MILOM : a new major step

Last update : 01/09/2009

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The MILOM line is a version of the instrumentation line that contains a variety of instruments necessary for understanding the sea environment and for calibrating the neutrino telescope optical detector lines. It contains also optical modules intended to evaluate in the sea all aspects of the ANTARES detector ahead of full production of the 12 optical detector lines. This line, deployed and operated in 2005, follow earlier test lines deployed and operated in 1999/2000 and 2002/2003 (details).

Before the deployment of the MILOM, the ANTARES program made use of other test lines connected to the shore via undersea cables.

The first such line, referred to as the “Demonstrator Line”, was deployed in November 1999 and connected on the deployment boat to an old undersea cable going to Marseille. This line was operated until June 2000 and proved various concepts of the ANTARES design, in particular the acoustic positioning system, and included reconstruction of cosmic ray muons with 7 optical modules as shown in figure 1. This line used an already existing undersea cable donated by France Telecom to  take data in a telephone exchange centre in Marseille with the demonstrator line being located on a special site near Marseille.

In 2001 a new cable was deployed between the final ANTARES site and the shore station in La Seyne-sur-Mer and in 2002 the detector junction box was deployed and connected at the end of this cable. The next test lines were deployed and connected between November 2002 and March 2003. Two lines were deployed, the MIL, the first version of the instrumentation line and the PSL, a short prototype for a full optical detector line with 15 optical modules. These lines which were operated in situ until May/ July 2003, respectively, again proved various aspects of the design. In particular the PSL was able to measure the counting rates in the optical modules (rates of bioluminescence over a period of ~4 months. Unfortunately a faileur in the main line cable prevented the electronics to be synchronised and muons couldn't be reconstructed.

Figure 1. Reconstruction of cosmic ray muons with 1999/2000 Demonstrator Line. The plot corresponds to a total of ~70 hours of data taking. Figure 2. Data from the battery operated slow control in the junction box. The blue and green points show the measured temperature at two locations in the JB, green in the power transformer heat bath and blue in the upper hemisphere which houses the slow control systems. Red is the humidity in the upper hemisphere.
The Main Electro-Optical Cable (MEOC) and Junction Box (JB) have now been in operation for 2½ years. The MEOC was deployed in the sea in Nov. 2001, initially with only a loop-back container at the sea end. In Nov. 2002 this sea end of the cable was brought to the surface, connected to the junction box and redeployed. Since this date the battery operated slow control in the junction box has sent to shore measurements of various parameters in the JB (figure 2).

The following pages give the most important results obtained so far with the MILOM

Author : Thierry Stolarczyk