感应同步加速器束团粒子纵向运动数值模拟

依据感应同步加速器验证实验中的相关数据,编写程序,实现了对感应同步加速中粒子纵向动力学过程的数值模拟。针对引起加速初期束团粒子大量丢失的多个可能因素进行了计算分析,明确了各因素对粒子丢失的影响方式和程度。以此为基础,提出了通过大幅减小加速腔体积并同时增加加速腔数量的方式来解决感应同步加速电压幅度实时调节困难的可行性建议,为感应同步加速器的性能提升提供了参考。     

DTL cavity design and beam dynamics for a TAC linear proton accelerator

A 30 mA drift tube linac (DTL) accelerator has been designed using SUPERFISH code in the energy range of 3-55 MeV in the framework of the Turkish Accelerator Center (TAC) project. Optimization criteria in cavity design are effective shunt impedance (ZTT), transit-time factor and electrical breakdown limit. In geometrical optimization we have aimed to increase the energy gain in each RF gap of the DTL cells by maximizing the effective shunt impedance (ZTT) and the transit-time factor. Beam dynamics studies of the DTL accelerator have been performed using beam dynamics simulation codes of PATH and PARMILA. The results of both codes have been compared. In the beam dynamical studies, the rms values of beam emittance have been taken into account and a low emittance growth in both x and y directions has been attempted.     

Beam steering correction of the quarter wave resonator in the HISCL

The Intensity Heavy Ion Superconducting Linear Accelerator as the injector of the High Intensity Heavy-Ion Accelerator Facility, which is a new project proposed in China has been designed. One of the design options in the low energy part is based on Quarter Wave Resonators (QWRs). However, because of the unsymmetrical geometry of the cavity, there are dipole fields near the beam hole, which may steer the beam vertically, thus leading to emittance growth and beam loss. The effect of the dipole mode field is analyzed, and a method to overcome the beam steering effect by placing QWRs with opposite orientation is proposed in this paper. The simulation results show that the beam steering effect is reduced effectively by this method, and the deviation of the beam centroid is decreased from 2.87 mm to 0.1 mm. The emittance growth is also smaller.     

Instrumental design and expected performance of coupled-moderator near-backscattering spectrometer at J-PARC

A near-backscattering (n-BS) crystal-analyzer neutron inelastic spectrometer, DIANA, has been proposed for construction at Japan Proton Accelerator Research Complex. It has originally been designed to view a decoupled non-poisoned moderator in order to obtain high intensity and good energy resolution. Recently, we have reconsidered the instrumental parameters including the type of moderator, by performing Monte-Carlo simulations in order to obtain better performance. Among four virtual n-BS spectrometers on different beam sources moderators, a coupled-moderator-source spectrometer has shown the best performance, i.e. compared to the original DIADA design between ninefold and fivefold enhanced intensities have been obtained with 21%-better to 35%-worse energy resolutions.     

Improvement in performance and operational experience of 14 UD Pelletron accelerator facility, BARC-TIFR

14 UD Pelletron Accelerator Facility at Mumbai has been operational since 1989. The project MEHIA (medium energy heavy ion accelerator) started in 1982 and was formally inaugurated on 30th December 1988. Since then the accelerator has been working round the clock. Improvement in accelerator performance and operational experience are described.     

Multifarious injection chamber for molecular structure study (MICOSS) system: development and application for serial femtosecond crystallography at Pohang Accelerator Laboratory X‐ray Free‐Electron Laser

The multifarious injection chamber for molecular structure study (MICOSS) experimental system has been developed at the Pohang Accelerator Laboratory X‐ray Free‐Electron Laser for conducting serial femtosecond crystallography. This system comprises several instruments such as a dedicated sample chamber, sample injectors, sample environment diagnostic system and detector stage for convenient distance manipulation. Serial femtosecond crystallography experiments of lysozyme crystals have been conducted successfully. The diffraction peaks have reached to ～1.8 Å resolution at the photon energy of 9.785 keV.     

Study on the HOMs coupler design of spoke cavity

The superconducting spoke cavity has been proposed to accelerate the proton in the low energy section of high power proton linac for an Accelerator Driven Sub-critical System (ADS).Considering that the High Order Modes (HOMs)in the superconducting cavity have far reaching influence on power dissipation and beam stability,the analysis of HOMs of the spoke cavity is needed.In this paper,we put emphasis on the analysis of HOMs of the spoke cavity and the HOMs coupler design.     

Simultaneous acceleration of multiply charged ions through a superconducting linac

The possibility of simultaneously accelerating particles with a range of charge-to-mass ratios ( approximately 20%) to the same energy is proposed and demonstrated for a superconducting linac. Uranium ions stripped in a foil with eight charge states have been accelerated through a portion of the ATLAS linac from 286 to 690 MeV, with 94% of the injected uranium in the accelerated beam. Emittance of the resultant beam has been measured and the energy spread was 1.3% compared to 0.4% for a single charge state. This development has immediate application to the high-intensity acceleration of heavy ions that are limited by ion-source intensities, such as the proposed Rare Isotope Accelerator Facility.     

Study on the HOMs coupler design of spoke cavity

The superconducting spoke cavity has been proposed to accelerate the proton in the low energy section of high power proton linac for an Accelerator Driven Sub-critical System (ADS). Considering that the High Order Modes (HOMs) in the superconducting cavity have far reaching influence on power dissipation and beam stability, the analysis of HOMs of the spoke cavity is needed. In this paper, we put emphasis on the analysis of HOMs of the spoke cavity and the HOMs coupler design.     

Rydberg states of HCN observed by electron impact spectroscopy

The electron energy loss spectrum of HCN has been determined in the energy region 8–13.6 eV at impact energies of 100, 50 and 30 eV. It is shown that energy loss spectra of HCN at intermediate impact energies can be satisfactorily analysed unlike the diffuse unassigned optical absorption spectra that have previously been reported. Rydberg series have been assigned using term values and quantum defects together with ionization potentials obtained by photoelectron spectroscopy.     

an Introduction to Mebt For JKJ and Its Upgrade Design

The medium-energy beam-transport line (MEBT) plays an important role in reducing the beam loss in the Japan Proton Accelerator Research Complex (J-PARC). A MEBT was designed and constructed,with good beam matching and lower beam loss. A brief introduction to the MEBT and its beam test results are given. To further reduce the beam loss during the transient time of the chopper,a medium-energy beamtransport line with an anti-chopper has been designed. It accomplishes three tasks: matching the beam from the RFQ to the acceptance of the DTL, chopping the beam to produce gaps for injection into the rapid cycling ring which follows the linac, and returning the partially deflected beam back to the acceptance of the DTL. An RF chopper and an anti-chopper have been adopted in the beam line, and the optimization of the design of the chopper cavity is discussed. Details of the beam dynamics analysis are given.     

类铍硫n=2的某些能级寿命的实验研究

主要报导用束箔技术对天体等离子体中重要元素硫的高电离态原子n =2的某些能级寿命的实验测量.实验数据用CANDY程序分析 ,并与理论计算结果和其它的实验结果作了比较. Lifetime measurement has been carried out for some low lying n=2 levels in the four electron ions S ⅩIII by using the beam-foil technique at National Laboratory of Heavy Ion Accelerator, Lanzhoiu, China. Spectra of highly ionized sulfur obtained at an energy of 2.5 MeV/nucleon have been studied in the 190-530  wavelength range. Experimental decay curves are analysized by the CANDY program, and compared with theoretical calculations and experimental measureaments.     

Electron energy loss spectra of the system Cu(311)/CO,Xe

The electron energy loss spectrum of a clean Cu(311) surface has been studied by reflected electrons using primary energies between 30 and 300 eV. The losses obtained are compared with literature values. Loss spectra with adsorbed CO and Xe are also reported. Some assignments of the loss mechanisms have been attempted.     

Inelastic scattering of He atoms from a Cu(110) surface

A He beam has been used to measure inelastic scattering from a Cu(110) surface. The scattering was a result of predominantly single phonon events and both energy gain and loss processes were observed. This was in contrast to Cu(001) where only energy loss was observed. For Cu(110), aligned in the [001] azimuth, partial dispersion relations have been measured which meant that phonons with ΔQ values up to the zone boundary value have not been detected under the present experimental conditions. The elastic incoherent component varied with azimuthal angle for Cu(110).     

JAERI和KEK联合项目中的中能束流传输线及其升级设计

中能束流传输线(MEBT)在日本质子加速器研究设施(J-PARC)中对控制束流损失起到非常关键的作用. 中能传输线已经成功设计和建造, 并进行了束流实验. 简要介绍了中能传输线及其束流实验的结果. 为进一步减少和消除传输线中的束流切割器的上升和下降过程中产生的不稳定粒子, 以满足更高流强下的束损要求, 给出了一个带有反束流切割器的中能传输线的升级设计, 该设计已被用作该项目的备用方案. 升级设计的中能传输线要完成三个任务：完成从RFQ到DTL的束流相空间匹配; 利用束流切割器把束流切割成注入快循环时所需要的束流结构, 以及利用反束流切割器把束流切割器上升和下降时间段产生的部分偏转的不稳定粒子作用回DTL的相空间接收度内, 以减少和避免粒子丢失. 在该中能传输线中, RF偏转器被用来作为束流切割器和反束流切割器. RF偏转器是中能传输线中最关键的部件, 进一步讨论了RF偏转器作为反束流切割器的优化设计. 也给出了该传输线的动力学分析的结果.     

The atomic structure and the properties of ununbium (<Emphasis Type="Italic">Z</Emphasis> = 112) and Mercury (<Emphasis Type="Italic">Z</Emphasis> = 80)

A super heavy element Uub (Z = 112) has been studied theoretically in conjunction with rela-tivistic effects and the effects of electron correlations. The atomic structure and the oscillator strengths of low-lying levels have been calculated, and the ground states have also been determined for the singly and doubly charged ions. The influence of relativity and correlation effects to the atomic properties of such a super heavy element has been investigated in detail. The results have been compared with the properties of an element Hg. Two energy levels at wave numbers 64470 and 94392 are suggested to be of good candidates for experimental observations.     

Study on the Lorentz detuning and tuning of β=0.3, 352 MHz spoke cavity

The superconducting spoke cavity has been proposed to accelerate the proton in the low energy section of the high power proton linac for the Accelerator Driven Sub-critical System in China. In this paper, the basic geometric and RF parameters of a β=0.3, 352 MHz spoke cavity are given, and the Lorenz detuning and tuning are presented.     

Development of fundamental power coupler for C-ADS superconducting elliptical cavities

5-cell elliptical cavities have been selected for the main linac of the China Accelerator Driven subcritical System(C-ADS) in the medium energy section. According to the design, each cavity should be driven with radio frequency(RF) energy up to 150 kW by a fundamental power coupler(FPC). As the cavities work with high quality factor and high accelerating gradient, the coupler should keep the cavity from contamination in the assembly procedure. To fulfil the requirements, a single-window coaxial type coupler was designed with the capabilities of handling high RF power, class 10 clean room assembly, and heat load control. This paper presents the coupler design and gives details of RF design, heat load optimization and thermal analysis as well as multipacting simulations. In addition, a primary high power test has been performed and is described in this paper.     

Dielectric properties of EuF2

Dielectric constant (?) and loss (tan δ) of EuF₂ have been measured for the first time as a function of frequency in the temperature range from liquid nitrogen to 300°C. The data has been used to obtain the values of conductivity (σ). The conductivity values are frequency independent in the high temperature region and yield 1.05 eV for the activation energy for conduction.     

Recent results on few-nucleon systems: Investigation from VBLHE-JINR

Recent results on the spin effects in deuteron inclusive breakup and deuteron-proton elastic scattering obtained at the Veksler and Baldin Laboratory of High Energies at JINR are reported. The experimental data have been obtained with the use of a high-energy polarized deuteron beam at the Synchrophasotron-Nuclotron Accelerator Complex. The covered energy range corresponds to the short internucleonic distances where the relativistic effects and non-nucleonic degrees of freedom can play a significant role.