High-resolution experiments on nuclear fragmentation at the FRS at GSI M. Valentina Ricciardi GSI Darmstadt, Germany

Outline CHARMS Collaboration for High-Accuracy experiments on nuclear Reaction Mechanisms with magnetic Spectrometers (15 min) High-resolution experiments on nuclear fragmentation: two results on properties of nuclear matter (15min) Applications to nuclear technology (5min)

PART 1 CHARMS Collaboration for High-Accuracy experiments on nuclear Reaction Mechanisms with magnetic Spectrometers

At GSI, Darmstadt, availability of: - ion beams at relativistic energy (SIS) - high-resolution magnetic spectrometer (FRS) The idea behind the CHARMS collaboration The idea: to study spallation and fragmentation reactions in inverse kinematics

A/Z from time and position: Z from IC: Once mass and charge are identified (A, Z are integer numbers) the velocity is measured from B  : Our tool: the high-resolution magnetic spectrometer FRS Resolution: very precise measurement

The high-quality experimental outcomes - full identification (A, Z)  extremely precise production cross-sections - absolute velocity from B   extremely precise velocity spectra 136 Xe(1 A GeV)+Pb Z=15 N=16 x constant see talk of Paolo Napolitani Limited acceptance: - in magnetic rigidity: combine several B  settings to cover all A/Z and velocities - in angle: only a part of the real production is measured.

Taïeb et al., NPA 724 (2003) 413 Ricciardi et al, PRC 73 (2006) Bernas et al., NPA 765 (2006) 197 Bernas et al., NPA 725 (2003) 213 Armbruster et al., PRL 93 (2004) Measured cross sections Measured velocities evaporation residues fission fragments Example: 1 A GeV 238 U on 1 H

Data accuracy: Statistic: below 3% Systematic: % About 15,000 production cross sections and velocity distributions for spallation, fragmentation and fission products measured! Experimental data available at: ProjectileTargetEnergy [A GeV] 56 Fe 1,2 H, Ti0.3, 0.5, 0.75, 1, ,124 Sn 1 136,124 Xe 1,2 H, Ti, Be, Pb0.2, 0.5, Au 1 H, Ti, Be, Au0.5, 0.8, Pb 1,2 H, Ti, Be0.5, U 1,2 H, Ti, Be, Pb1 see talk of Sylvie Leray Performed experiments

Research performed by CHARMS Basic research: Nuclide production in fission, spallation, fragmentation Structural effects in fission and fragmentation More on fission: dynamics, evolution of channels Nuclear EOS (momentum dependence of the mean field) Nuclear phase transitions (isospin thermometer) Applications to other fields in physics: Fission barriers in nuclear astrophysics  -resonance and quasi-elastic scattering in charge-exchange reactions Applications to nuclear technology: Transmutation of nuclear waste Nuclear safety Production of secondary beams (secondary-beam facilities) code ABRABLA code INCL+ABLA Basic research: Nuclide production in fission, spallation, fragmentation Structural effects in fission and fragmentation More on fission: dynamics, evolution of channels Nuclear EOS (momentum dependence of the mean field) Nuclear phase transitions (isospin thermometer) Applications to other fields in physics: Fission barriers in nuclear astrophysics  -resonance and quasi-elastic scattering in charge-exchange reactions Applications to nuclear technology: Transmutation of nuclear waste Nuclear safety Production of secondary beams (secondary-beam facilities) code ABRABLA code INCL+ABLA

PART 2 High-resolution experiments on nuclear fragmentation: two results on the properties of nuclear matter

1 Profiting of the full A, Z identification of the fragments to investigate the liquid-gas coexistence

Evidence of phase-transition from the caloric curve Evidence based on the yields of very light isotopes Is there some equivalent signature in heavy residues?

Which signature can we expect from the liquid component? E ~ 27 MeV  A E spectator ~ 27 MeV  A 3 MeV/nucleon Most of the nuclides belong to the plateau E* ~ A FO E* = length of evaporation path. The evaporation path gets shorter and shorter and shifts the initial N/Z This is our "potential" signature

Note: the attractor line is always on the left of the stability line Sequential evaporation: is washing out all? attractor line  if the final fragments fall on the attractor line every indication of the liquid-gas coexistence is lost

Yes, we can profit of the full A, Z identification to investigate the liquid-gas coexistence This is the "footprint" of a caloric curve !

/Z in full nuclear charge range Residue corridor not reached: Cold residues preserve memory on the initial N/Z over the whole Z range (high excitation energies) 136 Xe 124 Xe  124 Xe+Pb 1 A GeV  136 Xe+Pb 1 A GeV D. Henzlova "SYMMETRY ENERGY OF FRAGMENTS PRODUCED IN MULTIFRAGMENTATION" D. Henzlova et al., arXiv nucl-ex/

The isospin thermometer method The idea: the mean N/Z-ratio of the final elements can be used in combination with statistical-model codes in order to deduce the freeze-out temperature after break up M. V. Ricciardi T. Enqvist

2 Profiting of the precise measurement of the velocity of the fragments to get information on the momentum dependence of the nuclear mean field

Morrissey systematic D. J. Morrissey, Phys. Rev. C 39 (1989) 460

124 Sn Sn T lab = 800 MeV/u b = 5 fm BUU calculations of mid-peripheral nucleus-nucleus collisions L. Shi, P. Danielewicz, R. Lacey, PRC 64 (2001) The spectators response to the participant blast

Experimental evidence of the spectators response to the participant blast M. V. Ricciardi T. Enqvist Fission events excluded

Velocity spectra Fission and fragmentation can be disentangled ! see talk of Paolo Napolitani

V. Henzl 197 Au Au 197 Au + 27 Al

1 A GeV 238 U + Pb V. Henzl T. Enqvist C.M. momentum seems to be selectively sensitive to the momentum dependence of the nuclear force

Note: in exp  b  estimated only for A frag >60 quantitative discrepancy between experiment and BUU 1 A GeV 196 Au Au

PART 3 Applications to nuclear technology

238 U + p at 1 A GeV Experimental data taken at the FRS at GSI Calculation: ABRABLA code (GSI)

Prediction based on the ABRABLA and EPAX codes, GSI. K.-H. Schmidt, Prediction of RIB production rates at FAIR

D. Ridikas et al Detection sensitivity. 0.1 g of nuclear material per ton of container Needed: delayed-neutron yields, fission fragments A and Z distributions. Non-destructive characterisation of weapon grade materials or nuclear waste

Conclusions The CHARMS group and collaboration: fission, spallation and fragmentation reactions at relativistic energies Ion beams + High-resolution magnetic spectrometer  two observables: production cross sections for all nuclei and velocity spectra Examples of research: Fragmentation cross sections of heavy fragments can give indication on the liquid-gas phase transition Velocity of fragmentation residues as an observable to study the nuclear mean field: The longitudinal momentum is measurable with the required precision with high-resolution magnetic spectrometers RIB, Nuclear safety, nuclear waste and other potential applications