REALISTIC 3-DIMENSIONAL EIGENMODAL ANALYSIS OF ELECTROMAGNETIC CAVITIES USING SURFACE IMPEDANCE BOUNDARY CONDITIONS

Abstract The new X-ray Free Electron Laser (SwissFEL) at the Paul Scherrer Institute (PSI) employs, among many other radio frequency elements, a transverse deflecting cavity for beam diagnostics. Since the fabrication process is expensive, an accurate 3-D eigenmodal analysis is indispensable. The software package Femaxx has been developed for solving large scale eigenvalue problems on distributed memory parallel computers. Usually, it is sufficient to assume that the tangential electric field vanishes on the cavity wall (PEC boundary conditions). Of course, in reality, the cavity wall is conductive such that the tangential electrical field on the wall is nonzero. In order to more realistically model the electric field we impose surface impedance boundary conditions (SIBC) arising from the skin effect model. The resulting nonlinear eigenvalue problem is solved with a nonlinear Jacobi-Davidson method. We demonstrate the performance of the method. First, we investigate the fundamental mode of a pillbox cavity. We study resonance, skin depth and quality factor as a function of the cavity wall conductivity. Second, we analyze the transverse deflecting cavity of the SwissFEL to assess the capability of the method for technologically relevant problems. FORMULATION OF THE PROBLEM We wish to calculate the resonant frequencies and the corresponding field distribution in a dielectric electromagnetic cavity. The cavity wall Γ is assumed to be of arbitrary shape; there is no aperture or hole in Γ. The surface conductivity σ s of Γ is large but finite. The interior Ω of the cavity is assumed to be source-free, and is characterized by (µ 0 µ r , ε 0 ε r ). µ 0 and ε 0 are the magnetic permeability and electric permittivity in free space. µ r and ε r are relative magnetic permeability and relative electric permittivity, respectively. At microwave frequencies, µ r and ε r can be assumed to be non-dispersive. In the time-harmonic regime, after eliminating the electric field E(x), the magnetic field H(x) satisfies Here, k 0 =ω √ µ 0 ε 0 is the complex wave number in free space,ω = ω + iα is the complex angular frequency with ω the angular frequency and α the exponential decay rate. * hguo@inf. ethz.ch † arbenz@inf. ethz.ch ‡ benedikt.oswald@ps i.ch We use the surface impedance boundary condition (SIBC) Here, Z s is the complex surface impedance and n the surface normal vector pointing outwards. We employ Z s based on the theoretical skin effect model [2] where σ s is the surface conductivity, and δ is the skin depth. The real part of Z s is the surface resistivity, i.e., The skin depth δ is [2] δ depends on the angular frequency ω. Note that the skin effect model is appropriate only if σ s is large enough such that (according to The finite element method (FEM) is a suitable method for arbitrary geometrical scales. In order to apply the FEM we use the weak form of Eq (1), see Ω µ r H · ∇q dx = 0. Here, V denotes the functions in H(curl; Ω) that satisfy the SIBC boundary conditions and W =

Swiss paediatrician survey on complementary medicine

In Switzerland, complementary medicine (CM) is officially recognised within the healthcare system and mainly practised in an integrative manner, in conjunction with conventional medicine. As in other countries, there is high demand for and use of CM with children. However, there has so far been no research into the attitude towards, training in and offer of CM among paediatricians in Switzerland. Our study addresses this gap by investigating these topics with an online survey of paediatricians in Switzerland.METHODS: We conducted a national online survey using a 19-item, self- reporting questionnaire among all ordinary and junior members of the Swiss Society of Paediatrics (SSP). A comparison of the study sample with the population of all paediatricians registered with the Swiss Medical Association (FMH) allowed an assessment of the survey’s representativeness. The data analysis was performed on the overall group level as well as for predefined subgroups (e.g. sex, age, language, workplace and professional experience).RESULTS: 1890 paediatricians were approached and 640, from all parts of Switzerland, responded to the survey (response rate 34%). Two thirds of respondents were female, were aged between 35 and 55 years, trained as paediatric generalist and worked in a practice. Apart from young paediatricians in training, the study sample was representative of all Swiss paediatricians. 23% had attended training in CM, most frequently in phytotherapy, homeopathy, acupuncture/traditional Chinese medicine (TCM) and anthroposophic medicine. 65% were interested in CM courses and training. 16% provide CM services to their patients and almost all paediatricians (97%) are asked by patients/parents about CM therapies. More than half of the responding paediatricians use CM for themselves or their families. 42% were willing to contribute to paediatric CM research.CONCLUSIONS: In a representative sample of paediatricians in Switzerland, their personal attitude towards CM is positive, emphasised by great interest in CM training, a willingness to contribute to CM research and a high rate of paediatricians who use CM for themselves and their families. In contrast, the percentage of paediatricians offering CM is currently rather low despite strong demand for CM for children. This study provides key pointers for the future development of complementary and integrative medicine for children in Switzerland

H5hut: A high-performance I/O library for particle-based simulations

Particle-based simulations running on large high-performance computing systems over many time steps can generate an enormous amount of particle- and field-based data for post-processing and analysis. Achieving high-performance I/O for this data, effectively managing it on disk, and interfacing it with analysis and visualization tools can be challenging, especially for domain scientists who do not have I/O and data management expertise. We present the H5hut library, an implementation of several data models for particle-based simulations that encapsulates the complexity of HDF5 and is simple to use, yet does not compromise performance

Fuming Acid and Cryptanalysis: Handy Tools for Overcoming a Digital Locking and Access Control System - Full Version

We examine the widespread SimonsVoss digital locking system 3060 G2 that relies on an undisclosed, proprietary protocol to mutually authenticate transponders and locks. For assessing the security of the system, several tasks have to be performed: By decapsulating the used microcontrollers with acid and circumventing their read-out protection with UV-C light, the complete program code and data contained in door lock and transponder are extracted. As a second major step, the multi-pass challenge-response protocol and corresponding cryptographic primitives are recovered via low-level reverse-engineering. The primitives turn out to be based on DES in combination with a proprietary construction. Our analysis pinpoints various security vulnerabilities that enable practical key-recovery attacks. We present two different approaches for unauthorizedly gaining access to installations. Firstly, an attacker having physical access to a door lock can extract a master key, allowing to mimic transponders, in altogether 30 minutes. A second, purely logical attack exploits an implementation flaw in the protocol and works solely via the wireless interface. As the only prerequisite, a valid ID of a transponder needs to be known (or guessed). After executing a few (partial) protocol runs in the vicinity of a door lock, and some seconds of computation, an adversary obtains all of the transponder’s access rights

Progress on H5Part: A Portable High Performance Parallel DataInterface for Electromagnetics Simulations

Significant problems facing all experimental andcomputationalsciences arise from growing data size and complexity. Commonto allthese problems is the need to perform efficient data I/O ondiversecomputer architectures. In our scientific application, thelargestparallel particle simulations generate vast quantitiesofsix-dimensional data. Such a simulation run produces data foranaggregate data size up to several TB per run. Motived by the needtoaddress data I/O and access challenges, we have implemented H5Part,anopen source data I/O API that simplifies the use of the HierarchicalDataFormat v5 library (HDF5). HDF5 is an industry standard forhighperformance, cross-platform data storage and retrieval that runsonall contemporary architectures from large parallel supercomputerstolaptops. H5Part, which is oriented to the needs of the particlephysicsand cosmology communities, provides support for parallelstorage andretrieval of particles, structured and in the future unstructuredmeshes.In this paper, we describe recent work focusing on I/O supportforparticles and structured meshes and provide data showing performance onmodernsupercomputer architectures like the IBM POWER 5

From Improved Leakage Detection to the Detection of Points of Interests in Leakage Traces

Leakage detection usually refers to the task of identifying data-dependent information in side-channel measurements, independent of whether this information can be exploited. Detecting Points-Of-Interest (POIs) in leakage traces is a complementary task that is a necessary first step in most side-channel attacks, where the adversary wants to turn this information into (e.g.) a key recovery. In this paper, we discuss the differences between these tasks, by investigating a popular solution to leakage detection based on a t-test, and an alternative method exploiting Pearson\u27s correlation coefficient. We first show that the simpler t-test has better sampling complexity, and that its gain over the correlation-based test can be predicted by looking at the Signal-to-Noise Ratio (SNR) of the leakage partitions used in these tests. This implies that the sampling complexity of both tests relates more to their implicit leakage assumptions than to the actual statistics exploited. We also put forward that this gain comes at the cost of some intuition loss regarding the localization of the exploitable leakage samples in the traces, and their informativeness. Next, and more importantly, we highlight that our reasoning based on the SNR allows defining an improved t-test with significantly faster detection speed (with approximately 5 times less measurements in our experiments), which is therefore highly relevant for evaluation laboratories. We finally conclude that whereas t-tests are the method of choice for leakage detection only, correlation-based tests exploiting larger partitions are preferable for detecting POIs. We confirm this intuition by improving automated tools for the detection of POIs in the leakage measurements of a masked implementation, in a black box manner and without key knowledge, thanks to a correlation-based leakage detection test

E-Portfolios zur Unterstützung selbstorganisierter Tutoren- und Tutorinnentätigkeiten

Dieser Beitrag beschreibt den Einsatz von E-Portfolios zur Unterstützung selbstorganisierter Tutoren- und Tutorinnentätigkeiten in offenen Lernkontexten. Im Rahmen eines hochschuldidaktischen Praktikums betreuen Studierende der Wirtschaftspädagogik Studienanfänger/innen, die an einer Einführungsveranstaltung zum wissenschaftlichen Arbeiten teilnehmen, und dokumentieren dabei ihre Tätigkeit in einem E-Portfolio. Auf diese Weise wird die reflexive Lernprozessbegleitung mit einer Möglichkeit zur Zertifizierung semi-formeller, eigenverantwortlicher und selbstorganisierter Betreuungstätigkeiten kombiniert. (DIPF/ Orig.