The Present Development of CsI Rich Detectors for the ALICE Experiment at CERN

The ALICE Collaboration plans to implement a 12m^2 array consisting of 7 proximity focussed C6F^14 liquid radiator RICH modules devoted to the particle identification in the momentum range: 1 GeV/c - 3.5 GeV/c for pions and kaons. A large area CSI-RICH prototype has been designed and built with the aim to validate the detector parameter assumptions made to predict the performance of the High Momentum Particle Identification System (HMPID) of the ALICE Experiment. The main elements of the prototype will be described with emphasis on the engineering solutions adopted. First results from the analysis of multitrack events recorded with this prototype exposed to hadron beams at the CERN SPS will be discussed<P>List of Figures<UL><LI>Figure 1 <A HREF="ALICE_LAYOUT.EPS">General view of the ALICE lay-out</A><LI>Figure 2 <A HREF="RICHSCHEME.EPS">Schematic layout of the fast CsI-RICH</A><LI>Figure 3 <A HREF="HMPID_BARREL.EPS">Perspective view of the HMPID layout with the seven RICH modules tilted according to their position with respect to the interaction vertex. The frame that supports the detectors is also shown</A><LI>Figure 4 <A HREF="WIREFRAME.EPS">Top view of the photodetector anode plane with the wire support spacer. One CsI board, out of six forming the pad cathode plane, is also shown.</A><LI>Figure 5 <A HREF="RADIATORS.EPS">Perspective view of the HMPID honeycomb panel with the three radiator vessels</A><LI>Figure 6 <A HREF="ARTISTVIEWRICH.EPS">Cut away view of the HMPID CsI-RICH showing separately each detector component. Kapton buses that carry signals from the pads to the readout electronics are also shown</A><LI>Figure 7 <A HREF="ANGLERMS.EPS">a)number of resolved photoelectrons per event, b)reconstructed Cherenkov angle per photon</A><LI>Figure 8 <A HREF="C6F14.EPS">C6F14 transmission plots before and after the molecular sieve purification</A><LI>Figure 9 <A HREF="R1873_117.PS">Display plot showing an SPS event. Three tracks are reconstructed by using the tracking chamber telescope, the associated rings are shown in the HMPID prototype</A></UL><P>This publication also appears as <A HREF="http://consult.cern.ch/alice/Internal_Notes/1998/20/INT-98-20.ps">INT-98-20</A>.