MICE Ionization-Cooling Demonstration

The Neutrino Factory is a possible future accelerator facility that creates beams of neutrinos from the decays of muons in a storage ring. The neutrino beams from a Neutrino Factory would have the highest intensity and can be controlled with unprecedented accuracy. For these reasons, the Neutrino Factory has the potential to discover measurable differences between neutrino and antineutrino oscillations, which could be the key to understanding the puzzle of the matter-antimatter asymmetry of the universe. This phenomenon, known as CP violation, has been observed in the quark sector but has never been seen in the neutrino sector. A future Neutrino Factory would determine CP violation in the neutrino sector with the best possible accuracy. Furthermore, a Neutrino factory could be used as a first stage before the construction of a Muon Collider, which could be used to measure the properties of the Higgs boson with the ultimate precision, and could potentially reach energies of up to 6 TeV, in order to explore new physics phenomena at the highest energy frontier.

Both the Neutrino Factory and a Muon Collider rely on the acceleration of muons. To be able to create muon accelerator facilities, we require to reduce the size of the muon beam so that it may be accelerated. Since muons decay within 2 microseconds in their own rest frame, the only known way to reduce the phase space of the muon beam before the muons decay is to use the concept of ionisation cooling, in which the muons lose energy in an absorber such as liquid hydrogen or lithium hydride (LiH) and then recover the longitudinal component of the momentum by accelerating them using RF cavities. The international Muon Ionization Cooling Experiment (MICE) is an engineering demonstration of the concept of ionisation cooling. This experiment is being built at the Rutherford Appleton Laboratory, in which a beam of muons will be cooled in a muon cooling cell consisting of three absorbers and two RF cavities inside the field of two focus coil magnets. The emittance of the beam is measured before and after the cooling channel using a scintillating fibre tracker inside a superconducting solenoid, and the muons are identified using time-of-flight detectors, a Cherenkov detector and a calorimeter system consisting of a scintillating fibre-lead pre-shower detector (named the KL) and a totally active scintillating detector, called the Electron Muon Ranger (EMR).

In this proposal we aim to perform measurements of emittance reduction, without RF cavities (MICE step IV) and perform the final demonstration of ionisation cooling with RF cavities. This proposal is a bid for 42 months funding from Oct 2016 to March 2020, supporting academic and student effort over that period and research staff from the end of the bridging support that ends in December 2016.

1) The main impact of the Muon Ionization Cooling Experiment (MICE) is its contribution to the worldwide Accelerator R&D programme. Techniques developed in MICE are essential for future high power proton facilities including the Neutrino Factory and the Muon Collider. These will benefit the worldwide accelerator industry, including the development of future RF cavities that can operate inside magnetic fields, the development of large superconducting technology that may be realised in a simpler and more cost-effective way, and the development of innovative instrumentation to operate at such facilities.

2) The training of accelerator physicists and engineers underpins the increasing use of accelerators in research and industry, including such disparate areas as medical treatment and diagnosis, security applications and power generation. MICE has trained over 67 STFC and university staff and students, including 22 PhD students (12 have graduated and are deploying their skills in industry, such as IT consultancy, the financial sector, IBM and defence industries), 16 post-doctoral and contract staff and 11 faculty (8 PDRA staff trained on the project have taken their expertise to other projects or to private industry). MICE has developed UK expertise in running a major project in the UK, with 4 STFC and 7 university staff playing senior roles in the project leadership. The expertise in university and STFC staff include: low frequency RF for future accelerators, large superconducting solenoids, novel liquid hydrogen handling systems and accelerator instrumentation.

3) The MICE project will benefit the following collaborations: the international MICE collaboration encompassing 34 institutions in 8 countries; the International Design Study for a Neutrino Factory (IDS-NF), (https://www.ids-nf.org/wiki/FrontPage) and the EC-funded EUROnu project (http://www.euronu.org/), the nuSTORM collaboration (http://arxiv.org/pdf/1206.0294v1.pdf) and the 'Proton Accelerators for Science and Innovation' (PASI) collaboration, (http://pasi.org.uk/Main_Page).

4) The MICE project is benefitting UK and international industry through engineering and construction partnerships: cryogenic engineering (AS Scientific), collaborative development of unusually large superconducting magnets with closed-circuit cooling with TESLA engineering (UK) and Wang NMR (USA), knowledge exchange in the development of the MICE target with TechVac, Multigrind Watford, ExcelPrecision and CCFE-Babcock, and knowledge exchange with UK industry in the manufacture of RF amplifier components, HT safety systems, high power, high frequency electrical contacts and specialist plating and joining methods.

5) The MICE project is active in the dissemination of its activities, with refereed journal and conference publications, a freely accessible archive record (http://www.mice.iit.edu/), organised outreach activities for school students, participation in the Annual Goldsmiths courses for A-level teachers, participation in the Particle Physics masterclasses, public events, such as the "Accelerator extravaganza" at RAL and the General Public Access Day at RAl (8 July 2015), 15 undergraduate, PGI and summer projects hosted by MICE, publicity through Physics World and the CERN Courier, a prizewinning paper at the "SET for Britain" Meeting in 2009, and other public and media activities.