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At least 37 records · Page 2Linked to original sources
arXiv1996

On Two-cavity Coupling

This work presents research results on a novel analytical model of electromagnetic systems coupling through small size holes. The key problem regarding coupling of two cavities through an aperture in separating screen of finite thickness without making assumption on smallness of any parameters is considered. We are the first to calculate on the base of rigorous electromagnetic approach the coupling coefficients of the cylindrical cavities within the limit of small aperture and infinitely thin separating screen. The numeric results of electromagnetic characteristic dependencies that have been impossible to perform on the base of previous models are given.

acc-phys↗
arXiv1996

Analytical Solutions in the Two-cavity Coupling Problem

Analytical solution of precise equations that describe the rf-coupling of two cavities through a co-axial cylindrical hole are given for various limited cases. For their derivation we have used the method of solution of an infinite set of linear algebraic equations, based on its transformation into dual integral equations.

acc-phys↗
arXiv1996

Approximate Analytical Description of the Underdense Short Plasma Lens

The perturbative approach for describing the underdense plasma--ultrarelativistic electron bunch system is developed, using the ratio $\frac{n_0}{n_b}$ as a small parameter ($n_b$--bunch,$n_0$--plasma electron densities). Focusing of the electron bunch emerged in the first approximation of the perturbative procedure as a result of the plasma electrons redistribution. Focusing gradient and strength for ultrarelativistic, flat, uniform and short bunch are obtained and compared with the previous results.

acc-phys↗
arXiv1996

Orbit Dynamics for Unstable Linear Motion

A treatment is given of the orbit dynamics for linear unstable motion that allows for the zeros in the beta function and makes no assumptions about the realness of the betatron and phase functions. The phase shift per turn is shown to be related to the beta function and the number of zeros the beta function goes through per turn. The solutions of the equations of motion are found in terms of the beta function.

acc-phys↗
arXiv1996

An Investigation of Stochastic Cooling in the Framework of Control Theory

This report provides a description of unbunched beam stochastic cooling in the framework of control theory. The main interest in the investigation is concentrated on the beam stability in an active cooling system. A stochastic cooling system must be considered as a closed-loop, similar to the feedback systems used to damp collective instabilities. These systems, which are able to act upon themselves, are potentially unstable. The self-consistent solution for the beam motion is derived by means of a mode analysis of the collective beam motion. This solution yields a criterion for the stability of each collective mode. The expressions also allow for overlapping frequency bands in the beam spectrum and thus are valid over the entire frequency range. Having established the boundaries of stability in this way, the Fokker-Planck equation is used to describe the cooling process. This description does not include collective effects and thus a stable beam must be assumed. Hence the predictions about the cooling process following from the Fokker-Planck equation only make physical sense within the boundaries of beam stability. Finally it is verified that the parameters of the cooling system which give the best cooling results are compatible with the stability of the beam.

acc-phys↗
arXiv1996

Impedances and Power Losses for an Off-Axis Beam

A method for calculating coupling impedances and power losses for off-axis beams is developed. It is applied to calculate impedances of small localized discontinuities like holes and slots, as well as the impedance due to a finite resistivity of chamber walls, in homogeneous chambers with an arbitrary shape of the chamber cross section. The approach requires to solve a two-dimensional electrostatic problem, which can be easily done numerically in the general case, while for some particular cases analytical solutions are obtained.

acc-phys↗
arXiv1996

Selfacceleration of Electrons in One-dimensional Bunches, Moving in Cold Plasma

Nonlinear dynamics of the one-dimensional ultrarelativistic bunch of electrons,moving in cold plasma,is considered in multiple scales perturbative approach. A square root of the inverse Lorentz factor of the bunch electrons is taken as a small parameter. Bunch electrons momenta is changed in the first approximation.In the underdense plasma and for the model example of the combined bunch the selfacceleration of the bunch electrons can be remarkable.

acc-phys↗
arXiv1996

A High Current Proton Linac with 352 MHz SC Cavities

A proposal for a 10-120 mA proton linac employing superconducting beta-graded, CERN type, four cell cavities at 352 MHz is presented. The high energy part (100 MeV-1 GeV) of the machine is split in three beta-graded sections, and transverse focusing is provided via a periodic doublet array. All the parameters, like power in the couplers and accelerating fields in the cavities, are within the state of the art, achieved in operating machines. A first stage of operation at 30 mA beam current is proposed, while the upgrade of the machine to 120 mA operation can be obtained increasing the number of klystrons and couplers per cavity. The additional coupler ports, up to four, will be integrated in the cavity design. Preliminary calculations indicate that beam transport is feasible, given the wide aperture of the 352 MHz structures. A capital cost of less than 100 M$ at 10 mA, reaching up to 280 M$ for the 120 mA extension, has been estimated for the superconducting high energy section (100 MeV-1 GeV). The high efficiency of the proposed machine, reaching 50% at 15 mA, makes it a good candidate for proposed nuclear waste incineration facilities and Energy Amplifier studies.

acc-phys↗
arXiv1996

Coupling Impedances of Azimuthally Symmetric Obstacles of Semi-Elliptical Shape in a Beam Pipe

The beam coupling impedances of small axisymmetric obstacles having a semi-elliptical cross section along the beam in the vacuum chamber of an accelerator are calculated at frequencies for which the wavelength is large compared to a typical size of the obstacle. Analytical results are obtained for both the irises and the cavities with such a shape which allow simple estimates of their broad-band impedances.

acc-phys↗
arXiv1996

Sonoluminescence and the Heimlich Effect

The phenomenon of sonoluminescence (SL), originally observed some sixty years ago, has recently become the focus of renewed interest, particularly with the discovery that one can trap a single bubble and induce it to exhibit SL stably over a large number of acoustical cycles. In this work we shall adopt a version of the provocative suggestion put forward by Schwinger: the mechanism responsible for the radiation in SL is a dynamic version of the Casimir effect. It has been known since Casimir's original work in 1948 that the zero-point energy of quantum fields can be modified by the presence of boundaries, and that these modifications generate observable effects. For example, in Casimir's original work, the quantum fluctuations of the electromagnetic field in the presence of a pair of uncharged, parallel, perfectly conducting plates were shown to give rise to an attractive force between the plates.

hep-ph↗
arXiv1996

High energy proton acceleration in dissolving plasma clots

We consider the acceleration of particles (protons) in a plasma clot by an induced field which appears due to the dissolving of the clot. The mechanism of this acceleration is based on a model where the clot consists of double flat moving current layers. It is assumed that the currents flow in opposite directions, while the clot moves in a perpendicular one. It is shown that protons can reach the highest observed energy (of the order of $10^{11}- 10^{12}$GeV), providing that the size of the clot is large enough.

hep-ph↗
arXiv1995

Ultrashort Laser-pulse Diagnostics for Detection of Ordering within an Ion beam

A novel diagnostic method to detect ordering within one-dimensional ion beams in a storage ring is presented. The ions are simultaneously excited by a ultrashort pulsed laser ($\simeq 1$ ps) at two different locations along the beam and fluorescence is detected by a group of four photo-multipliers. Correlation in fluorescence signals is a firm indication that the ion beam has an ordered structure.

acc-phys↗
arXiv1995

A Study of Influence of Synchrotron Radiation Quantum Fluctuations on the Synchrotron Oscillations of a Single Electron Using Undulator Radiation

A single electron circulating in a storage ring is a very peculiar object. Synchrotron radiation quantum fluctuation causes stohastic process in the synchrotron oscillation of an electron. The radiation from a undulator permits one to obtain discret moments of longitudional electron motion. Experiments with a single electron on on the VEPP-3 optical klystrons are described.

acc-phys↗
arXiv1995

Radiation Damping and Quantum Excitation for Longitudinal Charged Particle Dynamics in the Thermal Wave Model

On the basis of the recently proposed {\it Thermal Wave Model (TWM) for particle beams}, we give a description of the longitudinal charge particle dynamics in circular accelerating machines by taking into account both radiation damping and quantum excitation (stochastic effect), in presence of a RF potential well. The longitudinal dynamics is governed by a 1-D Schrödinger-like equation for a complex wave function whose squared modulus gives the longitudinal bunch density profile. In this framework, the appropriate {\it r.m.s. emittance} scaling law, due to the damping effect, is naturally recovered, and the asymptotic equilibrium condition for the bunch length, due to the competition between quantum excitation (QE) and radiation damping (RD), is found. This result opens the possibility to apply the TWM, already tested for protons, to electrons, for which QE and RD are very important.

acc-phys↗