Exploring the temporally resolved electron density evolution in EUV induced plasmas

We measured for the first time the electron density in an Extreme Ultra-Violet induced plasma. This is achieved in a low-pressure argon plasma by using a method called microwave cavity resonance spectroscopy. The measured electron density just after the EUV pulse is $2.6\cdot10^{16}$ m$^{-3}$. This is in good agreement with a theoretical prediction from photo ionization, which yields a density of $4.5\cdot10^{16}$ m$^{-3}$. After the EUV pulse the density slightly increase due to electron impact ionization. The plasma (i.e. electron density) decays in tens of microseconds.Comment: 3 pages, 4 figure

Exploring the electron density in plasmas induced by extreme ultraviolet radiation in argon

The new generation of lithography tools use high energy EUV radiation which ionizes the present background gas due to photoionization. To predict and understand the long term impact on the highly delicate mirrors It is essential to characterize these kinds of EUV-induced plasmas. We measured the electron density evolution in argon gas during and just after irradiation by a short pulse of EUV light at 13.5 nm by applying microwave cavity resonance spectroscopy. Dependencies on EUV pulse energy and gas pressure have been explored over a range relevant for industrial applications. Our experimental results show that the maximum reached electron density depends linearly on pulse energy. A quadratic dependence - caused by photoionization and subsequent electron impact ionization by free electrons - is found from experiments where the gas pressure is varied. This is demonstrated by our theoretical estimates presented in this manuscript as well.Comment: submitted to J. Phys. D. 16 pages, 8 figure

Applying an accurate spherical model to gamma-ray burst afterglow observations

We present results of model fits to afterglow data sets of GRB970508, GRB980703 and GRB070125, characterized by long and broadband coverage. The model assumes synchrotron radiation (including self-absorption) from a spherical adiabatic blast wave and consists of analytic flux prescriptions based on numerical results. For the first time it combines the accuracy of hydrodynamic simulations through different stages of the outflow dynamics with the flexibility of simple heuristic formulas. The prescriptions are especially geared towards accurate description of the dynamical transition of the outflow from relativistic to Newtonian velocities in an arbitrary power-law density environment. We show that the spherical model can accurately describe the data only in the case of GRB970508, for which we find a circumburst medium density consistent with a stellar wind. We investigate in detail the implied spectra and physical parameters of that burst. For the microphysics we show evidence for equipartition between the fraction of energy density carried by relativistic electrons and magnetic field. We also find that for the blast wave to be adiabatic, the fraction of electrons accelerated at the shock has to be smaller than 1. We present best-fit parameters for the afterglows of all three bursts, including uncertainties in the parameters of GRB970508, and compare the inferred values to those obtained by different authors

New economic geography, empirics, and regional policy

There are doubts about the effectiveness of regional policy. Well known are the fruitless attempts of Italy to bridge the gap between the Mezzogiorno and the North, of Germany to bridge the gap between the Neue Länder and the West, and of the European Commission to reduce regional disparities in general. We validate one explanation: agglomeration advantages lock business activity in relatively prosperous core regions, even though wages – and thus production costs – tend to be higher there. We set off from the ‘New Economic Geography’, a set of general equilibrium models that focus on location choice. Theory, descriptive statistics, and econometric analysis support the conclusion that the European economic geography is characterized by a network of local and stable core periphery systems. This implies that disparities between core regions and their peripheries at a (sub) provincial level of regional aggregation are with us to stay, as regional policy targeted on peripheries tends to be insufficient to counter centripetal market forces. Moreover, even if such policy has an impact, it may be adverse, as core regions may benefit disproportionately in the long run. A focus of regional policy on local agglomerations, which have a realistic chance to hold on to economic activity, is therefore desirable.

The fake food buffet - a new method in nutrition behaviour research

Experimental research in behavioural nutrition is often limited by practical applicability. In the present study, we assess the reproducibility and validity of a new experimental method using food replicas. A total of fifty-seven people were invited on two separate occasions with an interval of 2 weeks to serve themselves a meal from a fake food buffet (FFB) containing replica carrots, beans, pasta and chicken. The external validity of the FFB was assessed in a second study by comparing meals served from replica foods (beans, pasta, chicken) with meals served from a corresponding real food buffet (RFB). For the second study, forty-eight participants were invited on two separate occasions; first to serve themselves a meal from the FFB or an RFB and 2 weeks later from the other buffet. The amounts of food items served and (theoretical) energy content were compared. Correlation coefficients between the amounts of fake foods served were 0·77 (95% CI 0·68, 0·86) for chicken, 0·79 (95% CI 0·68, 0·87) for carrots, 0·81 (95% CI 0·69, 0·89) for beans and 0·89 (95% CI 0·82, 0·93) for pasta. For the FFB meal and the RFB meal, the correlations ranged between 0·76 (95% CI 0·73, 0·91) for chicken and 0·87 (95% CI 0·77, 0·92) for beans. The theoretical energy of the fake meal was 132kJ (32kcal) lower compared to the energy of the real meal. Results suggest that the FFB can be a valuable tool for the experimental assessment of relative effects of environmental influences on portion sizes and food choice under well-controlled condition

Superconducting and structural properties of plasma sprayed YBaCuO layers deposited on metallic substrates

The properties of plasma sprayed Y-Ba-Cu-O coatings deposited on metallic substrates are studied. Stainless steel, nickel steels and pure nickel are used as substrate. Y-Ba-Cu-O deposited on stainless steel and nickel steel reacts with the substrate. This interaction can be suppressed by using an yttria-stabilized zirconia (YsZ) diffusion barrier. However, after heat treatment the Y-Ba-Cu-O layers on YsZ show cracks perpendicular to the surface. As a result the critical current density is very low. The best results are obtained for Y-Ba-Cu-O deposited on pure nickel; here no cracks perpendicular to the surface are observed. The critical current increases with the anneal temperature but annealing for longer than 10 h does not seem to improve the superconducting properties any further