Search results for "PLASMA"
showing 10 items of 4043 documents
Effects of orbital occupancies on the neutrinoless beta-beta matrix element of 76Ge
2008
In this work we use the recently measured neutron occupancies in the 76Ge and 76Se nuclei as a guideline to define the neutron quasiparticle states in the 1p0f0g shell. We define the proton quasiparticles by inspecting the odd-mass nuclei adjacent to 76Ge and 76Se. We insert the resulting quasiparticles in a proton-neutron quasiparticle random-phase approximation (pnQRPA) calculation of the nuclear matrix element of the neutrinoless double beta (0-nu-beta-beta) decay of 76Ge. A realistic model space and effective microscopic two-nucleon interactions are used. We include the nucleon-nucleon short-range correlations and other relevant corrections at the nucleon level. It is found that the res…
Effects of orbital occupation on 0νββ nuclear matrix element
2009
We have used the recently measured neutron occupancies in the 76 Ge and 76 Se nuclei as a guideline to define the neutron quasiparticle states in the 1p0f0g shell. The adjacent odd-mass nuclei help define the corresponding proton quasiparticle states. We insert the obtained quasiparticles in a proton-neutron quasiparticle random-phase approximation (pnQRPA) calculation of the nuclear matrix element of the neutrinoless double beta (0 νββ ) decay of 76 Ge. It is found that the resulting value of the 0 νββ matrix element is not far from the recently reported shell-model result.
Low-level gamma-ray spectrometry for analysing fusion plasma conditions
2008
Abstract A new method, combining activation by neutrons and charged particles with ultra low-level gamma-ray spectrometry, aimed at obtaining a better understanding and more adequate measurements of MeV particle leaks in magnetic fusion devices was studied here. A total of 36 samples containing Ti, LiF, B 4 C and W were placed in a boron-nitride holder mounted on the ceiling of the JET Tokamak. The samples were activated by 63 pulses from a D– 3 He plasma and were later measured using underground gamma-ray spectrometry. The radionuclides 7 Be, 46 Sc, 54 Mn, 56 Co, 57 Co, 58 Co, 124 Sb, 181 Hf, 182 Ta, 181 W and 185 W were detected in several of the samples, with very low levels of activity …
Bunching and cooling of radioactive ions with REXTRAP
2002
The properties of radioactive ion beams produced by the present on-line target ion source technology are often not suitable for direct post acceleration. For that purpose pulsed and cooled beams of higher charged ions are required. In the case of REX-ISOLDE, the post accelerator at the CERN-ISOLDE radioactive beam facility, a unique system for beam preparation is used. It consists of a gas-filled cylindrical Penning trap (REXTRAP) for bunching and cooling followed by an electron beam ion source for charge state breeding. The Penning trap has been successfully operated with an efficiency of up to 40% and a total number of up to 107 ions stored. Buffer-gas sideband cooling at the ions’ cyclot…
Centrality dependence ofπ,K, andpproduction in Pb-Pb collisions atsNN=2.76TeV
2013
In this paper measurements are presented of pi(+/-), K-+/-, p, and (p) over bar production at midrapidity (vertical bar y vertical bar < 0.5), in Pb-Pb collisions at root s(NN) = 2.76 TeV as a function of centrality. The measurement covers the transverse-momentum (p(T)) range from 100, 200, and 300 MeV/c up to 3, 3, and 4.6 GeV/c for pi, K, and p, respectively. The measured p(T) distributions and yields are compared to expectations based on hydrodynamic, thermal and recombination models. The spectral shapes of central collisions show a stronger radial flow than measured at lower energies, which can be described in hydrodynamic models. In peripheral collisions, the p(T) distributions are not…
Focusing ions by viscous drag and weak electric fields in an ion guide
1991
Abstract A new special ion guide has one or more grids at low electric potential in the space between nozzle and skimmer. Viscous drag caused by helium flow is used together with weak electric fields for focusing ions through the skimmer. A typical yield through the skimmer is 75% of that through the nozzle. The focusing device is called a “squeezer”. Most properties of the “squeezer ion guide” are similar to those of an ordinary ion guide. Because the kinetic energies are only of the order of 10 eV, however, problems caused by ion scattering are greatly reduced as compared to ordinary ion guides.
Electrodynamic Characteristics of a Strip Antenna Located on a Plane Interface of a Resonant Magnetoplasma and an Isotropic Medium
2015
We study the electrodynamic characteristics of an antenna having the form of an infinitesimally thin, perfectly conducting narrow strip located on a plane interface of a resonant magnetoplasma and an isotropic medium. The antenna is perpendicular to an external magnetic field and is excited by a given voltage. Singular integral equations for the antenna current, on the basis of which the current distribution is found in the case of an infinitely long radiator, are obtained. The limits of applicability of an approximate method based on the transmission line theory for determining the current distribution and input impedance of the antenna are established. Within the framework of this method,…
Neutrino conversions in hot plasma
1995
We discuss the excitation of sterile neutrinos in the early universe using general quantum kinetic equations, which also incorporate a possible primordial magnetic field $B$. We find a new contribution to the excitation propability, which has its origin in the shrinkage of the spin vector. In the absence of $B$ nucleosynthesis implies the constraint $\mid \Delta m^2\mid\sin^22\theta_0\lsim 1.6\times 10^{-6}~{\rm eV}^2$ which is more restrictive than previous estimates. We also present examples of possible stringent limits for $B\ne 0$.
Thermodynamic consistency of the equation of state of strongly interacting matter
2004
Addressing strongly interacting matter in the region of energy density where the hadronic gas phase coexists with the quark-gluon plasma phase, we discuss how thermodynamic consistency can be used to constrain the equation of state for uniform matter and we illustrate the method by constructing a T{sub c}-dependent family of thermodynamically consistent equations of state based on simple spline interpolations between the gas and plasma phases.
Single-component plasma of photoelectrons
2007
Abstract Ten-nanosecond pulses of photoelectrons liberated by intense UV laser pulses from a thin gold layer are captured into a single-component plasma that is ideally suited to cool antiprotons ( p ¯ ) for antihydrogen ( H ¯ ) production. Up to a billion electrons are accumulated using a series of laser pulses, more than are needed for efficient p ¯ cooling in the large traps now being used for loading p ¯ for H ¯ production. The method is demonstrated within an enclosed vacuum space that is entirely at 4 K, and is thus compatible with the exceptional cryogenic vacuum that is desirable for the long-term storage of antihydrogen. The pitfalls of other electron accumulation methods are entir…