ANGULAR MOMENTUM POPULATION IN FRAGMENTATION REACTIONS

Transcription

1 IoP Nuclear Physics Conference 2009 ANGULAR MOMENTUM POPULATION IN FRAGMENTATION REACTIONS Ana M. Denis Bacelar

2 OUTLINE Physics motivation Theory Previous results Experimental set-up Results High spin states Isomeric ratios Conclusions

3 MOTIVATION Extend the knowledge in the neutron-rich N~126 region Study of the reaction mechanism of fragmentation measuring the population of states with high angular momentum in the neutrondeficient N~126 region ( Surrey Data analysis by Nawras Al-Dahan (U. Settings around 212 Rn, 210 Th, 214 Th S347 experiment, GSI

4 THEORY: Abrasion-ablation model Fragmentation reactions: 2 steps Abrasion: collision between projectile and target ( s prefragment formed ( U 9 Be prefragment ablation ( s Ablation: nucleons evaporated final fragment ( Th, 212 Rn

5 ( P(I THEORY: Abrasion-ablation model ( stage Angular momentum distribution: ABRABLA code (abrasion IP 21 I II 1 exp 2 f 2 f 2 p f p f 1 A A AAAA 3/2 p 2 2 f p I m Spin-cutoff parameter where A f and A p are the masses of the fragment and the initial projectile th I m P ( I) di I I m J.-J. Gaimard and K.-H. Schmidt, Nucl. Phys. A 531 (1991) 709 M. De Jong, A.V. Ignatyuk and K.-H. Schmidt, Nucl. Phys. A 613 (1997) 435

6 EXPERIMENTALLY We can calculate the probability that in a reaction a nucleus is produced in an isomeric state ( R ) Isomeric ratios R exp N N isomer total We expect: R exp 1 I m th M. Pfützner et al, Phys. Rev. C 65 (2002)

7 PREVIOUS EXPERIMENTS Zs. Podolyak et al, Phys. Rev. Lett. 632 (2006) 203

8 PREVIOUS EXPERIMENTS Experimental results contradict the model An additional source of angular momentum has to be considered Collective contribution Angular momentum abrasion + ablation stage S. Pal and R. Palit Phys. Lett. B 665 (2008) 164 Zs. Podolyak et al, Phys. Rev. Lett. 632 (2006) 203 Better agreement for high spin states

9 EXPERIMENTAL SET-UP Accelerator SIS provides a 1 GeV/u 238 U beam with an intensity of 10 5 pps ( sections (high cross Projectile fragmentation on Be target The ions are separated and identified in the FRS

10 EXPERIMENTAL SET-UP Identification in mass and charge in the FRS: β A B 238 U SC21 TOF SC41 Q ( Be ( 9 Stopper Dipoles Bρ sci43 2 ΔE ~ Z sci42

11 counts counts counts S4 position RESULTS: High-spin states in At isotopes At / s E (kev) At s ns AoQ 39/ s 211At E (kev) E (kev)

12 1258 (55/2 + ) counts 138 counts counts 119 S4 position RESULTS: High-spin states in Rn isotopes Rn /2-960 ns 63/2-201 ns??? E (kev) AoQ ns ns??? ns??? 212Rn /2+ 1 μs / μs / ns??? Rn E (kev) E (kev)

13 counts S4 position RESULTS: High-spin states in 213 Rn Highest spin populated in a fragmentation reaction!!! 20 d e m o d e m o d e m o d e m o d e m o 213Rn d e m o d e m o d e m o d e m o d e m o 55/ ns??? d e m o d e m o d e m o d e m o d e m o AoQ d e m o d e m o d e m o d e m o d e m o 8 d e m o d e m o d e m o d e m o d e m o 4 d e m o d e m o d e m o d e m o d e m o d e m o d e m o d e m o d e m o d e m o E (kev)

14 RESULTS: Isomeric ratios Nucleus I R exp ρ th R exp / ρ th 209 At 29/ At At 39/

15 CONCLUSIONS Data analysis is going on! Several high-spin states were populated Test of fragmentation theories Useful for production of RIB s at high-spin 215 Ra 209 At 29/ Ra 211 At 39/ At Rn 55/

16 THANK YOU! A.M. Denis Bacelar, 1 A.M. Bruce, 1 Zs. Podolyák, 2 S. Lalkovski, 1 S. Pietri, 3 N. Al- Dahan, 2 M. Górska, 3 A. Algora, 4 N. Alkhomashi, 2 J. Benlliure, 5 P. Boutachkov, 3 A. Bracco, 10 E.Calore, 7 E. Casarejos, 5 I.J. Cullen, 2 A.N. Deo, 2 P. Detistov, 6,9 Z. Dombradi, 12 C. Domingo-Pardo, 3 M. Doncel, 6 F. Farinon, 3 G.F. Farrelly, 2 H. Geissel, 3 W. Gelletly, 2 J. Gerl, 3 N. Goel, 3 J. Grebosz, 3,8 R. Hoischen, 14 I. Kojouharov, 3 S. Leoni, 10 F. Molina, 4 A.I. Morales, 5 D. Montanari, 10 A. Musumarra, 11 R. Nicolini, 10 D.R. Napoli, 7 C. Nociforo, 3 A.Prochazka, 3 P.H. Regan, 2 B. Rubio, 4 D. Rudolph, 14 S. Vermas, 5 S.J. Steer, 2 P.Strmen, 13 T.P.D. Swan, 2 I. Szarka, 13 J.J. Valiente-Dobón, 7 P.M. Walker, 2 H. Weich, 3 H.J. Wollersheim 3 1 School of Environment and Technology, University of Brighton, Brighton BN2 4GJ, UK 2 Department of Physics, University of Surrey, Guildford GU2 7XH, UK 3 GSI, Planckstrasse 1, D-64291, Darmstadt, Germany 4 Instituto de Física Corpuscular, Universidad de Valencia, E-46071, Spain 5 Universidad de Santiago de Compostela, E-15706, Santiago de Compostela, Spain 6 Laboratorio de Radiaciones Ionizantes, Universidad de Salamanca, E-37008, Spain 7 INFN-Laboratori Nazionali di Legnaro, Italy 8 The Henryk Niewodniczánski Institute of Nuclear Physics, PL , Kraków, Poland 9 St. Kliment Ohridsky University of Sofia, 1164 Sofia, Bulgaria 10 University of Milan 11 INFN - Laboratori Nazionali del Sud, via S.Sofia 62, Catania, Italy 12 Institute of Nuclear Research of the Hungarian Academy of Sciences, P.O. Box 51, Debrecen, H-4001, Hungary 13 Bratislava Faculty of Mathematics and Physics, Comenius University, Bratislava, Slovak Republic 14 Department of Physics, Lund University, S Lund, Sweden