Nuclear physics experiments using accelerators

The advent of Van de Graaff, Tandem and Cyclotron Accelerators has opened up opportunities to study nuclear reactions and probe nuclear structure using both stable and radioactive particle beams with intensities ranging from 106 particles/s to several μA. In this talk we describe typical setups used in nuclear physics experiments in the study of elastic scattering, fusion, fission, particle spectra and structure of exotic nuclei. A few experiments will be taken up and described in more detail. Most setups involve the use of large detector array systems, associated electronics and data acquisition systems. Detector systems based on Silicon surface barrier detectors and strip detectors are used for particle spectroscopy. CsI detectors are used when higher efficiencies are required as in particle-gamma and fission-charged particle coincidence studies. Gas ion chambers are employed for the detection of fission fragments. Liquid scintillators are used for neutron detection. Data acquisition systems using CAMAC and VME have been developed in-house and these will be described. Current trends in integrated electronics and data acquisition, namely digital pulse processing will be described. Pulse shape discrimination (PSD) for neutron-gamma discrimination and PSD for charged particle identification will be described stressing on the newer digital techniques. In experiments with radioactive ion beams, the available beam intensities are often very low. This makes the design of the detector assemblies more challenging and it is often required to make a simultaneous measurement of neutrons, gamma-rays and charged particles in order to extract the maximum information with limited beam time. We have also undertaken offline counting, in this case optimizing the offline counting setup to allow the measurement of low cross sections. The physics information obtained from our recent experiments on fission time scales, deep sub-barrier fusion (studied using the BARC-TIFR Pelletron and LINAC accelerators) and experiments with 6He and 8He studied using the SPIRAL accelerator at GANIL will be presented. (author)