As scientists prepared to collapse the first particles in the Large Hadron Collider (LHC) in 2010, parts of the media dreamed that the EU-wide experiment could create a black hole that could swallow and destroy our planet. How on earth, columnists rage, could scientists justify such a dangerous indulgence for the pursuit of abstract, theoretical knowledge?
However, particle accelerators are much more than just giant toys that scientists can play with. They also have practical uses, although their sheer size has so far prevented their widespread use. Now, as part of a large-scale European collaboration, my team has published a report that explains in detail how a much smaller particle accelerator can be built – closer to the size of a large room than a big city.
Inspired by the technological and scientific know-how of machines like the LHC, our particle accelerator is designed to be as small as possible so that it can be used immediately in industry, healthcare and universities.
Collider area
The world’s largest collider, the LHC, uses particle acceleration to achieve the amazing speeds at which it collides particles. This system was used to measure the coveted Higgs boson particle – one of the most elusive particles predicted by the Standard Model. This is our current model for describing the structure and functioning of the universe.
Since the early 1930s, there have been fewer giant and glamorous particle accelerators performing useful tasks and causing collisions to improve our understanding of basic research. Accelerated particles are used to create radioactive materials and powerful radiation explosions, which are critical to health processes such as radiation therapy, nuclear medicine, and CT scans.
The typical disadvantage of accelerators is that they are bulky, complex to operate, and often prohibitively expensive. The LHC is a pinnacle of experimental physics, but it is 27 kilometers in circumference and costs 6.5 billion Swiss francs (5.2 billion pounds) to build and test. The accelerators currently installed in select hospitals are smaller and cheaper, but still cost tens of millions of pounds and require 400 x 400 m of space to install. Therefore, only large regional hospitals can afford the money and space for a radiation therapy department.
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Why exactly do accelerators have to be so big? The simple answer is, if they were smaller they would break. Since they are based on solid materials, increasing the performance too much would tear the system apart and create a very expensive mess.
The Large Hadron Collider is a huge loop system on the border between France and Switzerland. Cern
Need for speed
We wanted to find a way to make smaller, cheaper particle accelerators for use in a larger number of hospitals – from large and regional to small and provincial.
Our team assumed that you have two options for accelerating particles: either a strong push over a short distance or a lot of small nudges over a long distance – this is how the LHC works.
It’s a bit like going 100 mph in a vehicle: you can either accelerate slowly in a truck over a long period of time, or you can put your foot in a sports car and get there in seconds. Conventional accelerators are a bit like trucks: reliable and docile, but slow. We were looking for an alternative to sports cars.
We found this alternative in plasma. The beauty of plasma is that it consists only of an ionized gas: a gas that has been broken down into its smallest components. As such, it does not have the same limit on performance that can be applied to it as a solid system. In fact, you can’t break something that’s already broken.
A researcher holding part of our novel particle accelerator in his hand. Behind it is the corresponding section of a conventional accelerator. EuPRAXIA Conceptual Design Report, author provided
In this sense, plasmas can withstand much higher acceleration forces – up to a thousand times greater than a solid-state accelerator. The higher the power, the shorter the time and distance it takes to accelerate particles, and this results in smaller, cheaper accelerators.
Our accelerator uses powerful lasers to “shake” the plasmas it contains and to move their particles in such a way that waves are created. It’s a bit like the trail a boat (the laser) left on a lake (the plasma). Like a surfer, a beam placed on one of these waves can be pushed forward by it and constantly accelerate. These waves within plasmas are very small (sub-millimeters) and very strong, which means that the overall accelerator can be extremely small.
Plasma benefits
Plasma-based particle accelerators like ours require 100 times less space than existing structures, reducing the space required for installation from 400 x 400 m to just 40 x 40 m. The hardware needed to build our accelerator is cheaper to install, run, and maintain. Overall, we expect our plasma accelerator to reduce the cost of installing an accelerator in a hospital by a factor of ten.
A mouse embryo scanned with our machine (left column) and conventional scans (right column).
In addition to these two benefits, our accelerator can perform certain new functions that existing accelerators cannot. For example, plasma-based accelerators can provide detailed x-rays of biological samples with far greater clarity than those that exist today. By providing a better picture of the inside of a human body, doctors could find cancer at a much earlier stage and dramatically increase the chance of successfully treating the disease.
The same high-resolution imaging can also help identify the first signs of cracks and defects on machines in the nanometer range. Failures related to such failures are considered one of the “six big losses” known to manufacturers. Their early detection by our accelerator could help to extend the service life of high-precision, high-quality components in heavy industry and in manufacturing.
Accelerator rollout
The European Strategy Forum for Research Infrastructures will evaluate the draft report with a decision expected in summer 2021. If successful, it is expected that construction of the first two prototypes will be completed by 2030 and access to external users will be granted immediately thereafter.
It took us several years of interdisciplinary research to develop the first detailed and realistic design of such a machine. Our plasma accelerator is the latest example of how obscure, abstract, fundamental physics can invade our daily lives – cut research costs, improve manufacturing, and save lives.
This article by Gianluca Sarri, Reader (Associate Professor) in the Faculty of Mathematics and Physics at Queen’s University in Belfast, is republished from The Conversation under a Creative Commons license. Read the original article.
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