Investigating source confusion in PMN J1603−-4904

PMN J1603$-$4904 is a likely member of the rare class of $\gamma$-ray emitting young radio galaxies. Only one other source, PKS 1718$-$649, has been confirmed so far. These objects, which may transition into larger radio galaxies, are a stepping stone to understanding AGN evolution. It is not completely clear how these young galaxies, seen edge-on, can produce high-energy $\gamma$-rays. PMN J1603$-$4904 has been detected by TANAMI Very Long Baseline Interferometry (VLBI) observations and has been followed-up with multiwavelength observations. A Fermi/LAT $\gamma$-ray source has been associated with it in the LAT catalogs. We have obtained Chandra observations of the source in order to consider the possibility of source confusion, due to the relatively large positional uncertainty of Fermi/LAT. The goal was to investigate the possibility of other X-ray bright sources in the vicinity of PMN J1603$-$4904 that could be counterparts to the $\gamma$-ray emission. With Chandra/ACIS, we find no other sources in the uncertainty ellipse of Fermi/LAT data, which includes an improved localization analysis of 8 years of data. We further study the X-ray fluxes and spectra. We conclude that PMN J1603$-$4904 is indeed the second confirmed $\gamma$-ray bright young radio galaxy.Comment: 4 pages, 3 figures, accepted for publication in A&

Fermi-LAT counterparts of IceCube neutrinos above 100 TeV

The IceCube Collaboration has published four years of data and the observed neutrino flux is significantly in excess of the expected atmospheric background. Due to the steeply falling atmospheric background spectrum, events at the highest energies are most likely extraterrestrial. In our previous approach we have studied blazars as the possible origin of the High-Energy Starting Events (HESE) neutrino events at PeV energies. In this work we extend our study to include all HESE neutrinos (which does not include IC 170922A) at or above a reconstructed energy of 100 TeV, but below 1 PeV. We study the X-ray and $\gamma$-ray data of all ($\sim200$) 3LAC blazars that are positionally consistent with the neutrino events above 100 TeV to determine the maximum neutrino flux from these sources. This larger sample allows us to better constrain the scaling factor between the observed and maximum number of neutrino events. We find that when we consider a realistic neutrino spectrum and other factors, the number of neutrinos is in good agreement with the detected number of IceCube HESE events. We also show that there is no direct correlation between \Fermi-LAT $\gamma$-ray flux and the IceCube neutrino flux and that the expected number of neutrinos is consistent with the non-detection of individual bright blazars.Comment: accepted for publication by A&

Damage and deuterium retention of re-solidified tungsten following vertical displacement event-like heat load

AbstractSurface morphology and hydrogen isotope retention of W specimen melted with vertical displacement event-like heat load and subsequent deuterium (D) plasma exposure were studied. Applied heat loads using electron beam without raster scanning were about 190 and 230 MW/m2 in heat flux and 0.08, 0.12 and 0.16s in duration. After the heat load application, specimens showed apparent melting spots with grain growth or dense micrometer scale convex structure. Cracks were observed only in the part with the convex structure. D retention in the melted part of specimens was not significantly larger than in the reference specimen despite large changes of surface characteristics

Optimization of single crystal mirrors for ITER diagnostics

Diagnostic mirrors are planned to be used in all optical diagnostics in ITER. Degradation of mirrors due to e.g. deposition of plasma impurities will hamper the entire performance of affected diagnostics. in situ mirror cleaning by plasma sputtering is presently envisaged for the recovery of contaminated mirrors. There are observations showing a signature of sputtering dependence on crystal orientation. Should such a dependence exist, the sputtering of single crystal mirrors could be minimized, thus prolonging a mirror lifetime. Four single crystal molybdenum mirrors with different orientations were produced to study the effect of crystal orientation on sputtering. Mirrors were exposed to argon plasma under identical plasma conditions relevant to those expected in the mirror cleaning systems of ITER. The energy of impinging ions was about 60 eV. The amount of sputtered material corresponded to about a hundred mirror cleaning cycles in argon. Plasma exposures did not affect the mirror reflectivity. The maximum decrease of specular reflectivity did not exceed 5% at 250 nm. The mirrors with orientations [110]/[101] demonstrated up to 42% less sputtering than the mirrors with other crystal orientations. These findings outline the advantage of a favorable crystal orientation for a cleaning of heavy contaminants from ITER mirrors.Peer reviewe

ERO modelling of tungsten erosion in the linear plasma device PSI-2

Proceedings of the 22nd International Conference on Plasma Surface Interactions 2016, 22nd PSISeries of experiments on tungsten (W) erosion and transport in Argon (Ar) plasma were conducted at the linear plasma device PSI-2. W erosion was measured with three independent methods: WΙ spectroscopy, mass loss and quartz micro-balance (QMB) deposition sensor. Consistent set of data produced in these experiments was interpreted using the 3D ERO code simulations, which have reproduced all the main trends observed. Influence of the physical model assumptions (e.g. energy and angular distributions of sputtered particles) was demonstrated. The effect of WΙ effective quasi-metastable (MS) state population dynamics on spectroscopy measurements is shown; the characteristic relaxation time is determined. The measured physical sputtering yields for W are close to the simulated data obtained in the binary collision approximation (BCA) approach (SDTrimSP code). The remaining discrepancies between simulations and the experiment, mostly in spectroscopy, are accounted to the uncertainties in the plasma parameters and atomic data.Peer reviewe