CERN’s pioneering plasma wake field experiment, Awake began an upgrade a year ago before the rest of CERN’s accelerator complex.
The Awakening Accelerator, which explores ways to make the particle accelerator more compact, has become the first facility to pause CERN’s third long shutdown (LS3) operation.
Most of CERN’s accelerator complexes will enter LS3 in mid-2026, but on June 1st, Awake ended operations and began a series of major improvements.
Unique properties of awakening accelerators
Existing accelerators, such as large hadron colliders, use radio frequency fields within metal chambers to accelerate charged particles. Plasma – the state of matter in which some atoms are released from electrons – can allow higher energy to be achieved over shorter distances.
Awake’s acceleration technology can be used to create coats of arms and troughs in the electric field of a plasma using CERN’s Super Proton Synchrotron (SPS) proton beams to accelerate particles such as electrons.
These “wakefields” can be compared to being able to replace water when speed ships move, explained project leader Edda Gschwentner:
Acceleration of high energy electrons
During its first run from 2016 to 2018, the awakening accelerator became the world’s first experiment to demonstrate electrons being accelerated to multi-GEV energy levels in wake fields driven by protons rather than electrons or lasers.
The first phase of the second run, beginning in 2021 and ending June 1st this year, demonstrated how protons drive and maintain high-amplitude wake fields across 10 meters long plasma medium.
Gschwendtner said: “When the proton beam enters the plasma, it begins to self-conform, meaning it produces small bundles that resonate with the powerful wake field.”
Researchers now show that the quality of the electron beam can be controlled while electrons are accelerated to high energy, and that this process is scalable.
To facilitate this, awakening accelerators must be upgraded, including the installation of new electron beam systems and additional plasma sources.
The first plasma source acts as a self-modification of the proton beam, while the second accelerates externally injected electrons in the proton-driven plasma wake field to 4-10 GEVs to 10 meters.
Protection measures for radioactive materials
It is difficult to increase the size of the awakening accelerator to incorporate these changes. This is because it is located upstream of the chamber, which CERN neutrinos used previously in Gran Sasso (CNGS) experiments.
The CNGS involved pointing the SPS proton beam towards a graphite target and generating a neutrino beam directed towards the Gran Sasso Institute in Italy.
This process makes the target and its shielding material more radioactive, so special protective measures are required for disassembly and removal. A complex process is underway to ensure room for expanded awakening experiments, and new buildings have already been built to house and treat dismantled CNGS materials.
When will the Awake Accelerator upgrade complete?
To spread demand in CERN’s workforce, the demolition and removal process is expected to be nearly complete before other experiments enter LS3 in July 2026.
An improved version of Awake will be built before SPS Proton runs in 2029, before testing new setups begin.
Awake’s goal is to accelerate particles to much higher energy over much shorter distances, bringing them a step closer to realisation.
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