Surface cleaning and chemical process analysis of high quantum efficiency magnesium photocathode

Magnesium (Mg) has been demonstrated to be a safe, stable, and reliable photocathode for both normal-conducting and superconducting RF guns. Pure magnesium, with its low work function of 3.6 eV, exhibits significant quantum efficiency (QE) improvement — by up to two orders of magnitude — following appropriate surface cleaning procedures. This study investigates the chemical processes occurring on the material's surface in its as-received state and after thermal and plasma cleaning. These findings provide critical insights into the mechanisms underlying QE enhancement on this metallic photocathode.