The Large Hadron Collider has proven to be the boon to particle physics that everyone had imagined to be but it’s far from done yet. We’ll likely be getting great data out of the LHC for a couple decades to come, especially with the current and future upgrades that are planned. However it has its limit and considering the time it took to build the LHC many are looking towards what will replace it when the time comes. Trouble is that current colliders like the LHC can only get more powerful by being longer, something which the LHC struggled with at its 27KM length. However there are alternatives to current particle acceleration technologies and one of them is set to be trialled at the LHC next year.
The experiment is called AWAKE and was approved by the CERN board back in 2013. Recently however it was granted additional funding in order to pursue its goal. At its core the AWAKE experiment is a fundamentally different approach to particle acceleration, one that could dramatically reduce the size of accelerators. It won’t be the first accelerator of this type to ever be built, indeed proof of concept machines already exist at over a dozen facilities around the world, however it will be the first time CERN has experimented with the technology. All going well the experiment is slated to see first light sometime towards the end of next year with their proof of concept device.
Traditional particle colliders work on alternating electric fields to propel particles forward, much like a rail gun does with magnetic fields. Such fields place a lot of engineering constraints on the containment vessels with more powerful fields requiring more energy which can cause arcing if driven too high. To get around this particle accelerators typically favour length over field strength, allowing the particles a much longer time to accelerate before collision. AWAKE however works on a different principle, one called Plasma Wakefield Acceleration.
In a Wakefield accelerator instead of particles being directly accelerated by an electric field they’re instead injected into a specially constructed plasma. First a set of charged particles, or laser light, is sent through the plasma. This then sets off an oscillation within the plasma creating alternating regions of positive and negative charge. Then when electrons are injected into this oscillating plasma they’re accelerated, chasing the positive regions which are quickly collapsing and reforming in front of them. In essence the electrons surf on the oscillating wave, allowing them to achieve much greater velocities in a much quicker time. The AWAKE project has a great animation of the experiment here.
The results of this experiment will be key to the construction of future accelerators as there’s only so much further we can go with current technology. Wakefield based accelerators have the potential to push us beyond the current energy collision limits, opening up the possibility of understanding physics beyond our current standard model. Such information is key to understanding our universe as it stands today as there is so much beauty and knowledge still out there, just waiting for us to discover it.