DOE awarded Shen $500,000 per year for five years for his research into engineering high-field superconducting materials for advanced accelerator technology. If his team succeeds, the work could pave the way for the construction of high-field superconducting magnets for future accelerators such as Fermilab’s proposed muon collider, for energy upgrades of the Large Hadron Collider and for the development of new medical imaging devices.
Shen’s strategy is to search for a better magnet-making material. Scientists currently use two niobium-based materials, NbTi and Nb3Sn.
Scientists cooled magnets in the Tevatron with liquid helium to 4.2 Kelvin; they reached a magnetic field strength of 4.3 Tesla. The scientists who built the Large Hadron Collider cooled their magnets with superfluid liquid helium to an even colder 1.9 Kelvin and almost doubled that performance to 8.3 Tesla. Fermilab and other U.S. laboratories have recently developed new technology using niobium-tin, Nb3Sn, which scientists hope will help them make the jump to 12- to 13-Tesla magnets.
The next step, according to Shen, is to push the limit of superconducting magnet technology by exploring new materials beyond the niobium family. This would allow scientists to more than double the energy reach of the LHC without increasing the size of the accelerator, he said.
Shen plans to study a group of high-field superconductors, in particular Bi2Sr2CaCu2Ox. He expects he could use this material to build magnets with a reach of up to 50 Tesla.
Even better, the new material could be used to construct 1- to 5-Tesla magnets that operate at higher temperatures. Whereas current superconducting magnets must be cooled with liquid helium, Shen’s magnets could potentially be cooled with a simpler refrigeration unit.
“Helium is very expensive,” Shen said. “There are many places like Africa, India and China that would like to develop cryogen-free devices.”
The development of high-temperature superconductors could eventually lead to better power lines, faster computers and more energy-efficient transportation, Shen said.
“There are many superconducting materials and many more to be discovered,” he said. “The whole world could be superconducting.”
The objective of this project is to transform high-field superconductors, particularly Bi2Sr2CaCu2Ox, a high-temperature superconducting material that has magnetic field upper limits surpassing 100 Tesla at 4.2 K and can be fabricated into a multifilamentary round wire, to practical magnet conductors that can be used to generate fields above 20 Tesla for the next generation of accelerators. Studies will focus on
(1) understanding the micro- and nano-structures that produce high critical current density Jc in long-length conductors through extensive electromagnetic measurements and innovative micro-structural characterizations;
(2) advancing high-temperature superconducting magnet engineering through designing, fabricating, and testing Bi2Sr2CaCu2Ox insert coils that reach 30 Tesla in a useful aperture of over 30 mm. This research will result in a high-performance, 20-50 Tesla class conductor for the next generation of accelerators and spectrometers for medical imaging and advanced materials research. The fundamental understanding gained of superconductor synthesis and how nanostructure underpins the superconducting property will provide insights for the development of a large class of superconducting materials for magnet and energy applications.
Muon Accelerator Program Research Goals
Muons are point-like particles that are like electrons, except they are 200 times heavier, and are unstable. In fact, muons live for only two-millionths of a second before they decay. That doesn’t sound very long, but it is just long enough to collect them, form them into a beam, and either accelerate them to high energy or stop them in a target. This is good because muons provide a unique tool for addressing fundamental questions in physics, or for exploring the properties of materials. The challenge is to get enough muons to do the job, and to concentrate them within a small target, or within a very bright beam.
The Muon Accelerator R&D program is focused on developing the concepts and technologies needed to make vast quantities of muons (of order 1014 per second), reduce their energy-spread so that they can be captured within bunches, and form them into a very bright beam that can be either stopped or accelerated.
Beyond this, the MAP program is focused on developing two particularly exciting applications that use this very bright muon beam: Neutrino Factories and Muon Colliders.
Particle physicists have developed a set of nine questions about the universe. The muon collider would help to answer them. It could answer questions about dark matter and antimatter.
What is the nature of the universe and what is it made of?
What are matter, energy, space and time?
How did we get here and where are we going?
The goals for a Neutrino Factory is to make enough neutrinos of the right type in a controlled way so that new experiments can teach us more about this mysterious particle, and reveal its properties and its role in the Universe.