In an embodiment an X-ray source includes an electron source configured to emit electrons, an acceleration set-up configured to accelerate the emitted electrons and a transmission window downwards of the acceleration set-up, wherein the transmission window is configured to let through X-rays generated by the accelerated electrons, wherein the transmission window is located either in a straight extension of a line-of-flight of the accelerated electrons or off the line-of-flight and past the acceleration set-up, wherein the transmission window comprises a carbon carrier, and wherein the carbon carrier comprises sp2-hybridized carbon.

X-ray tubes that have a reduced exposure time for dental X-ray imaging and 3D dental imaging systems using these X-ray tubes are described. The X-ray tubes contain an anode, a filament, a cathode electrically connected to the filament, and a voltage source electrically connected to the cathode. The voltage source provides a high voltage to the anode relative to the cathode and filament control voltage. A low filament control voltage is used to generate electrons using a process of thermionic emission. These electrons are driven by a large electric field generated between the cathode and anode towards the target on the anode. A bias voltage is applied between the cathode and the filament to control the electron flow from the emitting filament to the anode. Such a configuration yields a switching speed ranging from about 1 ms to about 10 ms, allowing a short X-ray exposure time and a quicker overall imaging process for the 3D dental X-ray imaging systems. Other embodiments are described.

X-ray tubes that have a reduced exposure time for dental X-ray imaging and 3D dental imaging systems using these X-ray tubes are described. The X-ray tubes contain an anode, a filament, a cathode electrically connected to the filament, and a voltage source electrically connected to the cathode. The voltage source provides a high voltage to the anode relative to the cathode and filament control voltage. A low filament control voltage is used to generate electrons using a process of thermionic emission. These electrons are driven by a large electric field generated between the cathode and anode towards the target on the anode. A bias voltage is applied between the cathode and the filament to control the electron flow from the emitting filament to the anode. Such a configuration yields a switching speed ranging from about 1 ms to about 10 ms, allowing a short X-ray exposure time and a quicker overall imaging process for the 3D dental X-ray imaging systems. Other embodiments are described.