Intense Beam EXperiment (IBEX)

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Modelling an accelerator with a tabletop experiment

Particle accelerators were initially developed to study the fundamental nature of matter itself, but in fact have changed the way we live our lives. There are more than 35,000 particle accelerators in the world being used for a huge range of applications; very precise beams of particles can treat cancer, study biology, create new materials and date archaeological finds. I focus on accelerators which aim not to reach ever higher beam energies, but rather to reach very high beam intensities.

In the near future accelerators which provide intense beams of protons could be used for scientific facilities, but also for future applications like safely eliminating existing nuclear waste in Accelerator Driven Subcritical Reactors (ADSR), testing materials needed for fusion power or generating radio-isotopes for medical procedures. To do this, we need to understand the motion of hundreds of billions of charged particles squeezed into a rapidly changing magnetic and electric system, all controlled to a tenth of the diameter of a human hair. This is an incredible challenge. Losing even one particle in a million would either damage the accelerator or produce unwanted levels of radiation. So the main question I have been asking in my research is: “how do we understand and study these beams and design new accelerators without needing to build the accelerator first?”.

Usually, we rely on computer simulations. But as accelerators get more complex and more intense, we are faced with thousands of components, hundreds of billions of particles and beams which can travel around the accelerator tens of thousands of times as they gain energy. The amount of computational time needed to run accurate simulations is immense. In reality, it can turn out to be impossible as the computer itself can introduce tiny errors which might look like a real effect on the beam. How do we understand the chaotic reasons that particles get lost without actually losing them? How do we know whether a new proposal for a radical new type of accelerator will work, if we’ve never built one before?

By using an experiment rather than simulations, I will let nature do the computational work for me, letting me study many of the details of particle beams. This small experiment is called a Paul trap and is a small electric device which uses very similar physics to an accelerator but using a bunch of trapped charged Argon ions instead of a beam of protons. Rather than studying a beam travelling around an accelerator which sees varying magnetic fields, the Paul trap applies electric fields which alternate in time. This focuses and manipulates the beam in the same way that an accelerator does, while keeping the bunch of particles stationary, as if we are observers riding on the particle beam. By dialling into the Paul trap the correct structure of the accelerator, I will be able to start to answer many of the questions we have about intense particle beams. In future upgrades, we aim to create a Paul trap model of an exciting new type of accelerator that has never been built before called a Non-linear Integrable Optics (NIO) accelerator. This research will let us understand whether or not we could use this new idea in real accelerators in the future. This research could lead to important developments not just in physics, but also make a difference in the real world.

What is it?

IBEX is a linear Paul trap at the STFC Rutherford Appleton Laboratory. This small experiment consists of a linear Paul trap apparatus similar to the S-POD system at Hiroshima University, confining non-neutral Argon plasma in an rf quadrupole field. The physical equivalence between this device and a beam in a linear focusing channel makes it suitable for accelerator physics studies including resonances and high intensity effects.


IPAC'16 paper on 'Overview of the Design of the IBEX Linear Paul Trap Download

Resonance crossing (as in ns-FFAG) with SPOD (collaboration paper) Download

Recent studies of non-linear Paul trap by Hiroshima University collaborators Download