Rogowski and D-Dot Sensors for Nanosecond High-Voltage and High-Current Pulse Measurements in Impedance-Matched Pulse Generators

To measure the output voltage and current in our impedance-matched solid-state Marx generator we developed a voltage and current sensor integrated with the IMG structure. One of the advantages of our IMG structure is the coaxial inner transmission line (TL). The end of this TL is the output connection, which consists of a grounded ring and a smaller high-voltage (HV) inner conductor (coaxial). This structure is ideal for fitting D-dot and Rogowski-coil sensors, as these sensors can benefit from the strictly defined electric and magnetic fields in this waveguide. We developed D-dot and Rogowski-coil sensors on printed circuit boards (PCB) and show their usability in our application for measuring HV pulses. The sensors have a bandwidth of about 200 MHz, measure voltages up to 20 kV, and currents up to hundreds of amperes. Their simple PCB design makes them easily reproducible and cheap compared to commercial sensors. Although designed for our IMG, they can be fit on any coaxial line. Next, we made passive integrators to partly integrate the differentiated sensor signal, which improves the signal quality when measured with an oscilloscope. Finally, after software signal postprocessing, we achieve far better voltage measurements and similar current measurements compared to commercial probes.</p

Institutions versus market forces: Explaining the employment insecurity of European individuals during (the beginning of) the financial crisis

In reaction to the recent financial crisis, the European Commission re-stated its view that the balance between flexibility and security is the key to success for the future of the European social economy, as well as its belief in the power of institutional arrangements it deems necessary for this balance. However, do powerful institutions actually counter market forces where flexicurity is concerned? In this paper we address this question by analysing the impact of institutional configurations and market factors on perceived employment insecurity among workers in Europe. We use the 4th wave of the European Social Survey for 2008/2009, which covers 22 countries, and implement a multi-level approach where contextual effects are taken into account and individuals are considered to be embedded within a country. We find that policies that secure one’s income and employability skills, such as passive and active labour market policies, are more important for providing employment security for individuals than institutions that secure one’s current job, such as employment protection. Of the economic and labour market factors, general market conditions (measured as employment rate average) and the strength of the financial crisis (measured as gross domestic product growth rate from 2008 to 2009) are both similarly influential in explaining cross-national variance in the employment insecurity perception of individuals. More generally, and most interestingly, we find that institutional factors lose their significance when market factors are taken into account. Thus, it seems that differences in economic and labour market conditions between countries better explain why workers feel insecure about their employment, than the differences in employment and income policies. Although this result could be influenced by the time period under investigation, which is characterized by a financial crisis, results from previous studies using data from different periods suggest that it is not period-specific

Changing principles in European social security

The provision of social security benefits rests on normative principles of social justice. Most strongly manifest in earnings-related social insurance, the principle of reciprocity has been increasingly questioned on grounds of equity, adequacy and fiscal viability, in the wake of socio-economic changes (e.g. post-industralisation, globalisation) and political developments (e.g. Europeanisation). Universalist programmes seem extraordinarily expensive under tight public budgets, and could be criticised as inequitable at a time when middle classes increasingly rely on individual and occupational forms of income security. The principle of need appears to have become more prominent within modern European social security systems keen on targeting resources. Is there empirical evidence which would reflect these alleged trends? Concentrating on three principles inherent in social security transfers (need, universalism and reciprocity) the major concerns of this article are conceptual and empirical. First, it addresses the problem of operationalising social security principles and delineating indicators of change over time. Second, it applies two of these indicators in order to identify and compare the extent to which the three principles have gained or lost prominence since the early 1980s, with empirical evidence taken from the Netherlands, United Kingdom, Germany and Scandinavia. The article argues first that, applying either indicator, there is no cross-national trend towards squeezing reciprocity-based social insurance, but that a convergence between erstwhile strong (Bismarckian) and weak (Beveridgean) principled programmes can be identified. Second, a clear trend towards needs-based social security can be identified within the ¿legal¿ but not within the ¿volume¿ perspective, at least in some programmes and some claimant groups. This is due to both policy changes and favourable labour market conditions. Third, two countries indicate very diverse trends. British social security is distinctive in terms of the erosion of Beveridgean reciprocity, as well as the growing strength of the needs principle. In the Netherlands, there have been considerable shifts in principles underlying certain programmes, but no general trend in either direction can be observed. On the whole, Dutch social security continues to exhibit a strong mix of principles

Fast pulsed power generation with a solid-state impedance-matched Marx generator: concept, design, and first implementation

In this article, we present the concept, design, and first implementation of a new solid-state pulse topology: the solid-state impedance-matched Marx generator (IMG). This new topology can bring fast, adjustable pulse generation to a wide range of pulsed power applications. Where the original IMG is a high-power device (using spark gaps) for relatively low-repetition-rate, high-energy-density physics, we require a pulse source with a (sub)nanosecond rise time at moderate voltages of tens of kilovolts at high repetition rates for transient plasma generation. To achieve this, we adapted the IMG pulse source concept to a solid-state concept with additional transmission lines and metal-oxide-semiconductor field-effect transistor (MOSFET) switches. In this article, we present the general concept, a 20-stage design (with 3-D transient electromagnetic simulations), and a first 5-stage, 5-kV prototype. The prototype achieves 5-6-ns rise time pulses at voltages up to 2.5 kV into a matched 50- \Omega load (due to an oscillation in the drive circuit, the pulse was somewhat distorted at higher voltages) and can generate flexible pulse waveforms. Finally, improvements are suggested to achieve the desired pulse specifications