Update on BELLA Center laser system development towards a compact Thomson photon source*

Thomson scattering of laser pulses from relativistic electron beams can produce bright, narrow energy-spread MeV photon beams, with relevance to many applications including nuclear nonproliferation. Here we present a 5 Hz, 40 fs, 100 TW class laser system at the BELLA Center, dedicated to this light source development. The system consists of two independently tunable and compressible Ti:Sapphire multipass-amplifier arrays (2.8 J and 0.7 J on target, respectively) with the seed-beam split off just after the common CPA stretcher. Additionally, an independently tunable 40-fs probe beam is available in various configurations. We discuss the system layout, commissioning, performance, stability and alignment procedures to enable stable day-to-day operation and multi-beam experiments. Stable electron beams have been established via ionization injection with further source development and Thomson scattering experiments underway.