24-11-2021 | | By Robin Mitchell
Recently, researchers have been able to modulate a beam of neutron radiation to encode digital information. What challenges does traditional electromechanical radiation face, what did the researchers achieve, and could particle beams be used for digital information transmission in the future?
The electromagnetic spectrum encompasses everything from radio waves to gamma waves, and almost all parts of the spectrum have been used in some form of communication. Radio waves are ideal for sending information over vast distances, microwaves are great for high bandwidth over shorter distances, visible light enables fibre optic internet, x-rays produce internal images of the body, and gamma rays can even be used for imaging.
While the entirety of the EM spectrum can be used for many applications, there are some drawbacks to electromagnetic radiation in general. One of these is that EM waves, being waves, can diffract, reflect, and refract, which interferes with the transmission of data itself. For example, radio waves can diffract around buildings and landmarks to create interference and reduce the intensity in the received signal.
EM waves also struggle to transmit through certain mediums, with water being a classic example. Underwater communication with EM waves is tough to achieve; radio waves of extreme lengths have very low bitrates while visible light has a maximum range depending on its brightness (practically, this is less than 100 meters). Microwave radiation around 2.4GHz is ideal for use with technologies such as Wi-Fi but can barely penetrate water due to the hydrogen atoms in water molecules perfectly absorbing this frequency.
Recently, researchers from Lancaster University, in partnership with Jozef Stefan Institute in Slovenia, have created a neutron beam that can be modulated with a digital signal to transmit information. The setup utilises a californium-252 sample that emits fast neutrons (i.e., those with energies around 1 Mev with speeds of 14,000 km/s), which is then placed behind a screen. The screen is connected to an actuator that sits on rails, and the resulting beam intensity depends on whether the screen is in front of the beam or not.
However, unlike a laser beam, the fast neutron beam is only partly blocked as fast neutrons can travel through thick materials with relative ease (far easier than electromagnetic radiation). Thus, the detector used by the researchers would detect between 100 counts and 400 counts of neutron radiation if the screen was closed or open.
The researchers used bit times of approximately 10 seconds and transmitted data using a protocol similar to UART. This was the ability to send messages with 100% accuracy and no loss of bits. These results were confirmed with control messages and pseudo-random number generation to verify that the emitter and receiver had the same information.
While the neutron beam takes several orders of magnitude longer to convey information than radio (tens of seconds per bit as opposed to nanoseconds per bit), its ability to pass through materials like metal makes it an excellent choice for safety-critical applications.
For example, marine bulkheads are layers of steel that prevent water from leaking into ships, and these layers need to have as little breakage as possible. Installing communication cables in bulkheads can cause points of weakness as cables need to be routed through various layers. Still, a neutron beam would be able to go through such layers without degrading.
Particle beams could also be useful in areas with thick shielding, such as nuclear reactors. The use of a neutron beam communication device could enable data to be transmitted through layers of metal to prevent radioactive elements from leaking.
Particle beams also have the advantage that they do not diffract like waves due to their particle nature (of course, particles can also behave like waves, but making neutrons diffract is only possible with extremely small gaps). As such, a particle beam in space could be used to transmit information over vast distances that would otherwise be impossible with electromagnetic radiation while retaining a good single to noise ratio.
Overall, the researchers demonstrated a communication technology that can be used to go through materials that electromagnetic radiation simply cannot. This does not mean that neutron beam transmission will be the next big thing (as its bit rate is unbelievably low). Still, it does mean that some key applications could explore its use where traditional communication methods are not suitable.