Abstract: A portable x-ray tube 68 for producing x-rays, the tube 68 having an energy source 74 which directs energetic particles or photons at an electron multiplier 80 coupled to the energy source 74. A voltage source 84 applies a multiplier voltage across the electron multiplier 80. When triggered by the energy source 74, the electron multiplier 80 creates a multitude of electrons 28 directed towards a target anode 90 that receives the electrons and produces x-rays 30. The target anode 90 is coupled at a voltage difference of at least 3 kV relative to the electron multiplier 80 so as to define an electron acceleration region 32 between the electron multiplier 80 and the target anode 90. The target anode 90 contains an element having an atomic number greater than 11. A low pressure enclosure 70 contains the electron multiplier 80 and the target anode 90. The low pressure enclosure 70 includes a window 92 for allowing the x-rays 30 to pass through substantially unchanged.