BEAM25 program for numerical simulation of the processes of high-current electron beam shaping, acceleration and transportation

The paper presents the description of a self-consistent difference scheme and numerical algorithm of a joint solution of Maxwell equations and equation of charged particle motion on a regular non-uniform mesh. The given algorithm is applied to calculate non-stationary electromagnetic processes in axially symmetric structures consisting of components with different electric and magnetic properties as well as to simulate numerically the processes of high-current electron beam shaping, acceleration and transportation. The example of the program use for the calculation of electron beam characteristics in a STRAUS-2 accelerator diode is given. The obtained coincidence of calculation and experimental data lies within the limits of ±10%

WEC program for calculation of systems of accelerating voltage pulses formation on lines with distributed parameters

For some years at VNIIEF there have been developed iron-deprived linear induction accelerators (LIA) [1-3], applying, as basic elements of accelerating system, inductors with water insulation on the base of lines with distributed parameters. When creating such facilities one of the most important tasks is development of systems of forming high-voltage pulses of accelerating voltage with required electric characteristics. On the basis of solving the Maxwell equations system an algorithm of numerical simulation of non-stationary electromagnet processes in axially symmetrical structures consisting of elements with different electric properties (dielectric constant and magnetic permeability, conductivity) is developed. The form of the calculation area is supposed to be rectangular, limits of subareas (elements) separation may be random. There is given a description of applied difference scheme on regular inhomogeneous grid and their realization in the computer program. There is given an example of the program application for calculating electromagnet processes in STRAUS-2 accelerator [4] and their comparison with experimental results

Design of STRAUS-R accelerator

The paper presents a design of the direct-operation high-current electron accelerator STRAUS-R that is a modification of STRAUS-2 now in force. The accelerator is aimed at generating single bremsstrahlung pulses in the mode of electron beam focusing on the target. According to the calculations it should provide for getting the dose (Si) of 0.2÷0.25 Gy at a 1 meter distance from the target, the electron beam current being equal to 50÷60 kA, boundary energy of electrons – to 2.7÷3.0 MeV, bremsstrahlung pulse duration – to ≤ 50 ns and beam diameter on the target – to ≤ 5 mm. The description and results of numerical simulation of physics processes taking place in the accelerator are given

Numerical simulation of the processes of small-diameter high-current electron beam shaping and injection

With the aid of BEAM25 program there was carried out the numerical simulation of the non-stationary process of shaping a small-diameter (≤ 20 mm) high-current hollow electron beam in a diode with magnetic insulation, as well as of the process of beam injection into the accelerating LIA track. The diode configuration for the purpose of eliminating the leakage of electron flux to the anode surface was updated. Presented are the results of calculation of the injected beam characteristics (amplitude-time parameters of a current pulse, space-angle distributions of electrons etc.) depending on diode geometric parameters

Scalar Field Corrections to AdS_4 Gravity from Higher Spin Gauge Theory

We compute the complete contribution to the stress-energy tensor in the minimal bosonic higher spin theory in D=4 that is quadratic in the scalar field. We find arbitrarily high derivative terms, and that the total sign of the stress-energy tensor depends on the parity of the scalar field.Comment: 15 pages + appendix (30 pages

Evaluating the AdS dual of the critical O(N) vector model

We argue that the AdS dual of the three dimensional critical O(N) vector model can be evaluated using the Legendre transform that relates the generating functionals of the free UV and the interacting IR fixed points of the boundary theory. As an example, we use our proposal to evaluate the minimal bulk action of the scalar field that it is dual to the spin-zero ``current'' of the O(N) vector model. We find that the cubic bulk self interaction coupling vanishes. We briefly discuss the implications of our results for higher spin theories and comment on the bulk-boundary duality for subleading N.Comment: 17 pages, 1 figure, v2 references added, JHEP versio

Holography of the N=1 Higher-Spin Theory on AdS4

We argue that the N=1 higher-spin theory on AdS4 is holographically dual to the N=1 supersymmetric critical O(N) vector model in three dimensions. This appears to be a special form of the AdS/CFT correspondence in which both regular and irregular bulk modes have similar roles and their interplay leads simultaneously to both the free and the interacting phases of the boundary theory. We study various boundary conditions that correspond to boundary deformations connecting, for large-N, the free and interacting boundary theories. We point out the importance of parity in this holography and elucidate the Higgs mechanism responsible for the breaking of higher-spin symmetry for subleading N.Comment: 19 page

On the covariant quantization of tensionless bosonic strings in AdS spacetime

The covariant quantization of the tensionless free bosonic (open and closed) strings in AdS spaces is obtained. This is done by representing the AdS space as an hyperboloid in a flat auxiliary space and by studying the resulting string constrained hamiltonian system in the tensionless limit. It turns out that the constraint algebra simplifies in the tensionless case in such a way that the closed BRST quantization can be formulated and the theory admits then an explicit covariant quantization scheme. This holds for any value of the dimension of the AdS space.Comment: 1+16 pages; v4 two clarifications adde

Observation of exclusive DVCS in polarized electron beam asymmetry measurements

We report the first results of the beam spin asymmetry measured in the reaction e + p -> e + p + gamma at a beam energy of 4.25 GeV. A large asymmetry with a sin(phi) modulation is observed, as predicted for the interference term of Deeply Virtual Compton Scattering and the Bethe-Heitler process. The amplitude of this modulation is alpha = 0.202 +/- 0.028. In leading-order and leading-twist pQCD, the alpha is directly proportional to the imaginary part of the DVCS amplitude.Comment: 6 pages, 5 figure

A Bayesian analysis of pentaquark signals from CLAS data

We examine the results of two measurements by the CLAS collaboration, one of which claimed evidence for a $\Theta^{+}$ pentaquark, whilst the other found no such evidence. The unique feature of these two experiments was that they were performed with the same experimental setup. Using a Bayesian analysis we find that the results of the two experiments are in fact compatible with each other, but that the first measurement did not contain sufficient information to determine unambiguously the existence of a $\Theta^{+}$. Further, we suggest a means by which the existence of a new candidate particle can be tested in a rigorous manner.Comment: 5 pages, 3 figure