Collaborative Research: Muon Ionization Cooling Experiment

研究和开发高光度介子对撞机是提高加速器性能的一项重要活动。在考虑下一步可能的高能物理设施时，μ子与电子和质子相比具有重要的特性。由于与电子相比，μ子的辐射受到很大的抑制，因此考虑在TeV能量范围内为μ子设计一个相对紧凑的圆形对撞机是可行的。然而，像电子一样，μ子是一个点粒子，因此可以探索与质子相同的物理机制，其能量大约是质子的十倍。因此，在过去的几年里，介子对撞机吸引了越来越多的兴趣。由于μ介子是一种不稳定的粒子，因此在人们能够自信地说这种装置能够工作之前，需要对加速器物理和技术的许多新方面进行研究。国际μ子电离冷却实验（International Muon Ionization Cooling Experiment， MICE）是首次观测μ子电离冷却的高能物理实验。这种冷却是制造介子对撞机的必要步骤。冷却是一个过程，通过减少光束的发射度来减小光束的尺寸，这样更多的μ子可以在更小的孔径加速器和更少的聚焦磁铁中加速。这可能使高强度μ子加速器的建设成为可能，例如中微子工厂或μ子对撞机，它们可能比电子-正电子对撞机获得更高的能量。寻找冷却μ子方法的研究人员设计了MICE实验来测试一种称为电离冷却技术的有效性。电离冷却发生在介子通过吸收体时，它们因电离能损失而失去动量。然后它们在直线加速器中被重新加速，在那里它们的能量只在前进方向上被恢复。MICE将使用单个粒子束，每10纳秒通过探测器的介子不超过一个。实验需要平衡能量损失带来的冷却和μ子多次散射带来的加热。μ子电离冷却实验将使用卢瑟福阿普尔顿实验室（RAL）新建的低能μ子束对μ子电离冷却进行详细测量。该实验是单粒子实验，利用了高能物理实验中的多种探测技术。为了对μ子光束线进行表征和监测，采用了新开发的闪烁光纤轮廓监测仪和闪烁体桨速监测仪。为了监测光束的纯度和标记单个μ子的到达时间，将使用双气凝胶切伦科夫系统，并将使用塑料闪烁体飞行时间系统。

An important activity toward advancing accelerator capability is research and development for a high luminosity muon collider. Muons have important properties compared to electrons and protons when considering a possible next step for a high energy physics facility. Since radiation by muons is much suppressed compared to electrons, it is feasible to consider a relatively compact circular collider in the TeV energy range for muons. However the muon, like the electron, is a point particle and therefore can explore the same physics regime as protons with approximately ten times higher energy. Accordingly the muon collider has attracted increasing interest over the past couple of years. Since the muon is an unstable particle there are many new facets of accelerator physics and technology that need to be examined before one can say with confidence that such a device will work. The International Muon Ionization Cooling Experiment (or MICE) is a high energy physics experiment dedicated to observing ionization cooling of muons for the first time. Such cooling is a necessary step toward a muon collider. Cooling is a process whereby the emittance of a beam is reduced in order to reduce the beam size, so that more muons can be accelerated in smaller aperture accelerators and with fewer focussing magnets. This might enable the construction of high intensity muon accelerators, for example for a Neutrino Factory or Muon Collider, which potentially can attain higher energies than electron-positron colliders. Researchers looking for a method of cooling muons designed the MICE experiment to test the effectiveness of a technique called ionization cooling. Ionization cooling takes place when muons are sent through an absorber in which they lose momentum via ionization energy loss. They are then reaccelerated in a linear accelerator where their energy is restored only in the forward direction. MICE will use a single particle beam, with not more than one muon passing through the detector about every 10 nanoseconds. The experiment needs to balance the cooling from energy loss with the heating from multiple scattering of the muons.The Muon Ionization Cooling Experiment will make detailed measurements of muon ionization cooling using a newly constructed low-energy muon beam at the Rutherford Appleton Laboratory (RAL). The experiment is a single particle experiment and utilizes many detector techniques from high energy physics experiments. To characterize and monitor the muon beamline, newly developed scinitillating fiber profile monitors and scintillator paddle rate monitors are employed. In order to monitor the purity of the beam and tag the arrival time of individual muons, a dual aerogel Cherenkov system is used, and a plastic scintillator time-of-flight system will be used.