Ferrite Material Characterization in a Static Bias Field for the Design of a Tunable Cavity
During the development of ferrite-loaded accelerating cavities, the electromagnetic properties of the dispersive ferrite material need to be known. We describe a coaxial short-circuit measurement technique to measure the complex permeability of toroidal-shaped samples (127mm outer and 70mm inner diameter) that are exposed to an external magnetic bias field. The external magnetic bias field is applied perpendicular to the RF magnetic field. With this method it is possible to characterize the frequency dependence of the permeability for a frequency range of 1100MHz. The dependence of the permeability on the external magnetic bias is presented for the ferrite G-510 from Trans-Tech Inc. and the material characterization is shown in the same frequency range. The measurement results are verified by simulations of the measurement set-up.
Determination of Beam Coupling Impedance in the Frequency Domain
The concept of beam coupling impedance describes the electromagnetic interaction of 
uniformly moving charged particles with their surrounding structures in the Frequency 
Domain (FD). In synchrotron accelerators, beam coupling impedances can lead to beam 
induced component heating and coherent beam instabilities. Thus, in order to ensure 
the stable operation of a synchrotron, its impedances have to be quantified and their effects have to be controlled. Nowadays, beam coupling impedances are mostly obtained 
by Fourier transform of wake potentials, which are the results of Time Domain (TD) simulations. However, at low frequencies, low beam velocity, or for dispersive materials, 
TD simulations become unhandy. In this area, analytical calculations of beam coupling 
impedance in the FD, combined with geometry approximations, are still widely used. 
This thesis describes the development of two electromagnetic field solvers to obtain 
the beam coupling impedance directly in the FD, where the beam velocity is only a 
parameter and dispersive materials can be included easily. 
One solver is based on the Finite Integration Technique (FIT) on a staircase mesh. It 
is implemented both in 2D and 3D. However, the staircase mesh is inefficient on curved 
structures, which is particularly problematic for the modeling of a dipole source, that is 
required for the computation of the transverse beam coupling impedance. 
This issue is overcome by the second solver developed in this thesis, which is based 
on the Finite Element Method (FEM) on an unstructured triangular mesh. It is implemented in 2D and includes an optional Surface Impedance Boundary Condition (SIBC). 
Thus, it is well suited for the computation of longitudinal and transverse impedances 
of long beam pipe structures of arbitrary cross-section. Besides arbitrary frequency 
and beam velocity, also dispersive materials can be chosen, which is crucial for the 
computation of the impedance of ferrite kicker magnets. 
Numerical impedance simulations always contain simplifications, therefore they have 
to be confirmed by dedicated measurements. However, the beam coupling impedance 
of a single accelerator component cannot be measured directly. Therefore, a dedicated 
RF-laboratory was established at GSI, in order to measure broadband beam coupling 
impedances on the bench by means of the wire method, i.e. without beam. A detailed 
analysis of measurement methods is given by comparison of analytical, numerical, and 
measurement results for simplified accelerator devices. One conclusion is, that also the 
bench measurements have to be validated by dedicated electromagnetic simulations. 
The thesis closes with selected impedance induced effects on the beam revolving in 
the synchrotron and relevant impedance results for the future SIS-100 synchrotron for 
the FAIR project at GSI.
Computer-Aided System of Virtual Testing of Gas Turbine Engines
The article describes the concept of a virtual lab that includes subsystem of gas turbine engine simulation, subsystem of experiment planning, subsystem of measurement errors simulation, subsystem of simulator identification and others. The basis for virtual lab development is the computer-aided system of thermogasdynamic research and analysis “ASTRA”. The features of gas turbine engine transient modes simulator are described. The principal difference between the simulators of transient and stationary modes of gas turbine engines is that the energy balance of the compressor and turbine becomes not applicable. The computer-aided system of virtual gas turbine engine testing was created using the developed transient modes simulator. This system solves the tasks of operational (throttling, speed, climatic, altitude) characteristics calculation, analysis of transient dynamics and selection of optimal control laws. Besides, the system of virtual gas turbine engine testing is a clear demonstration of gas turbine engine working process and the regularities of engine elements collaboration. The interface of the system of virtual gas turbine engine testing is described in the article and some screenshots of the interface elements are provided. The developed system of virtual gas turbine engine testing provides means for reducing the laboriousness of gas turbine engines testing. Besides, the implementation of this system in the learning process allows the diversification of lab works and therefore improve the quality of training.