The Particle Cannon has a very long attack range, similar to the the Nod Beam Cannon. However the Particle Cannon ridiculously over-ranged and overpowered, plus it is strong against air units which makes the turret more deadly.
A good counter to this unit are anti-structure infantry like Commandos or rocket squads. A group of three Firehawks or Vertigoes are enough to bring the turret down. Using a fully upgraded Juggernaut or Specter would do well too, but they must be at the same level to do significant damage against the Particle Cannon.