Sunday, December 26, 2010
Q & A from the 7th grade science classes (Menomonie, WI)
For most of these, I'm going to give what I think of as a scientist answer. That is, a short answer, and then an explanation or refinement of the answer. Hope this is useful for the classes! These are great questions, over a huge range of topics. Fun to sit and write the answers as well!
Do you think we could capture neutrinos and use them for a purpose (like for an energy source?)
We certainly don't know how to do anything like that at the moment. But it's an interesting possibility, and many great advances in science and technology were hard to predict ahead of time. Lasers went from being lab curiosities to present in every CD, DVD, blu-ray, and cat toy within thirty years. Nuclear power went from an abstract theory to a commercial source of electrical power in about twenty five years. So in our lifetimes, it's not impossible that we'd have neutrino energy or neutrino communications.
What type of information are you looking for from your data?
We're looking to detect these very high energy neutrinos. Lower energy ones from the Sun and from showers/cascades of particles in the atmosphere have been well-measured, but no one has observed neutrinos from astronomical sources. We believe that they must be there, and, in fact, not being able to see them would probably be more revolutionary than seeing them. Our data, in detail, is the time profile (think of a graph of signal intensity versus time) of a very fast pulse in radio waves at a wide range of frequencies. The times of interest are measured in billionths of a second (nanoseconds (cool bit of information, light travels about one foot in one nanosecond)), and the signals are a few times louder (voltage or power) than the random fluctuations that are always present. We'd want to see the signal in a number of different antennas to tell direction and energy of the neutrino that made the pulse.
How do you stay warm? (what do you wear?)
We're issued some pretty good parkas and cold weather gear. There are some pictures at duvernois.blogspot.com under Extreme Cold Weather (ECW, which is what the gear is called) equipment. Basically you need thermal underwear tops and bottoms, polypro sock liners plus wool socks, insulated pants and a fleece jacket, a balaclava and a hat over that, two layers of gloves, and then ski pants or ski overalls, heavy cold weather boots and a parka. Because it can be so bright, you also need ski goggles. When it gets below about -50F or so, folks working outside typically use chemical heat packs in their boots and gloves. Frost nip and frostbite are occupational hazards here. During the winter season, emergency work is sometimes done outside down below -100F but one can't be out there for too long.
Do you have running water to shower?
I'm living in the new elevated South Pole Station which is heated and does have running (hot and cold) water. All of the water though has to be melted from snow which takes a lot of energy, so there are strict water conservation rules. You're limited to two two-minute showers per week and one load of (cold wash) laundry per week. Out at the small camps and bases in Antarctica using snow for daily cleaning is normal, and the only hot water is from a small pot on a stove. Folks are relative grimy here overall.
Has anyone ever been injured while working on project icecube?
There have never been any serious injuries on IceCube, though there have been a few close calls. Those have mostly been with the heavy equipment and cranes operating overhead. IceCube has a fairly extensive (many hundreds of pages) safety manual and most of the work done here is, more or less, in accord with US style safety regulations. Minor injuries are relatively common, it is both extremely cold and dry which means that it's very easy to have bleeding cuts and scrapes that are typical with any mechanical work. Additionally there are the cases of frost nip, especially at the beginning of the summer season when it's still warming up. There are many tales, some of them even true, around the Antarctic program of terrible accidents at various times and places. There are wrecked aircraft on the ends of several of the runways down here.
How did they drill the holes? What do you do if your equipment breaks down?
Both the IceCube and ARA holes are drilled with hot water. Essentially there is a big tub of hot water, and a long pair of hose (one inlet and one outlet) and the necessary pumps and heaters. Hot water is pumped through the hose into the snow, and water is pumped back to be reheated. The hose is let out slowly and it sinks down into the ice. It takes about two days (working 24 hour per day) to drill down 1 1/2 miles in the ice. The resulting hole is about 14-18" in diameter (with this drill setup, you could make it wider by slowing down the advance of the hose or increasing the flow of water), filled with water, and 12" diameter modules are lowered into the hole. The warm water in that hole takes up to a week to refreeze solid at which point the electronics are there to stay.
The folks who built the drill are here at Pole operating it, so they can work on any problems with it. In general, there is a lot of ability floating around here, any bulldozer, snowmobile, washing machine, radio transmitter, or aircraft here in the field has to be able to be repaired in the field. Some problems might require parts to be shipped in or the use of spares rather than repairs.
How is the equipment powered?
The station heat and electricity comes from diesel. The vehicles on the ground here are powered with either diesel or gasoline. Electricity is generated where required with small electrical generators which are also either gas or diesel. McMurdo used to have a nuclear reactor, and they have some new wind turbines. At the South Pole there is huge interest, both environment (we burn a lot of fuel in the middle of a pretty pristine place) and logistics (all of that fuel is flown down to the Pole on airplanes with the exception of a small amount which arrives on a land traverse, picture a convoy of big tracked dozers pulling sleds with fuel bladders on them), in making more green power. The problems though are difficult (otherwise it would already have been done!), sunlight only 1/2 of the year plus clearing the snow off of the solar panels, it's windy in the summer, but often windless in the winter...
Do you need a certain certification to be part of project icecube? How were you chosen to be part of the research project?
The IceCube folks are basically of three backgrounds: science, these are almost all Ph.D. physicists (as experimentalists we work on the instruments as well as the science, so picture a lab of electronics and sensors rather than formulas on a blackboard); technical, we have a couple of project management folks and engineers, typically they have spent much or all of their careers working closely with scientists; and drillers, these are folks hired in to work on the drilling, they have a WIDE variety of backgrounds and when they aren't drilling for IceCube they might be on the north slope in Alaska, or on a rig in the north sea, or putting in deep wells in Saudi Arabia. There are always exceptions, especially in the whole Antarctic end of things. The gal who runs the communications facility at the South Pole Station was our camp manager many years ago in McMurdo on a balloon campaign. Folks with the US Antarctic Program jobs tend to keep showing up around the continent that they love.
Well, ARA is the successor instrument to another experiment called ANITA in which I played a role. When I got a job at the University of Wisconsin, physics department and IceCube Research Center, it was mostly for ARA and to bring some real radio detection capability to the group, Since then I've also become part of the IceCube experiment. In the sciences, other than applying for a specific job, most every research project would love to have someone come knocking at the door expressing interest in the project and a willingness to (initially at least, especially if you don't have a lot of background) volunteer.
How did they know where to drill the holes?
We have them laid out on a map, and then there's a survey team that comes around and marks the actual spot to be drilled with a wooden stake and a label. They have a number of surveyed spots around the station, and using a mix of GPS and traditional surveying tools (transit and level) are able to mark spots to a few inches. Afterwards, they come around and redo the work to measure the "as built" locations which could be a tiny bit different than the ideal locations. For the detectors we need to know where they are precisely, but they don't have to be in the exact locations we specified initially. For example, near the station, you might mark a location on the map, but later discover that a cable runs through there, so you move the location over a foot or two. But then later you measure that actual location to better precision.
The folks who do the surveying work in Antarctica are a really small community, as there are a lot of details which are dramatically different than surveying other places. Markers are buried by snow each year, and even simple things like "100 feet east" are pretty complicated when you're at the Pole and everything is north of you (sort of).
How many people are in your camp? How big is your camp area?
The South Pole population is updated every day or so on the main monitors in the galley. It's currently 240 people. About 125 people have berths (tiny rooms, 6x8') in the main station. The rest of the people live out in what is called summer camp, about 100 yards from the main station. They live in (somewhat) heated double wall long tents. Basically bunkhouses. There is a race around the Pole tomorrow (on Christmas morning) and that race goes all the way around all of the fuel dumps, the equipment storage, the cargo berms, and the ski taxiway. That is a total distance of 2.1 miles.
The IceCube experiment starts within a couple hundred yards of the station, and at the farthest is about 1/2 mile away. ARA is building another 1/2 mile behind the far edge of IceCube. Ultimately, we'd like to build something about 20 miles on a side, covering 400 or so square miles.
Have they ever found anything in the ice while drilling?
All of the IceCube drilling area was checked over with ground-penetrating radar before drilling began. The ice that the South Pole station (and previous stations) is built on is moving, and old station material, buried by lots of compressed snow were found with the radar ahead of construction. There are whole buried buildings, pallets of cargo, and who knows what else from the past sixty years of stations out there. During the drilling, there weren't any report of really hitting something, although if the hole intersected with some small item, say a screwdriver dropped in the snow by Byrd's parties in 1958, it wouldn't have been noticed, and ultimately would have ended up at the very bottom (sinking down through the water) of the hole. ARA is being built well outside of where people have ever had camps, so there's no expectation of finding anything!
Near McMurdo, there are some dry valleys (called the Dry Valleys of Antarctica) which have no snow cover. It's blown out of them by the wind. These areas have abundant fossils, and there are hints that there is probably oil down there in the rocks. At the South Pole, the rock is over 1 1/2 miles down.
What are neutrinos made of?
Neutrinos are fundamental particles, which means they aren't made up of anything else. No sub-pieces to them. The so-called Standard Model of Particle Physics has three generations of particles: the lowest generation is the one we're somewhat familiar with, the electron and its antiparticle, the positron, and then the electron-neutrino and the electron-anti-neutrino. The neutrino was originally postulated as having to exist (as a nearly invisible particle) to carry off energy and momentum in observed particle collisions. Imagine the following, you throw a tennis ball to a friend of yours, she catches the ball, but goes flying backwards. Something other than that tennis ball was involved. Okay, now change those to subatomic particles, and the "something else" is the neutrino. In modern times, neutrino detectors have had great success, but fundamentally the neutrino doesn't interact very much, so detectors have to be large. Here at the South Pole we're sitting on the world's largest piece of clear (in light AND radio) material which is why it's a good place to put a detector system.
At what concentration levels are neutrinos found in the ice/air?
The neutrinos that we're measuring are passing through. They're traveling at very close to the speed of light as they pass through the ice (or the air). In fact, in a material, the speed of light is lower than it is in no material (in vacuum) and these particles are traveling faster than light in the material. The emission made by such objects is called Cherenkov light (after the Russian who explained the phenomena, this is the blue glow in movies from inside reactors). That said, there are many millions of neutrinos passing through your body in the time it takes to read this sentence. Some of them come from the nuclear reactions in the heart of the Sun, some from cosmic ray particles hitting the atmosphere and making showers of secondary particles, some from each nuclear reactor on Earth, some from decaying natural radioactives in the Earth itself, and some (the few, but the ones we're interested in) from supernovae, active galaxies, colliding black holes, and other fun (which means here dramatic and violent) astronomical sources. An exact number here hides that they come from many directions, many sources, with a wide range of energies (more than a factor of 100000000000000 in energy between the lowest energy (nuclear decay or reactor) neutrinos and the highest energy capabilities of ARA and ANITA).
Thanks much and cheers,
Mike DuVernois, writing on Christmas Eve, at the South Pole (well, about 100 feet from the South Pole)
----- Original Message -----
From: Michael DuVernois
Subject: Re: science
Let me send along the following, layperson explanations of the two experiments.
ARA and IceCube are both looking for neutrinos from high-energy systems in the universe. Neutrinos are small, nearly massless subatomic particles that pass through material with only the rarest interactions. In fact, IceCube is most interested in neutrinos which have already gone through most of the Earth and happen to interact in the ice near the detector going upwards. IceCube looks for the light emission from the neutrino interactions in the ice. ARA looks for a coherent pulse (lasting on order of a billionth of a second, a nanosecond) of radio emission. We use the ice because it is both light transparent and radio transparent. The remoteness of the site, the South Pole, reduces the anthropogenic backgrounds so the real physics signal stands out more clearly. In detail, the two experiments are optimized for different energy ranges: IceCube for lower energies, and signals associated with supernovae, and ARA for higher energies, and signals associated with the most energetic particles in the universe (the so-called GZK cosmic rays).
There is a lot more, at layperson, general scientifically trained audience, and technical levels on the IceCube website. There are a couple of less technical explanations of the ANITA experiment which is a balloon-borne experiment which is the intellectual godmother of ARA: for example, http://www.phys.hawaii.edu/~anita/web/science.html
On Nov 17, 2010, at 8:31 PM, Michael DuVernois wrote:
Some additional information...
I am going to Antarctica to work on different projects, the Askaryan Radio Array (ARA) in which I have a large role, but it's a small startup project, and IceCube for which I am a small part of a large project.
(Not much there, more as the detector gets built.)
Currently it's not South Pole specific, but will be once I head out. My flight out of the US is on December 15th, will be at Pole on December 21st, and will leave the ice around January 14th.
IceCube blogs from Pole:
There are several websites that have material about Antarctica.
The Polartrec website has classroom resources as well as other information.
Here is a link to videos that we produced with the Madison School District. Each video is one minute long
There are only three different videos. Some are in different sizes or formats.
The University of Delaware has a nice site too.
Instrumentation Manager & Scientist
IceCube Research Center & Antarctic Astrophysics Center
222 West Washington Avenue, Suite 500
Madison, WI 53703 USA
at 1:21 PM