INDIRECT DETERMINATION OF NEUTRON CAPTURE CROSS SECTIONS ON SPHERICAL AND NEAR-SPHERICAL NUCLEI USING THE SURROGATE METHOD

Bethany L. GoldblumBerkeley Nuclear Research CenterDepartment of Nuclear EngineeringUniversity of California, Berkeley

THE SURRO

GATE METHO

DNuclear Reactions Schematic

93Mo*

Pn P

n

Desired Reaction

d

Direct Reactionp

92Mo 92Mo

92Mo(d,p) 93Mo 92Mo(n,) 94Mo(d,p) 95Mo 94Mo(n,)

METHO

DOLO

GYAbsolute Surrogate Measurement

Surrogate Ratio Measurement

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σn,γ92Mo =σ n,abs

92Mo N(d ,pγ )93Mo (Ex )

N(d ,p )93Mo(E x )

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σn,γ92Mo =

σ n,abs92Mo(En )σ n,abs

94 Mo(En )

N(d ,pγ )93Mo (Ex )

N(d ,p )93Mo(E x )

N(d ,p )95Mo(E x )

N(d ,pγ )95Mo (Ex )

σ n,γ94Mo

EXPERIMEN

TAL METHO

DSSTARS-LiBerACE

• 11 MeV Deuteron Beam

• 92Mo: 460 ± 5 μg/cm2 Target-DE spacing: 9 mm

• 94Mo: 250 ± 6 μg/cm2 Target-DE spacing: 21 mm

Discrete -rayTagging

Statistical -rayTagging

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Pγ =N(d ,pγ )(Ex )N(d ,p )(Ex )

IDENTIFICATION OF THE NUMBER OF -CASCADES IN COINCIDENCE WITH THE SURROGATE REACTION EJECTILE

Discrete -rayTagging

Statistical -rayTagging

IDENTIFICATION OF THE NUMBER OF -CASCADES IN COINCIDENCE WITH THE SURROGATE REACTION EJECTILE

Energy (keV)

93Mo: Epeak = 943 keVEx = 8000-8100 keV

IDENTIFICATION OF THE NUMBER OF -CASCADES IN COINCIDENCE WITH THE SURROGATE REACTION EJECTILE

Discrete -rayTagging

Statistical -rayTagging

Energy (keV)

93Mo: E = 6-7 MeVEx = 8000-8100 keV

92Mo(n,) CRO

SS SECTION

Absolute Surrogate Measurement

92Mo(n,) CRO

SS SECTION

Surrogate Ratio Measurement

EVALUATION

OF -DECAY TAGGIN

G TECHNIQ

UES

-decay probability of 93Mo and 95Mo

EVALUATION

OF -DECAY TAGGIN

G TECHNIQ

UES

Ratio of the Statistical to Discrete Tag

CONCLUSIONS

1. First use of the surrogate method in the indirect determination of neutron-induced reaction cross sections on spherical and quasi-spherical nuclei

2. To improve the discrete tag, empirical data on nuclear level schemes could be used to sum parallel decay paths

3. To improve the statistical tag, the -ray energy range should be constrained to isolate primary -transitions

4. Discrete and statistical -decay tags likely capture similar information for more deformed nuclei

B.L. Goldblum, et al., Phys. Rev C 85, 054616 (2012).

COLLABORATORS

M. Wiedeking, L.A. Bernstein, D.L. Bleuel, F.S. Dietrich, R. Hatarik, S.R. Lesher, N.D. Scielzo

P.T. Lake, I.-Y. Lee, S. Pachalis, M. Petri, L. Phair

K. Alfonso, R. Vial, J. Vujic

T. Reed

J.M. Allmond