Count rate maximum useful

There is some controversy as to whether adsorption occurs in emulsion counting of Na2 C03 (Wigfield, 1976). Our results agree with those of that author in that we have not seen effects that could be attributed to adsorption. Furthermore we have never had ciny problems with low count rates when using counting mixtures of the recommended ccanpositions even with the highest specific activity Na2 C0j we used (59.5 mCi/mmol). The maximum specific activity theoretically possible for Na2 C03 at 100% isotopic abundance is 64 mCi/mmol (Wilson, 1966). 

The cause of this difficulty therefore resides within the counter itself. The difficulty is described by saying that the Geiger counter has a dead time, by which is meant the time interval after a pulse during which the counter cannot respond to a later pulse. This interval, which is usually well below 0.5 millisecond, limits the useful maximum counting rate of the detector. The cause of the dead time is the slowness with which the positive-ion space charge (2.5) leaves the central wire under the influence of the electric field. This reduction in observed counting rate is known as the coincidence loss. 

A novel variation of the above technique can be used in some cases. By choosing an appropriate source so that the maximum resonance in the paramagnetic state occurs at or near zero relative velocity, one eliminates the need of a Mossbauer spectrometer completely, and the transition temperature can be determined by measuring the count rate transmitted through a stationary absorber and emitted by a stationary source as a function of temperature—see, for example. Refs. 18, 20. 

Pacific Scientific Met One 210 Liquid Particle Counter is used to measure particles in clean fluids used in electronic, pharmaceutical and other manufacturing processes. It classifies particles in six size ranges in the 0.4 to 25 pm size range using laser diode based forward light scattering. Maximum count rate is 8000 particles per minute at a fluid flow rate of 100 ml min. ... 

Line positions cannot be measured with sufficient precision on a chart recording made with a ratemeter. Instead, a scaler is used to determine the count rate at several positions on the line profile, and from these data the position of the line center is calculated. This procedure is particularly necessary when the lines are broad, as they are from hardened steel the line width at half-maximum intensity is then 5°-10° 29. If the line is 8° wide and the stress constant AT, is 86.3 ksi/ deg A20, as given above, a stress of 50 ksi will cause the line to shift by only 7 percent of its width when the specimen is turned through 45°. Measurement of such a small shift requires that the line center be accurately located at each angle ij/. 

Also, this method does not allow the recognition of shoulders, but of real local maxima only. If, especially for large step widths, a maximum is placed just between two grid points, the measured counting rates at both points will be smaller by several percent than the (unmeasured) maximum itself Using the above formula for A permits a rather accurate estimation of the unknown peak height. 

This system is relatively simple and is used as a mobile detector. However, it has a high dead time (= 200 p.S), hence a low maximum counting rate. This type of device cannot be used for quantitative intensity measurements. 

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