Sharp minds at work

Lance Cooley

Lance Cooley, head of the Superconducting Materials Department, wrote this column.

A central mission of the Superconducting Materials Department in the Technical Division is the exploration of new materials and new processes that could have an impact on the design, engineering and construction of accelerator components. Although Fermilab is not a dedicated materials science laboratory, the laboratory relies on advances in materials to build the RF cavities, magnets and other accelerator tools needed to conduct research at the Energy and Intensity Frontiers as well as to make contributions to other fields.

Two of Fermilab’s Peoples Fellows reside in our department, Alex Romanenko and Tengming Shen. Both have won DOE Early Career Research Awards, and their research programs are off to fantastic starts, thanks to their sharp minds and creativity and to networks of worldwide collaborators seeded by the Technical Division.

Romanenko focuses on subtle aspects of niobium metal that limit the performance of superconducting RF cavities. His work could result in a significant reduction in the cost of cryogenic refrigeration for high-power linear accelerators as well as in gains in the manufacturing and processing yield for high-gradient cavities. Through a series of innovative measurements, he has proven that the current methods for treating cavities still leave behind hydrogen impurities just under the metal’s polished surface. Left unaltered, tiny hydride precipitates will form and change the metal’s structure and properties, negatively affecting the cavities’ performance. By understanding where the trace hydrogen is located and how it arrived there, Alex has begun teaching the community what preventive actions should be useful to take.

Shen focuses on superconducting wires and cables that can operate in ultrahigh magnetic fields, far above the limit of niobium-based compounds used for superconducting magnets today. He researches whether one of the high-temperature superconducting materials, called Bi-2212, could become the basis of a technology to produce magnetic fields in excess of 30 Tesla. He is collaborating with universities and wire vendors to improve wire raw material and fabrication and with magnet engineers to implement special processes that greatly improve the properties. His work paves the way for much stronger magnets that could cool muon particle beams or steer particles around a future high-energy circular collider.

A key ingredient to the success of these young investigator programs is their collaborations with external laboratories and universities. They exchange samples, compare measurements made with different instruments and discuss different points of view. These efforts reveal aspects of superconducting material never appreciated before by the accelerator science community. Without these connections, the important discoveries that are in motion now might not have taken hold. The success of our rising stars punctuates how effective these collaborations are.