Lab4 handout - School of Nuclear Engineering Purdue...

Info iconThis preview shows pages 1–3. Sign up to view the full content.

View Full Document Right Arrow Icon
NUCL 205 Exp 4: Nuclear Statistics 1/7 2/7/2010 School of Nuclear Engineering Purdue University West Lafayette, IN 47907-1290 NUCL 205 Experiment 4: Nuclear Statistics and Error Propagation 1 Objectives The objectives of this experiment are: a. To introduce the student to the statistical nature of all experimental measurements, especially nuclear counting experiments; b. To demonstrate the methods used to determine the statistical spread expected in data; c. To show how statistics can be used to check for the proper design and operation of equipment and methods used in an experiment; and d. To introduce the student to methods for determining how errors propagate through calculations. 2 Nuclear Statistics Nuclear radiation measurement involves phenomena which are statistical in nature, for example the number of nuclei decaying per unit time or the number of counts recorded per unit time by a detector. An understanding of these statistical effects is necessary for a meaningful interpretation of the data. 2.1 Mean Values The purpose of any experimental measurement is to determine the "true" value of one or more physical quantities, such as the rate of decay of a sample of radioactive material. Unfortunately, every experimental measurement has some experimental error or uncertainty associated with the measurement so that the true value, m, of the phenomenon can only be approximated by the measured value. If the measurement is repeated N times, then the true value is approximated by the average value of measured values, that is = N i i i x N x m 1 (1) where N is the number of independent measurements and x i is the value of the i th measurement. As the number of measurements increases, the statistical uncertainty of the average value decreases and the average value of the experimental measurements becomes a better approximation of the true value except for "systematic" experimental errors which may be present in any experiment. 2.2 Standard Deviation The spread or variation of the experimental measurements, x i about the true value, m , is given by the "true standard deviation," s . The physical meaning of the standard deviation is to define a band of values between (m+s) and (m-s) containing 68% of all of the measurements, x i . Thus, it is expected that
Background image of page 1

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
NUCL 205 Exp 4: Nuclear Statistics 2/7 2/7/2010 approximately one out of three experimental values will fall outside of this band. A larger band, (m ± 2s), will contain approximately 95% of the measurements. However, the true standard deviation for an experiment can never be determined unless an infinite number of measurements are made; but the true value of the standard deviation can be approximated if the experiment is repeated a number of times. The approximate or experimental value of the standard deviation,
Background image of page 2
Image of page 3
This is the end of the preview. Sign up to access the rest of the document.

This note was uploaded on 03/11/2010 for the course MCMP 341 taught by Professor No during the Spring '10 term at Purdue University-West Lafayette.

Page1 / 7

Lab4 handout - School of Nuclear Engineering Purdue...

This preview shows document pages 1 - 3. Sign up to view the full document.

View Full Document Right Arrow Icon
Ask a homework question - tutors are online