External-beam development and PFAS measurements with the UML Van de Graaff accelerator

Charged-particle beams are useful in various non-destructive analysis techniques, such as Particle-Induced Gamma-ray Emission (PIGE), Particle-Induced X-ray Emission (PIXE), and Rutherford Backscattering Spectrometry (RBS). An extension to a beamline at the UMass Lowell Van de Graaff Accelerator Facility is being developed to enable analysis of more numerous as well as larger samples in air. The current design utilizes a Kapton window supported by a steel mesh. To test this new capability, samples were analyzed for their 19F content. Various per- and polyfluoroalkyl substances (PFAS) —a potential health and environmental concern— were placed in an external 3.5-MeV proton beam to quantify their relative 19F content [1]. Characteristic 19F gamma-rays at 109.9 and 197.1 keV were detected using a high-efficiency HPGe detector and the relative differences in 19F compared. An overview of the setup, initial test results, and future development of the ion-analysis beamline will be presented.

[1] L. Schultes, G.D Peaslee et al., Environ. Sci. Technol. Lett. 2019, 6, 2, 73–78