Nuclear Level Densities of Residual Nuclei from evaporation of 64Cu

Moses B. OginniOhio University

SNP2008July 9, 2008

List of Collaborators• S. M. Grimes, C. R. Brune, T. N. Massey

• A. V. Voinov

• A. S. Adekola, Z. Heinen

• D. Carter, D. Jacobs, J. O’Donnell

• Andreas Heinz (Yale University)

Outline

• Introduction

• Experiments and facilities

• Results

• Outlook and Conclusion

Introduction

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• The study of NLD based on Bethe’s idea.[*] 2 assumptions: - non-interacting fermions

- single particle states are equidistantin energy.

* H. A. Bethe, Phys. Rev. 50, 336 (1936)

MODEL PARAMETERS FOR NLD

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• General pattern for level density parameter is given as:

ROHR Al-Quraishi

[**]

[**]

** S.I. Al-Quraishi et al, Phys. Rev. C63, 065803(2001).

a = 0.071*A + V V = 1.64 A ≤ 38 V = 3.74 38 < A ≤ 69 V = 6.78 69 < A ≤ 94 V = 8.65 94 < A < 170 a = 0.108*A + 2.4 A ≥ 170

[*]

* G. Rohr, Z Phys. A – Atoms and Nuclei 318, 299 – 308 (1984).

α = 0.1062, β = 0.00051

α = 0.1068, γ = 0.0389

Experiments

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6Li + 58Fe

7Li + 57Fe

64Cu

p + 63Ni

n + 63Cu

α + 60Co

6Li + 55Mn 61Nip + 60Con + 60Niα + 57Fe

Edwards Accelerator Facility

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beamTarget

Si

Si

Si

SiSi

SiSi

Si

Si

Si

2m flight path

Scheme of experimental set-up for charge-particle spectra measurementsEdward’s Accelerator Lab, Ohio University

N

8

Particle ID

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•TOF and E information were used to separate the charged particles.

•PSD and E information were used to separate the neutrons and the photons.

Calibrations

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Charged Particle Energ y Calibration

-elastic scattering of Li6 on Gold-elastic scattering of Li7 on Gold-elastic scattering of d on Gold-alpha source of 3 known peaks

Neutron Efficiency Calibration

-Using the result of Al27(d,n) reaction from Massey et al. (Nucl. Sci. andEng.,129,175-179(1998))as standard.

Angular distributions

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•Angular distribution of compound nuclear reaction is expected to be symmetric about 90 degree.

Proton Spectrum (I)

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Proton Spectrum (II)

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Alpha Spectrum (I)

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Alpha Spectrum (II)

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Proton Spectrum (III)

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6Li + 58Fe

7Li + 57Feα + 60Co

6Li + 55Mn p + 60Co

Deuteron Spectrum (I)

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Deuteron Spectrum (II)

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Break Up Study6Li α + d (Q = -1.47MeV) α + n + p (Q = -3.70MeV) 5He + p (Q = -4.59MeV)

7Li α + t (Q = -2.47MeV) α + d + n (Q = -8.72MeV) 5He + d (Q = -9.61MeV) 6He + p (Q = -9.98MeV) α + 2n + p (Q = -10.95MeV) 5He + n + p (Q = -11.84MeV)

• Is the break up a 1-step process or a 2-step process ?6Li 6Li* … 7Li 7Li* …

Energy Levels of 6Li and 7Li

* http://www.tunl.duke.edu/

Energy levels of 6Li

Energy levels of 7Li

Neutron Spectrum (I)

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Neutron Spectrum (II)

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Future Prospects

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• Test data with other models aside Fermi-gas• Quantify the contributions of break up to our evaporation spectra.

• Other experiments under study are :Experiments Z-Zо

0

2

4

Conclusion

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•Rohr systematic appears to describe well protons spectra but did not do well with alpha spectra because of break-up contributions.•We believe that the alpha spectra up to 8MeV cannot be usedfor estimating level density because of the break up contribution•Our analysis shows that tentative LD parameters can be assigned as follows:

63Ni: a = 8.21/MeV, δ = 1.51MeV63Cu: a = 8.21/MeV, δ = 1.51MeV60Co: a = 8.00/MeV, δ = 0.00MeV

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EXTRASLIDES

Optical Parameters