representation of a single
module of the ICARUS detector and
The ICARUS detector is composed by two semi-independent, symmetric, filled with liquid argon modules of approximately 3.6 x 3.9 x 19.9 cubic meters. The charge particles passing inside the volume, where a uniform electric field is applied, produces ion-electron pairs. A fraction of them, depending on the field intensity and on the density of ion pairs, will not recombine and will immediately start to drift parallel to the field in opposite directions. Only the motion of the much faster electrons induces a current on a number of parallel wire planes located at the end of the sensitive volume. The choice of the liquid argon was driven by the following considerations:
The read-out chambers (two TPC for each half-vessel) are mounted on the internal walls with the cathode at the centre, to maximize the LAr sensitive volume (corresponding to about 480 ton in mass). The read-out chamber scheme consists of three parallel planes of wires (horizontal, +60 and -60 degrees). Information is read both by electric charge induction on the first two readout planes encountered by drifting electrons and by electric charge collection on the last readout plane. The signals from the three wire planes, together with measurement of the drift time, provide a (redundant) full 3-D image reconstruction of the event. The main features of this type of chamber is that there is no charge amplification inside to allow the drifting electrons to induce signals on different wire planes. This requires a high quality electronics to maintain a good signal over noise ratio. The total number of electronic read-out channels is about 55000.