Recent Developments
Recent interest in LIBS has focused on the miniaturization of the components and the development of compact, low power, portable systems. This direction has been pushed along by interest from groups such as NASA, ESA as well as the military. The Mars Science Laboratory mission brought ChemCam, a LIBS instrument, onto Mars in 2012.
Recent developments in LIBS have seen the introduction of double-pulsed laser systems. For double-pulse LIBS one distinguishes between orthogonal and perpendicular configuration. In perpendicular configuration the laser is fired twice on the same spot on the specimen with a pulse separation in the order of one to a couple of tens of microseconds. Depending on pulse separation, the second pulse is more or less absorbed by the plasma plume caused by the previous pulse, resulting in a reheating of the laser plasma leading to signal enhancement. In orthogonal configuration a laser pulse is fired parallel to the sample surface either before or after the perpendicular pulse hits the specimen. The laser plasma ignited in the surrounding medium above the surface by a first pulse causes (by its shock wave) an area of reduced pressure above the specimen into which the actual plasma from the sample can expand. This has similar positive effects on sensitivity like LIBS performed at reduced pressures. If the orthogonal laser pulse is delayed with respect to the perpendicular one, the effects are similar as in the perpendicular configuration. Timing electronics such as digital delay generators can precisely control the timing of both pulses.
Both double-pulse LIBS as well as LIBS at reduced pressures are aimed at increasing the sensitivity of LIBS and the reduction of errors caused by the differential volatility of elements (e.g. Hydrogen as an impurity in solids). It also significantly reduces the matrix effects. Double-pulsed systems are also proving useful in conducting analysis in liquids, as the initial laser pulse forms a cavity bubble in which the second pulse acts on the evaporated material.
LIBS is one of several analytical techniques that can be deployed in the field as opposed to pure laboratory techniques e.g. spark OES. Recent research on LIBS is focusing on compact and (man-)portable systems. Industrial applications of LIBS are e.g. the detection of material mix-ups, analysis of inclusions in steel, analysis of slags in secondary metallurgy and high-speed identification of scrap pieces for material specific recycling tasks.
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