MP-41 Teil 2: Physik exotischer Kerne

MP-41 Teil 2: Physik exotischer Kerne, SS-2012

MP-41 Teil 2: Physik exotischer Kerne

13.4. Einführung, Beschleuniger

20.4. Schwerionenreaktionen, Synthese superschwerer Kerne (SHE)

27.4. Kernspaltung und Produktion neutronenreicher Kerne

4.5. Fragmentation zur Erzeugung exotischer Kerne

11.5. Halo-Kerne, gebundener Betazerfall, 2-Protonenzerfall

18.5. Wechselwirkung mit Materie, Detektoren

25.5. Schalenmodell

1.6. Restwechselwirkung, Seniority

8.6. Tutorium-1

15.6. Tutorium-2

22.6. Vibrator, Rotator, Symmetrien

29.6. Schalenstruktur fernab der Stabilität

6.7. Tutorium-3

13.7. Klausur


Rare-Isotope Beam Experiments

Discovery of projectile-fragmentation reaction at Bevalac @ LBL (Lawrence Berkeley Laboratory) D.E. Greiner et al., Phys.Rev. Lett. 35 (1975) 152

12C, 16O (2.1 AGeV) + Target (Be, C, Al, Cu, Ag, Pb)

- Several fragments are produced in reactions

- Velocity of fragments is almost the same as that of the beam

- Momentum distribution is narrow, and has no significant correlation with target mass and beam energies


Rare-Isotope Beam Experiments

Momentum distribution of fragments (example 34S fragments from 40Ar + C @ 213 AMeV )

34S fragments: 400 MeV/c narrow40Ar beam: 26600 MeV/c

Momentum distribution of fragments are represented by a simple formula based on the Goldhaber model

10

A

FAF

A: Beam mass numberF: Fragment mass number

σ0 = 90 MeV/c


Production of Radioactive Ion Beams

Spallation

Fragmentation

ISOL = Isotope Separator On Line


In-flight separation of Rare Isotope Beams

Primary (production) target Peripheral nuclear reactionsForward focused products

Electromagnetic separator

Secondary (reaction)

target Experiment

al area

Selected radioactive beamE >> 20 AMeV

Stable HI projectile sourceE ~ 1000 AMeV


Fragmentation at Relativistic Energies

FRS

FRS

abrasion

projectile

target nucleus

ablation

projectile fragment

FRagment Separator


RIBs produced by fragmentation or fission

9Be targetexotic nuclei (also neutron deficient)fragments nearly retain the projectile direction and velocity

208Pb target, heavy beam (238U)neutron rich nucleifragments can be faster than the projectile

Interaction zone

Coulomb field


Radioactive Ion Beams at GSI

1GeV/u U + H

About 1000 nuclear residues

identified

A/Z-resolution ~10-3


The FRagment Separator FRS

in-flight A and Z selection energy resolution: ~ 1 GeV

131Sn 132Sn


Rare Isotope Selection at FRS: Bρ – ΔE – Bρ selection

20m secondary beam78Ni ~ 100 AMeV

primary beam86Kr ~700 AMeV

production target9Be

fmagnetic dipoles degrader

fully striped fragments

Transmission : • 20-70 % for

fragmentation• < 2 % for fission

magnetic dipoles


FRagment Separator

Wedge-shapedDegrader

PrimaryBeam

Beam & AllFragmentation Products

MomentumSelection

SpacialDispersion

SecondaryBeam

IsotopeSelection

19Ne at 600AMeV:Phase-space imaging of differently shaped degraders within the achromatic ion-optical system. The results for a homogeneous, an achromatic, and a monoenergetic degrader are given. All degraders have the same thickness on the optical axis (d/r=0.5)


Fragment Separation40Ar 50MeV/u + Ta (100μm), wedge shaped Al (200μm) degrader

0.39 mrad 1.66mrad


Chromatic Aberration

When different colors of light propagate at different speeds in a medium, the refractive index is wavelength dependent. This phenomenon is known as dispersion.

Longitudinal (axial) chromatic aberration: Transverse (lateral) chromatic aberration:The focal planes of the various colors do The size of the image varies from one not coincide. color to the next.


Production, Separation, Identification

abrasion

projectile

target nucleusablation

projectile fragment

SISUNILAC

FRS

TPC-x,y position @ S2,S4

Plastic scintillator (TOF) @ S4

MUSIC (ΔE) @ S4

Standard FRS detectors

FRagmentSeparator


Standard FRS and RISING detectors

multiwire chamber;beam position

CATE Si-CsI arrays; (X,Y), Z,A

scintillator

MUSICionization chamber;

Zscintillator

ToF

Ge-Cluster detectors

production target

Z

A/Q

Y

X

Y

X

reaction target

E

E


Scattering experiments at relativistic energies

xy positionfrom LYCCA


Calculate the event-rate for the fragmentation reaction

to produce the doubly magic nucleus 100Sn. The expected production cross section is 7.4·10-12 [barn].

5010050

294

11012454 /410 SncmgBesXe

9g of 9Be ≡ 6.02·1023 particles/cm2

4g of 9Be ≡ 2.68·1023 particles/cm2

luminosity = projectile [s-1] · target nuclei [cm-2] = 1010 [s-1] · 2.7·1023 [cm-2]

event rate = luminosity [s-1 cm-2] · cross section [cm2] = 2.7·1033 [s-1 cm-2] · 7.4·10-36 [cm2] = 0.02 [s-1]

= 72 [h-1] = 1718 [d-1]

MP-41 Teil 2: Physik exotischer Kerne

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