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Proposal for continuation of UK participation in the International Muon Ionization Cooling Experiment

关于英国继续参与国际μ介子电离冷却实验的提案

基本信息

批准号：
ST/J002100/1
负责人：
John Cobb
金额：
$ 31.69万
依托单位：
University of Oxford
依托单位国家：
英国
项目类别：
Research Grant
财政年份：
2012
资助国家：
英国
起止时间：
2012 至无数据
项目状态：
已结题

来源：
https://gtr.ukri.org/projects?ref=ST%2FJ002100%2F1
关键词：
Proposal continuation UK participation International

项目摘要

Neutrinos are three different but related particles; their ability to turn into each other has given physicists their first glimpse of the physics which they know must lay beyond the Standard Model. Investigation of the physics which underlies their properties will: deepen our understanding of how the Universe developed after the Big Bang; how the current asymmetry between matter and anti-matter developed from a situation where they were created in equal amounts in the Big Bang; and help us to understand what happens when a supernova explodes showering the cosmos with the heavy elements necessary for planets and life itself to form. In order to understand their properties, we must build an accelerator capable of creating neutrinos in immense numbers. They must have energy between well-defined limits and the mixture of different types must be very precisely known. Such a facility, known as the Neutrino Factory, would be revolutionary and to build one is a challenging project, both from the point of view of the particle detectors which must be built, and the engineering problems which must be overcome. This programme needs a world-wide collaboration, but it is one in which physicists and engineers from the UK are playing a leading role.Neutrinos are created from a beam of muons and the muons themselves are produced from the decay of pions produced by the collision of protons with a metal target. A machine to make an intense beam of neutrinos needs to take the beam of muons, which is large and diverges rapidly, and reduce its size and divergence. The resulting beam can be accelerated, stored and when it decays produces an intense beam of neutrinos. The muons only live for 2.2 microseconds when at rest, and even when they are accelerated and their lifetime is extended by the effect of relativity, there is little time to manipulate the muons so that they are in a state to be accelerated.MICE is an international collaboration based at the Rutherford Appleton Laboratory in Oxfordshire, which uses a beam of muons created by the ISIS accelerator and aims to show that it is feasible to create such an intense beam. It will do this by creating a beam of muons of much lower intensity and tracking each one individually through one part of the system which has been designed to perform this beam compression at the Neutrino Factory. This process where the random sideways motions of the muons are reduced and we are left with the longitudinal motion is referred to as cooling the beam; the system which performs the cooling is known as the cooling channel.The first stage was to build a system capable of producing a muon beam whose size and divergence could be adjusted before it enters the cooling channel. This was completed last year and measurements have been made to show that the beam has the flexibility and intensity for MICE to perform the required measurements.The second stage is to finish construction of the cooling channel itself and to provide a system to measure very accurately the position and momentum of each muon before and after it has passed through the cooling channel. By looking at many muons produced in many different conditions, it will be possible to determine how much cooling has been produced by the channel. In the channel itself the muons will be slowed by passing through a suitable material, such as liquid hydrogen, liquid helium or lithium hydride. As they slow they lose momentum both longitudinally and transversely to the beam axis. Then they are accelerated with high field radio frequency cavities, replacing only the longitudinal momentum.This experiment, which is pushing the boundaries of what is possible with materials, magnets and cooling technologies, represents a collaboration between particle physicists, and accelerator physicists and will demonstrate the UK's ability to host an experiment at the forefront of science and engineering.

中微子是三种不同但相关的粒子;它们相互转化的能力使物理学家们第一次看到了他们知道必须超越标准模型的物理学。对它们的物理性质的研究将：加深我们对宇宙在大爆炸后如何发展的理解;当前物质和反物质之间的不对称是如何从大爆炸中等量创造的情况发展而来的;并帮助我们理解当超新星爆炸时会发生什么，给宇宙带来行星和生命本身形成所必需的重元素。为了了解它们的性质，我们必须建造一个能够产生大量中微子的加速器。它们必须具有在明确限定的极限之间的能量，并且必须非常精确地知道不同类型的混合物。这样一个设施，被称为中微子工厂，将是革命性的，建立一个是一个具有挑战性的项目，无论是从必须建立的粒子探测器的角度来看，还是必须克服的工程问题。这一计划需要全球范围的合作，但英国的物理学家和工程师在其中发挥了主导作用。中微子是由一束μ子产生的，而μ子本身是由质子与金属靶碰撞产生的π子衰变产生的。一台制造强中微子束的机器需要接收μ子束，μ子束很大，发散很快，并减小它的尺寸和发散度。由此产生的光束可以被加速，储存，当它衰变时产生强烈的中微子束。μ子在静止状态下只能存活2.2微秒，即使它们被加速，并且它们的寿命因相对论效应而延长，也几乎没有时间操纵μ子，使它们处于加速状态。MICE是位于牛津郡卢瑟福阿普尔顿实验室的国际合作项目，它使用ISIS加速器产生的μ子束，旨在证明产生这种强束是可行的。它将通过创建一束强度低得多的μ子，并通过系统的一个部分单独跟踪每一个μ子来实现这一点，该系统被设计用于在中微子工厂执行这种光束压缩。这个过程中，μ子的随机横向运动被减少，剩下的是纵向运动，我们称之为冷却束;执行冷却的系统被称为冷却通道。第一阶段是建立一个能够产生μ子束的系统，该系统的大小和发散度可以在进入冷却通道之前进行调整。该项目于去年完成，并进行了测量，结果表明该束流具有灵活性和强度，可用于MICE进行所需的测量。第二阶段是完成冷却通道本身的建造，并提供一个系统，可以非常精确地测量每个μ子在通过冷却通道之前和之后的位置和动量。通过观察在许多不同条件下产生的许多μ介子，将有可能确定通道产生了多少冷却。在通道本身中，μ子将通过合适的材料（如液氢、液氦或氢化锂）而被减慢。当它们慢下来时，它们在纵向和横向上都失去了动量。然后，它们被高场射频腔加速，仅取代纵向动量。这项实验将推动材料、磁体和冷却技术的极限，代表了粒子物理学家和加速器物理学家之间的合作，并将展示英国在科学和工程前沿举办实验的能力。