Lecture Series: Atomic Physics Tools in Nuclear Physics IV. High-Precision Penning Trap Mass Spectrometry

Transcription

1 Euroschool on Physics with Exotic Beams, Mainz 005 Lecture Series: Atomic Physics Tools in Nuclear Physics IV. High-Precision Penning Trap Mass Spectrometry Klaus Blaum Johannes Gutenberg-University Mainz and GSI Darmstadt, Germany

2 Mass and Energy Energy Mass equivalence Einstein 1905: = N + Z + Z binding energy High-precision mass measurements convey information on nuclear and atomic binding energies

3 Applications Field Mass uncert. δm/m General physics and chemistry 10-6 Nuclear physics Decay energies Binding energies 10-7 Nuclear structure Shell closure, pairing Deformation, halos Nuclear models and formulas Isobaric-multiplet mass equation (IMME) r, rp process Fundamental studies Symmetry tests Weak interaction studies (CVC hypothesis)

4 TOF Cyclotron Resonance Curve 390 TOF as a function of the excitation frequency Mean time of flight / µs Determine atomic mass from frequency ratio with a well-known reference mass. Centroid: f c = 1 q B π m f rf 63 Ga T 1/ = 3.4 s Excitation frequency ν RF / Hz f c,ref f c = m - me m - m ref e

5 Triple-Trap Trap Mass Spectrometer ISOLTRAP 0 3 Ar MCP 5 Me a n TOF (µs) cm 10 cm ν RF (Hz) precision Penning trap B = 5.9 T 1. m MCP 3 precision Penning trap determination of cyclotron frequency (R = 10 7 ) preparation Penning trap stable alkali ion reference source stable alkali ion reference source cooling Penning trap B = 4.7 T MCP 1 removal of contaminant ions (R = 10 5 ) ISOLDE beam (DC) 60 kev RFQ structure.8-kev ion bunches F. Herfurth, et al., NIM A 469, 64 (001) K. Blaum et al., NIM B 04, 478 (003) HV platform ion beam cooler and buncher carbon cluster ion source C 60 pellet laser beam Nd:YAG 53 nm cluster ion source

6 ISOLTRAP Setup 1 m

7 10-4 Coparison of Direct MS Techniques relative uncertainty CSS ESR SMS CPT ISOLTRAP JYFL COOL ESR IMS SPEG MISTRAL G. Audi et al., Nucl. Phys. A 79, 337 (003) D. Lunney et al., Rev. Mod. Phys. 75, 101 (003). half life (seconds)

8 The Mass of of Ne Ne 17 Ne How to probe that 17 Ne is a proton halo? Via the nuclear charge radii! T 1/ = 109 ms Yield = 1000/s 40 δm < 0.5 kev δν Isotope-shift measurements: A, A' IS = A' A ( KNMS + KSMS ) + Fel. δ MA' MA A' A δ r M M nuclear charge radii r A' A Mean time of flight Mass uncertainty of δm /m < (< kev) required! Ne (465 ions / 1h) ν c / Hz

9 Solving the Identification Puzzle in 70 Cu Isomerism in 70 Cu: Hyperfine structure of 70 Cu isomers (using laser ionization): I π E / kev T 1/ / s (6-) 4.4(3) 6.6() Intensity ratio: IT 5% β 95% 16% 80% 4% (3-) 101.1(3) 33() IT 50% β 50% (1+) () normalized to the area Mass excess Lit: -630(15) kev β =100%

10 Identification of Triple Isomerism in 70 Cu Intensity ratio: 16% 80% 4% Mean TOF / µs (6 ) state = gs q ω c = m B normalized to the area Unambiguous state assignment! ME of ground state is 40 kev higher than literature value! J. Van Roosbroeck et al., Phys. Rev. Lett. 9, (004). R , δm/m For the first time: Nuclear spectroscopy by mass spectrometry! Mean TOF / µs Mean TOF / µs (3 ) state = 1.is 4(3) kev ν c / Hz 101(3) kev with cleaning of 6 state 1 + state =.is

11 Superallowed β-decay and the Standard Model Conserved-vector vector-current current hypothesis: Vector part of weak interaction not influenced by strong interaction tion Intensity of β decays (ft( value) only a function of the vector coupling constant and the matrix element: ft = G V K M V K Product of fund. constants G V Vector coupling constant M V - Nuclear matrix element Corrections: to the statistical rate function f δ C isospin symmetry breaking correction (Coulomb force, strong force) to the nuclear matrix element M V : δ R radiative correction (bremsstrahlung etc.)

12 Experimental Access to Ft Values 5 Ft = Ft ( Q,T, b, P, δ 1/ EC R, δ C ) Q Decay energy mass m T 1/ Half-life life b Branching ratio P EC Electron capture fraction δ R Radiative correction Isospin symmetry breaking correction δ C Weak Interaction symmetry tests, CVC hypothesis δm/m < Unitarity of the CKM matrix d' s' b' Vud Vus Vub d G V = Vcd Vcs Vcb s V ud = b G Aµ Vtd Vts Vtb Mean Ft value of all decay pairs contributes to V ud via G V Can check unitarity via sum of squares of elements of the first row

13 Results Ft Values ISOLTRAP mass measurements Mg? Na : δq=0.8 kev, 34Ar? CVC hypothesis confirmed in this mass region 34Cl : δq=0.41 kev, 74Rb? 74Kr : δq=4.5 kev [I.S. Towner & J.C. Hardy, Phys. Rev. C 71, (005)] LEBIT 38Ca Mg 34Ar JYFLTRAP 74Rb CPT 46V 6Ga F. Herfurth et al., Eur. Phys. J. A 15, 17 (00) A. Kellerbauer et al., Phys. Rev. Lett.93, 0750 (004) M. Mukherjee et al., Phys. Rev. Lett. 93, (004) T. Eronen et al., to be published (005) G. Savard et al., to be published (005)

14 Status CKM Matrix Check unitarity via elements of the first row: V ud + V us + V ub = 1 + Δ V us and V ub from particle physics data (K( and B meson decays) From nuclear β decay (world average 005): V ud obtained from avg. Ft and G A from muon decay = (14) From neutron decay: V ud obtained from neutron β decay asymmetry A and lifetime τ Δ = (7). (RPP world average 00) [I.S. Towner & J.C. Hardy, submitted to Phys. Rev. C (005)] Δ = (8). [H. Abele et al., PRL 88 (00) 11801]

15 Solution to the Non-Unitarity Problem Present status: V ud (nuclear β-decay) = (4) V us (kaon-decay) = 0.00(6) V ub (B meson decay) = (5) Contribution to the unitarity: Hardy005 PDG004 V ub V us % 0.05% New measurement of V us from K e3+ decay V us = 0.7(30) V ud 99.95% = (16) [A. Sher et al., PRL 91 (003) 6180] New measurement of V us from K L decay V us = 0.5(3) BUT [T. Alexopoulos et al., PRL 93 (004) 18180] in disagreement with previous K e3+ decay data in disagreement with K e30 decay data [RPP 00: V us = 0.196(6)] [A. Lai et al., arxiv:hep-ex/ ]

16 g-factor of the Proton and Antiproton Test of CPT invariance magnetic moment (g - ) e + e - CPT ψ : Reversal of space, charge, and time Currently believed to hold CPT transforms particle into its antiparticle (P. Dirac 198) (g - ) q/m charge/mass mass difference 1s s two-photon spectroscopy µ + µ - e + e - p p K 0 K 0 H H rel. precision µ µ p N = g p s h ω c = e m p B Cyclotron frequency g p = ω ω L c ω L = g e m B Larmor frequency p p

17 The Proton and Antiproton Penning Trap PDG: g p = (9) g p =.800(8) Double Penning trap technique: We aim for δg/g = precision trap: homogeneous magnetic field for measurement of B via ν c and induction of spin flips magnetic field lines analysis trap: inhomogeneous field for detection of spin direction electric potential analysis trap precision trap 0 cm LHe temperature: single-ion detection small amplitudes extreme ultra-high vacuum long storage time GSI University of Mainz collaboration

18 MATS at NUSTAR / FAIR Precision Measurements of very-short lived nuclei using an Advanced Trapping System for highly-charged ions (similar to the TITAN Proposal for TRIUMF) f c 1 = π q m B decay & laser spectroscopy TOF Ion production FRS Low Energy Branch RFQ EBIT Mass Analyzer Preparation Penning trap Precision Penning trap νc ν Time-of-flight detector Q RFQ trap: Beam bunching EBIT: charge breeding q/m selection: separation MATS Technical Proposal, accepted by the FAIR-PAC (005) Cooler trap: beam preparation Precision trap: measurements Detectors: -FT-ICR -TOF-ICR -Si(Li)

19 Summary of Lecture IV The development of a carbon cluster-comb comb was a breakthrough in mass spectrometry of radionuclides. ISOLTRAP can perform high-precision mass measurements (<10-8 ) on very short-lived nuclides (<100 ms) that are pro- duced with very low yields (<100 ions/s); δm( Na) = 160 ev Such high-precision mass measurements can provide valuable input to nuclear structure and fundamental studies preparation of isomerically pure beams for further experiments Great potential for further measurements with even increasing sensitivity and precision and yet shorter half-lives! lives! Thanks a lot for your attention.