6th Dec 2011 ISOLDE Workshop, CERN
Reaction Dynamics studies with 6,7Li and 9Be nuclei at Pelletron, Mumbai, India
Vivek ParkarUniversity of Huelva, Spain
Previous affiliation :Bhabha Atomic Research Centre, Mumbai, India
Outline of Talk:
Introduction to 14UD Pelletron facility, Mumbai, India
Studies with stable weakly bound (6,7Li and 9Be) nuclei:
Fusion cross-sections
Inclusive and exclusive breakup
Dipole Polarizabilities of 7Li and 9Be
Future prospects with light RIBs at ISOLDE
A] Basic Research
Reaction studies near barrier
Fission studies
Nuclear Structure
Atomic Physics
Radio Chemistry studies
Magnetism
B] Applied Research
Radiation damage studies
Radiation Biology
Accelerator Mass
Spectroscopy (AMS)
Track etched membrane
Bio-environmental studies
http://www.tifr.res.in/~pell
Reactions with stable weakly bound nuclei
Low breakup threshold
Stable ions
6Li +d, Sd=1.48 MeV
7Li +t, St=2.47 MeV9Be ++n, Sn=1.57 MeV
Advantagelarge intensity and good beam quality
Study effect of breakup channel on elastic scattering and fusion cross-sections
Inclusive and exclusive breakup studies
Next step: Reaction dynamics with light RIBs
Fusion cross-sections from online and offline ray measurements
6,7Li+144,152Sm6,7Li+90Zr6,7Li+198Pt6,7Li+165Ho6,7Li+159Tb9Be+124Sn9Be+89Y
Motivation :Fusion in presence of breakup channel enhance fusion due to coupling OR suppress fusion due to loss of flux
Online ray technique: When ER is short lived (few secs) ray de-excitation from the excited states of that ER
Offline ray technique: When ER is long lived (few mnts - days) Measurement of rays after beta decay/Electron capture
Fusion = Σ ER
Evaporation Residue Measurement
Off-beam intensities of charac-teristic -lines from decay ofER and half-life were measured
F.C.Target &Catcher
Beam
Suppression (~28%) at E>Vb breakupEnhancement at E<Vb target deformationEffect of breakup and deformation coexist
Projectile breakup vs. target deformation
P. K. Rath et al., Nucl Phys. A (Accepted)
Systematic of fusion suppression factor
(i) For a particular projectile, the suppression factor is more or less independent of the product ZPZT , (ii) suppression increases with decreasing breakup threshold of the projectile.
Exploring fusion at deep sub-barrier energies
New sensitive off-beam method KX - rays coincidence A. Lemasson et al., NIMA 598, 445 (2009)
A. Shrivastava et al., PRL 103, 232702 (2009)
Measurements: typical 2D
spectra
E (arb. unit)
E (
arb
. un
it)
7Li
6Li
t,d,p
(a) (b)
(c) (d)
Beam:6Li, Pelltron @TIFR
Energy: 24-50 MeV
Target:209Bi ~330 g/cm2 self-supporting
4 telescopes of SSB
S. Santra et al., Phys. Rev. C (Submitted)
Below barrier, = Reaction
Otherwise, CF+Reaction
Complete reaction picture for 6Li+209Bi
Exclusive breakup study of 6Li
FC
209Bi(1 mg/cm2)
6Li Beam(~40nA)
250
100
100100 T1
T2(d)
T3()
T4(d)
M1
M2
Detectors: 2 telescopes (E: ~ 33 and E: ~ 500), 2 telescopes (E:~150 and E: ~1000), and 2 single monitors (E ~ 2000) of Si surface barrier detectors
Measured: Light charged particles in singles as well as coincidence, in list mode
Angular range: 50o-170o.
Energy: 36 and 40 MeV
Projectile breakupDirect breakup: Projectile breaks up directly into fragments at any
excitation energy larger than breakup threshold.
Sequential breakup: Projectile excited to resonant state followed by breakup, or it can exchange a few nucleon with the target and then breaks up.
6Li209Bi
d
6Li6Li
6Li
6Li* 6Li*5Li
209Bi209Bi
d p
n
Typical two dimensional spectra with and
without coincidence conditions.
E(MeV)
15 20 25 30 35
Cou
nts
0
10
20
30
[a]
[e]
[f]
td
p
d
6Li
7Li
E (MeV)E (MeV)
E
(M
eV)
E
(M
eV)
E
(M
eV)
E
(M
eV)
[c]
[d]
[b]
Cou
nts
Ch. No.
T1 @ 55o T2 @ 65o
Inclusive and exclusive -production
CDCC results with full coupling agrees with the average of two sets of experimental data for 3+ resonant state
Total d (theory) << (incl)
p(exp) + d(th) << (incl)
Other possible sources : (1) (6Li,4He) (2) (6Li,5Hen+4He) (3) (6Li,7Li4He+t)(4) partial fusion (d-cap)
Breakup of 6Li at 40 MeV
d/d (m
b/sr
)
10-2
10-1
100
101
102
-d-sequential (expt.)-d-direct (expt.)-p-total (expt.)-d-sequential (theory)-d-total (theory)-inclusive (expt.)
Breakup of 6Li at 36 MeV
c.m. (deg)40 60 80 100 120 140
d/d (m
b/sr
)
10-2
10-1
100
101
102
[a]
[b]
S. Santra et al., PLB 677, 139 (2009)
Centre of matter distributions and centre of charge distributions of a nucleus do not coincide (e.g. deuteron, 7Li, 6He, 11Li etc.) in the presence of strong
electric field. Transition between states of opposite parity. (For normal nuclei states of opposite parity are at high excitation energy)For weakly bound nuclei low breakup threshold,
continuum states of opposite parity are nearby. The effect is very small. (2% change in elastic cross section of d + 208Pb (αd=0.70 fm3), Similar effect
expected for 7Li + 208Pb (α7Li =0.018-0.048 fm3).
Introduction
Beam :- 7Li Target :- enriched 208Pb (on Carbon backing) Beam energies :- E7Li
= 18-28 MeV
(All energies below Coulomb Barrier)
Experimental Details
T4: + 1600
T2: - 400
T1: + 400
FC
208PbT3: - 1600
7Li Beam
1 1 2 2
1 1 2 2
( , ). ( , ) ( , ). ( , )( )
( , ). ( , ) ( , ). ( , )
F F B BL L R R L L R R
B B F FL L R R L L R R
C E C E C E C ER E
C E C E C E C E
CDCC Calculation Details The diagonal and coupling potentials calculated using cluster folding method,
4 3( ) ( ) ( )
7 7if f t iV R r V R r V R r r
R – 7Li - target separation r - separation between clusters. Continue……
R
r
t208Pb
V
Vt
A value of DP found from a precise measurement of elastic scattering data to be, = 0.045 fm3
Loosely bound unstable nuclei (e.g. 6He, 11Li, 11Be) DP effect more important.
V. V. Parkar et al.,Phys. Rev. C (Rapid Com.), 78, 021601R (2008)
( 1, . . )8
900
B E g s n
E Enn
Polarizability parameter
Future prospective at ISOLDEReactions with 8,9,11Li and 7,10,11,12,14Be on similar targets to study complete reaction dynamics and compare with existing 6,7Li and 9Be data
Dipole polarizability studies for number of nuclei
GLORIA Array @
UHU, Spain
Team Members
S. Kailas, A. Chatterjee, S. Santra, A. Shrivastava, K. Mahata, K. Ramachandran, V. Jha, B. J. Roy,
S. K. Pandit, P. K. RathNuclear Physics Division, BARC, Mumbai
V. Nanal, R. G. Pillay, R. PalitDNAP, TIFR, Mumbai