Coulomb excitation of the presumably super-deformed band in 42Ca

- preliminary results from the first AGATA Demonstrator experiment

Katarzyna Hadyńska-Klęk1

F. Azaiez3, A. Maj2, P. Napiorkowski1

and the AGATA collaboration*

* Univ. Ankara, Turkey; Univ. Bonn, Germany; NIPNE Bucharest, Romania; Univ. Brighton, UK; GANIL, Caen, France; Univ. Camerino, Italy; NBI Copenhagen, Danmark; Univ. Cracow, Poland;

STFC Daresbury, UK; GSI Darmstadt, Germany; TU Darmstadt, Germany; INFN Firenze, Italy; INFN Genova, Italy; Univ. Göteborg, Sweden; FZ Jülich, Germany; Univ. Jyväskylä, Finland; Univ. Keele, UK; Univ. Köln, Germany; IFJ PAN Krakow, Poland; INFN Legnaro, Italy; Univ. Liverpool, UK; Univ. Istanbul, Turkey; IPN Lyon, France;

Univ. Lund, Sweden; Univ. Manchester, UK; INFN/Univ. Milano, Italy; LMU München, Germany; TU München, Germany; INFN Napoli, Italy; CSNSM Orsay, France; IPN Orsay, France; INFN/Univ. Padova, Italy;

Univ. Paisley, UK; INFN Perugia, Italy; CEA Saclay, France, Dapnia; Univ. Sofia, Bulgaria; KTH Stockholm, Sweden; IPHC Strasbourg, France; Univ. Surrey, UK; IPJ Swierk, Poland; Univ. of Warsaw, Poland; Univ. Uppsala,

Sweden; Univ. York, UK

17th Nuclear Physics Workshop "Marie & Pierre Curie” Kazimierz 2010

Motivation - 40Ca

• Highly colective structure found in 40Ca

• B(E2; 4+→ 2+ in SD) = 170 W.u (DSAM)

||

Deformation of the 2+ state in the superdeformed band: β2=0.59(9)

(E. Ideguchi et al., Phys. Rev. Lett. 87

2001)

42Ca 40Ca

• Highly collective structure were found in the A~40 region (40Ca, 36,38Ar)

• B(E2) values in 42Ca suggest smaller deformation of the of the 0+(1837 keV) band than in the case of 40Ca

• observation of GDR feeding of presumably deformed band in 42Ca from very deformed hot 46Ti (M.Kmiecik et al. Acta Phys. Pol. B36, 1169(2005)) - (SD bands preferential feeding by the low energy component of the highly split GDR decaying?)

• moment of inertia very similar to that found for the SD-band in 40Ca

40Ca vs 42Ca

42Ca

First experiment with AGATA Demonstrator @ LNL Legnaro

AIMS OF THE EXPERIMENT:

to proof the possibility of Coulomb excitation of highly deformed bands in A~40 region nuclei,

to determine the B(E2) values for low spin part of the presumable super-deformed band in 42Ca,

to expand the knowledge about the electromagnetic properties of low-laying states in 42Ca,

to determine quadrupole moments for the both ground state and SD bands.

IN ADDITION

the response of the AGATA Demonstrator for low multiplicity gamma rays in a wide energy range 300 – 2500 keV,

the coincidence mode of DAQ with particle detector connected via AGAVA interface

the Doppler correction of a detected gamma rays in quasielastic kinematic.

First physical experiment with AGATA Demonstrator @ LNL Legnaro

beamtime: 18-23.02.2010 beam: 42Ca, 170 MeV targets:

208Pb, 1 mg/cm2 , 197Au, 1 mg/cm2 (tests + setting up)

DANTE: 3 MCP detectors covered θ range 100°-144° AGATA: 3 clusters at 143.8 mm from the target particle – γ coincidence mode: trigger rate 150÷250 Hz

Observed decay scheme of 42Ca

Ca42

E [keV]

Possible scenario #1

• Excitation via E2(01+ → 21

+) and E3(21

+→ 1-) transitions

• Deexcitation via E1(1- → 02+ ) 2048 keV

• GOSIA calculations: B(E3; 21

+→ 1-) > 2.5*106 W.u.

• This scenario has to be excluded

E2

E3

E1

Ca42

Possible scenario #2

• We assume that the observed gamma line comes from a 2+ level placed at 2048 keV.

• The 22+ state can be populated directly

via E2(01+ → 22

+)

• Deexcitation – through E2(22+ → 01

+) 2048 keV

• It was enough to reproduce the intensity of the 2048 keV gamma ray with B(E2; 22

+ → 01+) ~ 1 W.u only

Another surprising effect

In multi-step Coulex each additional step leads to a weaker excitation → we expected more counts in the 2424 keV line than in the 1729 keV transition

In the experiment, the 1729 keV line is stronger!

Expected ratio:

1729 keV : 2424 keV = 1 : 2

Obtained ratio:

1729 keV : 2424 keV = 44 : 3 !

It seems that the 42+ state is populated

stronger that the 22+ in the same band

Excitation of the presumably SD band is smaller then it was expected from calculations

Ca42

Summary

Preliminary results from the Coulomb excitation of the 42Ca - first physical experiment using AGATA Demonstrator

Coulomb excitation of the levels up to 4+ states in the GS band and presumably SD band in 42Ca was observed

A very strong 2048 keV transition was observed → probably another 2+ state found

Special thanks to:

D. Bazzacco4, E. Farnea4, G. de Angelis4, D. Bartolato4, P.Bednarczyk2, M.Bellato4, G. Benzoni6, L. Berti6, B. Bruyneel10, F. Camera6, M.Ciemała2,

P.Cocconi4, A. Colombo4, A. Corsi6, F. Crespi6, A. Czermak2, B.Dulny2, B.Fornal2, S. Franchoo3, A. Gadea4, A. Gottardo4, A.K. Gourishetty2,

X. Grave3, J. Grębosz2, M. Gulmini6, R. Isocrate4, G. Jaworski1, M.Kicinska-Habior1, M. Kmiecik2, N. Kondratyev4, A. Korichi5, W.Korten8, G. Lehaut7, S. Lenzi4, S.Leoni6, S. Lunardi4, G. Maron6, R.Menegazzo4, D.Mengoni4, E. Merchan11, W. Męczyński2, C. Miechelagnoli4, P. Molini4,

D.Napoli4, R. Nicolini6, M. Niikura3, M. Palacz1, G.Rampazzo4, F. Recchia4, N. Redon7, P. Reiter10, D. Rosso4, E. Sahin4, J.Srebrny1, I. Stefan3,

O.Stezowski7, J. Styczeń2, N. Toniolo4, C.A. Ur4, V.Vandone6, B.Wadsworth9, A. Wiens10, K. Wrzosek-Lipska1, M. Zielińska1, M.Ziębliński2

1University of Warsaw, Poland; 2IFJ PAN Kraków, Poland; 3IPN Orsay, France; 4 INFN, Legnaro and University of Padova, Italy; 5CSNSM Orsay France; 6Universita’ di Milano and INFN sezione di

Milano, Italia; 7 IPN Lyon, France; 8CEA Saclay, France; 9University of York, UK; 10University of Cologne, Germany 11GSI Darmstadt, Germany

Towsley, Cline, Horoshko @

Pulse Shape Analysisto decompose

recorded waves

Highly segmented HPGe detectors

·

·

Reconstruction of tracks evaluating permutations

of interaction points

Digital electronicsto record and

process segment signals

1

23

4

Reconstructed gamma-rays

AGATA - Ingredients of Gamma–Ray Tracking

Gamma energy without Doppler correction

Gamma energy Doppler corrected

5% 2%

First gamma spectrum