Restricted Spin-Ranges in the Oslo Method
201
5 Summary and Conclusions
We have presented the first systematic analysis of the effect of a realistic, very
narrow spin distribution on the Oslo Method for the (d,p) reaction using the example
of the heavy nucleus 240 Pu. We have shown that if the assumptions of the Oslo
Method were fulfilled, i.e., if the reaction populated all levels proportionally to
the intrinsic spin(-parity) distribution, we regain the correct level density and γ -ray
strength. However, for such a heavy nucleus and a beam energy below the Coulomb
barrier, the calculations show a rather small overlap between the populated spins and
the intrinsic distribution. This leads to significant distortions in the extracted nuclear
level density and γ -ray strength. We now investigate how the presented approach
can be used to correct for the deviations. Finally, the impact on lower mass nuclei
needs to be studied, although a significantly greater overlap of the populated and
intrinsic distribution and therefore smaller impact is expected.
Acknowledgments We would like to thank J. C. Müller, E. A. Olsen, A. Semchenkov, and
J. C. Wikne at the Oslo Cyclotron Laboratory for providing the stable and high-quality
deuterium beam during the experiment. This work was supported by the Research Council
of Norway under project Grants No. 263030 (F.Z, A.G, S.S) and 262952 (G.M.T), and by
the National Research Foundation of South Africa (M.W.). A.C.L. gratefully acknowledges
funding from the European Research Council, ERC-STG-2014 Grant Agreement No. 637686.
This work was performed under the auspices of U.S. Department of Energy by Lawrence
Livermore National Laboratory under Contract No. DE-AC52-07NA27344 (D.L.B) and the
Lawrence Berkeley National Laboratory under Contract No. DE-AC02-05CH11231 (L.A.B.).
The work of B.L.G., J.A.B., and T.A.L. was supported by the U.S. Department of Energy,
National Nuclear Security Administration, Office of Defense Nuclear Nonproliferation Research
and Development (DNN R&D) through the Nuclear Science and Security Consortium under
Award DE-NA0003180. A.V. was supported under Department of Energy Contract No. DENA0002905.
References
1. J.L. Ullmann et al., Phys. Rev. C 96(2), 024627 (2017)
2. A. Schiller et al., Nucl. Instrum. Methods Phys. Res. A 447(3), 498–511 (2000)
3. A.C. Larsen et al., Phys. Rev. C 83(3), 034315 (2011)
4. M. Guttormsen et al., Phys. Rev. Lett. 109(16) (2012)
5. M. Guttormsen et al., Phys. Rev. C 88(2), 024307 (2013)
6. M. Guttormsen et al., Phys. Rev. C 89(1), 014302 (2014)
7. T.G. Tornyi et al., Phys. Rev. C 89(4), 044323 (2014)
8. T.A. Laplace et al., Phys. Rev. C 93(1), 014323 (2016)
9. K. Heyde et al., Rev. Mod. Phys. 82(3), 2365–2419 (2010)
10. R. Henderson et al., Nucl. Instrum. Methods Phys. Res., Sect. A 655(1), 66–71 (2011)
11. M. Guttormsen et al., Nucl. Instrum. Methods Phys. Res. A 648(1), 168–173 (2011)
12. M. Guttormsen et al., Phys. Scr. T32, 54–60 (1990)
13. T.G. Tornyi et al., Nucl. Instrum. Methods Phys. Res. A 738, 6–12 (2014)
14. M. Guttormsen et al., Nucl. Instrum. Methods Phys. Res. A 374(3), 371–376 (1996)
15. L.C. Campo et al., Phys. Rev. C 94(4) (2016)
201
5 Summary and Conclusions
We have presented the first systematic analysis of the effect of a realistic, very
narrow spin distribution on the Oslo Method for the (d,p) reaction using the example
of the heavy nucleus 240 Pu. We have shown that if the assumptions of the Oslo
Method were fulfilled, i.e., if the reaction populated all levels proportionally to
the intrinsic spin(-parity) distribution, we regain the correct level density and γ -ray
strength. However, for such a heavy nucleus and a beam energy below the Coulomb
barrier, the calculations show a rather small overlap between the populated spins and
the intrinsic distribution. This leads to significant distortions in the extracted nuclear
level density and γ -ray strength. We now investigate how the presented approach
can be used to correct for the deviations. Finally, the impact on lower mass nuclei
needs to be studied, although a significantly greater overlap of the populated and
intrinsic distribution and therefore smaller impact is expected.
Acknowledgments We would like to thank J. C. Müller, E. A. Olsen, A. Semchenkov, and
J. C. Wikne at the Oslo Cyclotron Laboratory for providing the stable and high-quality
deuterium beam during the experiment. This work was supported by the Research Council
of Norway under project Grants No. 263030 (F.Z, A.G, S.S) and 262952 (G.M.T), and by
the National Research Foundation of South Africa (M.W.). A.C.L. gratefully acknowledges
funding from the European Research Council, ERC-STG-2014 Grant Agreement No. 637686.
This work was performed under the auspices of U.S. Department of Energy by Lawrence
Livermore National Laboratory under Contract No. DE-AC52-07NA27344 (D.L.B) and the
Lawrence Berkeley National Laboratory under Contract No. DE-AC02-05CH11231 (L.A.B.).
The work of B.L.G., J.A.B., and T.A.L. was supported by the U.S. Department of Energy,
National Nuclear Security Administration, Office of Defense Nuclear Nonproliferation Research
and Development (DNN R&D) through the Nuclear Science and Security Consortium under
Award DE-NA0003180. A.V. was supported under Department of Energy Contract No. DENA0002905.
References
1. J.L. Ullmann et al., Phys. Rev. C 96(2), 024627 (2017)
2. A. Schiller et al., Nucl. Instrum. Methods Phys. Res. A 447(3), 498–511 (2000)
3. A.C. Larsen et al., Phys. Rev. C 83(3), 034315 (2011)
4. M. Guttormsen et al., Phys. Rev. Lett. 109(16) (2012)
5. M. Guttormsen et al., Phys. Rev. C 88(2), 024307 (2013)
6. M. Guttormsen et al., Phys. Rev. C 89(1), 014302 (2014)
7. T.G. Tornyi et al., Phys. Rev. C 89(4), 044323 (2014)
8. T.A. Laplace et al., Phys. Rev. C 93(1), 014323 (2016)
9. K. Heyde et al., Rev. Mod. Phys. 82(3), 2365–2419 (2010)
10. R. Henderson et al., Nucl. Instrum. Methods Phys. Res., Sect. A 655(1), 66–71 (2011)
11. M. Guttormsen et al., Nucl. Instrum. Methods Phys. Res. A 648(1), 168–173 (2011)
12. M. Guttormsen et al., Phys. Scr. T32, 54–60 (1990)
13. T.G. Tornyi et al., Nucl. Instrum. Methods Phys. Res. A 738, 6–12 (2014)
14. M. Guttormsen et al., Nucl. Instrum. Methods Phys. Res. A 374(3), 371–376 (1996)
15. L.C. Campo et al., Phys. Rev. C 94(4) (2016)