Description of the material

The region no. 3 has to be filled with sea water, which has been defined as material no. 18. In our example we have adopted one of the mixtures in use by the ANTARES experiment. In that case, sea-water is represented by the compound of 8 elements: hydrogen, oxygen, potassium, sodium, calcium, potassium chlorine and sulphur. The relative proportions are given in terms of average atom content. For the specific problem described here, there is no need of simulating e.m. showers (and in fact we have asked for EMF-OFF), there is no need of preparing a pemf file.