Photon spectrum of free neutron decay revealed for the first time
National Institute of Standards and Technology (NIST) research reveals the photon spectrum of free neutron decay for the first time
Story
"The team measured two aspects of neutron decay: the energy spectrum of the photons, and also its branching ratio, which can provide information on how frequently the decays were accompanied by photons above a specific energy. The results of this effort gave them a branching ratio measurement more than twice as accurate as the previous value, *and the first measurement of the energy spectrum.* "
Published 14 June 2016 © 2016 American Physical Society
This is interesting as we observed thermal neutrons in *GlowStick* 5.3 and others have reported them too.
The key graph in the paper "Energy spectrum deposited by photons from radiative neutron decay." is worth taking a look at - imagine what this would look like on a Log Lin basis - would it look a little like "signal"?
Main Process
Read about "Free neutron decay" in wiki
"About one in 1000 of free neutrons decay with an additional emitted gamma ray thought of as due to a sort of "internal bremsstrahlung" that arises as the emitted beta particle interacts with the charge of the proton in an electromagnetic way"
From a summary
"Based on 22 million electron-proton events, the researchers report an average branching ratio of 3.35×10−3 for product photons with energies between 14.1 and 782 keV"
"A second detector array of large area avalanche photodiodes directly detected photons from 0.4 to 14 keV"
Could this in part explain the "signal" in GS 5.2?
Tip-off: Ged
Comments
"I have made a quick read of the paper. It is unlikely that this is the cause for our signal. Let us consider a couple of reasons why I say this.
Neutrons could come from spallation of the Li from the high energy protons that Piantelli says comes from the Ni-H reaction. Let's look at the cases of fast, thermal, and cold neutrons.
Neutrons have a long half life of 880s or about 15 minutes. This is mentioned in the paper. They specifically mentioned use of cold neutrons in their experiment (velocity less than 1E3 m/s) in a vacuum.
First, it is likely that the Li spallation would create relatively fast neutrons in the 100keV to 1MeV range. Such neutrons would likely exit the reactor. Fast neutrons in this range have a velocity of >1E6 m/s and would statistically be 8.8E8 meters away for the mean time to decay - twice the distance to the moon.
If, for some reason, the reaction created abundant thermal neutrons in the 1eV range, such neutrons have a velocity of about 1E4 m/s; so the mean distance for neutron decay is 8.8E6 meters, or about the diameter of the Earth away.
Now, what about cold and ultra-cold neutrons? First, they would be unlikely to be created by spallation. But, if they were created in large numbers, long before they decayed, they would be captured by the nuclei of the metals of the reactor because at such low velocities the capture cross-section for a neutron is very high. In such a circumstance, it is not clear what the emission would be (would depend on the metal), but it would not be the neutron decay spectrum that would be observed."
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