228 research outputs found
Modeling of COMPASS tokamak divertor liquid metal experiments
Two small liquid metal targets based on the capillary porous structure were exposed to the divertor plasma of the tokamak COMPASS. The first target was wetted by pure lithium and the second one by a lithium-tin alloy, both releasing mainly lithium atoms (sputtering and evaporation) when exposed to plasma. Due to poorly conductive target material and steep surface inclination (implying the surface-perpendicular plasma heat flux 12-17 MW/m(2)) for 0.1-0.2 s, the LiSn target has reached 900 degrees C under ELMy H-mode. A model of heat conduction is developed and serves to evaluate the lithium sputtering and evaporation and, thus, the surface cooling by the released lithium and consequent radiative shielding. In these conditions, cooling of the surface by the latent heat of vapor did not exceed 1 MW/m(2). About 10(19) lithium atoms were evaporated (comparable to the COMPASS 1 m(3) plasma deuterium content), local Li pressure exceeded the deuterium plasma pressure. Since the radiating Li vapor cloud spreads over a sphere much larger than the hot spot, its cooling effect is negligible (0.2 MW/m(2)). We also predict zero lithium prompt redeposition, consistent with our observation.
Directional Sensitivity of the NEWSdm Experiment to Cosmic Ray Boosted Dark Matter
We present a study of a directional search for Dark Matter boosted forward
when scattered by cosmic-ray nuclei, using a module of the NEWSdm experiment.
The boosted Dark Matter flux at the edge of the Earth's atmosphere is expected
to be pointing to the Galactic Center, with a flux 15 to 20 times larger than
in the transverse direction.
The module of the NEWSdm experiment consists of a 10 kg stack of Nano Imaging
Trackers, i.e.~newly developed nuclear emulsions with AgBr crystal sizes down
to a few tens of nanometers. The module is installed on an equatorial
telescope. The relatively long recoil tracks induced by boosted Dark Matter,
combined with the nanometric granularity of the emulsion, result in an
extremely low background. This makes an installation at the INFN Gran Sasso
laboratory, both on the surface and underground, viable. A comparison between
the two locations is made. The angular distribution of nuclear recoils induced
by boosted Dark Matter in the emulsion films at the surface laboratory is
expected to show an excess with a factor of 3.5 in the direction of the
Galactic Center. This excess allows for a Dark Matter search with directional
sensitivity. The surface laboratory configuration prevents the deterioration of
the signal in the rock overburden and it emerges as the most powerful approach
for a directional observation of boosted Dark Matter with high sensitivity. We
show that, with this approach, a 10 kg module of the NEWSdm experiment exposed
for one year at the Gran Sasso surface laboratory can probe Dark Matter masses
between 1 keV/c and 1 GeV/c and cross-section values down to
~cm with a directional sensitive search.Comment: 15 pages, 14 figures, updated references, clarified discussion in
intro section. Submitted to JCA
Phenotypic and Functional Changes in Blood Monocytes Following Adherence to Endothelium
Blood monocytes are known to express endothelial-like genes during co-culture with endothelium. In this study, the time-dependent change in the phenotype pattern of primary blood monocytes after adhering to endothelium is reported using a novel HLA-A2 mistyped co-culture model.Freshly isolated human PBMCs were co-cultured with human umbilical vein endothelial cells or human coronary arterial endothelial cells of converse human leukocyte antigen A2 (HLA-A2) status. This allows the tracking of the PBMC-derived cells by HLA-A2 expression and assessment of their phenotype pattern over time. PBMCs that adhered to the endothelium at the start of the co-culture were predominantly CD11b+ blood monocytes. After 24 to 72 hours in co-culture, the endothelium-adherent monocytes acquired endothelial-like properties including the expression of endothelial nitric oxide synthase, CD105, CD144 and vascular endothelial growth factor receptor 2. The expression of monocyte/macrophage lineage antigens CD14, CD11b and CD36 were down regulated concomitantly. The adherent monocytes did not express CD115 after 1 day of co-culture. By day 6, the monocyte-derived cells expressed vascular cell adhesion molecule 1 in response to tumour necrosis factor alpha. Up to 10% of the PBMCs adhered to the endothelium. These monocyte-derived cells contributed up to 30% of the co-cultured cell layer and this was dose-dependent on the PBMC seeding density.Human blood monocytes undergo rapid phenotype change to resemble endothelial cells after adhering to endothelium
NEWSdm Collaboration
Direct Dark Matter searches are nowadays one of the most fervid research topics with many experimental efforts devoted to the search for nuclear recoils induced by the scattering of Weakly Interactive Massive Particles (WIMPs). Detectors able to reconstruct the direction of the nucleus recoiling against the scattering WIMP are opening a new frontier to possibly extend Dark Matter searches beyond the neutrino background. Exploiting directionality would also prove the galactic origin of Dark Matter with an unambiguous signal-to-background separation. Indeed, the angular distribution of recoiled nuclei is centered around the direction of the Cygnus constellation, while the background distribution is expected to be isotropic. Current directional experiments are based on gas TPC whose sensitivity is limited by the small achievable detector mass. In this paper we present the discovery potential of a directional experiment based on the use of a solid target made of newly developed nuclear emulsions and of optical read-out systems reaching unprecedented nanometric resolution
Measurement of the cosmic ray muon flux seasonal variation with the OPERA detector
The OPERA experiment discovered muon neutrino into tau neutrino oscillations in appearance mode, detecting tau leptons by means of nuclear emulsion films. The apparatus was also endowed with electronic detectors with tracking capability, such as scintillator strips and resistive plate chambers. Because of its location in the underground Gran Sasso laboratory, under 3800 m.w.e., the OPERA detector has also been used as an observatory for TeV muons produced by cosmic rays in the atmosphere. In this paper the measurement of the single muon flux modulation and its correlation with the seasonal cycle of atmospheric temperature is reported
More results from the OPERA experiment
The OPERA experiment reached its main goal by proving the appearance of vτ in the CNGS vμ beam. Five vτ candidates were detected with a S/B ratio of ∼ 10, allowing to reject the null hypothesis at 5.1σ. The search has been extended by loosening the selection criteria in order to improve the statistical uncertainty. One of the vτ candidates selected with the new strategy shows a double vertex topology and, after a dedicated multivariate analysis, is compatible with being a vTτ interaction with charm production. Based on the enlarged data sample the estimation of Δm223 in appearance mode is being performed. The search for ve interactions has been extended over the full data set with a more than twofold increase in statistics: data are compatible with the non-oscillation hypothesis in the three-flavour mixing model. The implications of the electron neutrino sample in the framework of the 3+1 sterile mode will lead to exclusion limits on sin2 2θμe. Finally, the analysis of the annual modulation of cosmic muons is introduced
Updated constraints on sterile neutrino mixing in the OPERA experiment using a new identification method
This paper describes a new identification method specifically
designed to improve the low-energy ()
identification efficiency attained by enlarging the emulsion film scanning
volume with the next generation emulsion readout system. A relative increase of
25-70% in the low-energy region is expected, leading to improvements in
the OPERA sensitivity to neutrino oscillations in the framework of the 3 + 1
model. The method is applied to a subset of data where the detection efficiency
increase is expected to be more relevant, and one additional candidate
is found. The analysis combined with the appearance results improves
the upper limit on to 0.016 at 90% C.L. in the
MiniBooNE allowed region .Comment: 12 pages, 6 figure
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