Lee A. Bernstein
· ProfessorVerifiedUniversity of California, Berkeley · Nuclear Engineering
Active 1993–2025
About
Lee A. Bernstein is the Nuclear Data Group Leader at Lawrence Berkeley National Laboratory (LBNL) and a professor in the UC-Berkeley Department of Nuclear Engineering. He leads the Bay Area Nuclear Data Group, which aims to meet the nuclear data needs of the applied and basic science and engineering community while training the next generation of nuclear scientists and engineers. Bernstein has over 25 years of experience in experimental nuclear physics, with a specialization in measuring low-energy nuclear properties and cross sections. He has led domestic and international experimental campaigns utilizing high-resolution charged-particle, neutron, and photon spectrometers to gather data sets ranging from gigabytes to terabytes. Prior to joining Berkeley in 2016, he was a staff scientist and group leader at Lawrence Livermore National Laboratory, where he contributed to the development of detectors for measuring properties of High Energy Density plasmas at the National Ignition Facility. Bernstein is a fellow of the American Physical Society, recognized for his work developing novel methods for determining neutron-nucleus cross sections via high-resolution gamma-ray spectroscopy, early development of the surrogate ratio method, and studying nuclear processes in high energy density plasmas. He teaches courses in nuclear physics and policy and has served as the principal academic advisor for 17 Ph.D. and M.S. students.
Research topics
- Physics
- Nuclear physics
- Engineering
- Computer Science
- Optics
- Thermodynamics
- Nuclear engineering
- Classical mechanics
- Materials science
- Electrical engineering
- Data science
- Philosophy
- Atomic physics
- Mechanics
Selected publications
In Memory of Dr. Richard B. Firestone
Nuclear Data Sheets · 2025-03-07
articleOpen accessCorrection to: Compound-Nuclear Reactions
Springer proceedings in physics · 2025-01-01
book-chapterOpen accessPhysical review. C · 2025-04-18 · 4 citations
articleOpen accessSenior authorImproved neutron inelastic scattering cross sections have repeatedly been identified as a top priority nuclear data need, important for basic science and a range of applications in nuclear energy, stockpile stewardship, and proliferation detection. For the <a:math xmlns:a="http://www.w3.org/1998/Math/MathML"><a:mmultiscripts><a:mi mathvariant="normal">C</a:mi><a:mprescripts/><a:none/><a:mn>12</a:mn></a:mmultiscripts></a:math>(<c:math xmlns:c="http://www.w3.org/1998/Math/MathML"><c:mrow><c:mi>n</c:mi><c:mo>,</c:mo><c:msup><c:mi>n</c:mi><c:mo>′</c:mo></c:msup><c:mi>γ</c:mi></c:mrow></c:math>) reaction in particular, recent measurements have unveiled some structural discrepancies, demonstrating incongruities among themselves and in relation to the ENDF/B-VIII.0 nuclear data evaluation. To help resolve these disagreements, a measurement was performed at the 88-Inch Cyclotron at Lawrence Berkeley National Laboratory using a broad-spectrum neutron beam and a 99.8% pure natural carbon target. The Gamma Energy Neutron Energy Spectrometer for Inelastic Scattering (GENESIS) was employed to measure energy-differential <d:math xmlns:d="http://www.w3.org/1998/Math/MathML"><d:mi>γ</d:mi></d:math>-ray emission spectra as a function of incident neutron energy in the energy range of 5.5 to 16.7 MeV. The <e:math xmlns:e="http://www.w3.org/1998/Math/MathML"><e:mmultiscripts><e:mi mathvariant="normal">C</e:mi><e:mprescripts/><e:none/><e:mn>12</e:mn></e:mmultiscripts></e:math> partial <g:math xmlns:g="http://www.w3.org/1998/Math/MathML"><g:mi>γ</g:mi></g:math>-ray cross sections were extracted at <h:math xmlns:h="http://www.w3.org/1998/Math/MathML"><h:msup><h:mn>63</h:mn><h:mo>∘</h:mo></h:msup><h:mo>,</h:mo><h:mo> </h:mo><h:mrow><h:mn>122</h:mn><h:mo>.</h:mo><h:msup><h:mn>5</h:mn><h:mo>∘</h:mo></h:msup></h:mrow></h:math>, and <i:math xmlns:i="http://www.w3.org/1998/Math/MathML"><i:msup><i:mn>150</i:mn><i:mo>∘</i:mo></i:msup></i:math> with respect to the incoming neutron beam and integrated using angular distribution data available in the literature. The data show agreement with a recent literature measurement and evaluation from 11 to 15 MeV, but indicate a larger cross section for incident neutron energies between 5.5 and 8.5 MeV. The measured relative angular distributions are also reported and were found to agree with evaluation.
Radiochimica Acta · 2025-03-12 · 2 citations
articleOpen accessAbstract A very brief overview of the hitherto investigated production routes of 86g Y is given, and a comparative analysis of its production via the two low-energy reactions, namely (p,n) and (d,2n) on 96.4 % enriched 86 Sr as target material, is presented. Based on our recent cross-section measurements, the calculated yields of 86g Y via the two reactions were compared, and the levels of co-produced isotopic impurities were estimated. At low-energy medical cyclotrons ( E p < 20 MeV; E d < 10 MeV) the use of the (p,n) reaction is superior, both in terms of the yield of 86g Y and the levels of radionuclidic impurities. At medium-sized cyclotrons, on the other hand, the (d,2n) reaction leads to higher yield of 86g Y, but the level of radionuclidic impurities is also higher. The method of choice for production of 86g Y thus remains the (p,n) reaction on enriched 86 Sr.
Journal of Applied Physics · 2025-06-16 · 2 citations
articleOpen accessNuclear fusion is an enticing alternative to current sources of energy, with multilayered Rare-Earth Barium Copper Oxide (REBCO) coated conductors deemed pivotal in the race toward fully realized, commercially viable, and magnetic confinement fusion reactors. In this study, we simulated the ion spectrum expected to evolve from REBCO's nickel-based Hastelloy C-276 substrate and copper stabilizer in an affordable robust compact-like reactor. We then emulated this gas production through helium implantation to investigate changes in materials and superconducting properties. Our results revealed that the substrate and stabilizer are capable of producing protons energetic enough to recoil throughout the tape thickness in appreciable doses, and alphas energetic enough to deposit 7.54 × 1014 ions/cm2 or 50.1 helium appm in the superconducting layer over a 30-year reactor lifetime. The superconducting layer of SuperPower® tapes exhibited at least double the swelling rate of the other major layers, and both SuperPower and Fujikura Ltd. tapes displayed microstructural changes in the REBCO layer not observed in isotropic metals. For the estimated lifetime fluence, the Fujikura tapes showed a ∼1 K reduction in critical temperature and a 32% degradation in critical current for compact reactor-relevant conditions (16 T, 20 K). Nuclear transmutation, low-temperature solder implantations, gas-ion evolution, the influence of gas production on vortex dynamics, and other related considerations are also discussed.
Deuteron-induced reactions on natural Zr from threshold to 50 MeV: production of <sup>86g</sup> Y
Radiochimica Acta · 2025-12-25
articleOpen accessAbstract Two stacks of thin Zr foils were irradiated with 30 and 50 MeV deuterons, respectively, using the Lawrence Berkeley National Laboratory 88-Inch Cyclotron, and 19 excitation functions for nat Zr( d , x ) reactions were measured over a beam energy range of 6.3–47.64 MeV, where the independent cross sections for nat Zr( d , x ) 88 Nb and nat Zr( d , x ) 86m,g Y were measured for the first time. The well-characterized nat Fe( d , x ) 56 Co, nat Ni( d , x ) 56 Co, nat Ni( d , x ) 58 Co, nat Ni( d , x ) 61 Cu, nat Ti( d , x ) 46 Sc and nat Ti( d , x ) 48 V monitor reactions were used to determine the deuteron beam current throughout the stacks. All cross sections were determined using High Purity Germanium (HPGe) detector γ -ray spectroscopy. A variance minimization technique was employed to simultaneously constrain the deuteron beam currents with multiple monitor reactions, thus reducing systematic uncertainties. An additional 16 channels are reported for reactions on the nickel, titanium, and iron monitor foils, leading to a total of 35 excitation functions, with seven reaction channels reported for the first time in this work. The measured excitation functions are compared to calculations provided by the reaction modeling codes TALYS – 2.0, ALICE – 2020, CoH – 3.5.3 and EMPIRE – 3.2.3, as well as the TENDL – 2023 data library. The degree of agreement between theory and experiments is discussed. The possible production of the important PET radionuclide 86g Y via the nat Zr( d , x ) route was critically examined. The physical yields for nat Zr( d , x ) 86 Y and other yttrium isotopes produced were calculated and compared to other production pathways. Due to high-level of associated radionuclide impurities, this route cannot deliver 86g Y suitable for medical applications.
Deuteron-induced reactions on natural Zr from threshold to 50 MeV: production of $^{86}$Y
ArXiv.org · 2025-06-23
preprintOpen accessTwo stacks of thin Zr foils were irradiated with 30 and 50 MeV deuterons, respectively, using the Lawrence Berkeley National Laboratory $88$-Inch Cyclotron, to investigate this production pathway for the promising PET tracer $^{86}$Y. Nineteen excitation functions for $^{\text{nat}}$Zr($d$,$x$) reactions were measured over a beam energy range of $6.3$--$47.64$ MeV, where the independent cross sections for $^{\text{nat}}$Zr($d$,$x$)$^{88}$Nb and $^\text{nat}$Zr($d$,$x$)$^{86\text{m, g}}$Y were measured for the first time. The well-characterized $^{\text{nat}}$Fe($d$,$x$)$^{56}$Co, $^{\text{nat}}$Ni($d$,$x$)$^{56}$Co, $^{\text{nat}}$Ni($d$,$x$)$^{58}$Co, $^{\text{nat}}$Ni($d$,$x$)$^{61}$Cu, $^{\text{nat}}$Ti($d$,$x$)$^{46}$Sc and $^{\text{nat}}$Ti($d$,$x$)$^{48}$V monitor reactions were used to determine the deuteron beam current throughout the stacks. All cross sections were determined using High Purity Germanium (HPGe) detector $γ$-ray spectroscopy. A variance minimization technique was employed to simultaneously constrain the deuteron beam currents with multiple monitor reactions, thus reducing systematic uncertainties. An additional $16$ channels are reported for reactions on the nickel, titanium, and iron monitor foils, leading to a total of $35$ excitation functions, with $7$ reaction channels reported for the first time in this work. The measured excitation functions are compared to calculations provided by the reaction modeling codes $\textsc{TALYS}-2.0$, $\textsc{ALICE}-2020$, $\textsc{CoH}-3.5.3$ and $\textsc{EMPIRE}-3.2.3$, as well as the $\textsc{TENDL}-2023$ data library. The degree of agreement between theory and experiments is discussed. The physical yields for $^{\text{nat}}$Zr($d$,$x$)$^{86}$Y and other yttrium isotopes produced are calculated and compared to other production pathways.
Burnup Measurement using Bent Crystal Diffraction Spectrometers for Pebble Bed Reactors
arXiv (Cornell University) · 2025-10-09
preprintOpen accessBurnup measurement is essential for monitoring and controlling pebble bed reactors (PBRs), where fuel pebbles circulate rapidly through the core. However, conventional gamma spectroscopy using high purity germanium (HPGe) detectors is difficult due to high activity levels in discharge pebbles, leading to excessive dead time and Compton scattering. This study explores the use of bent crystal diffraction (BCD) spectrometers to filter the emitted gamma spectrum and isolate key peaks for improved measurement accuracy and speed. Pebble wise depletion calculations were performed and the resulting spectra were analyzed using ray tracing (SHADOW3) and gamma response modeling (GADRAS). Key isotopes, $^{137m}$Ba/$^{137}$Cs, $^{239}$Pu, $^{144}$Ce, $^{148m}$Pm, and $^{140}$La, were found to strongly correlate with burnup, residence time, core passes, plutonium production, and fluence. Machine learning regression models applied to simulated spectra achieved a coefficient of determination ($R^2$) as high as 0.995 for burnup prediction. Among various BCD configurations, mosaic silicon crystals in the (440) orientation combined with an HPGe detector provided optimal performance for $^{137m}$Ba, while (220) and (440) configurations paired with scintillators were effective for the remaining isotopes.
Physical Review Letters · 2025-02-07 · 4 citations
articleOpen accessExcitation of long-lived states in bromine nuclei using a tabletop laser-plasma accelerator providing pulsed (<100 fs) electron beams provided a sensitive probe of γ strength and level densities in the nuclear quasicontinuum and may indicate angular momentum coupling through electron-nuclear interactions. Solid-density active LaBr_{3} targets absorb real and virtual photons up to 35±2.5 MeV and deexcite through γ cascade into different states. A factor of 4.354±0.932 enhancement of the ^{80}Br^{m}/^{80}Br^{g} isomeric ratio was observed following electron irradiation, as compared to bremsstrahlung. Additional angular momentum transfer could possibly occur through nuclear-plasma or electron-nuclear interactions enabled by the ultrashort electron beam. Further investigation of these mechanisms could have far-reaching impact including decreased storage of long-term nuclear waste and an improved understanding of heavy element formation in astrophysical settings.
Proceedings for the Workshop on Applied Nuclear Data Activities 2025
2025-08-12
reportOpen access
Frequent coauthors
- 248 shared
D. L. Bleuel
Lawrence Livermore National Laboratory
- 215 shared
D. T. Casey
Lawrence Livermore National Laboratory
- 149 shared
P. Fallon
Lawrence Berkeley National Laboratory
- 141 shared
A. O. Macchiavelli
Oak Ridge National Laboratory
- 128 shared
J. A. Caggiano
Lawrence Livermore National Laboratory
- 127 shared
J. A. Frenje
Fusion Academy
- 126 shared
H. G. Rinderknecht
Energetics (United States)
- 125 shared
M. Gatu Johnson
Massachusetts Institute of Technology
Education
- 1994
Ph.D., Physics
Rutgers University New Brunswick
- 1990
M.S., Physics
University of Maryland
- 1988
B.A., Physics
Rutgers University New Brunswick
Awards & honors
- Fellow of the American Physical Society (Division of Nuclear…
- Recipient of 3 LLNL Physical and Life Science Directorate Aw…
- Director's Science and Technology Award for the Development…
- Physics Division Award for Teaching Nuclear Physics in HED P…
- Recipient of the Defense Programs Award of Excellence for Me…
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