Highlights from the first beam commissioning stage at ESS for its ion source and low energy beam transport

The proton linac of the European Spallation Source, under construction in Lund, Sweden, had beam commissioning of its ion source (IS) and the following low energy beam transport (LEBT) at their final locations from September 2018 to July 2019. This was first of several beam commissioning stages for the linac of ESS, towards the start of the user program in 2023. This paper presents highlights of characterizations of the IS and LEBT from the aforementioned beam commissioning period, including behavioral change of the IS against its parameters, error source identifications of the beam trajectory in the LEBT, and preliminary characterization of the LEBT output beam against solenoid strengths in LEBT.