With neutron beam intensities of ∼10 5–10 6 n/s, one must use large solid angles for the detectors or long observation times or both to obtain statistically meaningful data. The macro pulses had a repetition rate of 100 Hz. The proton beam consists of a 625 us macro pulse containing about 340 micro pulses of width 250 ps that are spaced 1.8 us apart. The proton beam is pulsed allowing one to measure the time of flight (energy) of the neutrons arriving at the experimental area. The fast neutron beam intensities were ∼10 5–10 6/s for E n = 2–100 MeV. The experiment was located on the 15R beam line (15° right with respect to the proton beam). “White spectrum” neutron beams were generated from an unmoderated tungsten spallation source using the 800 MeV proton beam from the LANSCE linear accelerator. The experiments were carried out at the Weapons Neutron Research Facility (WNR) at the Los Alamos Neutron Science Center (LANSCE) at the Los Alamos National Laboratory (LANL). The preparation of the targets and their characterization are described in. Typical actinide thicknesses are 100 ug/cm 2. The actinide fluorides are vapor deposited onto thin carbon foils. Actinide oxides are converted to actinide fluorides in a dual glove box system. Vapor deposition avoids the presence of impurities in the target. have suggested a simple parameterization of the TKE release in the low energy and spontaneous fission of actinide nuclei in the form:Īll the targets used in this work were made by vapor deposition. Among the list of such articles that influenced the author are, and. įrom time to time there are important review articles on fission that influence the development of the field. Pomorski, “Theory of Nuclear Fission” Springer, (2011). Wagemans, “The Nuclear Fission Process”, CRC Press (1991), and H.J. Huizenga “Nuclear Fission” Academic Press (1974), C. There are many books that describe the fission process. Because of this fact, it is important to understand the TKE release for its practical importance and the information gained about large scale nuclear collective motions. Most of the energy released in the fission of actinide nuclei appears in the form of the total kinetic energy (TKE) of the fragments. The GEF model predictions agree with the data in general as do the CGMF model predictions. The constant position of the heavy mass peak is interpreted as being due to the influence of the N = 88 and Z = 50 shells. In the case of 233U and 235U, our measurements agree with prior work. ![]() The TKE distributions were Gaussian in shape and their mean value as a function of incoming neutron energy could be fitted with second order polynomials. Corrections were made to the data for pulse height defect and the fragment energy loss in the target and its backing. The actinide targets were made by vapor deposition leading to high-quality targets, that were thin and uniform with reduced impurities. The fission fragments were detected using Si PIN diode detectors, giving us the fragment energies. The neutron energies were deduced from time-of- flight measurements. The total kinetic energy release and fission mass distributions for the fast neutron (E n = 3–100 MeV) induced fission of 232Th, 233U, 235U, 237Np, 239Pu, 240Pu, and 242Pu have been measured using the LANSCE facility. Chemistry Department, Oregon State University, Corvallis, OR, United States.
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