This Week’s Science News from SWTG

A New Particle Accelerator & String Theory Gets Saved?

Physicists Just Invented a New Particle Accelerator!

Credit: Murakami et al, Sci Rep 15, 19112 (2025)

Physicists just invented a new type of particle accelerator, using a “micronozzle.” It accelerates protons just like the LHC, but does over a distance of micrometers what takes a standard magnet-based accelerator hundreds of meters. In the press release, the inventors say the new method delivers “excellent beam quality”. Could this be the future of high energy physics? Let’s have a look.

For decades, building a proton collider meant increasingly larger rings of increasingly stronger magnets. It’s worth the effort, we’ve been told, because probing short distances requires high energies. Particle colliders, therefore, are our best chance to find out what happens at short distances. Yet the increasingly huge size of these colliders has become economically unsustainable. CERN’s plans for the next larger collider, the FCC, which would be more than 90 kilometres in circumference, are in the range of about $40 billion.

One of the technologies that could shrink particle accelerators down is wakefield acceleration. For this, one shoots a laser at a gas. The laser displaces charges, creating a plasma that travels at high speed, pulling electrons behind it. This method has been used to successfully accelerate electrons up to about 5 giga-electron volts or so over a distance of about 1 centimetre. That’s still about a factor 1000 less than what the LHC currently delivers, but it’s promising. Unfortunately, wakefield only works for electrons. Protons are just too heavy.

This is where the new idea, called micronozzle acceleration, comes in. It works like this: Inside a vacuum chamber, you place a metallic funnel, that’s nozzle. It’s just a few millimetres wide and in their example, it’s made of aluminium. Inside of it, you have a small rod with hydrogen, because you want to accelerate protons and hydrogen nuclei are just protons. The rod could be frozen hydrogen or some other material that’s saturated with hydrogen.

Then, you take a big laser – which must have a power of several petawatts – and shoot it at the funnel. This rips electrons off the material of the nozzle. At the incoming side of the nozzle, this creates a lot of moving electrons inside of the nozzle. These hit the hydrogen rod and kick out protons. But at the outgoing side of the nozzle, this strips electrons off on the outer side. This means that the inner side is positively charged. Because of the curve of the nozzle this both focuses and accelerates the protons. This is really clever.

Now I have to warn you that this was not an experiment, it was a computer simulation. But at least in this computer simulation, the protons reached almost a giga-electron volt in energy. So that’s still somewhat less than wakefield acceleration reaches for electrons – and it’s a simulation rather than the real thing – but come on, this is a really cool idea. And they reached this acceleration just over a few micrometres, which coincidentally is just about the size of my enthusiasm for the $40 billion collider.