Nebulization reflux concentrator

A nebulization reflux concentrator for removing trace gas contaminants from a sample gas is described. Sample gas from a gas supply is drawn by a suction source into a vessel. The gas enters the vessel through an atomizing nozzle, thereby atomizing and entraining a scrubbing liquid solvent drawn through a siphon tube from a scrubbing liquid reservoir. The gas and entrained liquid rise through a concentrator and impinge upon a solvent phobic filter, whereby purified gas exits through the filter housing and contaminated liquid coalesces on the solvent phobic filter and falls into the reservoir

QCD Factorization for Semi-Inclusive Deep-Inelastic Scattering at Low Transverse Momentum

We demonstrate a factorization formula for semi-inclusive deep-inelastic scattering with hadrons in the current fragmentation region detected at low transverse momentum. To facilitate the factorization, we introduce the transverse-momentum dependent parton distributions and fragmentation functions with gauge links slightly off the light-cone, and with soft-gluon radiations subtracted. We verify the factorization to one-loop order in perturbative quantum chromodynamics and argue that it is valid to all orders in perturbation theory.Comment: 28 pages, figures include

Hard-scattering factorization with heavy quarks: A general treatment

A detailed proof of hard scattering factorization is given with the inclusion of heavy quark masses. Although the proof is explicitly given for deep-inelastic scattering, the methods apply more generally The power-suppressed corrections to the factorization formula are uniformly suppressed by a power of \Lambda/Q, independently of the size of heavy quark masses, M, relative to Q.Comment: 52 pages. Version as published plus correction of misprint in Eq. (45

VUV photoemission studies of candidate Large Hadron Collider vacuum chamber materials

In the context of future accelerators and, in particular, the beam vacuum of the Large Hadron Collider (LHC), a 27 km circumference proton collider to be built at CERN, VUV synchrotron radiation (SR) has been used to study both qualitatively and quantitatively candidate vacuum chamber materials. Emphasis is given to show that angle and energy resolved photoemission is an extremely powerful tool to address important issues relevant to the LHC, such as the emission of electrons that contributes to the creation of an electron cloud which may cause serious beam instabilities and unmanageable heat loads on the cryogenic system. Here we present not only the measured photoelectron yields from the proposed materials, prepared on an industrial scale, but also the energy and in some cases the angular dependence of the emitted electrons when excited with either a white light (WL) spectrum, simulating that in the arcs of the LHC, or monochromatic light in the photon energy range of interest. The effects on the materials examined of WL irradiation and /or ion sputtering, simulating the SR and ion bombardment expected in the LHC, were investigated. The studied samples exhibited significant modifications, in terms of electron emission, when exposed to the WL spectrum from the BESSY Toroidal Grating Monochromator beam line. Moreover, annealing and ion bombardment also induce substantial changes to the surface thereby indicating that such surfaces would not have a constant electron emission during machine operation. Such characteristics may be an important issue to define the surface properties of the LHC vacuum chamber material and are presented in detail for the various samples analyzed. It should be noted that all the measurements presented here were recorded at room temperature, whereas the majority of the LHC vacuum system will be maintained at temperatures below 20 K. The results cannot therefore be directly applied to these sections of the machine until measurements at cryogenic temperatures, i.e., in the presence of cryosorbed gas layers, are obtained. However, these results are directly relevant to all the warm regions of the LHC vacuum system, such as the experimental vacuum chambers and warm element vacuum chambers in the insertion regions

VUV photoemission studies of candidate LHC vacuum chamber materials

In the context of future accelerators and, in particular, the beam vacuum of the LargeHadron Collider (LHC), a 27 km circumference proton collider to be built at CERN, VUVsynchrotron radiation (SR) has been used to study both qualitatively and quantitatively candidatevacuum chamber materials. Emphasis is given to show that angle and energy resolvedphotoemission is an extremely powerful tool to address important issues relevant to the LHC, suchas the emission of electrons that contribute to the creation of an electron cloud which may causeserious beam instabilities. Here we present not only the measured photoelectron yields (PY)from the proposed materials, prepared on an industrial scale, but also the energy and, in some cases,the angular dependence of the emitted electrons when excited with either a white light (WL)spectrum, simulating that in the arcs of the LHC or monochromatic light in the photon energy rangeof interest. The effects on the materials examined of WL irradiation and/or ion sputtering,simulating the SR and ion bombardment expected in the LHC, were investigated. The studiedsamples exhibited significant modifications, in terms of electron emission, when exposed to the WLspectrum from the BESSY TGM7 beamline. Moreover, annealing and ion bombardment alsoinduce substantial changes to the surface thereby indicating that such surfaces would not have aconstant electron emission during machine operation. Such characteristics may be an importantissue to define the surface properties of the LHC vacuum chamber material and are presented indetail for the various samples analysed

Homoclinic Signatures of Dynamical Localization

It is demonstrated that the oscillations in the width of the momentum distribution of atoms moving in a phase-modulated standing light field, as a function of the modulation amplitude, are correlated with the variation of the chaotic layer width in energy of an underlying effective pendulum. The maximum effect of dynamical localization and the nearly perfect delocalization are associated with the maxima and minima, respectively, of the chaotic layer width. It is also demonstrated that kinetic energy is conserved as an almost adiabatic invariant at the minima of the chaotic layer width, and that the system is accurately described by delta-kicked rotors at the zeros of the Bessel functions J_0 and J_1. Numerical calculations of kinetic energy and Lyapunov exponents confirm all the theoretical predictions.Comment: 7 pages, 4 figures, enlarged versio

Fully Unintegrated Parton Correlation Functions and Factorization in Lowest Order Hard Scattering

Motivated by the need to correct the potentially large kinematic errors in approximations used in the standard formulation of perturbative QCD, we reformulate deeply inelastic lepton-proton scattering in terms of gauge invariant, universal parton correlation functions which depend on all components of parton four-momentum. Currently, different hard QCD processes are described by very different perturbative formalisms, each relying on its own set of kinematical approximations. In this paper we show how to set up formalism that avoids approximations on final-state momenta, and thus has a very general domain of applicability. The use of exact kinematics introduces a number of significant conceptual shifts already at leading order, and tightly constrains the formalism. We show how to define parton correlation functions that generalize the concepts of parton density, fragmentation function, and soft factor. After setting up a general subtraction formalism, we obtain a factorization theorem. To avoid complications with Ward identities the full derivation is restricted to abelian gauge theories; even so the resulting structure is highly suggestive of a similar treatment for non-abelian gauge theories.Comment: 44 pages, 69 figures typos fixed, clarifications and second appendix adde