Stau Search in IceCube

The tau lepton’s supersymmetric partner, the stau, appears in some models as the next-to-lightest supersymmetric particle. Their deacy process into the lightest superpartner is usually suppressed by supersymmetry breaking, which makes it a long-lived particle. In this scenario, its signature is a long, minimally ionizing track when traveling through the IceCube detector. Independent of their primary energy, the stau tracks appear like low-energy muons in the detector. A potential signal of staus would thus be an excess over muon tracks induced by atmospheric muon neutrinos. Our analysis focuses on the region around the horizon as here the ratio between stau signal and atmospheric background is largest. We will present the first sensitivity to constrain the stau mass using IceCube and demonstrate the potential of this analysis with future improvements

Klimt artwork: red-pigment material investigation by backscattering Fe-57 Mössbauer spectroscopy, SEM and p-XRF

Material tests were performed on a rediscovered Klimt-artwork “Trompetender Putto”. We performed studies on the red colored spots, mainly taken from non-restored parts. MIMOS II Fe-57 Mössbauer spectroscopy (novelty in art-pigment analysis) mainly reveals haematite and crystallized goethite in red colors. Electron microscopy can identify various layers of the original and overpainting of an artwork. The number of layers fluctuates between three and four chemically painted areas. The portable X-ray fluorescence analysis enables to reduce the pigment list to containing mercury (cinnabar), lead, zinc, iron and titanium. Infrared-light-irradiation visualizes the different age of the pigments

Material erosion, deposition and material transport in the stellarator W7-X

Material erosion, deposition and material transport in the stellaratorW7-XM. Mayera,*, M. Baldena, S. Brezinsekb, V.V. Burwitza,c, C.P. Dhardd, R. Guimarãese, M. Guitart Corominasa, P. Hireta, D. Naujoksd, R. Neua,c, J.H. Schmidt-Denckera, T.S. Silvae, and W7-X TeamaMax-Planck-Institut für Plasmaphysik, Garching, GermanybForschungszentrum Jülich GmbH, Jülich, GermanycTechnische Universität München, München,GermanydMax-Planck-Institut für Plasmaphysik, Greifswald, GermanyeUniversity of São Paulo, São Paulo, BrazilNet erosion, deposition and material transport in the stellarator W7-X were investigated on the Test Divertor Unit (TDU) using special carbon marker coatings and on the vessel walls by analysis of W-coated and regular wall elements duringthe operational phases OP1.2a in the year 2017 and OP1.2b in 2018. While OP1.2a was characterised by high concentrations of oxygen and carbon impuritiesin the plasmas, OP1.2b had much smaller impurity concentrations due to regular boronizations and showed considerably better plasma performances with higher plasma densities. First exposures of tungsten marker coatings in the TDU and at the inner heat shield were performed in OP1.2b. The samples were analysed by quantitative ion beam analysis methods, scanning electron microscopy, and laser-induced breakdown spectroscopy (LIBS).Very high net erosion of carbon was observed at the strike line of all 10 TDUs in both campaignsand is attributed to sputtering and chemical erosion by C and O impurities in OP1.2a[1], while the erosion was probably dominated by impact of H ions in OP1.2b. Re-deposition of carbon in remote areas of the TDU was small.Thicker re-deposited carbon layers with thicknesses of a few microns were observed at the divertor baffles,anoticeable deposition of boron on the TDU was observed after OP1.2b. The inner wall showed no erosion but net deposition of about 100 nm thick boron/carbon layersdue to the boronizations, the outer vessel wall showed a complicated pattern of small erosion areas and thin deposits. Stripes of boron/carbon layers were observed behind the gaps of inner wall protection tiles.The global carbon balance is currently unclear. However, carbon eroded from the TDU was not redeposited in the divertor region but was transported out of the divertor area. Some carbon was redeposited at the divertor baffles but was also pumped out as CO, CO2, or CH4. This is a profound difference to divertors in tokamaks, where eroded material is typically redeposited in remote divertor areas or in the inner divertor. A first assessment of tungsten as plasma-facing material in W7-X is provided.[1] M. Mayer et al., PFMC 2019, Phys. Scr., in press*Corresponding author:tel.: +49 89 3299 1639, e-mail: [email protected]

Assessment of erosion/deposition on the W7-X first-wall after completion of the first phase of divertor operation

Assessment of erosion/deposition on the W7-X first-wallafter completion of the first phase of divertor operationC. P. Dhard, M. Baldena, S. Brezinsekb, T. Dittmarb, P. Hireta, M. Mayera, S. Masuzakic, G. Motojimac,D. Naujoks, M. Rasinskib, N. Sandigd, J. H. Schmidt-Denckera, R. Yib, D. Zhaobandthe W7-X TeamMax-Planck-Institut für Plasmaphysik, Wendelsteinstrasse 1, 17491 Greifswald, GermanyaMax-Planck-Institut für Plasmaphysik, Boltzmannstrasse 2, 85748 Garching, GermanybForschungszentrum Jülich GmbH, Institut für Energie-und Klimaforschung-Plasmaphysik, Partner of the Trilateral Euregio Cluster (TEC), 52425 Jülich, Germanyc National Institute for Fusion Science, 322-6 Oroshi, Toki 509-5292, JapandFreie Universität Berlin, Kaiserswertherstrasse 16-18, 14195 Berlin, [email protected] first operationalphase of the stellarator Wendelstein 7-X (W7-X) was completed towards the end of 2018. This phase consisted of three plasma campaigns, the first withlimiterplasmas and the remaining two with tenTest Divertor Units(TDUs)and protectivetiles surrounding the plasma. All these were made of fine grain graphite.During these campaigns, the stored plasma energy was increased gradually up to 200 MJ.With ca.62 % area of the plasma-facing components covered with carbon and the rest with stainless steel, carbon-based impurities are expected to play a significant role for the plasma-wall interactions. In order to study these, a number of samples were installed in regions of the TDU with high particle-and power fluxes as well as onfirst wall components with comparatively lower heat loads. Since a large number of plasma-facing components were removed forinstallingthe actively cooled high heat flux divertorsmade of carbon-fiber compositesfor the next operation campaigns, this provided a good opportunity to study thesecomponents. This paper covers the erosion/deposition studies onselected samples exposed during whole campaigns.About2200 Ti-Zr-Mo screws,distributed uniformly along the toroidal and poloidal directions over the whole torus, were chosen for the measurements. Altogether ca.30 000 screws have been used to fix the graphite tiles on the cooling structures, the plasma-facingscrew heads were coated with carbonmarker layers to study erosion/depositionover every campaign. After the last campaign,the chosenscrews were removed and the marker layer thicknesses were measured using a betascope which contains a 147Pm beta-source and a Geiger-Müller counter and measures the thickness of thin layers by measuring the back-scattered beta particles. On the outboard side stainless steel wall panels,44 Si-wafer and other long-term probes were installed and the measurements wereperformed for the erosion/depositions in these lowly loaded areas. The results of thesemeasurements analyzed together with additionalmeasurements on the graphite tiles will be presented in the paper