An x-ray tube comprising an anode and a cathode disposed at opposing ends of an electrically insulative cylinder. The x-ray tube includes an operating range of 15 kilovolts to 40 kilovolts between the cathode and the anode. The x-ray tube has an overall diameter, defined as a largest diameter of the x-ray tube anode, cathode, and insulative cylinder, of less than 0.6 inches. A direct line of sight exists between all points on an electron emitter at the cathode to a target at the anode.