Physicists at Massachusetts Institute of Technology (MIT) have successfully developed a table-top particle detector that is able to identify single electrons in radioactive gas. The device will enable scientists to actually “see” individual electrons. This may bring the scientific community a step closer to finally measuring the mass of a neutrino.
The research was funded in part by the Department of Energy and the National Science Foundation. Researchers from the Pacific Northwest National Laboratory, the University of Washington, the University of California at Santa Barbara (UCSB), and elsewhere collaborated with the MIT team to record the activity of more than 100,000 individual electrons in krypton gas.
The detector – named “Project 8” – uses a magnet to trap electrons given off when a radioactive gas decays. The weak signals emitted by those electrons are then picked up through a radio antenna. These signals can be used to map the electrons’ precise activity over several milliseconds.
“We can literally image the frequency of the electron, and we see this electron suddenly pop into our radio antenna,” says Joe Formaggio, an associate professor of physics at MIT. “Over time, the frequency changes, and actually chirps up. So these electrons are chirping in radio waves.”
Formaggio seemed to be talking about a physical phenomenon called cyclotron radiation, in which charged particles like electrons emit radio waves in a magnetic field. Electrons emit this radiation at a frequency similar to that of military radio communications.
In addition to imaging the frequency of electrons, the detector may prove an important development in measuring the mass of a neutrino.
The mysterious neutrinos are sub-atomic particle so miniscule that F. Reines described them as, “the most tiny quantity of reality ever imagined by a human being.” Several estimates have been put forward regarding neutrino mass. However, researchers have yet to precisely measure it.
“We have [the mass] cornered, but haven’t measured it yet,” said Formaggio. “The name of the game is to measure the energy of an electron — that’s your signature that tells you about the neutrino.”
Scientists have previously conducted experiments to spot the energy of electrons using a massive spectrometer. One such example was KATRIN (Karlsruhe Tritium Neutrino Experiment), conducted in Germany. There were two downsides however: KATRIN was much bigger than the MIT detector, and it also destroyed the electrons as it tried to measure them.
“In KATRIN, the electrons are detected in a silicon detector, which means the electrons smash into the crystal, and a lot of random things happen, essentially destroying the electrons,” said Daniel Furse, a graduate student in physics and a co-author on the paper. “We still want to measure the energy of electrons, but we do it in a non-destructive way.”
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