Manufacturing Bits: Aug. 28

Neutron scattering; 6D measurements; China’s neutron source.


Neutron scattering
The Department of Energy’s Oak Ridge National Laboratory has reached what the agency says is the world’s highest power level for a neutron source.

Oak Ridge has several facilities, including the so-called Spallation Neutron Source (SNS). The SNS is used in a metrology field called neutron scattering. Used in physics, chemistry, biology, and materials science, neutron scattering helps measure and unravel the makeup of complex structures.

The Spallation Neutron Source at the Department of Energy’s Oak Ridge National Laboratory (Source: Oak Ridge)

Started in 2006, SNS is said to be the world’s most powerful pulsed accelerator-based neutron scattering facility. The facility recently reached a new milestone by operating a complete neutron production run cycle at 1.3 megawatts. “Prior to running at 1.3MW, the last SNS neutron production run cycle was from November 1 to December 20, 2017, was operating at 1.2MW,” according to officials from Oak Ridge.

The facility produces neutrons with an accelerator-based system. The neutron itself is a subatomic particle. It has no electric charge and a mass slightly larger than a proton. Neutrons and protons make up the nucleus of an atom.

The SNS, meanwhile, accelerates protons at nearly 90% the speed of light down a linear accelerator. Then, the protons move into a ring, which compresses the proton pulses. The protons collide with a liquid mercury target, which then creates neutrons. Then, the neutrons are directed to various instruments.

The instruments provide neutron diffraction, scattering and depth profiling of a given sample. Here is a list of instruments.

The SNS has been able to operate at 1.3 megawatts during a 12-week production cycle. This, in turn, enables researchers to conduct faster scientific analyses.

As protons (yellow) strike the target vessel and pass into the liquid mercury inside, the protons are absorbed, creating neutrons (blue) that are then sent through moderators and beam tubes to research instruments to study the fundamental properties of materials. (Image credit: ORNL/Jill Hemman)

6D measurements
Using a replica of the SNS’ linear accelerator, Oak Ridge and the University of Tennessee have demonstrated the ability to make measurements in six dimensions.

Six-dimensional (6D) space includes the existing three dimensions. But it also includes three additional coordinates on the x, y, and z axes to track motion or velocity, according to researchers at Oak Ridge.

For years, the industry has attempted to develop 6D measurement capabilities. One way is to add three 2D measurements together, thereby creating a 6D representation. But this path falls short of providing actual 6D measurements—2D measurements becomes more difficult in higher dimensions.

To enable six-dimensional or 6D measurements, researchers build a replica of the front-end assembly of the linear accelerator, or linac, at the beam test facility. Then, they developed a new radio frequency quadrupole, the first accelerating element located at the linac’s front-end assembly at the SNS.

The artistic representation illustrates a measurement of a beam in a particle accelerator, demonstrating the beam’s structural complexity increases when measured in progressively higher dimensions. Each increase in dimension reveals information that was previously hidden. (Image credit: ORNL/Jill Hemman)

One of the challenges is to avoid or mitigate beam halo or beam loss. This is when particles travel to the outer extremes of the beam and are lost. Another challenge is to develop software tools, which can analyze 5 million data points in 6D measurements.

“Our goal is to better understand the physics of the beam so that we can improve how accelerators operate,” said Sarah Cousineau, group leader at Oak Ridge and a professor at University of Tennessee. “Part of that is related to being able to fully characterize or measure a beam in 6D space—and that’s something that, until now, has never been done.

“Right away we saw the beam has this complex structure in 6D space that you can’t see below 5D—layers and layers of complexities that can’t be detangled,” Cousineau said. “The measurement also revealed the beam structure is directly related to the beam’s intensity, which gets more complex as the intensity increases.”

China’s neutron source
After several years in development, China has opened its first spallation neutron source.

China’s Institute of High Energy Physics (IHEP) has completed and opened the so-called China Spallation Neutron Source (CSNS). Located in the Guangdong province, CSNS is composed of an 80 MeV linac and a 1.6GeV rapid cycling synchrotron (RCS).

It has a target station with three initial instruments used for neutron scattering research. It can be used in various fields, such as lithium-ion battery materials, rare earths, high-temperature superconductors and functional films.

“CSNS is like a super microscope and is an ideal probe for studying the micro-structure of materials. For example, we can use neutron scattering technology to study the residual stress of large metal parts, which is very important for improving the design of aircraft engines and key modules for high-speed trains,” said Chen Hesheng, manager of the CSNS project.

CSNS will provide a research platform for fundamental research and high-tech development in many fields, such as materials science and technology, physics, life sciences, chemistry, and new energy. (Image by IHEP)

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