STERILX

A new type of X-ray tube that overcomes the amplitude and energy distribution limits of existing commercial sources. The system is based on the use of laser diodes with fibre output, so as to bring the electron source to operate at high voltage. In doing so, the accelerated electron beam is sent to ground, benefiting from a better disposal of the heat produced on the anode, and a better focus. This type of tube lends itself to the emission of soft X-rays that can be used for sterilisation of hospital environments and medical equipment.

Currently, more than 90% of X-ray tubes on the market operate with ground cathode and high-voltage anode. On the cathode there is an electron emitter, usually a filament that delivers up to a few tens of mA of electrons into the vacuum via thermionic emission, supplied with electrical power of about ten watts. Such tubes have two fundamental limitations:

1. 1. 1. voltage and current cannot be varied in short periods of time, in the order of milliseconds, due to the thermal inertia of the filament. This limits the use in some radiological practices.
      2. In the commercially available X-ray tubes, the anode is placed at high voltage and consists of a piece of tungsten immersed in a copper cylinder, arranged at 45° to the incident electron beam. For voltages around 100 kV, the X-ray production efficiency is 1%. The anode geometry currently used results in an inhomogeneous amplitude and intensity spectrum at the output, which requires the use of aluminium filters to make homogeneous the beam incident on the patient or on the surfaces to be irradiated.

This technology eliminates the two problems listed above through two new configurations:

1. 1. 1. High-voltage cathode and filament lit by a laser.
      2. Ground anode consisting of a tungsten and synthetic diamond sandwich connected to a copper plate.

The technology makes it possible to generate X-rays with a much more homogenous amplitude and intensity spectrum than the current tubes on the market, and at the same time to better disperse the power from the sandwich to the copper plate.

Further developments include the use of innovative materials to replace the classic filament in X-ray tubes that, when illuminated by light at 260 nm, emit electrons by photoelectric effect with great efficiency.