Laser-Induced Breakdown Spectroscopy Optimization of Tropical Hardwoods
Date
2024-05
Authors
Journal Title
Journal ISSN
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Publisher
University of Delaware
Abstract
Handheld laser-induced breakdown spectroscopy (LIBS) is being implemented
to conveniently and effectively distinguish between various tropical hardwoods, a step
toward combating illegal timber trade at ports of entry. A key parameter for LIBS
analysis is the delay time between the laser pulse and spectral collection. Short delays
yield more information-rich spectra with high noise while longer delays sacrifice
information for a more stable spectrum. Currently, LIBS handheld spectrometers are
designed for alloy and mineral classification, so the acquisition settings for the non traditional - tropical hardwood – analysis should be re-optimized.
A subset of 23 species of hardwood were analyzed using various delay inputs,
a collection parameter that dictates when sample plasma is analyzed by the
instrument’s detectors. The factory default setting for the LIBS handheld is 650
nanoseconds. Optimizing for these organic samples shows that a delay time between
250 and 370 nanoseconds yields a significant improvement in multivariate analysis of
the collected spectra as evidenced in the increased accuracy of classification models.
This improvement is demonstrated on a set of 280 exotic hardwood exemplars. This is
meaningful for agencies such as the US Forestry Service (USFS) because it advises
that imported hardwoods can be successfully identified in the field by handheld
instrumentation such as LIBS.