Transverse Instabilities of Coasting Beams with Space Charge

Transverse beam stability is strongly affected by the beam space charge. Usually it is analyzed with the rigid-beam model. However this model is only valid when a bare (not affected by the space charge) tune spread is small compared to the space charge tune shift. This condition specifies a relatively small area of parameters which, however, is the most interesting for practical applications. The Landau damping rate and the beam Schottky spectra are computed assuming that validity condition is satisfied. The results are applied to a round Gaussian beam. The stability thresholds are described by simple fits for the cases of chromatic and octupole tune spreads.Comment: 6 pages, 2 figures, accepted by Phys. Rev. ST - Accel. Beam

Fractive antennas on the flying mashines

Проведен обзор существующих щелевых антенн, которые могут устанавливаться на летательных аппаратах. Необходимость работы в этой области диктуется требованиями аэродинамических характеристик антенн, размещенных на подвижных объектах. Модификация формы линии передачи и щелевой антенны позволяет обеспечить точное его совпадение с обшивкой летательного аппарата и обеспечение необходимой механической прочности. Более того, несмотря на все это, необходимо еще и обеспечить заданную диаграмму направленности антенны. Все эти результаты могут достигаться варьированием количества щелевых отверстий, а также расстоянием между ними. Кроме того, большое влияние на полученное излучение оказывает форма самого щелевого отверстия и местом расположения щели. Зная принцип работы щелевых антенн, можно получать при изготовлении качественные высотомерные устройства, измерители скорости объекта и т.п.This text made review the types of the fricative antennas, which can be built on the flying machines. This work is very necessary because of the requirement, that antennas on the flying machines must have aerodynamic parameters. Modification of the form of the transmission line and fricative antenna can ensure exact coincidence with encasement of the flying machine and supporting necessary mechanical strength. Moreover, despite all this facts, it is necessary to make right directivity pattern of the antenna. All this results can be obtain by variation the number of the fricative holes, and the distance between them. Then, the big influence on the radiation makes the design of the fricative hole, and the place, where thus hole can be built in. If we would know the principles of working of the fricative antennas, we can derive qualitative devices, like devises which can be used for: dimension of the height, dimension of the speed pf the object and many other engineering problems

Neutron electric form factor at large momentum transfer

Based on the recent, high precision data for elastic electron scattering from protons and deuterons, at relatively large momentum transfer $Q^2$, we determine the neutron electric form factor up to $Q^2=3.5$ GeV$^2$. The values obtained from the data (in the framework of the nonrelativistic impulse approximation) are larger than commonly assumed and are in good agreement with the Gari-Kr\"umpelmann parametrization of the nucleon electromagnetic form factors.Comment: 11 pages 2 figure

On isovector meson exchange currents in the Bethe-Salpeter approach

We investigate the nonrelativistic reduction of the Bethe-Salpeter amplitude for the deuteron electrodisintegration near threshold energies. To this end, two assumptions have been used in the calculations: 1) the static approximation and 2) the one iteration approximation. Within these assumptions it is possible to recover the nonrelativistic result including a systematic extension to relativistic corrections. We find that the so-called pair current term can be constructed from the $P$-wave contribution of the deuteron Bethe-Salpeter amplitude. The form factor that enters into the calculation of the pair current is constrained by the manifestly gauge independent matrix elements.Comment: 15 pages, incl. 3 figures, to be published Phys. Rev.

Superscaling and Neutral Current Quasielastic Neutrino-Nucleus Scattering beyond the Relativistic Fermi Gas Model

The superscaling analysis is extended to include quasielastic (QE) scattering via the weak neutral current of neutrinos and antineutrinos from nuclei. The scaling function obtained within the coherent density fluctuation model (used previously in calculations of QE inclusive electron and charge-changing (CC) neutrino scattering) is applied to neutral current neutrino and antineutrino scattering with energies of 1 GeV from $^{12}$C with a proton and neutron knockout (u-channel inclusive processes). The results are compared with those obtained using the scaling function from the relativistic Fermi gas model and the scaling function as determined from the superscaling analysis (SuSA) of QE electron scattering.Comment: 10 pages, 6 figures, published in Phys. Rev.

Development the emitter, which can based on the waveguide with the special form

Необходимость работы в этой области диктуется требованиями аэродинамических характеристик антенн, размещенных на подвижных объектах. Модификация формы линии передачи ищелевой антенны позволяет обеспечить точное его совпадение с обшивкой летательного аппарата и обеспечение необходимой механической прочности. Более того, несмотря на все это, необходимо еще и обеспечить заданную диаграмму направленности антенны. Все эти результаты могут достигаться варьированием количества щелевых отверстий, а также расстоянием между ними. Кроме того, большое влияние на полученное излучение оказывает форма самого щелевого отверстия и местом расположения щели. Зная принцип работы щелевых антенн, можно получать при изготовлении качественные высотомерные устройства, измерители скорости объекта и т.п.This work is very necessary because of the requirement, that antennas on the flying machines must have aerodynamic parameters. Modification of the form of the transmission line and fricative antenna can ensure exact coincidence with encasement of the flying machine and supporting necessary mechanical strength. Moreover, despite all this facts, it is necessary to make right directivity pattern of the antenna. All this results can be obtain by variation the number of the fricative holes, and the distance between them. Then, the big influence on the radiation makes the design of the fricative hole, and the place, where thus hole can be built in. If we would know the principles of working of the fricative antennas, we can derive qualitative devices, like devises which can be used for: dimension of the height, dimension of the speed pf the object and many other engineering problems

Antibacterial effect of nisin in vitro

Results of experimental studies of antimicrobial action of gel compositions containing active substance nisin are presented in the article. It is shown that increasing concentration of nisin at constant concentrations of the other components in the mixture inhibits growth of Staphylococcus aureus and Pseudomonas aeruginosa. The optimal concentration of nisin at which the process of pathogens growth inhibition is the most effective was determined in the experiment

Transverse Instabilities in the Fermilab Recycler

Transverse instabilities of the antiproton beam have been observed in the Recycler ring soon after its commissioning. After installation of transverse dampers, the threshold for the instability limit increased significantly but the instability is still found to limit the brightness of the antiprotons extracted from the Recycler for Tevatron shots. In this paper, we describe observations of the instabilities during the extraction process as well as during dedicated studies. The measured instability threshold phase density agrees with the prediction of the rigid beam model within a factor of 2. Also, we conclude that the instability threshold can be significantly lowered for a bunch contained in a narrow and shallow potential well due to effective exclusion of the longitudinal tails from Landau damping.Comment: 17 pages, 'Technical' Note, Use of 'internal' jargon and reference

Superscaling in Nuclei: A Search for Scaling Function Beyond the Relativistic Fermi Gas Model

We construct a scaling function $f(\psi^{\prime})$ for inclusive electron scattering from nuclei within the Coherent Density Fluctuation Model (CDFM). The latter is a natural extension to finite nuclei of the Relativistic Fermi Gas (RFG) model within which the scaling variable $\psi^{\prime}$ was introduced by Donnelly and collaborators. The calculations show that the high-momentum components of the nucleon momentum distribution in the CDFM and their similarity for different nuclei lead to quantitative description of the superscaling in nuclei. The results are in good agreement with the experimental data for different transfer momenta showing superscaling for negative values of $\psi^{\prime}$, including those smaller than -1.Comment: 16 pages, 5 figures, submitted for publication to Phys. Rev.

The relativistic impulse approximation for the exclusive electrodisintegration of the deuteron

The electrodisintegration of the deuteron in the frame of the Bethe-Salpeter approach with a separable kernel of the nucleon-nucleon interaction is considered. This conception keeps the covariance of a description of the process. A comparison of relativistic and nonrelativistic calculations is presented. The factorization of the cross section of the reaction in the impulse approximation is obtained by analytical calculations. It is shown that the photon-neutron interaction plays an important role.Comment: 31 pages, 14 figures, 1 tabl