Investigation of a 2-Colour Undulator FEL Using Puffin

Initial studies of a 2-colour FEL amplifier using one monoenergetic electron beam are presented. The interaction is modelled using the unaveraged, broadband FEL code Puffin. A series of undulator modules are tuned to generate two resonant frequencies along the FEL interaction and a self-consistent 2-colour FEL interaction at widely spaced non-harmonic wavelengths at 1nm and 2.4nm is demonstrated.Comment: Submitted to The 35th International Free-Electron Laser Conference, Manhattan, New York (2013

Magnetization reversal and local switching fields of ferromagnetic Co/Pd microtubes with radial magnetization

Three-dimensional nanomagnetism is a rapidly growing field of research covering both noncollinear spin textures and curved magnetic geometries including microtubular structures. We spatially resolve the field-induced magnetization reversal of free-standing ferromagnetic microtubes utilizing multifrequency magnetic force microscopy (MFM). The microtubes are composed of Co/Pd multilayer films with perpendicular magnetic anisotropy that translates to an anisotropy with radial easy axis upon rolling-up. Simultaneously mapping the topography and the perpendicular magnetostatic force derivative, the relation between surface angle and local magnetization configuration is evaluated for a large number of locations with slopes exceeding 45 degrees. The angle-dependence of the switching field is concurrent with the Kondorsky model, i.e., the rolled-up nanomembrane behaves like a planar magnetic film with perpendicular anisotropy and a pinning dominated magnetization reversal. Additionally, we discuss methodological challenges when detecting magnetostatic force derivatives near steep surfaces

Design considerations for table-top, laser-based VUV and X-ray free electron lasers

A recent breakthrough in laser-plasma accelerators, based upon ultrashort high-intensity lasers, demonstrated the generation of quasi-monoenergetic GeV-electrons. With future Petawatt lasers ultra-high beam currents of ~100 kA in ~10 fs can be expected, allowing for drastic reduction in the undulator length of free-electron-lasers (FELs). We present a discussion of the key aspects of a table-top FEL design, including energy loss and chirps induced by space-charge and wakefields. These effects become important for an optimized table-top FEL operation. A first proof-of-principle VUV case is considered as well as a table-top X-ray-FEL which may open a brilliant light source also for new ways in clinical diagnostics.Comment: 6 pages, 4 figures; accepted for publication in Appl. Phys.

How does successive inpatriation contribute to subsidiary capability building and subsidiary evolution? An organizational knowledge creation perspective

Intra-company knowledge transfer is a key source of competitive advantage for multinational companies (MNCs) and this knowledge is usually embedded in individuals. Drawing on organizational knowledge creation theory, we explore how inpatriation contributes to knowledge transfer and, in turn, subsidiary performance. Inpatriation involves the international assignment of employees from an MNC’s foreign subsidiary to its headquarters. Despite increasing attention to the role of inpatriation, we lack a clear understanding of whether and how inpatriates provide value to their subsidiaries after returning from headquarters. Through a qualitative case study of Japanese MNCs, we demonstrate the process through which inpatriates’ knowledge transfer contributes to subsidiary capability building and subsidiary evolution over time, and explain why successive inpatriation is thus critical to enhance subsidiary performance. Our theoretical model highlights the value of inpatriates as knowledge agents, reveals the process through which inpatriates transfer knowledge between HQ and subsidiaries, and provides a more nuanced understanding of the micro-foundations of intra-MNC knowledge transfer processes. Based on these findings, we argue that inpatriation is not merely a staffing method that is complementary to expatriation, but a key practice in its own right to support subsidiaries’ growth and performance

Why and how does shared language affect subsidiary knowledge inflows? A social identity perspective

We draw on social identity theory to conceptualize a moderated mediation model that examines the relationship between shared language among subsidiary and HQ managers, and subsidiaries’ knowledge inflows from HQ. Specifically, we study (1) whether this relationship is mediated by the extent to which subsidiary managers share HQ goals and vision, and the extent to which HR decisions are centralized; and (2) whether subsidiary type moderates these mediated relationships. Building on a sample of 817 subsidiaries in nine countries/regions, we find support for our model. Implications for research on HQ-subsidiary knowledge flows, social identity theory and international HRM are discussed

The bridging role of expatriates and inpatriates in knowledge transfer in multinational corporations

Drawing on the knowledge-based view of the firm, this paper provides the first empirical study that explicitly investigates the relationship between different categories of international assignees and knowledge transfer in multinational corporations (MNCs). Specifically, we examine (1) the extent to which expatriate presence in different functional areas is related to knowledge transfer from and to headquarters in these functions; and (2) the extent to which different categories of international assignees (expatriates vs. inpatriates) contribute to knowledge transfer from and to headquarters. We base our investigation on a large scale survey, encompassing data from more than 800 subsidiaries of MNCs in thirteen countries. By disaggregating the role of knowledge transfer across management functions, directions of knowledge transfer, and type of international assignees, we find that (1) expatriate presence generally increases function-specific knowledge transfer from and, to a lesser extent, to headquarters; and that (2) the relevance of expatriates and former inpatriates varies for knowledge flows between headquarters and subsidiaries. Additionally, we discuss implications for research and practice, in particular regarding different management functions and different forms of international assignments, and provide suggestions for future research

Readout for intersatellite laser interferometry: Measuring low frequency phase fluctuations of HF signals with microradian precision

Precision phase readout of optical beat note signals is one of the core techniques required for intersatellite laser interferometry. Future space based gravitational wave detectors like eLISA require such a readout over a wide range of MHz frequencies, due to orbit induced Doppler shifts, with a precision in the order of $\mu \textrm{rad}/\sqrt{\textrm{Hz}}$ at frequencies between $0.1\,\textrm{mHz}$ and $1\,\textrm{Hz}$. In this paper, we present phase readout systems, so-called phasemeters, that are able to achieve such precisions and we discuss various means that have been employed to reduce noise in the analogue circuit domain and during digitisation. We also discuss the influence of some non-linear noise sources in the analogue domain of such phasemeters. And finally, we present the performance that was achieved during testing of the elegant breadboard model of the LISA phasemeter, that was developed in the scope of an ESA technology development activity.Comment: submitted to Review of Scientific Instruments on April 30th 201

The LISA pathfinder mission

ISA Pathfinder (LPF), the second of the European Space Agency's Small Missions for Advanced Research in Technology (SMART), is a dedicated technology validation mission for future spaceborne gravitational wave detectors, such as the proposed eLISA mission. LISA Pathfinder, and its scientific payload - the LISA Technology Package - will test, in flight, the critical technologies required for low frequency gravitational wave detection: it will put two test masses in a near-perfect gravitational free-fall and control and measure their motion with unprecedented accuracy. This is achieved through technology comprising inertial sensors, high precision laser metrology, drag-free control and an ultra-precise micro-Newton propulsion system. LISA Pathfinder is due to be launched in mid-2015, with first results on the performance of the system being available 6 months thereafter. The paper introduces the LISA Pathfinder mission, followed by an explanation of the physical principles of measurement concept and associated hardware. We then provide a detailed discussion of the LISA Technology Package, including both the inertial sensor and interferometric readout. As we approach the launch of the LISA Pathfinder, the focus of the development is shifting towards the science operations and data analysis - this is described in the final section of the paper

EMIL The energy materials in situ laboratory Berlin a novel characterization facility for photovoltaic and energy materials

A knowledge based approach towards developing a new generation of solar energy conversion devices requires a fast and direct feedback between sophisticated analytics and state of the art processing test facilities for all relevant material classes. A promising approach is the coupling of synchrotron based X ray characterization techniques, providing the unique possibility to map the electronic and chemical structure of thin layers and interface regions with relevant in system in situ sample preparation or in operando analysis capabilities in one dedicated laboratory. EMIL, the Energy Materials In situ Laboratory Berlin, is a unique facility at the BESSY II synchrotron light source. EMIL will be dedicated to the in system, in situ, and in operando X ray analysis of materials and devices for energy conversion and energy storage technologies including photovoltaic applications and photo electrochemical processes. EMIL comprises up to five experimental end stations, three of them can access X rays in an energy range of 80 eV 10 keV. For example, one key setup of EMIL combines a suite of advanced spectroscopic characterization tools with industry relevant deposition facilities in one integrated ultra high vacuum system. These deposition tools allow the growth of PV devices based on silicon, compound semiconductors, hybrid heterojunctions, and organo metal halide perovskites on up to 6 sized substrates. EMIL will serve as a research platform for national and international collaboration in the field of photovoltaic photocatalytic energy conversion and beyond. In this paper, we will provide an overview of the analytic and material capabilities at EMIL

In-flight thermal experiments for LISA pathfinder: simulating temperature noise at the inertial sensors

Thermal Diagnostics experiments to be carried out on board LISA Pathfinder (LPF) will yield a detailed characterisation of how temperature fluctuations affect the LTP (LISA Technology Package) instrument performance, a crucial information for future space based gravitational wave detectors as the proposed eLISA. Amongst them, the study of temperature gradient fluctuations around the test masses of the Inertial Sensors will provide as well information regarding the contribution of the Brownian noise, which is expected to limit the LTP sensitivity at frequencies close to 1 mHz during some LTP experiments. In this paper we report on how these kind of Thermal Diagnostics experiments were simulated in the last LPF Simulation Campaign (November, 2013) involving all the LPF Data Analysis team and using an end-to-end simulator of the whole spacecraft. Such simulation campaign was conducted under the framework of the preparation for LPF operations