Physics with Exotic Nuclei Hans-Jürgen Wollersheim

Scattering Experiments with RIBs – Nuclear Structure Results Experimental evidence for closed-shell nuclei Scattering experiments at relativistic energies Projectile-like identification (Z, A) and scattering angle θ Doppler-shift correction of the emitted γ-rays

Outline

+12

E

)02;2( 1++ →EB

Physics with Exotic Nuclei Experimental evidence for magic numbers close to stability

Maria Goeppert-Mayer & J. Hans D. Jensen

high energy of 21+ state

Nuclei with magic numbers of neutrons/protons

+12

E

low B(E2; 21+→0+) values transition probability measured in single particle units (spu)

If we move away from stability? )02;2( 1 ++ →EB

Physics with Exotic Nuclei Experimental evidence for magic numbers close to stability

Production, Separation, Identification

abrasion

projectile

target nucleus ablation

projectile fragment SIS

FRS

TPC-x,y position @ S2,S4

Plastic scintillator (TOF) @ S4

MUSIC (ΔE) @ S4

Standard FRS detectors

FRagment Separator

Scattering Experiment at Relativistic Energies

104Sn, 100 MeV/u

124Xe, 793MeV/u

standard scintillator (SC21) finger segmented detector

104Sn fragments using 124Xe at 793 MeV/u

high rate at S2 ~106 s-1 ~2400 % more tracking efficiency good A/Q resolving power

Frederic Ameil

new digital readout

Scattering Experiment at Relativistic Energies

impact parameter: b

Au

fmCCD TP 5min ++>

Rutherford scattering only if distance of closest approach Dmin is large compared to nuclear radii + surfaces:

CP, CT half-density radii

Dmin fragment

beEBMeVE

255.0)10;1(3.13

≅→

≅−

∗

WuEBMeVE

9)20;2(086.4

=→

=+

∗

WuEBMeVE

34)30;3(615.2

=→

=−

∗

( ) ( )( )

=≥−

⋅→⋅⋅

≈

−

− 1/ln2210;

1

222

22

λλλ

λπλπσ λπλ forbbforB

beceZ

a

P

Atomic Background Radiation

Bremsstrahlung: slowing down of a moving point-charge

Radiative electron capture (REC) capture of target electrons into bound states of the projectile:

Primary Bremsstrahlung (PB) capture of target electrons into continuum states of the projectile:

Secondary Bremsstrahlung (SB) Stopping of high energy electrons in the target: 22~ tp ZZ ⋅σ

tp ZZ ⋅2~σ

tp ZZ ⋅2~σ

Scattering Experiment at Relativistic Energies

197Au-target 104Sn

124Xe, 793MeV/u

relativistic Coulomb excitation

xy position from LYCCA

Scattering Experiment at Relativistic Energies

104Sn

124Xe, 793MeV/u

exp. observables: Z, A, θ

RIB from FRS

secondary 197Au target

DSSSD DSSSD

CsI

CsI

time-of-flight

(x,y,ΔE) (x,y,ΔE) diamond/plastic

Lund-York-Cologne CAlorimeter

Scattering Experiment at Relativistic Energies

exp. observables: Z, A, θ

RIB from FRS

secondary 9Be target

DSSSD DSSSD

CsI

CsI

time-of-flight

(x,y,ΔE) (x,y,ΔE) diamond/plastic

Scattering Experiment at Relativistic Energies

exp. observables: Z, A, θ

RIB from FRS

secondary 9Be target

DSSSD DSSSD

CsI

CsI

time-of-flight

(x,y,ΔE) (x,y,ΔE) diamond/plastic

12

−=⋅γ

kinEcm

DSSSDCsIkin EEE ∆+=

( )211

cv−

=γ

with

and

with v from LYCCA-ToF

Lund-York-Cologne CAlorimeter

PreSPEC target chamber variable target position (13cm, 23cm)

Pavel Golubev

start ToF DSSSD

Au target

HECTOR BaF2

prompt ΔE-E

Coulomb excitation: A/Q - 37Ca all Ca detected in ΔE-E

prompt Fragmentation: A/Q - 37Ca K detected (mainly 36K)

37Ca beam at 196 MeV/u

Additional γ-Ray Background Radiation

1‰ interaction target most γ-rays from CATE

time spectrum

Scattering Experiment at Relativistic Energies

Doppler effect 80Kr → 197Au, 150 AMeV

2

0

1

cos1

β

ϑβ γγ

γ

−

⋅−=

ab

EE

Scattering Experiment at Relativistic Energies

2

0

1

cos1

β

ϑβ γγ

γ

−

⋅−=

ab

EE 00≅pϑfor

2

0

=

ΩΩ

γ

γ

EE

dd

lab

rest

Lorentz boost:

beam

Doppler effect:

Doppler-Shift Correction 238U on 197Au (386 mg/cm2) at 183 AMeV

66.372 79 Au Kα3 0.033

66.991 79 Au Kα2 27.5

68.806 79 Au Kα1 46.4

77.577 79 Au Kβ3 5.57

77.982 79 Au Kβ1 10.70

80.130 79 Au Kβ2 3.84

cos θ

γ

Au19779

http://ie.lbl.gov/atomic/x2.pdf Michael Reese

Doppler-Shift Correction 238U on 197Au (386 mg/cm2) at 183 AMeV

20 1

cos1

β

ϑβ γγγ

−

⋅−⋅=

ab

EE

93.844 92 U Kα3 0.099

94.654 92 U Kα2 28.2

98.434 92 U Kα1 45.1

110.421 92 U Kβ3 5.65

111.298 92 U Kβ1 10.70

114.445 92 U Kβ2 4.15

cos θ

γ

U23892

http://ie.lbl.gov/atomic/x2.pdf Michael Reese

Doppler Broadening

⋅⋅−⋅

=∆

γ

γ

γ

γ

ϑβϑβ

cos1sin

0

0

EE

γϑ∆⋅ ( ) ( ) ⋅⋅−⋅−−

=∆

γ

γ

γ

γ

ϑββϑβ

cos11cos

20

0

EE

β∆⋅

opening angle: slowing down in target:

beam

target

γ-ray set-up with higher efficiency

Ivan Kojouharov

Advanced GAmma Tracking Array

Signals from 36 segments + core are measured as a function of time (γ-ray interaction point)

John Strachan

Encapsulation

LYCCA

Au, Be target

HECTOR BaF2 array

AGATA Cluster array

HECTOR team

preprocessor computer farm

digitiser

Damian Ralet, Stephane Pietri

AGATA

AGATA at PreSPEC

T.R. Saito et al. Phys.Lett. B669 (2008), 19

High-energy Coulomb excitation triaxiality in even-even nuclei (N=76)

21+→0+

22+→21+

22+→0+

22+→21+

22+→0+

First observation of a second excited 2+ state populated in a Coulomb experiment at 100 AMeV using EUROBALL and MINIBALL Ge-detectors.

shape symmetry collective strength

)3(sin89)3(sin231

)3(sin89)3(sin

720

)02;2()22;2(

2

2

2

2

1

12

γγγ

γ

−

−+

−=→→

EBEB

)3(sin89)3(sin231

)3(sin89)3(sin231

)02;2()02;2(

2

2

2

2

1

2

γγγγ

−

−+

−

−−

=→→

EBEB

γ

γ

3sin893

3sin893)2()2(

2

2

1

2

−−

−+=

EE

Ivan Kojouharov, Michael Reese, Namita Goel, Liliana Cortes, Frederic Ameil, Bogdan Szczepanczyk H.-J. W., Damian Ralet, Pushpendra Singh, Stephane Pietri, Tobias Habermann, Edana Merchan, Giulia Guastalla, Plamen Boutachkov, Adolf Brünle,

Ian Burrows, Jonathan Strachan, (Paul Morral), Jürgen Gerl, (Henning Schaffner, Magda Gorska)

Slowed down beams – new experimental perspectives

VC ( )cmP av

QeZL θcos14 2

02

max −⋅⋅⋅⋅⋅⋅

≅∆

angular momentum transfer:

collective strength nuclear shape

Slowed down beams – beam characteristics

64Ni 700 AMeV

109 pps 107 pps 3∙106 pps 105 pps

62Co ~ 13 AMeV

ΔEnergy 5.2 AMeV Δθ 35 mrad

Slowed down beams – experimental set-up

target degrader

electrostatic mirror + MCP detector

position resolution ~ 1 mm time resolution ~ 100 ps

TPC-1 TPC-2 SC41 (x1 y1 t1) (x2 y2 t2)

( )12

2/311 /78.2/ss

AEtAE

−⋅=

∆∆

(x3 y3 t3)

experimental results:

velocity β beam energy E/A1 scattering angle θcm

Slowed down beams – experimental set-up

target degrader

TPC-1 TPC-2 SC41 (x1 y1 t1) (x2 y2 t2) (x3 y3 t3)

MCP DSSSD TOF between MCP and DSSSD

Time resolution 200 ps for one of the 256 detector pixels Akhil Jhingan (IUAC)

Reactions with Relativistic Radioactive Beams – R3B

𝐸𝐸∗ = �𝑚𝑚𝑖𝑖2𝑖𝑖

+ �𝑚𝑚𝑖𝑖𝑚𝑚𝑗𝑗𝛾𝛾𝑖𝑖𝛾𝛾𝑗𝑗 1− 𝛽𝛽𝑖𝑖𝛽𝛽𝑗𝑗𝑐𝑐𝑐𝑐𝑐𝑐𝜗𝜗𝑖𝑖𝑗𝑗𝑖𝑖≠𝑗𝑗

− 𝑚𝑚𝑝𝑝𝑝𝑝𝑝𝑝𝑗𝑗 𝑐𝑐2 + 𝐸𝐸𝛾𝛾,𝑠𝑠𝑠𝑠𝑠𝑠

Excitation energy E* from kinematically complete measurement of all outgoing particles

Dipole strength distribution of 68Ni

O. Wieland et al.; Phys. Rev. Lett 102, 092502 (2009)

direct γ-decay branching ratio: Γ0/Γ = 7(2)%

D. Rossi et al.; Phys. Rev. Lett 111, 242503 (2013)

mean field calculation

E.Litvinova et al.; PRC 79, (2009) 054312

γ-ray decay data

neutron decay data

Pygmy resonance

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