- Email: [email protected]
KM3NeT: Toward a cubic kilometre volume neutrino telescope in the Mediterranean Sea
ARTICLE IN PRESS Nuclear Instruments and Methods in Physics Research A 595 (2008) 54–57
Contents lists available at ScienceDirect
Nuclear Instruments and Methods in Physics Research A journal homepage: www.elsevier.com/locate/nima
KM3NeT: Toward a cubic kilometre volume neutrino telescope in the Mediterranean Sea C. Markou Institute of Nuclear Physics, NCSR ‘Demokritos’, Agia Paraskevi Attikis, Athens 15310, Greece
For the KM3NET Consortium a r t i c l e in f o
a b s t r a c t
Available online 8 July 2008
High energy neutrino astronomy is emerging as one of the most exciting options for studying astrophysical processes. To establish neutrino detectability from specific sources, neutrino telescopes of 3 km scale are needed. In order to complement the IceCube detector currently under construction in the South Pole, a corresponding Northern Hemisphere detector is needed. The three neutrino telescope projects in the Mediterranean, ANTARES, NEMO and NESTOR have joined forces in order to develop, prepare, construct and operate such a research facility, KM3NeT. To this end, the EU is funding a 3-year design study. In the present paper, the status of the design study is presented and options for the various technical problems are discussed. & 2008 Elsevier B.V. All rights reserved.
Keywords: Neutrino astronomy Neutrino telescopes KM3NeT
1. Introduction Detecting high-energy neutrinos from specific astrophysical sources will be a major step towards understanding various particle physics related processes which occur in the universe. These neutrinos can be detected by water/ice Cherenkov telescopes. Such detectors can contribute to the study of Active Galactic Nuclei (AGN), Supernova Remnants (SR) or microquasars, Gamma Ray Bursts (GRB), etc. At the same time, questions like the search for neutrinos from the decay of dark matter particles (WIMPs), magnetic monopoles and other exotic particles can be addressed [1]. As recent studies indicate [2,3], these signatures 3 will only be accessible through detectors of km scale or even larger. Current telescopes like AMANDA [4] and ANTARES [5] are too small for this task. The IceCube [6] telescope, under construction at the South Pole 3 will have an instrumented volume of 1 km . Being a downward looking detector, the sensitivity to the southern sky will be limited. This limitation includes regions of the Galactic plane containing a multitude of possible high energy neutrino sources, like SR, microquasars, pulsar wind nebulae as well as several unassociated gamma-ray sources as reported by the H.E.S.S. telescope [7,8]. A logical conclusion is that a complementary detector in the Northern Hemisphere is needed to cover the whole sky.
E-mail address: [email protected] 0168-9002/$ - see front matter & 2008 Elsevier B.V. All rights reserved. doi:10.1016/j.nima.2008.07.009
In the Mediterranean Sea, three pilot projects, namely ANTARES [5], NEMO [9] and NESTOR [10] have joined forces in order to design, develop, construct and operate such a neutrino telescope, KM3NeT [11]. Apart from the accumulated expertise, the Mediterranean Sea offers some unique advantages for such an endeavor, namely, deep waters close to the shore, proximity of infrastructures, clean waters and large windows of good weather periods for the necessary sea operations. The KM3NeT collaboration currently consists of 37 Institutes from 10 European Countries (Cyprus, France, Germany, Greece, Ireland, Italy, Netherlands, Romania, Spain, UK). The KM3NeT facility is meant to be an interdisciplinary research infrastructure, serving, in addition, as a deep water facility for associated sciences, like marine biology, oceanography, geology, geophysics and environmental sciences.
2. Status of KM3NeT Within FP6 the EU has initiated a 3-year research and development phase for KM3NeT. This design study started in February 2006, and will conclude in 2009 with the publication of the Technical Design Report (TDR) for KM3NeT. In early 2008, the Preparatory Phase (PP) of KM3NeT will start, overlapping for one year with the design study. The PP will be funded by FP7 and will address the political, governance, financial, strategic and sociopolitical issues of KM3NeT, including the site selection. The PP will also include prototyping work, in view of the start of the telescope construction in 2011. The time schedule of KM3NeT is such that the construction is expected to start early in the next decade,
ARTICLE IN PRESS C. Markou / Nuclear Instruments and Methods in Physics Research A 595 (2008) 54–57
55
string layout
allowing the completion and operation of KM3NeT concurrently with IceCube. The overall cost of KM3NeT is estimated to be 220–250 MEuro. KM3NeT is part of the ESFRI (European Strategic Forum on Research Infrastructures) roadmap [12] for future large scale infrastructures, being recognized as a research infrastructure of pan-European interest.
600 400 200 0 -200 -400 -600
-600
-400
-200
0 x [m]
200
0 x [m]
200
400
600
string layout 800 600 400 200 y [m]
The design study aims at providing design options for various components and detector configurations so as to deliver a detector with the best sensitivity for physics studies. The minimum requirements in terms of performance are an instrumented 3 volume of at least 1 km , with angular resolution of about 0:1 for neutrino energies above 10 TeV, sensitivity to all neutrino flavors, and a lower energy threshold of a few hundreds GeV (and around 100 GeV for pointing sources). Neutrino Cherenkov telescopes consist of a (usually) large number of photo-detection units, typically optical modules (OMs) containing one or more photomultiplier tubes (PMTs) for the detection of Cherenkov light. The OMs used in existing experiments, contain one large PMT (typically 10 in.) enclosed in a protective, pressure resistant, waterproof glass sphere. These OMs are arranged so as cover the instrumented volume, grouped in vertical structures with equal spacing between units. The specific choice of PMT size and arrangement in the OM as well as the layout of OMs in the instrumented volume have become the subject of detailed simulation, in order to optimize the sensitivity of the detector. In the context of the design study, various OM configurations and detector layouts have been simulated [13]. Examples of possible OMs can be seen in Fig. 1. These include OMs with a single large PMT, double OMs, and OMs with many small PMTs inside. A large number of detector layouts have been evaluated, with the vertical strings arranged in cuboid, ring, hexagonal, clustered or mixed layouts (Fig. 2). In all cases the total instrumented volume has been kept constant to 3 1 km and the total area of photocathode was kept constant. The effective area for muons as a function of muon energy is shown in Fig. 3 where the KM3NeT configuration-1 detector is a hexagonal array consisting of 127 vertical strings each with 25 OMs, 100 m horizontal spacing, 15 m vertical spacing between OMs and three large PMTs per OM, similar to the ANTARES configuration. In the same figure, the configuration-2 detector corresponds to a structure of 225 vertical strings arranged in a cuboid grid with interline spacing of 95 m, 36 stories, vertical spacing between OMs 16.5 m, with each OM containing 21 3 in. PMTs. The effective area calculation includes full simulation of the neutrino interaction, muon propagation, Cherenkov light transmission, track reconstruc-
y [m]
3. Detector optimization
0 -200 -400 -600 -800 -800
-600
-400
-200
400
600
800
Fig. 2. Examples of the detector layout: cuboid (top), ring (bottom) [13].
tion and event selection. Optical noise including 40K decays in sea water was added, as measured by NESTOR [14] and NEMO [15] in the respective sites. The higher effective area of the two KM3NeT detector configurations compared to IceCube can be explained partly in terms of the higher photo-cathode area and partly to the better angular resolution of the water detector. With similar configurations KM3NeT will have a sensitivity one order of magnitude higher than existing experiments.
4. Detector components and procedures
Fig. 1. Various options of optical module designs: (from left to right) single 10 in. PMT, multi-PMT OM, double PMT OM [13].
In designing the detector, the KM3NeT consortium can build upon the expertise of previous experiments, both in water (like DUMAND, Baikal, ANTARES, NEMO and NESTOR) and in ice
ARTICLE IN PRESS
Neutrino effective area (m2)
56
C. Markou / Nuclear Instruments and Methods in Physics Research A 595 (2008) 54–57
102
preliminary
10 1 10-1
Antares
10-2
IceCube KM3NeT configuration 1
10-3 10-4
KM3NeT configuration 2
2
2.5
3
3.5 4 4.5 log10 (E [GeV])
5
5.5
6
Fig. 3. Muon effective area as a function of energy for two KM3NeT layouts, IceCube and ANTARES [13].
(AMANDA, IceCube). Several key lessons have been learned from each of these projects. The highly hostile environment in which the detector has to operate, dictates the most crucial requirement on the system and its components, namely the reliability of the off-shore parts. Evidently, the recovery and repair of faulty components from the deep sea is both very difficult as well as costly and time consuming. Therefore, high reliability of all deep sea components is absolutely essential. One major design choice towards improving reliability is to simplify the design and reduce the number of underwater-mated connections. In the context of the design study, several options are being studied and evaluated. For example, the optical and acoustic calibration units which are used for timing calibration and for monitoring the positions of OMs, respectively, could, in principle, be separated from the OMs. Also under study is the possibility of transmitting all data to shore via optical fibre and reduction of the in-sea electronics using a photonics-based network [16]. In this scenario, the OM signal is flagged in a local optical modulator interrogated by an optical signal from the shore. The modulated signal is timestamped on shore, thus necessitating no off-shore laser for data transmission. Additional research and development is under way to evaluate the performance of OMs containing many smaller PMTs. These have the advantage of higher quantum efficiency, better single photon resolution, smaller transit time spread, and provide directionality which helps reducing noise from bioluminescence and 40K. A prototype is being built and evaluated at NIKHEF [17]. Also under investigation is the use of 10 in. PMTs with segmented photocathode area [18], as another way of gaining directionality, as is the evaluation of the performance of crystal hybrid PMTs [19]. In order to calibrate the angular resolution, absolute position and angular offset, the use of a floating sea-top array in the spirit of IceTop is under investigation [20]. The position of the sea-top detector can be determined via GPS, and signal from extensive air showers to calibrate the underwater detector. Preliminary studies indicate that three floating stations at distances of 20 m equipped with 16 m2 of scintillator each will be sufficient. The production model for the components should ensure that the detector can be built within a logical time frame. This corresponds to a construction time of about 3 years, if KM3NeT is going to be operational concurrently with IceCube. With a total of about 10,000 OMs distributed over 250 detector units, plus around 25 additional calibration lines, the production line should be able to handle 15 OMs per day, and complete 10 detector lines and one calibration line per month. This probably means that five production lines will be needed, with adequate logistics and quality control systems in place.
The size of the detector implies that new ways of sea deployment will have to be developed. The ANTARES mode of deployment with separate operations for the line deployment and the cable connection with a submersible is time consuming and impractical for a detector the size of KM3NeT with around 250 lines. A possible solution could be the method proposed by the NEMO collaboration in which each line is ‘‘rolled-up’’ in a container [21]. The line equipped with a release mechanism which unfolds the line after the container reaches the sea floor. By connecting several of these compact containers together, one sea operation will suffice for the deployment of several lines. Such a deployment model reduces both the time for interconnection of lines and the number of wet-mateable connections which are a significant source of potential failures. The feasibility of such a deployment model has been successfully demonstrated by the NESTOR collaboration when they deployed a tower module without any underwater operation [22].
5. Associated sciences The KM3NeT research facility will also serve the community of marine and geophysical sciences. The existence of dedicated and permanent sea-to-shore connections is a very desirable feature. Indeed, there is a separate working group within the KM3NeT design study, working on the design of the relevant detectors. There will exist several junction boxes distributed over the ocean floor, each able to serve several observation stations.
6. Conclusions A cubic kilometre scale underwater neutrino Cherenkov telescope is under way in the Mediterranean sea. Building on the expertise from the pilot projects in the region, an EU funded design study will produce the TDR for the detector by early 2009, containing the specifications for the KM3NeT research facility. This will include the neutrino telescope as well an associated sciences node. The preparatory phase, which will start in early 2008, will be the second 3-year phase of the project, and will settle issues unresolved during the design phase. Prototyping is expected to start within the preparatory phase with construction of the KM3NeT detector starting soon afterwards.
References [1] C. Spiering, Phys. Scr. T 121 (2005) 112. [2] A. Kappes, et al., Astrophys. J. 656 (2007) 870. [3] M.D. Kistler, J.F. Beacom, Guaranteed and prospective galactic TeV neutrino sources, Phys. Rev. D 74 (2006) 063007. [4] The AMANDA home page, hhttp://amanda.uci.edu/i. [5] The ANTARES home page, hhttp://antares.in2p3.fri. [6] The IceCube home page, hhttp://icecube.wisc.edu/i. [7] F. Aharonian, et al., H.E.S.S. Collaboration, preprint astro-ph/0511678 (2005). [8] F. Aharonian, et al., H.E.S.S. Collaboration, Astron. Astrophys. 437 (2005) L7. [9] The NEMO home page, hhttp://nemoweb.lns.infn.it/i. [10] The NESTOR home page, hhttp://www.nestor.org.gr/i. [11] The KM3NeT home page, hhttp://www.km3net.orgi. [12] European Strategy Forum on Research Infrastructures (ESFRI), hhttp:// cordis.europa.eu/esfri/home.htmli. [13] S. Kuch, Design studies for the KM3NeT neutrino telescope, Ph.D. Dissertation, University Erlangen-Nuremberg, Erlangen, Germany, 2007. [14] G. Aggouras, et al., NESTOR Collaboration, Nucl. Instr. and Meth. A 552 (2005) 420. [15] T. Chiarusi, et al., NEMO Collaboration, Environmental parameters and water characteristics from deep-sea surveys at the NEMO sites, in: Proceedings of the International Cosmic Ray Conference (ICRC05), Pune, India, August 2005. [16] P. Kooijman, et al., Photonic readout of optical modules in neutrino telescopes, in: Proceedings of the International Cosmic Ray Conference (ICRC07), Merida, Mexico, July 2007.
ARTICLE IN PRESS C. Markou / Nuclear Instruments and Methods in Physics Research A 595 (2008) 54–57
[17] P. Kooijman, et al., Multi-PMT optical module for undersea neutrino telescopes, in: Proceedings of the International Cosmic Ray Conference (ICRC07), Merida, Mexico, July 2007. [18] M. Taituti, Optical module for deep-sea neutrino telescopes, ICATPP07, Como, 2007. [19] A. Braem, et al., The X-HPD—conceptual study of a large spherical hybrid photodetector, CERN-PH-EP/2006-025.
57
[20] A. Leisos, A sea-top infrastructure for calibrating an underwater neutrino telescope, TeV particle astrophysics 2007, Venice, Italy, 27–31 August 2007. [21] P. Sapienza, Status of the NEMO project, in: Proceedings of the 20th European Cosmic Ray Symposium (ECRS 2006), Lisbon, Portugal, September 2006, e-Print: astro-ph/0611105. [22] E. Anassontzis, et al., Towers and KM3NeT, in: Proceedings of the Very Large Volume Neutrino Telescope (VLVnT2), Catania, Italy, November 2005.
Contents lists available at ScienceDirect
Nuclear Instruments and Methods in Physics Research A journal homepage: www.elsevier.com/locate/nima
KM3NeT: Toward a cubic kilometre volume neutrino telescope in the Mediterranean Sea C. Markou Institute of Nuclear Physics, NCSR ‘Demokritos’, Agia Paraskevi Attikis, Athens 15310, Greece
For the KM3NET Consortium a r t i c l e in f o
a b s t r a c t
Available online 8 July 2008
High energy neutrino astronomy is emerging as one of the most exciting options for studying astrophysical processes. To establish neutrino detectability from specific sources, neutrino telescopes of 3 km scale are needed. In order to complement the IceCube detector currently under construction in the South Pole, a corresponding Northern Hemisphere detector is needed. The three neutrino telescope projects in the Mediterranean, ANTARES, NEMO and NESTOR have joined forces in order to develop, prepare, construct and operate such a research facility, KM3NeT. To this end, the EU is funding a 3-year design study. In the present paper, the status of the design study is presented and options for the various technical problems are discussed. & 2008 Elsevier B.V. All rights reserved.
Keywords: Neutrino astronomy Neutrino telescopes KM3NeT
1. Introduction Detecting high-energy neutrinos from specific astrophysical sources will be a major step towards understanding various particle physics related processes which occur in the universe. These neutrinos can be detected by water/ice Cherenkov telescopes. Such detectors can contribute to the study of Active Galactic Nuclei (AGN), Supernova Remnants (SR) or microquasars, Gamma Ray Bursts (GRB), etc. At the same time, questions like the search for neutrinos from the decay of dark matter particles (WIMPs), magnetic monopoles and other exotic particles can be addressed [1]. As recent studies indicate [2,3], these signatures 3 will only be accessible through detectors of km scale or even larger. Current telescopes like AMANDA [4] and ANTARES [5] are too small for this task. The IceCube [6] telescope, under construction at the South Pole 3 will have an instrumented volume of 1 km . Being a downward looking detector, the sensitivity to the southern sky will be limited. This limitation includes regions of the Galactic plane containing a multitude of possible high energy neutrino sources, like SR, microquasars, pulsar wind nebulae as well as several unassociated gamma-ray sources as reported by the H.E.S.S. telescope [7,8]. A logical conclusion is that a complementary detector in the Northern Hemisphere is needed to cover the whole sky.
E-mail address: [email protected] 0168-9002/$ - see front matter & 2008 Elsevier B.V. All rights reserved. doi:10.1016/j.nima.2008.07.009
In the Mediterranean Sea, three pilot projects, namely ANTARES [5], NEMO [9] and NESTOR [10] have joined forces in order to design, develop, construct and operate such a neutrino telescope, KM3NeT [11]. Apart from the accumulated expertise, the Mediterranean Sea offers some unique advantages for such an endeavor, namely, deep waters close to the shore, proximity of infrastructures, clean waters and large windows of good weather periods for the necessary sea operations. The KM3NeT collaboration currently consists of 37 Institutes from 10 European Countries (Cyprus, France, Germany, Greece, Ireland, Italy, Netherlands, Romania, Spain, UK). The KM3NeT facility is meant to be an interdisciplinary research infrastructure, serving, in addition, as a deep water facility for associated sciences, like marine biology, oceanography, geology, geophysics and environmental sciences.
2. Status of KM3NeT Within FP6 the EU has initiated a 3-year research and development phase for KM3NeT. This design study started in February 2006, and will conclude in 2009 with the publication of the Technical Design Report (TDR) for KM3NeT. In early 2008, the Preparatory Phase (PP) of KM3NeT will start, overlapping for one year with the design study. The PP will be funded by FP7 and will address the political, governance, financial, strategic and sociopolitical issues of KM3NeT, including the site selection. The PP will also include prototyping work, in view of the start of the telescope construction in 2011. The time schedule of KM3NeT is such that the construction is expected to start early in the next decade,
ARTICLE IN PRESS C. Markou / Nuclear Instruments and Methods in Physics Research A 595 (2008) 54–57
55
string layout
allowing the completion and operation of KM3NeT concurrently with IceCube. The overall cost of KM3NeT is estimated to be 220–250 MEuro. KM3NeT is part of the ESFRI (European Strategic Forum on Research Infrastructures) roadmap [12] for future large scale infrastructures, being recognized as a research infrastructure of pan-European interest.
600 400 200 0 -200 -400 -600
-600
-400
-200
0 x [m]
200
0 x [m]
200
400
600
string layout 800 600 400 200 y [m]
The design study aims at providing design options for various components and detector configurations so as to deliver a detector with the best sensitivity for physics studies. The minimum requirements in terms of performance are an instrumented 3 volume of at least 1 km , with angular resolution of about 0:1 for neutrino energies above 10 TeV, sensitivity to all neutrino flavors, and a lower energy threshold of a few hundreds GeV (and around 100 GeV for pointing sources). Neutrino Cherenkov telescopes consist of a (usually) large number of photo-detection units, typically optical modules (OMs) containing one or more photomultiplier tubes (PMTs) for the detection of Cherenkov light. The OMs used in existing experiments, contain one large PMT (typically 10 in.) enclosed in a protective, pressure resistant, waterproof glass sphere. These OMs are arranged so as cover the instrumented volume, grouped in vertical structures with equal spacing between units. The specific choice of PMT size and arrangement in the OM as well as the layout of OMs in the instrumented volume have become the subject of detailed simulation, in order to optimize the sensitivity of the detector. In the context of the design study, various OM configurations and detector layouts have been simulated [13]. Examples of possible OMs can be seen in Fig. 1. These include OMs with a single large PMT, double OMs, and OMs with many small PMTs inside. A large number of detector layouts have been evaluated, with the vertical strings arranged in cuboid, ring, hexagonal, clustered or mixed layouts (Fig. 2). In all cases the total instrumented volume has been kept constant to 3 1 km and the total area of photocathode was kept constant. The effective area for muons as a function of muon energy is shown in Fig. 3 where the KM3NeT configuration-1 detector is a hexagonal array consisting of 127 vertical strings each with 25 OMs, 100 m horizontal spacing, 15 m vertical spacing between OMs and three large PMTs per OM, similar to the ANTARES configuration. In the same figure, the configuration-2 detector corresponds to a structure of 225 vertical strings arranged in a cuboid grid with interline spacing of 95 m, 36 stories, vertical spacing between OMs 16.5 m, with each OM containing 21 3 in. PMTs. The effective area calculation includes full simulation of the neutrino interaction, muon propagation, Cherenkov light transmission, track reconstruc-
y [m]
3. Detector optimization
0 -200 -400 -600 -800 -800
-600
-400
-200
400
600
800
Fig. 2. Examples of the detector layout: cuboid (top), ring (bottom) [13].
tion and event selection. Optical noise including 40K decays in sea water was added, as measured by NESTOR [14] and NEMO [15] in the respective sites. The higher effective area of the two KM3NeT detector configurations compared to IceCube can be explained partly in terms of the higher photo-cathode area and partly to the better angular resolution of the water detector. With similar configurations KM3NeT will have a sensitivity one order of magnitude higher than existing experiments.
4. Detector components and procedures
Fig. 1. Various options of optical module designs: (from left to right) single 10 in. PMT, multi-PMT OM, double PMT OM [13].
In designing the detector, the KM3NeT consortium can build upon the expertise of previous experiments, both in water (like DUMAND, Baikal, ANTARES, NEMO and NESTOR) and in ice
ARTICLE IN PRESS
Neutrino effective area (m2)
56
C. Markou / Nuclear Instruments and Methods in Physics Research A 595 (2008) 54–57
102
preliminary
10 1 10-1
Antares
10-2
IceCube KM3NeT configuration 1
10-3 10-4
KM3NeT configuration 2
2
2.5
3
3.5 4 4.5 log10 (E [GeV])
5
5.5
6
Fig. 3. Muon effective area as a function of energy for two KM3NeT layouts, IceCube and ANTARES [13].
(AMANDA, IceCube). Several key lessons have been learned from each of these projects. The highly hostile environment in which the detector has to operate, dictates the most crucial requirement on the system and its components, namely the reliability of the off-shore parts. Evidently, the recovery and repair of faulty components from the deep sea is both very difficult as well as costly and time consuming. Therefore, high reliability of all deep sea components is absolutely essential. One major design choice towards improving reliability is to simplify the design and reduce the number of underwater-mated connections. In the context of the design study, several options are being studied and evaluated. For example, the optical and acoustic calibration units which are used for timing calibration and for monitoring the positions of OMs, respectively, could, in principle, be separated from the OMs. Also under study is the possibility of transmitting all data to shore via optical fibre and reduction of the in-sea electronics using a photonics-based network [16]. In this scenario, the OM signal is flagged in a local optical modulator interrogated by an optical signal from the shore. The modulated signal is timestamped on shore, thus necessitating no off-shore laser for data transmission. Additional research and development is under way to evaluate the performance of OMs containing many smaller PMTs. These have the advantage of higher quantum efficiency, better single photon resolution, smaller transit time spread, and provide directionality which helps reducing noise from bioluminescence and 40K. A prototype is being built and evaluated at NIKHEF [17]. Also under investigation is the use of 10 in. PMTs with segmented photocathode area [18], as another way of gaining directionality, as is the evaluation of the performance of crystal hybrid PMTs [19]. In order to calibrate the angular resolution, absolute position and angular offset, the use of a floating sea-top array in the spirit of IceTop is under investigation [20]. The position of the sea-top detector can be determined via GPS, and signal from extensive air showers to calibrate the underwater detector. Preliminary studies indicate that three floating stations at distances of 20 m equipped with 16 m2 of scintillator each will be sufficient. The production model for the components should ensure that the detector can be built within a logical time frame. This corresponds to a construction time of about 3 years, if KM3NeT is going to be operational concurrently with IceCube. With a total of about 10,000 OMs distributed over 250 detector units, plus around 25 additional calibration lines, the production line should be able to handle 15 OMs per day, and complete 10 detector lines and one calibration line per month. This probably means that five production lines will be needed, with adequate logistics and quality control systems in place.
The size of the detector implies that new ways of sea deployment will have to be developed. The ANTARES mode of deployment with separate operations for the line deployment and the cable connection with a submersible is time consuming and impractical for a detector the size of KM3NeT with around 250 lines. A possible solution could be the method proposed by the NEMO collaboration in which each line is ‘‘rolled-up’’ in a container [21]. The line equipped with a release mechanism which unfolds the line after the container reaches the sea floor. By connecting several of these compact containers together, one sea operation will suffice for the deployment of several lines. Such a deployment model reduces both the time for interconnection of lines and the number of wet-mateable connections which are a significant source of potential failures. The feasibility of such a deployment model has been successfully demonstrated by the NESTOR collaboration when they deployed a tower module without any underwater operation [22].
5. Associated sciences The KM3NeT research facility will also serve the community of marine and geophysical sciences. The existence of dedicated and permanent sea-to-shore connections is a very desirable feature. Indeed, there is a separate working group within the KM3NeT design study, working on the design of the relevant detectors. There will exist several junction boxes distributed over the ocean floor, each able to serve several observation stations.
6. Conclusions A cubic kilometre scale underwater neutrino Cherenkov telescope is under way in the Mediterranean sea. Building on the expertise from the pilot projects in the region, an EU funded design study will produce the TDR for the detector by early 2009, containing the specifications for the KM3NeT research facility. This will include the neutrino telescope as well an associated sciences node. The preparatory phase, which will start in early 2008, will be the second 3-year phase of the project, and will settle issues unresolved during the design phase. Prototyping is expected to start within the preparatory phase with construction of the KM3NeT detector starting soon afterwards.
References [1] C. Spiering, Phys. Scr. T 121 (2005) 112. [2] A. Kappes, et al., Astrophys. J. 656 (2007) 870. [3] M.D. Kistler, J.F. Beacom, Guaranteed and prospective galactic TeV neutrino sources, Phys. Rev. D 74 (2006) 063007. [4] The AMANDA home page, hhttp://amanda.uci.edu/i. [5] The ANTARES home page, hhttp://antares.in2p3.fri. [6] The IceCube home page, hhttp://icecube.wisc.edu/i. [7] F. Aharonian, et al., H.E.S.S. Collaboration, preprint astro-ph/0511678 (2005). [8] F. Aharonian, et al., H.E.S.S. Collaboration, Astron. Astrophys. 437 (2005) L7. [9] The NEMO home page, hhttp://nemoweb.lns.infn.it/i. [10] The NESTOR home page, hhttp://www.nestor.org.gr/i. [11] The KM3NeT home page, hhttp://www.km3net.orgi. [12] European Strategy Forum on Research Infrastructures (ESFRI), hhttp:// cordis.europa.eu/esfri/home.htmli. [13] S. Kuch, Design studies for the KM3NeT neutrino telescope, Ph.D. Dissertation, University Erlangen-Nuremberg, Erlangen, Germany, 2007. [14] G. Aggouras, et al., NESTOR Collaboration, Nucl. Instr. and Meth. A 552 (2005) 420. [15] T. Chiarusi, et al., NEMO Collaboration, Environmental parameters and water characteristics from deep-sea surveys at the NEMO sites, in: Proceedings of the International Cosmic Ray Conference (ICRC05), Pune, India, August 2005. [16] P. Kooijman, et al., Photonic readout of optical modules in neutrino telescopes, in: Proceedings of the International Cosmic Ray Conference (ICRC07), Merida, Mexico, July 2007.
ARTICLE IN PRESS C. Markou / Nuclear Instruments and Methods in Physics Research A 595 (2008) 54–57
[17] P. Kooijman, et al., Multi-PMT optical module for undersea neutrino telescopes, in: Proceedings of the International Cosmic Ray Conference (ICRC07), Merida, Mexico, July 2007. [18] M. Taituti, Optical module for deep-sea neutrino telescopes, ICATPP07, Como, 2007. [19] A. Braem, et al., The X-HPD—conceptual study of a large spherical hybrid photodetector, CERN-PH-EP/2006-025.
57
[20] A. Leisos, A sea-top infrastructure for calibrating an underwater neutrino telescope, TeV particle astrophysics 2007, Venice, Italy, 27–31 August 2007. [21] P. Sapienza, Status of the NEMO project, in: Proceedings of the 20th European Cosmic Ray Symposium (ECRS 2006), Lisbon, Portugal, September 2006, e-Print: astro-ph/0611105. [22] E. Anassontzis, et al., Towers and KM3NeT, in: Proceedings of the Very Large Volume Neutrino Telescope (VLVnT2), Catania, Italy, November 2005.