Terahertz radiation to enable portable particle accelerators
Researchers at MIT in the US and DESY (Deutsches Elektronen-Synchrotron) in Germany have developed a technology that could shrink particle accelerators by a factor of 100 or more. The basic building block of the accelerator uses high-frequency electromagnetic waves and is just 1.5 cm (0.6 in) long and 1 mm (0.04 in) thick, with this drastic size reduction potentially benefitting the fields of medicine, materials science and particle physics, among others.
The donut-shaped Large Hadron Collider (LHC) may have grabbed most of the headlines since it came online in 2010, but particle accelerators that are linear (linacs) rather than circular are equally deserving of attention. Though generally not as powerful, linacs are much simpler and cheaper to build, they routinely help scientists understand how certain chemical processes take place, and they have led to innovations including radiation therapy and compact X-ray lasers.
Linacs accelerate particles using large cylindrical modules that include special resonant chambers. When radio signals are fed to these modules, the resonant cavities coordinate radio waves in such a way that energy is transferred to the particles and they are accelerated. Unfortunately, the low frequency of radio waves limits the amount of energy that can be sent, so linacs often need to extend over long distances to supply a useful amount of energy. Stanford's SLAC accelerator, for instance, measures a cool 3 km (1.9 mi).
But now, a team of researchers led by Prof. Franz Kärtner has managed to build a module that makes use of terahertz waves rather than radio waves. This thousand-fold frequency improvement could lead to particle accelerators that are proportionately smaller – meters rather than miles long – while retaining similar performance.
The researchers built a proof-of-principle prototype and verified that a single module was able to increase electron energy levels by 7 keV. According to the scientists, this figure could eventually soar up to 10 MeV, over 10 times more than what the best (and largest) modules can do today.
The scientists now plan to increase the power of the module to build a compact, experimental accelerator that would be less than a meter long.
"We need more terahertz energy and we are working on it," Kärtner told Gizmag. "Our current goal is to produce a compact 20 MeV accelerator. We hope to have that problem solved in two-three years. I would not put a number out, but there is of course the potential to build high energy machines of the scale of SLAC at reduced cost in the future."
Among the possible applications, Kärtner told us that the technology could in principle also be adapted to produce miniaturized but still powerful circular accelerators like the LHC.
A paper describing the advance was published in the latest edition of the journal Nature Communications.