FERMIAC
The FERMIAC is a mechanical analog computer that can display the propagation of neutron radiation using the Monte Carlo method . It was designed by Enrico Fermi in 1947 and built by LDP King of Los Alamos Scientific Laboratory . The original of the device is on display today at the Bradbury Science Museum, Los Alamos.
background
Rolling the dice using the Monte Carlo method has been greatly simplified by digital computing systems and was proposed by Stanislaw Ulam and John von Neumann to solve physical problems such as neutron diffusion and photon transport . In the second half of the 1940s, ENIAC was chosen for this purpose. This electronic calculating machine was not immediately available to the researchers in Los Alamos. Therefore, in the transition period of about two years, the FERMIAC was used to simplify the tedious and tedious simulations of the neutron flux.
construction
The device consists of a brass frame that can be moved on technical drawings using four wheels. Two measuring wheels record the distances covered on the paper, with which the cumulative flight time or the distance traveled by free neutrons that start either as thermal (0.0253 eV) or fast neutrons (2 MeV) is simulated. A pen can be used on a plexiglass pane with pre-marked angles and simulated scattering effects or the direction of new neutrons after a nuclear fission.
use
The transmission ratio of the measuring wheels is set according to the material constants used for the components to be examined. According to the Monte Carlo principle, random numbers are drawn that determine the direction and distance of the neutron movement. Arrived at the end of the movement step, another random number indicates which process follows, such as e.g. B. elastic or inelastic collision , nuclear fission or absorption . Usually at least 100 neutrons and their subsequent neutrons are drawn in a sectional drawing, for example to examine the neutron distribution in a fuel assembly .
Individual evidence
- ↑ What is the FERMIAC or Fermi Trolley? In: Bradbury Science Museum. Los Alamos National Laboratory, July 31, 2017, accessed April 21, 2020 .
- ^ Roger Eckhardt: Stan Ulam, John von Neumann and the Monte Carlo Method. In: Los Alamos Science, Special Issue, Stanislaw Ulam 1909-1984. Los Alamos National Laboratory, 1987, accessed April 21, 2020 .
- ↑ Fabrizio Coccetti: FERMIAC or Fermi's Trolley? Società Italiana di Fisica, September 28, 2015, accessed April 21, 2020 .