Beyond the WIMP: Unique crystals could expand the search for dark matter


IMAGE: An electronic simulation of the massive circulation of dark matter in deep space. An overlay chart (in white) demonstrates how a crystal sample extremely scintillates, or radiances, when exposed to …
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Credit: Centuries Simulation, Berkeley Laboratory

A brand-new particle detector style proposed at the United States Department of Energy’s Lawrence Berkeley National Lab (Berkeley Laboratory) might significantly widen the look for dark matter– makings up 85 percent of the overall mass of deep space yet we have no idea exactly what it’s made from– into an uncharted world.

While numerous big physics experiments have actually been targeting thought dark matter particles called Pansies, or weakly connecting huge particles, the brand-new detector style might scan for dark matter signals at energies countless times lower than those quantifiable by more traditional PUSHOVER detectors.

The ultrasensitive detector technology integrates crystals of gallium arsenide that likewise consist of the components silicon and boron. This mix of components triggers the crystals to scintillate, or illuminate, in particle interactions that knock away electrons.

This scintillation home of gallium arsenide has actually been mostly undiscovered, stated Stephen Derenzo, a senior physicist in the Molecular Biophysics and Integrated Bioimaging Department at Berkeley Laboratory and lead author of a research study released March 20 in the Journal of Applied Physics that information the product’s residential or commercial properties.

” It’s difficult to envision a much better product for browsing in this specific mass variety,” Derenzo stated, which is determined in MeV, or countless electron volts. “It ticks all packages. We are constantly fretted about a ‘Gotcha!’ or showstopper. However I have actually aimed to consider some method this detector product can stop working and I cannot.”

The development originated from Edith Bourret, a senior personnel researcher in Berkeley Laboratory’s Products Sciences Department who years previously had actually looked into gallium arsenide’s possible usage in circuitry. She offered him a sample of gallium arsenide from this previous work that included included concentrations, or “dopants,” of silicon and boron.

Derenzo had actually formerly determined some uninspired efficiency in a sample of commercial-grade gallium arsenide. However the sample that Bourret handed him displayed a scintillation luminosity that was 5 times brighter than in the business product, owing to included concentrations, or “dopants,” of silicon and boron that imbued the product with brand-new and boosted residential or commercial properties. This boosted scintillation suggested it was much more conscious electronic excitations.

” If she had not handed me this sample from more than 20 years back, I do not believe I would have pursued it,” Derenzo stated. “When this product is doped with silicon and boron, this ends up being essential and, mistakenly, an excellent option of dopants.”

Derenzo kept in mind that he has had a longstanding interest in scintillators that are likewise semiconductors, as this class of products can produce ultrafast scintillation beneficial for medical imaging applications such as ANIMAL (positron emission tomography) and CT (computed tomography) scans, for instance, in addition to for high-energy physics experiments and radiation detection.

The drugged gallium arsenide crystals he studied appear appropriate for high-sensitivity particle detectors since very pure crystals can be grown commercially in plus sizes, the crystals show a high luminosity in action to electrons booted far from atoms in the crystals’ atomic structure, and they do not seem impeded by common undesirable impacts such as signal afterglow and dark existing signals.

A few of the bigger WIMP-hunting detectors – such as that of the Berkeley Lab-led LUX-ZEPLIN job now under building and construction in South Dakota, and its predecessor, the LUX experiment – include a liquid scintillation detector. A big tank of liquid xenon is surrounded by sensing units to determine any light and electrical signals anticipated from a dark matter particle’s interaction with the nucleus of a xenon atom. That kind of interaction is referred to as a nuclear recoil.

On the other hand, the crystal-based gallium arsenide detector is developed to be conscious the slighter energies connected with electron recoils– electrons ejected from atoms by their interaction with dark matter particles. Just like LUX and LUX-ZEPLIN, the gallium arsenide detector would have to be put deep underground to protect it from the common bath of particles drizzling down on Earth.

It would likewise have to be combined to light sensing units that might discover the few infrared photons (particles of light) anticipated from a low-mass dark matter particle interaction, and the detector would have to be cooled to cryogenic temperature levels. The silicon and boron dopants might likewise perhaps be enhanced to enhance the total level of sensitivity and efficiency of the detectors.

Due to the fact that dark matter’s makeup is still a secret– it might be made up of one or lots of particles of various masses, for instance, or might not be made up of particles at all– Derenzo kept in mind that gallium arsenide detectors supply simply one window into dark matter particles’ possible hiding locations.

While Pansies were initially believed to populate a mass variety determined in billions of electron volts, or GeV, the gallium arsenide detector technology is appropriate to discovering particles in the mass variety determined in countless electron volts, or MeV.

Berkeley Laboratory physicists are likewise proposing other kinds of detectors to broaden the dark matter search, consisting of a setup that utilizes an unique state of cooled helium referred to as superfluid helium to straight discover so-called “light dark matter” particles in the mass series of countless electron volts (keV).

” Superfluid helium is clinically complementary to gallium arsenide considering that helium is more conscious dark matter interactions with atomic nuclei, while gallium arsenide is delicate to dark matter connecting with electrons,” stated Dan McKinsey, a professors senior researcher at Berkeley Laboratory and physics teacher at UC Berkeley who belongs of the LZ Cooperation and is carrying out R&D on dark matter detection utilizing superfluid helium.

” We have no idea whether dark matter engages more highly with nuclei or electrons– this depends upon the particular nature of the dark matter, which is up until now unidentified.”

Another effort would utilize gallium arsenide crystals in a various method to the light dark matter search based upon vibrations in the atomic structure of the crystals, referred to as optical phonons. This setup might target “light dark photons,” which are thought low-mass particles that would act as the provider of a force in between dark matter particles – comparable to the traditional photon that brings the electro-magnetic force.

Still another next-gen experiment, referred to as the Super Cryogenic Dark Matter Browse experiment, or SuperCDMS SNOLAB, will utilize silicon and germanium crystals to hunt for low-mass Pansies.

” These would be complementary experiments,” Derenzo stated of the lots of techniques. “We have to take a look at all the possible mass varieties. You do not wish to be tricked. You cannot omit a mass variety if you do not look there.”


Stephen Hanrahan, a personnel researcher in Berkeley Laboratory’s Molecular Biophysics and Integrated Bioimaging Department; and Gregory Bizarri, a senior speaker in making at Cranfield University in the U.K., likewise took part in this research study. The work was supported by Advanced Crystal Technologies Inc.

Lawrence Berkeley National Lab resolves the world’s most immediate clinical obstacles by advancing sustainable energy, safeguarding human health, developing brand-new products, and exposing the origin and fate of deep space. Established in 1931, Berkeley Laboratory’s clinical competence has actually been acknowledged with 13 Nobel Prizes. The University of California handles Berkeley Laboratory for the United States Department of Energy’s Workplace of Science. For more, see

DOE’s Workplace of Science is the single biggest advocate of standard research study in the physical sciences in the United States, and is working to deal with a few of the most important obstacles of our time. For more details, please see

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