My understanding is that it doesn't. Though if the energy gets high enough, you can start to get other particles out.
As for protecting one photon with a sheathe of other photons, the energy density required for that tube is absolutely insane. We're talking photons spaced the width of a proton apart, with very high energy. Even assuming that it could be assembled, the gravity from the leading edge of the tube is going to do "interesting things" to the rest of the tube. Maybe even black hole levels of interesting...
