JLab, Newport News, Virginia, USA
Foreign particles residing on the field carrying surface of accelerator cavities are a known mechanism for field emission. Developing the methods and tools for collecting and characterizing particles found in an accelerator enables process development towards field emission free SRF cavities. Methods are presented for sampling assemblies, components, processes, and environmental conditions utilizing forensic techniques with specialized tooling. Sampling activities to date have produced an inventory of over 850 GSR spindles. Traditional SEM + EDS analysis of this volume of spindles is challenged by labor investment, spindle sampling methods, and the subsequent data pipeline which ultimately results in a statically inadequate dataset for any particulate distribution characterization. A complete systematic analysis of the spindles is enabled by third party software controlling SEM automation for EDS data acquisition. Details of spindle creation, collection equipment, component sampling, automating particle assessment, and data analysis used to characterize samples from beamline elements in CEBAF are presented.
JLab, Newport News, Virginia, USA
While the techniques used to provide "UHV clean" and "particle-free" beamline components, including SRF cavities, continue to evolve, "real-world" operating machines must deal with actual accumulated and latent contamination issues that produce non-trivial cryogenic heatload, radiation, activation, and degradation via field emission. We have developed a standardized and automated particulate contamination assay method for use in characterizing particulates found on beamline components and in cleanroom assembly environments. We present results from using this system to analyze samples taken from reworked cryomodules from CEBAF. Particle sizes are much larger than anticipated. Utility for feedback on sources to enable improved source reduction is explored.
