Over the past few blog posts we have gone over many different things. We have learned that antimatter is the opposite of matter, and that this has all stemmed from an equation Paul Dirac had created. But, how did we manage to verify that this is actually true? We understand and have tested what happens when antimatter and matter come into contact with each other, complete conversion of mass into energy. But, what was the first step scientists had to undertake in order carry out this experiment? Scientists are constantly carrying out many unique experiments all around the world trying to understand more about antimatter, yet there is one thing that is universal and remains constant throughout every single experiment. We discussed the possible applications of antimatter, and not one of them could be possible without this one thing scientists do. Storing antimatter would not be something that scientists are researching if this process was not possible? So what is this process I am talking about? The creation of antimatter! We have gone over many different aspects of antimatter but we have not gone over what very well may be the most important piece of knowledge, the process scientists use to create this substance they study. Well, it is actually a much simpler and less complicated process that one would believe if they have not heard it. While it may be hard to grasp without a physical sciences background, helping one understand why such things happen as they do, it is not impossible.
Scientists at CERN, The European Organization for Nuclear Research, are hard at work trying to solve the greatest problem that has arose from the discovery of antimatter, the asymmetry problem. This problem poses questions as to why there is such a high quantity of matter in the visible universe as compared to antimatter. It cannot be that antimatter is just camera shy and is hiding from the telescopes that take pictures and scans of deep space, there actually is a deficiency of antimatter in the visible universe. Nature tends to sort itself out neatly, with things often being symmetrical. Therefore, the big bang should have created equal amount of matter and antimatter, but there is virtually no antimatter in the universe. In order to find out why, they need to carry out experiments and for that they need antimatter. The experiments they carry out specifically involve collisions in the large hadron collider, in which they study the difference between matter and antimatter during these very short periods in time.
CERN has this very interesting machine called the Antiproton Decelerator (AD). This machine began its functions in the year two thousand and has been used in experiments from ATHENA, Antihydrogen production and precision experiments, which began in 2001 all the way until now while it is still being used in an experiment that began in 2014 called BASE, Baryon Antibaryon Symmetry Experiment. The tool actually requires help from something called the proton synchrotron in order to create the protons. The scientists at CERN actually use a beam of protons, which are high concentrations of a very small particle called protons, and they aim and fire it at a metal plate. Once these protons come into contact with the metal plate at high speeds, what results is a collision which seems devastating on the subatomic level. The results of this collision is actually the creation of many different subatomic particles, one type of them is the antiproton, or positron, and it comes in abundance. There is one small issue at this point however, the antiprotons are not useful to the scientists yet. They do not have the right amount of energy and cannot be controlled at this point yet. This is where the name, Antiproton Decelerator, comes from. The antiprotons actually have too much energy and they move erratically and frenziedly to the point that they are not usable. The Antiproton Decelerator is actually what slows them down, and keeps them under control. The AD will make the antiprotons usable for experiments so that scientists can understand it more. It is actually very interesting to note that the AD does not actually create these antiprotons, but it allows them to be studied. Using the same ideas as presented in the past post with magnetism and electric fields, the antiprotons created in the last step are all coming off the metal plate at different angles since they are products of a collision. They are corralled into a single entry point at which only some of these antiprotons can manage to enter. Once inside the Antiproton Decelerator, which is a glorified storage unit, magnets are used to guide the antiprotons while electric fields are used to actually slow them down. Remember when I said that at low speeds antimatter actually begins to behave like a very weak and very small magnet. This process in which the speed of the antiprotons is lowered is called cooling and they actually undergo several laps of the ring which is the antiproton decelerator until they reach a speed which is equivalent to a tenth of the speed of light. From this point, they are then ejected to be used in the experiments scientists want to conduct.
While the Antiproton Decelerator is very useful and has been around for a very long period of time, it is time for an upgrade and that is exactly what CERN had in plan. They are going to be commissioning a new decelerator called ELENA, Extra Low ENergy Antiproton. CERN states that when used in unison with the AD and the positron synchrotron, we will see the energy of these antiprotons being reduced by a factor fifty. By making the antiprotons have less energy, the beam of protons can increase its intensity, resulting in experiments that will have anywhere from ten to one hundred times more antiprotons. A new experiment which will be executed using ELENA will actually test the effects of gravity on antimatter. Overall, we can see that the future looks bright for the world of antimatter study with these stellar machines at our disposal!
Genius Hour - Antimatter 