A major production milestone in a global mission to understand one of the Universe's biggest mysteries - why there is so much more matter than antimatter - has been achieved thanks to the input of UK researchers, including physicists at the University of Liverpool.
Half of the 137 giant neutrino sensors being built by the UK team for the Deep Underground Neutrino Experiment (DUNE) in the US are now complete, marking an important step towards the experiment's search for answers.
University of Liverpool physicists, led by Professor Christos Touramanis, are part of the DUNE international science project which, once complete, will send a beam of neutrinos 1,300 kilometres across the US, in a mission to explain why the Universe is made of matter rather than antimatter.
Neutrinos may hold clues to this mystery, as well as to other fundamental questions about how our Universe works.
Known as Anode Plane Assemblies (APAs), these giant sensors will detect the tiny electrical signals produced when neutrinos interact with liquid argon inside DUNE's enormous underground detector.
The APAs are being manufactured by a team of 25 technicians and engineers at the Science and Technology Facilities Council's (STFC) Daresbury Laboratory, located at Sci-Tech Daresbury, in the Liverpool City Region.
THE STFC team are working in close partnership with teams at the University of Liverpool, alongside the universities of Lancaster, Manchester, Sheffield, Sussex and Imperial College London. Collectively they are contributing components, contributing to quality assurance and providing scientific leadership.
They are part of the wider DUNE-UK collaboration, which brings together 14 universities and two national laboratories, with UK scientists and engineers also contributing to detector systems, software, computing and accelerator infrastructure.
Flagship instrumentation
DUNE is one of the most ambitious particle-physics experiments ever constructed. It will send a beam of neutrinos from Fermilab in Illinois to the Sanford Underground Research Facility in South Dakota, 1,300 kilometres away.
The APAs are the primary readout elements of DUNE's Far Detector 1, making them one of the UK's flagship instrumentation contributions to the experiment.
The UK is responsible for producing 137 of the 150 APAs required for the experiment.
Extraordinary engineering
At around 6.3 metres tall and 2.3 metres wide, each APA is roughly the height of a two-storey building and an extraordinary piece of precision engineering.
Each carries approximately 24 kilometres of hair-thin copper-beryllium wire, held in place by thousands of precision connections across its enormous frame.
When a neutrino interacts inside the liquid argon, it produces charged particles that leave behind electrical signals in the detector.
The APA wires detect those signals, allowing scientists to reconstruct what happened and study the neutrino's properties.
The completed APAs will ultimately be installed nearly a mile underground at Sanford Underground Research Facility, where DUNE's detector will contain tens of thousands of tonnes of liquid argon.
Answering fundamental questions
Neutrinos are among the most abundant particles in the Universe, but they rarely interact with matter, making them extremely difficult to detect.
By comparing the behaviour of neutrinos and antineutrinos as they travel from their source to the far detector, scientists hope DUNE will help answer some of the most fundamental questions in physics.
The experiment will investigate:
- why matter dominates over antimatter in the Universe
- how neutrinos behave and change as they travel
- neutrinos from exploding stars, including supernovae
The depth of the underground facility will help shield the detector from cosmic rays and other background radiation that could interfere with the extremely faint signals DUNE is designed to detect.
Collaboration in action
Ian Lazarus, Head of Technology at STFC's Daresbury Laboratory, said:
"Reaching the halfway point on APA production is a fantastic milestone for everyone involved. These are exceptionally large and technically demanding detector components, and getting to this stage reflects the skill, care and teamwork that has gone into every part of the programme.
"From the engineers building the APAs at Daresbury Laboratory, to the university teams supplying components, carrying out testing and providing scientific expertise, this has been a genuinely UK-wide effort.
"It's exciting to see this work taking shape as part of DUNE, and to know that these detector panels will ultimately help scientists investigate some of the biggest questions about our Universe."
Looking ahead to discovery
Professor Dave Newbold, formerly executive director of National Laboratories at STFC and senior responsible officer for DUNE UK and now co-spokesperson of the DUNE collaboration said:
"The APA team have accomplished a huge milestone by reaching the halfway point in their production. The unique and complex components that are now making their way from the UK to the USA are a central component of the DUNE neutrino detector, and vital to address the ambitious scientific goals of the experiment. It's great to know that profound questions about the universe are soon going to be answered through the efforts of workers across the UK, in industry, laboratories, and universities."
Revealing invisible particles
Together, the thousands of wires on the APAs will provide scientists with information used to reconstruct the position and movement of particles produced in neutrino interactions.
To date, 8 completed APAs have arrived at Fermilab for final testing, ahead of their installation at the underground detector in South Dakota.
A significant step
With half of the UK's 137 APAs now complete, work continues towards delivering all remaining assemblies to the experiment. The remaining APAs are due to be completed in April/May 2029 and delivered for installation in South Dakota between January and November 2029.
Justin Evans, University of Manchester, PI of the DUNE-UK APA project, said: "This is a major step towards realising DUNE. We are building a detector with the potential to answer some of the deepest questions in particle physics: why our Universe is dominated by matter, how neutrinos fit into our understanding of fundamental physics, and what we can learn from neutrinos produced by a supernova.
"DUNE will be one of the world's leading neutrino experiments, and it is enormously exciting to see the detector that will enable this science now taking shape."
Feelings of relief and anticipation
The first APAs were built at Daresbury and delivered to CERN in early 2018 where they were integrated in the ProtoDUNE prototype detector, a project under the co-leadership of Christos Touramanis, head of the Liverpool DUNE group, which validated the DUNE Far Detector design and its performance. More than ten Liverpool physicists, engineers, and technicians made key contributions to the APA project since 2016.
Professor Touramanis said: "As the DUNE physicist in charge of APAs in 2018-23 I am thrilled to celebrate this major milestone and very excited for the discoveries that will come out of DUNE over the next twenty or more years. It will be a fantastic continuation of the world-leading programme that Liverpool is pursuing in the role of fundamental symmetries in nature since the 1980s, and in neutrino physics over the last twenty years."
Image caption: Liverpool physicist Kris Majumdar with an APA in development
Credit: STFC
