Sponsored by the
National Science
Foundation
By Billy Mohr
Advisor: Professor Daryl Hartley
Experiment at Gammasphere
Heavy Ion Fusion Reaction
– 124Sn(51V,4n)171Ta
Experiment was designed to
look for Triaxial Deformation
n
nn
n
Process
Fusion
Evaporation (4 neutrons)
Statistical Gamma rays
Discrete Gamma Rays
Yrast Line
Data Analysis
Necessary to Do:
-Calibration of Detectors
Need to account for Doppler shift of energies due to the
moving target.
Same Physics done in General Physics still applies: Ta171 is moving, thus detectors observes different
frequencies. (Energy proportional to frequency)
-Efficiency of Detectors
Done with known sources with known energy states of
gamma ray emmission.
Important to account for relative efficiency since
Gammasphere does not detect different energies equally.
Then we can begin to analyze the spectrum
Eu-152 Spectrum
Used for Calibration of Detectors since Energies were Known
Relative Efficiency Diagram
Used 182Ta, 152Eu, 56Co sources
High Energy
Full Range
Channel # (Correlates to Energy)
Relative Efficiency
Low energy
Doppler Shift Correction
32°
70 °
90 °
110 °
148 °
E (Φ) =Eo(1+βcos(Φ))
β=(speed of Ta-171)/(speed of light)
Φ=Angle at which detectors were relative to target
Data Analysis of Ta-171
It is possible to determine shape and
behavior of a nucleus from the decay
sequences and energy states at which it
emits gamma rays.
The energies that Gammasphere detected
were sorted into a 3-D Coincidence Matrix
All gamma rays being detected within
80ns were said to be coincidence with one
another
Data Analysis of Ta-171
Sample Spectrum
g 7/2
h 9/2
J.C. Bacelar et al., Nucl. Phys. A 442, 54
(1985) h 11/2
(with only 6 detectors)
d 5/2
d 3/2
i 13/2
What does all this mean??
•A Level Scheme is useful for:
-Indications of deformations
-Alignment
-Trends in Energies
-Band Structure
-Backbending
Backbending is a term used to describe significant gains in
angular momentum that’s not due to rotation of the nucleus.
Evidence of Backbending
Theory predicts crossings
at 200 keV for the neutron
alignments and 530 keV for
the proton alignments
keV
d 5/2
g 7/2
270
280
h 11/2
266
h 9/2
d 3/2
293
270
Alignment Plot
20
Unexplained by Current Theory [g7/2]
18
16
i_x
ħ
14
Predicted by Theory [d5/2]
12
10
Series1
Series2
8
6
4
2
0
0
100
200
300
400
hbar*ome ga
keV
500
600
700
450
355
346
Summary
No evidence for triaxial deformation yet.
Further research required
Linked all bands together through
transitioning gamma rays.
Found approx. 130 new gamma rays.
Interesting back bending properties
Thanks 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.
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.
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 Zhang
QUESTIONS, CONCERNS,
COMMENTS, QUERIES,
INQUIRIES, QUANDRIES??