Manufacturing Bits: Oct. 17

WIMP dark matter detector; tiny accelerator; MOMS sensors.


WIMP dark matter detector
The LUX-ZEPLIN (LZ) Group has taken another step towards finding an elusive part of the universe—dark matter.

The LZ Group consists of 250 scientists and engineers from 37 institutions in the U.S., U.K., Portugal, Russia and Korea. In 2012, the group built the so-called Large Underground Xenon (LUX) dark matter detector. The detector is based on a 370 kilogram liquid xenon time-projection chamber.

Targeted to detect galactic dark matter, LUX resides one mile below the earth in an underground laboratory within the Stanford Underground Research Facility in Lead, South Dakota.

The LUX detector (Source: SLAC)

More recently, the group has devised a new sensor array in hopes of detecting dark matter. In theory, 4.9% of the universe consists of observable matter, such as protons, neutrons and electrons. Then, some 68.3% of the universe is dark energy, while the remaining 26.8% is dark matter. Dark matter exists in the universe, but it is invisible to the entire electromagnetic spectrum.

There are several efforts to detect dark matter, which is composed of so-called weakly interacting massive particles (WIMPs). To date, though, researchers have failed to directly observe or detect dark mater or WIMPs.

Seeking to detect WIMPs, the LUX-ZEPLIN group has devised a new array of 32 light sensors, dubbed photomultiplier tubes (PMTs). Over time, the system will incorporate 500 PMTs. The sensors detect light flashes emitted when dark matter particles hit xenon atoms inside the LUX chamber. The array will collect light up to 10 times more efficiently than the previous detector. The tests, which are expected to take several months, began in October of 2017.

Tiny accelerator
The Friedrich-Alexander Universität Erlangen-Nürnberg (FAU) has disclosed the first results with the world’s smallest particle accelerator, a technology that fits on a microchip.

In 2015, FAU teamed up with Stanford University and eight other international partner institutions in the so-called Accelerator on a Chip International Program (ACHIP).

The goal is to devise a small accelerator. One possible configuration for ACHIP’s particle accelerator prototype is a system that is the size of a shoebox or smaller. ACHIP has been developing a way to distribute laser power and steer the electrons in the unit.

The goal of the technology is to fire laser beams in the structure to accelerate electrons. Researchers must also control the oscillation of light and the movement of electrons with precision at attoseconds or a billionth of a billionth of a second.

Researchers from Erlangen, Germany-based FAU have devised a new technique. It involves the intersection of two laser beams oscillating at different frequencies. This, in turn, generates an optical field at precise degrees.

The optical field remains in contact with the electrons and moves them in so-called travelling waves. In effect, the electrons continuously sense or surf the optical field.

With the technology, researchers have achieved an acceleration gradient at 2.2 giga-electron-volts per meter. But the acceleration distance is only 0.01 millimeters, which is not sufficient for practical applications. “This approach will hopefully enable us to make this innovative particle acceleration technique usable in a range of research areas and fields of application such as materials science, biology and medicine; one example might be particle therapies for cancer patients,” said Peter Hommelhoff, the chair of laser physics at FAU.

MOMS sensors
Imec has unveiled a pressure sensor based on micro-optomechanical systems (MOMS) technology.

Leveraging both MEMS and photonics, the sensor can be used in medical and life science apps. Pressure sensors are used to measure altitude depth or other parameters. These types of sensors are based on either MEMS or optical fiber technologies.

MEMS-based pressure sensors provide good performance and have a small size. Optical fiber sensors are suitable for use in harsh environments. But both types are sometimes complex and expensive.

Imec’s new MOMS-based pressure sensor combines the best of both MEMS and optical fiber. The technology shows a high tolerance to EMI interference and supports multiplexing. With the sensor, Imec has demonstrated a root mean square (rms) precision lower than 1Pa across a large range that could easily reach 100kP.

“Our advanced sensor could be used in a variety of (biomedical) applications such as intracranial pressure or intravascular blood pressure monitoring, where high-quality remote sensing is required. The sensor has also proven its biocompatibility and can be used in combination with MRI technology as there are no metal parts,” said Xavier Rottenberg, group leader and principal scientist at Imec. “With our current demonstrator, and the high performance it achieves on a large pressure range, Imec has demonstrated the superior performance of MOMS-based pressure sensors and their potential to complement – and in some applications even replace – current MEMS-based devices.”

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