DLC deposition by PECVD at plasma cathode based low-pressure discharge

The characteristics of coatings prepared by acetylene decomposition in nonself-sustained discharge with a plasma cathode have been studied. The initial energy of electrons injected into the plasma was 0,1 – 0,7 keV, energy of ions bombarding the coating was 0,1 – 0,7 keV and the pressure of Ar + C2H2 gas mixture was 0,2 – 1 Pa. Microhardness and wear resistance of coatings were measured by methods of kinetic indentation and ball abrasion. The coatings with high microhardness (40 – 60 GPa) and high wear resistance were deposited on conditions that ion energy exceeded 300 eV. It was shown that coating’s microhardness and internal stresses in the coatings deposited on chamber walls could be reduced by concerted change of voltage accelerating injected electrons and bias voltage applied to samples placed into the plasma. This allows to avoid delamination of coating particles from the walls and to provide high quality coating on samples. When you are citing the document, use the following link http://essuir.sumdu.edu.ua/handle/123456789/2076

Effect of ion flux parameters on the rate of austenitic stainless steel nitriding in electron beam generated plasma

Nitriding of metals in electron beam generated plasma provides change of ion current density j and ion energy E over a wide range, the constant temperature of a sample being sustained by change of electron beam parameters. Broad (100 cm2) electron beam (5-20 A, 60-500 eV) was generated by electron source with a plasma cathode. 12X18 10 stainless steel was nitrided at 500 during 1 h. Dependences of nitriding layer thickness on j (1,6-6,2 m/cm2), E (100-300 eV), pressure of Ar-N2 gas mixture (1-10 Pa) were obtained. Nitrided layer thickness was measured in cross-sections with the use of microhardness meter and SEM micropictures. The layer thickness decreases with the rate 4-5 microns per 100 eV with E growth and rises from 19 up to 33 microns with j increase. Character of nitriding rate dependence on j contradicts conclusions of the theory concerning restriction of the layer thickness by ion sputtering with j growth. The value of effective diffusion coefficient is an order of magnitude higher than the one known from literary data. When you are citing the document, use the following link http://essuir.sumdu.edu.ua/handle/123456789/2084

178 MHz cavity with HOM damping for the DFELL storage ring

Design of the new cavity produced for the DUKE FELL storage ring is presented. The fundamental and higher order modes (HOMs) parameters are shown. The HOMs are substantially damped in a special load with absorbers made of conductive ceramics. Experimental studies of the absorbing material properties were carried out on models. The results are described. The cavity cold measurements results are presented as well.Представлено конструкцію, параметри, і результати розрахунку спектра вищих мод резонатора, виготовленого для накопичувального кільця лазера на вільних електронах в університеті ДЮКЕ (США). У цьому резонаторі вищі моди сильно подавлені за допомогою спеціального навантаження, що використовує провідну кераміку. Описано результати досліджень властивостей поглинаючого матеріалу, проведених на макеті. Приведено результати холодних вимірів резонатора і його іспитів на високому рівні потужності.Представлена конструкция, параметры и результаты расчета спектра высших мод резонатора, изготовляемого для накопительного кольца лазера на свободных электронах в университете ДЮКЕ (США). В этом резонаторе высшие моды сильно подавлены с помощью специальной нагрузки, использующей проводящую керамику. Описаны результаты исследований свойств поглощающего материала, проведенных на макете. Приведены результаты холодных измерений резонатора и его испытаний на высоком уровне мощности

Search for a W' boson decaying to a bottom quark and a top quark in pp collisions at sqrt(s) = 7 TeV

Results are presented from a search for a W' boson using a dataset corresponding to 5.0 inverse femtobarns of integrated luminosity collected during 2011 by the CMS experiment at the LHC in pp collisions at sqrt(s)=7 TeV. The W' boson is modeled as a heavy W boson, but different scenarios for the couplings to fermions are considered, involving both left-handed and right-handed chiral projections of the fermions, as well as an arbitrary mixture of the two. The search is performed in the decay channel W' to t b, leading to a final state signature with a single lepton (e, mu), missing transverse energy, and jets, at least one of which is tagged as a b-jet. A W' boson that couples to fermions with the same coupling constant as the W, but to the right-handed rather than left-handed chiral projections, is excluded for masses below 1.85 TeV at the 95% confidence level. For the first time using LHC data, constraints on the W' gauge coupling for a set of left- and right-handed coupling combinations have been placed. These results represent a significant improvement over previously published limits.Comment: Submitted to Physics Letters B. Replaced with version publishe

Search for the standard model Higgs boson decaying into two photons in pp collisions at sqrt(s)=7 TeV

A search for a Higgs boson decaying into two photons is described. The analysis is performed using a dataset recorded by the CMS experiment at the LHC from pp collisions at a centre-of-mass energy of 7 TeV, which corresponds to an integrated luminosity of 4.8 inverse femtobarns. Limits are set on the cross section of the standard model Higgs boson decaying to two photons. The expected exclusion limit at 95% confidence level is between 1.4 and 2.4 times the standard model cross section in the mass range between 110 and 150 GeV. The analysis of the data excludes, at 95% confidence level, the standard model Higgs boson decaying into two photons in the mass range 128 to 132 GeV. The largest excess of events above the expected standard model background is observed for a Higgs boson mass hypothesis of 124 GeV with a local significance of 3.1 sigma. The global significance of observing an excess with a local significance greater than 3.1 sigma anywhere in the search range 110-150 GeV is estimated to be 1.8 sigma. More data are required to ascertain the origin of this excess.Comment: Submitted to Physics Letters

Measurement of the Lambda(b) cross section and the anti-Lambda(b) to Lambda(b) ratio with Lambda(b) to J/Psi Lambda decays in pp collisions at sqrt(s) = 7 TeV

The Lambda(b) differential production cross section and the cross section ratio anti-Lambda(b)/Lambda(b) are measured as functions of transverse momentum pt(Lambda(b)) and rapidity abs(y(Lambda(b))) in pp collisions at sqrt(s) = 7 TeV using data collected by the CMS experiment at the LHC. The measurements are based on Lambda(b) decays reconstructed in the exclusive final state J/Psi Lambda, with the subsequent decays J/Psi to an opposite-sign muon pair and Lambda to proton pion, using a data sample corresponding to an integrated luminosity of 1.9 inverse femtobarns. The product of the cross section times the branching ratio for Lambda(b) to J/Psi Lambda versus pt(Lambda(b)) falls faster than that of b mesons. The measured value of the cross section times the branching ratio for pt(Lambda(b)) > 10 GeV and abs(y(Lambda(b))) < 2.0 is 1.06 +/- 0.06 +/- 0.12 nb, and the integrated cross section ratio for anti-Lambda(b)/Lambda(b) is 1.02 +/- 0.07 +/- 0.09, where the uncertainties are statistical and systematic, respectively.Comment: Submitted to Physics Letters

Search for new physics in events with opposite-sign leptons, jets, and missing transverse energy in pp collisions at sqrt(s) = 7 TeV

A search is presented for physics beyond the standard model (BSM) in final states with a pair of opposite-sign isolated leptons accompanied by jets and missing transverse energy. The search uses LHC data recorded at a center-of-mass energy sqrt(s) = 7 TeV with the CMS detector, corresponding to an integrated luminosity of approximately 5 inverse femtobarns. Two complementary search strategies are employed. The first probes models with a specific dilepton production mechanism that leads to a characteristic kinematic edge in the dilepton mass distribution. The second strategy probes models of dilepton production with heavy, colored objects that decay to final states including invisible particles, leading to very large hadronic activity and missing transverse energy. No evidence for an event yield in excess of the standard model expectations is found. Upper limits on the BSM contributions to the signal regions are deduced from the results, which are used to exclude a region of the parameter space of the constrained minimal supersymmetric extension of the standard model. Additional information related to detector efficiencies and response is provided to allow testing specific models of BSM physics not considered in this paper.Comment: Replaced with published version. Added journal reference and DO

Measurement of isolated photon production in pp and PbPb collisions at sqrt(sNN) = 2.76 TeV

Isolated photon production is measured in proton-proton and lead-lead collisions at nucleon-nucleon centre-of-mass energies of 2.76 TeV in the pseudorapidity range |eta|<1.44 and transverse energies ET between 20 and 80 GeV with the CMS detector at the LHC. The measured ET spectra are found to be in good agreement with next-to-leading-order perturbative QCD predictions. The ratio of PbPb to pp isolated photon ET-differential yields, scaled by the number of incoherent nucleon-nucleon collisions, is consistent with unity for all PbPb reaction centralities.Comment: Submitted to Physics Letters

Search for leptophobic Z ' bosons decaying into four-lepton final states in proton-proton collisions at root s=8 TeV

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Search for black holes and other new phenomena in high-multiplicity final states in proton-proton collisions at root s=13 TeV

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