High Spin states in spherical and deformed nuclei studies using the INGA at VECC

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High Spin states in spherical and deformed nuclei
studies using the INGA at VECC

• Sandeep S Ghugre
• UGC-DAE Consortium for Scientific Research,
  Kolkata Centre

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Indian National Gamma Array
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Array of Six Clovers
Mounting Structure
Vertical Ring
Median Plane
Supports Six Clovers
Supports Four Clovers
Present Set-up
Two at 1250 Backward
Two at 900
Two at 400 Forward
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Electronics DAQ System

• Integrated Electronics Modules( from NSC) for
  Clover Detectors were used.
• Data Acquisition was done using a CAMAC-based
  multi-parameter system LAMPS, in the multicrate
  configuration.
• E?, T?, and RF- Gamma were recorded.
• The entire electronics DAQ were housed in the
  cave.

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Observation of Ultra-fast transitions in A50
Mass Region.
Level structure of the odd-odd nucleus 54Mn. M S
University Baroda
High spins states in 178Os. Panjab University
Lifetime measurements in 101Pd. Mumbai University
Spectroscopy of few-valance particle nuclei
around 146Gd core Shape co-existence in
153Ho. B E S U
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Gamma ray spectroscopy following the 20Ne
40Ca reactions at 150 MeV
Indian National Gamma Array

• UGC DAE Consortium for Scientific Research ,
  Kolkata Centre
• Visva-Bharati University, Mumbai University,
  University of Notre Dame, Banaras Hindu
  University, M.S.University Baroda , SINP, VECC
  and NSC

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20Ne 40 Ca _at_ 150 MeV
PRC22 (1980) 2424
O
Ti
V
Sc
F
Cr
Ne
Mn
C
N
The Full line Measured Data Dashed Line
Evaporation Residue Distribution
Calculated with ALICE Code
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Physics Motivation ????

• Most of the Populated Nuclei
• are f7/2 shell nuclei
  (Proton Number between the
• 
  Magic Numbers 20 and 28)
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Characterized by Large
Deformation near the Ground state
Middle of the Shell f7/2
Moving away towards the End of the Shell f7/2
The Collective Behaviour is replaced by
Single - Particle Effects.
With Increasing Excitation Energy
Band Termination Shape Changes
Backbending Effects
Single particle Degrees of freedom and the
Collective ones Compete to produce.
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Experimental details

• Beam 20Ne
• Target Natural Ca sandwiched between two
  mylar films
  Front Mylar thickness
  4 ?m
• Backing Mylar
  thickness 25 ?m
• Target Thickness 5mg/cm2
• Event Rate 2.5k/sec
• Events Recorded 80 Million
  Gamma-Gamma Coincidence Events
• were
  Recorded.

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Fast Transitions in 50Cr
Partial Level Scheme of 50Cr
Representative Gated g Spectrum (Fingerprint
of a Nucleus !!!!!)?
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Doppler Shift in Transitions above 15/2- level in
51Cr !!!!
Nuclear Level Lifetime ltlt Stopping time of the
Recoil
Gamma-rays are emitted in flight
Partial Level Scheme of 51Cr
Representative Gated g Spectrum (Fingerprint
of a Nucleus !!!!!)?
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Turned towards the Calculation of Fractional
Doppler Shift
....A Measurement of Nuclear Level Lifetime
Shifted g-Energy
Detector Angle
Actual Un-shifted g-Energy
Fractional Doppler Shift
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Our Aim
To measure Experimental F(t)? To simulate
Theoretical F(t)? To extract Effective
Lifetime after comparing them To
extract Mean Lifetime of the Nuclear Levels
after applying the Feeding
correction

• Difficulties
• 1gt Thick Target
• 2gt Different Reaction Mechanisms
• 2gt Angular spreading

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Solution

• Development of a new Monte Carlo Algorithm
• 1gt Optimized for two media
• 2gt Incorporates the idea of cross-section
  distribution over the thickness of
  the target
• 3gt Takes care of Angular straggling

_at_ Mean Lifetime values of 51Cr and 49V have been
Extracted after comparing the algorithm and
method with the Precise DSAM measurement of 50Cr
_at_ Shell Model Calculation are being applied to
interpret the results.
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0.18
0.73
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Shell Model Calculations
Calculations performed using NuShell, using 40Ca
as the core, within the fp model space, where we
allowed up to t nucleons To be excited from
f7/2 shell to the rest of fp shell.
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51Cr
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Gamma ray spectroscopy following the 20Ne
51Vreaction at 145 MeV M S University of
Baroda
Best Poster Presentation Award at SAIP-06
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The energy levels of 54Mn were populated by a
145 MeV 20Ne beam incident on a 51V target .
This difficult to access N29 nucleus was
populated by non-equilibriated reaction.
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Clover detector has uniquely facilitated
polarization measurements, which are crucial for
spin-parity assignment.
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The level structure of 54Mn has been extended up
to E ? 5 MeV and J? 15
The absence of any regular band-like structure in
54Mn indicates the dominance of single particle
nature of this odd-odd nucleus.
The polarization measurements indicate the
possibility of a negative parity level at
1925-keV.
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The Os nuclei belongs to the transitional region
between the well-deformed rare earth and
spherical lead isotopes. The nuclei in this mass
region are believed to be soft to changes in
deformation due to the softness of nuclear
potential and consequently may result in the
shape co-existence. High spin states in the
178Os nucleus were populated using the
165Ho(20Ne, p6n) reaction at an incident beam
energy of 150 MeV.
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178Os
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g 0o
Prolate deformation in the ground state
g -15o
g-softness at higher excitation energies
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Thanks for your Kind Attention !!!!