ADA (short for Anello Di Accumulazione) was the first Italian particle accelerator and the first-ever electron–positron particle collider measuring around 4 feet in diameter which was designed to store beams of 250 MeV. 
The AdA collider was built at the LNF in Frascati in the year of 1961 with the help of a group of Italian physicists guided by the Austrian physicist Bruno Touschek (the individual to propose the idea of its development). During the time of ADA’s proposal, many American physicists were distancing themselves from using accelerators that sent a beam of particles into a fixed target to experiment with colliding two beams of particles instead. ADA was a great extension of this idea as it replaced one of the beams of particles (electrons) with a beam of antiparticles (positrons), a modification that was new and never before tested by physicists. 
After the machines construction, it was operated from 1961 to 1964, by the National Institute of Nuclear Physics, in Frascati, Italy. However, in the year 1962, the machine was relocated to the Laboratoire de l’Accelerateur Lineaire in Orsay, France, where it was used for an additional four years alongside the laboratory’s powerful particle injector.
Towards the end of 1963, AdA’s first electron-positron collisions were recorded. Then, the machine was operated a few more years for further successful and decisive tests before dismantling. AdA was never used to collect physics data. Instead, it was a testing ground for a breed of machines that was to change the course of particle physics in the following decades.
The collider is no longer operational but the legacy of the machine still lives on today. On 5 December 2013, the Italian National Institute of Nuclear Physics [INFN] Frascati National Laboratory [LNF] was given the great honour of becoming an EPS Historic Site for the realization of the Storage Ring AdA, the first official particle-antiparticle collider. Today, the European Physical Society recognized machines grand importance to particle physics, marking it as a historic site in its original home of the Frascati National Laboratory, that is part of Italy’s National Institute of Nuclear Physics. 
Impact of the ADA Collider
The impact of the ADA Collider has been immense in enabling a new chapter of accelerator physics to be established with the machine being the first particle-antiparticle collider and the first electron-positron storage ring. In addition to this grand accomplishment the machine was also able to prove the idea that one could accelerate and collide a beam of particles and antiparticles in the same machine, that has opened the possibility for a long line of particle and antiparticle colliders and storage rings long after its lifespan, that include such machines as the Frascati National Laboratory’s ADONE(big AdA or Higher energy collider) and CERN’s (Organisation Européene pour la Recherche Nucléaire or European Organization for Nuclear Research) Large Electron-Positron collider. ADA’s success was also instrumental to the discovery of the Touschek effect in the year of 1963 that explains how the length of time a beam lasts is effected by the scattering of particles inside a beam. It also allowed scientists to witness the interaction and annihilation of particles and antiparticles during energetic collisions alongside giving physicists the opportunity to better understand several aspects of accelerator physics that would not have been possible if not for the machines existence. 
- Bernardini, C. (2004). "AdA: The First Electron-Positron Collider" (PDF). Physics in Perspective. 6 (2). Bibcode:2004PhP.....6..156B. doi:10.1007/s00016-003-0202-y.
- AdA: the world’s first electron-positron collider, December 20,2013
- First particle-antiparticle collider now historic site, December 5, 2013