Preliminary informal tests with commercial NaI(Tl) were performed underground at end of the 80’s. Then, after the setting of the DAMA proposal to INFN on 1990, various R&D developments and detectors were realized, achieving also interesting results.
In 1996, a devoted study of the response to nuclear recoils induced by single neutron elastic scatterings in NaI(Tl) has been performed at ENEA-Frascati. Moreover, the comparison of the time behaviours between reference pulses for Compton events and recoils has quantitatively pointed out the possibility to statistically discriminate electromagnetic component of the counting rate – when investigating the so called WIMP class of candidates – at reasonable level by exploiting the pulse shape analysis in the experimental data.
The DAMA/NaI ( ≈ 100 kg of highly radiopure NaI(Tl) detector) experimental set-up was made by nine 9.70 kg low radioactive NaI(Tl) crystals, realized – in the framework of INFN contracts – with Crismatec company. Four 7.05 kg detectors, previously developed for SIMP search, were also placed on the top, mainly to partecipate to special triggers. All the materials of the detectors and those surrounding them, photomultipliers by EMI and shields were accurately selected by using the Germanium facility at Gran Sasso, mass and atomic absorption spectrometers and – with the highest sensitivity – testing prototypes deep underground. In particular, the PMTs were the results of a particular dedicated development. Moreover, also the growing methods and the assembling of crystals were carefully selected and specific protocols were developed.
The DAMA/NaI set-up completed its data taking in July 2002. It had as main aim the investigation of the presence of a Dark Matter particle component in the galactic halo by means of the model independent annual modulation signature. With the 0.29 ton x year total exposure it achieved a 6.3 sigma C.L. model independent evidence for the presence of Dark Matter particles in the Galactic halo. Some of the many possible corollary quests for the candidate particle have also been carried.
The same experimental set-up has also obtained several other results on other approaches and on various other rare processes (e.g. solar axion, possible Pauli exclusion principle violation, cluster decay, possible spontaneous transition on nuclei to a superdense state, Q-balls, possible charge non conserving processes, SIMPs and nuclearities, electron stability).