High-resolution experiments on nuclear fragmentation at the FRS at GSI

M. Valentina Ricciardi

GSI Darmstadt, Germany

Outline

CHARMSCollaboration 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

CHARMSCollaboration for High-Accuracy experiments on nuclear

Reaction Mechanisms with magnetic Spectrometers

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

x2, x4 Bt2, t4 velocity

flight path

x2, t2

x4, t4

beam monitor

target

scintillator

scintillator

ionisationchamber

ionisationchamber

beam

2ZΔE

A/Z from time and position:

Z from IC:

βγ

Bρ

Z

A

cm

e

0

Once mass and charge are identified (A, Z are integer numbers) the velocity is measured from B:

BZ

Ac

0m

e

Our tool: the high-resolution magnetic spectrometer FRS

Resolution:34 1052AA40Z105 ./.B/ΔB

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

136Xe(1 A GeV)+Pb Z=15N=16x

con

sta

nt

see talk of P

aolo 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) 014607 Bernas et al., NPA 765 (2006) 197 Bernas et al., NPA 725 (2003) 213 Armbruster et al., PRL 93 (2004) 212701

Measured cross sections

Measured velocities

evaporation residues

fission fragments

Example: 1 A GeV 238U on 1H

Data accuracy:

Statistic: below 3%

Systematic: 9 - 15 %

About 15,000 production cross sections and velocity distributions for spallation, fragmentation and fission products measured!

Experimental data available at: www.gsi.de/charms/data.htm

Projectile Target Energy [A GeV]56Fe 1,2H , Ti 0.3, 0.5, 0.75, 1, 1.5112,124Sn 112,124Sn 1136,124Xe 1,2H, Ti, Be, Pb 0.2, 0.5, 1

197Au 1H , Ti, Be, Au 0.5, 0.8, 1208Pb 1,2H, Ti, Be 0.5, 1238U 1,2H, Ti, Be, Pb 1 see talk of Sylvie Leray

Performed experiments

Research performed by CHARMS

Basic research:Nuclide production in fission, spallation, fragmentationStructural effects in fission and fragmentationMore 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 wasteNuclear safetyProduction of secondary beams (secondary-beam facilities)

code ABRABLA

code INCL+ABLA

Basic research:Nuclide production in fission, spallation, fragmentationStructural effects in fission and fragmentationMore 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 wasteNuclear safetyProduction 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

Espectator ~ 27 MeV A

3 MeV/nucleon

Most of the nuclides belong to the plateau

E* ~ AFO

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

attra

ctor

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 !

<N>/Z in full nuclear charge range

Residue corridor not reached: Residue corridor not reached: Cold residues preserve memory Cold residues preserve memory on the initial on the initial NN//ZZ over the whole Z range (high excitation energies) over the whole Z range (high excitation energies)

136Xe

124Xe

124Xe+Pb 1 A GeV 136Xe+Pb 1 A GeV

D. Henzlova

"SYMMETRY ENERGY OF FRAGMENTS PRODUCED IN MULTIFRAGMENTATION"D. Henzlova et al., arXiv nucl-ex/0507003

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

abrasion

break- up

evaporation

“attractor line”

experimentaldata

E*=ATFO2

E*=27A MeV

abrasionevaporation

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

124Sn +124Sn Tlab= 800 MeV/u b = 5 fmBUU calculations of mid-peripheral nucleus-nucleus collisions

L. Shi, P. Danielewicz, R. Lacey, PRC 64 (2001) 034601

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 P

aolo Napolitani

V. Henzl

197Au + 197Au 197Au + 27Al

1 A GeV 238U + Pb

V. HenzlT. Enqvist

C.M. momentum seems to be selectively sensitive to the momentum dependence of the nuclear force

Note: in exp b estimated only for Afrag>60

quantitative discrepancy between experiment and BUU

1 A GeV 196Au + 196Au

PART 3

Applications to nuclear technology

238U + 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, 2001.

Prediction of RIB production rates at FAIR

D. Ridikas et al. 2004

Detection sensitivity. 0.1 g of nuclear material per ton of container

Needed: delayed-neutron yields, fission fragments A and Z distributions.

Acceleratorof electrons

Detectorsof photons and neutrons

Probingphotons

Schematic of the nuclear material detection system

Non-destructive characterisation of weapon grade materials or nuclear waste

Conclusions

The CHARMS group and collaboration: fission, spallation and fragmentation reactions at relativistic energies www.gsi.de/charms

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