1 stephan ettenauer for the TITAN collaboration Experimental Program on Halo Nuclei with non-accelerated Beams at TRIUMF Weakly Bound Systems in Atomic and Nuclear Physics, March 2010

2 Outline Overview: Experimental Probes on Halo Production of Halo Nuclei non-accelerated TRIUMF – Laser Spectroscopy – Mass Measurements in Penning Trap Conclusion & Outlook TRIUMF

3 Halo Nuclei Two-proton halo One-neutron halo Two-neutron halo One-proton halo Four-neutron halo Binary system K. Tanaka et al., PRL 104, (2010) 22 C In 1985 Tanihata et al.: interaction cross section measurements (transmission experiment) 11 Li much larger than expected from general rule of stables: R N ~r 0 A 1/3 extra neutrons (or protons) in classically forbidden region I. Tanihata et al., PRL 55, 2676 (1985) Transmission Experiment T. Nakamura et al., PRL 103, (2009) 31 Ne New Candidates: would be heaviest nuclear halo system possibly p - wave 1n halo S 2n =10 keV S 2n =420 keV ⇒ mass required

4 beta Experimental Probes for Halos 4 Reaction Cross Sections Transfer Reaction Knockout Reactions Elastic Scattering Breakup Magnetic Moment Beta Decay Beta Delayed Particle Emission accelerated beams model depend. stopped or low E beam Mass Atomic Laser Spectroscop y this talk

5 Rare Isotope Production Beam cooler * ~ 60 keV ~ 10 MeV/u Experiments ~ 10 MeV/u ~ 100 MeV/u ExperimentsBeam cooler ~ 20 keV Charge- breeder Charge- breeder ISOL (TRIUMF, slow (~5 ms) BUT high intensityLow beam energy, ideal for decay and trap exp.Good beam quality (even cooled) & purityPost-acceleration for reaction studiesBUT element selective ionization ⇒ some elements not possible! In-Flight (MSU, GSI, RIKEN, GANIL):Production: fast, no chemistry involvedHigh beam energy, ideal for reaction exp.Life-time, masses, & basic discoveryLow intensity, poor beam quality & purity

6 TRIUMF TITAN (mass) collinear LS for 11 Li: W. Nörtershäuser et al.(GSI) 500 MeV protons target & ion source high resolution mass separator magnet pre-separator magnet to experiments ISOL-facility <60 keV nuclide yield [1/s]T 1/2 6 He2.00E ms 8 He ms 11 Li ms 11 Be1.90E s

7 Techniques: (anti)collinear LS two photon resonant LS LS of individual atoms in MOT } Charge Radius relative measurement ⇒ need reference: electron scattering (only possible with stables) Isotope Shift Mass shift Field Shift / Finite Size Shift Z.-C. Yan et al., PRL 100, (2008) atomic laser spectroscopyhigh precision atomic physics calculation with nuclear mass: need δδm < 1keV short lived (<10 ms) ⇒ Penning Traps for He, Li, Be: MS ∼ 10 GHz ⇔ FS ∼ 1 MHz in-beam

8 Laser spectroscopy of 11 Li R. Sanchez et al., PRL 96, (2006) from ISAC A Li + overall efficiency: 10 -4

9 Measurement Principle atomic level scheme: Li 1) 11 Li + from ISAC 2) neutralized in hot C - foil 3) two photon resonance 2s→3s spontaneous decay 3s→2p second laser: 2p→3d ionization detection of ions R. Sanchez et al., PRL 96, (2006) ⇒ Doppler free ⇒ scanν 0 broad narrow (transition of interest)

10 Spectra R. Sanchez et al., PRL 96, (2006) 6 Li 11 Li

11 M. Puchalski et al., PRL 97, (2006) Results R. Sanchez et al., PRL 96, (2006) isotope shifts 7 Li- A Li: 2s→3s reference r c ( 7 Li) = 2.39(3) fm At. Data Nucl. Data Tables 14, 479 (1974) Z.-C. Yan et al., PRL 100, (2008) mass shifts r c ( 11 Li) = 2.423(17)(30) fm reference r c mass: MISTRAL (2005) r c ( 11 Li) = 2.465(19)(30) fm mass: AME‘03 ! need mass !

12 TITAN ISAC beam: A + Penning traps: highest precision previously shortest 74 Rb with T 1/2 =65 ms CERN but 11 Li T 1/2 = 8.8 ms A. Kellerbauer et al., PRL 93, (2004) 1$CAN masses of halos: reflect binding energy separation energy: S n, Sp input to extract physical quantities from exp. (e.g. r c )

13 confinement: –strong axial, hom. B-field (3.7 T) –electrostatic quadrupolar field 3 eigenmotions cyclotron frequency quadrupolor rf- field (ring electrode) leads to conversion: magnetron ↔ reduced cyclotron radial energy: B Measurement Principle

14 initial magnetron preparation –dipolar RF excitation ~ 10 ms –Lorentz steerer quadrupolor rf- field extraction: through B-field E r to E l E l measured by TOF minimum at  c comparison to well known isotope Mass measurements in the MPET 10

15 Precise & Accurate accurate, but not precise precise, but not accurate line width (FWHM): ⇒ resolution: ⇒ even for T rf ∼ 10ms exact theoretical description even for non-ideal traps off-line tests with stables ⇒ control over systematics for TITAN: < 5 ppb possible L.S. Brown and G. Gabrielse, Rev. Mod. Phys. 58, 233 (1986) G. Bollen et al., J. Appl. Phys. 88, 4355 (1990) M. König et al., Int. J. Mass Spect. 142, 95 (1995)Int. J. Mass Spect. 142, 95 (1995) M. Kretzschmarr, Int. J. Mass Spect. 246, 122 (2007) G. Bollen et al., J. Appl. Phys. 88, 4355 (1990) G. Gabrielse, PRL 102, (2009) M. Brodeur et al, PRC 80, (2009) 6 Li

16 Mass of 11 Li M. Smith et al., PRL 101, (2008) 11 Li ReferenceMass [u] AME’ (21) MISTRAL (54) TITAN (69) r c ( 11 Li) = 2.427(16)(30) fm eliminates mass as source of uncertainty! two neutron separation energy: S 2n = -M(A,Z) + M(A-2,Z) + 2n asymptotic waveform for Borromean system soft electric-dipole excitation models of 11 Li: adjust 9 Li-n interaction T. Nakamura et al., PRL 96, (2006)

17 Other Halos: Laser Spectroscopy P. Mueller et al., PRL 99, (2007) 6 He and 8 He Argonne Lab / GANIL LS in MOT all in MHz mass: dominating uncertainty W. Nörtershäuseret al., PRL 102, (2009) 811 Be: GSI collinear LS δm=6.4 keV (AME’03)

18 TITAN: 6 He & 8 He M. Brodeur et al., in prep.V. L. Ryjkov et al., PRL 101, (2008) 2 nd 8 He mass meas. 1 st 8 He mass meas. 6 He mass meas. New masses (M.E.=m-A) 1.7σ 4.0σ 4 He 6 He 8 He S. Bacca et al., Eur. Phys. J. A 42, 553 (2009) comparison to theory: need 3N interactions

19 TITAN: 11 Be R. Ringle et al., PLB 675, 170 (2009) mass ref. mass ex.[kev] δ MS ( 9 Be- 11 Be) 2s 1/2 → 2p 1/2 AME’ (6.4) (9) TITAN’ (58) (13) ⇒ confirms AME & improves precision ⇒ uncertainty of mass negligible for r c P. Mueller et al., PRL 99, (2007)

20 12 Be S. Ettenauer et al., PRC 81, (2010) calculation & measurement of r c in the near future → see talk of Thomas Neff T 1/2 = 24 ms ~ ions/s detectable at yield station  measurement possible TITAN: m.e.= (2.1) keV

21 Conclusions Interplay of various experimental approaches allow to identify & probe nuclear halos Combination of high precision –laser spectroscopy –mass measurements –atomic physics calculation benchmark theoretical models (mass, matter/charge radius,..) later this year: electric quadrupole moment of 11 Li TITAN: masses –to investigate established halos 14 Be(2n), 19 C(1n), 17 Ne(1p) –needed to decide if halo structure in 22 C and 31 Ne ⇒ charge radius } Outlook (TRIUMF)

22 TITAN collaboration M. Brodeur, T. Brunner, S. Ettenauer, A. Gallant, V. Simon, M. Smith, A. Lapierre, R. Ringle, V. Ryjkov, M. Simon, M. Good, P. Delheij, D. Lunney, and J. Dilling for the TITAN collaboration

23 Backup Slides

24 AC Stark Effect R. Sanchez et al., PRL 96, (2006)

25 6 He and 8 He: Laser Spectroscopy

26 He: Comparison with theory Both the GFMC & NCSM r c agrees with new exp. 6,8 He r c Method that provides the closest values to experiment Only method that uses 3 nucleons interaction (3NI) GFMC 2NI 3NI NCSM Produce a physical r c for an unbound nuclei, consequence of using faster Gaussian fall-off and small model space. !

27 11 Be: Laser Spectroscopy W. Nörtershäuseret al., PRL 102, (2009)

28 11 Be: Comparison to Models