Physics with Neutrons 1 (Fundamentals)

• Introduction
• Main principles of neutron generation
• Properties of the free neutron
• Elastic scattering from ordered and disordered systems
• Small angle scattering
• Reflectometry
• Neutron instrumentation

After participation in the module the student is able to:

• explain details of neutron generation
• apply the kinematic theory of elastic neutron scattering
• understand the use of various instruments for neutron scattering
• judge the use of various scattering methods for the determination of the structure of various materials
• know the basic principles of neutron diffraction data from powder and single crystals
• understand diffraction data from non-crystalline materials
• modell the small-angle-scattering data
• explain the basic principles of neutron reflectrometry

• Bachelor degree in physics

The learning outcomes of the module will be achieved via frontal lecture, written and verbal lecturing and powerpoint presentations.

The lecture will be complemented by a weekly exercise class, where students will solve problems under supervision.

• under COVID-19 resctrictions via multimedia otherwise normal lecture with presence of students
• lecture notes
• exercises
• books
• internet

1. G. L. Squires: Introduction to the Theory of Thermal Neutron Scattering, Dover Publications, N. Y. (1966).
2. A. Furrer, J. Mesot, T. Strässle: Neutron Scattering in Condensed Matter Physics, World Scientific, London (2009) .
3. A. Furrer: Frontiers in Neutron Scattering, World Scientific, London (1999).
4. J. M. Carpenter, C.-K. Loong, Elements of Slow-Neutron Scattering, Cambridge University Press, (2015)
5. B.T.M Wills, C.J. Carlile, Experimental Neutron Scattering, Oxford University Press (2009).

There will be an oral exam of 30 minutes duration. Therein the achievement of the competencies given in section learning outcome is tested exemplarily at least to the given cognition level using comprehension questions and sample calculations.

For example an assignment in the exam might be:

• Give the equation which defines the wavelength of matter. Discuss the dependencies Write down the fission reaction.
• Why do fission neutrons have to be moderated? What means moderation?
• Describe the energy transfer in elastic central collision.
• List typical moderators. Argue about the difference of D2O and H2O as moderator. What are the diffusion length in both moderators?
• Discuss the differences/complementarity of reactor neutron sources and spallation neutron sources.
• Note the different cross sections for thermal neutrons. What is the unit for a cross section?
• What is the relation between sigma_coh and scattering length b?
• Give the definition of the double differential cross section for thermal neutrons.
• Define the scattering vector.
• Note the Laue condition in diffraction. What does it mean?
• Note the Bragg equation. What does it describe?
• Definition of structure factor and Debye-Waller factor
• Physical meaning of Bragg peaks on powder diffraction pattern
• What is the measurement principle of SANS. What are the typical application fields for SANS?
• How to characterise surfaces and interfaces? Explain the term “grazing incidence”.

Participation in the exercise classes is strongly recommended since the exercises prepare for the problems of the exam and rehearse the specific competencies.