IceCube Neutrino Telescope

AMANDA writes: "Ice Cube is a neutrino telescope located at the south pole. It has just received the congressional support for $15 million dollars from the NSF. It will be the largest scientific instrument in the world. It promises a view into the most energetic phenomena in the universe." The idea is to use a cubic kilometer of Antarctic ice as a detector. Impressive.

Comments

Seismic stability?

[seletz]

I wonder how the keep the ice from wandering/changing.

As in glaciers, I suppose that antarctic ice is constantly changing (or at last i think so). And 1Km^3 of ice is quite a big mass.

Just my $.02 tough...

Re:Seismic stability?

[trilucid]

Hmm... very good question indeed. This page shows the major tectonic plates involved.

It seems to me that they've got a fairly wide berth in area (given the relatively small size of the selected region for usage) for the purposes of the project. Apparently, the vast majority of Antarctica is comprised on a single major plate.

To the best of my knowledge (albeit limited), the greater portion of this region is relatively seismically stable as a result. Of course, they'd want to stay away from "boundary regions".

That's about all I've got. Anyone got more firm data on this?

Re:Seismic stability?

[seletz]

Well, ok. Basically this means that the whole area is quite stable (because of not being located near any tectonic folds/bounds).

Ok, now what about the ever changing nature of ice itself? I mean, this ice built up due to snow falling on the surface and then beeing compressed slowly to ice. In this month's german edition of Scientific American there's an article 'bout that somewhere here.

Ice keeps on "flowing" like some liquid, but only slower (way slower). What about the tension built up because of that? Ice is brittle, don't constantly keep cracks and canyons build up?

Re:Seismic stability?

[trilucid]

seletz, upon further research into your point, I happened across this document on the UCSC site. It discusses the "slippage" behavior of the West Antarctic ice sheet in particular. I'm not certain what region specifically the proposed neutrino study site lies in (hopefully the Eastern sheet???), but this definitely lends weight to your inquiry into the changing nature of the ice.

Here's an excerpt concerning this region:

"The ice streams can be seen in satellite images as large features within the ice sheet about 500 kilometers (300 miles) long and 20 to 100 kilometers (10 to 60 miles) wide. They move at a rate of 1 to 2 meters per day, sliding over a bed of sediment saturated with liquid water. But if the bed becomes cold enough for the water in it to start freezing, the loss of lubrication causes the ice stream to slow and eventually stop moving, Tulaczyk said."

Now, that is definitely some significant movement in the ice sheet. One can only presume that the researchers on this project have very carefully chosen the coordinates for the "telescope" placement to avoid this kind of nasty possibility. However, even the general settling and compacting of ice layers will inevitably produce some movement, even in an area limited to 1^3K.

As per my earlier reply, I guess that close monitoring of and allowances for such shifts have been incorporated into the project design specifications. At least, for $15M USD I'd certainly hope so! :).

It remains to be seen, however, if our species can manage to mess up the climate in the chosen region enough over 10 years to irreparably skew the results...

Re:Seismic stability?

[darkonc]

They move at a rate of 1 to 2 meters per day, sliding over a bed of sediment saturated with liquid water. But if the bed becomes cold enough for the water in it to start freezing, the loss of lubrication causes the ice stream to slow and eventually stop moving, Tulaczyk said.

That 1Metre/day is the movement of the whole ice chunk over lubricated ground. That sort of movement is not likely to affect the detector that much... More important is the warping of the ice block against itself which is more likely to be in the range of inches or feet /year (as an analogy: I may be walking at 5MPH, but my backbone is relatively stable relative to itself [unless I get hit by a car going 60MPH, in which case, all bets are off])

As noted at one Nasa glacial site,

Ice streams-large river-like currents of ice flowing through the ice sheets at speeds one to two orders of magnitude faster than the general ice flow-greatly increase the potential swiftness of ice-sheet collapse by rapidly transporting ice from the interior of the ice sheet to the margin.

Glacial movements on the Antarctic shelf can vary in the range of orders of magnitude. In other words, the movement at the place chosen for the dector are probably unlikely to be moving at the 1M/day rate.. Given that the detector is apparently at the south pole, my expectation is that that section of ice sheet is going to be relatively stable.

Re:Seismic stability?

[henrym]

Let me give you a first person perspective on the ice movement at the pole. I'm currently the Network Engineer for the US South Pole station for the next 12 months. The ice sheet that the entire station is on is slowing moving towards grid NW at about 10 meters per year which works out to about 1 inch per day. In fact every year on Jan 1st, we hold a ceremony where the correct location of the pole is calculated, and we place a new marker. Looking out from the current pole you can see a line of markers from previous years which track the movment of the station nicely. The thing is that the entire sheet is moving at the same pace, so we're remarkably stable from a seismic point of view.

The IceCube array is one of the more exciting projects we're looking at, but the logistics to support it are enormous. It won't happen for a few years yet, untill the new station has finished construction. Check out www.polar.org for more details.

It isn't "extraordinarily transparent" to me...

[tonyc.com]

They say there are going to be about 5000 detectors spaced throughout the cube; that's a spacing of about 55-60 meters between them. Is the "extraordinarily transparent Antarctic ice" so clear that the detectors can pick up Cherenkov light through that much of it, or is that distance sufficient to visually isolate each detector completely from its neighbors? I guess my question is, how much of the cube is really being used in the detector, and how much is just optical insulation?

After a bit more reading...

[tonyc.com]

...I found this line in the original proposal: "These constraints lead to a strawman design consisting of 81 strings 125 m apart, arranged on a square 9×9 grid. Each string holds 60 optical modules separated by 16 m."

There are good graphics showing how they'll be arranged, and explanation of how this design will facilitate ~1 resolution in muon trail reconstructions. Impressive!

I also found elsewhere that faint Cherenkov radiation can travel more than 24 meters through deep Antarctic ice before being completely attenuated. So that question is answered.

Pressure

[KM1]

The thing that helps out here is the wieght of the ice above the detector. The pressure from the ice above the ice in the detector changes the normally opaque ice into a very clear form of ice. The small gaspockets that make ice opaque is forced into the ice crystal structure making it even clearer. Thanks to this you can have a sight of well above 20 meters. There is already one neutrione detector using the antarctic ice, the European/American collaboration AMANDA. http://amanda.berkeley.edu/amanda/amanda.html

Re:Useless fact [offtopic?]

[BadDoggie]

"Average" adult: ~180cm high, 50cm wide, 25cm deep = 225,000cm^3. Reduce by a fudge factor of around 20% due to empty space = 180,000cm^3.
1m^3 = 1,000,000cm^3, so 1Mcm^3/180Kcm^3 can fit about 5.5 people (only 4.4 without the fudging).

We bring in the trash compactor method of squeezing people down, knock off another 10% and we get 5 people per cubic meter. One km^3 is 1,000,000,000m^3, so you get about 5 billion people mashed into a cubic kilometer. That "factoid" may have been correct when it was first stated, but the planet's WAY past the 5 billion population mark. Check out the World POPClock Projection from the U.S. Bureau of the Census.

The thing is, while it's not too difficult to corectly imagine square kilometers (humans are good with area), we pretty much suck once volume's involved. According to some architects I know (and some others in a documentary on skyscrapers), we do have the technology to build something a kilometer high, but we ain't even close to it yet, for a lot of reasons.

The tallest we've gone so far: Shanghai World Financial Center, which isn't done yet (expected completion: 2004), and the Petronas Twin Towers in Kuala Lumpur (Malaysia), which, at 1483 ft (452m), is only 10m higher than the Sears Tower in Chicago. And still not even half a kilometer high.

And there's not many buildings that have a square kilometer footprint, which would cover more than 12 streets and 6 avenues in Manhattan. That's a lot of space. Or ice.

The real reason we're so interested in this is probably because penguins live in Antarctica, which happens to be where most of the TuxRacer location shots were filmed.

woof.

There's no need to mod this as off-topic -- it's a tangent, but not unrelated. I also didn't take the +1. Save your mod points to knock off the flames, trolls, ASCII art and racist/nationalist crap which is sure to fill this story.

Ice is cool but...

[rakerman]

So is SNO

Re:Ice is cool but...

[FTL]

> So is SNO

Moderators, that was most certainly *not* offtopic.

I would be very much interested in a comparison between the Ice Cube and SNO. My guess is that the Ice Cube is a lot cheaper, but that the SNO is a lot more accurate.

Re:Ice is cool but...

[ErfC]

I think Ice Cube can measure neutrinos with much higher energy than SNO can. I'm having a hard time finding SNO's energy range on their site, so someone in the know should please correct me, but it seems IceCube can measure well into the 100 TeV range -- that's about a thousand to a million times higher than SNO measures (I think SNO only gets up into the GeV's, but again I"m not sure; this is coming from my poor memory of some of the neutrino talks I've been to).

At this energy, IceCube is then sensitive to all three types of neutrinos (e, mu, and tau); SNO can only see the first two, because the tau lepton (that the neutrino has to turn into to be detected) is so huge it's way outside SNO's energy range.

I know that SNO has about 9600 phototubes, and IceCube has about 5000, so SNO might be a bit more accurate for this reason.

Besides that, IceCube is huge. SNO is a sphere 12 metres across, or just under 2000 cubic metres. IceCube is a cubic kilometer, or 1000000 cubic metres. So it'll see a whole lot more neutrinos! (This may be related to why IceCube has a higher energy range.)

Another Neutrino Telescope (in Canada)

[pomakis]

The Sudbury Neutrino Observatory near Sudbury, Ontario, Canada is another interesting neutrino telescope. It's not nearly as large as the Ice Cube, but it's still very impressive. From their web page:

The Sudbury Neutrino Observatory ( SNO) is taking data that has provided revolutionary insight into the properties of neutrinos and the core of the sun. The detector, shown in the artist's conception below, was built 6800 feet under ground, in INCO's Creighton mine near Sudbury, Ontario. SNO is a heavy-water Cherenkov detector that is designed to detect neutrinos produced by fusion reactions in the sun. It uses 1000 tonnes of heavy water, on loan from Atomic Energy of Canada Limited (AECL), contained in a 12 meter diameter acrylic vessel. Neutrinos react with the heavy water (D2O) to produce flashes of light called Cherenkov radiation. This light is then detected by an array of 9600 photomultiplier tubes mounted on a geodesic support structure surrounding the heavy water vessel. The detector is immersed in light (normal) water within a 30 meter barrel-shaped cavity (the size of a 10 story building!) excavated from Norite rock. Located in the deepest part of the mine, the overburden of rock shields the detector from cosmic rays. The detector laboratory is extremely clean to reduce background signals from radioactive elements present in the mine dust which would otherwise hide the very weak signal from neutrinos.

Rappers Contributions to Physics Recognized!

[Nova Express]

It's good to see that Ice Cube's decision to turn himself into a neutrino detector is finally bringing recognition to the vital role rappers have played in cutting edge astrophysics over the last few years. But where are the equally important mentions of:

Ice T's decision to turn himself into phased sub-boson colission chamber?

Snoop Doggy Dog's work as a superstring detector?

The Beastie Boys' turning themselves into a distributed gamma ray burster radio observatory?

The Notorious BIG's role as a high energy muon accelerator that ultimately resulted in his untimely death?

And needless to say, what Slashdot reader could be ignorant of the tremendous theoretical work that MC Hawking has done?

It's high time these rapper/physicist's contributions to society were recognized!