High Density Spiral Projection Chamber (hdspc): Design Of The Endcap Detectors Of The Obelix Experiment At Lear.

We discuss the design of a cylindrical high density projection chamber [1] that uses the spiral projection chamber [2] geometry and will instrument the end-caps of the proposed OBELIX [3] experiment at LEAR. This detector-high density spiral projection chamber (HDSPC [4])- has axial symmetry, radial drift electric field, a radiator made of converter disks alternating with drift volumes and the amplification and readout region in the outer part of the cylinder. It is equipped with FADC electronics and reconstructs in three dimensions primary ionization produced in the active volume. It features fine granularity and high angular resolution near the beam pipe and appears particularly advantageous for λ and prong detection in the forward and very forward region of storage rings and extracted beam experiments.