Demonstrator Detection System for the Active Target and Time Projection Chamber (ACTAR TPC) project

The design, realization and operation of a prototype or demonstrator version of an active target and time projection chamber (ACTAR TPC) for experiments in nuclear physics is presented in detail. The heart of the detection system features a micromegas gas amplifier coupled to a high-density pixelated pad plane with square pad sizes of 2 x 2 mm(2). The detector has been thoroughly tested with several different gas mixtures over a wide range of pressures and using a variety of sources of ionizing radiation including laser light, an alpha-particle source and heavy-ion beams of Mg-24 and Ni-58 accelerated to energies of 4.0 MeV/u. Results from these tests and characterization of the detector response over a wide range of operating conditions will be described. These developments have served as the basis for the design of a larger detection system that is presently under construction.