http://en.wikipedia.org/wiki/Proton_pack wrote:
<<The Proton pack, designed by Dr. Egon Spengler, is a man-portable particle accelerator system that is used to create a charged particle beam - composed of protons - that is fired by the proton gun. Described in the first movie as a "positron collider", it presumably functions by colliding high-energy positrons to generate its proton beam. The beam allows a ghostbuster to contain and hold "
negatively charged ectoplasmic entities". This containment ability allows the wielder to position a ghost above a trap for capture. The doorman to the Mayor's mansion also uses the term proton pack as a toy for his little brother. Egon then replies that "A proton pack is not a toy."
While the Ghostbusters' dialogue indicates that the accelerator system operates similarly to a cyclotron (and indeed Dr. Peter Venkman refers to the proton packs in one scene as "unlicensed nuclear accelerators"), modern particle accelerators produce well collimated particle beams. This is far different from the beam from a proton pack, which tends to undulate wildly (though it still stays within the general area at which the user is aiming). The proton stream is quite destructive to physical objects, and can cause extensive property damage.
Each pack's energy cell has a half-life of 5,000 years. Knobs on the main stock of the Proton Pack can perform various functions to customize the proton stream, including adjustments for stream intensity, length, and degrees of polarization.
"
There's something very important I forgot to tell you! Don't cross the streams… It would be bad… Try to imagine all life as you know it stopping instantaneously and every molecule in your body exploding at the speed of light." —Egon Spengler/Harold Ramis on crossing proton streams
Crossing the streams was initially discouraged, as Egon believed that "total protonic reversal" would occur: this effect would have catastrophic results. However, in a desperate effort to stop the powerful Gozer the Gozerian, Egon noted that the door to Gozer's temple "swings both ways" and that by crossing the streams, they may be able to create enough force to close the door on Gozer and its control. As the Ghostbusters cross the streams, the combination of that much energy closes the door to Gozer's dimension and severs its ties to our world. The resulting blast destroys a good portion of the roof and blows up the Stay Puft Marshmallow Man.>>