Particle accelerators generate high energy beams of electrons, protons and ions for a wide range of applications. It includes particle colliders that shed light on nature’s subatomic components, X-ray lasers that capture atoms and molecules during chemical reactions, and medical devices for cancer treatment. As practice shows, the longer the accelerator, the more powerful it is. However, a team of scientists from the US Department of Energy’s SLAC National Accelerator Laboratory has invented a new type of accelerator design that provides 10 times more energy gain at a given distance than conventional accelerators. This can make the accelerators themselves 10 times shorter. A key idea of the technology, described in a recent article in Applied Physics Letters, is to use terahertz radiation to increase the energy of particles.
In modern accelerators, particles receive energy from a radio frequency field supplied to accelerator structures of a certain shape or cavity. Each cavity can only provide a limited increase in energy at a given distance, so very long chains of cavities are needed to generate high-energy beams.
Both terahertz and radio waves differ in their respective wavelengths. Since terahertz waves are 10 times shorter than radio waves, resonators in a terahertz accelerator can also be much smaller.
One of the main challenges in creating such small hollow structures is the need for precision machining. Over the past few years, SLAC teams have made some headway on this issue. Instead of using the traditional process of stacking many layers of copper on top of each other, they built their finest structure.
The new structure produces particle pulses a thousand times shorter than the pulses emanating from conventional copper structures.
The researchers plan to turn their invention into an electron gun – a device that could generate incredibly bright beams of electrons for scientific discoveries, including next-generation X-ray lasers and electron microscopes that will allow real-time viewing of how nature works at the atomic level. These rays can also be used to treat cancer.
Realization of this potential also requires further development of terahertz radiation sources and their integration with modern accelerators. Since terahertz radiation has a short wavelength, its sources are especially difficult to develop, and there are currently too few technologies for this.