projectile fragmentation at the fragment separator · projectile fragmentation at the fragment...
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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
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 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!