When plasmas are compressed multi-kilojoule lasers, some of the largest in the world, it is normally possible to get some nuclear fusion occurring. The neutrons produced in this fusion are normally produced in yields of about 105 neutrons per joule. When fusion is specifically sought for some incredible events have been produced. By blasting lasers into a compressible fuel pellet of deuterium and tritium an implosion was produced at the National Ignition Facility (NIF) in California which produced 7.6 × 1015 neutrons while only using 1.9 × 106 joule laser pulses. This is about 109 neutrons per joule. This event actually holds the record for the highest neutron number to joule ratio of any system in the world.
It is the traditional super villain plan to try to blow something up with a laser, whether that be the moon, the hero or a bank wall, lasers as tools of destruction are often seen in our media. The fact is, scientists are people too. Ever since lasers were first invented experiments have been performed to see if lasers can be used to effectively destroy things. Perhaps I’m not giving enough credit, understanding the laser breakdown threshold really creating and using lasers must safer. Also techniques such as laser induced breakdown spectroscopy involve the laser to atomise a sample for the spectrographic technique and laser machining can use the controlled ablation of a material to shape it.
Satellites certainty live an interesting life whizzing around the Earth; getting half frozen and half baked every orbit; trying to dodge all the other useless junk flying around as well; occasionally getting an order to rotate an arcsecond clockwise or something like that. They also get to be our first level of sensing when it comes to intense radio waves heading for Earth. Continue reading Studying Solar Radio Burst By Magnetic Reconnection
I consider it a slight shame that the layers of the Sun are not as widely known as the layers of the Earth. Most people could list the inner core, outer core, mantle and crust; but very few know that the layers of the Sun go: core, radiative zone, convection zone, photosphere, chromosphere and corona. The solar surface is defined as the boundary between the convection zone and photosphere so perhaps it is best to imagine the layers above his as the thin “atmosphere” of the Sun being only a few thousand miles thick (as opposed to radius to the solar surface which is about 400,000 miles).
Flux tubes are an interesting aspect of astrophysics. Flux or more accurately magnetic flux is the amount of magnetic field line flowing through a given 2D surface. A flux tube is therefore infinitely many circular 2D surfaces stuck together to create a long tube which magnetic field lines are imagined to flow through without ever exiting the sides of the tube. As magnetic field lines near the surface of the tube are always perpendicular to the surface they keep moving through and the total magnetic flux within the tube must stay constant even if the tube bends or grows and shrinks in diameter. Flux tubes and a slightly more advanced example that we’ll get onto in a second are found most prominently in the Sun. When large flux tubes are projecting out of the surface of the Sun then large amounts of magnetic field also flow out at this point, stymieing convection and producing a sunspot.
Despite having been writing these posts for almost two years I cannot remember explicitly mentioning terahertz spectroscopy once. There have been times when I have talked about analysis at the near infrared scale and of course referred to the terahertz frequency range but the exact details of terahertz spectroscopy have not been described in a way I’m satisfied with. Time to remedy that. Terahertz spectroscopy is a spectroscopic technique that uses photons in the area of terahertz (1012 Hz) to interact with the matter being studied.
Nuclear weapon testing has been both a good and a bad thing for the study of radioactive dating. On one hand the nuclear material released into the atmosphere has made it more difficult to accurately determine ages as the released radioactive material alters the naturally present concentrations in the atmosphere. On the other hand it can actually be beneficial in cases such as limnology. If some freshwater is found checking the radioisotopes present will reveal whether it has been recycled during the nuclear age. Another good example is to use the great increase in unnatural radioisotopes produced during a nuclear detonation, caesium-137 for instance, to calibrate other dating techniques. Since we know the exact dates of these explosions we can find the soil layer containing large amounts of caesium and check other dates compare to it.