Understanding nuclear structure and dynamics from the underlying strong force described by QCD is one of the major challenges in nuclear physics today. Exotic nuclei, with extreme ratios of proton-to-neutron number, provide an ideal playground to address key questions in nuclear physics and astrophysics.
- How does the structure of nuclei change with temperature, isospin and angular mometum?
- How does the strong force binds the nucleons together in atomic nuclei?
- What is the origin of elements in Nature?
- What are the nuclear processes involved in the evolution of the stars?
Accessing the limits of the nuclear chart is very challenging and highly innovatory equipment is required to reach further regions of the nuclear chart.
The active target and time projection chamber (ACTAR TPC) is a novel gas-filled detection system that will permit new studies into the structure and decays of the most exotic nuclei. The use of a gas volume that acts as a sensitive detection medium and as the reaction target itself (an “active target”) offers considerable advantages over traditional nuclear physics detectors and techniques. In high-energy physics, TPC detectors have found profitable applications but their use in nuclear physics has been limited. With the ACTAR TPC design, individual detection pad sizes of 2×2 mm2 are the smallest ever attempted in either discipline but is a requirement for high-efficiency and high-resolution nuclear spectroscopy. The corresponding large number of electronic channels (16000 from a surface of only 25×25 cm) requires new developments in high-density electronics and data-acquisition systems that are not yet available in the nuclear physics domain. Funded by the European Research Council (ERC) in 2014, ACTAR TPC is an ambitious project responsible for the development of a novel and versatile detector system for rare-isotope beam experiments at GANIL (France) and CERN-ISOLDE (Switzerland) and other facilities worldwide. The ACTAR TPC collaboration is composed of researchers and engineers from GANIL, CENBG, IPN Orsay in France, the K.U. Leuven in Belgium, and the Universidade de Santiago de Compostela in Spain.