7,199 research outputs found

    Analytic Criteria for Power Exhaust in Divertors due to Impurity Radiation

    Full text link
    Present divertor concepts for next step experiments such ITER and TPX rely upon impurity and hydrogen radiation to transfer the energy from the edge plasma to the main chamber and divertor chamber walls. The efficiency of these processes depends strongly on the heat flux, the impurity species, and the connection length. Using a database for impurity radiation rates constructed from the ADPAK code package, we have developed criteria for the required impurity fraction, impurity species, connection length and electron temperature and density at the mid-plane. Consistent with previous work, we find that the impurity radiation from coronal equilibrium rates is, in general, not adequate to exhaust the highest expected heating powers in present and future experiments. As suggested by others, we examine the effects of enhancing the radiation rates with charge exchange recombination and impurity recycling, and develop criteria for the minimum neutral fraction and impurity recycling rate that is required to exhaust a specified power. We also use this criteria to find the optimum impurity for divertor power exhaust.Comment: Preprint for the 11th PSI meeting, Adobe pdf with 14 figures, 15 page

    Non-collinearity in di-jet fragmentation in electron-positron scattering

    Get PDF
    We study fragmentation in electron-positron annihilation assuming a di-jet situation, using variables defined independent of any frame. In a collinear situation some of the variables are centered around zero with the small deviations attributed to intrinsic transverse momenta and large deviations attributed to additional hard subprocesses. Of course there is a gradual transition. Our modest goal is to show that covariantly defined variables are well suited to get a feeling for the magnitude of intrinsic transverse momenta.Comment: 10 pages, 12 figures, several minor correction

    Human responses to disasters: a pilot study on peritraumatic emotional and cognitive processing

    Get PDF
    This research article presents the qualitative development and cross-cultural pilot testing of a new instrument measuring emotional and cognitive processing during disasters. The instrument was developed according to a theoretical framework based on narratives from survivors of different types of disaster across Europe. Peritraumatic emotions and cognitions were assessed at three different stages of a disaster. The pilot study consisted of 311 participants responding to the questionnaire using scenario versions of disasters as well as 25 survivors working through the questionnaire using their experiences of real disasters. Both types of analysis were performed across seven countries. Differences in emotions and cognitions during the course of a disaster were displayed. Also, gender, the type of scenario participants were allocated to, and professional experience of emergencies led to differences in item response. As there was little difference between survivors’ and scenario participants’ responses, the use of a scenario in order to test pilot forms of questionnaires for purposive samples with certain characteristics such as limited sizes or access can be supported. For future research, the instrument should be field tested. It is envisaged it will be beneficial for a cross-cultural understanding of the influence of peritraumatic emotions and cognitions not only on posttraumatic psychological outcomes but also on related behavioural responses displayed during disasters

    Axiomatic Information Thermodynamics

    Get PDF
    We present an axiomatic framework for thermodynamics that incorporates information as a fundamental concept. The axioms describe both ordinary thermodynamic processes and those in which information is acquired, used and erased, as in the operation of Maxwell's demon. This system, like previous axiomatic systems for thermodynamics, supports the construction of conserved quantities and an entropy function governing state changes. Here, however, the entropy exhibits both information and thermodynamic aspects. Although our axioms are not based upon probabilistic concepts, a natural and highly useful concept of probability emerges from the entropy function itself. Our abstract system has many models, including both classical and quantum examples.Comment: 52 pages, 5 figures. Revised 28 Mar 201

    Radiation Rates for Low Z Impurities in Edge Plasmas

    Full text link
    The role of impurity radiation in the reduction of heat loads on divertor plates in present experiments such as DIII-D, JET, JT-60, ASDEX, and Alcator C-Mod, and in planned experiments such as ITER and TPX places a new degree of importance on the accuracy of impurity radiation emission rates for electron temperatures below 250 eV for ITER and below 150 eV for present experiments. We have calculated the radiated power loss using a collisional radiative model for Be, B, C, Ne and Ar using a multiple configuration interaction model which includes density dependent effects, as well as a very detailed treatment of the energy levels and meta-stable levels. The "collisional radiative" effects are very important for Be at temperatures below 10 eV. The same effects are present for higher Z impurities, but not as strongly. For some of the lower Z elements, the new rates are about a factor of two lower than those from a widely used, simpler average-ion package (ADPAK) developed for high Z ions and for higher temperatures. Following the approach of Lengyel for the case where electron heat conduction is the dominant mechanism for heat transport along field lines, our analysis indicates that significant enhancements of the radiation losses above collisional radiative model rates due to such effects as rapid recycling and charge exchange recombination will be necessary for impurity radiation to reduce the peak heat loads on divertor plates for high heat flux experiments such as ITER.Comment: Preprint for the 11th PSI meeting, gzipped postscript with 11 figures, 14 page
    • …
    corecore