Sudbury Neutrino Observatory

The Sudbury Neutrino Observatory (SNO)

What is the SNO?

The Sudbury Neutrino Observatory is an underground laboratory that began operating in 1999 to study and detect solar neutrinos which are particles that do not have an electric charge and nearly no mass. These invisible particles are produced in the suns core as byproduct of nuclear fusion and pass through the earth nearly at the speed of light. Due to the lack of mass and electric charge, they are extremely difficult to study which is why the Sudbury Neutrino Observatory was built for. The purpose of the SNO is to help scientists and astronomers understand the processes that take place in the sun.  It is operated by around 130 Canadian, American and British scientists.

 Development began in 1990 and was completed in 1998. It cost a total of $73,000,000 and was supported and funded by the Natural Sciences and Engineering Research Council of Canada, the Northern Ontario Heritage Foundation, United States Department of Energy, Ontario Power Generation and several more.

In the image above, you can see what the detector looks like along with the 9000 light sensors. Below is a diagram that displays the structures design and depth

Construction:

The Sudbury Netrino Observatory was built 2km underneath a mine in Sudbury called Creighton Nickel Mine. The detector is made up of a large acrylic ball that spans 12 m in diameter. The sphere hangs with the support of 10 ropes made of synthetic fiber. There are over 9000 photo multiplier tubes (or light sensors) right along the outside of the sphere that faces towards it. To detect the presence of neutrinos, these sensors observe how the neutrinos react with the water. When neutrinos interact with heavy water, it creates Cherenkov radiation, in other words, flashes of light emitted from the tank due to the interaction between neutrino and heavy water.

 There were many precautions taken in order to prevent unwanted signals from other sources and elements. The main one is the depth of the detector. SNO was built deep underground to shield the detector from noise of cosmic rays. Another is that the lab is kept extremely clean to prevent signals from the dust of the mine from interfering with the sensors.

This image shows just how deep the SNO is built.

Contribution:

The SNO has accomplished a lot in the field of neutrinos and has made important discoveries about their production along with information about the core of the sun. According to Astro-Canada, in the early 80s, “it was realized that the number of solar neutrinos detected by various laboratories were less than predicted by theoretical calculations”. This caused a debate about the suns production of neutrinos. Scientists could not confirm whether we simply did not understand our sun properly or if these neutrinos were changing form as they reached earth causing the amount to lower. The SNO discovered that neutrinos have some mass and can change form when they pass through the earth.

Although its primary goal has already been met, scientists continue using its data in order to learn as much about neutrinos as possible.

 Today, the Sudbury Neutrino Observatory has been expanded and is being operated under a new name, SNOLAB. The new observatory perform the same experiments and studies as SNO, however the laboratory has been expanded. A Queens University press release states that the lab will be “expanded by nearly 150% “,

http://astro-canada.ca/_en/a2115.php

http://physics.carleton.ca/sno/about-sno-project/sno-neutrino-detector

http://www.sno.phy.queensu.ca/sno/press_release/SNOBackgrounderNov15f.pdf