After you narrowly avoid vaporization by the High Energy Pellet, you reach Test Chamber 07.

Pellets and an Unstationary Scaffold

As with the previous test chamber, you need to make the high energy pellet go into the containment machine. There is an orange portal below the containment machine, so create a blue portal where the pellet is hitting the wall, indicated by the dark spot.

Once you do that, the Unstationary Scaffold starts moving. Create a blue portal on the ceiling above the left side of the scaffold path, and then drop through the orange portal when the scaffold is below. If you want to be sure that you position the blue portal correctly, stand below the scaffold when it's under the ceiling part where a portal can be made, then wait for it to move.

After the scaffold takes you to the exit, go into the elevator to reach Test Chamber 08.