Analysis of Fracture Behavior of Thin Polycrystalline Diamond Films

The effect of the substrate temperature and CH₄ concentrations on the fracture behavior of thin polycrystalline diamond films was systematically investigated by X-ray diffraction and scanning electron microscopy. The results show that the fracture behavior of thin polycrystalline diamond films synthesized by direct current plasma jet chemical vapor deposition is closely related to the substrate temperature and CH₄ concentrations. A high substrate temperature, due to difference in the thermal expansion coefficients of the substrate and the diamond film, causes thin polycrystalline diamond films to generate high residual stresses, which usually exceed fracture strength of thin diamond film and even that of diamond. The fracture toughness is found to drop with the increasing ratio of CH₄ concentration. In case of high CH₄ concentrations, various defects and impurities, such as cracks, microscopic holes, graphite, and amorphous carbon were observed in the films. Thus, the substrate temperature and CH₄ concentrations should be strictly controlled within an appropriate range.С помощью рентгеновской дифракции и сканирующей электронной микроскопии исследовано влияние температуры подложки и показателя концентрации CH₄ на поведение тонких поликристаллических алмазных пленок при разрушении. Показано, что поведение при разрушении тонких поликристаллических алмазных пленок, синтезированных химическим осаждением покрытия с помощью плазменной струи при постоянном токе, зависит от температуры подложки и показателя концентрации CH₄. Большая температура подложки приводит к возникновению высоких остаточных напряжений в тонких поликристаллических алмазных пленках вследствие различных значений коэффициента теплового расширения подложки и алмазной пленки, которые, как правило, оказываются выше значений сопротивления разрушению тонкой алмазной пленки и алмаза. Обнаружено, что вязкость разрушения уменьшается с увеличением показателя концентрации CH₄. По достижении высоких показателей концентрации CH₄ в тонких пленках образуются такие дефекты и примеси, как трещины, микроскопические отверстия, углерод в форме графита и аморфный углерод. Температуру подложки и показатель концентрации CH₄ необходимо контролировать в надлежащем диапазоне.За допомогою рентгенівської дифракції і скануючої електронної мікроскопії досліджено вплив температури підкладки і показника концентрації CH₄ на поведінку тонких полікристалічних алмазних плівок під час руйнування. Показано, що поведінка при руйнуванні тонких полікристалічних алмазних плівок, синтезованих хімічним осадженням покриття за допомогою плазмового струменя на основі постійного струму, залежить від температури підкладки і показника концентрації CH₄. Велика температура підкладки призводить до виникнення в тонких полікристалічних алмазних плівках високих залишкових напружень внаслідок різних значень коефіцієнта теплового розширення підкладки й алмазної плівки, які, як правило, вищі за значення опору руйнуванню тонкої алмазної плівки й алмаза. Виявлено, що в’язкість руйнування зменшується зі збільшенням показника концентрації CH₄. Після досягнення високих показників концентрації CH₄ у тонких плівках мають місце такі дефекти і домішки, як тріщини, макроскопічні отвори, вуглець у формі графіту і аморфний вуглець. Температуру підкладки і показник концентрації потрібно контролювати в необхідних межах

Study of wave propagation induced by sea dike breaching

In this paper, wave propagation induced by sea dike breaching is studied by physical model. Two sea dike layouts with seaside slope 1: 2 are applied. For layout A, inland area has the same elevations as the breach, and seaside water depth is 27.4cm. For layout B, inland area is 7cm lower than the breach, and seaside water depth is 34.4cm. Impacts of breach width, inland elevation, water depth and wave period on inundation area and overtopping discharge are carefully examined separately. Four breach widths, 5m, 10m, 15m and 20m, are selected. A series of irregular waves (JONSWAP ??=3.3) with mean wave periods 1.0s, 1.5s, 2.0s, and significant wave height 10 cm are applied at the offshore boundary for each layout. Several empirical formulas are proposed and indicate that change of inland area elevations affects the relationship among inundation area, overtopping discharge and breach width, wave propagation time and wave period. The correlation coefficient between calculated value and experimental data are very large, but some correlative value deviates a little from the ideal line, so in the future work, more factors should be considered, and the accuracy of the empirical formulas will be improved

Partonic flow and ϕ\phi-meson production in Au+Au collisions at sNN\sqrt{s_{NN}} = 200 GeV

We present first measurements of the $\phi$-meson elliptic flow ($v_{2}(p_{T})$) and high statistics $p_{T}$ distributions for different centralities from $\sqrt{s_{NN}}$ = 200 GeV Au+Au collisions at RHIC. In minimum bias collisions the $v_{2}$ of the $\phi$ meson is consistent with the trend observed for mesons. The ratio of the yields of the $\Omega$ to those of the $\phi$ as a function of transverse momentum is consistent with a model based on the recombination of thermal $s$ quarks up to $p_{T}\sim 4$ GeV/$c$, but disagrees at higher momenta. The nuclear modification factor ($R_{CP}$) of $\phi$ follows the trend observed in the $K^{0}_{S}$ mesons rather than in $\Lambda$ baryons, supporting baryon-meson scaling. Since $\phi$-mesons are made via coalescence of seemingly thermalized $s$ quarks in central Au+Au collisions, the observations imply hot and dense matter with partonic collectivity has been formed at RHIC.Comment: 6 pages, 4 figures, submit to PR

Plasma Wakefield Acceleration with a Modulated Proton Bunch

The plasma wakefield amplitudes which could be achieved via the modulation of a long proton bunch are investigated. We find that in the limit of long bunches compared to the plasma wavelength, the strength of the accelerating fields is directly proportional to the number of particles in the drive bunch and inversely proportional to the square of the transverse bunch size. The scaling laws were tested and verified in detailed simulations using parameters of existing proton accelerators, and large electric fields were achieved, reaching 1 GV/m for LHC bunches. Energy gains for test electrons beyond 6 TeV were found in this case.Comment: 9 pages, 7 figure

The energy dependence of ptp_t angular correlations inferred from mean-ptp_{t} fluctuation scale dependence in heavy ion collisions at the SPS and RHIC

We present the first study of the energy dependence of $p_t$ angular correlations inferred from event-wise mean transverse momentum fluctuations in heavy ion collisions. We compare our large-acceptance measurements at CM energies $\sqrt{s_{NN}} =$ 19.6, 62.4, 130 and 200 GeV to SPS measurements at 12.3 and 17.3 GeV. $p_t$ angular correlation structure suggests that the principal source of $p_t$ correlations and fluctuations is minijets (minimum-bias parton fragments). We observe a dramatic increase in correlations and fluctuations from SPS to RHIC energies, increasing linearly with $\ln \sqrt{s_{NN}}$ from the onset of observable jet-related fluctuations near 10 GeV.Comment: 10 pages, 4 figure

Measurement of Transverse Single-Spin Asymmetries for Di-Jet Production in Proton-Proton Collisions at s=200\sqrt{s} = 200 GeV

We report the first measurement of the opening angle distribution between pairs of jets produced in high-energy collisions of transversely polarized protons. The measurement probes (Sivers) correlations between the transverse spin orientation of a proton and the transverse momentum directions of its partons. With both beams polarized, the wide pseudorapidity ($-1 \leq \eta \leq +2$) coverage for jets permits separation of Sivers functions for the valence and sea regions. The resulting asymmetries are all consistent with zero and considerably smaller than Sivers effects observed in semi-inclusive deep inelastic scattering (SIDIS). We discuss theoretical attempts to reconcile the new results with the sizable transverse spin effects seen in SIDIS and forward hadron production in pp collisions.Comment: 6 pages total, 1 Latex file, 3 PS files with figure

Energy and system size dependence of \phi meson production in Cu+Cu and Au+Au collisions

We study the beam-energy and system-size dependence of \phi meson production (using the hadronic decay mode \phi -- K+K-) by comparing the new results from Cu+Cu collisions and previously reported Au+Au collisions at \sqrt{s_NN} = 62.4 and 200 GeV measured in the STAR experiment at RHIC. Data presented are from mid-rapidity (|y|<0.5) for 0.4 < pT < 5 GeV/c. At a given beam energy, the transverse momentum distributions for \phi mesons are observed to be similar in yield and shape for Cu+Cu and Au+Au colliding systems with similar average numbers of participating nucleons. The \phi meson yields in nucleus-nucleus collisions, normalised by the average number of participating nucleons, are found to be enhanced relative to those from p+p collisions with a different trend compared to strange baryons. The enhancement for \phi mesons is observed to be higher at \sqrt{s_NN} = 200 GeV compared to 62.4 GeV. These observations for the produced \phi(s\bar{s}) mesons clearly suggest that, at these collision energies, the source of enhancement of strange hadrons is related to the formation of a dense partonic medium in high energy nucleus-nucleus collisions and cannot be alone due to canonical suppression of their production in smaller systems.Comment: 20 pages and 5 figure

Longitudinal Double-Spin Asymmetry and Cross Section for Inclusive Jet Production in Polarized Proton Collisions at √s = 200 GeV

We report a measurement of the longitudinal double-spin asymmetry ALL and the differential cross section for inclusive midrapidity jet production in polarized proton collisions at √s=200  GeV. The cross section data cover transverse momenta

Two-particle correlations on transverse momentum and momentum dissipation in Au-Au collisions at sqrt(sNN) = 130 GeV

Measurements of two-particle correlations on transverse momentum pt for Au–Au collisions at GeV are presented. Significant large-momentum-scale correlations are observed for charged primary hadrons with 0.15 ≤ pt ≤ 2 GeV/c and pseudorapidity |η| ≤ 1.3. Such correlations were not observed in a similar study at lower energy and are not predicted by theoretical collision models. Their direct relation to mean-pt fluctuations measured in the same angular acceptance is demonstrated. Positive correlations are observed for pairs of particles which have large pt values while negative correlations occur for pairs in which one particle has large pt and the other has much lower pt. The correlation amplitudes per final state particle increase with collision centrality. The observed correlations are consistent with a scenario in which the transverse momentum of hadrons associated with initial-stage semi-hard parton scattering is dissipated by the medium to lower pt

The energy dependence of p\u3csub\u3et\u3c/sub\u3e angular correlations inferred from mean-p\u3csub\u3et\u3c/sub\u3e fluctuation scale dependence in heavy ion collisions at the SPS and RHIC

We present the first study of the energy dependence of pt angular correlations inferred from event-wise mean transverse momentum pt fluctuations in heavy ion collisions. We compare our large-acceptance measurements at CM energies , 62.4, 130 and 200 GeV to SPS measurements at 12.3 and 17.3 GeV. pt angular correlation structure suggests that the principal source of pt correlations and fluctuations is minijets (minimum-bias parton fragments). We observe a dramatic increase in correlations and fluctuations from SPS to RHIC energies, increasing linearly with from the onset of observable jet-related pt fluctuations near 10 GeV