About Target 4 Flight Path 60R

Instrument Specifications

GErmanium Array for Neutron Induced Excitations (GEANIE) is the first large-scale, escape-suppressed, high-resolution gamma-ray spectrometer to be used at a white neutron source. It is now installed at the WNR high-energy neutron facility at LANSCE. The operation and upgrade of GEANIE is a joint project of the Lawrence Livermore and Los Alamos National Laboratories, funded primarily by the Stockpile Stewardship program of the NNSA.

The GEANIE Array

GEANIE currently consists of 26 high-resolution Ge detectors surrounded by BGO escape-suppression shields. Depending upon the experiment, roughly half of the Ge detectors used are of planar geometry for excellent resolution at low gamma-ray energies, and the others are coaxial for greater efficiency at higher gamma-ray energies. This instrument covers the gamma-ray energy range from below 20 keV to over 8 MeV. The array is located on a 20 meter flight path where neutrons are available with continuous energy coverage from below 1 MeV to over 200 MeV. Neutron time-of-flight is used to determine incident neutron energies.

Research is conducted by teams of national laboratory staff with collaborators from universities and other institutions. Current efforts are focused mainly on (n,xn) reaction measurements and fission studies. Neutrons provide a unique probe for nuclear structure investigations allowing studies in heavier nuclei than are possible with charged particles, and complementing studies with heavy-ions by populating states with low to intermediate spins. Experiments addressing nuclear spectroscopy, nuclear reactions, and nuclear structure in previously inaccessible regions of excitation are in progress.

A sample γ-ray spectrum from n + 136Xe

GEANIE measurement of the cross section of the 239Pu(n,2n)238Pu reaction