Radiation from an oscillator uniformly moving along the axis of a dielectric cylinder

The radiation generated by a charged longitudinal oscillator moving with a constant drift velocity along the axis of a dielectric cylinder immersed in a homogeneous medium is investigated. For an arbitrary oscillation law a formula is derived for the spectral-angular distribution of this radiation. Under the Cherenkov condition for the dielectric permittivity of the external medium and oscillator drift velocity this formula contains two summands. The first one corresponds to the radiation with a continuous spectrum which propagates at the Cherenkov angle of the external medium. The second one describes the radiation which has a discrete spectrum for a given angle of propagation. The corresponding frequencies are multiples of the Doppler-shifted oscillation frequency. The results of numerical calculations for the angular distribution of the radiated quanta are presented and they are compared with the corresponding quantities for the radiation in a homogeneous medium. It is shown that the presence of the cylinder can increase essentially the radiation intensity.Comment: 16 pages, 8 EPS figure

On features of the radiation from an electron moving along a helix inside a cylindrical hole in a homogeneous dielectric

The radiation from a charge moving along a helical trajectory inside a cylindrical hole in homogeneous dielectric medium is investigated. Prompted by availability of materials with large dielectric permittivity $\epsilon$ and small absorption, we discuss the features of this type of radiation for media with $\epsilon \gg 1$. It is shown that there are high peaks in the angular distribution of radiation intensity at well-defined harmonics. The conditions are specified for the cavity-to-helix radii ratio, $\rho_{1}/\rho_{0}$, under which the angle-integrated radiation intensity on some harmonics exceeds that in the empty space. Though the amplification of radiation intensity increases with increasing $\epsilon$, the corresponding "resonant" values of $\rho _{1}/\rho_{0}$ ratio are practically independent of the dielectric permittivity of surrounding medium. It is shown that an analogous amplification of radiation takes place essentially for the same values of $\rho_{1}/\rho_{0}$ also for the radiation in a cylindrical waveguide with conducting walls. An explanation of this phenomenon is given.Comment: 8 pages, 6 figures, talk presented at RREPS07, 24-28 September, 2007, Prague, Czech Republi

Экспериментальная модель для исследования биологически детерминированных взаимодействий в области контакта имплантат - костная ткань

Aim: a) to develop the method for surface modification of polytetrafluoroethylene (PTFE) by applying a nanostructured metallic or ceramic coating, b) to study the possibility of using this obtained structures with different coatings as an experimental model for analysis of the fine interactions in the contact implant-tissue zone. The study demonstrates that the surface modification of PTFE by magnetron sputtering of nano-Ti and Ti-Ca-P-C-O-N leads to increased integration potential of materials. Data obtained indicate that the designed constructions can be successfully used as an experimental model for studying the interactions of implant - tissue interface elements of periimplant area.В задачи работы входило: а) разработка метода модификации поверхности политетрафторэтилена (ПТФЭ) путем нанесения наноструктурного металлического или керамического покрытия; б) исследование возможности использования полученной таким образом конструкции с различными по составу покрытиями в качестве экспериментальной модели для исследования тонких взаимодействий в области контакта имплантат - тканевые элементы периимплантационной зоны. Исследование продемонстрировало, что модификация поверхности ПТФЭ путем магнетронного напыления нанопокрытий Ti и Ti-Ca-P-C-O-N приводит к повышению интеграционного потенциала материалов. Полученные результаты свидетельствуют о том, что разработанные конструкции могут быть с успехом использованы в качестве экспериментальной модели для изучения взаимодействий в области интерфейса имплантат - тканевые элементы периимплантационной зоны

Long-range Angular Correlations On The Near And Away Side In P-pb Collisions At √snn=5.02 Tev

7191/Mar294

Multiplicity dependence of inclusive J/psi production at midrapidity in pp collisions at root s=13 TeV

Measurements of the inclusive J/psi yield as a function of charged-particle pseudorapidity density dN(ch)/d eta in pp collisions at root s = 13 TeV with ALICE at the LHC are reported. The J/psi meson yield is measured at midrapidity (vertical bar y vertical bar <0.9) in the dielectron channel, for events selected based on the charged-particle multiplicity at midrapidity (vertical bar eta vertical bar <1) and at forward rapidity (-3.7 <eta <-1.7 and 2.8 <eta <5.1); both observables are normalized to their corresponding averages in minimum bias events. The increase of the normalized J/psi yield with normalized dN(ch)/d eta is significantly stronger than linear and dependent on the transverse momentum. The data are compared to theoretical predictions, which describe the observed trends well, albeit not always quantitatively. (C) 2020 European Organization for Nuclear Research. Published by Elsevier B.V.Peer reviewe

First measurement of Ωc0 production in pp collisions at s=13 TeV

The inclusive production of the charm–strange baryon 0 c is measured for the first time via its hadronic √ decay into −π+ at midrapidity (|y| &lt;0.5) in proton–proton (pp) collisions at the centre-of-mass energy s =13 TeV with the ALICE detector at the LHC. The transverse momentum (pT) differential cross section multiplied by the branching ratio is presented in the interval 2 &lt; pT &lt; 12 GeV/c. The pT dependence of the 0 c-baryon production relative to the prompt D0-meson and to the prompt 0 c-baryon production is compared to various models that take different hadronisation mechanisms into consideration. In the measured pT interval, the ratio of the pT-integrated cross sections of 0 c and prompt + c baryons multiplied by the −π+ branching ratio is found to be larger by a factor of about 20 with a significance of about 4σ when compared to e+e− collisions

Elliptic flow of charged particles at midrapidity relative to the spectator plane in Pb–Pb and Xe–Xe collisions

Measurements of the elliptic flow coefficient relative to the collision plane defined by the spectator neutrons v2{ SP} in collisions of Pb ions at center-of-mass energy per nucleon–nucleon pair √ 2.76 TeV and Xe ions at √ sNN = sNN =5.44 TeV are reported. The results are presented for charged particles produced at midrapidity as a function of centrality and transverse momentum for the 5–70% and 0.2–6 GeV/c ranges, respectively. The ratio between v2{ SP} and the elliptic flow coefficient relative to the participant plane v2{4}, estimated using four-particle correlations, deviates by up to 20% from unity depending on centrality. This observation differs strongly from the magnitude of the corresponding eccentricity ratios predicted by the TRENTo and the elliptic power models of initial state fluctuations that are tuned to describe the participant plane anisotropies. The differences can be interpreted as a decorrelation of the neutron spectator plane and the reaction plane because of fragmentation of the remnants from the colliding nuclei, which points to an incompleteness of current models describing the initial state fluctuations. A significant transverse momentum dependence of the ratio v2{ SP}/v2{4} is observed in all but the most central collisions, which may help to understand whether momentum anisotropies at low and intermediate transverse momentum have a common origin in initial state f luctuations. The ratios of v2{ SP} and v2{4} to the corresponding initial state eccentricities for Xe–Xe and Pb–Pb collisions at similar initial entropy density show a difference of (7.0 ±0.9)%with an additional variation of +1.8% when including RHIC data in the TRENTo parameter extraction. These observations provide new experimental constraints for viscous effects in the hydrodynamic modeling of the expanding quark–gluon plasma produced in heavy-ion collisions at the LHC

J/psi production as a function of charged-particle pseudorapidity density in p-Pb collisions at root s(NN)=5.02 TeV

We report measurements of the inclusive J/ψ yield and average transverse momentum as a function of charged-particle pseudorapidity density dNch/dη in p–Pb collisions at sNN=5.02TeV with ALICE at the LHC. The observables are normalised to their corresponding averages in non-single diffractive events. An increase of the normalised J/ψ yield with normalised dNch/dη, measured at mid-rapidity, is observed at mid-rapidity and backward rapidity. At forward rapidity, a saturation of the relative yield is observed for high charged-particle multiplicities. The normalised average transverse momentum at forward and backward rapidities increases with multiplicity at low multiplicities and saturates beyond moderate multiplicities. In addition, the forward-to-backward nuclear modification factor ratio is also reported, showing an increasing suppression of J/ψ production at forward rapidity with respect to backward rapidity for increasing charged-particle multiplicity

Travelling Wave Accelerating Structure for Areal 50 MeV Energy Upgrade

AREAL facility development implies energy upgrade to 50 MeV in order to drive a THz free electron laser. To reach this goal, the installation of two 1.6 m long S Band travelling wave accelerating sections, with nominal accelerating gradient of 15 MV m, are foreseen. In this paper the design study of accelerating sections along with the matching performance of RF couplers are presented. The simulations are performed using the CST Microwave Studio.The first results of the accelerating structure prototype fabrication are discusse