Julius Ashkin

Ashkin died at Montefiore Hospital in Pittsburgh, Pennslylvania on June 4, 1982 after a lengthy illness.

In 1958–1959 Ashkin won a Ford Foundation grant to spend a sabbatical year in Geneva, Switzerland, at CERN, the European Organization for Nuclear Research. There, he became a member of the first group of scientists to use that institution's new 600 MeV synchrocyclotron. Using this particle accelerator he helped to make a significant discovery which confirmed an aspect of the V-A Theory of weak interactions. Supported by a grant from the Guggenheim Foundation, in 1968 he also spent a year as a Fellow at All Souls College, Oxford.

In 1953, with Bethe, his former director of theoretical work in Los Alamos, Ashkin published an article closely related to the work they had then done. This article, "Passage of Radiations Through Matter," summarized the effects of particles and radiation as they passed through solids. In time it became a standard reference for physics experimenters. Using the CIT cyclotron and following on work done by Bethe and Robert E. Marshak, Ashkin conducted experiments to determine the characteristics of a short-lived particle — the pi-meson or pion — that is produced when high energy cosmic ray protons and other cosmic ray components interact with matter in the Earth's atmosphere. Ashkin served as chair of the physics department between 1961 and 1972. After he died, CMU created the Julius Ashkin Teaching Award in his honor.

In 1950 it was revealed that one of the scientists at Los Alamos, Klaus Fuchs, was providing the Soviet intelligence bureau, NKGB, with secret information about bomb research. Between 1943 and 1946, Fuchs worked at both Columbia and Los Alamos. When the FBI interviewed Bethe and Feynman about their relationship with Fuchs while at Los Alamos, Feynman said Fuchs was quiet, reserved and not inclined to mix with other scientists outside of work. He also said he believed Fuchs was less stand-offish with Ashkin and seemed friendly with him.

In 1950 Ashkin joined the physics faculty of Carnegie Mellon University (then the Carnegie Institute of Technology) where Edward Creutz was department head and director of a new 450 MeV proton synchrocyclotron that CIT had built in nearby Saxonburg, Pennsylvania. Joining fellow scientists Lincoln Wolfenstein and Sergio de Benedetti, at this time Ashkin began to transition from mainly theoretical to mainly experimental work. The cyclotron remained in use at the Saxonburg Nuclear Research Center until the mid-1970s when it was dismantled and, using it, Ashkin was able to produce some of his best-known experimental results.

While at Rochester, Ashkin was the first scientist to formally recognize the importance of the Feynman diagram. Feynman devised the diagram in 1948 to provide a simple visualization of the mathematical expressions governing the behavior of subatomic particles. Although the diagram and its offshoots were later seen as extremely important tools, Feynman did not give them a theoretical framework nor did he explain how he proposed they be used. Physicists had difficulty in understanding their function, distrusted their simplicity, and were reluctant to give them formal recognition. Feynman later said physicists did not realize the diagram's power and would employ a more complex method created by Julian Schwinger. Ashkin, he said, was the first to break with this pattern: "They somehow or other couldn’t do it. They had to go through this [the Schwinger method] to believe it. But that's all right. The only person who didn't, the first paper where it was used directly — which I kept looking for, I kept flipping through the Physical Review as it came out — was Ashkin. He'd done some calculation for some experiment, and he said, 'We’ve calculated this using Feynman's rules.' Bloop! There it was in writing! Then gradually more and more people did it."

Along with other members of the Feynman team, Ashkin produced technical reports while at Los Alamos. These were classified at the time but have since been made public. One example gives an idea of the work carried out by the group. It is The Calculation of Critical Masses Including the Effects of the Distribution of Neutron Energies, by Feynman, R.P.; Welton, T.A.; Ashkin, J.; Ehrlich, R.; Peshkin, M.; and Reines, F. Report LA-524(Del.) January 21, 1947 (extract from abstract: "Convenient approximate methods are developed for the calculation of critical sizes and multiplication rates of spherical, active cores surrounded by infinite tampers. Special attention is given to those problems arising from the fact that neutrons of different velocities have different properties. The methods consist essentially of approximating the neutron densities at each velocity by fundamental mode shapes for each velocity.")

In 1946, before the scientists at Los Alamos dispersed, there was a brief period during which they gave lectures on subjects in which they had expertise. The program was styled the "Los Alamos University" and some junior members of laboratory personnel received college credit for attending them. Ashkin's were on theoretical mechanics. The course description says it covered the dynamics of particles, rigid bodies, elastic media, and fluids using vector analysis, particle dynamics, Lagrange's equations, and Hamilton's equations.

On leaving Los Alamos in 1946 Ashkin obtained a position as assistant professor at the University of Rochester and in 1950 he moved to the Carnegie Institute of Technology (later Carnegie Mellon University). He remained at CMU for the rest of his life, serving as professor and for a period head of the physics department. Robert Marshak brought Ashkin to the University of Rochester in 1946. As an assistant professor he taught mechanics and thermodynamics and theoretical physics and performed pioneering experiments on neutron-proton, proton-proton, and nucleon-nucleon scattering.

On July 16, 1945 Ashkin was present at the first-ever explosion of a nuclear bomb at the Trinity test site, Alamogordo. Only a few of the many scientists were permitted to witness this unspeakably dramatic culmination of their work. Ashkin was probably there because of his work on radiation poisoning, begun at Met Lab and probably continued afterward.

At Los Alamos Ashkin was assigned to work in the Theoretical Division headed by Bethe. There were five groups in this division and Ashkin was assigned to group 4, Diffusion Problems. His responsibilities, broadly, permitted him to build upon work he had done as a graduate student and in his months at Met Lab. T-4's group leader was Richard Feynman; Ashkin was alternate leader. The initial members were Richard Ehrich, and Frederick Reines. Theodore Welton [de] joined it in the early spring of 1944. The group's main task was to estimate the rate at which neutrons would diffuse through the explosive core of the bomb during nuclear fission. Somewhat facetiously Feynman later claimed that the work done at Los Alamos was mostly engineering, not science. Welton, however, told of the group's long hard hours, high spirits and cohesiveness, and said they achieved some excellent successes in theoretical physics. Their work required a great number of mathematical computations, which, Welton remembered, they performed using Work Projects Administration math tables and big Marchant mechanical calculators. In fact, their assistant, an enlisted man named Murray Peshkin, remembered the group as having an unending need for calculation. An undergraduate with a major in physics at the time he was recruited, he was put, as he recalled, "to solving differential equations that were needed to predict the critical mass of a bomb under various assumptions about the many unknown properties of the nuclei in the bomb material."

As an undergraduate, Ashkin was invited to join an honorary mathematics society, and received awards. He entered the fall semester as an assistant lecturer and began work toward a master's degree. A year later, having received that degree, he began work toward a Ph.D. under the supervision of Willis Lamb. As a graduate student, Ashkin contributed to one paper in astrophysics. and two papers in statistical mechanics He collaborated with Lamb in writing the first of the two papers on statistical mechanics and with Teller in writing the second. This second paper, "Statistics of Two-Dimensional Lattices with Four Components" has since been frequently cited. He received his Ph.D. in Physics in 1943.

During the latter part of 1942, before completing his Ph.D. work, Ashkin accepted an offer to work in the Manhattan Project. Early work on the development of the atom bomb had taken place at Columbia during the six years Ashkin was an undergraduate and graduate student there. When the process of nuclear fission was discovered in 1938, scientists in many locations in Europe and the United States began intense work to understand and control the phenomenon. Researchers at Columbia and nearby Princeton University were in the forefront of this work. There's no information on how much, if at all, Ashkin was involved in the effort at this early stage of his career, but it is certain that the Columbia physics department was the workplace for scientists who were devoted to the secret development of a new and phenomenally powerful weapon. These men included men already mentioned — Fermi, Rabi, Teller, and Bethe — as well as Leó Szilárd (who worked with Fermi to demonstrate that a nuclear reaction was possible), Herbert L. Anderson (then, like Ashkin, a Columbia graduate student), John R. Dunning (an associate professor at Columbia who had built a small cyclotron in the mid-1930s), Walter Zinn (a Columbia professor who worked with the Columbia cyclotron to demonstrate the possibility of a sustained chain reaction), George B. Pegram (Dean of Columbia's Faculties of Political Science, Philosophy, and Pure Science, who helped bring Fermi to the United States and brought him together with representatives of the U.S. Navy Department for the first discussion of the atomic bomb) and Harold Urey (associate professor of Chemistry whose work on separation of isotopes resulted in the discovery of deuterium). In addition, Columbia received visits from scientists at Princeton University who were coordinating their work with Columbia colleagues. These included John Wheeler, Edward Creutz, and Robert R. Wilson.

When Ashkin accepted an invitation to join the Manhattan Project he was still working on his Ph.D. He spent the last few months of 1942 at the Metallurgical Laboratory at the University of Chicago and then worked at the Los Alamos Laboratory from mid-1943 to mid-1945. The scientists at the Metallurgical Laboratory, or Met Lab as it was called, used a nuclear reactor called the Chicago Pile to produce the world's first controlled chain reaction. They built the reactor in a disused squash court under the bleachers of Stagg Field, the university's old football stadium. They had been brought together from Columbia and Princeton by Arthur Compton who was a professor of physics at the University of Chicago. The Met Lab consisted of two divisions. Fermi, Anderson, Zinn, Creutz, and Szilard were key members of the physics division; Bethe and Teller of the theoretical division.

Ashkin attended Brooklyn's James Madison High School, graduating in 1936, while still a few weeks shy of his 16th birthday. In his senior year, he received honors and awards. He was awarded a scholarship to attend Columbia University, where he studied four years as an undergraduate from 1936 to 1940, and three as a graduate from 1940 to 1943.

Julius Ashkin (August 23, 1920 – June 4, 1982) was a leader in experimental and theoretical physics known for furthering the evolution of particle physics from nuclear physics. As a theoretical physicist he made contributions in the fields of statistical mechanics, solid state physics, nuclear physics, and elementary particle physics. As an experimental physicist his main contributions concerned the passage of certain particles (pi-mesons, or pions) through solid matter and their subsequent decay. He was recognized for the quality of his research and teaching.

Julius Ashkin was born in Brooklyn, New York, on August 23, 1920. His parents were Isadore and Anna Ashkin. He had two younger siblings, a brother, Arthur, also a physicist, and a sister, Ruth. One older sibling, Gertrude, died while young. The family home was in Brooklyn, New York, at 983 E 27 Street. Isadore had immigrated to the United States from Odessa, Ukraine at the age of 19. Anna, five years younger, also came from the Ukraine (in her case Galicia). Within a decade of his landing in New York, Isadore had become a U.S. citizen and was running a dental laboratory at 139 Delancey Street in Manhattan. Ashkin's nickname was Julie. He is the uncle of the artist Michael Ashkin.