Investigating the Atomic and Nuclear Properties of the Heaviest - - PowerPoint PPT Presentation

Investigating the Atomic and Nuclear Properties of the Heaviest Elements

Michael Block

GSI Darmstadt Helmholtzinstitut Mainz Institut für Kernchemie der Universität Mainz GSI Colloquium 19.05.2015

Outline

• Status of superheavy element (SHE) research
• Basics of Penning trap mass spectrometry (PTMS)
• Direct mass measurements of nobelium and lawrencium isotopes
• New developments and selected results related to neutrino physics
• Basics of resonance ionization laser spectroscopy (RIS)
• Experimental efforts towards RIS of 254No at GSI
• Summary and conclusions

SHIPTRAP Collaborators

2010

• 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, …

• D. Ackermann, M. Block,

F.P. Heßberger

• M. Laatiaoui, S. Raeder

‏ Laser Spectroscopy Collaborators

Former members:

• E. Minaya Ramirez, J. Even, Ch. Droese
• F. Lautenschläger, P. Chhetri,
• Th. Walther
• H. Backe, W. Lauth
• R. Ferrer, P. Van Duppen
• B. Cheal, C. Wraith
• P. Kunz

Superheavy Elements – Present Status and Key Questions

Nuclear Chart

Neutron Number N Proton Number Z

SHE

• ≈ 3,000 nuclides known
• ≈ 250 stable nuclides
• ≈ 7,000 nuclides predicted to exist

Superheavy Nuclei (SHN)

Deformation

• fission barrier in liquid drop model vanishes for Z ≈ 106
• stabilization against spontaneous fission by nuclear shell effects

superheavy nuclei owe their very existence to shell effects Epot ground state (spherical) saddle point macroscopic fission barrier

100 120 114 162 184 108 152

N Z

a

b+ EC

SF b-

172

a a a a a

??????

Fl Lv Cn Ds Mt Hs Bh Rg

Superheavy Nuclides – Current Landscape

Courtesy Ch.E. Düllmann

• M. Bender et al., Phys. Lett. B 515 (2001) 42

Nuclear Shells: Magic Numbers in SHE?

high-precision mass measurements provide

• accurate absolute binding energies to map nuclear shell effects
• anchor points to fix decay chains

➡ Studies the nuclear structure evolution ➡ Benchmark theoretical nuclear models

Importance of Masses for Z > 100

Atomic Physics Studies of the Heaviest Elements

1 18 1 2 H 2 13 14 15 16 17 He 3 4 5 6 7 8 9 10 Li Be B C N O F Ne 11 12 13 14 15 16 17 18 Na Mg 3 4 5 6 7 8 9 10 11 12 Al Si P S Cl Ar 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 K Ca Sc Ti V Cr Mn Fe Co Ni Cu Zn Ga Ge As Se Br Kr 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 Rb Sr Y Zr Nb Mo Tc Ru Rh Pd Ag Cd In Sn Sb Te I Xe 55 56 57+* 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 Cs Ba La Hf Ta W Re Os Ir Pt Au Hg Tl Pb Bi Po At Rn 87 88 89+" 104 105 106 107 108 112 114 Fr Ra Ac Rf Db Sg Bh Hs 109 110 111 Cn 113 Fl 115 116 117 118 Mt Ds Rg

• Lv
• *

58 59 60 61 62 63 64 65 66 67 68 69 70 71 Ce Pr Nd Pm Sm Eu Gd Tb Dy Ho Er Tm Yb Lu

"

90 91 92 93 94 95 96 97 98 99 100 101 102 103 Th Pa U Np Pu Am Cm Bk Cf Es Fm Md No Lr

chemistry with single atoms

Lanthanides Actinides

• study atomic structure and architecture of periodic table
• affected by strong relativistic effects and QED
• benchmark theoretical calculations

Relativistic Effects in Uranium

finite c

contraction of s1/2, p1/2 orbitals expansion of

d, f orbitals

Spin-orbit coupling non-relativistic relativistic

• 60
• 50
• 40
• 30
• 20
• 10

6s

1/2

6p

1/2

6p

3/2

5f

5/2

5f

7/2

6s 6p 5f 6d 7s

{

E [eV]

6d3/2, 6d5/2 7p1/2, 7p3/2 7s1/2,

c 

• J. P. Desclaux, At. Data Nucl. Data Tables 12 (1973) 311

Methods: Search for atomic levels hyperfine spectroscopy Measurement of isotopic shifts Motivation: relativistic and QED effects Nuclear moments & spins changes in mean square charge radii

Laser Spectroscopy of the Heaviest Elements

adapted from B. Cheal

Laser spectroscopy – Status of Measurements

Measured since 1995 Measured prior to 1995

Figure from B. Cheal and K.T. Flanagan, J. Phys. G. 37 (2010) 113101

• Where is the end of the periodic table in atomic number and mass?
• What is the heaviest element that we can synthesize?
• What are the properties and boundaries of the predicted ”island of stability” of

superheavy elements?

• What are the details of the fission process and competing decay modes?
• Are there remnants of long-lived superheavy elements on earth?
• How do relativistic effects affect the architecture of the periodic table?

Superheavy Elements – Key Questions SHE research at GSI/HIM follows a comprehensive approach investigating atomic, chemical, and nuclear properties of SHE

100 120 114

162

184 108

152

N Z

Future Directions in SHE Research at GSI

a

b+ EC

SF b-

172

Courtesy Ch.E. Düllmann

Production of the Heaviest Elements

Requirements – Some Facts and Figures

Beam intensity:

• present:

6 x 1012 pps (1mAp) for typical beams 48Ca, 50Ti, …

• future:

≥6 x 1013 pps (10mAp) feasible

• need for high-power targets

Targets:

• 0.5-1.0 mg/cm2 thickness
• about 10 mg of material needed for typical target wheel geometries
• limited availability of actinide material

Recoil separator

• High transmission, short separation time
• low background (beam suppression, low n, g background)

Cross Sections for SHE Production

Courtesy Ch.E. Düllmann

102 104 106 108 110 112 114 116 118 120 1E-15 1E-14 1E-13 1E-12 1E-11 1E-10 1E-9 1E-8 1E-7 1E-6

Projectile Target

48Ca,..., 70Zn + 208Pb/ 209Bi 13C,..., 26Mg + 238U... 249Bk 48Ca + 238U,..., 249Cf

cross section / barn

atomic number Z

Z=119

50Ti + 249Bk

70 fb Due to low intensities radioactive beams are not competitive for SHE studies yet!

• Intensity of 109 pps corresponds to

0.5 mg / cm2 targets

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)

Basics of Penning Trap Mass Spectrometry

Basic Idea of a Particle Trap

restoring force 3D harmonic

• scillation

r F    

• confine single particles (nearly) at rest
• minimize perturbations (collisions, field imperfections, ...)
• long observation / measurement times

reducing the kinetic energy by cooling

Courtesy H.-J.. Kluge

Principle of Penning Traps

Cyclotron frequency:

B m q fc     2 1

q/m

• Strong homogeneous magnetic field
• Weak electric 3D quadrupolar field
• L. S. Brown and G. Gabrielse, Rev. Mod. Phys. 58 (1986) 233
• G. Gabrielse, Int. J. Mass Spectr. 279, (2009 ) 107

PENNING trap n- n+ nz axial motion cyclotron motion magnetron motion trajectory axial motion

20 40 60 80 100 120 140 160 10 20 30 40 50 60

Counts / bin TOF / us

Cyclotron frequency measurement

Time-of-flight resonance technique

• M. König et al., Int. J. Mass Spec. Ion Process. 142 (1995) 95

20 40 60 80 100 120 140 160 10 20 30 40 50 60

Counts / bin TOF / us

• 4
• 2

2 4 86 88 90 92 94 96 98 100

mean TOF /

m

s Excitation Frequency / Hz - 809548.8

133Cs+

1 m

Trap Drift- tube Detector

B

z B Fz    m

Penning Trap Mass Spectrometry

m qB

C

 n 2 1 

ref C f

m m r   n n Re

determine mass via cyclotron frequency measurement

 

e c ref e ref ref ref

m q m q m q q m      n n

atomic mass



ref ref ref

m B q    n 2 1 magnetic field calibration

tot RF c

N T s 1 1 ) ( n n 

statistical uncertainty TRF observation time Ntot number of det. ions

Direct Mass Measurements

• f Nobelium and Lawrencium Isotopes

with SHIPTRAP

SHIPTRAP Setup

≈ 50 MeV

≈‏1‏keV ≈‏1‏eV

SHIPTRAP Performance

732350 732400 732450 732500 10 20 30 40 50 60 147Tb + 147Dy + 147Ho +

• No. of counts / bin

Excitation frequency / Hz

147Er +

A = 147

Mass resolving power of m/dm‏≈‏100,000‏ in purification trap:  separation of isobars

• 2

2 4 6 85 86 87 88 89 90 91

Mean time of flight / ms (Excitation freq. - 1505390.8) / Hz 143Dy 2+ 310 keV

ground state 1/2+ isomeric state 11/2-

Mass resolving power of m/dm‏≈‏1,000,000 in measurement trap:  separation of isomers

• 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)

206Pb(48Ca,2n)252No 207Pb(48Ca,2n)253No 208Pb(48Ca,2n)254No 208Pb(48Ca,1n)255No 209Bi(48Ca,2n)255Lr 209Bi(48Ca,1n)256Lr

Direct mass measurements with SHIPTRAP

SHIPTRAP Results vs. Atomic Mass Evaluation

252No 2.3s 254No 55s 270Ds 0.1ms 262Sg 6.9ms 266Hs 2.3ms 258Rf 13ms

α α α α

Z = 102 Z = 104 Z = 106 Z = 108 Z = 110

α α α

256Rf 6.2ms 260Sg 3.6ms 264Hs 0.3ms

Pinning Down a-Decay Chains

270Ds mass can be fixed with

about 40 keV uncertainty now Anchor points

Masses of even-even N -Z = 48 and N -Z = 50 Nuclei

98 100 102 104 106 108 110

70 80 90 100 110 120 130 140

98 100 102 104 106 108 110

• 2
• 1

1 2

250Fm 254No

mc2 / MeV

270Ds 266Hs 262Sg 258Rf

/StrukturSWK/Abbildungen/Massen, F.P. Heßberger, 3.9.2013

Atomic Number Atomic Number (mc2(exp)- mc2(theo)) / MeV

Smolanczuk et al. [SmS95a] Myers et al. [MyS96] Kuora et al. [KoT05] Möller et. al. [MöN95]

248Fm 252No 256Rf 260Sg 264Hs

courtesy F. P. Hessberger

337 (2012) 1207 Experimental Muntian (mic-mac) Z=114 N=184 Möller FRDM Z=114 N=184 TW-99 Z=120 N=172 SkM* Z=126 N=184

No

SHIPTRAP: Probing the Strength of Shell Effects

d2n(N,Z) = 2B(N,Z) – B(N-2,Z) – B(N+2,Z)

SHIPTRAP: Probing the Strength of Shell Effects

d2n(N,Z) = 2B(N,Z) – B(N-2,Z) – B(N+2,Z)

Upgrades and Improvements

Upgrades and Combinations

• Novel experiments
• trap-assisted nuclear decay spectroscopy
• laser spectroscopy (in gas cell / gas jet)
• gas-phase chemistry (in gas cell / ion trap)
• Increase efficiency and sensitivity
• cryogenic gas cell
• novel measurement schemes (PI-ICR)
• single-ion mass measurements (FT-ICR)

(→ TRIGA-TRAP, TRAPSENSOR)

Cryogenic Gas Stopping Cell

• Larger stopping volume and Coaxial injection of reaction products
• Higher cleanliness due to cryogenic operation
• Larger gas density at a lower absolute pressure

Advantages compared to 1st generation gas cell: DC-Cage RF-Funnel 40K 20mbar He DC-Cage RF- Funnel 300K 60mbar He Cryo Cell Gas Cell 320mm 450mm 400mm

• C. Droese et al. NIM B 338, 126 (2014)

• Larger stopping volume and Coaxial injection of reaction products
• Higher cleanliness due to cryogenic operation
• Larger gas density at a lower absolute pressure

Advantages compared to 1st generation gas cell: DC-Cage RF-Funnel 40K 20mbar He DC-Cage RF- Funnel 300K 60mbar He Cryo Cell Gas Cell 320mm 450mm 400mm

• C. Droese et al. NIM B 338, 126 (2014)

Cryogenic Gas Stopping Cell

Phase-Imaging Ion-Cyclotron-Resonance Technique

Recent Breakthrough

Destructive time-of-flight detection Spatially resolved detection Delay-line detector

• S. Eliseev et al., Appl. Phys. B114, 107 (2014)

ions Delay-Line Detector by Roentdek R Φ R

tR R t    n      2

t n n   2 2  

Independent Measurements

• f Eigenfrequencies n+ and n-

Radial excitation Determination of the spatial distribution Radial excitation followed by a phase accumulation time

Phase-Imaging Ion-Cyclotron-Resonance Method

• S. Eliseev et al., Phys. Rev. Lett. 110, 082501 (2013)

Laser-ablation Ion source

superconducting magnet MCP- detector purification trap

Penning traps

measurement trap laser beam different samples

SHIPTRAP Off-line Setup

Position-sensitive Delayline Detector

Active diameter 42 mm Channel diameter 25 mm Open area ratio >50 % Position resolution 70 mm

• Max. B-field

a few mT Time resolution ~ 10 ns

image of magnetron motion (G ≈ 20) 8 mm 1 mm

(RoentDek GmbH DLD40)

Increased Precision with Phase Method

d[M(132Xe) - M(131Xe)] ~ 70 eV !!!

ToF-ICR (Ramsey)

10-hour measurements

PI-ICR

d[M(124Xe) - M(124Te)] ~ 300 eV Gain in Precision ≈‏4.5‏!!!

Veryfying the Accuracy of PI-ICR M = M(132Xe) - M(131Xe) MSHIPTRAP - MFSU = (8 ± 35) eV d(M)SHIPTRAP = (30stat )( 12sys) eV

Selected SHIPTRAP Results with the PI-ICR Technique

Neutrino Mass Determination

• absolute mass and mass hierarchy of neutrinos still an open question
• present limits: m(ne < 2 eV / m(ne < 225 eV

K.A. Olive et al. (Particle Data Group), Chin. Phys. C, 38, 090001 (2014).

Different experimental approaches:

• search for neutrinoless double beta transformation processes
• cosmology
• direct (anti)neutrino mass determination aiming at sub-eV uncertainty
• spectrometry (KATRIN: 3H b decay )
• calorimetry (MARE: 187Re b decay; ECHo ,HOLMES: 163Ho EC)

required: independent measurement of Q - value (mass difference) with accuracy on the order of eV

• Fig. from G. Drexlin, V. Hannen, S. Mertens, and C. Weinheimer

Advances in High Energy Physics Volume 2013 (2013)

b- decay Spectrum Measurement

b--decay of 3H; Q-value ≈ 18.6 keV b--decay of 187Re; Q-value ≈ 2.47 keV

KATRIN MARE

187Re b Decay Q - Value

b--decay of 187Re; Q-value ≈ 2.47 keV

SHIPTRAP results 187Re/187Os mass difference

• D. Nesterenko et al., Phys. Rev. C 90, 042501(R) (2014)

187Re b—decay Q - value=2492(30)(15) eV

SHIPTRAP:

SHIPTRAP result confirms latest micro-calorimeter results

• D. Nesterenko et al., Phys. Rev. C 90, 042501(R) (2014)

187Re b Decay Q - Value

ANALYSIS of DE-EXCITATION SPECTRUM

mn

163Ho 163Dy + Ec+ ne (En)

Electron Capture in 163Ho

Holmes: B. Alpert et al., Eur. Phys. J. C 75 (2015) 112 ECHo: L. Gastaldo et al., J. Low Temp. Phys. 176 (2014) 876

EC in 163Ho; Q-value ≈ 2.55 keV (AME 2012)

EC

direct measurement of mass difference

163Ho-163Dy can clarify situation

1982 J.U. Andersen et al. 1983 P.A. Baisden et al. 1984 E. Laegsgaard et al. 1985 Hartmann & Naumann 1986 S. Yasumi et al. 1992 Hartmann & Naumann 1993 F. Bosch et al. 1994 S. Yasumi et al. 1997 F. Gatti et al. 2013 ECHo

Q-value of EC in 163Ho Statistical sensitivity to mn

taken from A. Nucciotti, arXiv: 1405.5060v2

0.4 eV

163Ho EC Decay Q - Value

Laser Spectroscopy of the Heaviest Elements

Principles of Resonant Laser Ionization

Adapted from K. Wendt / C. Geppert

Radiation Detected Resonance Ionization Spectroscopy

Search for Atomic Transitions in Nobelium

Theoretical predictions for the 1S0-1P1- transition in the element nobelium

[1],[2]: S. Fritzsche, Eur. Phys. J. D 33 (2005) 15 [3]: A. Borschevsky et al., Phys. Rev. A 75 (2007) 042514 [4]: Y. Liu et al., Phys. Rev. A 76 (2007) 062503 [5]: P. Indelicato et al., Eur. Phys. J. D 45 (2007) 155 [6]: J. Sugar, J. Chem. Phys. 60 (1974) 4103

• RIS with two step excitation and

non-resonant second step

• search for 1P1 level in range

predicted by different theories

• determine IP via Rydberg series
• Measure isotope shift of 1P1-

1S0

transition (Z=102)

10 cm

• Detector

Filament (Tantal)

+ + +

Recoil Beam

Laser Beams

n1 n

a

Buffer Gas

Resonant Ionization Laser Spectroscopy of Nobelium

Pulsed

1 2 3 4 5 6 Collecting on Detector Collecting on Filament

Beam off Beam on

Time [s]

Heat Pulse Lasers

Laser System

Laser Systems

M.Laatiaoui et al., Hyp. Int. (2013) DOI: 10.1007/s10751-013-0971-x

RADRIS-optimization: on-line experiments (155Yb)

experiments on the chemical homolog Yb allow:

• ptimization of full setup
• localizing the atom cloud
• monitoring of overall efficiency during level-search in nobelium
• verall efficiency 1% achieved

λ2 = 351 nm Laser 1 Laser 2 λ1 = 398.9 nm

2-step excitation 155Yb

• measure residual activity on filament
• determine filament temperature for evaporation
• Desorption enthalpy of No from Ta:

246±24 kJ/mol

Evaporation of 254No from Ta Filament

M.Laatiaoui et al., Eur. Phys. J. D 68 (2014) 71

254No

Future Perspectives

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: R.-D. Herzberg (Univ. Liverpool) Deputy:

• M. Block (GSI/HIM/JGU)

Technical Director:

• A. Yakushev (GSI)

Currently includes 9 German and 17 international institutes Endorsed by NUSTAR Collaboration Committee:

• Sept. 25, 2014

submission to FAIR management: summer 2015

Staged Approach towards cw linac for SHE

• 1. Full performance test of sc

cw LINAC Demonstrator

• @GSI HLI
• proof of principle
• 2. Full performance test of a

shorter sc cavity

• energy variation (by Ampl &

Phase)

• 8 gaps
• simpler design
• easier to fabricate
• 3. Advanced Demonstrator
• up to 4.61 MeV/u @ A/Q = 6
• 5× sc CH-Cavity, 5× sc Solenoid
• possible to place in HLI@GSI

1 3 2

Courtesy of V. Gettmann / W. Barth

cooperation: GSI, HIM, Uni Frankfurt

First components – October 2014

Courtesy of V. Gettmann / W. Barth

• Direct high-precision mass measurements provide complementary tools to

map nuclear structure effects in the heaviest elements

• Increased resolving power and higher precision of novel PI-ICR method
• pens the door for applications in fundamental physics
• Laser spectroscopy for Z > 100 allows studying the impact of relativistic

effects on the atomic structure

• Laser spectroscopy will also provide information of nuclear properties such

as spins, moments, and changes in charge radii (model independent)

• stepwise approach for new cw-linac underway -> GSI will maintain leading

position in SHE research

Summary and Conclusions

Thank you for your attention !