UNM Fission Fragment Spectrometer for Improved Nuclear Data
Start Date
8-11-2017 8:30 AM
End Date
8-11-2017 12:30 PM
Abstract
Fission cross section and product yields are important for active interrogation, understanding secondary reactor heating, nuclear forensics and for furthering theory on fission preformation conditions. To reduce the uncertainty while determining material compositions using delayed signals that are produced in active interrogation, it is required to have a better understanding of the fission product yield over a range of neutron energies and actinide targets. Less uncertainty allows for higher fidelity simulations which are important for understanding minimum detectable limits. Rather than determining the presence of special nuclear material directly, improved fission fragment data provides information useful for identifying the interrogated actinide through the delayed gamma-ray and neutron signatures. Very little data exists on fragment distributions on neutron energies outside of the thermal (0.025 eV) and fusion (~14 MeV) neutron energy regions. The first iteration of the UNM Fission Product Spectrometer, to measure this data, has been tested at the LANL-LANSCE neutron source on the low energy (~0.025 eV – 1 keV) neutron beamline. The spectrometer consists of a heavy ion time-of- flight (TOF) module followed by an ionization chamber (IC), for velocity and KE measurements, respectively, of the ejected fission products. These particle-by-particle measurements are used to derive the masses of the fission products. The IC also provides a range evaluation by the addition of an “active cathode” timing to measure heavy ion penetration depth into the IC gas for determination of the proton number. The LANSCE facility is able to produce a range of incident neutron for a range of actinide targets relevant to nonproliferation. This work is in parallel with a LANL project to develop a high efficiency spectrometer, SPIDER, to run on the LANSCE high energy neutron beamlines.
UNM Fission Fragment Spectrometer for Improved Nuclear Data
Fission cross section and product yields are important for active interrogation, understanding secondary reactor heating, nuclear forensics and for furthering theory on fission preformation conditions. To reduce the uncertainty while determining material compositions using delayed signals that are produced in active interrogation, it is required to have a better understanding of the fission product yield over a range of neutron energies and actinide targets. Less uncertainty allows for higher fidelity simulations which are important for understanding minimum detectable limits. Rather than determining the presence of special nuclear material directly, improved fission fragment data provides information useful for identifying the interrogated actinide through the delayed gamma-ray and neutron signatures. Very little data exists on fragment distributions on neutron energies outside of the thermal (0.025 eV) and fusion (~14 MeV) neutron energy regions. The first iteration of the UNM Fission Product Spectrometer, to measure this data, has been tested at the LANL-LANSCE neutron source on the low energy (~0.025 eV – 1 keV) neutron beamline. The spectrometer consists of a heavy ion time-of- flight (TOF) module followed by an ionization chamber (IC), for velocity and KE measurements, respectively, of the ejected fission products. These particle-by-particle measurements are used to derive the masses of the fission products. The IC also provides a range evaluation by the addition of an “active cathode” timing to measure heavy ion penetration depth into the IC gas for determination of the proton number. The LANSCE facility is able to produce a range of incident neutron for a range of actinide targets relevant to nonproliferation. This work is in parallel with a LANL project to develop a high efficiency spectrometer, SPIDER, to run on the LANSCE high energy neutron beamlines.
