ELECTROPHYSICAL INSTALLATION BASED ON BARRIER DISCHARGE FOR HYDROCARBON SYNTHESIS

In an electrophysical installation, a mixture of CH4 and C2H6 was treated by a barrier discharge. The hydrocarbon conversion was experimentally recorded. For the developed plasma chemical reactor, with help of the solver "ZDPlasKin", a theoretical evaluation of the plasma kinetics processes occurring in the discharge was carried out. The experimental results are in good agreement with the theoretical estimate.217-21

Воздействие наносекундных ультрафиолетовых лазерных импульсов на поверхность монокристаллов германия

For the first time, a detailed comprehensive study of the "dry" etching of dislocation and dislocation-free germanium samples on the {111}, {110} and {100} planes has been carried out. Etching was carried out by exposure to pulses of nanosecond UV laser radiation of subthreshold intensity (wavelength 355 nm, duration ~ 10 ns, energy density ~ 0.5–1.3 J/cm2, pulse repetition rate 100 Hz, divergence 1–2 mrad). Before and after laser heat treatment of the surface, the samples were examined using a Zygo optical profilometer and a scanning electron microscope. Features of the nature of damage to surfaces corresponding to different crystallographic planes of single crystals of industrial dislocation germanium are revealed. They are compared with data on subthreshold damages of typical dislocation-free crystals.It is shown that in dislocation samples of germanium on the {111} plane, it is possible to create a regime of exposure to radiation, leading to the formation of etch pits that are outwardly identical to dislocation pits detected during selective chemical etching. Their concentration corresponds in order of magnitude to the density of dislocations.On the {100} plane of dislocation samples, etching results were also found, which clearly have a crystallographic nature. At an energy density of the acting radiation ≥ 0.4 J/cm2, on the surfaces of dislocation ({100} plane) and dislocation-free germanium ({111}, {100}, {110} planes), only individual spots ~ 50 μm in size were registered, as well as individual microcraters ~ 0.1–1 μm in size, which do not have crystallographic features. The possibility of environmentally friendly detection of dislocations in germanium without the use of chemical reagents is shown.Впервые проведено подробное комплексное исследование «сухого» травления дислокационных и бездислокационных образцов германия на плоскостях {111}, {110}, {100}. Травление осуществляли путем воздействия импульсов наносекундного ультрафиолетового (УФ) лазерного излучения допороговой интенсивности (длина волны — 355 нм, длительность ~ 10 нс, плотность энергии ~ 0,5—1,3 Дж/см2, частота следования импульсов — 100 Гц, расходимость — 1—2 мрад). До и после лазерной термообработки поверхности образцы исследовали с помощью оптического профилометра Zygo и растрового электронного микроскопа. Выявлены особенности характера повреждения поверхностей, соответствующих различным кристаллографическим плоскостям монокристаллов промышленного дислокационного германия. Они сопоставлены с данными о допороговых повреждениях типовых бездислокационных кристаллов.Показано, что в дислокационных образцах германия на плоскости {111} возможно создание режима воздействия излучения, приводящего к формированию ямок травления, внешне идентичных дислокационным ямкам, выявляемым при селективном химическом травлении. Их концентрация по порядку величины соответствует плотности дислокаций.На плоскости {100} дислокационных образцов также обнаружены результаты травления, явно имеющие кристаллографическую природу. При плотности энергии воздействующего излучения ≥ 0,4 Дж/см2 на поверхностях дислокационного (плоскость {100}), и бездислокационного германия (плоскости {111}, {100}, {110}), были зарегистрированы лишь отдельные пятна размером ~ 50 мкм, а также отдельные микрократеры размером ~ 0,1—1 мкм, не имеющие кристаллографических признаков. Показана возможность экологичного выявления дислокаций в германии без использования химических реагентов

Модификация поверхности германия при воздействии излучения наносекундного ультрафиолетового лазера

Modification of the polished {111} surface of single-crystal germanium (n-type, resistivity 47 Ohm · cm), exposed to radiation of a focused frequency-pulse nanosecond ultraviolet Nd : YaG laser, was studied by optical profilometry, scanning electron and probe microscopy. It was revealed, that the threshold of plasma formation with generation of a crater on the surface, occurs at an energy density of E ~ 1.2—1.3 J/cm2. When the sample was stationary, at E ~ 0.1 J/cm2 irreversible damage to the surface occurred. When scanning the surface with radiation at E ~ 0.50—1.15 J/cm2, in the absence of noticeable traces of crater formation, the generation of etching pits with a regular triangular shape was observed, the concentration of which was (3—5) · 105 cm2. The figures resemble dislocation-etching pits, usually obtained by selective chemical etching.Dislocations were detected by ablation because of exposure to laser radiation. The centers of ablation nucleation are dislocations that come to the crystal surface. The transverse dimension of etching pits was ~ 5—10 µm and their overlap led to an alternating picture of trihedral pyramids, formed by the {111} planes. The presented images show the rounded edges and tops of the pyramids and the height of the profile of the figures ~ 1—2 μm. The linear dimensions of the pits testify a rapid flow of the process. Based on the total time of exposure to radiation on the surface ~ 200 ns, the rate of formation of flat faces in the pits equal to ~ 0.1—0.3 m/s, which is several orders of magnitude higher, than the rate of formation of the same faces during crystal growth was established. The depth of the surface layer, in which the structure was formed, was ~ 15 μm.Методами оптической профилометрии, сканирующей электронной и зондовой микроскопии исследована модификация полированной поверхности {111} монокристаллического германия (n-тип проводимости, удельное сопротивление 47 Ом · см) в результате воздействия сфокусированным частотно-импульсным излучением наносекундного ультрафиолетового Nd : YaG лазера. Выявлено, что порог плазмообразования с образованием кратера на поверхности возникает при плотности энергии лазерного излучения Е ~ 1,2÷1,3 Дж/см2. При неподвижном положении образца при Е ~ 0,1 Дж/см2 возникали необратимые повреждения поверхности. При сканировании поверхности излучением при Е ~ 0,50÷1,15 Дж/см2, в отсутствии заметных следов кратерообразования, наблюдалось образование ямок травления с правильной трехгранной формой, концентрация которых  составляла (3—5) ⋅ 105 см-2. Фигуры напоминают дислокационные ямки травления, получаемые селективным химическим травлением.Выявление дислокаций происходило путем абляции в результате воздействия лазерного излучения. Центрами зарождения абляции являются дислокации, выходящие на поверхность кристалла. Поперечный размер ямок травления  составил ~5—10 мкм, и их перекрытие привело к чередующейся картине трехгранных пирамид, образованных плоскостями {111}. Наблюдали скругленные грани и вершины пирамид, высота профиля фигур составила ∼1—2 мкм. Линейные размеры ямок свидетельствуют о быстром протекании процесса. Исходя из суммарного времени воздействия излучения на поверхность ∼200 нc установлена скорость формирования плоских граней в ямках, которая составляет ∼0,1—0,3 м/с, что на несколько порядков превышает скорость формирования таких же граней при росте кристалла. Глубина поверхностного слоя, в котором происходило формирование структуры, составляла ∼15 мкм

Single hadron response measurement and calorimeter jet energy scale uncertainty with the ATLAS detector at the LHC

The uncertainty on the calorimeter energy response to jets of particles is derived for the ATLAS experiment at the Large Hadron Collider (LHC). First, the calorimeter response to single isolated charged hadrons is measured and compared to the Monte Carlo simulation using proton-proton collisions at centre-of-mass energies of sqrt(s) = 900 GeV and 7 TeV collected during 2009 and 2010. Then, using the decay of K_s and Lambda particles, the calorimeter response to specific types of particles (positively and negatively charged pions, protons, and anti-protons) is measured and compared to the Monte Carlo predictions. Finally, the jet energy scale uncertainty is determined by propagating the response uncertainty for single charged and neutral particles to jets. The response uncertainty is 2-5% for central isolated hadrons and 1-3% for the final calorimeter jet energy scale.Comment: 24 pages plus author list (36 pages total), 23 figures, 1 table, submitted to European Physical Journal

Expected Performance of the ATLAS Experiment - Detector, Trigger and Physics

A detailed study is presented of the expected performance of the ATLAS detector. The reconstruction of tracks, leptons, photons, missing energy and jets is investigated, together with the performance of b-tagging and the trigger. The physics potential for a variety of interesting physics processes, within the Standard Model and beyond, is examined. The study comprises a series of notes based on simulations of the detector and physics processes, with particular emphasis given to the data expected from the first years of operation of the LHC at CERN

Hunt for new phenomena using large jet multiplicities and missing transverse momentum with ATLAS in 4.7 fb−1 of s√=7TeV proton-proton collisions

Results are presented of a search for new particles decaying to large numbers of jets in association with missing transverse momentum, using 4.7 fb−1 of pp collision data at s√=7TeV collected by the ATLAS experiment at the Large Hadron Collider in 2011. The event selection requires missing transverse momentum, no isolated electrons or muons, and from ≥6 to ≥9 jets. No evidence is found for physics beyond the Standard Model. The results are interpreted in the context of a MSUGRA/CMSSM supersymmetric model, where, for large universal scalar mass m 0, gluino masses smaller than 840 GeV are excluded at the 95% confidence level, extending previously published limits. Within a simplified model containing only a gluino octet and a neutralino, gluino masses smaller than 870 GeV are similarly excluded for neutralino masses below 100 GeV

Measurement of χ c1 and χ c2 production with s√ = 7 TeV pp collisions at ATLAS

The prompt and non-prompt production cross-sections for the χ c1 and χ c2 charmonium states are measured in pp collisions at s√ = 7 TeV with the ATLAS detector at the LHC using 4.5 fb−1 of integrated luminosity. The χ c states are reconstructed through the radiative decay χ c → J/ψγ (with J/ψ → μ + μ −) where photons are reconstructed from γ → e + e − conversions. The production rate of the χ c2 state relative to the χ c1 state is measured for prompt and non-prompt χ c as a function of J/ψ transverse momentum. The prompt χ c cross-sections are combined with existing measurements of prompt J/ψ production to derive the fraction of prompt J/ψ produced in feed-down from χ c decays. The fractions of χ c1 and χ c2 produced in b-hadron decays are also measured

Measurements of Higgs boson production and couplings in diboson final states with the ATLAS detector at the LHC

Measurements are presented of production properties and couplings of the recently discovered Higgs boson using the decays into boson pairs, H →γ γ, H → Z Z∗ →4l and H →W W∗ →lνlν. The results are based on the complete pp collision data sample recorded by the ATLAS experiment at the CERN Large Hadron Collider at centre-of-mass energies of √s = 7 TeV and √s = 8 TeV, corresponding to an integrated luminosity of about 25 fb−1. Evidence for Higgs boson production through vector-boson fusion is reported. Results of combined fits probing Higgs boson couplings to fermions and bosons, as well as anomalous contributions to loop-induced production and decay modes, are presented. All measurements are consistent with expectations for the Standard Model Higgs boson

Standalone vertex finding in the ATLAS muon spectrometer

A dedicated reconstruction algorithm to find decay vertices in the ATLAS muon spectrometer is presented. The algorithm searches the region just upstream of or inside the muon spectrometer volume for multi-particle vertices that originate from the decay of particles with long decay paths. The performance of the algorithm is evaluated using both a sample of simulated Higgs boson events, in which the Higgs boson decays to long-lived neutral particles that in turn decay to bbar b final states, and pp collision data at √s = 7 TeV collected with the ATLAS detector at the LHC during 2011

Measurement of the production of a W boson in association with a charm quark in pp collisions at √s = 7 TeV with the ATLAS detector

The production of a W boson in association with a single charm quark is studied using 4.6 fb−1 of pp collision data at s√ = 7 TeV collected with the ATLAS detector at the Large Hadron Collider. In events in which a W boson decays to an electron or muon, the charm quark is tagged either by its semileptonic decay to a muon or by the presence of a charmed meson. The integrated and differential cross sections as a function of the pseudorapidity of the lepton from the W-boson decay are measured. Results are compared to the predictions of next-to-leading-order QCD calculations obtained from various parton distribution function parameterisations. The ratio of the strange-to-down sea-quark distributions is determined to be 0.96+0.26−0.30 at Q 2 = 1.9 GeV2, which supports the hypothesis of an SU(3)-symmetric composition of the light-quark sea. Additionally, the cross-section ratio σ(W + +c¯¯)/σ(W − + c) is compared to the predictions obtained using parton distribution function parameterisations with different assumptions about the s−s¯¯¯ quark asymmetry