基于束流位置探测器的束团长度测量

分析了驱动电子束团的频域特性,研究了基于该特性进行长度测量的理论基础;使用三维模拟软件对束流位置探测器(BPM)进行建模,用模拟的方法对传输阻抗进行了数值计算;对不同长度的束团进行了测量和计算,并且分析了束团位置在真空管道中偏移对束团长度测量的影响。由测量结果可见,电子束团长度在10~100 ps(3~30 mm)时,测量误差均小于2%,满足中国工程物理研究院高平均功率自由电子激光太赫兹实验测量的使用要求。     

基于束流位置探测器的束团长度测量

分析了驱动电子束团的频域特性,研究了基于该特性进行长度测量的理论基础;使用三维模拟软件对束流位置探测器(BPM)进行建模,用模拟的方法对传输阻抗进行了数值计算;对不同长度的束团进行了测量和计算,并且分析了束团位置在真空管道中偏移对束团长度测量的影响。由测量结果可见,电子束团长度在10~100 ps(3~30 mm)时,测量误差均小于2%,满足中国工程物理研究院高平均功率自由电子激光太赫兹实验测量的使用要求。     

Evaporative cooling of an atomic beam

We present a theoretical analysis of the evaporative cooling of an atomic beam propagating in a magnetic guide. Cooling is provided by transverse evaporation. The atomic dynamics inside the guide is analyzed by solving the Boltzmann equation with two different approaches: an approximate analytical ansatz and a Monte-Carlo simulation. Within their domain of validity, these two methods are found to be in very good agreement with each other. They allow us to determine how the phase-space density and the flux of the beam vary along its direction of propagation. We find a significant increase for the phase-space density along the guide for realistic experimental parameters. By extrapolation, we estimate the length of the beam needed to reach quantum degeneracy. Received 24 September 1999     

HIRFL-CSRm冷却束流寿命

实验研究了HIRFL-CSRm中电子冷却装置对C6+,Ar15+两种束流寿命的影响。首先,通过对比实验的测量确定电子冷却可以有效提高束流寿命;其次,探究了电子冷却装置中的各项参数（主要是电子束密度分布、流强、能量、绝热展开因子）是如何影响束流寿命的,通过改变电子束参数,测量束流寿命的变化趋势和规律,并且结合电子冷却相关理论对实验结果给予解释,最终通过实验优化和确定最佳的冷却装置参数,使束流在HIRFL-CSRm上获得了较高的寿命,从而提高HIRFL-CSRm束流累积过程中的流强增益。     

White light transverse cooling of a helium beam

We report a study of transverse laser cooling on a metastable helium beam using spectrally broadened diode lasers (“white light") to increase its flux. For this purpose, beam profile and atomic flux versus laser power and other parameters have been characterized. We have performed experiments to compare this technique with other transverse cooling methods using monochromatic light. Best results are obtained with a “ziz-zag" configuration using “white light". Received 21 December 1998 and Received in final form 27 May 1999     

局域中空光束中原子的强度梯度冷却

提出了一种采用蓝失谐局域中空光束实现中性原子冷却与囚禁的新方法，并采用Monte-Carlo模拟方法研究了局域中空光束中原子强度梯度冷却（即Sisyphus冷却）的 动力学过程. 研究发现一个温度约为5μK和密度为10^12—10^13cm^3的超冷原子样品可以在我们的单束局域中空光束势阱中获得，而且这一原子密度可通过改变聚焦系统的相对孔径来加以调控. 因此，这一蓝失谐的局域中空光束还可用于实现全光型玻色-爱因斯坦凝聚. 关键词： 局域中空光束 原子囚禁 强度梯度冷却     

HIRFL-CSRm冷却束流寿命

实验研究了HIRFL-CSRm中电子冷却装置对C6+,Ar15+两种束流寿命的影响。首先,通过对比实验的测量确定电子冷却可以有效提高束流寿命;其次,探究了电子冷却装置中的各项参数（主要是电子束密度分布、流强、能量、绝热展开因子）是如何影响束流寿命的,通过改变电子束参数,测量束流寿命的变化趋势和规律,并且结合电子冷却相关理论对实验结果给予解释,最终通过实验优化和确定最佳的冷却装置参数,使束流在HIRFL-CSRm上获得了较高的寿命,从而提高HIRFL-CSRm束流累积过程中的流强增益。     

Longitudinal focusing and cooling of a molecular beam

A neutral polar molecule experiences a force in an inhomogeneous electric field. This electric field can be designed such that a beam of polar molecules is exposed to a harmonic potential in the forward direction. In this potential the longitudinal phase-space distribution of the ensemble of molecules is rotated uniformly. This property is used to longitudinally focus a pulsed beam of ammonia molecules and to produce a beam with a longitudinal velocity spread of 0.76 m/s, corresponding to a temperature of 250 mu K.     

HLS横向反馈系统研制中的关键技术

较为全面地介绍了合肥光源横向模拟反馈系统研制过程中,所涉及的部分关键问题,如矢量运算模块的开发,Notch滤波器研制,基于Hilbert变换进行相空间重建、模式分析,反馈Kicker腔的研制.     

强流电子束引出窗风冷数值模拟

研究了1.2 MW大功率电子加速器引出窗钛膜受力状况,确定其工作温度必须控制在150 ℃以内。此温度下,热传导和热辐射的散热作用可以忽略,强迫风冷是唯一的散热途径。用流体模拟计算软件分析了钛膜冷却效果与出口风速和距离之间的关系,分析回流区的存在及其影响,并对引出窗结构做了初步优化。模拟了附加隔离窗形成的封闭空间对引出窗风冷的影响,模拟结果为：提出的非均布扫描方式可以将引出窗输出能力提升76%。     

一维晶化束的辐射能损与束流冷却

 用Jacobian椭圆函数求解了一维晶化束的非线性动力学方程，并用第一类全椭圆积分表示了粒子振动周期。在经典物理学框架内，讨论了储存环中作相对论运动的带电粒子的辐射能损，以及由于辐射能损导致的束流冷却。结果表明, 由于辐射损失束流将进一步冷却。     

HLS横向反馈系统研制中的关键技术

较为全面地介绍了合肥光源横向模拟反馈系统研制过程中, 所涉及的部分关键问题, 如矢量运算模块的开发, Notch滤波器研制, 基于Hilbert变换进行相空间重建、模式分析, 反馈Kicker腔的研制.     

Measurement of laser light thomson-scattered from a cooling electron beam

First results are presented from an experiment scattering laser light from a relativistic electron beam. The 5 cm diameter continuous electron beam of 28 keV kinetic energy and 2.6 A current presents an electron gas of a density of 8×10⁷ cm^–3, from which 20 ns pulses of laser light (490 nm) were scattered at a repetition rate of 15 Hz and an average power of 20 mJ per pulse. The Doppler-shifted wavelength of photons backscattered under 180° was analysed with a Fabry-Perot interferometer. This technique provides, for the first time, a non-destructive measurement of the velocity distribution in an electron beam radially resolved in space. The results presented here comprise the direct measurement of the absolute electron energy and the degree of space-charge compensation in the electron beam. The determination of an upper bound of 10^–2 for the ratio of longitudinal to transverse electron temperature implies the first direct measurement of a flattened velocity distribution.     

一维晶化束的辐射能损与束流冷却

用Jacobian椭圆函数求解了一维晶化束的非线性动力学方程,并用第一类全椭圆积分表示了粒子振动周期。在经典物理学框架内,讨论了储存环中作相对论运动的带电粒子的辐射能损,以及由于辐射能损导致的束流冷却。结果表明, 由于辐射损失束流将进一步冷却。     

Incoherent vertical ion losses during multiturn stacking cooling beam injection

The efficiency of the multiturn ion injection with electron cooling depends on two parameters, namely, cooling efficiency and ion lifetime. The lifetime of freshly injected ions is usually shorter than the lifetime of strongly cooled stacked ions. Freshly injected ions are lost in the vertical direction because the vertical acceptance of the synchrotron is usually a few times smaller than the horizontal acceptance. Incoherent vertical losses of freshly injected ions arise from their multiple scattering by residual gas atoms and transverse diffusion caused by stack noise. Reduced ion lifetime limits the multiturn injection efficiency. Analytical estimations and BETACOOL-based numerical evaluations of the vertical ion losses during multiturn injection are presented in comparison with the experimental data obtained at the HIMAC synchrotron and the S-LSR storage ring.     

多束团不稳定性的模拟研究

利用模拟的方法研究了多束团不稳定性.SCBI程序(SIMULATION OF COUPLED-BUNCH INSTABILITIES)是一个用来模拟研究储存环上高频腔、真空盒内壁及其它腔形结构元件的长程尾场和中程尾场激发的多束团不稳定性的综合程序.在束团均匀分布情形下,比较了SCBI程序与ZAP程序的结果,两者非常一致.同时,利用SCBI程序对北京正负电子对撞机(BEPC)多束团改进方案(BEPCⅡ)的多束团不稳定性进行了详细的研究.     

Buffer-gas cooling of NH via the beam loaded buffer-gas method

NH radicals from a molecular beam are cooled using a novel beam-loaded buffer gas method. The radicals are produced in a glow discharge beam source and injected into cryogenic helium gas. Up to 10¹² molecules in their ground electronic, vibrational, and rotational state are detected in the buffer gas and translational temperatures under 6 K are achieved. The cooling method presented is general and can be applied to any molecules in a molecular beam.Received: 20 July 2004, Published online: 26 October 2004PACS: 33.80.Ps Optical cooling of molecules; trapping - 34.50.Ez Rotational and vibrational energy transfer - 39.10. + j Atomic and molecular beam sources and techniquesB. Friedrich: Present address: Department of Molecular Physics, Fritz-Haber-Institut der Max-Planck-Gesellschaft, Berlin, Germany.     

北京正负电子对撞机束团拉伸效应研究

本文叙述了在北京正负电子对撞机(BEPC)上,用条纹相机和频谱分析方法对束团拉伸效应的研究.由测量结果归纳出BEPC束团拉伸效应的标度规律,这一规律与理论分析有相当好的一致关系.