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Exploring the properties and proposed theories of antimatter

Alex Escobar

on 18 January 2013

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Transcript of Antimatter

The other side of matter Antimatter Introduction History History Antimatter in the Universe Facts Antiparticles in the lab Applications of Antimatter •Antimatter used to be a concept only found in science fiction movies and literature. However ever since its discovery in the 20th century, it is not considered a thing of science fiction. Antimatter is an important topic in particle physics. •This equation was similar to the Schrödinger wave equation for electrons. This was a problem because classical theories suggested that the charge of an electron is negative. Although it has not been experimentally confirmed, existing theory predicts that antimatter behaves the same to gravity as normal matter. Antimatter is not antigravity. •Where is the antimatter in the universe? This is a very puzzling question for physicists because they detect normal matter almost everywhere they look in the universe. •In the following years new accelerators at CERN, Geneva, and Brookhaven, USA, made possible the production and observation of other antiparticles. •In normal matter, electrons have a negative charge and protons have a positive charge. But in antimatter, electrons have positive charge and protons have negative charge. •A British physicist named Arthur Schuster first used the term “antimatter” when he wrote letters to a scientific journal called Nature in 1898. •Today, scientists around the world are studying antimatter in order to understand and answer questions about all the matter found in our universe. •In simple terms, antimatter is made up of antiparticles which have the same mass as regular particles except that they have opposite charge. •Just like normal particles, antiparticles combine with each other to form what is known as antimatter. •Electrons with positive charge are called positrons and protons with negative charge are called anti protons. •In 1928, the British physicist Paul Dirac came up with an equation, known as the Dirac Equation, which combined both the theory of quantum mechanics and special relativity. •Schuster’s ideas were only speculation at that time and were not treated seriously. •Schuster proposed the idea of antiparticles, solar systems made entirely of antimatter, and even hypothesized matter and antimatter annihilating each other when coming in contact. •The Dirac Equation predicted the existence of an electron with positive charge, which Paul Dirac called an antiparticle. •Later in the 1950s came the discovery of antiprotons and antineutrons at Lawrence Berkeley National Laboratory (LBNL) in California. •Before antiprotons and antineutrons were discovered, bigger and more powerful particle accelerators had to be built in order to accelerate particles at higher energies. •He had discovered the first antiparticle which was later called a positron. This was a very significant discovery because from that moment, antimatter was no longer a topic of science fiction. •Proof of the existence of antielectrons came in 1932 when the American physicist Carl David Anderson was investigating Cosmic Rays and found a particle which behaved like an electron, but had a positive charge. Dirac wanted to know what this antiparticle was and later hypothesized that every particle has an antiparticle with same mass but opposite charge. An antielectron. However when converting energy into particles of matter, the same amount of antiparticles have to be created. The amount of energy released is proportional to the mass as shown by Einstein's famous equation E=mc^2 , which shows that matter is a form of energy But when antimatter comes in contact with normal matter, they annihilate each other and release high-energy photons (gamma rays) or other particle–antiparticle pairs. Antimatter is ruled by the same rules as normal matter. In theory, it is possible to have an antimatter solar system or an antimatter person. Combining 1 kg of antimatter with 1 kg of matter would release 1.8×1017 J of energy. Also, the value of c^2=90 000 000 000 000 000 which means that there is a lot of energy stored in a small amount of mass This means that energy can be transformed into matter and antimatter. And when you combine matter with antimatter, you get energy. Antimatter on Earth •Antimatter can be found on Earth but in vey insignificant amounts. •It is possible that galaxies made up just of antimatter do exist but are too far away to be detected. This is why NASA is trying to prove if these galaxies are real by searching for X-Rays and gamma rays signatures of annihilation in distant clusters of galaxies. •Physicists believe that both matter and antimatter were created in equal quantities when the universe was born. When the universe was younger, it had a lot more energy because it was hotter. That energy should have been enough to create equal amounts of matter and antimatter. But today, scientists don’t know why the universe seems to be made entirely of matter and not antimatter. •If there were places in the universe that were made completely of antimatter, the gamma rays produced in annihilation reactions along the boundary between matter and antimatter regions would be detectable. •Positrons have also been detected above thunderstorm clouds by the American Astronomical Society. These positrons are created by gamma-ray flashes released by electrons that are accelerated by electric fields in the clouds. •This antimatter is produced in really small quantities and within nanoseconds, it comes in contact with matter and gets destroyed as it annihilates and releases energy. This is why antimatter is very scarce on our planet. •Antimatter is also created naturally when cosmic rays from the sun penetrate our atmosphere. •Antimatter can occur naturally during the breakdown of radioactive material. Positrons are created naturally in + decays of naturally occurring radioactive isotopes, such as potassium-40. Discovery of Positrons, Antiprotons, and Antineutrons •The basic principle to produce antimatter is to get enough energy in a collision to produce antiparticles. •The following years, anti-nuclei have been produced at much higher energies. These anti-nuclei are made of antiprotons and antineutrons. •Then in 1956, the antineutron was discovered during collisions between protons at the Bevatron (Lawrence Berkeley National Laboratory) by Bruce Cork and colleagues. •Soon came the discovery of antiprotons in 1955 by physicists Emilio Segrè and Owen Chamberlain. •In 1954, a physicist Earnest Lawrence built a massive particle accelerator, called the Bevatron, that could collide together two protons at 6.2 GeV (Giga-electron-volts). •In the 50's a new accelerator in Berkeley, California reached energies sufficient to produce antiprotons and antineutrons. •As mentioned before, enough energy can produce matter. When energy is transformed into matter, equal amounts of matter and antimatter are created. •In 1995, CERN confirmed that it had successfully created nine anti-hydrogen atoms. This was done by accelerating antiprotons at relativistic speeds alongside conventional atoms. In specific cases, when passing close to the nucleus of the atom, their energy would be sufficient to force the creation of an electron-positron pair. Once in a while, the antielectron would then pair with the passing antiproton, creating a single atom of anti-hydrogen. •In 2011, the STAR detector at the RHIC in Brookhaven announced the observation of
anti-helium 4 nuclei. •Later, even higher energy accelerators at Serpukhov, Russia, and at CERN allowed scientists to produce and observe anti-helium 3 nuclei. •At the Proton Synchrotron at CERN, Antonino Zichichi and other colleagues announced that they had created the nuclei of anti-deuterium in 1965. How Positrons are Made •As mentioned before, collisions of particles with high amounts of energy produce antimatter. •Eventually a whole "shower" of electrons, positrons, and photons is made. At this point, positrons can be collected with magnets and placed in particle accelerators for more experiments. •The second nucleus is there to exchange energy and momentum with, otherwise you cannot start with a photon (zero mass) and end up with two objects with mass and conserve energy and momentum. • As electrons are deflected from their straight path, they release some energy in the form of high-energy photons. These photons can then travel near another nucleus and spontaneously become an electron-positron pair. •When high energy electrons are shot near the nuclei of atoms, the electrons will get deflected due to the electric field around the charged nuclei. If the charge of the nuclei is larger, the electrons will be deflected more frequently and at greater angles. •The electron-positron pairs created can then go scattering towards other nuclei, radiate photons which can then produce more electron-positron pairs. •In summary, electrons travelling fast enough towards a piece of material called a target (preferably made out of atoms that have a large atomic number), will have a shower of electrons, positrons and photons. How Antiprotons are Made •At CERN, the Proton Synchrotron accelerates protons to energies of 26 GeV which then collide into an iridium rod. •The composition of an antiproton is two up antiquarks and one down antiquark. •At Fermi National Accelerator Laboratory (Fermilab), antiprotons are produced in a similar way. •The antiprotons are collected using magnets in vacuum. • The protons bounce off the iridium nuclei with enough energy for matter to be created. A range of particles and antiparticles are formed. How is Antimatter Stored? •Antimatter is not something that can easily be stored in a container because it will annihilate with matter as soon as it touches. •This is how on April 26, 2011, CERN announced that they had trapped 309 anti-hydrogen atoms, for about 1,000 seconds. •It is more difficult to trap neutral antiparticles because most of them hit the walls of the trapping chamber where they annihilate with the ordinary atoms of normal matter. •Charged antimatter can be contained in a device called Penning Trap which uses electric and magnetic fields. •However the spins (angular momentum) of their subatomic particles produce a magnetic moment. This magnetic field can be influenced by an outside magnetic field which means that some anti-hydrogen atoms are attracted to it. By interacting with this magnetic field it is possible to trap anti-hydrogen atoms. •For example, anti-hydrogen is neutral and therefore is unaffected by the electric and magnetic fields used to trap the charged positrons and antiprotons. Cost of Production Uses in Medicine Antimatter as an Alternative Source of Fuel •With current technology it would cost over $ 100 000 000 000 to produce just 1 milligram of antimatter. •Also, storing antimatter is another problem because it doesn’t last very long. •It is created at such tremendous inefficiencies that making substantial quantities would drain the entire planet's power supply. •The reason for this is that the production of antiprotons is complicated since few are produced during reactions inside particle accelerators. The production rate of antimatter is very small. •Creating anti-matter is important in Positron Emission Tomography (PET) scans. •Small amounts of a radioactive substance are inserted into a person’s body. As this substance decays, positrons are produced. •A PET scan uses the gamma photons released from the annihilation of electrons and positrons. •PET scans are used for medical purposes. It is used to measure blood flow, detect cancer, and detect coronary artery disease. •When positrons annihilate with electrons in the body, gamma rays (high energy photons) are emitted. These gamma rays are detected to make a map of where this substance has spread inside the body. •As of today, antimatter is not an appropriate source of fuel because there is hardly any of it found on Earth. •Since the energy density of antimatter is higher than that of conventional fuels, an antimatter fueled spacecraft would have a higher thrust-to-weight ratio than a conventional spacecraft. Small amounts of antimatter could provide longer rocket propulsion. •If there was enough antimatter, it could be used as a fuel source to power rockets for interplanetary trips or even long interstellar voyages. •It would take about 100 000 000 000 years for the facilities at CERN to produce 1 gram or 1 mole of anti-hydrogen. •Antimatter could be used as a renewable and efficient source of fuel but the cost of producing it outweighs the benefits of the energy it could produce. Antimatter production would take a really long time to produce in today’s particle accelerators. In a magnetic field, charged particles follow curved paths, with opposite charges curving in opposite directions. Positron emitting radioisotopes are prepared by bombarding stable atomic nuclei with protons. Protons are speeded up in a particle accelerator  which then collide with the stable nuclei, and knocks out one neutron from its nucleus. The proton now occupies the position where the ousted neutron once stayed. But this atomic configuration is unstable, so the proton now decays by emitting positron. Fluorine-18 is the most commonly used radioisotope. Antimatter Rockets for Long Space Mission According to NASA, antimatter could be the most potent fuel source known to man. Once idea is to create a rocket that is propelled by a positron reactor. This is why positrons are the best choice because their annihilation releases gamma rays with about 400 times less energy than antiproton annihilation.   One danger of using antimatter is that when it annihilates with matter, it can release high energy gamma rays which are dangerous. These gamma rays can penetrate matter and even break up molecules. The NASA Institute for Advanced Concepts (NIAC) is funding a team of researchers who are currently working on a new design for an antimatter-powered spaceship. When antimatter meets matter, both annihilate in a complete conversion to energy and this is what makes antimatter so powerful. A trip to Mars would require tons of chemical fuel. But a couple of milligrams of antimatter could be enough. Antimatter Theories that need more Research One Electron Theory Any Questions? Gravitational Polarization of the Quantum Vacuum Tully-Fisher Experiment Gravitational dipole fluid • The theory derives the famous Tully-Fisher Experiment
The Tully-Fisher experiment is an empirical that is based on numerical data collected by numerous observations of galaxies and clusters Time Space During his nobel prize lecture, Feynman told a story about Wheeler calling him in the middle of the night
Wheeler told him he derived the solution to the indistinguishability of electrons
They are all the SAME electron
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