A low-cost, true integrating averager circuit has been designed for applications where low-level signal voltages must be recovered from noisy waveforms. The design separates the integrating, averaging and amplifying stages of the unit, so that correct functionality of each is guaranteed. High-quality commercially available components are combined with an optimized circuit layout, enabling the complete unit to be fabricated on one standard sized, single-sided printed circuit board, complete with on-board power supply regulation. The circuit can be incorporated into a standard housing, with a total cost of approximately ten per cent of that of a commercial unit, and the modular design means that custom modifications are easy to make. The performance of the unit is quantified in terms of the dynamic parameters of interest, and an example is given of the application to routine spectroscopic measurements. The main performance limitations are discussed in the context of the design considerations, and suggestions are made as to future improvement possibilities.
In this paper several laser-based spectroscopic methods capable of detecting low concentrations of a particular element are described, with particular emphasis on the contrasting techniques of Laser-Induced Breakdown Spectroscopy (LIBS), and Resonance Ionisation Mass Spectroscopy (RIMS). Simple mathematical treatments, based on thermodynamic considerations and rate equation models, are given for both systems, allowing semiquantitative analysis from the magnitudes of observed signals. Experimental results are presented for both methods. For LIBS these include the determination of the concentration of alloy constituents, the detection of surface contaminants and the use of measured line intensities to calculate electron temperatures in laserproduced plasmas. For RIMS, detection of the geologically important element rhenium (Re) was accomplished in the gas phase at a level of 4 x 10 8 atoms/cm 3 , and the relative proportions of the stable isotopes 185 Re and 187 Re were measured with the use of a quadrupole mass filter. In addition, an optogalvanic system is described, which was used to calibrate the wavelength of the RIMS resonance to an accuracy of 0.013 nm.
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