Physicists at the Massachusetts Institute of Technology report they've developed a small, tabletop particle detector capable of identifying a single electron emitted from a cloud of radioactive gas.
The detector utilizes magnets to trap electrons given off by decay of the radioactive gas, holding them inside a magnetic bottle.
While in the bottle, the electrons give off extremely weak signals that allows their activity to be tracked over several milliseconds, the scientists say in a report on their work in Physical Review Letters.
That activity showed a characteristic pattern, they said; when emitted by the gas, the electrons vibrate at a particular baseline frequency that, before it peters out, can spike whenever the electron collides with an atom of the radioactive gas.
An electron colliding with multiple atoms in the detector will display frequency jumps showing a step-like pattern, explains MIT physics Professor Joe Formaggio.
"We can literally image the frequency of the electron, and we see this electron suddenly pop into our radio antenna," he says. "Over time, the frequency changes, and actually chirps up. So these electrons are chirping in radio waves."
The work represents a significant step toward a long-sought but elusive goal of physics, he adds; determining the mass of a neutrino.
Neutrinos are elementary particles throughout the universe that have proved extremely hard to detect because they don't interact with standard matter, simply passing through it instead.
Although theories on what their mass might be have been put forward, that measurement has so far eluded researchers.
In their experiments, the MIT scientists, working with researchers at the University of Washington, the Pacific Northwest National Laboratory and the University of California, Santa Barbara, have tracked and recorded the activity of more than 100,000 individual electrons emitted by decaying krypton gas.
"We have [the mass] cornered, but haven't measured it yet," Formaggio says. "The name of the game is to measure the energy of an electron — that's your signature that tells you about the neutrino."
Their success has encouraged them to begin experiments with tritium gas, ideal for gathering measurements because it decays at a rate that allows relatively easy observations of its electron byproducts.
As a radioactive atom in tritium gas decays, Formaggio explains, it morphs into an isotope of helium while releasing an electron, along with a neutrino.
Since the sum of the energies of those resultant particles matches the original amount of the energy of the neutron they come from, measuring the energy of the electron can yield information on the energy — and thus the mass — of its accompanying neutrino, he says.
