Advancing into a New Era: Unveiling the First Chip-Sized Particle Accelerator

Scientists have engineered electron accelerators at the nanophotonic scale, constituting a major leap toward the miniaturization of particle accelerators. These groundbreaking accelerators are as compact as a computer microchip and utilize lasers to expedite the motion of electrons. This technological advancement has the potential to revolutionize internal radiotherapy by enabling the use of endoscopes in future applications.

For the inaugural time, researchers have achieved the acceleration of electrons using a nanoscale device.

Particle accelerators are indispensable instruments across diverse sectors, including industry, scientific research, and healthcare. These machines typically require spatial footprints ranging from a few square meters up to expansive research facilities. Employing lasers to quicken electrons within a photonic nanostructure provides a microscopic alternative, promising to significantly reduce costs and downsize these devices.

To date, there has been no concrete evidence to substantiate meaningful gains in electron speed. A collaborative effort between laser physicists at Friedrich-Alexander-Universität Erlangen-Nürnberg (FAU) and their counterparts at Stanford University has now successfully demonstrated the world’s first nanophotonic electron accelerator.

The FAU team has made history by measurably boosting the speed of electrons in nanometer-scale structures. Accompanying imagery shows the microchip containing these structures juxtaposed with a 1-cent coin for comparison. Credit: FAU/Julian Litzel

Particle Accelerators and Their Transition to Nanophotonics

When the term “particle accelerator” is mentioned, the Large Hadron Collider at CERN in Geneva—spanning approximately 27 kilometers—is often the first thing that comes to mind. However, such large-scale particle accelerators are not the norm. More commonly, these devices appear in everyday applications such as medical imaging and tumor radiation treatment, though they are still sizable and present room for performance enhancements.

To advance and shrink existing apparatus, global physicists are exploring dielectric laser acceleration, or nanophotonic accelerators. These structures measure merely 0.5 millimeters in length, with an acceleration channel approximately 225 nanometers wide, effectively making them the size of a computer chip.

These particles are propelled by extremely short laser pulses that illuminate the nanostructures. Dr. Tomáš Chlouba, one of the lead authors of the newly published study, states, “The ideal application would be to incorporate a particle accelerator into an endoscope, thereby delivering radiotherapy directly to the targeted area within the body.”

While the vision is yet to be fully realized by the FAU Chair of Laser Physics team, led by Prof. Dr. Peter Hommelhoff and comprising Dr. Tomáš Chlouba, Dr. Roy Shiloh, Stefanie Kraus, Leon Brückner, and Julian Litzel, significant strides have been made. Dr. Roy Shiloh declares, “For the first time, we can truly say we have a particle accelerator on a chip.”

Electron Guidance Plus Acceleration Equals Particle Accelerator

Roughly two years ago, the team achieved their first significant milestone by applying the alternating phase focusing (APF) method to control electron flow across extended distances within a vacuum channel. This served as the foundational step toward creating a particle accelerator. The remaining challenge was to accelerate the particles to achieve significant energy gains.

Stefanie Kraus elaborates, “We have not only been successful in guiding electrons but also in accelerating them across a distance of half a millimeter in these nanofabricated structures.” Though it may seem insignificant to some, this marks a monumental achievement in the realm of accelerator physics. Leon Brückner adds, “We attained an energy gain of 12 kiloelectron volts, a 43 percent increase in energy.”

To achieve such considerable acceleration over large distances—at least in nanoscale terms—the FAU physicists combined the APF method with specially designed pillar-shaped geometrical structures.

The initial demonstration serves as a precursor to greater ambitions. The ultimate objective is to escalate the energy gain and electron current to levels where the chip-based particle accelerator can be employed in medical applications. “To reach higher energies and currents, we will need to expand the existing structures or position multiple channels adjacently,” explains Tomáš Chlouba regarding the team’s future endeavors.

A Worldwide Endeavor Toward Miniaturization

The achievements of the FAU team were nearly concurrently demonstrated by colleagues at Stanford University. Both research teams are collaborating on the “Accelerator on a Chip” project, funded by the Gordon and Betty Moore Foundation.

Dr. Gary Greenburg of the Gordon and Betty Moore Foundation notes, “In 2015, the FAU- and Stanford-led ACHIP team envisioned a revolutionary concept for particle accelerator design. We are thrilled that our financial support has contributed to transforming this vision into a reality.”

Reference: “Coherent nanophotonic electron accelerator” by Tomáš Chlouba, Roy Shiloh, Stefanie Kraus, Leon Brückner, Julian Litzel, and Peter Hommelhoff, published on 18 October 2023 in Nature.
DOI: 10.1038/s41586-023-06602-7

Frequently Asked Questions (FAQs) about nanophotonic particle accelerator

More about nanophotonic particle accelerator

• Nature Journal Article on Coherent Nanophotonic Electron Accelerator
• Friedrich-Alexander-Universität Erlangen-Nürnberg Research Page
• Stanford University Research on Nanophotonics
• Gordon and Betty Moore Foundation
• Particle Accelerators: An Overview
• Introduction to Nanophotonics
• Medical Applications of Particle Accelerators
• Accelerator on a Chip Program (ACHIP)