The characteristics and performance of the newly commissioned neutron detector array at IUAC are described. The array consists of 100 BC501 liquid scintillators mounted in a semispherical geometry and are kept at a distance of 175 cm from the reaction point. Each detector is a $5''\times 5''$ cylindrical cell coupled to $5''$ diameter photomultiplier tube (PMT). Signal processing is realized using custom-designed home-made integrated electronic modules which perform neutron–gamma discrimination using zero cross timing and time-of-flight (TOF) technique. Compact custom-built high voltage power supply developed using DC–DC converters are used to bias the detector. The neutrons are recorded in coincidence with fission fragments which are detected using multi-wire proportional counters mounted inside a 1m diameter SS target chamber. The detectors and electronics have been tested off-line using radioactive sources and the results are presented.

This paper summarizes the results of some of the recent fusion–fission experiments carried out at the National Array of Neutron Detectors (NAND) Phase-01 installed at the Pelletron+LINAC accelerator facility of Inter-University Accelerator Centre (IUAC), New Delhi. Pre-scission neutron multiplicity excitation functions are measured for the ^213,215,217Fr, ^{210,212,214,216}Rn and ^206,210Po compound nuclei populated through the fusion of the ¹⁹F+^194,196,198Pt, ^16,18O+^194,198Pt and ¹²C+^194,198Pt systems, respectively. Pre-scission neutron yields from these reactions are compared with the extensive statistical model calculations to look for the effects due to the compound nucleus shell closure, 𝑁/𝑍 ratio of the compound nucleus, magnitude of the saddle-point shell corerction and fission time-scale.