Laser safety analysis

Lasers are widely used in the workplace for a variety of purposes ranging from cutting and welding to materials analysis and measurement. The t5q)es of laser used including their output powers vary depending on the application. The current standard for laser safety provides appropriate advice to both the manufacturer and the user of laser products. 

Choosing a suitable Raman spectrometer for on-line process analysis requires different criteria from laboratory analysis. Some key considerations are laser safety, ruggedness, repeatability, long-term and environmental stability, high uptime, calibration ttansferability, ease of operation and maintenance, smart diagnostics for analyser performance, and industry-standard communication. Many processes require the analysis to be performed... 

S.D. Harvey, T.J. Peters and B.W. Wright, Safety considerations for sample analysis using a near-infrared (785 nm) Raman laser source, Appl. Spectrosc., 57, 580-587 (2003). 

All these applications have different instrumental configurations and in many cases the laser can be delivered to the analysis point via fibre optics. This provides an implementation challenge as laser exposure and eye safety are paramount concerns particularly in a manufacturing environment. Although mentioned briefly here Raman PAT applications are likely to be an area of significant growth over the coming years. 

Harvey, S.D. Peters, T.J. 8t Wright, B.W. Safety Considerations for Sample Analysis Using a Near-Infrared (785 nm) Raman Laser Source Appl. Spectrosc. 2003, 57, 580-587. 

Technetium isotopes in the PWR primary coolant show a behavior which is quite different from that of the other fission products treated in this section. Whereas the short-lived Tc is only of minor radiological relevance, its long-lived isomer c (halflife 2.1 HP a) deserves some attention with respect to safety analyses for the final storage of radioactive wastes. Normally, c is not analyzed in the reactor coolant because of its very low activity concentration and of its unfavorable radiation properties (P 0.3 MeV, negligible y transition). For this reason, the Tc mass is frequently determined rather than its radioactivity suitable techniques for this task are neutron activation analysis, inductively-coupled mass spectrometry and laser resonance ionization mass spectrometry (see, for example, the comparative evaluation given by Trautmann, 1993). In each case, very expensive analytical procedures are required therefore, the greatest part of the available information on Tc behavior in reactor primary circuits has been derived from measurements of y-emitting Tc. 

The cone calorimeter can also be used to obtain other data in support of fire safety engineering analysis. For example, the instrument can be used to determine ignition characteristics of a material by measuring the time to ignition at different heat flux levels. A laser smoke photometer is moimted on the duct to determine the smoke production rate. A continuous gas sample can be taken from the exhaust duct and analyzed to determine the concentration of different toxic and corrosive products of combustion in the effluents. Fourier transform infrared spectroscopy is now a common method to measure the concentration of toxic and irritant gases in the exhaust duct of the cone calorimeter. 

Industrial application of SNMS is still in its infancy. As opposed to the many SIMS applications for polymer/additive analysis cfr. Chp. 4.2.1), there appear to be no records (yet) of the use of SNMS or SIMS/SNMS for this purpose despite the desirable features of the (combined) technique. However, scarcity and cost of the equipment (as well as safety aspects for L-SNMS) play a major role in application to routine problems. Also, the SIMS-XPS combination is obviously a serious proven competitor in many instances. Another drawback in many applications is of course the fact that the surface is analysed rather than the bulk. In SNMS most progress can be expected from a combination of laser post-ionisation and sputter depth profiling. 

In a broad sense, spectroscopic methods applied in process analytics comprise widely used techniques like UVA IS, mid-IR, NIR, NMR and XRF, and less frequently used ones, such as Raman spectroscopy, fluorescence, chemiluminescence, acoustic emission and dielectric specfloscopy. Upcoming in-process analysis techniques are 2D-fluorescence, and laser absorption specfloscopy (LAS) with tuneable lasers and ppm level sensitivity. The availability of mini-spectrometers (e.g. UVA IS/NIR) is not highly relevant in plant environments where safety is of primary concern. 

Nevertheless, predictions are a valuable form of analysis that also provide insight into safety, maintenance and warranty costs and other product considerations. US Department of Defence Handbook (M1L-HDBK-217F, dd Dec 1991) can be used for reliability prediction of electronic components (e.g. microcircuits, semi-conductors, lasers, resistors, capacitors, etc.). The purpose of MlL-HDBK-217 is... 

This analysis enables the evaluation of the use of lasers from a safety view. 

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