Benjamin Abeles (1925–2020): The Architect of Deep Space Power
Benjamin Abeles was a physicist whose work literally illuminated the farthest reaches of our solar system. A survivor of the Holocaust and a pioneer of materials science, Abeles is best known for developing the germanium-silicon (Ge-Si) alloys that power Radioisotope Thermoelectric Generators (RTGs). These devices have provided the steady, long-lived electrical power required for NASA’s most ambitious missions, including the Voyager probes, the Cassini mission to Saturn, and the New Horizons mission to Pluto.
1. Biography: From the Kindertransport to the Frontiers of Science
Benjamin Abeles was born on June 23, 1925, in Vienna, Austria, and raised in Prague, Czechoslovakia. His life was early defined by the upheaval of World War II. In 1939, at the age of 14, he was one of the many Jewish children saved by the Kindertransport, which brought him to the United Kingdom just months before the outbreak of war. His parents and sister, who remained behind, were murdered by the Nazi regime.
In the UK, Abeles worked as a waiter and later served as a mechanic in the Royal Air Force (RAF) No. 311 (Czechoslovak) Bomber Squadron. After the war, he returned to Prague to study at Charles University, but following the communist coup in 1948, he moved to Israel. He completed his undergraduate studies and earned his Ph.D. in Physics from the Hebrew University of Jerusalem in 1955.
In 1956, Abeles immigrated to the United States, beginning a prolific career in industrial research. He spent over two decades at RCA Laboratories (the David Sarnoff Research Center) in Princeton, New Jersey, before joining Exxon Research and Engineering in 1979. He remained active in the scientific community well into his 90s, eventually moving back to the UK, where he passed away in Leicester on December 14, 2020.
2. Major Contributions: Thermoelectrics and Granular Metals
Abeles’s scientific output was characterized by a transition from fundamental solid-state physics to highly practical material engineering.
The Silicon-Germanium (SiGe) Alloy
Abeles’s most significant contribution was the discovery and optimization of germanium-silicon alloys for thermoelectric power generation. Along with his colleague George D. Cody, Abeles demonstrated that by alloying silicon and germanium, one could significantly reduce thermal conductivity without a proportional decrease in electrical conductivity. This "phonon-glass, electron-crystal" behavior allowed for a high "figure of merit" ($ZT$), making the material exceptionally efficient at converting heat into electricity at high temperatures.
Granular Metals and Discontinuous Films
While at RCA and Exxon, Abeles conducted foundational research into "granular metals"—composites consisting of tiny metallic grains embedded in an insulating matrix. He developed the theoretical framework for "hopping conduction," explaining how electrons tunnel between these isolated metallic islands. This work remains a cornerstone of mesoscopic physics and the study of disordered systems.
Superconductivity and Thin Films
Abeles also made significant strides in the study of superconductivity in thin films. He investigated the "proximity effect," where a superconductor influences the properties of a neighboring normal metal, contributing to the understanding of how dimensionality affects phase transitions in materials.
3. Notable Publications
Abeles authored or co-authored over 100 scientific papers. Some of his most influential works include:
- "Thermal Conductivity of Ge-Si Alloys" (1962, Physical Review): This seminal paper detailed the lattice thermal conductivity of these alloys, providing the theoretical basis for their use in space power.
- "Lattice Thermal Conductivity of Disordered Semiconductor Alloys at High Temperatures" (1963, Physical Review): A deeper dive into the physics of phonon scattering in alloys.
- "Electron Localization in Granular Metals" (1975, Physical Review Letters): Co-authored with P. Sheng and B. Coutts, this paper is a highly cited exploration of the transition from metallic to insulating behavior in composite materials.
- "Applied Physics of Granular Metals" (1976, Applied Physics): A comprehensive review that bridged the gap between basic theory and industrial application.
4. Awards & Recognition
- Stuart Ballantine Medal (1979): Awarded by the Franklin Institute for his work on thermoelectric materials (specifically the Ge-Si alloy).
- David Sarnoff Award: RCA’s highest technical honor, recognizing his role in the development of space power systems.
- Fellow of the American Physical Society (APS): Elected for his contributions to the understanding of transport properties in solids.
- Induction into the New Jersey Inventors Hall of Fame: Recognizing the local and global impact of his research at RCA and Exxon.
5. Impact & Legacy: Powering the Stars
The legacy of Benjamin Abeles is currently floating billions of miles away from Earth. The RTGs utilizing his SiGe alloys have proven to be among the most reliable machines ever built.
- The Voyager Probes: Launched in 1977, Voyager 1 and 2 are still communicating with Earth 46 years later, powered by the SiGe thermoelectrics Abeles helped develop.
- Deep Space Exploration: Because solar power is ineffective beyond Mars, the Ge-Si RTG became the standard for NASA missions to the outer planets, including Galileo (Jupiter) and Cassini (Saturn).
- Materials Science: His work on granular metals laid the groundwork for modern nanotechnology and the study of nanocomposites, influencing how we design materials for sensors and electronics today.
6. Collaborations
Abeles was a collaborative researcher who thrived in the industrial laboratory environment:
- George D. Cody: His primary collaborator at RCA. Together, they solved the material challenges of high-temperature thermoelectrics.
- Ping Sheng: A key collaborator at Exxon who worked with Abeles on the complex physics of granular materials and wave propagation in disordered media.
- S. Meiboom: Early in his career, he worked with Meiboom on the magnetoresistance of germanium, which helped establish his reputation in semiconductor physics.
7. Lesser-Known Facts
- A "Quiet" Revolutionary: Despite his work being essential to the "Space Race," Abeles was known for his humility and soft-spoken nature. He rarely sought the spotlight, preferring the laboratory to the podium.
- The RAF Mechanic: His time as a mechanic in the RAF during WWII likely influenced his later ability to bridge the gap between abstract physics and mechanical reliability.
- Centenarian Proximity: Abeles lived to be 95, remaining intellectually curious and engaged with the physics community until his final years.
- Artistic Connection: His wife, Ann Abeles, was also a scientist (a microbiologist), and together they were active supporters of the arts and sciences in Princeton for decades.
Benjamin Abeles represents the pinnacle of the 20th-century immigrant scientist: a man who escaped the darkest chapters of history to provide the light that allowed humanity to see across the solar system.