This work is devoted to neutron spin echo and neutron resonant spin echo instrumentation and research. In the first chapter we describe the basic theory of the methods of neutron spin echo and neutron resonant spin echo. We focus on the very basics of the Spin-Echo (paragraph 1.1), on methods used for studying non-dispersive excitations (like lattice dynamics in glasses), and also on the methods of exploration of the lattice dynamical properties of ordered systems, like bulk crystals. The measurement of phonons in crystals demands tilting of the magnetic fields boundaries, what is explained in paragraph 1.2. In paragraph 1.3 we give the basics of the neutron resonant spin echo with a complete description of the bootstrap technique. We do not pretend to give the full theory of the neutron spin echo, for the details about spin echo, we propose, for example, book [3]. In the second chapter we present calculations to improve the performance of the coils for spin echo. The results in paragraph 2.1 prove the possibility to wind coils not only from a flat tape, but also from wire with round cross-section. Static field coils wound by round wire are successfully being used in the ZETA NRSE option of the IN3 triple-axis spectrometer at the ILL. The results of paragraph 2.2 give good advise how to optimize the bootstrap geometry for better performance. Some of them (like increasing of the thickness of the outer mu-metal shield of the bootstrap coil pair to 1 mm) are also taken into account on IN3-ZETA at the ILL, what resulted in an improvement of the spectrometer performance. The third chapter is devoted to the design study of a multi angle neutron resonance spectrometer. In paragraph 3.1 the derivation of the MIEZE-2 principle is derived from the quantum-mechanical point of view and the basic idea of a multi angle neutron resonance spectrometer is given. In paragraph 3.2 we show the results of ray-tracing simulations to optimize the neutron beam intensity on the detector. This basic estimate demonstrates that a spherical mirror can give appreciable focusing of neutron paths onto the detector with high path length homogeneity, what allows to use focusing geometry for the MIEZE-2 technique. In paragraph 3.3 we present results of the curved static field coil for the curved bootstrap coils. The Boundary Element Method is used for modeling its magnetic field. Simulations show that curved bootstrap coils will show good performance with rather small losses of polarization, because the leakage fields outside of bootstrap are small. The magnetic field inside of the coils will be enough homogeneous to make nearly perfect spin-flips. In paragraph 3.4 we estimate the performance of the curved RF-field coil. We did it in a purely analytical way, making the results free from iteration errors. As a result we conclude that a multi angle neutron resonance spectrometer is possible and that the curved geometry does not lead to significant losses of polarization in comparison with a corresponding flat geometry. The focusing geometry gives a significant increase of beam intensity on the detector, making the construction of a multi angle neutron resonance spectrometer highly favorable. The fourth chapter is devoted to measurements of phonon linewidths in germanium by means of the united TAS-NRSE techniques. Paragraph 4.1 gives the survey of the theoretical and experimental results obtained on phonon lifetimes, paragraph 4.2 provides an overview of the triple-axis technique. In paragraph 4.3 we consider the combination of the TAS and NRSE techniques for measuring of phonons in bulk crystals. The paragraph 4.4 is devoted to the basic data about germanium. In paragraph 4.5 we derive the conditions for the computer-based estimation of the optimum parameters for germanium linewidth measurement on IN3 spectrometer at the ILL. The next paragraph 4.6 is devoted to measurements of phonon linewidths in germanium on IN3-Zeta spectrometer at ILL in November 2001. Our explanation of the experimental result is in good agreement with experiment. In paragraphs 4.7-4.9 we estimate the optimum parameters for the measurements of phonon linewidths in germanium. We conclude that such measurements are hardly possible for phonons in high-symmetry directions because of the high curvature of the dispersion surface across high symmetry direction. However, they are possible for phonons belonging to symmetry planes. We demonstrate how such estimation can be done. Presently an energy resolution of about 2.5 meV can be achieved. We show the parameters of the spectrometer configuration to reach this energy resolution, and estimate the scattering intensities which could be reached in TAS measurements. In the appendixes we derive general data and results having no direct connection to the NSE-NRSE techniques themselves, but are widely used in simulating the magnetic coil performance for spectrometers. We present some new ideas, those are not been completed yet, and present a design for the high-precision coil for the MUPAD project at the ILL.     «

This work is devoted to neutron spin echo and neutron resonant spin echo instrumentation and research. In the first chapter we describe the basic theory of the methods of neutron spin echo and neutron resonant spin echo. We focus on the very basics of the Spin-Echo (paragraph 1.1), on methods used for studying non-dispersive excitations (like lattice dynamics in glasses), and also on the methods of exploration of the lattice dynamical properties of ordered systems, like bulk crystals. The measur...     »

Das Kapitel 1 dieser Arbeit beschreibt die Theorie der Neutron-Spin-Echo (NSE) und Neutron-Resonanz-Spin-Echo (NRSE) Technik. Im Paragraph 2.1 wird gezeigt, dass zur Herstellung der Spulen anstelle von Flachdraht auch runder Draht verwendet werden kann, ohne dass die Polarisation der Neutronen wesentlich verschlechtert wird. Diese Tatsache ermöglicht den Bau von Spektrometern mit grossflächigen Detektoren. Kapitel 3 diskutiert das Design eines MIEZE-2 NRSE-Vielwinkelspektrometers. In Paragraph 3.1 wird das Grundprinzip des Spektrometers beschrieben. Die Paragraphen 3.2-3.4 zeigen anhand von numerischen Berechnungen, dass ein solches Spektrometer technisch realisierbar ist. Paragraph 4.1 gibt einen Überblick über theoretische Modelle, mit denen man die Lebensdauer von Phononen beschreiben kann. Anschliessend wird die Funktionsweise eines Dreiachsenspektrometers und dessen Kombination mit der NRSE-Technik erklärt. In Paragraph 4.4 werden die bekannten experimentellen Ergebnisse von Ge beschrieben. Im Paragraph 4.5 leiten wir die Auswahlregeln für die Messung von Phononen in Ge her und zeigen die Randbedingungen auf, damit Phononen mit höchster Auflösung gemessen werden können. In den folgenden Abschnitten werden erste Messungen von Phononlinienbreiten in Ge mit Hilfe des IN3-Zeta-Spektrometers präsentiert und die Resultate werden im Rahmen der berechneten Auflösung des Spektrometers diskurtiert. Die Diskussion zeigt, dass mit Hilfe der Neutron-Resonanz-Spin-Echo Technik eine Energieauflösung von ca. 2.5 meV erreicht werden kann. Das heisst, dass in Zukunft am FRM-2 mit Hilfe von NRSE gezielt die Linienbreite von Supraleitern charakterisiert werden kann und dass es sogar möglich sein wird, den Einfluss von Isotopen auf die Gitterdynamik zu messen.     «

Das Kapitel 1 dieser Arbeit beschreibt die Theorie der Neutron-Spin-Echo (NSE) und Neutron-Resonanz-Spin-Echo (NRSE) Technik. Im Paragraph 2.1 wird gezeigt, dass zur Herstellung der Spulen anstelle von Flachdraht auch runder Draht verwendet werden kann, ohne dass die Polarisation der Neutronen wesentlich verschlechtert wird. Diese Tatsache ermöglicht den Bau von Spektrometern mit grossflächigen Detektoren. Kapitel 3 diskutiert das Design eines MIEZE-2 NRSE-Vielwinkelspektrometers. In Paragraph 3...     »