Wednesday, May 23, 2012

South Dakota's LUX will join the dark matter wars

Many articles on this blog were dedicated to the war on the existence of dark matter.

Some research teams claim that they have already detected a proof of a dark matter particle, a WIMP, whose mass is of order 10 GeV. Other teams disagree equally vehemently.

The Homestake Mine

In the Fall, a new big player will enter this conflict; see a list of other participants. Its name is LUX: Large Underground Xenon detector. Phys.ORG just dedicated a fresh article to the experiment:
Lying in wait for WIMPs: Researchers seek to increase the sensitivity of Large Underground Xenon detector by orders of magnitude
But much of the data were already available to readers of the Symmetry Magazine in April 2012.

The project is located almost a mile beneath the surface, in The Homestake Mine, a gold mine that closed in 2002 and opened for science in 2007.

Cylindrical titanium thermos ("the can") will hold liquid xenon cooled to –108 degrees Celsius. In many respects, you could think that the experiment is similar to XENON100 in Gran Sasso, Italy which is a cornerstone of the "dark matter is not seen" axis.

Lead, South Dakota, 3,000 people. You see the mine at the top.

But there's one important difference: XENON100 only has 100 kilograms of xenon, as the name indicates. LUX will have 350 kilograms of xenon and there already exist plans for a bigger LUX with 3-5 tons of xenon.
Slightly off-topic: Dennis Overbye of the New York Times wrote a sad article called American Physics Dreams Deferred explaining that there is no funding for hard physics but there is a lot of money for fraudulent climate Marxists, thieves, fraudsters, and criminals for whom a decent government should only pay for the nooses
Because the signals per unit time are pretty much proportional to the mass, you may calculate how much time LUX will need to beat the results of XENON100. Size matters here.

The LUX detector, to be lowered to the gold mine.

So expect either faster discoveries or more stringent exclusion limits. But we will have to wait what they will observe. Don't expect any substantial data before 2013.

Two arrays with 61 photomultipliers each. The xenon will be outside them.

A photomultiplier should see every collision of a wimp with the xenon nucleus.

In 2010, engineer Wendy Zawada had to remove some last pile of rock and pocket the last gold – poor guy – to allow LUX to arrive.

Directions: Majorana Demonstrator (looking for neutrinoless double beta decay) in the left cavern, LUX in the right one.

Floor of the Davis cavern will host LUX.

Stainless steel plates on that floor: a lid of the tank.

Construction workers built the tank from the top, starting with the lid.

271,000 liters of purified water is included to protect the smaller detector with xenon from natural radioactive decays.

A diagram of the experiment.

LUX's Simon Fiorucci emigrated from EDELWEISS and XENON in Gran Sasso.

LUX's control room is above the tank, the tunnel goes to the Majorana Demonstrator.

Data taking may begin in October 2012.

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