Memoir of James R. Wilson

James R. Wilson

I came to the Lawrence Laboratory in the spring of 1953. I started working with John Foster. His assignment was to make a nuclear explosive that was different from Los Alamos designs. The first computer program that I wrote was designed to calculate the initiation probability of the super critical configuration of plutonium per injected neutron. This probability was very important for our first nuclear explosive test. The test was very successful.

The next computation project that I developed was a program that solved the Boltzmann equation for neutrons in a bomb, for axial systems. By that time, around 1958, computer programs were written on punched cards. The cards for the above program filled a large filing cabinet of several cubic feet. Back then when a large program involved thousands of punched cards it behooved one to be extra careful when errors were removed. In later years after user friendly computer systems were incorporated at the Laboratory the ease of debugging a program greatly increased, but we also increased the program´┐Żs complexity so there was much more to debug. Over the years it has continued to be true that debugging is both an Art Form and a Science.

The next computer problem I attacked was the development of a two dimensional magneto-hyrodynamical program. We had started work on chemical explosive driven electrical generators. That application died out, but a decade or so later I used the program to study the collapse of a magnetized rotating star. The result of the calculation was the production of a very energetic pair of axial jets. That program has had many workers involved and it is still an active Laboratory design tool.

Another early computer project was the development of a code that solved the Boltzmann equation in spherical geometry for the time evolution of the photon distribution in space angle and energy. Later this program was extended to treat non thermal atomic equilibrium for atoms.

At the time people did not want to use such a detailed calculation of photonic evolution. I was in B division and we were quite detached from the Laboratory theoretical division. T Division supported A Division. We were much more free to develop new computing methods. Project managers were most often reluctant to have the computer programs that they used for their engineering design studies changed even if it meant improved calculations. Later I applied my computer experience to the development of astrophysical oriented calculations. Today, I am working on a computer program designed to follow the evolution of an inhomogeneous cosmos.

During all these years it has remained true that being able to do research with the aid of computers has resulted in an astonishing improvement in our understanding of science, and the world around us.

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