Practical laser induced breakdown spectroscopy unit

Abstract

An apparatus for performing laser-induced breakdown spectroscopy comprises a handheld unit with a pump laser and a controller. A combination of a solid laser medium and a Q-switch receive a laser beam from said pump laser. Focusing optics focus laser pulses from said combination to a focal spot at a sample. Light collection optics collect light from plasma induced of sample material by focused laser pulses. A spectrometer receives collected light and produces information describing its spectral distribution. A power source delivers electric power to other parts of the apparatus. The pump laser, combination, focusing optics, light collection optics, spectrometer and power source are parts of said handheld unit.

Description

TECHNICAL FIELD[0001]The invention concerns in general the technology of laser-induced breakdown spectroscopy. In particular the invention concerns the structure of an apparatus built for laser-induced breakdown spectroscopy measurements.BACKGROUND OF THE INVENTION[0002]For various applications, methods are needed for determining the material constitution of a sample. One of known methods is laser-induced breakdown spectroscopy (LIBS), which involves focusing a laser beam onto a surface of the sample with a high enough power density to transform a small part of the sample material into a state of plasma. Optical emissions from the plasma plume are collected with light collection optics, and the spectral distribution (i.e. intensity as a function of wavelength) of the collected optical emissions is analysed in a spectrometer that produces information in electronic form describing the spectral distribution. Since atomic and molecular constituents of sample materials have characteristi...

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Benefits of technology

[0017]Passively Q-switched pulse lasers have been considered to only be suitable to benchtop analysers, because their energy consumption has been relatively high. However, in the course of the development work leading to the present invention it was found that certain means may be applied to significantly reduce the energy consumption. Using Nd:YLF (Neodymium (3+)-doped Yttrium Lithium Fluoride) as the active (gain) medium leads to better efficiency, higher pulse energy and shorter pulse duration, which means that in order to create the same amount of plasma, the electric power needed for the pump laser can be smaller than with e.g. a corresponding Nd:YAG (Neodymium (3+)-doped Yttrium Aluminum Garnet) gain medium. Wavelength locking can be used to stabilize the output wavelength of the laser diode, which substantially eliminates temperature-dependent wavelength drift. This way the power-intensive active temperature control of the pump laser can be completely avoided or at least limited to only compensating for the largest deviations from a nominal operating temperature.

Problems solved by technology

A drawback of the known LIBS measurement devices is certain clumsiness and limited applicability to field use.

Passively Q-switched pulse lasers have been considered to only be suitable to benchtop analysers, because their energy consumption has been relatively high.

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