreover, the LTE condition was validated by the McWhirter relation, plasma relaxation time and diffusion length, and the optically thin condition was observed through the variation in line intensity. The results indicated that when the focal point was below the target surface, the plasma shielding was the weakest, and the highest line intensity could be obtained. In addition, there was a positive correlation between the increased plasma temperature and the degree of shielding effect. When the focal point was above the target surface, the high-irradiance pulse directly broke down the free air and produced a shock wave. Under the high pressure of the over-heated shock wave, the line intensity, plasma temperature and electron density increased again. This study provides an important insight into the experiments and applications of picosecond LIBS.

Optimizing the Teflon thickness for fast neutron detection using a Ge detector

The optimum Teflon (C2F4)n thickness for fast neutron detection through the 19F(n,α)16N reaction was calculated and found to be ≈ 5.0 cm. Here, the 6.13 MeV γ ray emitted by 16N is assumed to be detected by a Ge diode. The geometry of the system is discussed and the γ line intensity was found to vary weakly with Teflon thickness.

Charge-exchange soft x-ray emission of highly charged ions with inclusion of multiple-electron capture

Charge-exchange has been recognized as a primary source of soft x-ray emission in many astrophysical outflow environments, including cometary and planetary exospheres impacted by solar wind. Some models have been setup by using different data collections of charge-exchange cross-sections. However, multiple electron transfer has not been included in these models. In this paper, we setup a charge exchange model with the inclusion of double-electron capture, and make a detailed investigation of this process on x-ray emissions of highly charged carbon, nitrogen, oxygen and neon ions by using available experimental cross-sections. We also study the effect of different n −selective cross-sections on soft x-ray emission by using available experimental n −distributions. This work reveals that double electron capture enhancement on line intensity is basically linearly proportional to the ratio of ion abundance in the solar wind. It is more obvious for soft x-rays from carbon ions (C4 +) in collision with CO2, and the enhancement on line intensity can be up to 53 per cent with typical ion abundances (ace observation) in solar wind. The synthetic spectra with parameters from the Ulysses mission for solar wind reveals velocity-dependence, target-dependence, as well as the non-negligible contribution from the double-electron capture.

EUV Beam-Foil Spectra of Titanium, Iron, Nickel, and Copper

Beam–foil spectroscopy offers the efficient excitation of the spectra of a single element as well as time-resolved observation. Extreme-ultraviolet (EUV) beam–foil survey and detail spectra of Ti, Fe, Ni, and Cu are presented, as well as survey spectra of Fe and Ni obtained at an electron beam ion trap. Various details are discussed in the context of line intensity ratios, yrast transitions, prompt and delayed spectra, and intercombination transitions.