Global team of scientists finish assembling next-generation dark matter detector

Global team of scientists finish assembling next-generation dark matter detector
Researchers examine the foil-wrapped LUX-ZEPLIN xenon detector. Credit: Matt Kapust

The key component of the LUX-ZEPLIN experiment is ready to be sealed and lowered nearly 1.5 km underground, where it will search for dark matter.

Dark matter is a mysterious form of matter thought to make up around 85 percent of the mass of the universe. However, because it is predicted to interact only very weakly with ordinary matter, it has so far not been detected.

LUX-ZEPLIN (LZ) will be the most sensitive dark matter experiment ever built. On 26 July, researchers finished assembling its centrepiece, the liquid Time Projection Chamber (TPC), at the Sanford Underground Research Facility in South Dakota, U.S..

"This will be at the heart of the LZ dark matter experiment," said Professor Henrique Araújo, from the Department of Physics at Imperial College London, who leads the LZ collaboration efforts in the UK and co-led the development of the TPC with Professor Tom Shutt from SLAC National Accelerator Laboratory.

13,500 hours of effort

To assemble the TPC, 250 members from 37 institutions from across the globe came together to ensure the mechanical, optical, electrical, radiological and cleanliness requirements of the project were met.

Global team of scientists finish assembling next-generation dark matter detector
The recently assembled LUX-ZEPLIN xenon detector in the Surface Assembly Lab cleanroom at Sanford Underground Research Facility on 26 July 2019. Credit: Matt Kapust.

Manufacture of the tens of thousands of components that make up the TPC started in 2015, and assembly of the instrument began in December 2018. The integration stage involved 13,500 hours of effort—a significant fraction of which was devoted to maintaining the required ultra-clean conditions at the surface-level assembly lab.

Next, it will be inserted into its cryostat vessel—a chamber that maintains cold temperatures—and lowered nearly 1.5km underground into a disused goldmine, ready to hopefully detect dark matter. Operations are planned to start in mid-2020.

"We have some things in common with a ," said Professor Araújo. "Before you launch, you do all of your work on the ground for years, perfecting the engineering so your instrument will work no matter what. LZ is a bit like a space experiment, just headed the opposite direction. We cannot expose it to underground air—that would compromise its performance. Once you deploy it underground, that's it. It has to work."

Detecting WIMPs

Once underground, the detector will be cooled to -100°C and filled with ten tonnes of liquid xenon. Because xenon is a heavy element, there is a higher chance of xenon atoms interacting with hypothetical dark matter particles called WIMPs—weakly interacting massive particles.

Researchers believe that if a WIMP interacts with a xenon atom, it will produce two flashes of light. One appears promptly, when the particle collides with a xenon atom, which recoils through the liquid. The second is generated by electrons shaken off by the collision, which are guided to the top of the detector and accelerated through a layer of gaseous xenon above the liquid.

Global team of scientists finish assembling next-generation dark matter detector
The detector in inspected under UV light. Credit: Nicolas Angelides

Although these flashes would be imperceptible to the human eye, the detector is lined with hundreds of photomultiplier tubes. These ultrasensitive sensors can amplify a signal from even a single photon of light.

Decades of development

The TPC design employed by LZ has been perfected over decades of experimentation with similar detectors that allow researchers to determine where an interaction happens, and whether it is likely due to a background interaction in the instrument or a true dark matter signal. Amongst these were the ZEPLIN-III experiment at the Boulby Mine in North Yorkshire, led by Imperial, and the US-led LUX experiment—which gave rise to LZ.

Being buried deep underground protects the experiment from too many background interactions from processes readily detected at the surface that could obscure a dark signal, such as the cosmic rays that shower the Earth from outer space.

Professor Shutt said: "The TPC is a complex system and it's a major achievement to have it fully assembled. It takes us one important step closer to being able to look for .

"It is also gratifying because it involved assembling a large number of subsystems designed and built by groups across the US and the UK over a number of years. So, it's a coming together of sorts for the collaboration."


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Scientists piece together the largest U.S.-based dark matter experiment

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Aug 07, 2019
Dark matter is a supersolid that fills 'empty' space, strongly interacts with ordinary matter and is displaced by ordinary matter. What is referred to geometrically as curved spacetime physically exists in nature as the state of displacement of the supersolid dark matter. The state of displacement of the supersolid dark matter is gravity.

The supersolid dark matter displaced by a galaxy pushes back, causing the stars in the outer arms of the galaxy to orbit the galactic center at the rate in which they do.

Displaced supersolid dark matter is curved spacetime.

In the Bullet Cluster collision the dark matter has not separated from the ordinary matter. The collision is analogous to two boats that collide, the boats slow down and their bow waves continue to propagate. The water has not separated from the boats, the bow waves have. In the Bullet Cluster collision the galaxy's associated dark matter displacement waves have separated from the colliding galaxies, causing the light to lense

Aug 07, 2019
Please see Possible Dark Matter Mass Candidates in Spinning Sphere Theory. This theory uses fractals of one, two, and three dimensional particles to predict the mass of dark matter particles.

Aug 07, 2019
Recently two papers have been published. The first one deals with the measurement of the speed of rotation of galaxies and, in our view, closes the issue of the existence of dark matter. The second one argues that the expansion of the universe is not accelerating. However, this fact does not answer the question as to what in general is the cause of the universe's expansion and does not address the widespread opinion that 70% of the universe consists of dark energy.
https://www.acade...k_Energy

Aug 08, 2019
The cause of universal expansion is due to birth of new galaxies out of "nowhere": we need millions years of accumulated observation in order to confirm this fact. The dark is dark because it cannot be seen, however, it is an omnipresent element which shall be added just atop the hydrogen, shall provide us with source of unlimited energy, artificial / temporary dimension creation, FTL interstellar travel and much more.
We need to earn the right to use this source of energy, nothing in this universe is free of charge. I give you about 300 years from now, or more, or never if we destroy one another.

Aug 08, 2019
dr t, if it takes millions of years to confirm?
how can you honestly claim tour fabulisms are a "fact"

unless you are a lot older than you look?

or you have a time machine?
if so can i borrow it for a short jaunt to 812 ad
monday the twelfth of october
about nones
om the escarpment overlooking the vale of pojhola?

kiitos, kaveri!

Aug 12, 2019
Does dark matter really exist, or is there something wrong with our understanding of gravity and its role in the expansion of the apprehensible universe? The expansion of the universe strikes me as a tug of war between the explosive force of the Big Bang and the counteracting role of gravity involving visible matter, where gravity was at its strongest at an earlier time and involved giant galaxies, but which lessened as time has gone by resulting in ever smaller accretions of matter as the explosive force of the Big Bang has overcome gravitational forces. This explains the general 'speeding up' of galaxies as the distance between them increases because they have been gradually released from gravitational bonds and are increasingly subject to universal expansion. Local gravity still holds sway between local groups of galaxies as well as matter influenced by black holes within accretions of matter such as galactic centers. Perhaps the gravitational constant needs reevaluating.

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