KM3NeT - News Archive

Archive of news items

New publication: The KM3NeT multi-PMT optical module

27 July 2022 – Long-term operation in the deep sea puts challenging requirements on detectors. A review of the design and construction of the KM3NeT optical module has been published:

S. Aiello et al. 2022 JINST 17 P07038 DOI 10.1088/1748-0221/17/07/P07038


The optical module of the KM3NeT neutrino telescope is an innovative multi-faceted large area photodetection module. It contains 31 three-inch photomultiplier tubes in a single 0.44 m diameter pressure-resistant glass sphere. The module is a sensory device also comprising calibration instruments and electronics for power, readout and data acquisition. It is capped with a breakout-box with electronics for connection to an electro-optical cable for power and long-distance communication to the onshore control station. The design of the module was qualified for the first time in the deep sea in 2013. Since then, the technology has been further improved to meet requirements of scalability, cost-effectiveness and high reliability. The module features a sub-nanosecond timing accuracy and a dynamic range allowing the measurement of a single photon up to a cascade of thousands of photons, suited for the measurement of the Cherenkov radiation induced in water by secondary particles from interactions of neutrinos with energies in the range of GeV to PeV. A distributed production model has been implemented for the delivery of more than 6000 modules in the coming few years with an average production rate of more than 100 modules per month. In this paper a review is presented of the design of the multi-PMT KM3NeT optical module with a proven effective background suppression and signal recognition and sensitivity to the incoming direction of photons.

Rendering of a KM3NeT DOM
Rendering of a KM3NeT optical module with bollards attached to mechanically supporting cables in the deep-sea. In the cut out, the interior of the module with photomultipliers and electronics is visible. The black break-out box connects to the electro-optical network for electrical power and long-distance data communication toward the control station on shore.

KM3NeT at ICHEP 2022

For the first time, the International Conference on High Energy Physics was organized in Italy. This major conference in our field was the opportunity for KM3NeT and ANTARES members to present the latest updates from our experiments.

Some of our collaborators were also involved in the organization of the conference being held in Bologna.

The various talks and posters are available on the website of the conference:

Group picture of some of the KM3NeT members attending ICHEP (showing how seriously they considered this great opportunity!)

Rebecca Gozzini summarizing the potential of ANTARES and KM3NeT for indirect dark matter searches.

Valentin Pestel describing the KM3NeT sensor technology that allows the collaboration to carry out oscillation neutrino studies.

An overview of the recent results of ARCA presented by Piotr Kalczyński.

Victor Carretero presenting his work on the search for new physics in the neutrino sector.

Maurizio Spurio getting ready to present the latest highlights from ANTARES.

Isabel Goos before presenting the potential of KM3NeT for supernova neutrino searches.

Gwenhael W De Wasseige talking about KM3NeT during her plenary talk on multi-messenger physics.

Welcome KM3NeT/ARCA19

14 June 2022 – The sea campaign for enlarging the KM3NeT/ARCA submarine telescope which was started on June 2, has been completed today with a full success. As a result, data taking with ARCA has been resumed with 19 detection units in operation!

This represents a major step forward for the collaboration, as this was the first time that a 2-weeks campaign was performed. The scope of the operation in fact was twofold: to upgrade the submarine network, by installing 2 new junction boxes in replacement of the junction box that we had been operating so far, and to install 11 new detection units (DUs). The operation therefore took place in two steps: after the first round of activities for installation of the junction boxes and the first 4 DUs, the ship went back to shore to pick up the remaining set of 7 DUs.

The campaign was performed with Handin Tide, of the FUGRO company, which had already performed the previous sea campaign for KM3NeT/ARCA last year, sailing off from Malta.

All planned activities were performed with full success, including ancillary operations such as the replacement of one autonomous acoustic beacon on the sea floor. A speed record was also established, with 7 detection units installed, connected and unfurled in less than 48 hours!

As a result of the campaign, the size of ARCA has more than doubled: It now comprises 19 detection units in operation, equipped with more than 10,000 photomultipliers,

The KM3NeT collaboration wishes to thank the Handin Tide crew for their top-level performance, the KM3NeT teams which worked tirelessly offshore and onshore to reach this remarkable success, as well as all teams which work so hard at the almost 30 integration sites of the collaboration to produce the DUs for building the apparatus.

Below is a gallery of pictures from the campaign. A log of the activities while the operation was ongoing is available on our blog.

Detection units in the port of Malta awaiting deployment.
Loading of a detection unit onto Handin Tide.
Handin Tide leaving Malta for the first phase of the campaign.

Deployment of one of the junction boxes installed in the campaign.

The deck of Handin Tide loaded with DUs for the second phase of the campaign.
Connection of one detection unit on the sea bottom.
The onshore control station at Portopalo di Capo Passero during the campaign. More than 30 people from 10 institutes in France, Italy and the Netherlands participated in the activities onshore.


Fifty years ago, in 1972, the first neutrino conference was held in Hungary, because the organisers were not satisfied with the subdued position of neutrino interactions at the international conferences at that time. Nowadays, the neutrino conference is one of the major conferences in neutrino (astro)particle physics. Neutrino2022 took place in virtual Seoul, 30 May-4 June, 2022 and of course KM3NeT was there to show the results of data taking with the first detection units of ARCA and ORCA.

Aart Heijboer, physics coordinator of KM3NeT, showed the results of one year of data taking with ORCA6 and 100 days with ARCA6. The ‘6’  refers to the number of detection units in a detector used in the data analysis.

The ORCA detector is optimised to measure the oscillation parameters of neutrinos travelling through the Earth. Neutrino oscillation is a quantum mechanical phenomenon in which a neutrino created with a particular flavour – electron, muon or tau neutrino – can be later measured to have changed its flavour. In figure 1 below, it is evident that the data does NOT follow the flat blue horizontal line indicating the absence of neutrino oscillations. In other words, already with only six detection units, the ORCA6 detector ‘sees’ oscillations. In the second figure two oscillation parameters are plotted against each other. Clearly, the contour of ORCA6 is still wider than that of other experiments. More data with more detection units will make it narrower.


Also the ARCA detector, optimised for the search of high energy neutrinos from sources in the Universe, is well underway pushing the limits of the potential to discover sources of neutrinos down towards the expected limits of the full detector.


In the poster sessions KM3NeT physicists presented the details of many analyses being performed with the ARCA and ORCA detectors.

Aart Heijboer concluded at the plenary session that ARCA and ORCA will span eight decades in energy, that there is a rich variety of data analyses going on in the collaboration and that construction of the detectors is ramping up. Promising conclusions.

Very nice to have been invited to share the progress of KM3NeT with the community of neutrino (astro)physicists!

The KM3NeT Collaboration thanks the organisers of Neutrino2022 for an excellent edition of the conference. See you in two years time in Milano.


A vibrant Collaboration meeting in Athens

27 May 2022 – Last week the KM3NeT Collaboration joined in Athens for an in-person Collaboration meeting. It was a long-awaited achievement, after two years of remote meetings.  Many thanks to our hosts at NCSR Demokritos for an excellent organisation!

The pleasure to be together again gave new impulse to all activities, and vibrant discussions took place about progress in construction of ARCA and ORCA, preparation of deployments campaigns and the latest methods and results of data analysis.

Besides the fact that we were extremely happy to meet in person again, we have also learned from the pandemic and our ZOOM-experience: With an eye on sustainability, family situations or other obligations, we also offered the possibility to join the meeting remotely. Which worked great!

Of course we also discussed about the war in Ukraine: With deep sadness for the horror which has been developing there for months now, the Collaboration decided to formally suspend all relationships with public institutions in Russia, including those institutes which had a status of observer institutes in the Collaboration. This won’t impact, though, on the solidarity and friendship with our colleagues in Russia, many of whom have openly stood up against the war, who will be therefore still welcome to participate in KM3NeT on a private basis.

During the meeting, the University of Georgia, which participates in KM3NeT with a team led by Kakhaber Tavzarashvili, changed its membership status from observer to member institute, and several colleagues from various institutes made their debut.

Finally, the meeting gave a good opportunity to refine the plans for the newly approved projects of KM3NeT Infradev-2, supported by EU, and the French project NEUMED.

What a feeling to take a nice Collaboration picture again!

A crossroads collaboration meeting

24 February 2022 – Although we had to organise our collaboration meeting virtually once again, it was rich in contents and emotions!

With currently 18 lines deployed, we have discussed recent progress in calibration, data acquisition, simulations, and physics analyses as well as the plans for the future sea operations in 2022!

This meeting also marked a crossroads for neutrino telescopes in the sea. On February 14th 2022, after 16 years of continuous data taking, the ANTARES detector was switched off for the final time. ANTARES has therefore handed over the baton to KM3NeT for the scrutiny of the neutrino sky from the Mediterranean.

Welcome, ORCA-10!

22 November 2021 – Four new detection units have been added to ORCA with a 5-day intense and successful sea operation.

The operation has been performed with two ships: the Castor, equipped for deployment and precise installation of the detection units on the sea floor, and Janus, equipped with a remotely operated vehicle used for inspecting and for connecting the new units to the submarine infrastructure.

You can read all details of the operation in the daily reports published in our ORCA-blog.

Data taking with 10 detection units has been started!

One of the new detection units of ORCA outboard of Castor, preparing to its journey to the seafloor, 2,500 m below.

Online but happy collaboration meeting

19 November 2021 – Our collaboration met this week for its traditional Fall meeting – the 5th to be organised online. Despite the physical distance, we had lively and interesting exchange over the week. Many new data analyses were presented, and more than 120 participants connected to the sessions. The week ended by fun social events, and the wish to chat face to face, in-person at the next meeting.



We also welcomed new institutes in the Collaboration:

– University of Sharjah, UAE;
– Khalifa University, UAE;
Lebedev Physical Institute, Russia;
UCLouvain, Belgium.

The new institutes will work on various topics ranging from neutrino astronomy to neutrino physics, while contributing to detector construction. Welcome in the collaboration!

Finally, we celebrated 6 months of ARCA data taking with 6 detection units! For the occasion, some of the artists in our collaboration prepared a 6hand piano piece. Enjoy!

New sea installation started for ORCA! Follow it from our blog

18 November 2021 – Right in the middle of the joint ANTARES and KM3NeT Collaboration meeting, which is taking place  – once again – online, a new sea campaign has been started for ORCA. Isn’t it the right way to show that a virus can’t stop science?

Today, November 18th, seven new detection units of KM3NeT, onboard the Castor ship of Foselev Marine, sailed from La Seyne sur Mer in Southern France to the KM3NeT/ORCA deep-sea site, about 40 km from the shore. The aim of the campaign is to deploy as many of them as the weather, which is not ideal in this season, will allow.

As in the past campaigns, two vessels will be used for the operation: the detection units will be deployed and precisely installed on the sea floor from the Castor, while a remotely operated vehicle will be maneuvered from the Janus of Comex.

We will document the activites of next days through our liveblog and over our social media channels.

Remain connected with us for this new, extraordinary challenge from the deep sea!

The deck of the Castor packed with detection units, while preparing to sail.

Welcome to the liveblog about the ORCA sea operation of November 2021

November 17, 2021 – KM3NeT is getting ready for a new sea operation at the ORCA site near the French coast of Toulon.

Seven new detection units for ORCA are already onboard the Castor ship which will be used for the deployment.
The ship is waiting for an improvement of the weather conditions to sail from the port of La Seyne Sur Mer.

We will report on this operation with posts in the social media and in the ORCA-blog.