Projectile Fragmentation Projectile Fragmentation at the Fragment Separatorat the Fragment Separator

Andreas HeinzAndreas HeinzWright Nuclear Structure Laboratory, Wright Nuclear Structure Laboratory,

Yale UniversityYale University

for the for the CHARMSCHARMS CollaborationCollaboration

Symposium on 30 Years of Projectile Fragmentation, ACS meeting, San Francisco, September 10-11, 2006

CHARMSCHARMSCCollaboration for ollaboration for HHighigh--AAccuracy Experiments on Nuclear ccuracy Experiments on Nuclear RReaction eaction

MMechanisms with Magnetic echanisms with Magnetic SSpectrometerspectrometersP. ArmbrusterP. Armbruster11, A. , A. BacquiasBacquias11, , L. GiotL. Giot11, V. Henzl, V. Henzl1,121,12, D. Henzlova, D. Henzlova1,121,12, A. Keli, A. Kelićć11, S. , S. LukićLukić11, , R. PleskaR. Pleskačč11, ,

M.V. RicciardiM.V. Ricciardi11, , K.K.--H. SchmidtH. Schmidt11, O. Yordanov, O. Yordanov11, J. Benlliure, J. Benlliure22, J. Pereira, J. Pereira2,122,12, E. Casarejos, E. Casarejos22, M. , M. FernandezFernandez22, T. Kurtukian, T. Kurtukian22, C., C.--O. BacriO. Bacri33, M. Bernas, M. Bernas33, L. Tassan, L. Tassan--GotGot33, L. Audouin, L. Audouin33, C. St, C. Stééphanphan33, ,

A. BoudardA. Boudard44, S. Leray, S. Leray44, C. Volant, C. Volant44, C. Villagrasa, C. Villagrasa44, B. Fernandez, B. Fernandez44, J., J.--E. DucretE. Ducret44, J. Ta, J. Taïïebeb55, C. , C. SchmittSchmitt66, B. Jurado, B. Jurado77, F. Reymund, F. Reymund88, P. Napolitani, P. Napolitani88, D. Boilley, D. Boilley88, A. Junghans, A. Junghans99, A. Wagner, A. Wagner99, A. , A.

KuglerKugler1010, V. Wagner, V. Wagner1010, A. Krasa, A. Krasa1010, A. Heinz, A. Heinz1111, P. Danielewicz, P. Danielewicz1212, L. Shi, L. Shi1212, T. Enqvist, T. Enqvist1313, K. , K. HelariuttaHelariutta1414, A. Ignatyuk, A. Ignatyuk1515, A. Botvina, A. Botvina1616

11GSI, Darmstadt, GermanyGSI, Darmstadt, Germany22Univ. Santiago de Univ. Santiago de CompostelaCompostela, , SantSant. de . de CompostelaCompostela, Spain, Spain

33IPN IPN OrsayOrsay, , OrsayOrsay, France, France44DAPNIA/SPhN, CEA DAPNIA/SPhN, CEA SaclaySaclay, Gif , Gif sursur Yvette, FranceYvette, France

55DEN/DMS2S/SERMA/LENR, CEA DEN/DMS2S/SERMA/LENR, CEA SaclaySaclay, Gif , Gif sursur Yvette , FranceYvette , France66IPNL, IPNL, UniversiteUniversite Lyon, Lyon, GroupeGroupe MaterieMaterie NucleaireNucleaire 4, Villeurbanne, France4, Villeurbanne, France

77CENBG, CENBG, BordeauBordeau--GradignanGradignan, France, France88GANIL, Caen FranceGANIL, Caen France

99Forschungszentrum Forschungszentrum RossendorfRossendorf, Dresden, Germany, Dresden, Germany1010Nuclear Physics Institute, Nuclear Physics Institute, RezRez, Czech Republic, Czech Republic

1111Wright Nuclear Structure Laboratory, Yale University, New Haven,Wright Nuclear Structure Laboratory, Yale University, New Haven, USAUSA1212NSCL and Physics and Astronomy Department, Michigan State UniverNSCL and Physics and Astronomy Department, Michigan State University, East Lansing, USAsity, East Lansing, USA

1313CUPP Project, CUPP Project, PyhasalmiPyhasalmi, Finland, Finland1414Univeristy of Helsinki, Helsinki, FinlandUniveristy of Helsinki, Helsinki, Finland

1515IPPE IPPE ObninskObninsk, Russia, Russia1616Institute for Nuclear Research, Russian Academy of Sciences, MosInstitute for Nuclear Research, Russian Academy of Sciences, Moscow, Russiacow, Russia

TopicsTopics

Basic researchBasic research::

Momentum dependence of the nuclear mean field (Talk of V. Henzl)Momentum dependence of the nuclear mean field (Talk of V. Henzl)Thermal instabilities of nuclear matter (Talk of D. Henzlova)Thermal instabilities of nuclear matter (Talk of D. Henzlova)Dissipation in Nuclear Matter Dissipation in Nuclear Matter Very asymmetric fissionVery asymmetric fissionStructure effects in fission and fragmentationStructure effects in fission and fragmentationNuclide production in fragmentation and fission (Talk of J. BenlNuclide production in fragmentation and fission (Talk of J. Benlliure)liure)

ApplicationsApplications::Nuclear astrophysicsNuclear astrophysicsSpin, alignment and polarisation in fragmentationSpin, alignment and polarisation in fragmentationTransmutation of nuclear wasteTransmutation of nuclear wasteNuclear safetyNuclear safetyProduction of secondary beams (RIA, FAIR)Production of secondary beams (RIA, FAIR)

The HeavyThe Heavy--Ion Synchrotron at GSIIon Synchrotron at GSIBeams from p to 238U Energies of 1-2 A GeV

The The FRagmentFRagment Separator FRSSeparator FRS

x2, x4 Bρt2, t4 velocity

flight path

x2, t2

↑x4, t4

beam monitortarget

scintillator

scintillator

ionisationchamber

ionisationchamber

beam

Z / ∆Z ≈ 200

A / ∆A ≈ 400

∆(βγ)/βγ ≈ 5·10-4

M.V. Ricciardi, PhD thesis

238U+Ti at 1 A GeV

Two “natural” observables:

Momentum distributions

Cross sections

Projectile FragmentationProjectile FragmentationTwo different time scales for abrasion and ablation →

(at least) a two-step process!

Abrasion AblationBreak-up

Abrasion of nucleons in a peripheral collision produces excited Abrasion of nucleons in a peripheral collision produces excited CN CN ((prefragmentprefragment).).

high <E*high <E*> > ≈≈ 27 27 MeVMeV per abraded nucleon per abraded nucleon DeDe--excitation through particle evaporation (excitation through particle evaporation (n,pn,p,,αα)) or fissionor fission(relatively) low angular (relatively) low angular momentamomenta (listen tomorrow to Z. Podolyak)(listen tomorrow to Z. Podolyak)

Momentum DistributionsMomentum DistributionsBi208-193

83

Nucleon excitation in projectile fragmentation

1H(208Pb,208Bi)x at 1 A GeV2H(208Pb,208Bi)x at 1 A GeV

Velocity of 208Bi in the frame of the 208Pb projectile.

A. 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 + π-)Probability for ∆ excitation and energy in the nuclear medium can be deduced.

Measured Nuclide Production in Fragmentation and Measured Nuclide Production in Fragmentation and InIn--flight Fissionflight 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 developmentData available at: http://www-w2k.gsi.de/charms/data.htm

ExperimentExperiment

Total Kinetic Energy (TKE) distributionCharge distribution

Two Reaction MechanismsTwo 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!

Experimental Information on Fission Experimental Information on Fission at low Eat low E**

E*-Bf < 10 MeV

E. Konecny et al., Proc. Third IAEA Symp. Phys. Chem. Fission Vol 2, 1974, p. 3

A lot of new data!

Transition from Symmetric to Transition from Symmetric to Asymmetric FissionAsymmetric Fission

Data resulted in:

o improved models for yield calculations

o better understanding of low-energy fission: evolution of fission channels, influence of pairing, …

GSI code ABLA GSI code ABLA -- Examples lowExamples low--energy reactionsenergy reactions

Excitation function and A- and Z- distributions:

Dissipation and Dissipation and Nuclide Nuclide

Production Production

J. Taïeb et al.

Dissipation and Nuclear FissionDissipation and Nuclear Fission

Collective motion converts into“heat” due to friction

Junior researcher

Potential difference

Collective motion

Deformation

Energy

Compound Nucleus

Saddle point

ScissionGround state

Fiss

ion

barr

ier

What does this have to do with nuclear fission?

τCN-Saddle

τSaddle-Scission

Dissipation and the Saddle Point Dissipation and the Saddle Point TemperatureTemperature

Deformation

Ene

rgy

Compound Nucleus

Saddle point

Ground state

∆E

If there is any dissipation τneutron < τfission → mneutron and ∆E get larger

→ Tsaddle is smaller

Reminder: the connection between temperature and excitation energy

Level density parametera

ETnuc

*

=τCN-Saddle

τSaddle-Scission

Charge Width as a ThermometerCharge Width as a Thermometer

Asymmetric mass split

Symmetric mass split

Asymmetric mass split

From: Bjornholm, Lynn; Rev. Mod. Phys. 52, 725 (1980)

Mass asymmetry η

Pote

ntia

l Population

2

2

2

2

2

fissA

saddle

fiss

fissZ

dVd

TAZ

η

σ ⎟⎟⎠

⎞⎜⎜⎝

⎛=

238U @ 1 A GeV on 9Be

First Results

Model description fails for deformed projectiles

→ influence of “initial” deformation on dissipation in nuclear fission

Spherical

Deformed

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)

GSI code ABLA GSI code ABLA –– Examples for highExamples for high--energy energy reactionsreactions

Experiment Calculation

The Future: RThe Future: R33BB

Measure:

Charge AND Mass of projectile and fission fragments

Neutrons

Gammas

Cross sections

Exclusive experiments AND high resolution

Future (Part II): ElectronFuture (Part II): Electron--Ion scattering in a Ion scattering in a Storage Ring (Storage Ring (eAeA ColliderCollider) ) ELISeELISe

• 125-500 MeV electrons• 200-740 MeV/u RIBs

• achievable luminosity: 1025-1029 cm-2s-1

depending on ion species

- spectrometer setup at theinteraction zone

- detection system for RI inthe arcs of the NESR (see EXL)

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