Watching this YouTube video about the LHC at around 3 minutes and 50 seconds into the video the narrator says...
For machine protection reasons we are not allowed to inject a high intensity beam into an empty machine, therefore we start injecting a very low intensity probe beam.
However the video doesn't provide any further explanation as to why a high intensity beam can't be injected into an empty machine. It goes on to say that when the high intensity beam is injected, the probe beam is kicked out.
My question is why can't (or possibly why shouldn't) a high intensity beam be injected into the LHC when the machine is empty?