Counting efficiency

Efficiency, counting The proportion of particles in a volume or mass flow that are counted as they pass through the sensing element of an optical particle counter. 

Count the alpha particles in each tracer sample for a time period sufficient to accumulate at least 1000 counts. An initial estimate of the sample counting period is based on the activity of the tracer and the known counting efficiency. Count all disks for the same period of time. The samples may be counted more than once. Count the spectral analysis background for approximately 200,000 s and the proportional-counter alpha-particle background at least 30,000 s. Record data in Data Table 6.2. 

The detection system is calibrated in terms of energy per channel in keV or MeV. It also is calibrated in terms of counting efficiency - counts per gamma ray - as a function of energy. 

Transfer an aliquot of the sample into a container for which the detector has been calibrated in terms of gamma-ray counting efficiency (count per gamma-ray emission), as in Experiment 2B. After transferring the solution... 

G-M tubes is longer than for photomultiplier tubes therefore, samples of high radioactivity are not efficiently counted by the G-M tube. In addition, sample preparation is more tedious and time-consuming for G-M counting. 

Radio- detection Background (CPM) Counting efficiency (%) Counting time (min) Limit of detection" (DPM) Limit of quantification (DPM)... 

Detection efficiency (counts per reactor fission) determines the measurement time required to attain the desired statistical precision and therefore limits the distances between detectors. Thus, detection efficiency determines the lengths of fission chains that provide correlatable events for calculation of cross power spectral densities. Measurements have been satisfactorily performed by this method, with detection efficiencies as low as 10 count per reactor fission. For this larg BWR, Ae ralculated detection efficiency is greater than 10 for a 5-g U fission detector within 70 cm of the c6re center. More efficient detectors such as Li glass sc tillators (factor of —100 larger) could be us d for unirradiated fuel, and measurements could be made with these detectors more than 100 cm from the core center. 

Since, In practice, the efficiency frequently varies, it is necesseuy to determine the counting efficiency before one can compare different samples. A radioactive standard of acciirately known activity is essential for the determination of the efficiency counting. The use of radioactive standards is in principle similar to that of standards in colorimetric or spectrophotometric assays. There are two types of standards (i) internal standard (this is usually a p-emitter of accurately known activity which, when dissolved in unquenched scintillation mixture, provides a reference standard), and (ii) external standard (ay-emitter incorporated in most instruments). 

Such a course has obvious advantages in that it teaches communication, leadership, and teamwork. But it also has two negative aspects time and evaluation. There is no doubt that such a course requires much more time from everyone — the professors, the tutors, and the students. In an age when efficiency counts, it is difficult to convince all the actors that the extra effort is worth it, or even to find the time required to teach and learn in this way. Professors are forced by the system to be very engaged in research as was seen in the previous section. Since research publication is the motor for promotion, etc., the professors prefer to spend less time in the classroom. The students have to work for other courses, which probably also... 

Counter efficiency = (counts per minute from the sample/disintegration per minute from radioisotope) x 100%. 

Solid lines are fitted for all data to the exact VTMR equation including all delayed neutron terms, and for all variables related with VTMRs -counting efficiency (counts/fission), reactivity, Pu-239 fission portion (assuming fissions are occured only by U-235 and Pu-239), neutron generation time and effective delayed neutron fraction. 

Quantification is nevertheless possible with this type of analyzer, as long as one works on weak dynamic ranges (see Chapter 7). Most users of TOF spectrometers in GC-MS coupling speak of semi-quantification. This infers that the spectrometer allows the estimation of analyte quantities rather than a precise dosage. This issue is contested based on certain applications in which TOF analyzers quantify as accurately as quadrupoles. Considering the economic stakes accompanying the efficient counting of ions, it is very probable that detection solutions will soon address this problem. 

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