GOSIA as a tool for COULEX on exotic beams Katarzyna Wrzosek
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Transcript GOSIA as a tool for COULEX on exotic beams Katarzyna Wrzosek
GOSIA
as a tool for COULEX
on exotic beams
Katarzyna Wrzosek
Heavy Ion Laboratory
Warsaw University
EWON Workshop, Prague, 10-12 May 2007
LOW - ENERGY COULOMB
EXCITATION:
Well-established method to study collective
excitations in nuclei.
Purely electromagnetic the only nuclear
properties involved are the matrix elements
of the electromagnetic multipole moments.
EWON Workshop, Prague, 10-12 May 2007
208Pb
Gamma ray spectrometer
EXOGAM – up to 11 segmented Ge clovers (90 and 135)
Particle detector
CD-detector - annular, highly segmented double silicon strip detector
(DSSD)
covered angles: 23,8-54,5 in the LAB ≡ 24-145 in the C.M. frame
EWON Workshop, Prague, 10-12 May 2007
COULEX Analysis Scheme
Measured
yields
Level scheme
available
spectroscopic
data
(, BR, )
Experimental
setup geometry:
particle and
detectors
MINIMALIZATION
PROCEDURE
Errors estimation
GOSIA
set of matrix
elements
Quadrupole
rotational invariant
sum rules
shape parameters
for individual
states
EWON Workshop, Prague, 10-12 May 2007
SIGMA
GOSIA
GOSIA is a Rochester – Warsaw semiclassical coupledchannel Coulomb excitation least-squares search code.
Developed in early eighties by
T. Czosnyka, D. Cline, C.Y.Wu
and continuously upgraded to fulfill requirements of new
experiments.
Used extensively for Coulomb excitation studies of a wide
range of nuclei.
Typical use of GOSIA:
1.
Fitting of the matrix elements to the experimental data.
2.
Simulation of the experiments:
to predict which - ray will be observed
to check to what extent the observation will depend on
individual matrix elements.
EWON Workshop, Prague, 10-12 May 2007
AN EXAMPLE:
COULOMB EXCITATION OF 74,76Kr @ GANIL
Coulomb excitation is the only method that can
directly distinguish between different shapes of the
nucleus
ideally suited to verify the shape coexistence
scenario in the Kr isotopes.
Shape parameters of the two lowest 0+ states in 74Kr
and 76Kr nuclei were inferred from coulomb
excitation data.
The Coulomb excitation analysis were performed
using the last squares fitting code GOSIA.
EWON Workshop, Prague, 10-12 May 2007
EXPERIMENTS (SPIRAL @ GANIL)
508 keV
770 keV
74Kr
74Kr
76Kr
76Kr
+ 208Pb
(5·105 pps, 4.7·A MeV)
+ 208Pb
(106 pps, 4.4·A MeV)
E. Clement et al., submitted to Phys Rev C
EWON Workshop, Prague, 10-12 May 2007
76 Kr
76Kr
39.5° - 49.0°
61.4° - 71.8°
71.0° - 87.7°
EWON Workshop, Prague, 10-12 May 2007
107.0° - 121.5°
RESULTS
EWON Workshop, Prague, 10-12 May 2007
QUADRUPOLE ROTATIONAL
INVARIANT SUM RULES
model independent description of the nuclear shape
is based on a fact, that scalar products of E2
operators are rotational invariants.
Operator products may be expressed using the
intermediate state expansion formula:
EWON Workshop, Prague, 10-12 May 2007
QUADRUPOLE ROTATIONAL INVARIANT
SUM RULES
model independent description of the nuclear shape
To get information on triaxiality the higher order
invariant is needed:
EWON Workshop, Prague, 10-12 May 2007
RESULTS
The deformation of the 0+1 is very similar in 74Kr and 76Kr.
Triaxiality parameter:
the ground state of 76Kr is prolate, while the 0+2 state has an triaxial
shape.
Both, the ground state and the 0+2 state of 74Kr are triaxial, but with
different parameter.
EWON Workshop, Prague, 10-12 May 2007
Collaboration of 74,76Kr Project
CEA Saclay, France
E.Clément
A.Görgen
W.Korten
E.Bouchez
A.Chatillon
A.Hürstel
Y.Le Coz
A.Obertelli
Ch.Theisen
J.N.Wilson
CEA/DIF, France
J.-P. Delaroche
M.Girod
H.Goutte
S.Péru
GANIL, Caen, France
J.M.Casandjian
G. de France
HIL Warsaw, Poland
T.Czosnyka
J.Iwanicki (OLL, Liverpool)
P.J.Napiorkowski
M.Zielińska (CEA Saclay)
Oliver Lodge Lab., Liverpool, UK
C.Andreoiu
P.A.Butler
R.-D.Herzberg
D.G.Jenkins
G.D.Jones
Univ. Of Surrey, Guildford, UK
W.N.Catford
C.Timis
GSI, Darmstadt, Germany
F.Becker
J.Gerl
NBI, Copenhagen, Denmark
G.Sleten
EWON Workshop, Prague, 10-12 May 2007
List of the experiments
where GOSIA was recently used
ISOLDE (MINIBALL), CERN:
J. Cederkall – 108Sn, 110Sn
J. Iwanicki - 88Kr, 92Kr
A. Hurst - 70Se
I. Stefanescu – 68Cu, 70Cu
J. Van de Walle – 74Zn
GANIL (EXOGAM), FRANCE:
E. Bouchez – 76Kr
E. Clement – 74Kr
M. Zielińska – 44Ar
JYVASKYLA, FINLAND
F. Becker – 78Kr
JAEA, TOKAI, JAPAN:
M. Koizumi - 66Zn, 68Zn
T. Hayakawa – 78Se
A. Osa - 84Kr
Y. Toh – 70Ge
M. Zielińska – 96Mo
ANL (Gammasphere), USA
A.Hayes – 178Hf
Next experiments
ISOLDE (MINIBALL), CERN:
E. Clement – 96Sr
(Jul 2007)
P.Butler, P. Van Duppen (Aug 2007)
EWON Workshop, Prague, 10-12 May 2007
182,184Hg
JRA6
INTAG
Warsaw Coulomb Excitation Group
@ Heavy Ion Laboratory, Warsaw Univ.
Tomasz
Czosnyka
Julian Srebrny
Jędrzej Iwanicki
Paweł Napiorkowski
Magdalena Zielińska (CEA Saclay)
Katarzyna Wrzosek
Katarzyna Hadyńska (UAM, Poznań)
Daniel Piętak (PW, Warsaw)
EWON Workshop, Prague, 10-12 May 2007
Thank you
EWON Workshop, Prague, 10-12 May 2007