By Billy Mohr

Advisor: Professor Daryl HartleySponsored by the National Science Foundation

Experiment at GammasphereExperiment at Gammasphere

Heavy Ion Heavy Ion Fusion Reaction Reaction– 124124Sn(Sn(5151V,4n)V,4n)171171TaTa

Experiment was designed to Experiment was designed to look for Triaxial Deformationlook for Triaxial Deformation

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ProcessProcessFusionFusion

Evaporation (4 neutrons)Evaporation (4 neutrons)Statistical Gamma raysStatistical Gamma raysDiscrete Gamma RaysDiscrete Gamma Rays

Yrast LineYrast Line

DataData AnalysisAnalysisNecessary to Do:Necessary to Do:-Calibration of Detectors-Calibration of Detectors

Need to account for Doppler shift of energies due to the Need to account for Doppler shift of energies due to the moving target. moving target. Same Physics done in General Physics still applies: Ta-Same Physics done in General Physics still applies: Ta-171 is moving, thus detectors observes different 171 is moving, thus detectors observes different frequencies. (Energy proportional to frequency)frequencies. (Energy proportional to frequency)

-Efficiency of Detectors-Efficiency of DetectorsDone with known sources with known energy states of Done with known sources with known energy states of gamma ray emmission.gamma ray emmission.Important to account for relative efficiency since Important to account for relative efficiency since Gammasphere does not detect different energies equally.Gammasphere does not detect different energies equally.

Then we can begin to analyze the spectrumThen we can begin to analyze the spectrum

Eu-152 SpectrumEu-152 Spectrum

Used for Calibration of Detectors since Energies were KnownUsed for Calibration of Detectors since Energies were Known

Relative Efficiency DiagramRelative Efficiency Diagram

Channel # (Correlates to Energy)Channel # (Correlates to Energy)

Relative E

fficiency

Relative E

fficiency

Used Used 182182Ta, Ta, 152152Eu, Eu, 5656Co sourcesCo sources

Low energyLow energyFull RangeFull Range

High EnergyHigh Energy

Doppler Shift CorrectionDoppler Shift Correction

E (E (ΦΦ) =Eo(1+) =Eo(1+ββcos(cos(ΦΦ))))

ββ=(speed of Ta-171)/(speed of light)=(speed of Ta-171)/(speed of light)

ΦΦ=Angle at which detectors were relative to target=Angle at which detectors were relative to target

3232°°

7070 °°

9090 °°

110110 °°

148148 °°

Data Analysis of Ta-171Data Analysis of Ta-171

It is possible to determine shape and It is possible to determine shape and behavior of a nucleus from the decay behavior of a nucleus from the decay sequences and energy states at which it sequences and energy states at which it emits gamma rays.emits gamma rays.The energies that Gammasphere detected The energies that Gammasphere detected were sorted into a 3-D Coincidence Matrixwere sorted into a 3-D Coincidence MatrixAll gamma rays being detected within All gamma rays being detected within 80ns were said to be coincidence with one 80ns were said to be coincidence with one anotheranother

Data Analysis of Ta-171Data Analysis of Ta-171

Sample SpectrumSample Spectrum

d 5/2d 5/2

h 9/2h 9/2g 7/2g 7/2

d 3/2d 3/2

h 11/2h 11/2

i 13/2i 13/2

J.C. Bacelar et al., Nucl. Phys. J.C. Bacelar et al., Nucl. Phys. A 442A 442, 54 , 54 (1985)(1985)(with only 6 detectors)(with only 6 detectors)

What does all this mean??What does all this mean??

•A Level Scheme is useful for:A Level Scheme is useful for:-Indications of deformations-Indications of deformations-Alignment-Alignment-Trends in Energies-Trends in Energies-Band Structure-Band Structure-Backbending-Backbending

Backbending is a term used to describe significant gains in Backbending is a term used to describe significant gains in angular momentum that’s not due to rotation of the nucleus. angular momentum that’s not due to rotation of the nucleus.

Alignment Plot

0

2

4

6

8

10

12

14

16

18

20

0 100 200 300 400 500 600 700

hbar*omega

i_x

Series1

Series2

d 5/2d 5/2 270270 450450

g 7/2g 7/2 280280 355355

h 11/2h 11/2 266266

h 9/2h 9/2 293293

d 3/2d 3/2 270270 346346

Theory predicts crossings Theory predicts crossings at 200 keV for the neutron at 200 keV for the neutron alignments and 530 keV for alignments and 530 keV for the proton alignmentsthe proton alignments

Evidence of BackbendingEvidence of Backbending

Predicted by Theory [d5/2]Predicted by Theory [d5/2]

Unexplained by Current Theory [g7/2]Unexplained by Current Theory [g7/2]

keVkeV

keVkeV

ħħ

SummarySummaryNo evidence for triaxial deformation yet.No evidence for triaxial deformation yet.

Further research requiredFurther research required

Linked all bands together through Linked all bands together through transitioning gamma rays.transitioning gamma rays.

Found approx. 130 new gamma rays.Found approx. 130 new gamma rays.

Interesting back bending propertiesInteresting back bending propertiesThanksThanks to D.J. Hartley, M.K. Djongolov, F.G. Kondev, H. Amro, A. to D.J. Hartley, M.K. Djongolov, F.G. Kondev, H. Amro, A. Aguilar, D.L. Balabanski, M.P. Carpenter, P. Chowdhury, W. Cluff, D.M. Aguilar, D.L. Balabanski, M.P. Carpenter, P. Chowdhury, W. Cluff, D.M. Cullen, M. Danchev, G.D. Dracoulis, G.B. Gagemann, A.M. Kishada, K. Cullen, M. Danchev, G.D. Dracoulis, G.B. Gagemann, A.M. Kishada, K. Lagergren, T. Lauritsen, E.F. Moore, E. Ngijoi-Yogo, S.W. Odegard, A. Lagergren, T. Lauritsen, E.F. Moore, E. Ngijoi-Yogo, S.W. Odegard, A. Pipidis, L.L. Riedinger, S.V. Rigby, M.A. Riley, D.T. Scholes, G. Sletten, Pipidis, L.L. Riedinger, S.V. Rigby, M.A. Riley, D.T. Scholes, G. Sletten, S.K. Tandel, C. Teal, J.R. Vanhoy, P.M. Walker, and Jing-ye ZhangS.K. Tandel, C. Teal, J.R. Vanhoy, P.M. Walker, and Jing-ye Zhang

QUESTIONS, CONCERNS, QUESTIONS, CONCERNS, COMMENTS, QUERIES, COMMENTS, QUERIES,

INQUIRIES, QUANDRIES??INQUIRIES, QUANDRIES??