Design studies towards a 4 MW 170 GHz coaxial-cavity gyrotron

In this work the feasibility of a 4 MW 170 GHz coaxial-cavity gyrotron for continuous wave operation is demonstrated. For the first time complete physical designs of the major gyrotron components are elaborated. In a first step, one possible new operating mode is determined, followed by the development of detailed physical designs of the major gyrotron components: Diode and triode type electron gun, coaxial cavity, two-beam quasi-optical output coupler and depressed collector

Monte Carlo Approach to M-Theory

We discuss supersymmetric Yang-Mills theory dimensionally reduced to zero dimensions and evaluate the SU(2) and SU(3) partition functions by Monte Carlo methods. The exactly known SU(2) results are reproduced to very high precision. Our calculations for SU(3) agree closely with an extension of a conjecture due to Green and Gutperle concerning the exact value of the SU(N) partition functions.Comment: 13 pages, LaTeX, REVTEX, correction of eq.(26) for D=4,6 and non-prime values of

Spectral properties of single Raman-scattered photons

Single photons with well controlled spectral and temporal properties are an essential resource for quantum communication protocols, such as the quantum repeater. Such photons can be generated from a single ion by Raman scattering. A fundamental understanding of the underlying scattering process allows to tailor properties of these Raman photons for the respective application. This work contains a comprehensive experimental study on spectral properties of single Raman-scattered photons, generated by laser excitation. The necessary experimental tools to measure spectra of single photons are presented. In addition, I expand an existing quantum optical model description to corroborate the experimental results. With study of 393nm and 854nm photons emitted from a single 40Ca+ ion, I am able to characterize the dependence of their spectra on properties of the excitation laser. With that, I confirm that the linewidth of a photon generated with weak laser excitation is narrower than the corresponding transition in the 40Ca+ ion. Furthermore, I study the influence of quantum interference effects on the spectrum of the scattered photon. In all cases, the measured spectra are in good agreement with spectra calculated using the model. As an application of tailored spectral properties, atom-photon entanglement is generated. Thereby spectral filtering erases the correlation between frequency and polarization.Einzelne Photonen mit kontrollierten spektralen und zeitlichen Eigenschaften sind eine wichtige Ressource für Quantenkommunikationsprotokolle wie den Quantenrepeater. Solche Photonen können mit einem einzelnen Ion durch Raman-Streuung erzeugt werden. Ein grundlegendes Verständnis des Streuprozesses erlaubt es Raman-Photonen an die jeweilige Anwendung anzupassen. Diese Arbeit enthält eine umfassende experimentelle Analyse der spektralen Eigenschaften von einzelnen durch Laseranregung gestreuten Raman-Photonen. Ich stelle die benötigten experimentellen Werkzeuge zum Messen der Spektren einzelner Photonen vor. Zusätzlich erweitere ich ein bestehendes quantenoptisches Modell, um die experimentellen Ergebnisse zu untermauern. Ich untersuche 393nm und 854nm Photonen, welche mit einem 40Ca+ Ion erzeugt werden um die Abhängigkeit des Spektrums von den Parametern des anregenden Lasers zu charakterisieren. Damit zeige ich, dass die Photonen für eine schwache Laseranregung eine schmalere Linienbreite haben als der entsprechende Übergang im 40Ca+ Ion. Zusätzlich untersuche ich den Einfluss von Quanteninterferenzeffekten auf das Spektrum des gestreuten Photons. In allen Fällen zeigen die gemessenen Spektren eine gute Übereinstimmung mit den modellierten Spektren. Als Anwendung von maßgeschneiderten Spektren wird Atom-Photon Verschränkung erzeugt. Dabei löst spektrales filtern die Korrelation zwischen Frequenz und Polarisation auf

How can consumer trust in organic products be enhanced?

The study presented explores consumer trust in organic food and the effectiveness of enhancing consumer trust by communication strategies on traceability. The research is based on the general finding that trust is one of the most crucial aspects when consumer decide whether to buy or not to buy organic products. However, there are hardly any empirical works which analyse in detail consumer trust in organic food and the ways it can be enhanced. First, based on a quantitative inquiry of 600 persons in Germany the study presented investigates consumer trust in the different actors involved in the organic supply chain (farmers, processors, traders, labels), in distinct attributed qualities such as benefits for health, ecology and animal welfare as well as the customers’ criteria for assessing trustworthiness of the organic products. Empirical data is analysed by multivariate statistics such as cluster analysis to identify distinct consumer segments with respect to their trust characteristics. In a second step there will be a qualitative research method using interviews combined with a visualizing technique. The aim of this method is to understand the consumers’ attitudes towards the supply chain of organic food and the complex construct of trust better. The results shall help to develop communication strategies for enhancing consumer trust in organic food

Variance of fluctuations from Noether invariance

The strength of fluctuations, as measured by their variance, is paramount in the quantitative description of a large class of physical systems, ranging from simple and complex liquids to active fluids and solids. Fluctuations originate from the irregular motion of thermal degrees of freedom and statistical mechanics facilitates their description. Here we demonstrate that fluctuations are constrained by the inherent symmetries of the given system. For particle-based classical many-body systems, Noether invariance at second order in the symmetry parameter leads to exact sum rules. These identities interrelate the global force variance with the mean potential energy curvature. Noether invariance is restored by an exact balance between these distinct mechanisms. The sum rules provide a practical guide for assessing and constructing theories, for ensuring self-consistency in simulation work, and for providing a systematic pathway to the theoretical quantification of fluctuations.Comment: 4 pages, 1 figur

Noether’s theorem in statistical mechanics

Noether’s Theorem relates symmetries to fundamental physical laws. Rather than applying the concept to an action integral in order to obtain conservation laws, here the authors consider Statistical Mechanical objects, such as the free energy and density and power functionals to derive exact force and torque sum rules