Gizmorama - March 26, 2018
The search for dark matter is going to get much easier. It's all thanks to scintillator, a new material that is responsive to dark matter. Let the exploration begin!
Learn about this and more interesting stories from the scientific community in today's issue.
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*- New material capable of detecting dark matter, scientists say -*
Scientists believe a new material, known as a scintillator, will expand the search for dark matter.
New analysis suggests the scintillator material is sensitive to dark matter particles with less mass than a proton, which should allow scientists to look for dark matter among a previously unexplored mass range.
Weakly interacting massive particles, or WIMPs, describe dark matter particles with a mass greater than that of a proton. Scientists have tried to directly detect WIMPs using a variety of strategies, but with no success.
What dark matter consists of remains a mystery. Astronomers can only intimate its presence by measuring its gravitational influence. But researchers are hopeful that a search at a lower mass range could yield a breakthrough.
The detection abilities of the new scintillator material, described this week in the Journal of Applied Physics, require temperatures approaching absolute zero, or minus 460 degrees Fahrenheit.
The material is composed of gallium arsenide crystals, or GaAs, enhanced with silicon and boron. Models suggest the unique material should scintillate, or light up, when collisions with dark matter particles knock electrons away.
Researchers at the Lawrence Berkeley National Laboratory in California want to combine the material with a cryogenic photodetector, which can detect tiny amounts of light at extremely low temperatures.
"It's hard to imagine a better material for searching in this particular mass range," Stephen Derenzo, a senior physicist at LBL, said in a news release. "It ticks all of the boxes. We are always worried about a 'Gotcha!' or showstopper. But I have tried to think of some way this detector material can fail and I can't."
Gallium arsenide crystals are fairly easily grown. In recent lab tests, the crystals glowed intensely when electrons were expelled from the crystals' atomic structure. Additionally, the material doesn't suffer from some of the characteristics of other particle-detecting scintillators, such as afterglow, which can lead to a false signal.
Once constructed, the new GaAs scintillator will be positioned deep underground -- protected from interfering cosmic rays -- where scientists hope it will detect dark matter particles.
*-- Researchers trap particle-based microlaser inside optical cable, a first --*
For the first time, scientists have trapped a particle-based microlaser inside an optical cable. The breakthrough could allow scientists to deliver laser light to hard to reach locations.
"The flying microlaser could potentially be used to deliver light inside the body," Richard Zeltner, researcher at the Max Planck Institute for the Science of Light in Germany, said in a news release. "By inserting a fiber into the skin, a microlaser emitting at a suitable wavelength could deliver precisely positioned light for use with light-activated drugs."
In experiments, scientists used the flying microlaser to make extremely precise temperature measurements in real time.
The technology utilizes a whispering gallery mode resonator, featuring particles that amplify specific wavelengths of light. Just as sound waves move across the curved surfaces of the whispering gallery in St. Paul's Cathedral, light waves ripple across the inner surface of the resonator particles.
"This is the first demonstration of distributed sensing using a whispering gallery mode resonator," said Zeltner. "This unique approach to sensing potentially opens many new possibilities for distributed measurements and assessing physical properties remotely with high spatial resolution. For example, it could be useful for temperature sensing in harsh environments."
The resonator is housed inside of a hollow-core photonic crystal fiber. The glass microstructure surrounding the hollow core confines light to the inside of the fiber.
"For quite some time, our research group has been developing the technology necessary to optically trap particles inside hollow-core photonic crystal fibers," said researcher Shangran Xie. "In this new work, we were able to apply this technology not just to trap a particle but also to induce it to act as a laser that can be used for sensing over long distances in a fiber."
Once the first laser microparticle is trapped inside the fiber, a second laser pulse is used to excite the microparticle, causing the microparticle to emit light. As the microparticle moves through the fiber, scientists can measure changes in its laser emissions. In experiments, researchers used the technology to measure changes in temperature as the microparticle moved through the fiber.
"The spatial resolution of this distributed sensor is ultimately limited by the size of the particle," said Zeltner. "This means that, potentially, we could achieve spatial resolution as small as several micrometers over very long measurement ranges, which is a huge advantage of our system compared with other types of distributed temperature sensors."
Scientists described the technology in a new paper published this week in the journal Optics Letters.
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