Investigating 16O with the 15N(p,{\alpha})12C reaction

The 16O nucleus was investigated through the 15N(p,{\alpha})12C reaction at excitation energies from Ex = 12 231 to 15 700 keV using proton beams from a 5 MeV Van de Graaff accelerator at beam energies of Ep = 331 to 3800 keV. Alpha decay from resonant states in 16O was strongly observed for ten known excited states in this region. The candidate 4-alpha cluster state at Ex = 15.1 MeV was investigated particularly intensely in order to understand its particle decay channels.Comment: Submitted for Proceedings of Fourth International Workshop on State of the Art in Nuclear Cluster Physics (SOTANCP4), held from May 13 - 18, 2018 in Galveston, TX, US

Treibhausgasflüsse beim Anbau von Winterweizen und Kleegras

At the experimental station Viehhausen, 30 km north of Munich in southern Germany, N2O, CO2 and CH4 fluxes between soil and atmosphere were measured to investigate the influence of site-related factors and cultivation-technique on the emissions of these greenhouse gases. Clover-grass as well as several wheat cropping systems (with and without biogas slurry) were analyzed under the conditions of organic farming. This paper shows the results of the vegetation period of 2009. The N2O emissions from the wheat fields were higher than those from clover-grass fields. Ploughing-in of the legume-grass biomass resulted in releasing distinctive N2O emissions. For CH4 fluxes the arable soils were a net sink, especially in cropping systems with winter wheat

VME Readout at and Below the Conversion Time Limit

The achievable acquisition rates of modern triggered nuclear physics experiments are heavily dependent on the readout software, in addition to the limits given by the utilized hardware. This paper presents an asynchronous readout scheme that significantly improves the livetime of an otherwise synchronous triggered Versa Module Eurocard Bus-based data acquisition system. A detailed performance analysis of this and other readout schemes, in terms of the basic data transfer operations, is described. The performance of the newly developed scheme as well as synchronous schemes on two systems has been measured. The measurements show excellent agreement with the detailed description. For the second system, which previously used a synchronous readout, the deadtime ratio is at a 20-kHz trigger request frequency reduced by 30% compared to the nearest contender, allowing 10% more events to be recorded in the same time. The interaction between the network and readout tasks for single-core processors is also investigated. A livetime ratio loss of a few percents can be observed, depending on the size of the data chunks given to the operating system kernel for network transfer. With appropriately chosen chunk size, the effect can be mitigated

Physical Conditoins in Orion's Veil II: A Multi-Component Study of the Line of Sight Toward the Trapezium

Orion's Veil is an absorbing screen that lies along the line of sight to the Orion H II region. It consists of two or more layers of gas that must lie within a few parsecs of the Trapezium cluster. Our previous work considered the Veil as a whole and found that the magnetic field dominates the energetics of the gas in at least one component. Here we use high-resolution STIS UV spectra that resolve the two velocity components in absorption and determine the conditions in each. We derive a volume hydrogen density, 21 cm spin temperature, turbulent velocity, and kinetic temperature, for each. We combine these estimates with magnetic field measurements to find that magnetic energy significantly dominates turbulent and thermal energies in one component, while the other component is close to equipartition between turbulent and magnetic energies. We observe molecular hydrogen absorption for highly excited v, J levels that are photoexcited by the stellar continuum, and detect blueshifted S III and P III. These ions must arise from ionized gas between the mostly neutral portions of the Veil and the Trapezium and shields the Veil from ionizing radiation. We find that this layer of ionized gas is also responsible for He I absorption in the Veil, which resolves a 40-year-old debate on the origin of He I absorption towards the Trapezium. Finally, we determine that the ionized and mostly atomic layers of the Veil will collide in less than 85,000 years.Comment: 43 pages, 15 figures, to be published in Ap

Hubble Space Telescope Images of Magellanic Cloud Planetary Nebulae: Data and Correlations across Morphological Classes

The morphology of planetary nebulae (PNe) provides an essential tool for understanding their origin and evolution, as it reflects both the dynamics of the gas ejected during the TP-AGB phase, and the central star energetics. Here we study the morphology of 27 Magellanic Cloud planetary nebulae (MCPNe) and present an analysis of their physical characteristics across morphological classes. Similar studies have been successfully carried out for galactic PNe, but were compromised by the uncertainty of individual PN distances. We present our own HST/FOC images of 15 Magellanic Cloud PNe (MCPNe) acquired through a narrow-band lambda 5007 [O III] filter. We use the Richardson-Lucy deconvolution technique on these pre-COSTAR images to achieve post-COSTAR quality. Three PNe imaged before and after COSTAR confirm the high reliability of our deconvolution procedure. We derive morphological classes, dimensions, and surface photometry for all these PNe. We have combined this sample with HST/PC1 images of 15 MCPNe, three of which are in common with the FOC set, acquired by Dopita et al. (1996), to obtain the largest MCPN sample ever examined from the morphological viewpoint. By using the whole database, supplemented with published data from the literature, we have analyzed the properties of the MCPNe and compared them to a typical, complete galactic sample. Morphology of the MCPNe is then correlated with PN density, chemistry, and evolution.Comment: text file lstanghe_mcpn.tex (LaTex); Figures 2 through 10, Figure 5 is in 3 parts (a,b,c); Figure 1 available by regular mail only; ApJ, in press, November 10, 199