DESY News: First sensors for IceCube Upgrade on their way to Antarctica

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2024/09/02
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First sensors for IceCube Upgrade on their way to Antarctica

The world's largest neutrino detector is being upgraded

The upgrade of the IceCube neutrino telescope has reached an important milestone with the shipment of the first 128 sensors built at DESY to Antarctica. The IceCube detector consists of more than 5000 light sensors, known as Digital Optical Modules (DOM), which are melted into the ice of the South Pole at a depth of up to 2500 metres on 86 cables. It is the largest neutrino telescope in the world with an active volume of around one cubic kilometre. Since its completion in 2010, IceCube has detected high-energy neutrinos from cosmic accelerators such as active galactic cores and from our own Milky Way galaxy. The particles were up to 100 times more energetic than the protons in the Large Hadron Collider, the world´s largest accelerator.

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Zeuthen mechanics assemble the mDOMs under clean room conditions. Photo: DESY, Matthias Schust
In the Antarctic summer of 2025/26, the international IceCube collaboration will install the IceCube Upgrade, an expansion of the detector. Seven new cables with more than 700 optical sensors will be placed close to each other in the centre of IceCube. They will increase the sensitivity of the research ice cube and will allow to measure the properties of low-energy neutrinos generated in our atmosphere with the highest accuracy. New calibration devices will also further improve the sensitivity of IceCube for cosmic neutrinos.

As it is with the IceCube detector itself, DESY is significantly involved in the IceCube Upgrade project. Together with German university groups, the researchers in Zeuthen developed one of the two sensor types for the upgrade: the multi-PMT Digital Optical Module (mDOM). “We are very pleased with the successful progress of the upgrade project – from development and production to the current dispatch of the first modules,” says Christian Stegmann, DESY Director of Astroparticle Physics.

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The mDOMs newly developed for the IceCube upgrade can look in all directions with their 24 light sensors. Photo: Susann Niedworok
In contrast to the DOMs previously used at IceCube, the mDOM has 24 photomultipliers (PMTs) as light-sensitive elements and can observe light from all directions. More than 400 mDOMs are currently being manufactured at DESY in Zeuthen and at Michigan State University in the USA. Before they are then shipped south and melted down in the perpetual ice of Antarctica, all mDOMs are operated for three weeks at a temperature of minus 40 degrees Celsius in a freezer container to ensure that they are suitable for use in the detector for at least 10 years. After several years of development and two years of construction, the first delivery of 128 mDOMs was shipped from Zeuthen to Antarctica in mid-August.

“This marks an important milestone on the way to the IceCube Upgrade. The entire mDOM team is already looking forward to the first neutrinos measured with mDOMs,” says Timo Karg, who is leading the work on the IceCube Upgrade at DESY. The mDOMs will travel by ship to New Zealand and from there be transported by plane to the South Pole. There they will be tested by DESY scientists next December and January, during the Antarctic summer, and will then be ready for installation in the ice a year later.