In the last 30 days

• Open/close LSO/LYSO Crystals for Future HEP Experiments

  Rihua Mao et al 2011 J. Phys.: Conf. Ser. 293 012004 Tag this article

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  Because of their high stopping power (X ₀ = 1.14 cm), fast (t = 40 ns) and bright (4 times of BGO) scintillation and good radiation hardness, cerium doped silicate based heavy crystal scintillators (LSO and LYSO) have attracted a broad interest in the high energy physics community pursuing precision electromagnetic calorimeter in severe radiation environment. We present in this paper current status of large size LSO and LYSO crystals adequate for HEP applications. The optical and scintillation properties and their radiation hardness are discussed.

• Open/close A Digital Calorimeter for Dark Matter Search in Space

  X L Sun et al 2011 J. Phys.: Conf. Ser. 293 012038 Tag this article

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  A novel digital imaging calorimeter is designed for the observation of high energy electrons and gamma rays on the Space Station of China. The MC data shows that the calorimeter has a capability of observing the electrons (without separation between e+ and e−) and the gamma-rays in 30GeV-5TeV with a high energy resolution of 4% over 500GeV, a good angular resolution of 0.5 degree over 500GeV, and a high proton rejection power of ~5×10 ⁵(95% signal efficiency). The calorimeter has a large geometrical factor of ~3.3 m ²sr (5 sensitive faces) with ~1T weight. The excellent energy resolution make us can detect any change of the energy spectra and a line signature in the energy distribution, as expected from the dark matter.

• Open/close Inflow length and tripping effects in turbulent boundary layers

  Ramis Örlü and Philipp Schlatter 2011 J. Phys.: Conf. Ser. 318 022018 Tag this article

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  A recent assessment of available direct numerical simulation (DNS) data from turbulent boundary layer flows [Schlatter & Örlü, J. Fluid Mech. 659, 116 (2010)] showed surprisingly large differences not only in the skin friction coefficient or shape factor, but also in their predictions of mean and fluctuation profiles far into the sublayer. For the present paper the DNS of a zero pressure-gradient turbulent boundary layer flow by Schlatter et al. [Phys. Fluids 21, 051702 (2009)] serving as the baseline simulation, was re-simulated, however with physically different inflow conditions and tripping effects. The downstream evolution of integral and global quantities as well as mean and fluctuation profiles are presented and results indicate that different inflow conditions and tripping effects explain most of the differences observed when comparing available DNS. It is also found, that if transition is initiated at a low enough Reynolds number (based on the momentum-loss thickness) Re _θ < 300, all data agree well for both inner and outer layer for Re _θ > 2000; a result that gives a lower limit for meaningful comparisons between numerical and/or wind tunnel experiments.

• Open/close Polymer chemistry and hydrogel systems

  E H Schacht 2004 J. Phys.: Conf. Ser. 3 22 Tag this article

  Article References Full text PDF (188 KB)

  Hydrogels are an interesting class of materials that can be prepared by a variety of methods. The properties of these materials depend on their building blocks and the preparation procedures and can be largely varied.

  Among the various classes of hydrogels, are the gels based of physically structuring biopolymers, like gelatine. By chemically modifying these biopolymers, hydrogels with a dual crosslinkage (physical and chemical) can be prepared.

  Hydrogels serve a broad range of applications, including biomaterials, matrices for drug delivery and scaffolds for tissue engineering.

• Open/close The High Dynamics Readout of PMT for BGO Calorimeter

  Yunlong Zhang et al 2011 J. Phys.: Conf. Ser. 293 012013 Tag this article

  Article References Full text PDF (835 KB)

  For one cell of BGO-EM energy deposition of electron/gamma with energy above TeV is between 0.5 MIPs and 10 ⁵ MIPs, the readout system need to cover this high dynamic range.

• Open/close How to use the cosmological Schwinger principle for energy flux, entropy, and "atoms of space–time" to create a thermodynamic space–time and multiverse

  Andrew Beckwith 2011 J. Phys.: Conf. Ser. 306 012064 Tag this article

  Article References Full text PDF (549 KB)

  We make explicit an idea by Padmanabhan in DICE 2010 [1], as to finding "atoms of space–time" permitting a thermodynamic treatment of emergent structure similar to Gibbs treatment of statistical physics. That is, an ensemble of gravitons is used to give an "atom" of space–time congruent with relic GW. The idea is to reduce the number of independent variables to get a simple emergent space–time structure of entropy. An electric field, based upon the cosmological Schwinger principle, is linked to relic heat flux, with entropy production tied in with candidates as to inflaton potentials. The effective electric field links with the Schwinger 1951s result of an E field leading to pairs of e ⁺e ⁻ charges nucleated in space–time volume V · t. Note that in most inflationary models, the assumption is for a magnetic field, not an electric field. An electric field permits a kink–anti-kink construction of an emergent structure, which includes Glinka's recent pioneering approach to a Multiverse. Also an E field allows for an emergent relic particle frequency range between one and 100 GHz. The novel contribution is a relic E field, instead of a B field, in relic space–time "atom" formation and vacuum nucleation of the same.

• Open/close The mysterious disappearance of Ettore Majorana

  Barry R Holstein 2009 J. Phys.: Conf. Ser. 173 012019 Tag this article

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  We review the short but interesting life of Ettore Majorana.

• Open/close Raman spectroscopy of hydrogen confined under extreme conditions

  N Subramanian et al 2010 J. Phys.: Conf. Ser. 215 012057 Tag this article

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  The challenge of confining hydrogen and its isotopes at high pressures and temperatures have hindered exploration of the predicted novel phases and their properties in static high P-T experiments. We have developed new methods to achieve good local confinement of hot, dense hydrogen that additionally protects the diamond anvils during the experiments. Raman spectra of such locally confined hydrogen and deuterium samples at high P-T conditions reveal interesting and rich features which include some that may be related to melting and some related to possible formation of species like metal hydrides and clathrates. These are discussed in the context of difficulties associated with establishing unambiguous diagnostics of melting of hydrogen, and thereby determination of the melting curve in laser and resistive heating diamond cell experiments at high pressures.

• Open/close A quantitative comparison between xen and kvm

  Andrea Chierici and Riccardo Veraldi 2010 J. Phys.: Conf. Ser. 219 042005 Tag this article

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  Virtualization is a proven software technology that is rapidly transforming the IT landscape and fundamentally changing the way that people compute. Recently all major software producers (e.g. Microsoft and RedHat) developed or acquired virtualization technologies. Our institute is a Tier1 for LHC experiments and is experiencing lots of benefits from virtualization technologies, like improving fault tolerance, providing efficient hardware resource usage and increasing security. Currently the virtualization solution adopted is xen, which is well supported by the Scientific Linux distribution, widely adopted by the HEP community. Since the HEP linux distribution is based on RedHat ES, we feel the need to investigate performance and usability differences with the new kvm technology recently acquired by RedHat. The case study of this work will be the LHCb experiment Tier2 site hosted at our institute, where all major grid elements run on xen virtual machines smoothly. We will investigate the impact on performance and stability that a migration to kvm would entail on the Tier2 site, as well as the effort required by a system administrator to deploy the migration. Several quantitative test results will be shown and explained in detail.

• Open/close Metallic hydrogen: The most powerful rocket fuel yet to exist

  Isaac F Silvera and John W Cole 2010 J. Phys.: Conf. Ser. 215 012194 Tag this article

  Article References Full text PDF (1.90 MB)

  Wigner and Huntington first predicted that pressures of order 25 GPa were required for the transition of solid molecular hydrogen to the atomic metallic phase. Later it was predicted that metallic hydrogen might be a metastable material so that it remains metallic when pressure is released. Experimental pressures achieved on hydrogen have been more than an order of magnitude higher than the predicted transition pressure and yet it remains an insulator. We discuss the applications of metastable metallic hydrogen to rocketry. Metastable metallic hydrogen would be a very light-weight, low volume, powerful rocket propellant. One of the characteristics of a propellant is its specific impulse, I _sp. Liquid (molecular) hydrogen-oxygen used in modern rockets has an Isp of ~460s; metallic hydrogen has a theoretical I _sp of 1700s! Detailed analysis shows that such a fuel would allow single-stage rockets to enter into orbit or carry economical payloads to the moon. If pure metallic hydrogen is used as a propellant, the reaction chamber temperature is calculated to be greater than 6000 K, too high for currently known rocket engine materials. By diluting metallic hydrogen with liquid hydrogen or water, the reaction temperature can be reduced, yet there is still a significant performance improvement for the diluted mixture.