Electron cooling: Theory, experiment, application
Electron cooling: Theory, experiment, application
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DOI：
10.1016/0370-1573(90)90040-9
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发表时间：
1990-11
期刊：
影响因子：
--
通讯作者：
H. Poth
中科院分区：
文献类型：
--
作者：
H. Poth
由于刘维尔定理的结果，带电粒子束中的动量扩散和发射度不能用离子光学来减小。这限制了圆形机器中可以加速或减速的离子的数量，进而限制了可用于实验的强度和光度。电子冷却可以克服这一障碍。电子冷却的机理相当于等离子体中的温度弛豫，等离子体由冷和热组成。电子冷却最初是为了积累反质子而提出的，但现在它的应用主要是改进用于原子和核物理精密实验的轻离子束和重离子束。电子冷却减少了纵向和横向离子速度的扩散，这意味着离子束的动量扩散、直径和发散减少。达到均衡所需的时间通常是秒的量级。在有利的条件下，电子和离子之间可以达到热平衡，从而产生非常高的相空间密度。因此，更强、更明亮的大范围离子束可以被输送到原子、核能和中能物理实验中。冷却束也提供了一个干净的、自由电子的靶子，这对原子物理来说特别有趣。对电子冷却的理解--无论是理论上还是实验上--现在已经达到了这样的水平，只有几个问题需要回答，几个疑虑需要消除。本文试图对这一主题进行全面的报道，并对现有的知识进行总结。讨论了该方法未来可能的发展和改进，以及合并的平行束排列在原子物理中的应用。
As a consequence of Liouville's theorem, the momentum spread and the emittance in charged-particle beams cannot be reduced by means of ion optics. This limits the number of ions that can be accelerated or decelerated in a circular machine and, in turn, the intensity and luminosity availab le for experiments. Electron cooling can overcome this obstacle. The mechanism underlying electron cooling is equivalent to that of temperature relaxation in a plasma consisting of a hot and a cold component. Initially electron cooling was proposed for the accumulation of antiprotons, but today its application is found mainly in the improvement of light- and heavy-ion beams to be used for precision experiments in atomic and nuclear physics.Electron cooling reduces the spread in the longitudinal and transverse ion velocities, which means a decrease in the momentum spread, in the diameter, and in the divergence of the ion beam. The time that elapses until equilibrium is reached is usually of the order of seconds. Under favourable conditions, thermal equilibrium between electrons and ions can be obtained, yielding very high phase-space densities. Consequently, more intense and brilliant beams of a wide range of ions can be delivered to atomic, nuclear and intermediate-energy physics experiments. The cooling beam provides also a clean, free-electron target, and this is especially interesting for atomic physics.The understanding of electron cooling - both theoretically and experimentally - has now reached such a level that there are only a few questions still to be answered and a few doubts to be removed. This article attempts to give a comprehensive coverage of the subject and summarizes the present knowledge. Possible future developments and refinements of the method are discussed, as well as the application of the merged parallel-beam arrangement for atomic physics.