Advancing Hollow Cathode Lamp Calibrations for Next-Generation Spectrographs

Wavelength calibration for multi-object spectrographs commonly relies on hollow-cathode lamps, which provide many well-characterised lines in the visible and near-infrared. However, these lamps are dim and struggle to illuminate large focal planes in the VLT and ELT era. Problems have also arisen in the procurement of Thorium cathode lamps, a standard in the field, due to contamination issues and manufacturers withdrawing them from the market. We present a technology development project focusing on the design and manufacture of hollow cathode lamps tailored for astronomical purposes to enhance their output flux, stability, and line ratios. In our custom-built units we are optimizing the cathode design, material, and current, allowing the mosaicking of configurable cathodes. The choice of filler gases and the pressure of the system is similarly being optimized. We finally present work on characterisation of Cerium cathodes, identified as a potential alternative to Thorium and Uranium due to favourable nuclear properties. This work represents a step towards robust, scalable calibration solutions for future spectroscopic facilities.