Projectile Fragmentation at the Fragment Separator

1. Projectile Fragmentation at the Fragment Separator Andreas Heinz Wright Nuclear Structure Laboratory, Yale University for the CHARMS Collaboration Symposiumon 30 Years of Projectile Fragmentation, ACS meeting, San Francisco, September 10-11, 2006

2. CHARMSCollaboration for High-Accuracy Experiments on Nuclear Reaction Mechanisms with Magnetic Spectrometers P. Armbruster1, A. Bacquias1, L. Giot1, V. Henzl1,12, D. Henzlova1,12, A. Kelić1, S. Lukić1, R. Pleskač1, M.V. Ricciardi1, K.-H. Schmidt1, O. Yordanov1, J. Benlliure2, J. Pereira2,12, E. Casarejos2, M. Fernandez2, T. Kurtukian2, C.-O. Bacri3, M. Bernas3, L. Tassan-Got3, L. Audouin3, C. Stéphan3, A. Boudard4, S. Leray4, C. Volant4, C. Villagrasa4, B. Fernandez4, J.-E. Ducret4, J. Taïeb5, C. Schmitt6, B. Jurado7, F. Reymund8, P. Napolitani8, D. Boilley8, A. Junghans9, A. Wagner9, A. Kugler10, V. Wagner10, A. Krasa10, A. Heinz11, P. Danielewicz12, L. Shi12, T. Enqvist13, K. Helariutta14, A. Ignatyuk15, A. Botvina16 1GSI, Darmstadt, Germany 2Univ. Santiago de Compostela, Sant. de Compostela, Spain 3IPN Orsay, Orsay, France 4DAPNIA/SPhN, CEA Saclay, Gif sur Yvette, France 5DEN/DMS2S/SERMA/LENR, CEA Saclay, Gif sur Yvette , France 6IPNL, Universite Lyon, Groupe Materie Nucleaire 4, Villeurbanne, France 7CENBG, Bordeau-Gradignan, France 8GANIL, Caen France 9Forschungszentrum Rossendorf, Dresden, Germany 10Nuclear Physics Institute, Rez, Czech Republic 11Wright Nuclear Structure Laboratory, Yale University, New Haven, USA 12NSCL and Physics and Astronomy Department, Michigan State University, East Lansing, USA 13CUPP Project, Pyhasalmi, Finland 14Univeristy of Helsinki, Helsinki, Finland 15IPPE Obninsk, Russia 16Institute for Nuclear Research, Russian Academy of Sciences, Moscow, Russia

3. Topics • Basic research: • Momentum dependence of the nuclear mean field (Talk of V. Henzl) • Thermal instabilities of nuclear matter (Talk of D. Henzlova) • Dissipation in Nuclear Matter • Very asymmetric fission • Structure effects in fission and fragmentation • Nuclide production in fragmentation and fission (Talk of J. Benlliure) • Applications: • Nuclear astrophysics • Spin, alignment and polarisation in fragmentation • Transmutation of nuclear waste • Nuclear safety • Production of secondary beams (RIA, FAIR)

4. The Heavy-Ion Synchrotron at GSI Beams from p to 238U Energies of 1-2 A GeV

5. 238U+Ti at 1 A GeV A / A  400 Z / Z  200 ()/  5·10-4 M.V. Ricciardi, PhD thesis The FRagment Separator FRS • Two “natural” observables: • Momentum distributions • Cross sections

6. Projectile Fragmentation Two different time scales for abrasion and ablation → (at least) a two-step process! Ablation Abrasion Break-up • Abrasion of nucleons in a peripheral collision produces excited CN (prefragment). • high <E*>  27 MeV per abraded nucleon • De-excitation through particle evaporation (n,p,) or fission • (relatively) low angular momenta (listen tomorrow to Z. Podolyak)

7. Momentum Distributions Nucleon excitation in projectile fragmentation 1H(208Pb,208Bi)x at 1 A GeV 2H(208Pb,208Bi)x at 1 A GeV Velocity of 208Bi in the frame of the 208Pb projectile. • Kelić et al., PRC 70, 064608 (2004) • Two components can be distinguished: • Quasi-elastic scattering (p replaces n in 208Pb) • (1232) excitation (e.g. n 0  p + -) • Probability for  excitation and energy in the nuclear medium can be deduced.

8. Measured Nuclide Production in Fragmentation and In-flight Fission For heavy projectile fission opens up as a decay channel → knowledge of the fission properties of unstable heavy nuclei is necessary Excellent basis for model development Data available at: http://www-w2k.gsi.de/charms/data.htm

9. Experiment Total Kinetic Energy (TKE) distribution Charge distribution

10. Two Reaction Mechanisms Plastic: only nuclear-induced fission Pb: nuclear and electromagnetic-induced fission Nuclear: ZCN = Z1 + Z2 Electromagnetic: ZCN = Z1 + Z2 → trigger for low excitation energies!

11. Experimental Information on Fission at low E* E*-Bf < 10 MeV A lot of new data! E. Konecny et al., Proc. Third IAEA Symp. Phys. Chem. Fission Vol 2, 1974, p. 3

12. Transition from Symmetric to Asymmetric Fission • Data resulted in: • improved models for yield calculations • better understanding of low-energy fission: evolution of fission channels, influence of pairing, …

13. GSI code ABLA - Examples low-energy reactions Excitation function and A- and Z- distributions:

14. Dissipation and Nuclide Production J. Taïeb et al.

15. Dissipation and Nuclear Fission Compound Nucleus Saddle point Collective motion Junior researcher Energy Potential difference Fission barrier Ground state Collective motion converts into “heat” due to friction Scission Deformation What does this have to do with nuclear fission? τCN-Saddle τSaddle-Scission

16. Dissipation and the Saddle Point Temperature Compound Nucleus Saddle point ΔE Energy If there is any dissipation τneutron < τfission → mneutron and ΔE get larger → Tsaddle is smaller Reminder: the connection between temperature and excitation energy Ground state Deformation Level density parameter τCN-Saddle τSaddle-Scission

17. Charge Width as a Thermometer Asymmetric mass split Symmetric mass split Asymmetric mass split Population Potential Mass asymmetry η From: Bjornholm, Lynn; Rev. Mod. Phys. 52, 725 (1980)

18. First Results 238U @ 1 A GeV on 9Be Deformed Spherical Model description fails for deformed projectiles → influence of “initial” deformation on dissipation in nuclear fission

19. Fine structure in residue yields after violent nuclear collisions Caution when interpreting nuclide yields with thermodynamic approaches without nuclear structure! M.V. Ricciardi et al., NPA 733, 299 (2004)

20. GSI code ABLA – Examples for high-energy reactions Experiment Calculation

21. The Future: R3B • Measure: • Charge AND Mass of projectile and fission fragments • Neutrons • Gammas • Cross sections Exclusive experiments AND high resolution

22. Future (Part II): Electron-Ion scattering in a Storage Ring (eA Collider) ELISe • 125-500 MeV electrons • 200-740 MeV/u RIBs • achievable luminosity: • 1025-1029 cm-2s-1 depending on ion species • spectrometer setup at the • interaction zone • detection system for RI in • the arcs of the NESR (see EXL)

23. Conclusions • A lot of progress in the understanding of projectile fragmentation. • Heavy beams and high resolution spectrometers are excellent tools. • Don’t forget the influence of nuclear structure and nucleonic exciations. • A wealth of new data from projectile fragmentation, spallation, in-flight fission and fission of secondary beams allowed for the development of realistic models with predictive power. • Applications in accelerator driven systems, nuclear astrophysics, ... • The future looks bright!