University of Heidelberg

Questions on F17: Experiments on neutron physics

Before doing these experiments you must be able to answer the questions given in this catalog in order to make sure you have an understanding of the underlying physics. These include questions on
  • interactions of neutrons with matter,
  • interactions of gamma radiation with matter
  • and various nuclear decay mechanisms.
It's essential that you are able to answer these questions to carry out these experiments successfully. Failure to answer these questions may result in exclusion from the experiments. The prerequesites include basic knowledge of nuclear and particle physics and solid state physics. The evaluation of the experimental data of the time of flight measurement requires you to write a small programm. Therefore some basic programming skills - preferably in C - are necessary. In addition to the script please refer to the following books for additional information:
  • W. R. Leo, Techniques for Particle Physics Experiments, Springer-Verlag, 1994 (chapters 1, 2.7, 2.8, 6 and 10.7)
  • G. F. Knoll, Radiation Detection and Measurement, John Wiley \& Sons, New York 1978 (chapters 1, 2, 12 and 14)
  • P. R. Bevington, D. K. Robinson, Data Reduction and Error Analysis for the Physical Sciences, McGraw-Hill Inc., 1992 (chapter 4)
  • T. Mayer-Kuckuk, Kernphysik, Teubner Studienbücher Physik, Teubner Stuttgart, 1994 (especially chapter 3)
  • Krane, Kenneth S. Introductory Nuclear Physics. John Wiley & Sons

Questions related to individual experiments:

Part I: The Neutron

  • What are thermal neutrons ?
  • What is moderation and what happens on the microscopic scale?
  • What's the function of polyethylen and lead as part of the neutron source? Due to which pysical properties are they chosen?

Part II: Neutron Detection

  • How does a gas detector work?
  • What is a pulse height spectrum? What is shown there?
  • How is kinetic energy distributed in a two body decay? How does a three body decay differ?
  • What are the reasons for the edge effects of the 3He counter tube?
  • What's the use of a discriminator ?

Part III: Activation Analysis

  • What is the depletion zone of a n-p-junction? Which physical properties have an influence on its spatial dimensions?
  • Which area of semiconductor detectors is sensitive to ionising radiation? How can this region be enlarged?
  • What are photo effect, compton effect and pair production?
  • How does the pulse height spectrum of a monoenergetic gamma source look like if detected by a semiconductor detector?
  • What does the energy resolution of semiconductor detector depend on? How does it compare to the energy resolution of gaseous detectors?
  • What's the intensity of a measured gamma line?

Part IV: Time of Flight Measurement

  • What's the velocity distribution of the neutrons from our neutron source?
  • What properties do (density) distribution functions have?
  • What is described by the opening function of the chopper?
  • What is shown in a time of flight diagram?

Teil V: Radiography

  • Can neutrons blacken a photographic film?
  • Which matrials yield high contrast using X-ray radiography, which using neutrons?

Note on the protocol:

During measurements a clear and readable protocol is to be taken. It should contain a sketch of the experiments and include all settings of the electronics and the most important data and measuring times.

Note on the report:

The report has to be self contained. Make sure that each part (measurement, data and error analysis) can be understood without further reference to the script. Please make sure that graphs and drawings are labeled properly and you make use of your word processor's spell checker.

Links to interesting pages on neutron physics:

IT Department