I have a geiger counter, the specifications say it is sensitive to x-rays down to 30kev. I wonder where that number comes from? Am I correct in thinking that any x-ray photon that enters the geiger tube will register a count, regardless of it's energy? Perhaps the 30kev minimum is there to ensure that the amount of radiation being detected is accurate? What do you think? There is a large attenuation loss due to the glass walls of the geiger tube at lower energies. I ask because I wonder if the meter would be suitable as a qualitative test for danger from my experiment, which could be producing x-rays from 20-30kev. Thanks for your thoughts.