New Powerful Particle Accelerator One Step Closer With Muon Sorting Technology

New experimental results show that particles called muons can be coralled into beams suitable for high-energy collisions, paving the way for new physics.

Particle accelerators are best known for collapsing matter to probe its composition, but they are also used to measure the chemical structure of drugs, treat cancer and make silicon microchips.

Current accelerators use protons, electrons, and ions, but more powerful accelerators using muons—heavier relatives of electrons—have the potential to revolutionize the field. Muon accelerators would be cheaper and smaller, so they could be built on the same sites as existing accelerators, while still having access to even higher energies.

Now, a new analysis of the muon beam experiment has demonstrated the success of one of the key technologies required for muon accelerators. This paves the way for the muon accelerator to scale up earlier than other types of accelerators using different particles.

The analysis was led by scientists from Imperial College London as part of the MION Ionization Cooling Experiment (MICE) collaboration, and the findings are published in Natural physics.

The first author of the study, Dr. Paul Bogdan Jurj, from Imperial’s Department of Physics, said: “Our proof of principle is great news for the international particle physics community, which is preparing plans for a new generation of higher energy accelerators. It is an important development towards the realization of a muon accelerator that could fit into existing sites , such as FermiLab in the United States, where enthusiasm for this technology is growing.

Powerful particle accelerators

The world’s most powerful particle accelerators, such as the Large Hadron Collider (LHC), smash particles called protons at high energies. These collisions produce new subatomic particles that physicists want to study, such as the Higgs and other bosons and quarks.

To achieve higher energy collisions and access new physics discoveries and applications, a much larger proton collider would need to be built. The LHC is ring-shaped with a circumference of 27 km, and plans have been drawn up to potentially build an accelerator nearly 100 km long.

However, the considerable cost and long time required to build such an accelerator means that some physicists are looking elsewhere for a solution. Promising avenues include colliders that break up muons instead.

Muon colliders would be more compact and therefore cheaper, reaching such high effective energies as the proposed 100 km proton collider in a much smaller space. However, technological developments are needed to ensure that the muons collide often enough.

Marshal minions

The main problem was getting the muons to gather in a small enough space so that when accelerated, they formed a concentrated beam. This is necessary to ensure their collision with the beam of muons accelerated around the ring in the opposite direction.

The MICE collaboration previously produced such a beam using magnetic lenses and energy-absorbing materials to “cool” the muons. Initial analysis showed that this successfully moved the muons toward the center of the beam.

A new analysis of this experiment looked more closely at the “shape” of the beam and how much space it took up. As a result, the team was able to show that the beam was made ‘more perfect’ by cooling: it was smaller in size and the muons traveled in a more organized manner.

The experiment was performed using the MICE muon beam at the Science and Technology Facilities Council (STFC) ISIS Neutron and the muon beam facility at the STFC Rutherford Appleton Laboratory in the UK. The team is now working with the International Muon Collider Collaboration to build the next phase of demonstrations.

MICE Collaboration spokesperson Professor Ken Long, from Imperial’s Department of Physics, said: “The clear positive result shown by our new analysis gives us confidence to continue with larger prototype accelerators to put this technique into practice.”

Dr. Chris Rogers, based at STFC’s ISIS facility in Oxfordshire, led the MICE analysis team and is now leading the development of the muon cooling system for the muon accelerator at CERN.

He said: “This is an important result that shows the cooling performance of MICE in the clearest possible way. It is now essential that we move on to the next step, a muon cooling demonstrator, to deliver a muon accelerator as soon as possible.”