Rare Earth Helps Observatory Detect Ancient Neutrinos

Japan's Super Kamioka observatory ushered with rare earth elements to help it sense ancient neutrinos. New Atlas reported that the Super-Kamiokande neutrino observatory has received a relatively simple upgrade that should allow it to look further back in time. A rare-earth element called gadolinium (Gd) has been added to the water in the huge underground facility, which will make it more sensitive to neutrinos from more distant and ancient supernovae.

As a fairly lightweight elementary particle, neutrinos rarely interact with conventional matter, so they can pass through most objects unhindered. Taking the human body as an example, about billions of neutrinos streaming through your body every second.

But occasionally, neutrinos will also hit electrons in atoms. Under the right circumstances, scientists have the opportunity to study these collisions. This is also one of the main reasons why observation stations such as Super-K are most suitable for being buried under rocks or ice to avoid other radiation. It is reported that Super-K, located 1 km below Mount Ikeno in Japan, where it’s been quietly waiting and detecting neutrinos since 1996.

The active instrument of the facility is a huge tank standing 40 meters tall, filled with some 50 million liters (13 million gallons) of ultra-pure water and with walls lined with 13,000 photomultiplier tubes.

When neutrinos enter the water tank and hit water molecules, they produce tiny flashes. The magnification through the photomultiplier tube helps the optical sensor to pick up relevant information.

It is worth mentioning that, these neutrinos have different "fingerprints" of flashes depending on their origin, which can include the Sun, supernova explosions, artificial experiments, nuclear reactors, or from the decay of protons.

Unfortunately, although supernovae are particularly fascinating, these events do not happen often. If the search range is extended to other galaxies (not limited to the Milky Way where we are), the number of neutrinos that can be picked up can be increased.

The difficulty in this matter is that the farther the signal is, the weaker it is, and it is even difficult to distinguish it from the background noise. The good news is that the rare earth element Gd added in this Super-K upgrade helps to significantly amplify those neutrino signals from distant supernovae.

So, the new upgrade is designed to help amplify neutrino signals from those distant supernovae. In July, the research team had added about 13 tons of Gd compounds to the test solution to reach a concentration of about 0.01%.

By interacting with some neutrinos to produce neutrons, gadolinium interacts with these particles to produce a gamma ray flash, which the optical sensors can easily spot. More importantly, this will not negatively affect the monitoring of other neutrino events.

Project overseer Masayuki Nakahata said: "With a gadolinium concentration of 0.01 percent Super-Kamiokande should detect neutrons from neutrino collisions with 50 percent efficiency, We plan to increase the concentration in a few years to increase efficiency. I hope we can observe neutrinos from ancient supernovae within a few years."

The research team added that this upgrade ushered with rare earth could allow observatory Super-K to detect neutrinos from supernovae that occurred as far back as 10 billion years. This could teach us more about particle physics and the distant history of the universe.

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