Yerevan synchrotron in the mode of stretcher for injected electron beam of 75 MeV energy

At the Yerevan synchrotron, an experiment is planned on the investigation of a clustered structure of nuclei, when the synchrotron is working in the mode of stretcher of the injected electron beam with energy of 75 MeV. The results of calculation of the circulating beam dynamics in the vacuum chamber of the synchrotron during 5 ms and changes of the beam parameters due to scattering of electrons by nuclei of the residual gas are presented. It is shown that the increase in the beam sizes due to scattering of electrons is permissible for available sizes of the synchrotron vacuum chamber.     

Precise out-vacuum proton beam monitoring system based on vibrating wire

As an instrument for Korea Multi-purpose Accelerator Complex (KOMAC) facility proton beam profiling, a vibrating wire monitor (VWM) has been installed and tested at TR23 target room. Experiments were done at very low (100 nA) beam current conditions. At the number of particles about 10¹¹ proton/train and trains repetition rate of 0.1 Hz we have measured the beam profile by a few scanning steps. The experience accumulated in these experiments turned out to be useful for the VWM upgrades (e. g. understanding interactions of protons with wire materials and heat transfer processes) and will be particularly helpful for the KOMAC beam halo measurements in the future high-current operation.     

Design and simulation of the wire scanner for the injector linac of BEPC Ⅱ

BEPC Ⅱ,the upgrade project of Beijing Electron Positron Collider (BEPC),is an accelerator with large beam current and high luminosity,so an efficient and stable injector is required.Several beam diagnostic and monitoring instruments are used.A new diagnostic instrument--wire scanner,has been designed and will be used to nleasure the profile of the linac beam of BEPC Ⅱ.This paper describes the prototype of this system and the cause of heat generating of the wire.Some simulation results of the heat and force by using finite element method software-ANSYS(R),2) are presented and discussed.     

Effects of scanning speed on the laser beam profile measurements by vibrating wire

For measuring laser beam profiles, a vibrating wire monitor (VWM) has been introduced. The measurements were carried out at different speeds of scan. Preliminary estimates were made for the calculation of the VWM response times with respect to the thermal losses along the wire, and radiative and convective losses. These estimates, however, do not determine the difference between the beam profile and the frequency response of the VWM for a given scan rate. To evaluate the reliability of the frequency response of the VWM, comparisons between forward and reverse beam scans at different speeds have been used. The results of these scans are used to correct the thermal inertia in the frequency response of the VWM.     

一种新的电子束扫描电流产生方法

 在工业辐照电子直线加速器中,电流发生器是电子束扫描设备中的重要部分,可控式电流反馈-电流镜产生扫描电流是一种新方法,其电流波形可被扫描均匀度指标修正,不仅可以得到良好的电子束扫描均匀度,而且还可以提高均匀扫描的速度。     

2MeV注入器脉冲电子束时间分辨能谱诊断研究

 介绍了利用磁分析器和电子束产生的契伦科夫辐射光诊断直线感应加速器脉冲电子束时间分辨能谱的原理、方法及诊断系统,对中物院2MeV感应叠加型注入器的2kA强流脉冲电子束时间分辨能谱进行实验诊断,并与二极管电压进行对比分析。测得能量约2.2MeV,60ns内最大能量变化为4%。     

Longitudinal beam distribution and coherent synchrotron radiation of relativistic electron clouds

The effect of the form of the longitudinal distribution of an electron beam on the characteristics of coherent synchrotron radiation is investigated. The spectral density and total power of the coherent synchrotron radiation are studied as functions of the dispersion and excess of the longitudinal distribution, as well as of the energy of the radiating particles.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 2, pp. 17–20, February, 1977.     

All optical electron injector using an intense ultrashort pulse laser and a solid wire target

Energetic electron bunches were generated by irradiating a solid tungsten wire 13 μm wide with 50 femtosecond pulses at an intensity of ∼3×10¹⁸ W/cm². The electron yield, energy spectrum and angular distribution were measured. These energetic electron bunches are suitable for injection into a laser driven plasma accelerator. An all-optical electron injector based on this approach could simplify timing and alignment in future laser-plasma accelerator experiments. PACS 41.75.Ht; 41.75.Lx; 52.38.Kd; 52.38.Ph     

Polarization of coherent synchrotron radiation from an electron beam rotating in a plasma

After eliminating reflections from the walls of the plasma container, we observed polarization of the coherent synchrotron radiation from a relativistic electron beam rotating in a plasma. Several features of the polarization agree well with calculations based on the single particle synchrotron radiation theory. A particular polarization ratio (Fig. 3) does not, however. We deduce from this direct diffraction of the radiation by the beam electrons. This is strong evidence for beam-particle bunches of size cm. Also, there must be some absorption of the extraordinary wave to account for the observations. We suggest a way to apply these results to measure the pitch angle of the beam.Work supported by Army Research Office.     

带电粒子束传输中横向发散的类ABCD定律

 傍轴近似下带电粒子束传输可完全类比于近轴光线椭圆高斯光束的传输。基于这种类比,建立了带电粒子束传输中横向发散的复曲率半径的类ABCD定律,引入了带电粒子在横向的复曲率半径的概念,并以复曲率半径的实部表征带电粒子束的敛散特性,虚部表征带电粒子束的束斑大小。由此提出：带电粒子束整体可被看作类椭圆高斯光束,其发射度与光束波长的作用相同。通过这种类比可知,在适宜的加速器环境下,理论上可能产生相干带电粒子束。     

Detecting cracks in a longitudinally vibrating beam with dissipative boundary conditions

This paper focuses on detecting a small open crack in an axially vibrating beam with viscous boundary conditions by using non-destructive dynamical measurements. The damage is simulated by an equivalent linear elastic spring. It is shown that the measurement of the changes in a suitable pair of eigenvalues leads to the solution of the diagnostic problem, namely identification of crack location and severity. Results apply to uniform beams under various sets of boundary conditions.     

Lateral displacements of a vibrating cantilever beam with a concentrated mass

The displacement equation for a uniform cross-section, cantilever-type beam carrying a concentrated mass at one end is solved under the most general conditions of an arbitrary distributed lateral load and arbitrary boundary and initial conditions. The method employs complex variable residue theory t0 determine the inversion integral for the Laplacetransformed solution of the boundary value problem. An example problem is solved and the displacement is shown graphically at several points along the beam for two values of the concentrated mass.     

Repelling of electron beam with local electron cyclotron resonance

Experimental results are presented for a repelling of electron beam drifting along an increasing magnetic field by the local electron cyclotron resonance with the non-uniform static magnetic and high frequency fields.     

Determination of the electron beam size at the Kurchatov synchrotron radiation source using an X-ray refractive lens

The electron beam size in the storage ring of the Kurchatov synchrotron radiation source at 2.5 GeV is determined using an x-ray two-dimensional parabolic refractive lens. The vertical size of the electron beam of the storage ring is found to be 270 μm, which exceeds the corresponding design value 140 μm (at a betatron coupling of 1%). The difference is explained by the imperfect geodetic arrangement of ring elements and the incomplete adjustment of the ring.     

Applications of focused ion beam for preparation of specimens of ancient ceramic for electron microscopy and synchrotron X-ray studies

In this paper the capabilities of FIB systems as a tool for TEM studies of ancient pottery are explored, especially when the amount of available material is very limited and when, for instance, there is stringent demand for very accurate location of the electron-transparent area as is the case for investigation of outer surface layers, such as slips and patinas. The advantages of the two main FIB milling techniques (H-bar and Lift-out) are discussed in detail and illustrated through the study of metallic lustre decorations and a particular type of Roman Terra Sigillata coating. The H-bar technique is ideal for investigations where the features of interest are near the edges of a ceramic fragment. A significantly large area of surface decoration can be studied without any restriction on the size and the shape of fragment. On the other hand, the Lift-out technique is very powerful for extracting TEM membranes far from the edges. An added advantage of this technique is that the thickness of the foil is very uniform and that allows large tilts and makes it possible to obtain electron diffraction patterns of several zones axes from the same crystal, making crystallographic phase identification easier and precise, and identification of complex structures possible. We also show that the FIB system can be used to deposit very precise registration marks, allowing an experimenter to correlate results from TEM measurements with other complementary techniques, such as synchrotron based microdiffraction and μXANES. Combination of these complementary techniques is becoming a very powerful approach to probe the chemical and morphological microstructure of heterogeneous and complex material from the nanometre to millimetre scale.     

Vircator with ballistic focusing of an electron beam

A high-power microwave oscillator (vircator) is built around an ironless induction linac. The feature of this device is ballistic focusing of an electron beam in a diode-type system with a concentric spherical cathode and anode. The possibility of the vircator to generate high-power microwave pulses is demonstrated.     

Free electron laser spectral dynamics with a modulation of electron beam energy

Recent experimental and theoretical works on free electron laser spectral dynamics have pointed out the difficulty to obtain a narrow and stable spectrum operation. This goal can only be achieved by avoiding the sideband generation leading to a broadband and unstable spectrum. Tapered wiggler and two-frequency wiggler are well suited for combining sharp spectrum and high efficiency but are not really compatible with a wide tunability of laser light. Filtering sidebands is a good way for lower power experiments but it seems to be difficult to conceive wideband filters, specially in the far-infrared region. Modulation of electron energy is a new potential soft way for controlling the spectral dynamics of longpulse free electron laser. Spectral dynamics under the modulation is investigated in the linear and non-linear regimes in the far-infrared region. Simulations show that a pulsed and sharp spectrum behavior can be obtained by optimizing the modulation parameters. The interest of such a method for the far-infrared experiments is discussed.