Stuck in 'Follow Freeman' (SPOILERS)

[HalfBob42]

I'm at the part where this ion cannon shoots beams from the sky. What the heck am I supposed to do? Barney keeps saying I need to go 'inside' to shut it down over and over again, but all the ways in are closed.

 

[KagePrototype]

Go all the way right, around the rubble, and into a building. You can go through this building and past the first set of forcefields. Then sprint across to the other side of the courtyard, and you can do the same here. Once you're past all the forcefields, the suppressor won't try to get you anymore, though you'll have a few combine to deal with. Then you go all the way to the right of the building, pull out the plug, and get through the forcefield, letting you into the building.