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

2. CHARMS Collaboration 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. The FRagment Separator FRS
M.V. Ricciardi, PhD thesis
238U+Ti at 1 A GeV
Z / Z  200
A / A  400
()/  5·10-4
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, (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:

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
Collective motion converts into “heat” due to friction
Ground state
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 Exclusive experiments AND high resolution 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
MeV electrons
MeV/u RIBs
achievable luminosity:
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!