NEMO-RD

Collaboration

- INFN: Bari, Bologna, Cagliari, Catania, Genova, LNF-Laboratori Nazionali di Frascati, LNS-Laboratori Nazionali del Sud, Messina, Roma 1
- OGS Trieste
- CNR: IOF, La Spezia; IBM, Venezia; IST, Messina.

National Responsible: E. Migneco (LNS)

1. Goal of the experiment

The realization of a telescope for high-energy neutrinos of astrophysical origin is nowadays considered as one of the most important aims in the astroparticle physics field. The detection of these neutrinos could help to investigate the mechanisms giving rise to the most energetic phenomena in the Universe such as the Active Galactic Nuclei and the Gamma Ray Bursts. It is believed that such a detector must have an active volume of 1 km 3 and should be shielded from atmospheric cosmic rays. The most promising technique seems to be the detection of the Cherenkov light emitted by secondary muons produced in neutrino interaction, by means of an array of detectors located in the sea abysses at a depth of more than 3000 m.

The experimental program of NEMO-RD is to develop technologies suitable for the realization of such a detector. In particular the issues addressed are:

- study of optical and oceanographic properties of deep sea waters aimed at finding and characterize a candidate site (close to the Italian coast) for the detector installation;
- development of new low-power electronics suitable for the submarine environment
- study of the mechanical feasibility of the detector

More on the experiment...

2.

Activities during 2002

During 2002 the collaboration has continued the characterization of the deep-sea site close to Capo Passero, selected as a candidate site for the installation of the km 3 neutrino detector. Measurements of optical properties, water currents, sedimentation, optical background and biofouling have been carried out. As planned an extensive number of sea campaigns has allowed measuring optical water properties in different periods of the year, establishing the seasonal dependence of these parameters. Deep-sea optical properties have been found to be stable throughout the year, confirming the excellent characteristics of the site. During 2002 two sea campaigns, one on the Capo Passero site and one on the Toulon site where the Antares detector will be installed, have been carried out in collaboration with the Antares site exploration group. During these campaigns instruments developed by both the NEMO and Antares collaborations have been used jointly, allowing a cross check of the results. In particular the absorption length has been measured with the NEMO AC9 transmissometer and the Antares Test 3 setup. Results are in agreement showing that the absorption length in the blue region of the spectrum is 68 m in Capo Passero and 48 m in Toulon. Optical background has also been measured with two similar setups, one developed by the NEMO collaboration and one by Antares. With these setups the background due to the presence of 40K in seawater and to bioluminescence has been measured, showing that the background rate is more than a factor of 2 lower in Capo Passero (28 kHz on a 8” PMT, compatible with the unavoidable 40K background) than in Toulon (58 kHz, with a strong presence of bioluminescence).

A project for the realization of an undersea installation to be realized at the Catania LNS underwater Test Site has been developed. This project, called NEMO Phase 1, comprises all the essential components (junction boxes, flexible towers, electronics and data transmission system, cable interconnections, …) of the km 3 detector, as defined by the preliminary project developed by the collaboration, and aims at demonstrating the technological feasibility of the detector. This project, which is partially supported by the INFN, is also funded for an amount of 3 MEuro by the MIUR through a contract approved in November 2002. A further request of funding, for approximately 2 MEuro, has been submitted to the MIUR in January 2003.

The following achievements have been obtained:

- Completion of data collection at the Capo Passero Site (100 % (*))
- Realization of the storey electronics and data transmission system (70 % (**))
- Realization of a prototype of the mechanical structure for a "flexible tower" (30 % (***))

(*) an extensive number of sea campaigns has been performed on the Capo Passero site, allowing for a study of the seasonal dependence of the optical properties of the waters. However, it is foreseen to extend the data collection for the forthcoming years to allow for a long term characterization of the site.

(**) a first prototype is ready and assembled; realization of the firmware is in progress.

(***) design of the structure completed; start of the realization postponed due to delayed funding; the realization is in progress and completion foreseen by june 2003.

Milestones 2003

Realization and test in water of a 1/10 scale model of the tower | 30-04-2003
Realization of the prototype of the power and front-end electronics contained inside the Optical Module | 31-05-2003
Realization of a prototype of a tower storey | 30-06-2003
Realization of a prototype of the storey electronics | 30-09-2003
Realization of prototypes of the Optical Modules | 30-09-2003
Realization of an assembly tool for the Optical Modules (subject to the approval of a further funding request during next year - date to be defined) | to be defined
Realization of a prototype of the Junction Box (subject to the approval of a further funding request during next year - date to be defined) | to be defined

3. INFN contribution to the experiment in terms of manpower and financial support

Manpower:

The INFN participation in the experiment amounts to 58 physicists and engineers for a total of 23.5 FTE and 15 technicians (5.1 FTE). Support is also given from the mechanics and electronics workshops of the INFN’s "Sezioni" and Laboratori that are involved in the project.

Budget for the Year 2003: 1.7 % of the CSN2 budget for 2003.

4. Number of publications in refereed journals: 1

5. Conferences talks: 2

5 talks, 2 of which invited.

6. Number of undergraduate and doctoral thesis on the experiment

- Undergraduate theses (in progress) 11
- Undergraduate theses (completed in 2002) 2
- PhD theses (in progress) 5
- PhD theses (completed in 2002) 0

7. Leadership roles in the experiment

- E. Migneco — Spokesman

8. Innovative instruments

The in situ measure of the water optical properties is crucial for the characterization of the deep-sea site. Some of these properties, like the volume scattering function, have never been measured in situ before. To achieve this result the collaboration has designed and realized an instrument to measure the angular distribution of the scattered light at different wavelengths. This scatter-meter (called DEWAS) has been successfully tested in deep water (3400 m) and is now undergoing the laboratory calibrations. A study to upgrade the system sensitivity is also under way.

An instrument to measure the attenuation length of light in water has also been designed and tested in shallow waters.

Both these new instruments could find applications in marine biology and oceanographic researches.

9. Competing experiments

The goal of building a 1 km3 neutrino telescope and the related R&D activities are followed with interest by two other collaborations in the Mediterranean (NESTOR and ANTARES) planning to deploy a detector with lower effective area (demonstrator). An Italian collaboration, including physicists from the NEMO collaboration, is also invlved in the ANTARES experiment.

Baikal, one of the two astrophysics neutrino experiments at present in data taking, is limited by the shallowness of the detector and will not achieve the 1 km3 dimensions. AMANDA, the second running experiment located in the South Pole ice, is planning to reach the 1 km2 effective area (project ICE-CUBE); this experiment is at only 2000 m depth and is limited by light scattering in ice.

10. International committee which has reviewed the experiment

The experiment is reviewed by the funding authorities of INFN.

The Peer Review Committee of ApPEC will give an evaluation of the properties of the proposed sites for the neutrino telescope.