The was Ray Davis’s experiment at the Homestake Gold Mine. The first neutrinos from the sun that scientists were able to see were the ones energetic enough to change a chlorine atom into an excited argon atom (by changing a neutron inside a nucleus to a proton). Researchers were able to see these only by building an extremely large scintillator detector and making sure there were no radioactive contaminants anywhere nearby. Scientists now know that most neutrinos from the sun are in the tens to hundreds of electronvolts. Neutrinos from the sun come in energies from tens to millions of electronvolts, a result of the many different fusion processes that take place there simultaneously. Credit: Super-Kamiokande Collaboration/Kamioka Observatory, ICRR, Univ. The bright yellow at the center means a high concentration of neutrinos from that direction. The trick, then, is building a detector that can measure tiny differences in electron energies. Another proposed method to see these neutrinos is using these low-energy neutrinos to stimulate a beta decay, then searching for an outgoing electron that has just a little more energy than one would expect. It turns out that materials at room temperature are vibrating with thermal energies that are much higher than these Big Bang neutrinos, so one way to see these lowest-energy neutrinos is to use stiller, colder materials (at cryogenic temperatures) and look for nuclei that receive a small amount of energy seemingly out of the blue. This is less energy than it takes to even knock an electron out of a hydrogen atom, making them incredibly hard to detect, because you need a detector with an even lower threshold. The lowest-energy neutrinos come from just a few seconds after the Big Bang, and it is expected that these neutrinos have only a fraction of an electronvolt of energy. Because neutrinos come in a very broad range of energies, an even broader range of techniques have to be used to see them.
0 Comments
Leave a Reply. |