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The Oslo Method Applied The Oslo Method Applied

The Oslo Method Applied - PowerPoint Presentation

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The Oslo Method Applied - PPT Presentation

to the QuasiContinuum of E xcited N uclei Magne Guttormsen Department of Physics and SAFE University of Oslo Oslo Seminar Oslo 6 December 2012 The Oslo Method Oslo Seminar Oslo 6 December 2012 ID: 356055

2012 oslo seminar december oslo 2012 december seminar level density phys 3he quasi rev particles guttormsen nim matrix thermal 232th 232 generation

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Slide1

The Oslo Method Applied

to the Quasi-Continuum

of

Excited NucleiMagne GuttormsenDepartment of Physics and SAFE University of Oslo

Oslo Seminar, Oslo, 6 December, 2012Slide2

The Oslo Method

Oslo Seminar, Oslo, 6 December, 20121) M. Guttormsen et al., NIM A374 (1996) 3712) M. Guttormsen et al., NIM A255 (1987) 5183) A. Schiller et al., NIM A447 (2000) 498Analysis of possible systematic errors of the Oslo methodA.C. Larsen et al.,

Phys. Rev. C 83, 034315 (2011)Measure particle-g coincidencesUnfold  spectra at each E 1)

Apply the first-generation method 2)Ansatz: First-generation matrix P(E, E)  (E - E)  T(E) 3) Normalization

Examples of

level

densitySlide3

Experiments at OCL

12 MeV d on 232Th 24 MeV 3He on 232Th g3He –beam 3He, a,d

,t

5”x5” NaIM.Guttormsen

, A.Bürger, T.E.Hansen, N.Lietaer

, NIM A648(2011)168

∆E-E

Backwards:

J

= 40

o

– 54

o

Oslo Seminar, Oslo, 6 December, 2012Slide4

∆E-E bananas

(d,d’)232Th (d,p)233Th(3He,t)232Pa (3He,d)233Pa(

3He,a)231Th

Oslo Seminar, Oslo, 6 December, 2012Slide5

Assumption for the extraction of

first-generation g-spectraOslo Seminar, Oslo, 6 December, 2012

(

d,p)(d,p)

The

g

-energy distribution is the same

if the decay starts at E after

g

-emission or

starts after the direct reaction into E.

E

gSlide6

Gamma-multiplicity

Oslo Seminar, Oslo, 6 December, 2012Slide7

From total to primary g-ray matrix

s

pin

2-6

ħ

E

x

232

Th(

d

,p

)

233

Th

Oslo Seminar, Oslo, 6 December, 2012Slide8

Primary g-ray matrix P(Ex,Eg) Level density

Trans. coeff.r(Ef) T(Eg)

P(Ex,Eg) Oslo Seminar, Oslo, 6 December, 2012Slide9

Multiplicative factorsOslo Seminar, Oslo, 6 December, 2012

Brink

hypothesis

Fermi’s

golden

ruleSlide10

P(Ex,Eg) = r(Ef) . T(Eg) ?

Oslo Seminar, Oslo, 6 December, 2012Slide11

Normalization

Oslo Seminar, Oslo, 6 December, 2012A. Gilbert and A.G.W. Cameron, Can. J. Phys. 43, 1446 (1965)T. von Egidy and D. Bucurescu, Phys. Rev. C 72, 044311 (2005), Phys. Rev. C 73, 049901(E) (2006)S. Goriely, HF+

BCS Demetriou and Goriely, Nucl. Phys. A695 (2001) 95 44Sc

Average level spacings D from neutron capture: Slide12

r(Ef) and T(Eg)

Oslo Seminar, Oslo, 6 December, 2012Slide13

231,232,233Th and 232,233PaInverse energy-weighted sum rule:

K. Heyde, P. von Neumann-Cosel, A. Richter, Rev. Mod. Phys., 82, 2365 (2010)Oslo Seminar, Oslo, 6 December, 2012M. Guttormsen et al., PRL 109, 162503 (2012) Slide14

Thermal quasi-particles,

the spectators of mid-shell nucleiOslo Seminar, Oslo, 6 December, 2012Slide15

Thermal quasi-particles create level density

Oslo Seminar, Oslo, 6 December, 2012

Cooper pair Broken pair

1 level 25 levelsSlide16

A simple model for level density

Oslo Seminar, Oslo, 6 December, 2012

-

Combining all possible proton and neutron configurations- Nilsson single-particle energy scheme- BCS quasi-particles

jSlide17

Nilsson level scheme

Oslo Seminar, Oslo, 6 December, 2012Model parameters: = 0.066 = 0.32 = 0.23

1p 1n

1p 3n1p 5n1p 7n

3p 1n

3p 3n

3p 5n

5p 1n

5p 3n

7p 1n

20Slide18

Level density and broken pairs

Oslo Seminar, Oslo, 6 December, 2012

Level densities Number of broken pairsSlide19

Parity asymmetry

Oslo Seminar, Oslo, 6 December, 2012

U. Agvaanluvsan, G.E. Mitchell

, J.F. Shriner Jr., Phys. Rev. C 67, 064608 (2003)Slide20

Titanium and tin

Oslo Seminar, Oslo, 6 December, 201246TiSlide21

Summary

Oslo Seminar, Oslo, 6 December, 2012Simultaneous extraction of level density and g-strength functionExamples from A = 40 – 230Number of thermal quasi-particles determines number of levelsConstant temperature level densityFluctuations for lighter even-even nucleiSlide22

Oslo Seminar, Oslo, 6 December, 2012

http://tid.uio.no/workshop2013/