Post on 11-Feb-2021
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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