Sub-task 4:Spallation and fragmentation

reactionsM. Valentina Ricciardi (GSI)

in place of José Benlliure (USC)

Sub-task leader: Universidad de Santiago de Compostela, SpainOther participant: GSI, Darmstadt, Germany Contributor: VINČA-INS, Belgrade, Serbia

TASK 11: BEAM INTENSITY CALCULATION - kick-off meeting

General idea behind sub-task 4

Spallation and fragmentation reactions are a versatile tool for the production of both neutron-rich and neutron-deficient nuclides

By an appropriate combination of projectile, target and energy the production of a specific exotic nuclide can be enhanced

A deep knowledge on these reaction mechanisms is essential for the planning and design of a RIB facility

A deep knowledge on spallation and fragmentation reactions can be achieved by:

measuring the production yields in some "key" reactions

developing prediction codes

benchmark of the models

planning "key"

experiments

Measurement of the production yields:the inverse-kinematics method at relativistic

energies

p 1GeV

238U

238U 1GeV/u

H2

direct kinematics inverse kinematics

~ 10 KeV/u

~ 1 GeV/u

Identification off-line with chemistry or spectroscopy:

only cumulative yields of long-lived isotopes no knowledge on the kinematics of the reaction

Identification on-line with recoil separator:

identification of every reaction product in-flight prior to decay velocity spectrum for every produced isotope

Resolution: - ()/ 5·10-4 - Z / Z 510-3

- A / A 2.510-3

ZAB

ecm0

The Fragment Separator at GSI

Full identification of every product

- Precise velocity measurement for every nuclide- Disentangling different reaction mechanisms

Example: production cross sections for 1 A GeV 238U on p

fissionM. BernasM. V. Ricciardi

evaporation residuesJ. Taïeb

Data available at: http://www-w2k.gsi.de/charms/data.htm

The reaction mechanisms

proton 1 GeV

fissionfragments

Intra-nuclear Cascade Evaporation / Fission

238U

Abrasion

sequential evaporation

fission

excited compound

nucleus

What we learn from the experimental data

FRAGMENTATION CORRIDORE* of CN from Coulomb excit. to central coll.Max E* length of corridorFragments: higher mass CN: low E*

lower mass CN: high E*E*: low evapor. of n (horizontal path) high evapor. of n, p, , IMF (transv. path)

FISSION AREAFission barrier ~ Z2/A

e.g. Au, Pb prefer to evap. n, p(A/Z)FFs ≈ (A/Z)CN position of the CN

High E* FFs close to stabilityLow E* FFs neutron-rich

COLD FRAGMENTATION

EVAPORATION RESIDUES

FISSION FRAGMENTSFISSION

FRAGMENTS

EVAPORATION RESIDUES

From experimental data to models

proton 1 GeV

fissionfragments

Intra-nuclear Cascade Evaporation / Fission

Statistical model for the description of spallation and fragmentation

238U

Abrasion

sequential evaporation

fission

excited compound

nucleus

The statistical model

From the INC stage: ACN, ZCN, E* (exit. en.), J2 (mean sq. ang. mom.)

Random sample among: n, p, light-particles evaporation and fissionProbability of one or the other channel given by the decay widths

If evaporation occurs: En. consumed = bind. en. (+ Coul. barr.) + kin. en. Mass of fragment = CN after the evaporation chainevaporation goes on until the energy is consumed or a fission event occurs

If fission occurs: En. threshold = fission barrier Fission fragments: <A/Z> ≈ <A/Z>CN , Y = Y(E*, N)If fission fragments are enough excited they can follow an evaporation chain

From model to experimental data: the case of cold

fragmentation

List of deliverables

Provide data and benchmarking of models for the reactions:1 A GeV 238U + p, d - evaporation residues, fission fragments(GSI, USC – month 12)1 A GeV 238U + Pb – fission fragments (especially low-energy fission)(GSI, USC – month 12)1 A GeV 136Xe + p, Be, Pb - neutron-rich nuclides (cold fragmentation) (GSI, USC – month 18)1 A GeV 238U,208Pb + Be - neutron-rich nuclides (cold fragmentation) (USC)

Systematic calculations of nuclide production cross-sections (GSI, USC, VINCA)

Implementation plan for the first 12 months

Provide final data for the production cross sections of extremely neutron-rich residues in the reactions:

136Xe(1 A GeV) + 1H,Be,Pb 238U(1 A GeV) + Be 208Pb(1 A GeV) + Be

Provide data and benchmarking of models for the reactions:1 A GeV 238U + p, d - evaporation residues, fission fragments1 A GeV 238U + Pb – fission fragments (especially low-energy fission)

Up to 18 months:

Present status of the work

Data evaluation on the production of extremely neutron-rich residues in the reactions 1 A GeV 136Xe + p, Be, Pb and 1 A GeV 238U,208Pb + Be is in progress.

This work will be done with USC own resources

Experimental data:1 A GeV 238U + p, d - evaporation residues, fission fragments1 A GeV 238U + Pb – fission fragments (especially low-energy fission)are almost fully analyzed

The predictive power of the model is being improved (dynamics of fission and a proper description of collective excitations, IMF emission)

12 months

18 months

TASK 11: BEAM INTENSITY CALCULATION - kick-off meeting

Thank you