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Fermilab | Batavia, IL | USA

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Sniffing out science with a blood-hound like detector

Editor’s note:
Bob’s most excellent particle adventure, part 3

Bob Peterson continues to travel with his QuarkNet particle detector around the edge of Africa recording remnants of cosmic rays. This offers a chance to study how cosmic ray recordings differ on land and sea and at different latitudes. The data will be accessible to high school students and teachers in several countries who use similar detectors to learn about particle physics.

His first post explains why he’s taking his science to the seas and how getting a detector on a boat sounds easier than it is.  In Bob’s second post the boat gets going and so does the detector.

26 April 2011
R/V Polarstern
Lat: 13-40.8 S
Long: 0-8.6 W
Ship velocity 11.0 knots
Ship course 322.7 ° T

After six days out, we just crossed back to the Western Hemisphere. I wondered what that bump was. Home still feels a long way away. The first days of the heavy swell have passed and everyone, including myself, is resting easier. The voyage has started to focus on the science to be done.

However, every onboard science group is experiencing problems with data collection including myself and the QuarkNet cosmic ray muon detector. After a successful plateauing while in Cape Town, South Africa, now one data channel is acting up with changeable counts of cosmic ray remnants interacting with the detector. The rate on that one channel will rise and fall unexpectedly and I cannot find a cause. It’s happened over the past two nights. If it happens again, I will switch the power cables and see if I can isolate the cause.

It occurred to me that anything done on a ship complicates procedures. Ship environments do not make data collection easy. There is constant motion from swell and wind, and this slows just putting hardware together. Tools are not close at hand, and if ship personnel get involved, then the chain of command comes into play. And to search for anything means climbing flights of stairs. My legs are getting stronger, but the stairs are so steep that I tread carefully. Ship personnel go up and especially down like cats.

One group from the Leibniz Institute of Tropospheric Research has two large containers bolted to the top deck over the bridge. This deck is 85 feet above the water. Extending out the forward side of one container is an intake pipe that is “sniffing” the air in the lower atmosphere for particles. Not high-energy particles, rather things such as soot and sea salt and organic compounds. They need to avoid any ship-generated contaminates as they are trying to correlate the low-level atmospheric particles with the upper atmosphere. The upper atmosphere is measured using a Light Detection and Ranging, or LIDAR, laser system from the second container. So, at night you can see a rich green laser projecting vertically over the ship. Well, we are sailing in the southeast trade winds and our heading is due northwest so the relative wind over the deck is from the stern. Unfortunately, they are “sniffing” the engine exhaust coming out of the stack, and they can even tell when the galley starts cooking. Their sampling is so accurate that they can tell what is for dinner. I can tell what’s for dinner by reading the menu.


Plateauing a detector: This means that the detector has hit the sweet spot where the photo multiplier tubes are recording the optimal amount of photons. Below that spot we would be missing valuable data and above it the data would get muddy.

*Stern: The rearmost part of a ship or boat.

*Trade winds: A wind blowing steadily toward the equator from the northeast in the Northern Hemisphere or the southeast in the Southern Hemisphere, especially at sea. Two belts of trade winds encircle the Earth, blowing from the tropical high-pressure belts to the low-pressure zone at the equator.

*Stack: A chimney or a vertical exhaust pipe.

— Bob Peterson


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