Nucleus Nucleus 2015 – Catania
Nuclear Structure
of the Heaviest Elements revealed by
High-Precision Mass Measurements
Michael Block
GSI Darmstadt
Helmholtz-Institut Mainz
Institut für Kernchemie der Johannes Gutenberg Universität Mainz
Future Directions in SHE Research at GSI
120
Z
Talk by
Ch. Düllmann
16:30
Talk by
F.P. Heßberger
11417:15
Poster by
A. Di Nitto
tonight
108
SF
a
184
100
152
162
172
Courtesy Ch.E. Düllmann
N
b+
EC
b-
Nuclear Shells: Magic Numbers in SHE?
M. Bender et al., Phys. Lett. B 515 (2001) 42
Importance of Masses for Z > 100
Two neutron separation energy / MeV
16
Cf
Fm
No
Rf
Ds
Sg
Hs
14
12
Mt
Md
Lr
Es
10
140
144
148
152
156
160
164
Bh
Db
168
Neutron number N
high-precision mass measurements provide
• accurate absolute binding energies to map nuclear shell effects
• anchor points to pin down decay chains
➡ Studies the nuclear structure evolution
➡ Benchmark theoretical nuclear models
172
Nuclear Structure Indicators from Masses
two-neutron separation energy
Two neutron separation energy / MeV
16
Cf
S2n(N,Z) = M(N,Z) – M(N-2,Z) +2 mn
Fm
No
Rf
Ds
Hs
Sg
14
12
Mt
Md
Lr
Es
10
140
144
148
152
156
160
164
Bh
Db
168
172
Neutron number N
indication for shell closure at N = 152 & N = 162
Data from Atomic Mass Evaluation 2012:
M. Wang et al., CPC(HEP & NP), 2012, 36(12): 1603–2014
Nuclear Structure Indicators from Masses
two-neutron separation energy
S2n(N,Z) = M(N,Z) – M(N-2,Z) +2 mn
Two neutron separation energy / MeV
Z=98
Z=99
Z=100
Z=101
Z=102
Z=103
Z=104
15
14
13
12
11
10
140
144
148
152
156
160
164
Neutron number N
Two neutron separation number S2n / keV
16000
16
Z=106
Z=107
Z=108
Z=109
Z=110
Z=111
15000
14000
13000
12000
11000
10000
154
156
158
160
162
164
Neutron number N
indication for shell closure at N = 152 & N = 162
Data from Atomic Mass Evaluation 2012:
M. Wang et al., CPC(HEP & NP), 2012, 36(12): 1603–2014
166
168
170
172
Tools for Direct Mass Measurements
Time-of-flight spectrometry
momentum
analysis p=mv
L
single turn: SPEG/GANIL, S800/NSCL
multi turn: ESR/GSI, CSR/Lanzhou, RIBF ring
electrostatic MR-ToF (Giessen,
ISOLDE, RIKEN, ...)
start
stop
Frequency measurements
storage rings
ESR/GSI, CSR/Lanzhou, RIBF rings
Penning traps
LEBIT/NSCL, ISOLTRAP/ISOLDE
JYFLTRAP/JYFL, CPT/ANL
SHIPTRAP/GSI, TITAN/TRIUMF,
TRIGATRAP/ Mainz, MLLTRAP,
…
B
wc = q/m B
Principle of Penning Traps
PENNING trap
q/m
•
Strong homogeneous magnetic field
•
Weak electric 3D quadrupole field
Cyclotron frequency:
axial
motion
axial
motion
nz
1 q
fc 
 B
2 m
cyclotron motion
n+
n-
magnetron motion
L. S. Brown and G. Gabrielse, Rev. Mod. Phys. 58 (1986) 233
G. Gabrielse, Int. J. Mass Spectr. 279, (2009 ) 107
trajectory
Synthesis and Separation by SHIP
kinematic separation
in flight by velocity filter
Typical yield for primary beam  6 x 1012 / s
1 atom/s
@ Z  102 (s  1 mb)
1 atom/week
@ Z= 112 (s  1 pb)
SHIPTRAP Setup
≈ 50 MeV
≈ 1 eV
≈ 1 keV
SHIPTRAP Performance
60
147
A = 147
+
Ho
40
147
+
Dy
30
147
20
Er
147
Mass resolving power of
m/dm ≈ 100,000
in purification trap:
+
Tb
+
 separation of isobars
10
0
732350
732400
732450
732500
Excitation frequency / Hz
310 keV
91
Mass resolving power of
m/dm ≈ 1,000,000
in measurement trap:
90
Mean time of flight / ms
No. of counts / bin
50
89
88
ground
state 1/2+
87
86
isomeric
state 11/2-
85
-2
0
2
143
 separation of isomers
2+
Dy
4
(Excitation freq. - 1505390.8) / Hz
6
Direct mass measurements with SHIPTRAP
206Pb(48Ca,2n)252No
207Pb(48Ca,2n)253No
208Pb(48Ca,2n)254No
209Bi(48Ca,2n)255Lr
209Bi(48Ca,1n)256Lr
208Pb(48Ca,1n)255No
M. Block et al., Nature 463, 785 (2010), M. Dworschak et al., Phys. Rev. C 81, 064312 (2010)
E. Minaya Ramirez et al., Science 337, 1183 (2012)
SHIPTRAP Results vs. Atomic Mass Evaluation
Pinning Down a-Decay Chains
270Ds
Z = 110
mass can be fixed with
α
about 40 keV uncertainty now
Z = 108
α
Z = 104
Z = 102
0.1ms
α
264Hs
0.3ms
Z = 106
α
α
3.6ms
α
256Rf
2.3s
α
258Rf
13ms
Anchor points
262Sg
6.9ms
6.2ms
252No
266Hs
2.3ms
260Sg
254No
55s
270Ds
Masses of even-even N -Z = 48 and N -Z = 50 Nuclei
140
270
Ds
130
264
266
Hs
Hs
mc2 / MeV
120
260
Sg
258
256
100
Rf
Rf
252
254
No
90
80
262
Sg
110
No
250
248
Fm
Fm
(mc2(exp)- mc2(theo)) / MeV
70
2
Möller et. al. Kuora et al. Myers et al.
[KoT05]
[MöN95]
[MyS96]
Smolanczuk et al.
[SmS95a]
1
0
-1
-2
98
100
102
104
106
108
110 98
100
Atomic Number
102
104
106
108
110
Atomic Number/StrukturSWK/Abbildungen/Massen,
F.P. Heßberger, 3.9.2013
courtesy F. P. Hessberger
SHIPTRAP: Probing the Strength of Shell Effects
d2n(N,Z) = 2B(N,Z) – B(N-2,Z) – B(N+2,Z)
No
Experimental
Muntian (mic-mac)
Z=114 N=184
Möller FRDM
Z=114 N=184
TW-99
Z=120 N=172
337 (2012) 1207
SkM*
Z=126 N=184
Probing the Strength of Shell Effects
Evolution of N = 152 shell closure
1800
1600
d2n_max / keV
1400
1200
1000
800
600
400
200
0
96
98
100
102
Z
Data taken from Atomic Mass Evaluation (AME) 2012: M. Wang et al.
104
106
Probing the Strength of Shell Effects
N = 152 isotones
Data taken from Atomic Mass Evaluation (AME) 2012: M. Wang et al.
Upgrades and Combinations
• Novel experiments
• trap-assisted decay spectroscopy
• laser spectroscopy (gas cell, gas jet, trap)
• gas phase chemistry
• Increase efficiency and sensitivity
• novel measurement schemes (PI-ICR)
• single-ion mass measurements (FT-ICR)
(→ TRIGA-TRAP, TRAPSENSOR)
• cryogenic gas cell
Cryogenic Gas Cell
Cryo Cell
Gas Cell
400mm
DC-Cage
DC-Cage
RF-Funnel
40K
300K
RFFunnel
60mbar He
20mbar He
450mm
320mm
Advantages compared to 1st generation gas cell:
• Larger stopping volume and Coaxial injection of reaction products
• Higher cleanliness due to cryogenic operation
• Larger gas density at a lower absolute pressure
C. Droese et al. NIM B 338, 126 (2014)
Cryogenic Gas Cell
Cryo Cell
Gas Cell
400mm
DC-Cage
DC-Cage
RF-Funnel
40K
300K
RFFunnel
60mbar He
20mbar He
450mm
320mm
Advantages compared to 1st generation gas cell:
• Larger stopping volume and Coaxial injection of reaction products
• Higher cleanliness due to cryogenic operation
• Larger gas density at a lower absolute pressure
C. Droese et al. NIM B 338, 126 (2014)
Recent Breakthrough
Destructive
time-of-flight
detection
Spatially
resolved
detection
Delay-line
detector
S. Eliseev et al., Appl. Phys. B114, 107 (2014)
Phase-Imaging Ion-Cyclotron-Resonance Method
Delay-Line Detector
ions
Determination of the
spatial distribution
Independent
Measurements
image
of magnetron
motion (G ≈ 20)
of Eigenfrequencies n+ and n-
Radial excitation
Radial excitation followed
by a phase accumulation time
  2n  2nt
 R
n 

2t tR
S. Eliseev et al., Phys. Rev. Lett. 110, 082501 (2013)
R
8 mm
1 mm
Φ
R
PI-ICR vs. ToF-ICR in experiment
PI-ICR
ToF-ICR
10-hour measurements
d[M(124Xe) - M(124Te)] ~ 300 eV
d[M(132Xe) - M(131Xe)] ~ 70 eV !!!
Gain in Precision ~ 4.5 !!!
S. Eliseev et al., Phys. Rev. Lett. 114, 107 (2014)
48Ca
Mass Measurements
nc(48Ca+)
nc(C4+)
TITAN
LEBIT
AME 2012
SHIPTRAP
d(mass excess) ≈ 17 eV
= 1.000 990 101 75(36stat) (15sys)
PRELIMINARY
Superheavy Elements Subcollaboration of NUSTAR @ FAIR
Proposal to integrate new "Superheavy Element" subcollaboration in NUSTAR
@ FAIR submitted to Board of Representatives (Summer '14)
Focus: synthesis, nuclear structure, atomic physics, nuclear
chemistry experiments in region Z ≥ 100
Existing facilties: SHIP, TASCA, SHIPTRAP, Chemistry beamline
Developments for high-intensity cw-Linac ongoing (HIM, GSI, U Frankfurt)
Complementary to existing NUSTAR activities at Super-FRS
Organizational Structure:
Spokesperson:
Deputy:
Technical Director:
R.-D. Herzberg (Univ. Liverpool)
M. Block (GSI/HIM/JGU)
A. Yakushev (GSI)
Currently includes 9 German and 17 international institutes
Endorsed by NUSTAR Collaboration Committee:
submission to FAIR management:
Sept. 25, 2014
summer 2015
SHE research 2020+
New cw linac
EBeam up to 7.3 MeV/u
Length: 13.5 m
1
H
3
Li
11
Na
19
K
37
Rb
55
Cs
87
Fr
119
4
Be
12
Mg
20 21
Ca Sc
38 39
Sr Y
56 57+* 58
Ba La Ce
88 89+" 90
Ra Ac Th
120
59
Pr
91
Pa
60
Nd
92
U
61
Pm
93
Np
62
Sm
94
Pu
63
Eu
95
Am
64
Gd
96
Cm
65
Tb
97
Bk
66
Dy
98
Cf
67
Ho
99
Es
68
Er
100
Fm
69
Tm
101
Md
70
Yb
102
No
71
Lu
103
Lr
22
Ti
40
Zr
72
Hf
104
Rf
23
V
41
Nb
73
Ta
105
Db
24
Cr
42
Mo
74
W
106
Sg
25
Mn
43
Tc
75
Re
107
Bh
26
Fe
44
Ru
76
Os
108
Hs
27
Co
45
Rh
77
Ir
109
Mt
28
Ni
46
Pd
78
Pt
110
Ds
29
Cu
47
Ag
79
Au
111
Rg
30
Zn
48
Cd
80
Hg
112
Cn
5
B
13
Al
31
Ga
49
In
81
Tl
113
---
6
C
14
Si
32
Ge
50
Sn
82
Pb
114
Fl
7
N
15
P
33
As
51
Sb
83
Bi
115
---
8
O
16
S
34
Se
52
Te
84
Po
116
Lv
9
F
17
Cl
35
Br
53
I
85
At
117
---
2
He
10
Ne
18
Ar
36
Kr
54
Xe
86
Rn
118
---
--- ---
•
Atomic structure beyond No (Z=102)
•
Experiments with single SHE-ions
(e.g. chemistry + mass spec)
•
Chemical studies towards Eka-Rn
•
New SHE molecules, their stability,
formation kinetics
•
New period in the periodic table
184
Mapping the island of stability:
• New elements with Z>118
• Neutron-rich isotopes in transfer reactions
• Weak EC decay channels towards center of island
• Direct mapping of shell evolution towards N=184
27
First components – October 2014
Courtesy of V. Gettmann / W. Barth
SHIPTRAP Collaborators
D. Ackermann, K. Blaum, S. Chenmarev, C. Droese, Ch. Duellmann,
M. Eibach, S. Eliseev, P. Filanin, F. Giacoppo, M. Goncharov, E. Haettner,
F. Herfurth, F. P. Heßberger, O. Kaleja, M. Laatiaoui, G. Marx,
D. Nesterenko, Yu. Novikov, W. R. Plaß, S. Raeder, D. Rodríguez,
D. Rudolph, C. Scheidenberger, S. Schmidt, L. Schweikhard,
P. Thirolf, G. Vorobjev, C. Weber, …
2010
Summary and Conclusions
• State-of-the-art mass spectrometry provides masses of exotic
nuclides with high accuracy – anchor points
• High-precision mass measurements allow probing shell effects and
tracking the evolution of nuclear structure in the heaviest elements
• Technical and methodical improvements will extend the reach
towards more exotic nuclides with higher Z
• SHE research remains cornerstone of science program at GSI/FAIR
• New cw-linac will preserve competitiveness in the future