2023-10-19 22:10:00
Particle accelerators are essential tools in many fields, from industry to research to the medical sector. These machines require considerable space, ranging from a few square meters to large research centers.
Using lasers to accelerate electrons within a photonic nanostructure offers a microscopic alternative with the potential to generate significantly lower costs and make devices considerably less bulky.
So far, no substantial energy gains have been demonstrated. In other words, it hasn’t been proven that the electrons actually increased in speed significantly.
A team of laser physicists from the Friedrich-Alexander-University ofErlangen-Nuremberg (FAU) succeeded in demonstrating the first nanophotonic electron accelerator – along with colleagues from Stanford University.
Particle accelerators: a revolution in progress
When we hear “particle accelerator“, most people probably think of the Large Hadron Collider in Geneva, the ring-shaped tunnel about 27 kilometers long where researchers from around the world conduct research on unknown elementary particles. Such giant particle accelerators are the exception.
We are more likely to encounter them in other places in our daily lives, for example in medical imaging procedures or during radiotherapy to treat tumors. Even then, however, the devices are several meters in size and still rather bulky, with room for improvement in terms of performance.
In an effort to improve and downsize existing devices, physicists around the world are working on dielectric laser acceleration, also known as nanophotonic accelerators.
The structures they use are just 0.5 millimeters long, and the channel through which the electrons are accelerated is only 225 nanometers wide, making these accelerators as small as a computer chip. The particles are accelerated by ultra-short laser pulses illuminating the nanostructures.
Towards a medical application
«The dream application would be to place a particle accelerator on an endoscope so that radiotherapy can be delivered directly to the affected area inside the body“, explains Dr. Tomáš Chlouba, one of the four main authors of the recently published article.
This dream may still be far from the reach of the FAU Chair of Laser Physics team led by Prof. Dr. Peter Hommelhoff but they have now managed to take a decisive step in the right direction by demonstrating the nanophotonic electron accelerator.
Guide electrons + acceleration = particle accelerator.
« For the first time we can really talk about a particle accelerator on a chip “, enthuses Dr. Roy Shiloh.
A little over two years ago, the team made their first big breakthrough: they managed to use the alternating phase focusing (APF) method from the early days of acceleration theory to control the flow of electrons in a vacuum channel over long distances. It was the first major step toward building a particle accelerator. Now all it took to gain large amounts of energy was acceleration.
« Using this technique, we have now managed not only to guide the electrons but also to accelerate them in these nano-fabricated structures over a length of half a millimeter », specifies Stefanie Kraus. While this may not seem like a big feat to many, it is a huge success for the field of accelerator physics. “ We gained an energy of 12 kiloelectronvolts. This is an energy gain of 43% », added Leon Brückner.
To accelerate particles over such large distances (on the nanoscale), FAU physicists combined the APF method with specially developed pillar-shaped geometric structures. This demonstration is only the beginning, however. The goal now is to increase the energy gain and electron current to such an extent that the particle accelerator on a chip is sufficient for applications in medicine.
For this, the energy gain should be increased by a factor of around 100.
« To get higher electron currents at higher energies exiting the structure, we will need to expand the structures or place multiple channels next to each other “, concludes Tomáš Chlouba the next steps of the FAU laser physicists.
For a better understanding
What is a particle accelerator?
A particle accelerator is a device that uses electromagnetic fields to propel charged particles to high speeds and to contain these particles in well-defined beams.
What is a nanophotonic accelerator?
A nanophotonic accelerator is a type of particle accelerator that uses lasers to accelerate electrons within a photonic nanostructure. These accelerators are microscopic and have the potential to generate significantly lower costs and make devices considerably less bulky.
What is dielectric laser acceleration?
Dielectric laser acceleration is a technique used to accelerate particles. The structures used for this technique are only 0.5 millimeters long, and the channel through which the electrons are accelerated is only 225 nanometers wide.
What is the Alternating Phase Focusing (APF) method?
The alternating phase focusing (APF) method is a technique used to control the flow of electrons in a vacuum channel over long distances. This method was used to build a particle accelerator.
What is the purpose of the particle accelerator on a chip?
The goal is to increase the energy gain and electron current to such an extent that the particle accelerator on a chip is sufficient for applications in medicine. For this, the energy gain should be increased by a factor of around 100.
Original publication from FAU: T. Chlouba, R. Shiloh, S. Kraus, L. Brückner, J. Litzel and P. Hommelhoff, DOI: 10.1038/s41586-023-06602-7
Main illustration caption: For the first time, FAU researchers have succeeded in measurably accelerating electrons in structures of just a few nanometers. In the image you can see the microchip with the structures and, in comparison, a 1 euro cent coin. (Image: FAU/Julian Litzel)
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#millimeter #particle #accelerator #change #medicine