Measurement of Fission Neutron Spectrum and Multiplicity using a Gamma Tag Double Time-of-flight Setup

Journal Article · Thu May 01 00:00:00 EDT 2014 · Nuclear Data Sheets

DOI:https://doi.org/10.1016/j.nds.2014.08.058· OSTI ID:1465740

Blain, E. ^[1]; Daskalakis, A. ^[1]; Danon, Y. ^[1]

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1. Rensselaer Polytechnic Inst., Troy, NY (United States)

Recent efforts have been made to improve the prompt fission neutron spectrum and nu-bar measurements for Uranium and Plutonium isotopes particularly in the keV region. A system has been designed at Rensselaer Polytechnic Institute (RPI) utilizing an array of EJ-301 liquid scintillators as well as lithium glass and plastic scintillators to experimentally determine these values. An array of BaF2 detectors was recently obtained from Oak Ridge National Laboratory to be used in conjunction with the neutron detectors. The system uses a novel gamma tagging method for fission which can offer an improvement over conventional fission chambers due to increased sample mass. A coincidence requirement on the gamma detectors from prompt fission gammas is used as the fission tag for the system as opposed to fission fragments in a conventional fission chamber. The system utilizes pulse digitization using Acqiris 8 bit digitizer boards which allow for gamma/neutron pulse height discrimination on the liquid scintillators during post processing. Additionally, a 252Cf fission chamber was designed and constructed at RPI which allowed for optimization and testing of the system without the need for an external neutron source. The characteristics of the gamma tagging method such as false detection rate and detection efficiency were determined using this fission chamber and verified using MCNP Polimi modeling. Prompt fission neutron spectrum data has been taken using the fission chamber focusing on the minimum detectable neutron energy for each of the various detectors. Plastic scintillators were found to offer a significant improvement over traditional liquid scintillators allowing energy measurements down to 50 keV. Background was also characterized for all detectors and will be discussed.

• Research Organization: Rensselaer Polytechnic Inst., Troy, NY (United States)
• Sponsoring Organization: USDOE National Nuclear Security Administration (NNSA)
• Grant/Contract Number: NA0001814
• OSTI ID: 1465740
• Journal Information: Nuclear Data Sheets, Vol. 119, Issue C; ISSN 0090-3752
• Publisher: Elsevier
• Country of Publication: United States
• Language: English

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