Statistical Nuclear Physics and (α,n) Reactions For Applications (Zach Meisel, Ohio University) 1
Statistical Nuclear Physics and (α,n) Reactions for ApplicationsZach Meisel (Ohio University), DE-NA0003909
Goal: To increase the accuracy and predictive power of statistical descriptions of nuclear reactions. This is done by benchmarking model calculations against experimental data. Specifically, nuclear level-densities are measured via particle evaporation spectra and (α,n) cross sections are directly measured.
Personnel: The experimental low-energy nuclear physics group at Ohio University(bold green are funded by this work)
• Faculty: Zach Meisel, Alexander Voinov, Carl Brune, Steve Grimes, Tom Massey• Postdoctoral Research Associates: Mansi Saxena• Graduate Students: Kristyn Brandenburg, Michael Hartos, Joseph Derkin,
Gula Hamad, Yenuel Jones-Alberty, Som Paneru, Doug Soltesz,Shiv Subedi, Justin Warren
Products: 9 publications and 7 invited presentationsPublished Outcome: A.V. Voinov et al. PRC 99, 054609 (2019)
Statistical Nuclear Physics and (α,n) Reactions For Applications (Zach Meisel, Ohio University) 2
X-ray burstsNeutrino-driven winds (proton-rich)Core collapse supernovae shocksNeutrino-driven winds (neutron-rich)Neutron star mergersNeutron star crusts
Nuclear properties are needed across the nuclear landscape
Applications with Fissile Materials Extreme Astrophysical Environments
Statistical Nuclear Physics and (α,n) Reactions For Applications (Zach Meisel, Ohio University) 3
Hauser-Feshbach formalism: The approach to calculate σstatisticalSy
stem
Ene
rgy ECM
X + a
Z
γ Y + b
ba
Reaction of Interest
Z
β+ decay or
Reaction
Easier to Perform Reaction
ba
γ
Formation Decay
Formation
Decay
𝜎𝜎𝑋𝑋 𝑎𝑎,𝑏𝑏 𝑌𝑌𝐻𝐻𝐻𝐻 = 𝜋𝜋
λ𝜋𝜋
2
�𝐽𝐽
2𝐽𝐽 + 1(2𝐽𝐽𝑎𝑎 + 1)(2𝐽𝐽𝑋𝑋 + 1)
𝑊𝑊𝑎𝑎𝑏𝑏𝑇𝑇𝑎𝑎𝑋𝑋𝑇𝑇𝑏𝑏𝑌𝑌
∑𝑐𝑐ℎ𝑎𝑎𝑎𝑎 𝑇𝑇𝑐𝑐ℎ𝑎𝑎𝑎𝑎
Formation
Decay
Statistical Nuclear Physics and (α,n) Reactions For Applications (Zach Meisel, Ohio University) 4
The Edwards Accelerator Laboratory at Ohio University
Statistical Nuclear Physics and (α,n) Reactions For Applications (Zach Meisel, Ohio University) 5
HF ingredients: Level densities, strength functions, & optical potentials
𝜎𝜎𝑋𝑋 𝑎𝑎,𝑏𝑏 𝑌𝑌𝐻𝐻𝐻𝐻 = 𝜋𝜋
λ𝜋𝜋
2
�𝐽𝐽
2𝐽𝐽 + 1(2𝐽𝐽𝑎𝑎 + 1)(2𝐽𝐽𝑋𝑋 + 1)
𝑊𝑊𝑎𝑎𝑏𝑏𝑇𝑇𝑎𝑎𝑋𝑋𝑇𝑇𝑏𝑏𝑌𝑌
∑𝑐𝑐ℎ𝑎𝑎𝑎𝑎 𝑇𝑇𝑐𝑐ℎ𝑎𝑎𝑎𝑎is a bit too cute for it’s own good…
Get from γ-strength function(or, for particles, optical model potential)
Level Densityof decay daughter
For one calculation, need several OMPs, γSFs, and ρLD:For each channel:
Reasonable input choices can lead to order-of-magnitude+ reaction rate uncertainties.
Statistical Nuclear Physics and (α,n) Reactions For Applications (Zach Meisel, Ohio University) 6
Nuclear Level Density is hard to predict on stability, and is poorly constrained off
CS impact of LD on (n,γ) on stable isotopesBeard et al. PRC 2014
Spread in LD predictions & data for…
52Cr
60Zn
Zelevinsky & HoroiPPNP 2019
Soltesz et al. In PrepAl Quraishi et al.
PRC 2001
LD reduction off-stability has been suggested empirically and based on considering “effective level density”
Statistical Nuclear Physics and (α,n) Reactions For Applications (Zach Meisel, Ohio University) 7
Our approach to constraining nuclear level density:The particle evaporation method
Y + b
b
Number of decays to daughter states (Y) will be related to the number of states within an excitation
energy region
Statistical Nuclear Physics and (α,n) Reactions For Applications (Zach Meisel, Ohio University) 8
Our approach to constraining nuclear level density:The particle evaporation method
A.V. Voinov et al. PRC 2019
Statistical Nuclear Physics and (α,n) Reactions For Applications (Zach Meisel, Ohio University) 9
Our goal is to establish systematics of the nuclear level density
A.V. Voinov et al. PRC 2019
Year 1 results:• 74,76Ge level densities are lower than many predictions
(excellent agreement with SM: Ormand & Brown arXiv:1912.08973)
and D0• This impacts LD extractions requiring
normalization at high energies• 59Mn decay analysis ongoing (BSFG favored for 58Cr)
Michael Hartos (GS)
74Ge
76Ge
24Mg(7Li,p)In collaboration with
Statistical Nuclear Physics and (α,n) Reactions For Applications (Zach Meisel, Ohio University) 10
(α,n) reactions matter for many applications, yet direct data are sparse
Statistical Nuclear Physics and (α,n) Reactions For Applications (Zach Meisel, Ohio University) 11
86Se(α,xn) P. Mohr PRC 2016
The (α,n) cross section dependency on the αOMP means that measurements can improve theoretical estimates for nuclides
in a similar region of the nuclear chart
J. Glorius et al. PRC 2014
R. Talwar et al. PRC 2018
(α,n) theory predictions depend on the α optical potential (αOMP)
Statistical Nuclear Physics and (α,n) Reactions For Applications (Zach Meisel, Ohio University) 12
HeBGB, custom built for (α,n) measurements at the EALK. Brandenburg MS Thesis (OU) 2017
Kristyn Brandenburg (GS)
27Al(α,n)
online analysis
Year 1 results:• Completed with SSAA funds• Validated efficiency with
51V(p,n) and 13C(α,n)• Performed first cross section
measurement: 27Al(α,n)• Analyses are ongoing
Gula Hamad (GS)
Statistical Nuclear Physics and (α,n) Reactions For Applications (Zach Meisel, Ohio University) 13
Join us in Athens, OH this July!
Meeting emphasis:• limits of the statistical model• overlaps between statistical nuclear physics for astrophysics and applications• fission and the r-process
INPP.OHIO.EDU/~T3
Statistical Nuclear Physics and (α,n) Reactions For Applications (Zach Meisel, Ohio University) 14
Thanks to: my collaborators and
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