There are lots of small hadron colliders. Hadrons are just composite particles made up of quarks and held together by the strong force. This includes "exotic" p

There are lots of small hadron colliders. Hadrons are just composite particles made up of quarks and held together by the strong force. This includes "exotic" particles like mesons and high energy baryons, but it also includes the "mundane" baryons such as protons and neutrons. So technically any proton accelerator is a hadron collider. Which includes the first cyclotron, a proton accelerator built in 1932 that was only 27 inches across, a very "small hadron collider" indeed.