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Counting rate statistics

Such significant increase of accuracy may be explained on the base of analysis of the numerical values of the theoretical correction coefficients and calculated for 1, , and for analytical pai ameter lQ.j,yipj.j,jj- Changing from lines intensities for the ratios of analytical element line intensity to the intensity of the line most effecting the result of analytical element (chromium in this case) measurement enables the decreases of the error 5 or even 10 times practically to the level of statistics of the count rate. In case of chromium the influencing elements will be titanium, tungsten or molybdenum. [Pg.442]

Because X-ray counting rates are relatively low, it typically requires 100 seconds or more to accumulate adequate counting statistics for a quantitative analysis. As a result, the usual strategy in applying electron probe microanalysis is to make quantitative measurements at a limited collection of points. Specific analysis locations are selected with the aid of a rapid imaging technique, such as an SEM image prepared with backscattered electrons, which are sensitive to compositional variations, or with the associated optical microscope. [Pg.187]

Thus the counting rate should be sufficiently high to ensure a precision sufficient for isotope effect measurements a target precision of 0.1% is obtained for total counts of 106. Radiolabeled material used for isotope effect measurements usually has counting rates of 15,000 counts per minute (cpm). To achieve 0.1% precision such samples must be counted for 8 h or more. More often counting time is limited to several cycles of about 10 min each with a commensurate increase in the statistical error. [Pg.234]

The central assumption of ion counting is that ions arrive at the detector at random, i.e., that the probability of arrival of an ion is the same for any time interval of a same length. The number , of ions i arriving at any collection device during the time interval dt is therefore subject to Poisson statistics , is proportional to 5t, the average count rate is n/8t, and its... [Pg.132]

Assuming that/A is 0.01, and we would like to determine this value with the atom-probe to an accuracy of 5% of fA, then the number of ions collected should be at least 39 600. This is already near an impractically large number in the atom-probe analysis. It quickly becomes impractical to determine accurately the concentration of a minority species with the atom-probe at a low counting rate if its concentration is smaller than —0.5%. The following statistical analysis points to a method with which this difficulty can be overcome. [Pg.155]

Up to now we have carefully restricted our discussion of nuclear statistics to cases where 1-min counts were taken. If the number of counts recorded in 1 min was x, then the counting rate has been quoted as x + (.v)1/2 cpm. Suppose, however, that we recorded 160 counts in 5 min. What would be the standard deviation of the average counting rate (in cpm) The best estimate of the mean number of counts in the 5-min period would by 160 + (160)1,/2 that is, 160 + 13 counts. The average rate would be 160/5 + 13/5 = 32 + 3 cpm. In general, therefore, the rate R is given as ... [Pg.573]

Since for a given measuring time nlrut It, and acc /e2i> where /el is the electron beam current, it can be seen that when acc /Jtrue the statistical error is optimal and independent of ItV Second, the coincidence rate is restricted by the maximum allowable singles count rates in either channel (—106— 107 cps, as discussed earlier). [Pg.37]

The disadvantages of this reaction place some real constraints on its use 1) The (t,p) cross section is only about 5 percent of the total cross section 2) The dominant reaction, usually (t,2n), produces abundant prompt Y rays 3) Reactions such as (t,n) and (t,d) [as well as (t,p)] often result in short-lived beta decaying products 4) The usual in-beam techniques such as angular distributions are complicated by the necessity to use the outgoing proton to identify the reaction As a result of the first three disadvantages, much of the Y ay and electron count rates are not from the (t,p) reaction and thus experiments of reasonable duration have limited statistics ... [Pg.194]

It should be mentioned that in general the contributions to the cumulative uncertainty originating in the number of counts in the tails are smaller than the contributions of the statistical uncertainty and the uncertainties of the boundary positions and that the latter become more important at high count rates. [Pg.232]

We have carried out the first measurement of the 2S /2 — 2P3/2 interval in 7V6+. Our result is in good agreement with the theory, but the precision of 0.07 cm-1, or. 17% of the Lamb Shift interval, is not sufficient to provide a useful test. However the count rates and signal-to-background ratio achieved, 100 kHz/particle-nA and 25 respectively, are consistent with obtaining a statistical precision of 0.001 cm-1. The beam current and detector solid angle can be increased in future experiments if necessary. [Pg.697]

One detector is held stationary and the other is rotated about the sample axis the coincidence count rate is recorded by the scaler at each angle chosen. A typical time required to obtain an angular correlation curve with good statistics and with an angular resolution of 10 mr is lOOh. [Pg.57]

The pulse channel allows the count rate to be measured in the specified area of SRP storage with the statistical accuracy up to 1%. In order to take into account the electronie equipment drift and variations in the detector operation conditions it is necessary to have the external device for calibration and control of pulse channel stability. [Pg.215]


See other pages where Counting rate statistics is mentioned: [Pg.2062]    [Pg.135]    [Pg.38]    [Pg.43]    [Pg.48]    [Pg.49]    [Pg.289]    [Pg.86]    [Pg.210]    [Pg.46]    [Pg.172]    [Pg.6]    [Pg.133]    [Pg.155]    [Pg.105]    [Pg.191]    [Pg.109]    [Pg.184]    [Pg.35]    [Pg.37]    [Pg.37]    [Pg.32]    [Pg.184]    [Pg.86]    [Pg.72]    [Pg.175]    [Pg.235]    [Pg.39]    [Pg.224]    [Pg.225]    [Pg.472]    [Pg.481]    [Pg.144]    [Pg.175]    [Pg.187]    [Pg.504]    [Pg.48]    [Pg.384]    [Pg.669]   


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