On completeness of description of an equilibrium canonical ensemble by reduced s-particle distribution function

In this article it is shown that in a classical equilibrium canonical ensemble of molecules with $s$-body interaction full Gibbs distribution can be uniquely expressed in terms of a reduced s-particle distribution function. This means that whenever a number of particles $N$ and a volume $V$ are fixed the reduced $s$-particle distribution function contains as much information about the equilibrium system as the whole canonical Gibbs distribution. The latter is represented as an absolutely convergent power series relative to the reduced $s$-particle distribution function. As an example a linear term of this expansion is calculated. It is also shown that reduced distribution functions of order less than $s$ don't possess such property and, to all appearance, contain not all information about the system under consideration.Comment: This work was reported on the International conference on statistical physics "SigmaPhi2008", Crete, Greece, 14-19 July 200

РАССЕЯНИЕ ФЛУОРЕСЦЕНТНОГО РЕНТГЕНОВСКОГО ИЗЛУЧЕНИЯ В ВЕЩЕСТВЕ

During the study the X-ray K-spectra of the elements of the middle of periodic system in the media with the small effective atomic numbers on the energy-dispersion spectrometer with the semiconductor detector, experimentally discovered the previously not noted in the scientific publications appearance of peaks of incoherently scattered radiation Kα-lines of the elements of sample. These peaks, which are practically absent for Co, grow for the more heavy elements. Their intensities reach, for example for Ka line of Sn, to 10-15% of the intensity of fluorescent peak. In contrast to the peaks of incoherently scattered radiation of the characteristic anode emission of X-ray tubes, these peaks adjoin close to the fluorescent peak, forming the continuous region of incoherent scattering. This is caused by the broad band of scattering angles (from 0 to 180o). Appearance in the spectra of the peaks of the incoherently scattered characteristic lines of the elements of the sample leads to the need for their account because of the possibility of their superposition on the characteristic lines of other elements. Furthermore, the appearance of the incoherently scattered lines leads to the decrease of the intensities of the corresponding fluorescent lines.Keywords: x-ray spectrometer, semiconductor detector, incoherent dispersion of fluorescent radiation.(Russian)DOI: http://dx.doi.org/10.15826/analitika.2013.17.4.002B.D. Kalinin, R.I. Plotnikov “Pretsizion Tekhnologies” Co. Lt., St. Petersburg, Russian Federation При изучении рентгеновских К-спектров элементов середины периодической системы в материалах с малыми эффективными атомными номерами на энергодисперсионном спектрометре с полупроводниковым детектором, экспериментально обнаружено ранее не отмеченное в научных публикациях появление пиков некогерентно рассеянного излучения Kα-линий элементов образца. Эти пики, практически отсутствующие у Co, возрастают для более тяжелых элементов. Их интенсивность доходит, например для Ka-линии Sn, до 10-15 % от интенсивности флуоресцентного пика. В отличие от пиков некогерентно рассеянного излучения характеристического излучения анодов рентгеновских трубок, эти пики вплотную примыкают к флуоресцентному пику, образуя непрерывную область некогерентного рассеяния. Это обусловлено широким диапазоном углов рассеяния (от 0 до 180o). Появление в спектрах пиков некогерентно рассеянных характеристических линий элементов образца ведет к необходимости их учета из-за возможности их наложения на характеристические линии других элементов. Кроме того, появление некогерентно рассеянных линий ведет к уменьшению интенсивностей соответствующих флуоресцентных линий.Ключевые слова: рентгеновский спектрометр, полупроводниковый детектор, некогерентное рассеяние флуоресцентного излучения.DOI: http://dx.doi.org/10.15826/analitika.2013.17.4.00

Experimental and Theoretical Investigation into the Effect of the Electron Velocity Distribution on Chaotic Oscillations in an Electron Beam under Virtual Cathode Formation Conditions

The effect of the electron transverse and longitudinal velocity spread at the entrance to the interaction space on wide-band chaotic oscillations in intense multiple-velocity beams is studied theoretically and numerically under the conditions of formation of a virtual cathode. It is found that an increase in the electron velocity spread causes chaotization of virtual cathode oscillations. An insight into physical processes taking place in a virtual cathode multiple velocity beam is gained by numerical simulation. The chaotization of the oscillations is shown to be associated with additional electron structures, which were separated out by constructing charged particle distribution functions.Comment: 9 pages, 8 figure

Crab cavities for linear colliders

Crab cavities have been proposed for a wide number of accelerators and interest in crab cavities has recently increased after the successful operation of a pair of crab cavities in KEK-B. In particular crab cavities are required for both the ILC and CLIC linear colliders for bunch alignment. Consideration of bunch structure and size constraints favour a 3.9 GHz superconducting, multi-cell cavity as the solution for ILC, whilst bunch structure and beam-loading considerations suggest an X-band copper travelling wave structure for CLIC. These two cavity solutions are very different in design but share complex design issues. Phase stabilisation, beam loading, wakefields and mode damping are fundamental issues for these crab cavities. Requirements and potential design solutions will be discussed for both colliders.Comment: 3 pages. To be published in proceedings of LINAC 2008, Victoria, Canad

Conductivity of twin walls - surface junctions in ferroelastics: interplay of deformation potential, octahedral rotations, improper ferroelectricity and flexoelectric coupling

Electronic and structural phenomena at the twin domain wall-surface junctions in the ferroelastic materials are analyzed. Carriers accumulation caused by the strain-induced band structure changes originated via the deformation potential mechanism, structural order parameter gradient, rotostriction and flexoelectric coupling is explored. Approximate analytical results show that inhomogeneous elastic strains, which exist in the vicinity of the twin walls - surface junctions due to the rotostriction coupling, decrease the local band gap via the deformation potential and flexoelectric coupling mechanisms. This is the direct mechanism of the twin walls static conductivity in ferroelastics and, by extension, in multiferroics and ferroelectrics. On the other hand, flexoelectric and rotostriction coupling leads to the appearance of the improper polarization and electric fields proportional to the structural order parameter gradient in the vicinity of the twin walls - surface junctions. The "flexo-roto" fields leading to the carrier accumulation are considered as indirect mechanism of the twin walls conductivity. Comparison of the direct and indirect mechanisms illustrates complex range of phenomena directly responsible for domain walls static conductivity in materials with multiple order parameters.Comment: 35 pages, 11 figures, 3 table, 3 appendices Improved set of rotostriction coefficients are used in calculation

A prototype liquid Argon Time Projection Chamber for the study of UV laser multi-photonic ionization

This paper describes the design, realization and operation of a prototype liquid Argon Time Projection Chamber (LAr TPC) detector dedicated to the development of a novel online monitoring and calibration system exploiting UV laser beams. In particular, the system is intended to measure the lifetime of the primary ionization in LAr, in turn related to the LAr purity level. This technique could be exploited by present and next generation large mass LAr TPCs for which monitoring of the performance and calibration plays an important role. Results from the first measurements are presented together with some considerations and outlook.Comment: 26 pages, 27 figure

Machine-Related Backgrounds in the SiD Detector at ILC

With a multi-stage collimation system and magnetic iron spoilers in the tunnel, the background particle fluxes on the ILC detector can be substantially reduced. At the same time, beam-halo interactions with collimators and protective masks in the beam delivery system create fluxes of muons and other secondary particles which can still exceed the tolerable levels for some of the ILC sub-detectors. Results of modeling of such backgrounds in comparison to those from the e+ e- interactions are presented in this paper for the SiD detector.Comment: 29 pages, 34 figures, 7 table

LED-based Fourier transform spectroscopy of H216O in the range 15500-16000 cm-1

The vibrational-rotational absorption spectrum of water vapor within the range 15500–16000 cm−1 is measured and analyzed. The spectrum is recoded with an IFS-125M Fourier transform spectrometer with a resolution of 0.03 cm−1, at pressure of 25 mbar, at a temperature of 24°C, and at an optical path length of 34.8 m. The measurements are performed using a multipass White cell with a base length of 60 cm. A light-emitting diode is used as a radiation source. The signal-to-noise ratio is about 104, which makes it possible to measure the parameters of lines with intensities on the order of 10−27 cm/molecule. The centers, intensities, and half-widths of lines are determined by fitting the Voigt profile parameters to measured data set by the least squares method. A list of more than 430 lines is formed based on the analysis of the spectrum. The obtained results are compared with calculated and experimental data of other authors

Investigation of the Chaotic Dynamics of an Electron Beam with a Virtual Cathode in an External Magnetic Field

The effect of the strength of the focusing magnetic field on chaotic dynamic processes occurring inan electron beam with a virtual cathode, as well as on the processes whereby the structures form in the beamand interact with each other, is studied by means of two-dimensional numerical simulations based on solving a self-consistent set of Vlasov-Maxwell equations. It is shown that, as the focusing magnetic field is decreased,the dynamics of an electron beam with a virtual cathode becomes more complicated due to the formation andinteraction of spatio-temporal longitudinal and transverse structures in the interaction region of a vircator. The optimum efficiency of the interaction of an electron beam with the electromagnetic field of the vircator isachieved at a comparatively weak external magnetic field and is determined by the fundamentally two-dimensional nature of the motion of the beam electrons near the virtual cathode.Comment: 12 pages, 8 figure