Leszek Motowidlo, 1951 - 2016

December 19, 2016 (PO50).  Dr. Leszek (Lesh) Motowidlo, 65, of Southington Connecticut, ended his battle with cancer, September 21, 2016, in Connecticut, USA.  He was the husband of Diane Motowidlo.

Born on February 5, 1951, in Chambon-Feugerolles, France, he was the son of Gracjan and Jeanine Motowidlo of New Britain. His family immigrated with him to the United States in 1955. Lesh began his journey in applied physics with studies at Central Connecticut State University (CCSU). He then went on to the University of Connecticut and received his M.S. in Physics in 1976 and his Ph.D. in Metallurgy in 1981 under the supervision of Dr. James Galligan. Leszek received the Distinguished Alumni Award from the UCONN School of Engineering in 1996 for his outstanding contributions to both the science and engineering applications of superconducting materials. He gave the DeVivo Lecture in Materials Science 1993 at Northeastern University. He was a member of Sigma Xi Research Society, the New York Academy of Science 2000, and the Academy of Distinguished Engineers 1996.

Lesh contributed over 35 years to research, development, and manufacture in the superconductivity and low-temperature communities. He first joined Varian Associates and served as Visiting Scientist at MIT working with John Williams on superconducting magnet development. He maintained ties to Connecticut throughout his career, starting from work at the University of Connecticut on mechanical properties of lead at liquid helium temperature, and continuing through his association with Intermagnetics General Corporation (IGC), Supercon, and his subsequent venture as founder and CEO of SupraMagnetics.  His body of work reflects an understanding of solid state physics, which he applied to produce numerous innovations in practical superconducting wires. His achievements as an innovator and entrepreneur are matched well by his contributions as a scientist.

Working in the late 1980s with Mike Walker and Bruce Zeitlin, Lesh pioneered artificial pinning-center (APC) conductors by co-fabricating niobium and Nb-Ti into homogeneous multi-component nanostructures. The concept of assembling the intended nanostructure by hand at a much larger size provided control over the fraction and arrangement of flux-pinning centers, whereby significantly higher critical current could be achieved than by random precipitates. This work continued through the 1990s and 2000s and expanded to include other metals, including magnetic components such as nickel. An undulator magnet for a Brookhaven National Laboratory light source project was fabricated from one of the final APC conductors. Working with Mark Rudziak and Terence Wong at Supercon, an APC conductor using magnetic nickel-copper alloy pinning centers endures as having the highest measured critical current density of any Nb-Ti wire at the common benchmark of 5 T field and 4.2 K temperature, reaching above 5000 A/mm². For comparison, conventionally processed strands with α-Ti pinning centers achieved only up to 4000 A/mm² while those used for magnets for the Large Hadron Collider (LHC) achieved less than 3200 A/mm².

The advent of high-temperature superconductors motivated Lesh to take on challenges of conductors based on Bi-2212 and Bi-2223. Working in collaboration with Showa of Japan he developed 1st generation HTS wires with state-of-the-art J_c. At IGC, Supercon, and SupraMagnetics, Lesh developed new approaches to powder-in-tube (PIT) technologies, where he developed innovations in milling, re-stacking, wire-drawing and other conductor processing. By the mid-1990s, Lesh and coworkers at IGC and the University of Wisconsin demonstrated Bi-2212 round wires with high current density using a partial melt process. A key insight noted that current density increased with reduction of the powder core diameter. Rutherford cables were manufactured from these conductors in the late 1990s by collaborators at Lawrence Berkeley National Laboratory. Processing improvements also led to long-length Bi-2223 conductors and prototype coils at IGC by 1993.

Through Supramagnetics, Lesh produced a hallmark Nb₃Sn product with a novel octagonal geometry. The design allowed the introduction of high-strength components at interstices, making it the only internally reinforced Nb3Sn wire. He also successfully pioneered the use of Cu₅Sn₄ as a low-cost alternative to NbSn₂ powders typically used to make Nb₃Sn by the PIT route. The combination of uniform high-quality Cu₅Sn₄ powders and the PIT design provided as an excellent test bed for exploring alloying additions that could help increase the high-field performance of Nb₃Sn for future accelerator magnets beyond the field range of the LHC. In his final program supported by the US Department of Energy, he successfully showed that mixtures of SnO₂ and Cu₅Sn₄ powders could be used to form ZrO₂ precipitates in Nb-1Zr alloy tubes, which later resulted in Nb₃Sn layers with ultra-fine grain size and improved flux-pinning properties at high fields. In conjunction with successes at the Ohio State University, this final design contributes a scalable route to APC-Nb₃Sn, and it should continue to provide an economical test bed for the development of future low-cost high-field Nb₃Sn conductors. He was the author or coauthor of over 120 papers and was awarded 10 patents in superconducting materials.

Throughout his career, Lesh was an enthusiastic contributor to the High Energy Physics and Energy Efficiency conductor communities. He stood out for his positive, can-do attitude which inspired others to do their best. He was extremely creative as indicated by his patents and research ideas.  His regular presentations at the annual High Field Superconductor Workshops will be greatly missed.

Lance Cooley, David Larbalestier Peter Lee, Hem Kanithi, Bruce Zeitlin