Scientists say they have found a way to shrink a critical component of particle accelerators, which could allow for the miniaturization of more powerful accelerators in the future. The research, led by the Deutsches Elektronen-Synchrotron’s (DESY) Franz Kärtner from the Center for Free-Electron Laser Science (CFEL), is published in the journal Nature Communications.
In modern particle accelerators, electromagnetic radiation in the radio frequency range is used to accelerate electrons to near light speed. Accelerators like this include the Large Hadron Collider (LHC) and others used in medicine in devices such as X-ray machines.
This latest breakthrough relies on using terahertz radiation instead, found between infrared radiation and microwaves on the electromagnetic spectrum, which has a wavelength 1,000 times shorter than comparable radio frequencies. As a result, small “accelerator modules” that play a part in accelerating the electrons can be made comparably shorter, with a cross-section of just one millimeter (0.04 inches) – compared to 10 centimeters (four inches) in normal accelerators. This means the entire accelerator can be greatly reduced in size while still achieving similar energies – and it can be scaled up to achieve greater energies with more ease.
"Terahertz radiation is more useful than radio frequency because you have shorter wavelengths, and therefore need less energy to generate the same accelerating field," Kärtner told IFLScience. "As soon as we can generate more terahertz radiation, we can accelerate with higher energies. No question."
Although terahertz radiation had been considered before, it had been difficult to use it at high energies using electron beams. In this latest research, the researchers used lasers instead to produce comparatively high energies. Their prototype increased the energy of particles by seven kiloelectronvolts (keV, thousand), but they think that in three to four years, they could achieve energies of 20 megaelectronvolts (MeV, million). These are useful energies for smaller particular accelerators, but not so useful for particle smashers like the LHC, which use energies of more than 13 teraelectronvolts (TeV, trillion).
"This is not a particularly large acceleration, but the experiment demonstrates that the principle does work in practice," explains co-author Arya Fallahi of CFEL in a statement. Thus, the scientists don’t see their research being useful for accelerators like the LHC, which would need to generate a lot of terahertz to be useful, but rather more compact accelerators used in other areas like medicine, or perhaps even in linear accelerators that don’t quite match the LHC in size.
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