Performance evaluation of an energy tuning assembly for neutron spectral shaping

Journal Article · 21 January 2019 · Nuclear Instruments and Methods in Physics Research. Section A, Accelerators, Spectrometers, Detectors and Associated Equipment

DOI: https://doi.org/10.1016/j.nima.2019.01.049 · OSTI ID:1513143

Bevins, James E. ^[1]; Sweger, Z. ^[2]; Munshi, N. ^[2]; Goldblum, B. L. ^[3]; Brown, J. A. ^[3]; Bleuel, D. L. ^[4]; Bernstein, L. A. ^[3]; Slaybaugh, R. N. ^[3]

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1. Air Force Inst. of Technology, Wright Patterson AFB, OH (United States). Dept. of Engineering Physics
2. Univ. of California, Berkeley, CA (United States). Dept. of Physics
3. Univ. of California, Berkeley, CA (United States). Dept. of Nuclear Engineering
4. Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)

An energy tuning assembly (ETA) was designed here to be fielded at the National Ignition Facility (NIF) to modify the characteristic D-T fusion spectrum to include a prompt fission neutron spectral component. The ETA was characterized at the 88-Inch Cyclotron at Lawrence Berkeley National Laboratory to measure the shaped spectrum from an incident deuteron breakup neutron source, test the proposed neutron spectroscopy techniques used to inform the flux measurements at NIF, and validate the ability to predict ETA performance using a Monte Carlo Neutral Particle (MCNP) simulation. Activation foils (i.e., Ni, In, Au, Al) were exposed to a collimated 33-MeV deuteron-breakup beam originating from a tantalum breakup target. The source spectrum absent the ETA was characterized using a set of activation foils and the STAYSL unfolding code. Finally, the ETA-modified spectrum was obtained using activation foil unfolding with a $\frac{{\chi }^2}{\nu }=0.92$. The ETA-modified unfolded spectrum agreed with the MCNP-simulated prediction in the energy range of 0.1–14 MeV, but exhibited disagreements in the 10 eV–100 keV region. This work demonstrates shaping of the NIF neutron spectrum via the ETA to be a viable path forward for tailored neutron beams at NIF.

• Research Organization: Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); Univ. of California, Berkeley, CA (United States)
• Sponsoring Organization: National Science Foundation (NSF) (United States); USDOE; USDOE National Nuclear Security Administration (NNSA), Office of Defense Nuclear Nonproliferation (NA-20)
• Grant/Contract Number: AC02-05CH11231; AC52-07NA27344; NA0003180
• OSTI ID: 1513143
• Report Number(s): LLNL-JRNL--767547; 957398
• Journal Information: Nuclear Instruments and Methods in Physics Research. Section A, Accelerators, Spectrometers, Detectors and Associated Equipment, Journal Name: Nuclear Instruments and Methods in Physics Research. Section A, Accelerators, Spectrometers, Detectors and Associated Equipment Vol. 923; ISSN 0168-9002
• Publisher: ElsevierCopyright Statement
• Country of Publication: United States
• Language: English