An intense positron pulse source at NEPOMUC

到目前为止，用正电子进行的实验使用的是低密度和高重复频率的连续光束或脉冲光束。在这里，我们建议使用最近开发的有效存储正电子的技术来建立一个容量前所未有的正电子陷阱。它将能够存储NEPOMUC光束线的主光束，并从这个IPPS(强正电子脉冲源)产生短的、非常强的正电子脉冲。正电子将被存储在一个圆柱形陷阱系统中，在这个系统中，正电子沿着超导电磁铁的场线传播，并另外受到静电势(彭宁-马尔姆伯格陷阱)的限制。该项目的目标是拥有10^12个颗粒的存储能力。为了实现这一数字，将使用几个Penning-Malmberg陷阱系统，这些陷阱围绕磁铁的中心轴径向布置。为了填充陷阱，正电子将在所谓的主单元中径向(垂直于场线)传输，横跨整个磁体直径。同样重要的是，我们将开发技术将目前由5mT的磁场引导的初级NEPOMUC束流注入存储单元(5T)的场中。为了做到这一点，正电子可以通过与中性背景气体(缓冲气体陷阱)的非弹性碰撞来减速和冷却。这样产生的非常冷的正电子可以被静电加速到更强的磁场中。或者，我们将探索将非常高能量的正电子直接注入5T场的途径，在那里它们将被金属重建器中的碰撞减慢。我们将首先开发这两种技术，以决定更有效的一种，最终将在我们的系统中实现。在我们的装置中产生的强烈、极短的正电子脉冲的应用特别是为了研究正电子与物质的相互作用。该项目是未来使用NEPOMUC专用装置使用正电子脉冲研究带电、被捕获的纳米粒子的一个明显的先决条件。第二个目标是生产第一个由电子和正电子组成的冷的、磁封闭的等离子体对。该项目对基础等离子体物理和天体物理同样重要，将是计划中的设备的第一次应用。进一步的研究目标是凝聚态物理学：这将是第一次有可能研究块状固体，在这种固体中，正电子不仅占据地面，而且由于其较高的密度，还占据激发态。

Experiments with positrons have so far used continuous beams or pulsed beams of low density and high repetition rate. Here we suggest to use recently developed techniques for efficient storage of positrons to build a positron trap of unprecedented capacity. It will enable to store the primary beam of the NEPOMUC beamline, and produce short, very intense positron pulses from this IPPS (Intense Positron Pulse Source).Positrons will be stored in a system of cylindrical traps in which positrons are travelling along the field lines of a superconducting electromagnet, and are additionally confined by electrostatic potentials (Penning- Malmberg trap). The project aims for a storage capacity of 10^12 particles. In order to achieve this figure, a system of several Penning-Malmberg traps will be used, that are radially arranged around the central axis of the magnet. To fill the traps, positrons will be transported radially (perpendicular to the fieldlines) in a so-called Master cell, spanning the whole diameter of the magnet.Equally important, we will develop techniques to inject the primary NEPOMUC beam, currently guided by a field of 5 mT, into the field of the storage cells (5 T). In order to do so, positrons can either be decelerated and cooled down by inelastic collisions with a neutral background gas ('buffer gas trap'). Very cold positrons produced such can then be accelerated electrostatically into the stronger magnetic field. Alternatively, we will explore the route of direct injection of very energetic positrons into the 5 T field, where they will be slowed down by collisions in a metallic remoderator. We will develop both techniques initially, in order to decide for the more efficient one, which will eventually be realized in our system.Applications for intense, extremely short positron pulses produced in our device are in particular for the investigation of positron-matter interaction. The project is an apparative pre-requisite for future research on charged, trapped nano-particles using positron pulses using a dedicated set-up at NEPOMUC. A second aim is the production of the first cold, magnetically enclosed pair plasma composed of electrons and positrons. This project, which is equally important for fundamental plasma physics as well as for astrophysics, will be the first application for the planned device. Further research aims are in condensed matter physics: For the first time, it will be possible to investigate bulk solids, in which positrons are occupying not only ground, but - because of their higher density - also excited states.