介质壁加速腔加速结构优化

为了在介质壁加速器中增大轴向加速电场, 提高加速梯度的同时抑制径向电场对束包络的扩张, 提出了在每个加速电极上添加金属栅网结构。采用基于粒子云网格方法的电磁粒子模拟软件对不加栅网与添加栅网的电极结构进行了数值仿真, 分析了不同结构下加速管道中的电场分布和束包络变化。通过实验对比了两种不同结构下经过相同的加速长度获得的粒子能量。结果表明:添加金属栅网结构相对于不加栅网的金属小孔式结构, 轴向加速电场强度提高20%, 同时径向电场得到有效抑制;栅网结构下, 被加速的粒子束在自由漂移空间中的径向发散基本得到抑制;在相同的加速长度下加速H3+粒子, 栅网结构得到的能量增益提高了一倍。     

介质壁加速腔加速结构优化

为了在介质壁加速器中增大轴向加速电场, 提高加速梯度的同时抑制径向电场对束包络的扩张, 提出了在每个加速电极上添加金属栅网结构。采用基于粒子云网格方法的电磁粒子模拟软件对不加栅网与添加栅网的电极结构进行了数值仿真, 分析了不同结构下加速管道中的电场分布和束包络变化。通过实验对比了两种不同结构下经过相同的加速长度获得的粒子能量。结果表明：添加金属栅网结构相对于不加栅网的金属小孔式结构, 轴向加速电场强度提高20%, 同时径向电场得到有效抑制;栅网结构下, 被加速的粒子束在自由漂移空间中的径向发散基本得到抑制;在相同的加速长度下加速H3+粒子, 栅网结构得到的能量增益提高了一倍。     

Design concept of cryogenic accelerating structures of a copper accelerator

The surface resistance of copper is studied in the region of classical and anomalous skin effect. The surface resistance gain (equal to the ratio of the surface resistances of copper at room and helium temperatures) is determined as a function of the electromagnetic field frequency. It is shown that the gain has an inverse power dependence on frequency. The frequencies at which the gain for copper is equal to 10 are determined. It is found that high-frequency power losses in the walls of the accelerating structure of the accelerator, which is prepared from nonsuperconducting metals at T ≥ 4.2 K, can be reduced by more than an order of magnitude as compared to an accelerating structure operating at room temperature. This confirms the possibility of developing a high-efficiency accelerator.     

Phase synchronization in tilted deterministic ratchets

We study phase synchronization for a ratchet system. We consider the deterministic dynamics of a particle in a tilted ratchet potential with an external periodic forcing, in the overdamped case. The ratchet potential has to be tilted in order to obtain a rotator or self-sustained nonlinear oscillator in the absence of external periodic forcing. This oscillator has an intrinsic frequency that can be entrained with the frequency of the external driving. We introduced a linear phase through a set of discrete time events and the associated average frequency, and show that this frequency can be synchronized with the frequency of the external driving. In this way, we can properly characterize the phenomenon of synchronization through Arnold tongues, which represent regions of synchronization in parameter space, and discuss their implications for transport in ratchets.     

Conception design of helium ion FFAG accelerator with induction accelerating cavity

Technological advancements are strongly required to fulfill the demands of new accelerator devices with the highest accelerating gradients and operation reliability for the future colliders.To this purpose an extensive R&D regarding molybdenum coatings on copper is in progress.In this contribution we describe chemical composition,deposition quality and resistivity properties of diferent molybdenum coatings obtained via sputtering.The deposited films are thick metallic disorder layers with diferent resistivity values above and below the molibdenum dioxide reference value.Chemical and electrical properties of these sputtered coatings have been characterized by Rutherford backscattering,XANES and photoemission spectroscopy.We will also consider multiple cells standing wave section coated by a molybdenum layer designed to improve the performance of X-Band accelerating systems.     

Quantum theory of electron motion in a cyclic resonant accelerator

The motion of a relativistic electron in a constant focusing magnetic field and a high-frequency rotational electromagnetic field, used to offset the radiative energy loss, is studied on the basis of the Klein-Gordon equation. The solutions found may be used to construct a theory for electron storage rings, in which quantum fluctuations are particularly important.Translated from Izvestiya VUZ. Fizika, No. 4, pp. 12–22, April, 1970.     

Equations of motion of particle in circular accelerator with general field

Lagrange equations of motion are derived for a particle in a circular accelerator with arbitrarily spatially variable guiding magnetic field describing the motion of a particle by means of dimensionless deviations of the particle from a circle as the reference curve. The author also derives linearized equations of motion (so-called equations of perturbations used in stability investigations according to the Ljapunov method of the 1st approximation). The equations are given in the closed form and are thus quite exact.     

Electric strength of an accelerating gap in a plasma source of charged particles

An investigation is performed on the electric strength of accelerating gaps of plasma sources of electrons and ions in the presence of beam plasma behind the accelerating electrode. For the bipolar mode, when the gas ionization in the accelerating gas may be ignored, the conditions of bridging the gap of plasma discharge of a source with beam plasma and of disruption of emission current are found.     

Phase velocity and particle injection in a self-modulated proton-driven plasma wakefield accelerator

It is demonstrated that the performance of the self-modulated proton driver plasma wakefield accelerator is strongly affected by the reduced phase velocity of the plasma wave. Using analytical theory and particle-in-cell simulations, we show that the reduction is largest during the linear stage of self-modulation. As the instability nonlinearly saturates, the phase velocity approaches that of the driver. The deleterious effects of the wake's dynamics on the maximum energy gain of accelerated electrons can be avoided using side-injections of electrons, or by controlling the wake's phase velocity by smooth plasma density gradients.     

Electric strength of the accelerating gap of a plasma electron source at rough vacuum

Conditions for the electric breakdown of the accelerating gap of a plasma electron source are determined. It is shown that, depending on the gas pressure and the size of openings in the emission electrode, two types of breakdown can occur. One of them is due to the ignition of a low-voltage discharge between the electrodes of the accelerating system, and the other one is caused by switching of the main discharge from the anode to the accelerating electrode.     

Approximation of equations of motion of particle in circular accelerator

It is shown that the equations of motion of a particle in a circular accelerator with general azimuthally periodic guiding magnetic field are substantially simplified if a large number of field periods is assumed. The simplified equations permit a clear picture of the influence of the magnetic field parameters on the dynamics of the accelerated particle to be obtained easily.     

Phase transition for absorbed Brownian motion with drift

We study one-dimensional Brownian motion with constant drift toward the origin and initial distribution concentrated in the strictly positive real line. We say that at the first time the process hits the origin, it is absorbed. We study the asymptotic behavior, ast, ofm _t , the conditional distribution at time zero of the process conditioned on survival up to timet and on the process having a fixed value at timet. We find that there is a phase transition in the decay rate of the initial condition. For fast decay rate (subcritical case)m _t is localized, in the critical casem _t is located around , and for slow rates (supercritical case)m _t is located aroundt. The critical rate is given by the decay of the minimal quasistationary distribution of this process. We also study in each case the asymptotic distribution of the process, scaled by , conditioned as before. We prove that in the subcritical case this distribution is a Brownian excursion. In the critical case it is a Brownian bridge attaining 0 for the first time at time 1, with some initial distribution. In the supercritical case, after centering around the expected value—which is of the order oft—we show that this process converges to a Brownian bridge arriving at 0 at time 1 and with a Gaussian initial distribution.     

Phase front motion in uniaxial ferromagnet

It is well known that in the uniaxial ferromagnet in the presence of an external magnetic field perpendicular to the easy axis (h_x) a continuous phase transition occurs for a critical value of this field. There are metastable and stable states if one includes a small field parallel to the easy axis (h_z). The motion of the relaxation front of the metastable state is investigated. It is found that an “interphase wall of Neel-type” exists, its velocity is proportional to h_z and increases when the critical point is approached.     

Operation of a ruby laser with tilted mirrors

The present paper is concerned with a study of the operation of a ruby laser with plane mirrors set at angles of 3–10 relative to each other. It is shown that tilting the mirrors shifts the intensity maximum on the mirrors and deflects the radiation beams toward the further edges of the mirrors. The prevailing patterns in the near and far zones were found to coincide for all mirror tilt directions. The experimental results are compared with theoretical deductions and a conclusion is drawn regarding the modal composition of the radiation.     

Opening an energy gap in an electron double layer system at the integer filling factor in a tilted magnetic field

We employ magnetocapacitance measurements to study the spectrum of a double layer system with gate-voltage-tuned electron density distributions in tilted magnetic fields. For the dissipative state in normal magnetic fields at filling factor v=3 and 4, a parallel magnetic field component is found to give rise to the opening of a gap at the Fermi level. We account for the effect in terms of parallel-field-caused orthogonality breaking of the Landau wave functions with different quantum numbers for two subbands.     

Vibro-acoustic analysis of a rectangular-like cavity with a tilted wall

In this paper, a fully coupled vibro-acoustic model is developed to characterize the structural and acoustic coupling of a flexible panel backed by a rectangular-like cavity with a slight geometrical distortion, which is introduced through a tilted wall. The combined integro-modal approach is used to handle the acoustic pressure inside the irregular-shaped cavity. Based on the model proposed, the distortion effect on the vibro-acoustic behavior of the coupled system is investigated using the averaged sound pressure level inside the enclosure and the averaged quadratic velocity of the vibrating plate. Simulations are conducted to examine the distortion effect on acoustic natural frequencies, acoustic pressures and structural responses. Effects of the wall inclination on coupling coefficients are also assessed, and an index is proposed to quantify the degree of variation of coupling strength.