Particle accelerators play an important role in the field of science and technology. The construction and eventual experiments conducted using CERN's Large Hadron Collider (LHC), for instance, have led to the discovery of the Higgs boson, which was previously a theoretical subatomic particle.
The means through which particle accelerators speed up particles, however, pose a problem that could hinder their further development. LHC, which spans 17 miles in circumference, accelerate charged particles by controlling electric fields that are generated inside a metal cavity. With this technique, the accelerating field cannot exceed 100 mega-electron volts per meter. Otherwise, the metal would break down. This means that higher energy accelerators to be constructed in the future would have to be bigger and, consequently, very expensive.
Fortunately, there appears to be a workaround for this issue. A team of scientists from the Lawrence Berkeley National Lab of the U.S. Department of Energy set up a new record by speeding up subatomic particles to the highest energies using a compact accelerator small enough to fit on a table.
Wim Leemans, director of Berkeley Lab's Accelerator Technology and Applied Physics Division, and colleagues used a petawatt laser and plasma, in essence a charged-particle gas, to speed up particles (electrons) inside a tube of plasma measuring nine centimeters long with the speed corresponding to an energy of 4.2 giga-electron volts.
"The acceleration over such a short distance corresponds to an energy gradient 1000 times greater than traditional particle accelerators," the study's news release read.
The acceleration marks a record-setting energy for laser plasma accelerators, a new class of accelerators that scientists believe could reduce enormous traditional accelerators into more compact machines.
"A laser-driven particle accelerator, delivering a beam of electrons with a record-breaking energy of 4.2 giga-electron-volts, could lead to compact x-ray lasers or high-energy colliders," wrote Georg Korn from the ELI Beamlines in Prague, Czech Republic, in reference to the study of Leemans and colleagues.
The researchers achieved the record-breaking energies with the aid of the Berkeley Lab Laser Accelerator (BELLA), which started operation in 2013. BELLA has the capability to produce a petawatt and its development could lead to the development of future accelerators that are up to 100 times more compact than what current technologies offer.
The study "Multi-GeV Electron Beams from Capillary-Discharge-Guided Subpetawatt Laser Pulses in the Self-Trapping Regime," was published in Physical Review Letters on Dec. 8.