On the operation of a Micropattern Gaseous UV-Photomultiplier in Liquid-Xenon

Operation results are presented of a UV-sensitive gaseous photomultiplier (GPM) coupled through a MgF2 window to a liquid-xenon scintillator. It consisted of a reflective CsI photocathode deposited on top of a THick Gaseous Electron Multiplier (THGEM); further multiplication stages were either a second THGEM or a Parallel Ionization Multiplier (PIM) followed by a MICROMEsh GAseous Structure (MICROMEGAS). The GPM operated in gas-flow mode with non-condensable gas mixtures. Gains of 10^4 were measured with a CsI-coated double-THGEM detector in Ne/CH4 (95:5), Ne/CF4 (95:5) and Ne/CH4/CF4 (90:5:5), with soft X-rays at 173 K. Scintillation signals induced by alpha particles in liquid xenon were measured here for the first time with a double-THGEM GPM in He/CH4 (92.5:7.5) and a triple-structure THGEM/PIM/MICROMEGAS GPM in Ne/CH4 (90:10) with a fast-current preamplifier.Comment: 12 pages, 9 figures, submitted to JINS

The ALICE experiment at the CERN LHC

ALICE (A Large Ion Collider Experiment) is a general-purpose, heavy-ion detector at the CERN LHC which focuses on QCD, the strong-interaction sector of the Standard Model. It is designed to address the physics of strongly interacting matter and the quark-gluon plasma at extreme values of energy density and temperature in nucleus-nucleus collisions. Besides running with Pb ions, the physics programme includes collisions with lighter ions, lower energy running and dedicated proton-nucleus runs. ALICE will also take data with proton beams at the top LHC energy to collect reference data for the heavy-ion programme and to address several QCD topics for which ALICE is complementary to the other LHC detectors. The ALICE detector has been built by a collaboration including currently over 1000 physicists and engineers from 105 Institutes in 30 countries. Its overall dimensions are 161626 m3 with a total weight of approximately 10 000 t. The experiment consists of 18 different detector systems each with its own specific technology choice and design constraints, driven both by the physics requirements and the experimental conditions expected at LHC. The most stringent design constraint is to cope with the extreme particle multiplicity anticipated in central Pb-Pb collisions. The different subsystems were optimized to provide high-momentum resolution as well as excellent Particle Identification (PID) over a broad range in momentum, up to the highest multiplicities predicted for LHC. This will allow for comprehensive studies of hadrons, electrons, muons, and photons produced in the collision of heavy nuclei. Most detector systems are scheduled to be installed and ready for data taking by mid-2008 when the LHC is scheduled to start operation, with the exception of parts of the Photon Spectrometer (PHOS), Transition Radiation Detector (TRD) and Electro Magnetic Calorimeter (EMCal). These detectors will be completed for the high-luminosity ion run expected in 2010. This paper describes in detail the detector components as installed for the first data taking in the summer of 2008

Structural-Properties Of Amorphous Hydrogenated Carbon .3. NMR Investigations

Our NMR studies give experimental evidence of bonding heterogeneity in samples of a-C:H on the nanometer scale. Two classes of protons were identified with distinctly different spin-lattice-relaxation behavior. The difference in the spin-lattice relaxation provides a means of spectral editing of cross-polarization magic-angle spinning, combined rotation and multiple-pulse spectroscopy, dipolar dephasing spectra, and multiple quantum NMR experiments. This combination of the various NMR techniques allows for a detailed structural investigation of a-C:H, e.g., the sp2:sp3 ratio, the relative amount of hydrogenated and nonhydrogenated carbons, etc. A model incorporating the heterogeneity is established and discussed. The NMR results are compared with neutron spectroscopy and diffraction data

A potential novel rapid screening NMR approach to boundary film formation at solid interfaces in contact with ionic liquids

The boundary films generated oil a series of inorganic compounds, typical of native films oil metal and ceramic surfaces, when exposed to various ionic liquids (ILs) based oil the trihexyl(teti-adecyl)phosphonium cation have been characterized using multinuclear solid-state NMR. The NMR results indicate that SiO2 and Mg(OH)(2) interact strongly with the anion and cation of each IL through a mechanism of adsorption of the anion and subsequent close proximity of the cation in a surface double layer as observed through H-1-Si-29 cross polarization experiments). In contrast, Al2O3, MgO, ZnO, and ZrO2 appear less active, strongly suggesting the necessity of hydroxylated surface groups ill order to enhance the generation of these interfacial films. Using solid-state NMR to characterize Such interfaces not only has the potential to elucidate mechanisms of wear resistance and corrosion protection via iLs, but is also likely to allow their rapid screening for such durability applications