Internationally renowned physicist Joel Hosea remembered for a 50-year career that encompassed much of PPPL’s history
The story of Joel Hosea’s career is the story of PPPL. The Laboratory, founded as Project Matterhorn in 1951, had only been called the Princeton Plasma Physics Laboratory (PPPL) for seven years when Hosea began work there in 1968. He worked at many of the Laboratory’s major experiments and devoted his 50-year career to research at PPPL and around the world.
Hosea died on Aug. 25, just a day after beginning treatment at the Mayo Clinic in Minnesota. He was 79.
The physicist was an internationally-known expert in radio frequency (RF) heating of plasmas, a technique that uses radio frequency waves to heat plasma to extremely high temperatures to produce fusion energy, which powers the suns and the stars, to generate electricity.
“Joel was a major player and a pioneer at this Laboratory,” said Rich Hawryluk, associate director for fusion and former interim director of PPPL, who had known Hosea since both were young physicists on the Princeton Large Torus (PLT) experiment in the 1970s. “He was one of the most energetic people that I’ve known and to find out this has happened was just very shocking. He’s going to be terribly missed. He had an extensive knowledge of everything in the RF community around the world.”
Hosea was a strong advocate for the RF program that researched the use of high-frequency radio waves to produce what is called the ion cyclotron range of frequency (ICRF) to heat plasmas in a method similar to the way microwaves heat food. “He could be tenacious,” said Dale Meade, a former deputy director at PPPL. “The ICRF group was a really strong group of physicists, engineers and technicians. It was one of the strongest core competencies in the Laboratory.”
“Joel was quite a force to work with,” recalled engineer Nevell Greenough, who worked closely with Hosea. “As you worked with him, you appreciated his force, his way of getting things done and being extremely dedicated to the program and pushing people to excel.”
Hosea grew up in Atlanta and in Birmingham, Alabama. He attended Auburn University in Alabama where he met his wife, Kathy. He went on to get his doctorate from Stanford University in 1966. After graduation, Hosea was a National Science Foundation post-doctorate associate at the Saclay Nuclear Research Center in France for two years.
When Hosea joined PPPL in March 1968, he embarked on his life’s work on RF heating. His early work on the Model C Stellarator with mentor Rolf Sinclair, one of the original Project Matterhorn physicists, was on ion cyclotron heating. The process employs radio waves at the same frequency as the plasma ions that travel around the doughnut-shaped magnetic field inside the fusion device called a tokamak.
He continued RF work on the Symmetric Tokamak, which began experiments in the 1970s, and later became the RF group head for that experiment. He went on to study RF waves on the Princeton Large Torus (PLT), which began operating in 1975. He became project head of the PLT in 1980, which enabled him to carry out an extensive research program on RF heating and current drive. In 1984, researchers used ion-cyclotron heating on PLT to produce temperatures of 60 million degrees centigrade, a record for that heating technique.
Hosea was known for his extensive knowledge of engineering and for expecting physicists on his staff to develop the same knowledge. Retired physicist Randy Wilson began working with him on PLT in 1980 and became a close friend. “He was very insistent that everybody in the group not just learn how to operate the RF systems and do the RF physics but that we all became machine operators and we were all responsible for various diagnostics on the machine. The idea was we would totally understand tokamak physics and what our experiments were doing,” Wilson recalled. “I’m so grateful for that training I got under him.”
Engineer Robert Ellis said Hosea was very good about encouraging those working with him to take on new roles and advance in their field. “Joel had extremely high technical standards and if you could satisfy those standards you got along well with him,” he said.
After PLT, Hosea became involved in RF research on PPPL’s Tokamak Fusion Test Reactor (TFTR). He became head of a group studying RF waves on TFTR in 1987 and managed the development and installation of RF antennas by PPPL and Oak Ridge National Laboratory to study fast RF waves. In 1991, he became head of TFTR Tokamak Operations for deuterium-tritium and pioneered the use of the fast waves in heating D-T plasmas. TFTR produced a world record 6.3 million watts of fusion power with a 50-50 mixture of deuterium and tritium in 1993.
“His understanding of all aspects of the tokamak plus the new knowledge he gained about tritium operation led to very smooth productive operation of the machine,” said retired physicist Kenneth Young, another colleague of Hosea’s. “Later on, he often talked of serious challenges that he, and his team, had overcome for the D-T operation, but these were never apparent for the rest of us working on the experiments.”
In 1997, Hosea was appointed head of experiments under PPPL Director Rob Goldston. He later became involved with RF research on the National Spherical Torus Experiment (NSTX) and eventually headed the RF group for NSTX. His research on NSTX focused on understanding the edge of the plasma in the so-called scrape off layer. He continued that research until his death.
Hosea collaborated on RF research nationally and internationally on the C-Mod experiment at MIT, DIII-D at General Atomics, the Experimental Advanced Superconducting Tokamak (EAST) in China and the Korea Superconducting Tokamak Advanced Research (KSTAR) experiment. Collaborators at KSTAR recently sent Hosea a plaque for his contributions since he was unable to attend a recent conference.
Hosea was cited in 325 articles on ResearchGate but often chose to let younger collaborators be listed as first authors, Wilson said. He was a fellow of the American Physical Society and a co-inventor on three patents: a 1971 invention of a diagnostic that uses sound waves to analyze plasma, and two inventions intended for plasma experiments: a 1986 invention with PPPL physicist Samuel Cohen and others of a limiter to confine plasma; and a 1989 invention with physicist David Hwang, of the University of California, Davis, of an RF Faraday-thermal shield and plasma limiter.
Hosea was devoted to his work and his family and he continued to come in to work at PPPL almost daily after he retired. He joked that the only difference between his work before and after retirement was that he didn’t have to attend meetings after he retired. As Ellis puts it, “He was still a creative force right to the end.”
He is survived by his wife, Kathy, and three grown children: Devon, Christopher, and Stephanie, as well as several grandchildren. The family plans to hold a memorial service at a later date.
PPPL, on Princeton University's Forrestal Campus in Plainsboro, N.J., is devoted to creating new knowledge about the physics of plasmas — ultra-hot, charged gases — and to developing practical solutions for the creation of fusion energy. The Laboratory is managed by the University for the U.S. Department of Energy’s Office of Science, which is the largest single supporter of basic research in the physical sciences in the United States, and is working to address some of the most pressing challenges of our time. For more information, please visit science.energy.gov.
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