mounting of the device

Dr. Matthias Rossbach and his team of the Institute of Energy and Climate Research, IEK-6, Nuclear Waste Management and Reactor Safety of the Forschungszentrum Jülich GmbH designed and constructed a new instrument for prompt and delayed fission neutron induced reaction Gamma spectrometry.

They installed and tested the instrument together with the local support team at the SR10 channel of the FRM II. With the help of this new device, Rossbach and his team intend to produce a complete data catalogue of inelastic scattering reactions for elements and actinides. This information is particularly important when hazardous materials need to be investigated non-destructively, e.g., in safeguards applications or for nuclear waste processing and storage purposes. Additionally, some of the reactions will produce radioactive isotopes that can be measured with high sensitivity after irradiation at a close-to-detector position to extract production probabilities and other nuclear-physical properties.

The fission neutron beam created at a 93 % enriched ²³⁵U converter plate of 15 × 15 cm² effective area in immediate vicinity of the tip of the beam tube delivers unmoderated fission neutrons of 2.3•10⁸ cm^-2s^-1 (with 6 cm PB filter) to the MEDAPP experimental bunker where the new FaNGaS instrument is located. Two adjacent collimators in the beam channel confine the beam to 5 cm diameter and irradiate elemental or isotopic samples in front of a heavily shielded 50 % eff. HPGe detector. The shielding consists of 15 cm of lead, 1 cm of boron carbide and 40 cm of polyethylene to reduce scattered fast neutrons and gamma rays producing background in the detector. The present system allows taking spectra with sufficient sensitivity to determine systematically prompt gamma signals from (n,n’), (n,p) and in some cases also (n,2n) reactions.

FaNGaS has been set-up under a BMBF contract (02 S 9052A) “Bestimmung und Validierung nuklearer Daten von Actiniden zur zerstörungsfreien Spaltstoffanalyse in Abfallproben durch prompte Gamma Neutronenaktivierungsanalyse (PGAA-Actinide)” in close cooperation with the PGAA, MEDAPP and NECTAR of the MLZ.