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European SSAF Crete, Sept . 7-8, 2007 1 Oslo Cyclotron Laboratory and the Nuclear Physics Program S. Siem Department of Physics University of Oslo

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Page 1: European SSAF Crete, Sept. 7-8, 2007 European SSAF Crete, Sept. 7-8, 2007 1 1 Oslo Cyclotron Laboratory and the Nuclear Physics Program S. Siem Department

European SSAF Crete, Sept. 7-8, 2007European SSAF Crete, Sept. 7-8, 2007

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Oslo Cyclotron Laboratory and the

Nuclear Physics Program

Oslo Cyclotron Laboratory and the

Nuclear Physics Program

S. SiemDepartment of Physics

University of Oslo

S. SiemDepartment of Physics

University of Oslo

Page 2: European SSAF Crete, Sept. 7-8, 2007 European SSAF Crete, Sept. 7-8, 2007 1 1 Oslo Cyclotron Laboratory and the Nuclear Physics Program S. Siem Department

European SSAF Crete, Sept. 7-8, 2007European SSAF Crete, Sept. 7-8, 2007

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Oslo Cyclotron Laboratory (OCL)Oslo Cyclotron Laboratory (OCL)

Protons 2-35 MeVDeuterons4-18 MeV3He 6-47 MeV4He 8-35 MeV

Protons 2-35 MeVDeuterons4-18 MeV3He 6-47 MeV4He 8-35 MeV

Page 3: European SSAF Crete, Sept. 7-8, 2007 European SSAF Crete, Sept. 7-8, 2007 1 1 Oslo Cyclotron Laboratory and the Nuclear Physics Program S. Siem Department

European SSAF Crete, Sept. 7-8, 2007European SSAF Crete, Sept. 7-8, 2007

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Experimental set-upExperimental set-up

CACTUS:28 NaI 5”x5” and 8 Si telescopes

CACTUS:28 NaI 5”x5” and 8 Si telescopes

Page 4: European SSAF Crete, Sept. 7-8, 2007 European SSAF Crete, Sept. 7-8, 2007 1 1 Oslo Cyclotron Laboratory and the Nuclear Physics Program S. Siem Department

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The PhysicsThe PhysicsNuclear structure and decay properties in continuumNuclear structure and decay properties in continuum

Spin2 - 6 ħ

Ex

T = 1 MeV

Yrast line(no levels)

Page 5: European SSAF Crete, Sept. 7-8, 2007 European SSAF Crete, Sept. 7-8, 2007 1 1 Oslo Cyclotron Laboratory and the Nuclear Physics Program S. Siem Department

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The energy distribution of primary rays contains information on the level density ρ(Ef) and gamma-ray transmission coefficient T(E)

The Brink Axel hypothesis:

The Brink Axel hypothesis:

)()(),( ρ ETEEEP fi ⋅∝

Page 6: European SSAF Crete, Sept. 7-8, 2007 European SSAF Crete, Sept. 7-8, 2007 1 1 Oslo Cyclotron Laboratory and the Nuclear Physics Program S. Siem Department

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Level densityLevel density Gamma-ray strength functionsGamma-ray strength functions

148Sm

Page 7: European SSAF Crete, Sept. 7-8, 2007 European SSAF Crete, Sept. 7-8, 2007 1 1 Oslo Cyclotron Laboratory and the Nuclear Physics Program S. Siem Department

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147Sm

146Sm

Level Densities Level Densities • Left: Comparing even-even nuclei: the nuclei closer to a closed shell and

have smaller level density, but more structure.• Right: There is a big difference between odd and even nuclei due to pairing

• Left: Comparing even-even nuclei: the nuclei closer to a closed shell and have smaller level density, but more structure.

• Right: There is a big difference between odd and even nuclei due to pairing

Page 8: European SSAF Crete, Sept. 7-8, 2007 European SSAF Crete, Sept. 7-8, 2007 1 1 Oslo Cyclotron Laboratory and the Nuclear Physics Program S. Siem Department

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Microcanonical Temperature

Page 9: European SSAF Crete, Sept. 7-8, 2007 European SSAF Crete, Sept. 7-8, 2007 1 1 Oslo Cyclotron Laboratory and the Nuclear Physics Program S. Siem Department

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Radiative strength functions for some rare earth nuclei. Roughly, the shape corresponds to the tail of the giant electric dipole resonance (GEDR). There is a significant bump superimposed on the radiative strength function, which is interpreted as scissors mode in continuum (M1).

Radiative strength functions for some rare earth nuclei. Roughly, the shape corresponds to the tail of the giant electric dipole resonance (GEDR). There is a significant bump superimposed on the radiative strength function, which is interpreted as scissors mode in continuum (M1).

Page 10: European SSAF Crete, Sept. 7-8, 2007 European SSAF Crete, Sept. 7-8, 2007 1 1 Oslo Cyclotron Laboratory and the Nuclear Physics Program S. Siem Department

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Scissors mode

Established M1 multipolarity of a pygmy

resonance in 172Yb at Eγ = 3.3 MeV

B(M1↑) =9hc

32π 2

σΓ

E

⎝ ⎜

⎠ ⎟py

= 6.5(15)μN2

π ν

Page 11: European SSAF Crete, Sept. 7-8, 2007 European SSAF Crete, Sept. 7-8, 2007 1 1 Oslo Cyclotron Laboratory and the Nuclear Physics Program S. Siem Department

European SSAF Crete, Sept. 7-8, 2007European SSAF Crete, Sept. 7-8, 2007

1111A.Voinov et al. Phys.Rev.Lett.93, 142504 (2004)

Radiative strength function of 57Fe

A large unexpected increase in the radiative strength function was first seen in iron. We still don’t have an explanation for what the physics behind it is.

Page 12: European SSAF Crete, Sept. 7-8, 2007 European SSAF Crete, Sept. 7-8, 2007 1 1 Oslo Cyclotron Laboratory and the Nuclear Physics Program S. Siem Department

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Features and future plansFeatures and future plans

• OCL is modern and well equipped• Continues beam time of 1-2 weeks• New Silicon Ring (SiRi) with 64

particle telescopes• Plans to replace the 28 NaI

detectors with BrilLanCe 380 crystals

• OCL is modern and well equipped• Continues beam time of 1-2 weeks• New Silicon Ring (SiRi) with 64

particle telescopes• Plans to replace the 28 NaI

detectors with BrilLanCe 380 crystals

Page 13: European SSAF Crete, Sept. 7-8, 2007 European SSAF Crete, Sept. 7-8, 2007 1 1 Oslo Cyclotron Laboratory and the Nuclear Physics Program S. Siem Department

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In Oslo we now have:

2 PhD positions and

1 Postdoc position

To be filled as soon as possible.

[email protected]