ABSTRACT: Lessons from a Non-Injury Stray Beam Exposure during Harmonic System Commissioning
On April 16, 2025, a laser supervisor at SLAC National Accelerator Laboratory's Linac Coherent Light Source (LCLS) user facility experienced an exposure to stray 515 nm light while aligning an assembly for generating the 4th harmonic of a 1030 nm Class 4 laser beam. While the exposure was determined to be well below Class 1 limits with no injury, the incident revealed multiple systemic issues of potential interest to laser safety professionals.
This presentation examines how design evolution, schedule pressures, and incomplete Transition-To-Operations (TTO) processes converged to create conditions for exposure. Key technical factors included: removal of motorization from the harmonic assembly without reassessing beam containment requirements; missing engineered controls (periscope cover beam blocks); and ergonomic challenges requiring workers to climb onto laser tables for alignment access. Human performance aspects included deviations from SLAC’s Core Laser Safety Practices and gaps in understanding laser exposure symptoms.
The Judgements of Need (JONs) in the line-led causal analysis report focused on: (1) cultivating deeper safety culture through internalizing SLAC’s Core Laser Safety Practices, (2) empowering workers to request help in challenging conditions, (3) protecting commissioning time to prevent safety compromises, and (4) strengthening configuration control when designs evolve.
This case study offers practical insights for LSOs managing complex experimental systems, implementing TTO protocols, and balancing scientific urgency with thorough safety verification.
This presentation examines how design evolution, schedule pressures, and incomplete Transition-To-Operations (TTO) processes converged to create conditions for exposure. Key technical factors included: removal of motorization from the harmonic assembly without reassessing beam containment requirements; missing engineered controls (periscope cover beam blocks); and ergonomic challenges requiring workers to climb onto laser tables for alignment access. Human performance aspects included deviations from SLAC’s Core Laser Safety Practices and gaps in understanding laser exposure symptoms.
The Judgements of Need (JONs) in the line-led causal analysis report focused on: (1) cultivating deeper safety culture through internalizing SLAC’s Core Laser Safety Practices, (2) empowering workers to request help in challenging conditions, (3) protecting commissioning time to prevent safety compromises, and (4) strengthening configuration control when designs evolve.
This case study offers practical insights for LSOs managing complex experimental systems, implementing TTO protocols, and balancing scientific urgency with thorough safety verification.
BIO: Eric Cunningham
Eric Cunningham is a lead scientist in the Laser Science department of the Science, Research, and Development division at the Linac Coherent Light Source (LCLS), a directorate of SLAC National Accelerator Laboratory in Menlo Park, CA. Eric first joined SLAC in 2016 after completing his PhD in Optics at CREOL, the College of Optics & Photonics at the University of Central Florida. Since that time, he has fulfilled multiple roles within the organization including Laser Scientist and System Laser Safety Officer at the Matter in Extreme Conditions instrument, as well as the Directorate Laser Lead for laser safety and Lead for Laser Operations at LCLS. Eric also serves as a member of the SLAC Laser Safety Committee.
