Abstract

Poster - Splinter General   (MW-1801 / virtual plenum)

Probing the emission characteristics of HCL to improve line ratios for spectroscopic calibration

Philip Bolte
Institut für Astro- und Geophysik Göttingen (IAG)

Hollow cathode lamps (HCLs) emit a combination of wide gas and narrow metal lines characteristic for the material of the cathode used. A vast variety of commercially available cathode material and carrier gas combinations enables the wide coverage of wavelengths with narrow metal lines. Therefore, HCLs have been used for decades as a cost effective calibration light source in high precision radial velocity instruments like CARMENES and HARPS. However, the small line ratio of metal to gas lines limits the number of sharp metal lines applicable in calibration. The glow discharge effect in HCL has been thoroughly researched as a plasma source for thin film deposition as well as the distribution of metal atoms within the lamps. However, the geometries and varying line ratios of different glow areas of HCL are not well known. As part of an ongoing masters project, we look into the emission geometries and transmitted light intensities of different glow regimes along the lamps optical axis by the means of raytracing, as well as potential alternative strategies of injecting light from HCLs into spectrographs for calibration. This poster will present the preliminary results of the modelling process of the hollow cathode lamp, the resulting predicted intensities per polarization and a comparison with raytracing efforts on features observed in the lab.