Development of Instrumentation for the Muon Ionization Cooling Experiment

这项提议是为Muon电离冷却实验(MICE)所需的仪器开发而提出的。在粒子物理领域，人们对使用粒子加速器来形成非常强的高能µ子束越来越感兴趣。介子发现于1937年，是电子质量更大的表亲，是一种亚原子粒子，它与物质的简单而广为人知的相互作用使其成为一种有用的探测器，具有一系列用途。然而，到目前为止，由于介子的平均寿命很短，只有2.2微秒，所以还不可能加速介子。论证Muon加速器可行性的关键步骤是Muon电离冷却实验(MICE)。加速高强度的µ子束的主要障碍是，这种束流产生的体积太大，无法放入同步加速器的典型真空室中，而且由于介子寿命短，几乎没有时间来充分收缩束流。电离冷却是一种快速收缩或“冷却”介子束的新技术。在这个过程中，一束µ子穿过精心挑选的材料，在材料中，它通过电离附近的原子而损失能量。这些相互作用降低了介子速度的所有三个分量：水平、垂直和纵向。然后，介子束被射频空腔加速，只替换了介子的纵向速度分量。由于水平分量和垂直分量越来越少，而纵向分量保持不变，µ子的轨迹变得更加平行，使得聚焦磁铁能够大幅减小光束的大小。在实践中，上述电离冷却过程因多种工程挑战而变得复杂。例如，光束必须包含在大体积、高场超导磁体中，能量吸收材料的原子必须是轻的(最好是氢原子)，这样才不会散射到盖过冷却效应的程度。小鼠的目标是建立一段电离-冷却通道，用仪器测量其冷却性能，并使用粒子加速器产生的µ子束来演示这项先进的加速器技术。MICE项目是来自欧洲、日本和美国的约150名物理学家和工程师共同努力的成果。MICE获得批准，并计划在英格兰的卢瑟福·阿普尔顿实验室运行。这项实验的估计成本为5000万美元，将由合作机构分摊。

This proposal is for instrumentation development needed for the Muon Ionization Cooling Experiment (MICE). In the field of particle physics, there is increasing interest in using particle accelerators to form very intense beams of high-energy muons. Discovered in 1937, the muon, a more massive "cousin" of the electron, is a subatomic particle whose simple and well-understood interactions with matter make it a useful probe for a range of purposes. Until now, however, due to its short average lifetime of 2.2 microseconds, it has not been possible to accelerate muons. The key step in demonstrating the feasibility of muon accelerators is the Muon Ionization Cooling Experiment (MICE). The main obstacle to accelerating an intense muon beam is that such beams are created too large to fit into the typical vacuum chamber of a synchrotron and the short muon lifetime leaves little time to adequately shrink the beam. Ionization cooling is a new technique to shrink, or "cool" a muon beam quickly. In this process, a beam of muons passes through carefully selected material in which it loses energy by ionizing nearby atoms. These interactions reduce all three components of a muon's velocity: horizontal, vertical, and longitudinal. The muon beam is then accelerated by radio-frequency cavities, replacing only the longitudinal velocity component of the muons. As the horizontal and vertical components are increasingly reduced while the longitudinal component is maintained, the muons' trajectories become more nearly parallel, allowing focusing magnets to substantially reduce the size of the beam.In practice, the ionization cooling process described above is complicated by multiple engineering challenges. For example, the beam must be contained in large-volume, high-field superconducting magnets, and the atoms of the energy absorbing material must be light (preferably hydrogen) so that the muons do not scatter so much as to overwhelm the cooling effect. The goal of MICE is to build a section of an ionization-cooling channel, instrument it to measure its cooling performance, and use a muon beam produced at a particle accelerator to demonstrate this advanced accelerator technique. The MICE project is a collaborative effort of some 150 physicists and engineers from Europe, Japan, and the US. MICE is approved and scheduled to run at England's Rutherford Appleton Laboratory. The $50 million estimated cost of the experiment is to be shared among the institutions of the collaboration.