Exp__04_Nuc_E_450_Sp11

# Exp__04_Nuc_E_450_Sp11 - 4-1 RADIATION COUNTING...

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Unformatted text preview: 4-1 RADIATION COUNTING STATISTICS (Experiment 4) OBJECTIVETo observe the variations in counting rate caused by random nuclear decay and to become familiar with some of the statistical tools used to evaluate the accuracy and precision of nuclear measurements. To introduce students to the use of computer controlled data collection and analysis. INTRODUCTIONIn this experiment we will study the types of radiation counting corrections required to evaluate various errors introduced into the radiation counting procedure. There are systematic errors, in which there is a constant difference between a measured value and the true value. Such errors are sometimes called determinate errors, since the magnitude of the error can be determined and a correction factor applied. The determination and use of the resolving time correction factor, described in Experiments 2 and 3, are good examples of corrections for a systematic error. Experiment 5 considers other types of systematic counting errors and the determination of their correction factors. This type of error biases a measurement. A second type of error is called a random error. Random errors result from fluctuating conditions. This type of error is sometimes called indeterminate, because for any given measurements one cannot know the magnitude of the deviation of the measured value from the true value. Instead, one estimates the uncertainty in the measurement expressed in such terms as standard deviation, average deviation, or probable error. This type of error decreases the precision of a measurement. Both types of errors affect the accuracy of a measurement. You will use a Microsoft Excel program that does the statistical analysis and plots the histogram of the sample. READING ASSIGNMENTPrior to conducting this experiment, read all of Chapter 3 of Knoll. 4-2 EQUIPMENTThe GM counting instrumentation and radioactive sources used in this experiment are the same as those used in Experiment 2. (See Figure 1) Pulse InverterSCAOscilloscopeIOIOShelfBoxGM TubeHigh VoltageOIOITimer & Counter AMP IO Figure 1 Block Diagram for Counting Statistics SOFTWAREMicrosoft Excel for Windows DEFINITIONS OF TERMSOur first task is to define some words and symbols needed in the presentation and discussion below. The appendices contain a list of key equations used to work up the data. These terms are listed on the following page. 4-3 Term Definitiontrial – one of N measurements (counting observations). sample – the collection of N trials, a subset of the population. source – a collection of radioactive atoms (mounted on a support) used in the experiment to produce radiation counts.. t – counting time. "t" is usually kept constant for a sample of measurements....
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