Breakthrough of 2013
22 January 2014
Maarten de Jong
The discovery of cosmic high energy neutrinos with IceCube has been awarded by the PHYSICS WORLD magazine as the breakthrough of the year 2013. An interview with Maarten de Jong, Professor at NIKHEF and spokesperson of KM3NeT.
Maarten, the IceCube Collaboration has been awarded the PHYSICS WORLD breakthrough of the year 2013. What do you feel about this as (1) a neutrino physicist and (2) as the responsible project manager of KM3NeT?
Maarten de Jong: I appreciate this recognition for the important achievements of the IceCube collaboration. The latest results do not only consolidate the relatively new field of neutrino astronomy, they put neutrino astronomy at the heart of the wider astroparticle physics programme. While IceCube has shown that the detection of cosmic neutrinos is possible today, the foreseeable future may tell us the answers to many long-standing questions such as: what is the origin of cosmic rays and how do cosmic particle accelerators work?
The recent observations by IceCube represent a major boost to the KM3NeT project. I am delighted because it validates my firm believe that neutrino astronomy has a bright future and because KM3NeT is now in an ideal position to fulfil this future.
The neutrino window to the cosmos has now really been opened by IceCube?
Maarten de Jong: Yes, now it is time to look through the window and see what is behind.
How about the science case of KM3NeT, frozen in concrete by the Icecube results?
Maarten de Jong: IceCube demonstrates the requirements, in particular the size, for building a neutrino telescope capable to detect cosmic neutrinos. Compared to IceCube, an experiment in water offers a better angular resolution and can be easier expanded to a larger sensitive volume. KM3NeT will provide the capability for really doing neutrino astronomy.
Furthermore, IceCube and KM3NeT complement each other to cover the full sky. Scientifically very interesting, the field of view of KM3NeT includes the central region of our Galaxy, which hosts many potential sources of high-energy neutrinos. So, KM3NeT may well be the first to identify the sources of the observed high-energy neutrinos.
And let’s face it, as an underwater infrastructure KM3NeT offers a lot of opportunities that go far beyond neutrino astronomy. Antares demonstrates that there is synergy with Earth and sea sciences.
Can you explain what is KM3NeT phase-1.5?
Maarten de Jong: Following the design study and preparatory phase, the KM3NeT “phase-1” project was launched in January 2013 with an available budget of about 31M euro. The costs for the complete infrastructure, which we call “phase-2”, amount to about 220–250M euro. During a joint meeting with Antares, IceCube, KM3NeT and Lake Baikal in October 2013, the idea of an intermediate phase emerged. The main objective of “phase-1.5” is to be as sensitive as IceCube and measure the IceCube signal with different systematics, improved resolution, and complementary field of view.
IceCube’s technology has been developed in the 1990s/early 2000s, which is more than 10 years ago. Concerning KM3NeT, what major technology developments have been made since that time?
KM3NeT DOM at Nikhef
Maarten de Jong: In general, a neutrino telescope consists of a huge three-dimensional array of photosensors deployed in a transparent medium such as deep water or ice. Among many developments made to increase sensitivity and reduce costs I would like to emphasize that the last decade demonstrated that even the well-known photo-multiplier tube (PMT) technology could be advanced to substantially higher sensitivities. Compared to the traditionally used large PMTs of typically 10 inch size inside a glass sphere, KM3NeT developed an alternative based on incorporating many newly designed small PMTs of 3 inch size inside the same glass sphere. This design helped maximizing the total photo-cathode area, improving photon counting and directionality and reducing costs. The KM3NeT design has attracted interest from other scientific groups as well as industry for the implementation of the low-power high voltage. Following the demand of KM3NeT, the price of small PMTs is now competitive -if not better- compared to large PMTs. In addition to a price reduction, the segmentation of the photo-cathode brings in better data for science. This is like in your digital camera: more pixels yield a better picture!
The readout of the detector is based on the “All-data-to-shore” concept pioneered in Antares. In this, all analogue signals from the PMTs are digitized and all digital data are sent to shore for real-time processing by a farm of commodity PCs. Modern electronics and fiber-optics combined with state-of-the-art firmware and software provide for a flexible and cost-effective implementation of the readout system.
All in all, the costs for the KM3NeT detector are significantly less than those of previous detectors. In short, the KM3NeT telescope will be at least five times larger than IceCube for less than double of the price. In this respect, KM3NeT can be considered as the next generation neutrino telescope.
As a final question for today: In the global context, where do you place KM3NeT?
Maarten de Jong: In October 2013, the Antares, IceCube, KM3NeT and Lake Baikal collaborations signed the Memorandum of Understanding for a Global Neutrino Network (GNN). This step formalized the already active cooperation between the different groups. Once infrastructures of similar scale are operational on the three continents, the stated aim of the GNN is a worldwide Global Neutrino Observatory.
Maarten, thanks a lot!