Reaching out to stars beyond the Milky Way

Posted By : Enaie Azambuja
Reaching out to stars beyond the Milky Way

An international team of researchers in Japan is getting ready to power up a 50,000-ton neutrino detector by adding a single metal, which will turn it into the world's first detector capable of analysing exploding stars beyond the immediate neighbourhood of the Milky Way. Neutrinos are so tiny and interact so weakly that every second, trillions of them manage to pass through human bodies without anyone noticing.

The problem is that all supernova neutrinos that have been detected to-date have come from the immediate vicinity of our galaxy. No one knows whether neutrinos from older galaxies far outside ours act the same way as neutrinos close to Earth, or whether there is a completely new class of tiny particles yet to be discovered.

Experimental physicist Mark Vagins, Kavli Institute for the Physics and Mathematics of the Universe, and Ohio State University theorist John Beacom wanted to see if it were possible to improve Japan's largest neutrino detector, Super-Kamiokande.

One of their ideas was to add the rare-earth metal gadolinium to the detector's water tank, taking advantage of the gadolinium nuclei's ability to capture neutrons. If a neutron released from a neutrino interaction were nearby, it would be absorbed by the gadolinium, which would release the extra energy by creating a flash of light: a signal that could be detected by the equipment.

But before any tests could be run, the two researchers needed to find out if their idea made scientific sense and predict what complications they might need to overcome.

First, water inside the detector would need to be transparent. Neutrinos interact with water, creating tiny flashes of light that are picked up by the photomultiplier tubes lining the walls of the tank. If gadolinium made the water murky, it would prevent the phototubes from detecting any light.

Second, the gadolinium needed to be uniformly spread within the tank so it could be close enough to a neutrino-water interaction to magnify its signal.

"These two criteria, uniformity and transparency, mean the gadolinium must be induced to dissolve," says Dr Vagins. "We've spent over ten years figuring out how to do it."

In July 2015, Dr Vagins announced at an international conference in Tokyo that he had developed the necessary technology and will now start plans to enrich Super-Kamiokande with gadolinium.

Gadolinium is a by-product of the extraction of other rare earth metals, some of which are used to produce the colours in flat-screen TVs. This makes gadolinium affordable so that Dr Vagins and his team will be able to purchase the 100 tons needed to help Super-Kamiokande detect neutrinos from distant supernovae.


You must be logged in to comment

Write a comment

No comments




More from Kavli Institute for the Physics and Mathematics of the Universe

Sign up to view our publications

Sign up

Sign up to view our downloads

Sign up

EVS32
19th May 2019
France EUREXPO LYON
Sensor+Test 2019
25th June 2019
Germany Nürnberg Messe
DSEI 2019
10th September 2019
United Kingdom EXCEL, London
European Microwave Week 2019
29th September 2019
France Porte De Versailles Paris
Engineering Design Show 2019
16th October 2019
United Kingdom Ricoh Arena, Coventry