Commissioning of electron cooling in CSRe

The 400 MeV/u 12C6＋ ion beam was successfully cooled by the intensive electron beam near 1 A in CSRe.The momentum cooling time was estimated near 15 s.The cooling force was measured in the cases of difierent electron beam profiles,and the difierent angles between the ion beam and electron beam.The lifetime of the ion beam in CSRe was over 80 h.The dispersion in the cooling section was confirmed as positive close to zero.The beam sizes before cooling and after cooling were measured by the moving screen.The beam diameter after cooling was about 1 mm.The bunch length was measured with the help of the signals from the beam position monitor.The difiusion was studied in the absence of the electron beam.     

Commissioning of electron cooling in CSRm

A new generation electron cooler has started operation in the heavy ion synchrotron CSRm which is used to increase the intensity of heavy ions. Transverse cooling of the ion beam after horizontal multi-turn injection allows beam accumulation at the injection energy. After optimization of the accumulation process an intensity increase in a synchrotron pulse by more than one order of magnitude has been achieved. In given accumulation time interval of 10 seconds, 108 particles have been accumulated and accelerated to the final energy. The momentum spread after accumulation and acceleration in the 10-4 range has been demonstrated in six species of ion beams. Primary measurements of accumulation process varying with electron energy, electron beam current, electron beam profile, expansion factor and injection interval have been performed. The lifetimes of ion beams in the presence of electron beams were roughly measured with the help of DCCT signal.     

Commissioning of electron cooling in CSRm

A new generation electron cooler has started operation in the heavy ion synchrotron CSRm which is used to increase the intensity of heavy ions. Transverse cooling of the ion beam after horizontal multi-turn injection allows beam accumulation at the injection energy. After optimization of the accumulation process an intensity increase in a synchrotron pulse by more than one order of magnitude has been achieved. In given accumulation time interval of 10 seconds, 10⁸ particles have been accumulated and accelerated to the final energy. The momentum spread after accumulation and acceleration in the 10^－4 range has been demonstrated in six species of ion beams. Primary measurements of accumulation process varying with electron energy, electron beam current, electron beam profile, expansion factor and injection interval have been performed. The lifetimes of ion beams in the presence of electron beams were roughly measured with the help of DCCT signal.     

Secondary electron time detector for mass measurements at CSRe

The Isochronous Mass Spectrometry is a high accurate mass spectrometer. A secondary electrons time detector has been developed and used for mass measurements. Secondary electrons from a thin carbon foil are accelerated by an electric field and deffected 180° by a magnetic field onto a micro-channel plate. The time detector has been tested with alpha particles and a time resolution of 197 ps (FWHM) was obtained in the laboratory. A mass resolution around 8×10-6 for m/m was achieved by using this time detector in a pilot mass measurement experiment.     

HIRFL-CSR电子冷却系统空心电子束性能研究

电子冷却系统中冷却力的大小与电子束的温度密切相关。由于强流电子束自身产生的空间电荷场,使得电子束的速度离散,增加了电子束温度,降低了冷却效率。为了减小空间电荷效应,HIRFL CSR的电子冷却系统将首次采用空心电子束对储存环中的重离子束流进行冷却。通过分析实心电子束和空心电子束的空间电荷场,研究了其对电子束速度和温度的影响。     

Secondary electron time detector for mass measurements at CSRe

The Isochronous Mass Spectrometry is a high accurate mass spectrometer. A secondary electrons time detector has been developed and used for mass measurements. Secondary electrons from a thin carbon foil are accelerated by an electric field and deflected 180°by a magnetic field onto a micro-channel plate. The time detector has been tested with alpha particles and a time resolution of 197 ps （FWHM） was obtained in the laboratory. A mass resolution around 8×10^-6 for Am/m was achieved by using this time detector in a pilot mass measurement experiment.     

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     

CSRe减速模拟

对兰州重离子加速器冷却储存环实验环中束流的减速过程进行了模拟研究,采用变换谐波的方式将粒子减速到较低能量,以适应高精度原子物理实验的需要.根据模拟结果得到了减速过程各个时刻粒子在纵向相空间分布,并给出了高频参数在减速过程中的变化曲线.     

Low-energy electron beam source

Experimental results of research into a ferroelectric-plasma-source-assisted hollow anode (HA) discharge as a source of low-energy electron beams are presented. To generate electron beams, the HA auto-bias negative voltage was achieved by the discharge current flowing through the resistor connecting the HA and the grounded electrode. It is shown that this method allows reliable and reproducible generation of low-energy electron beams with electron energy of several hundreds of eV, electron current density up to several A/cm² and pulse duration of several tens of microseconds.     

Design of a new pseudospark-produced high-brightness electron beam source

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兰州重离子加速器冷却储存环中电子冷却性能

为了在兰州重离子加速器冷却储存环(HIRFL-CSR)上开展一维离子束序化的研究,在CSR主环上,对6.39 MeV/u的58Ni19+离子束进行了冷却累积实验。测量了离子束与电子束之间不同的水平、垂直夹角以及不同电子束剖面的情况下,束流累积及束流寿命变化情况;重点研究了离子束衰减过程中动量分散随离子数的变化规律,拟合计算得到了动量分散随离子数按照幂函数衰减的指数;在给定离子数的情况下,动量分散随夹角、电子束剖面的依赖关系,为下一步在CSR上获得纵向一维有序化离子束的研究做准备。在实验中观测到在较大的夹角情况下,离子束出现纵向振荡和中心频率移动。     

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。     

CSRe电子冷却模式下核质量测量研究

研究了CSRe电子冷却模式下使用线性质量刻度时, 空间电荷效应对测量精度的影响、 CSRe上测量190Ir质量的实验可行性以及估算了电子冷却模式下, 使用非线性刻度法所能达到的测量精度。 理论上的分析表明, CSRe在束流和二极铁磁场稳定的理想情况下, 如果电子冷却对同种离子束的冷却效果能达到δp/p=10－6量级, 采用非线性刻度的方法, 能够对像190Ir这样的重离子达到σ(m)/m≈10-8的测量精度。 Nuclear mass measurement by electron cooling mode in CSRe is discussed, mainly in three related aspects: the systematic error caused by the space charge effect in the case of linear mass calibration; the possibility of mass measurement of 190 Ir in CSRe; the estimation of the attainable precision in the case of non linear mass calibration. Theoretic analysis of the attainable precision shows that a precision of σ(m)/m≈10-8 can be achieved if the momentum spread of each kind of ions can be reduced to 10-6 in CSRe.     

HIRFL-CSR实验环电子冷却装置磁场测量

在HIRFL-CSR实验环电子冷却装置上采用了独立的高精度螺线管串联产生纵向磁场的设计,获得很高的冷却段磁场平行度。使用霍尔片测量磁场的分布,使用磁针测磁方法测量冷却段磁场的磁轴偏角,并根据测量及计算结果对单个线圈磁轴进行微调。测量及调试结果表明,在施加电流为额定电流的一半时,冷却段磁感应强度为0.078 T,剩余磁场小于2×10-4 T,磁场不平行度小于1×10-4,达到了预期的设计目标。     

小型空心阴极等离子体电子枪实验

基于空心阴极效应和低压辉光放电原理,设计了一种小型空心阴极等离子体电子枪并进行了实验研究,在低气压下获得了稳定的空心阴极辉光放电,测量电子枪放电结果表明：在空心阴极中加入灯丝热子可明显降低放电气压;电子束电流的大小随放电电压增大而增大,受气体气压影响较小;在气压2 Pa,放电电压10 kV,脉宽4 μs脉冲下放电,可得到脉宽为2 μs,电流为600 mA的电子束。     

小型空心阴极等离子体电子枪实验

基于空心阴极效应和低压辉光放电原理,设计了一种小型空心阴极等离子体电子枪并进行了实验研究,在低气压下获得了稳定的空心阴极辉光放电,测量电子枪放电结果表明:在空心阴极中加入灯丝热子可明显降低放电气压;电子束电流的大小随放电电压增大而增大,受气体气压影响较小;在气压2Pa,放电电压10kV,脉宽4μs脉冲下放电,可得到脉宽为2μs,电流为600mA的电子束。     

电子束在弯曲螺线管中的运动

为研究HIRFL-CSR电子冷却装置中电子束穿过电子冷却装置中弯曲螺线管后电子横向能量的变化,用POISSON程序计算出弯曲螺线管的磁场分布,考虑了空间电荷效应,用数值方法模拟计算了电子在弯曲螺线管中的运动情况,得到了电子束横向能量变化最小时磁场各分量与电子束能量和弯曲螺线管几何尺寸之间的关系,并获得了电子束横向能量在束流截面的空间分布。     

亚微米局域空心光束的产生及其在单原子囚禁与冷却中的应用理论研究

提出了一种采用单模光纤、环形二元相位板和微透镜组成的光束整形系统产生亚微米局域空心光束的方案. 根据瑞利-索莫菲衍射积分公式, 数值计算了微透镜焦平面附近的场分布, 详细研究了空心光束的暗斑尺寸与单模光纤模场半径和微透镜焦距的关系. 数值计算结果表明: 在微透镜焦平面附近光场分布近似对称, 在焦点处场强近似为零, 周围场强逐渐增大, 形成半径约为0.4 μm的三维封闭的球形空心光场区域, 即亚微米局域空心光束. 当局域空心光束为蓝失谐时, 光场中的原子将被囚禁在光场最弱处. 若加上抽运光, 原子将受到蓝失谐局域空心光束与抽运光共同激发的强度梯度Sisyphus冷却. 本文利用该方案产生的亚微米局域空心光束构建单原子的囚禁与冷却器件, 并以单个⁸⁷Rb原子为例, 利用Mont-Carlo方法研究亚微米局域空心光束中单原子囚禁与强度梯度冷却的动力学过程, 结果表明利用该器件可以获得温度在5.8 μK量级的超冷单原子.     

HIRFL-CSR电子冷却系统空心电子束性能研究

 电子冷却系统中冷却力的大小与电子束的温度密切相关。由于强流电子束自身产生的空间电荷场,使得电子束的速度离散,增加了电子束温度,降低了冷却效率。为了减小空间电荷效应,HIRFL CSR的电子冷却系统将首次采用空心电子束对储存环中的重离子束流进行冷却。通过分析实心电子束和空心电子束的空间电荷场,研究了其对电子束速度和温度的影响。     

电子束在弯曲螺线管中的运动

 为研究HIRFL-CSR电子冷却装置中电子束穿过电子冷却装置中弯曲螺线管后电子横向能量的变化,用POISSON程序计算出弯曲螺线管的磁场分布,考虑了空间电荷效应,用数值方法模拟计算了电子在弯曲螺线管中的运动情况,得到了电子束横向能量变化最小时磁场各分量与电子束能量和弯曲螺线管几何尺寸之间的关系,并获得了电子束横向能量在束流截面的空间分布。