Proton packs are essencially nuclearaccelerators that are used to accelerate particles also known as Particle throwers .
The particles create an energy stream or ribbon used to catch ghosts , it does not trap them only direct them to the ghost trap witch is emptiend in the containment unitinside the Ghostbusters firehouse headquarter basement .
Important to note that particle stream or ribbons should not be crossed or enter in contact with each other because the results could be catastrophic according the Egon Spengler in the first movie , yet in the 2009 Ghostbusters game simply cause some painful thingling to the characters .
In the 2009 games it is also noted that the packs can be upgraded with slime thrower and other types of energy beams to help the Ghostbusters cope with different kinds of spooks .
Note that in the pilot episodes of The real ghostbuster the ecto 1 have a particle thrower canon mounted on a seat on the hearse roof witch can also be seen in the toy version of Kenner , and in the DS version , the only one you can actually control the ecto 1A you can use a similar particle thrower .