Despite it’s name, Positron Annihilation Spectroscopy (PAS) is actually a non-destructive method for analysing solid materials. When the positron is fired into the solid we expect it to annihilate an electron and produce a very visible gamma photon. Now if there is a defect, in particular a vacancy defect then the positrons will be able to survive slightly longer while passing through this space. It is therefore possible to observe an extended length of time, about a nanosecond, where no annihilation photon is returned revealing the presence of a defect.
Researching the basic tenants of antimatter is an interesting thing. If a lack of symmetry, some slight difference, between matter and antimatter could be found the scientists who discovered would no doubt win the Nobel prize and a whole lot of other scientific prizes with it. It would probably become one of the most important scientific breakthroughs of the decade, if not the century. In previous posts here, here, here and here I begin by mentioning the matter-antimatter symmetry. The second and third of these posts are about producing more antimatter for study and the first and fourth are about looking for this elusive symmetry break.
In a world of evergrowing tension, international trust is at an all time low. With the recent Russian diplomat expulsions and resulting retaliatory expulsion of mostly US diplomats from Russia, there is a considerable political conflict brewing. This is particularity worrying as currently over 93% of the world’s military nuclear capacity is held between Russia and the United States. Russia currently has about 7000 nuclear missiles and the US has approximately 6800. The rest of the world’s cumulative might barely breaches 1000.
The south pole is a region of the world, which much like the Moon, has been internationally agreed upon to be neutral (sort of). No further territorial claims can be made to Antarctica since The Antarctic Treaty was ratified 1961 and all countries that had a claim at the time promised to act like they didn’t for all effective purposes. Ultimately the goal was to make Antarctica for peaceful, non nuclear, scientific research which has pretty much succeeded. One of the pinnacles of this research was the construction of the IceCube Neutrino Observatory which was completed in 2010. The IceCube is fed by over 5000 sensors which are distributed within a cubic kilometre of ice. When a neutrino interacts with the ice it will produce secondary particles which travel at speeds faster than light can travel through the ice. This of course produces Cherenkov radiation which the detectors can pick up.
It is of important scientific interest to try to create large quantities of matter and antimatter if we ever wish to detect some form of asymmetry between the two. If there is ever going to be a practical application of antimatter we would also require significantly more antimatter than we currently produce to exploit this application. Now pair production is the process of producing matter and antimatter pairs from energy, most often electron and positron pairs from photons far into the X-ray and gamma part of the spectrum. One of the methods with high potential for pair production is the Breit-Wheeler method in which a high energy photon is induced to decay into two particles in a strong electromagnetic background field.
Laser pulses on the femtosecond timescale and with many terawatts of power have allowed the scientific community to examine all manner of extreme physical effects. It is the production of these lasers which has brought about the very recent field of experimental astrophysics, something that would have been scoffed at fifty years ago. Many of the different laser applications from medical physics to nuclear physics can be summed up as transferring a large amount of energy from electromagnetic waves to particles. These laser matter interactions are by no means simple, but are certainly a fundamental part of physics especially if we want to properly apply the technology these lasers are providing.
A scintillator is a material which luminesces when impacted by ionising radiation. This occurs through the expected process of excitation and then relaxing of atoms which in this case produces visible photons. Scintillator plates are often connected to charge coupled devices (CCDs) in order to be able to get visual imaging of radiation in real time. There are many occasions when having this information would be useful. The kind of particle and its location in the image will reveal the distribution of isotopes in a sample; it can help detect possibly dangerous leaks in the machines of a nuclear facility; and there will always be applications for these things found in research conditions.