Development of Instrumentation for the Muon Ionization Cooling Experiment

该建议是为μ子电离冷却实验（MICE）所需的仪器开发。 在粒子物理学领域，人们对使用粒子加速器来形成非常强的高能μ子束的兴趣越来越大。1937年发现的μ子是电子的一个更大质量的“表亲”，是一种亚原子粒子，它与物质的简单和良好的相互作用使其成为一系列用途的有用探针。然而，到目前为止，由于其平均寿命仅为2.2微秒，因此无法加速μ子。 证明μ子加速器可行性的关键步骤是μ子电离冷却实验（MICE）。加速强烈的μ子束的主要障碍是，这样的光束太大而不能放入同步加速器的典型真空室，并且短的μ子寿命几乎没有时间来充分收缩光束。电离冷却是一种快速收缩或“冷却”μ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，通过电离附近的原子而失去能量。这些相互作用降低了μ子速度的所有三个分量：水平，垂直和纵向。然后，μ子束被射频腔加速，只取代μ子的纵向速度分量。当水平和垂直分量逐渐减小而纵向分量保持不变时，μ子的轨道变得更加接近平行，从而允许聚焦磁体大幅减小束流的尺寸。在实践中，上述电离冷却过程因多个工程挑战而变得复杂。例如，束流必须包含在大体积的高场超导磁体中，能量吸收材料的原子必须是轻的（最好是氢），这样μ子就不会散射得太多，以至于压倒了冷却效果。MICE的目标是建立一个电离冷却通道的一部分，测量其冷却性能，并使用粒子加速器产生的μ子束来演示这种先进的加速器技术。 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的合作成果。 MICE获得批准，并计划在英国卢瑟福阿普尔顿实验室运行。试验的5 000万美元估计费用将由合作机构分摊。

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.