Laser induced breakdown detection for the assessment of colloid mediated radionuclide migration

摘要: Abstract Colloids play an important role in the transport of pollutants environment. Harmful substances can undergo over large distances if bound to colloids aqueous surrounding. One example is migration Pu(IV) at unexpectedly high rates several miles a Nevada nuclear detonation test site. For long term safety assessments radioactive waste repositories, it hence crucial know about amount, size distribution and chemical composition ground water. Standard methods (e.g. light scattering) be applied for concentrations sizes particles. smaller than 50 nm, however, are detected with very low efficiency. Laser induced breakdown detection (LIBD) fill this gap. A new instrumentation presented, which as compared previous instruments, opens up much wider operational dynamic range, now covering three orders magnitude (5–1000 nm) seven particle concentration (1 ppt – ppm). The technique based on plasma formation colloidal particles inside focus pulsed laser. plume by three-dimensional optical observations means its shock wave piezo-detector. mathematical modelling, detailed knowledge photon fluence focal region indispensable. first time true Gaussian TEM00 mode has been achieved LIBD apparatus great care taken guarantee long-term stability parameters. Automated control laser pulse energy beam shape introduced allow routine reproducible measurement. combines acoustic monitoring two CCD cameras placed perpendicular each other order gain additional information. events systematically characterized respect number density aquatic function energy. Whereas threshold (irradiance) only depends colloid size, probability higher energies direct colloids. correlation facts allows speciation distribution.