Today, because there were so many visitors, the cage traveled half speed so it took quite a bit longer to get two kilometers underground. To be honest, I liked it better on Monday when we went full speed!! We are planning on staying underground until 4:00pm today. Right now, that seems like it is going to be a long day. (in the end -- it didn't feel like a long day at all!! I think I finally know what I want to be when I grow up -- a SNOLAB Scientist!)
Once we get to SNOLAB itself, we have to wash off our boots and get ready for the next step.
Of course, we had to shower, wash and dress in special clean clothing again. See that I'm holding a notebook -- I'm trying to learn and write down everything I can. The picture below is from the ultra-pure water generation system. The big cylinders to the right are charcoal filters, but the water will go through several steps such as reverse osmosis and deionization before it is clean enough for use with the experiments at SNOLab.
The new SNO+ project is using the same infrastructure from the original SNO experiment. Please click here to go to the virtual tour page and click on 20, 21 and 22 to view the SNO sphere. It has 9600 Photo-multiplier tubes (PMTs) on the outside of the acrylic vessel (AV) which is on the inside. You can see the AV when you click on 20 of the virtual tour.
We had an amazing tour of the scintillator -- which is the purification system for linear alkyl benzene -- or LAB for short. lAB is a dish soap type substance. This is what they are going to fill the AV with during the SNO+ experiment. Previously, the scintillator system was tested with ultra-pure water to make sure everything worked and that there were no leaks, and now they are beginning to push LAB through the system to clean out the water and become more and more confident that the system is safe and will work for its intended purpose. It will take three months or so to flush out all the water.
The big blue tanks are there to hold the LAB prior to purification. As you can see, the AV of SNO+ will hold a huge volume!!
Here is part of the LAB purifier. Notice all the wiring at the top of the picture. Every aspect of every valve, flange and container has to be monitored electronically. The pipes were connected using and expensive, clean and precise type of welding called orbital welding.
Here is the screen of the computer monitoring system. You can see how complex and multi-step the system is. The operators of this part of SNO+ are engineers.
One thing to know about LAB is that it is extremely combustible! And... remember.. we are 6800 feet under the ground!! As you can imagine, safety is a huge consideration.
There are special smoke alarms that actually suck in the air and don't have to wait for the smoke to come to them. It is a very early detection system called VESDA.
There are also many many other fire suppression systems in place all over the underground laboratory.
Next, we went over to the Germanium detectors, which are used to count the radiation of samples of materials used in the experiments. It is very important that all materials used - including the ultra-pure water - have extremely low radiation levels! If they didn't -- it would mess up the data used to detect Neutrinos and Dark Matter. Everything in lab, including the containers and the paint on the walls, needs to have super super low radioactivity.
In the above circular counter the outside very thick ring is made of lead (but covered with copper) and the inner, brighter circle is pure, clean copper. This is all designed to keep out background radiation such as radon and muons. This is also why we are so far down underground -- it shields against cosmic radiation and muons. It takes two to three weeks of counting the sample to get good data about how clean and non-radioactive it is.
The lead bricks in the last picture of a different type of germanium detector uses lead bricks that we down underground in the Windsor salt mines since the 1950s. This is good to use, because it hasn't been exposed to surface radiation for decades!!
On another note -- Ian, the operator of the counter, also said that we are still measuring the effects of the Fukashima reactor leak!! (Why isn't this on the news??!!)
Following this, I was able to job shadow Ana Sofia who is one of the operators of the SNO+ detector. It isn't up and running yet, but it is filled with ultra-pure water so that the detector can be calibrated. Ultimately, the AV of the detector will be filled with LAB and a couple of other substances which will make it's sensitivity to neutrinos exponentially greater than the original SNO experiment -- it will also detect the process of neutrino-less double beta decay which will answer two main physics questions: 1. Are neutrinos their own anti-particle? and 2. What is the actual mass of neutrino? We know they have mass, but what is it?
To collect the data -- there are 32 data acquisition boards with 512 channels --- and each channel is connected to one of the 9600 PMTs of the SNO+ detector.
That's a LOT of data!! The detector needs nano-second precision!!
Each day I understand more and more! So glad I had I had so many days in a row here!!
People we spoke to that day:
Paul Larochelle, Operations Engineer at SNOLAB (in the SNO+ Scintillator plant)
Dr. Ian Lawson, SNOLAB Research Scientist (in the low background counting area)
Ana Sofia Ignacio, MSc in Physics (the SNO+ detector operator)
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