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	Friday, April 3, 2015

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New magnet at Fermilab achieves high-field milestone

This magnet recently achieved an important milestone, reaching its design field of 11.5 Tesla. It is the first successful niobium-3-tin, twin-aperture accelerator magnet in the world. Photo: Sean Johnson, TD

Last month, a new superconducting magnet developed and fabricated at Fermilab reached its design field of 11.5 Tesla at a temperature nearly as cold as outer space. It is the first successful twin-aperture accelerator magnet made of niobium-3-tin in the world.

The advancements in niobium-3-tin, or Nb₃Sn, magnet technology and the ongoing U.S. collaboration with CERN on the development of these and other Nb₃Sn magnets are enabling the use of this innovative technology for future upgrades of the Large Hadron Collider (LHC). They may also provide the cornerstone for future circular machines of interest to the worldwide high-energy physics community. Because of the exceptional challenges — Nb₃Sn is brittle and requires high-temperature processing — this important milestone was achieved at Fermilab after decades of worldwide R&D efforts both in the Nb₃Sn conductor itself and in associated magnet technologies.

Superconducting magnets are at the heart of most particle accelerators for fundamental science as well as other scientific and technological applications. Superconductivity is also being explored for use in biosensors and quantum computing.

Thanks to Nb₃Sn's stronger superconducting properties, it enables magnets of larger field than any in current particle accelerators. As a comparison, the niobium-titanium dipole magnets built in the early 1980s for the Tevatron particle collider produced about 4 Tesla to bend the proton and antiproton beams around the ring. The most powerful niobium-titanium magnets used in the LHC operate at roughly 8 Tesla. The new niobium-3-tin magnet creates a significantly stronger field.

Because the Tevatron accelerated positively charged protons and negatively charged antiprotons, its magnets had only one aperture. By contrast, the LHC uses two proton beams. This requires two-aperture magnets with fields in opposite directions. And because the LHC collides beams at higher energies, it requires larger magnetic fields.

In the process of upgrading the LHC and in conceiving future particle accelerators and detectors, the high-energy physics community is investing as never before in high-field magnet technologies. This creative process involves the United States, Europe, Japan and other Asian countries. The latest strategic plan for U.S. high-energy physics, the 2014 report by the Particle Physics Project Prioritization Panel, endorses continued U.S. leadership in superconducting magnet technology for future particle physics programs. The U.S. LHC Accelerator Research Program (LARP), which comprises four DOE national laboratories — Berkeley Lab, Brookhaven Lab, Fermilab and SLAC — plays a key role in this strategy.

The 15-year investment in Nb₃Sn technology places the Fermilab team led by scientist Alexander Zlobin at the forefront of this effort. The Fermilab High-Field Magnet Group, in collaboration with U.S. LARP and CERN, built the first reproducible series in the world of single-aperture 10- to 12-Tesla accelerator-quality dipoles and quadrupoles made of Nb₃Sn, establishing a strong foundation for the LHC luminosity upgrade at CERN.

The laboratory has consistently carried out in parallel an assertive superconductor R&D program as key to the magnet success. Coordination with industry and universities has been critical to improve the performance of the next generation of high-field accelerator magnets.

The next step is to develop 15-Tesla Nb₃Sn accelerator magnets for a future very high-energy proton-proton collider. The use of high-temperature superconductors is also becoming a realistic prospect for generating even larger magnetic fields. An ultimate goal is to develop magnet technologies based on combining high- and low-temperature superconductors for accelerator magnets above 20 Tesla.

The robust and versatile infrastructure that was developed at Fermilab, together with the expertise acquired by the magnet scientists and engineers in design and analysis tools for superconducting materials and magnets, makes Fermilab an ideal setting to look to the future of high-field magnet research.

—Emanuela Barzi, Technical Division

Photo of the Day

Between the lines

Looking up from the northeast corner of the ground floor of Wilson Hall gives you an appreciation of the building's geometry. Photo: Robert Carrara, OCIO

In the News

Searching for a 'quantum foam' bubbling through the universe

From ars technica, April 2, 2015

Two of our most successful theories, quantum mechanics and general relativity, are at odds with each other in a number of areas. They make conflicting predictions—and, for some time, the quest has been on to find a deeper theory, one that resolves the conflicts and provides a better view of reality. Such a theory would describe how gravity works at a quantum level, and as such it would be known as a theory of quantum gravity.

Frontier Science Result: PICO

Seeing dark matter

A calibration event from PICO-2L shows boiling from multiple recoiling atomic nuclei. PICO-2L is designed to see a recoiling nucleus a from dark matter interaction.

We are not yet seeing dark matter, but we could.

Dark matter is all around us. There is six times more dark matter in our universe than there is the ordinary matter that we experience every day. Like neutrinos, dark matter can pass right through us and the Earth without being noticed. Moreover, dark matter does not interact with light, so we cannot see it, except perhaps in a bubble chamber.

Bubble chambers, including Fermilab's 15-foot bubble chamber, were among the largest and most important particle detectors of the 1960s and 1970s investigating the physics of the weak force. In operation, bubble chambers are filled with liquid held above its boiling point temperature at the bubble chamber's expansion pressure. The liquid boils if a nucleation site, such as a dust grain or a surface scratch, is available. In their absence, ionizing radiation (that is, particle tracks) can create bubbles. The exploding line of bubbles formed along a track lets physicists "see" the particle and photograph it.

The PICO collaboration, of which Fermilab is a member (formed from the merger of PICASSO and COUPP), has revisited bubble chamber technology in order to look for dark matter particles. While dark matter particles pass through the Earth, they may very occasionally bounce off an atomic nucleus. PICO bubble chambers can see these nuclear recoils. They do not see most other types of ionizing radiation that can emulate dark matter in other detector technologies. PICO can also see bubbles from alpha radiation, but these are distinguishable as they sound different from those made by dark matter. As a bubble rapidly grows, PICO uses ultrasonic acoustic sensors to measure the sound of this small explosion and to reject the louder bubbles created by alpha radiation.

The PICO-2L bubble chamber operated in 2013 and 2014 at SNOLAB, 6,800 feet underground in a Canadian nickel mine. Using 2 liters of perfluoropropane, C₃F₈, PICO-2L has set the world's strongest proton spin-dependent dark matter search limits. Fluorine provides the most sensitive target nucleus to detect a spin-dependent dark matter interaction, which means future large bubble chambers may see, and hear, dark matter interactions that other detectors can not.

—Alan Robinson, University of Chicago

In Brief

LDRD Fest - today at 4 p.m.

Today four Fermilab scientists will discuss cutting-edge scientific and technological projects aligned with mission and strategic plans of Fermilab and DOE.

Intended for a broad audience, their talks, titled "LDRD Fest," will take place at today at 4 p.m. in One West as part of the Joint Experimental-Theoretical Physics Seminar.

The speakers are Fermilab scientists Phil DeMar, Juan Estrada, Hogan Nguyen and Henryk Piekarz. They will describe and give a status update of their LDRD projects in areas of accelerator magnets, computing network traffic, cosmic microwave background detectors and CCDs for coherent neutrino scattering.

Death

In memoriam: Tom Jordan

Tom Jordan

Tom Jordan, project coordinator for QuarkNet from its inception, died on Monday, March 30. He was 52.

Jordan worked at Fermilab from 1998 to 2006, before moving to the University of Florida and then to the University of Notre Dame.

QuarkNet brings high school physics teachers into the particle physics research community at 50 universities and labs nationwide. Jordan's vision for the program and his tireless drive supporting teachers and mentors instilled and maintained excitement for physics research and physics education.

David Jones of Florida International University remembers Jordan's enjoyment of physics and ability to convey it.

"Tom loved all aspects of QuarkNet, from troubleshooting code and electronics to the bigger questions," Jones said. "When he was working with students, he had a special ability to connect with them and get them to be curious about the cosmos or high-energy physics."

Illinois teacher Darwin Smith spent a summer working at Fermilab for Jordan on QuarkNet.

"As a non-physics major there were gaps in my knowledge about things we were doing," Smith said. "Tom was incredibly patient, and I have always appreciated that."

Boston teacher Rick Dower was reminded of Jordan's educational focus.

"Tom knew that developing the process of inquiry was more important than any specific answer he could give. His legacy is the sharing of that vision with so many teachers," Dower said.

Jordan is survived by his wife and five daughters. Read his full obituary.

—Spencer Pasero, Education Office