Enter either door and walk around the corridor. Battle the two Skaarj Lords on patrol ad push the button. This will open the bars blocking the lift near your entry point. Leave the corridor and ride the lift up.
The two alcoves on either side of this landing hold several items including Rifle Rounds, an Assault Vest, ASMD Core, Razorblades, Flak Cannon and Bullets. Cross the force field and drop through the hole in the platform ahead to reach the entrance to the Source. Enter any of the doors.