Search

A position-sensitive, high-resolution time-of-flight detector for fission fragments has been developed. The SPectrometer for Ion DEterminiation in fission Research (SPIDER) is a $2E-2v$ spectrometer designed to measure the mass of light fission fragments to a single mass unit. The time pick-off detector pairs to be used in SPIDER have been tested with $\alpha$-particles from $^{229}$Th and its decay chain and $\alpha$-particles and spontaneous fission fragments from $^{252}$Cf. Each detector module is comprised of a thin electron conversion foil, electrostatic mirror, microchannel plates, and delay-line anodes. Particle trajectories on the order of 700 mm are determined accurately to within 0.7 mm. Flight times on the order of 70 ns were measured with 200 ps resolution FWHM. Computed particle velocities are accurate to within 0.06 mm/ns corresponding to precision of 0.5%. An ionization chamber capable of 400 keV energy resolution coupled with the velocity measurements described here will pave the way for modestly efficient measurements of light fission fragments with unit mass resolution., Comment: 15 pages 6 figures

A digital data acquisition system has been combined with a double Frisch gridded ionization chamber for use at both moderated and unmoderated neutron sources at the Los Alamos Neutron Science (LANSCE) facility. The high efficiency of the instrument combined with intense LANSCE beams and new acquisition system permits fission output measurements across 11 orders of magnitude incident neutron energy. The acquisition and analysis system is presented along with the first in-beam performance tests of the setup.

The average Total Kinetic Energy (TKE ) release and fission-fragment yields in neutron-induced fission of 235 U and 238 U was measured using a Frisch-gridded ionization chamber. These observables are important nuclear data quantites that are relevant to applications and for informing the next generation of fission models. The measurements were performed a the Los Alamos Neutron Science Center and cover E n = 200 keV – 30 MeV. The double-energy (2E) method was used to determine the fission-fragment yields and two methods of correcting for prompt-neutron emission were explored. The results of this study are correlated mass and TKE data.

The average total kinetic energy $(\overline{TKE})$ in $^{239}\mathrm{Pu}(n,f)$ has been measured for incident neutron energies between 0.5 and 50 MeV. The experiment was performed at the Los Alamos Neutron Science Center (LANSCE) using the neutron time-of-flight technique, and the kinetic energy of fission fragments post-neutron emission was measured in a double Frisch-gridded ionization chamber. This represents the first experimental study of the energy dependence of $\overline{TKE}$ in $^{239}\mathrm{Pu}$ above neutron energies of 6 MeV.

The ionization chamber component of the SPIDER detector has been designed to measure energy loss and kinetic energy of fragments produced through neutron-induced fission with energy resolutions of