Only one in a million collisions creates an antiproton
been equal amounts of each just after the Big Bang – so why are we, and everything we touch, made of matter? Many physicists around the world are working on competing hypotheses to explain this conundrum and so far there is no consensus within the scientific community about how to explain the phenomenon. One of the two current most popular explanations is something known as ‘Charge Parity Violations’, a remarkably simple theory that states that some reactions happen more easily than others, meaning that matter was more commonly produced in the conditions directly after the Big Bang than antimatter. However, in order to assume this, we would need to change some of the most fundamental laws of physics. The other explanation states that large parts of our universe is made of antimatter, thereby restoring the imbalance, but this turns our problem from one of creation to one of separation. How and why are they separated? Why haven’t we seen any of it and why is it not annihilating? These questions are challenging scientists the world over. The wonderfully mysterious antimatter has some very real and useful applications in the modern world. The first is medical imaging: the ‘anti’ twin of the more well-known proton is the antiproton, which has been shown within laboratory experiments to have the potential to treat certain cancers, a method that is not too dissimilar from ion therapy. Antimatter’s other potential uses include the fuel of Star Trek ’s Starship Enterprise – of course – and as a trigger for nuclear bombs. It was discovered that nuclear weapons triggered using antimatter would be more discriminate and would therefore create less long-term contamination than conventional nuclear weapons. The future of antimatter looks exciting. It will take significant investment to turn it from being a niche experiment to a commercial industry. However, once this is achieved, its benefits will be innumerable. C ERN is formed of multiple particle accelerators that are used for all kinds of different experiments. They accelerate protons, the positive charge in an atom. Antimatter is created by crashing a proton into a metal at a high energy to create a proton and antiproton pair. First, the proton is taken from a hydrogen atom using an electric field and is then accelerated by the Linear accelerator, Linac 2, and injected into the Proton Synchrotron Booster, before being shot into the Proton Synchrotron and finally sent off from the main Large Hadron Collider and into what is called an antimatter factory, where the antihydrogen is created. What is the Anti-Proton Decelerator? Lucas Brown
The Linac 2 first picks up the proton from the hydrogen atom and then accelerates it by charging conductors alternatively. The proton is then sent into the Proton Synchrotron Booster, which is formed of four magnetic rings. They use magnetic fields that push and accelerate the particle down the empty tunnel. It also uses radiofrequency cavities to create a magnetic field. The energy of the particle increases at a high rate and is shot into the Proton Synchrotron, home to about 300 non-super conductors that over a distance of about 700 metres increase the proton’s energy to ten times its normal amount, near the speed of light. At this point the proton has enough energy to create a proton-antiproton pair when shot into a piece of metal, but only one in a million collisions creates an antiproton. The antiproton created is travelling at near the speed of light and thus has too much energy to create an atom of antimatter, so it is sent into the antimatter decelerator. This uses many superconducting magnets to keep the antiproton on the right path and more dipoles create a strong electric field to slow the particle down. The antiproton is also ‘cooled’ by sending it into a cloud of electrons, which reduces the sideways motion of the particle and its spread of energy as the charges repel. At this point, the antiproton is travelling at ten per cent of the speed of light and has sufficiently low energy to be inserted into the antimatter. They are collided with a positron, an antielectron, which is retrieved in the natural decay of Sodium-22. There is an electrostatic attraction between the positron and the antiproton, meaning that when they are both at a low enough energy they form antihydrogen. The experiments do many things to the antimatter. They often try to find its properties and, for example, they have found the charge of the antihydrogen. There have also been experiments using antihydrogen to test the gravitational pull on the antimatter. Once the antihydrogen is created, they tend to collide with matter particles, causing an annihilation. Detectors are used to see these annihilations in order to observe how antimatter reacts to matter and the particles and energy it creates in a collision. Many of these experiments have been used to explain what the universe was like at high energies with the ratio between antimatter and matter still balanced and, in doing so, to explain the origin of everything that we have ever known.
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