Zero count rate

Zero count rate The number of counts recorded in unit time by an optical particle counter when a particle-free gas is passed through the measuring chamber. 

With high dispersion and poor flow paths, the response to a tracer impulse usually showed considerable tailing. It often approaches zero count rate so slowly that it is difficult to extrapolate to the end of the curve. 

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. 

It can be shown that the upper limit on the rate (when zero counts are observed), A0,... 

Flo. 34. Mbssbauer spectrum of tetramethyl tin before and after chemisorption on y-AI,03. N is the count rate of the y quanta at the given value of V N0 is the count rate of the y quanta when the absorption agent is stationary, (a) Tetramethyl tin, (b) tetramethyl tin adsorbed on y-AI203. Zero velocity is with respect to Sn02- Figure according to Karasev et al. (230). 

Low Count Rates in Blanks. Radioactive contamination in a blank should be zero, or constant and extremely small. A procedure blank is a deionized water sample that is processed through the complete analysis. Carrier is added, every step is performed to the end of the analysis, and the final form is counted. Blanks are processed as part of each sample batch to check the quality of the analysis with regard to laboratory contamination for this batch. 

The blank shows whether the reagents, glassware, and work environment contribute any radioactivity to samples. A blank will have a zero net count rate - that is, the measured or gross count rate minus the detector background count rate - if no radioactivity is observed. If the net count rate is above zero, it should be low compared to the net count rate of the analyte. Efforts should be made to find and reduce the source of contamination. 

The net count rate at a given mass, Rm, is related to the self-absorption factor at that mass, fm, in terms of the activity, A, gamma-ray decay fraction, d, and counting efficiency at zero self-absorption, e0, by Equation 3.2 ... 

Calculate the ratio of the net count rate to the disintegration rate of K gamma rays in the sample, based on the half life, gamma-ray decay fraction, ratio of 40K to potassium mass, and K/KC1 ratio of 39.1/74.6. Calculate the self-absorption factor with Eq. 3.1. Calculate the counting efficiency at zero self-absorption with Eq. 3.2 and record in Data Table 3.3. 

Adjust the upper discriminator of the second channel (Channel B) to its maximum value and its lower discriminator to a value sufficiently above zero so that only about 25 to 50% of the count rate observed in Channel A for an unquenched standard appears in Channel B. 

The regression line in Figure 5b also provides an indication of the initial activity of thoron in the water. The y-intercept (6.61 on a Ln scale) represents the count rate when the inverse of the flow rate is at zero (the flow rate is at infinity), thus the instantaneous count rate would be exp(6.61) or 742 cpm. Correcting for the solubility of radon in water (a = 0.316) at the in situ water temperature (13°C) and using a rated RAD-7 efficiency for thoron of 5.68 cpm/(Bq/L) [0.210 cpm/(pCi/L)], this translates to a thoron activity of 41.3 Bq/L in the water. 

Figure 9. The observed variation of the coincidence count rates as functions of the phase of entangled photons 0 at zero delay for the photon-number entangled photons. Solid triangles represent the two-fold coincidences with Da Da and show the phase of input photons. Solid diamonds represent the four-fold coincidences with Di D2 Da Da which show the phase of the output photons demonstrating a successful NS operation. Error bars are based on the usual Poisson fluctuation in the number of counts on the uncorrected data (error bars of two-fold coincidences are too small to display). The phase of four-fold coincidence is shifted (1.05 0.06) tv against two-fold coincidence in agreement with the expected tv phase shift.

The measurement accuracy was experimentally determined by positioning the tracer in known locations inside the bed (Moslemian, 1987). The apparent tracer positions were calculated from the linear regression formulation Eq. 9.13, based on the measured detector count rates and the predetermined calibrations. Sufficient data were taken at each location to allow for statistical determination of mean and standard deviations of the tracer position and velocity. In general, the axial errors were often greater than the radial errors because of the longer axial distance of the bed that the detectors had to monitor. For an empty bed, the mean axial error in determining the tracer position was 4.7 mm and the mean radial error was 3.9 mm The corresponding standard deviations were 1.6 mm in the axial direction and 1.2 mm in the radial direction. These deviations were due to the statistical nature of the radiation detection and are the minimum deviations obtainable for the tracer position. The measured mean axial and radial velocities were approximately zero (<1 cm/s) at all locations inside the bed. However, the standard deviations of the velocities were 7.6 cm/s in the... 

In the experiment, the sampling of the detectors was initiated slightly sooner than the release of the radioactive particles to ensure the recording of the events near zero time. As the particles were released, the outputs of the detectors positioned above the free surface (Levels 1 and 2 shown in Fig. 9.5) reached their maximum within a small fraction of second because of the passage of the falling tracer particles. The steady-state averaged count rate did not overlap for the four levels because of the variation in density distribution seen by detectors at different levels. From the curves in Fig. 9.21, three types of information could be obtained. The asymptotic steady-state values of the count rates were measures of the mean density distributions of the radioactive particles in the bed. The time required to reach these asymptotic values was an indication of the mixing rate of the bed particles. The shapes of the curves yielded information on the manner in... 

Calculate the counting rate for the case shown in the figure below. The source has the shape of a ring and emits 10 part./s isotopically. The background is zero. The detector efficiency is 80 percent, and F = 1. 

According to Eq. 12.22, if one uses an X-ray detector set at an angle 0 (Fig. 12.47) to detect diffracted photons of wavelength A, the counting rate is zero at any angle different from 0. In practice, this does not happen. As the angle 0... 

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