Scientists at CERN, the European Organization for Nuclear Research, have run the first tests on a new kind of accelerator, exploring a method that can dramatically cut the size of future particle physics experiments.
Particle physics studies are no small feat — literally. The Large Hadron Collider (LHC) spans 5 miles or so in diameter, which is huge enough to comprise a number of towns. The Linear Accelerator of Stanford University, on the other hand, is 2 miles in length. Is there a way to produce far smaller yet still massively powerful accelerators?
Wakefield Acceleration
As Popular Science explains, colliders such as the LHC boast many parts, but the overall need somewhere to store particles and get them working at extremely high speeds. This place will smash the particles together or against another entity, and look at all of the bits produced by the explosion.
As part of the process of speeding up, the particles need to be pushed via subjecting them to a series of alternating electric fields. Getting particles to work faster generally entails building longer rather than more powerful experiments.
Through the AWAKE experiment, CERN will test a novel method that will get such particles going much quicker in a shorter span of time. It’s a proof of concept and an early attempt at producing wakefield acceleration.
The idea of a wakefield accelerator was first proposed in the 1970s, but back then was a bit too technical to be pursued. The concept is that proton beam-driven plasma wakefields could accelerate charged particles.
How does this work? First, a packet of protons from the Super Proton Synchrotron, the institute’s proton accelerator, will go through a plasma field. The electrons (negatively charged) fly toward the protons (positively charged), at which point the latter have flown away and the former remain flying.
In their absence, the electrons leave positively charged plasma, effectively pulling them back to where they came from.
The process goes on and creates a wave; plop an electron into the wave and it will surf along to avoid other negative electrons that go crashing down. This leads the “surfer” to accelerate speedily through the wakefield, which can be a thousand times faster than the conventional technique.
Prospects: Much Smaller Accelerators
Project leader Edda Gschwendtner said this spells great potential for allowing particle accelerators to be much smaller than they currently are.
“If you make a linear collider nowadays it would be about 50 kilometers [31 miles],” she told PopSci.
The test beam for the experiment, also dubbed as the “Proton Driven Plasma Wakefield Acceleration Experiment,” took place June 16 and sought to see whether all the sections of the beam line to the experiment are correctly working, and that the magnets are aligning the beam correctly.
As a beam of particles has been successfully sent through the experiment, the next stage of commissioning is underway.
“What was really nice is that when we first sent the beam down the proton line to the experiment area, it immediately hit the last detector, verifying our calculations and installation,” said Gschwendtner.
CERN now has the beam, but still has to perform measurements and calibration, as well as collect physics data by the end of this year. And there is no accelerated electrons or plasma just yet, as that would likely happen no earlier than 2018.
All these may one day give rise to a tabletop-sized accelerator, never mind it would probably take a couple of decades or so.
