1 stephan ettenauer for the titan collaboration experimental program on halo nuclei with...
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stephan ettenauer for the TITAN collaboration
Experimental Program on Experimental Program on
Halo Nuclei Halo Nuclei with non-accelerated Beams at TRIUMFwith non-accelerated Beams at TRIUMF
Weakly Bound Systems in Atomic and Nuclear Physics, March 2010
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Outline
•Overview: Experimental Probes on Halo•Production of Halo Nuclei•non-accelerated Halos @ TRIUMF
– Laser Spectroscopy– Mass Measurements in Penning Trap
•Conclusion & Outlook
TRIUMF
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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, 062701 (2010)
22C
In 1985 Tanihata et al.:•interaction cross section measurements(transmission experiment)•11Li much larger than expected from
general rule of stables: RN ~r0 A1/3 •extra neutrons (or protons)in classically forbidden region
I. Tanihata et al., PRL 55, 2676 (1985)
Transmission Experiment
T. Nakamura et al., PRL 103, 262501 (2009)
31Ne
New Candidates:
would be heaviest nuclear halo systempossibly p - wave 1n halo
S2n=10 keV
S2n=420 keV
⇒ mass required
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beta
Experimental Probes for Halos
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ReactionCross Sections
TransferReaction
KnockoutReactions
ElasticScattering
Breakup
MagneticMoment
Beta Decay
Beta DelayedParticle Emission
•accelerated beams•model depend.
stopped orlow E beam
Mass
Atomic LaserSpectrosco
py
this talk
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Rare Isotope Production
Beam cooler
*
~ 60 keV
~ 10 MeV/uExperiments Experiments Experiments
~ 10 MeV/u~ 100 MeV/u
ExperimentsBeam cooler
~ 20 keV
Charge-
breeder
Charge-
breeder
ISOL (TRIUMF, ISOLDE@CERN):Production: 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
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ISAC @ TRIUMF
TITAN(mass)
collinear LS
for 11Li: W. Nörtershäuser et al.(GSI)
500 MeV protons
target &ion source
high resolution mass separator magnet
pre-separatormagnet
to experiments
ISOL-facility
<60 keV
nuclide yield [1/s] T1/2
6He 2.00E+07 807 ms8He 49000 119 ms11Li 15000 8.8 ms
11Be 1.90E+06 13.8 s
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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, 243002 (2008)
atomic laser spectroscopy high 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
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Laser spectroscopy of 11Li
R. Sanchez et al., PRL 96, 033002 (2006)
fromISAC
ALi+
overall efficiency:10-4
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Measurement Principle
atomic level scheme: Li
1) 11Li+ from ISAC2) neutralized in hot C - foil3) two photon resonance 2s→3s
4) spontaneous decay 3s→2p5) second laser: 2p→3d6) ionization7) detection of ions
R. Sanchez et al., PRL 96, 033002 (2006)
⇒ Doppler free
⇒ scanν0
broad
narrow (transition of interest)
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Spectra
R. Sanchez et al., PRL 96, 033002 (2006)
6Li 11Li
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M. Puchalski et al., PRL 97,133001 (2006)
Results
R. Sanchez et al., PRL 96, 033002 (2006)
isotope shifts 7Li-ALi: • 2s→3s• reference rc(7Li) = 2.39(3) fm
At. Data Nucl. Data Tables 14, 479 (1974)
Z.-C. Yan et al., PRL 100, 243002 (2008)
mass shifts
rc (11Li) = 2.423(17)(30) fm
reference rc
mass: MISTRAL (2005)
rc (11Li) = 2.465(19)(30) fm
mass: AME‘03
! need mass !
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TITAN
ISAC beam: A+
Penning traps: •highest precision•previously shortest 74Rbwith T1/2=65 ms ISOLTRAP @ CERN
•but 11Li T1/2 = 8.8 ms
A. Kellerbauer et al., PRL 93, 072502 (2004)
1$CANmasses of halos:•reflect binding energy•separation energy: Sn, Sp•input to extract physical quantities from exp. (e.g. rc )
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• 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
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• initial magnetron preparation– dipolar RF excitation ~ 10 ms– Lorentz steerer
• quadrupolor rf- field• extraction: through B-field Er to El
• El measured by TOF • minimum at νc
• comparison to well known isotope
Mass measurements in the MPET
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Precise & Accurate
accurate, but not precise
precise, but not accurate
line width (FWHM):
⇒ resolution:
⇒ even for Trf ∼ 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)M. Kretzschmarr, Int. J. Mass Spect. 246, 122 (2007)
G. Bollen et al., J. Appl. Phys. 88, 4355 (1990)G. Gabrielse, PRL 102, 172501 (2009)
M. Brodeur et al, PRC 80, 044318 (2009)
6Li
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Mass of 11Li
M. Smith et al., PRL 101, 202501 (2008)
11Li
Reference Mass [u]
AME’03 11.043 798(21)
MISTRAL 2005 11.043 715 7(54)
TITAN 2007 11.043 723 61 (69)
rc (11Li) = 2.427(16)(30) fm
eliminates mass as source of uncertainty!two neutron separation energy:
S2n = -M(A,Z) + M(A-2,Z) + 2n•asymptotic waveform for Borromean system•soft electric-dipole excitation
•models of 11Li: adjust 9Li-n interaction
T. Nakamura et al., PRL 96, 252502 (2006)
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Other Halos: Laser Spectroscopy
P. Mueller et al., PRL 99, 252501 (2007)
6He and 8He•Argonne Lab / GANIL•LS in MOT
all in MHz
mass: dominating uncertainty
W. Nörtershäuseret al., PRL 102, 062503 (2009)
811Be:•GSI•collinear LS
δm=6.4 keV (AME’03)
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TITAN: 6He & 8He
M. Brodeur et al., in prep.V. L. Ryjkov et al., PRL 101, 012501 (2008)
2nd 8He mass meas.1st 8He mass meas. 6He mass meas.
New masses (M.E.=m-A)
1.7σ 4.0σ
4He
6He
8He
S. Bacca et al., Eur. Phys. J. A 42, 553 (2009)
comparison to theory: need 3N interactions
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TITAN: 11Be
R. Ringle et al., PLB 675, 170 (2009)
mass ref.
mass ex.[kev]
δMS (9Be-11Be) 2s1/2 → 2p1/2
AME’0320 174.1(6.4)
31 560.05(9)
TITAN’09
20 177.60(58)
31 560.086(13)⇒confirms AME & improves precision
⇒uncertainty of mass negligible for rc
P. Mueller et al., PRL 99, 252501 (2007)
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12Be
S. Ettenauer et al., PRC 81, 024314 (2010)
calculation & measurement of rc in the near future → see talk of Thomas Neff
T1/2 = 24 ms ~30-300 ions/s
detectable at yield station measurement possible TITAN: m.e.=25
078.0(2.1) keV
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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 11Li• TITAN: masses
– to investigate established halos 14Be(2n), 19C(1n), 17Ne(1p)
–needed to decide if halo structure in 22C and 31Ne
⇒ charge radius}Outlook (TRIUMF)
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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
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Backup SlidesBackup Slides
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AC Stark Effect
R. Sanchez et al., PRL 96, 033002 (2006)
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6He and 8He: Laser Spectroscopy
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He: Comparison with theory
Both the GFMC & NCSM rc agrees with new exp. 6,8He rc Method that provides the closest values to experimentOnly method that uses 3 nucleons interaction (3NI)
GFMC2NI
3NINCSM Produce a physical rc for an unbound nuclei, consequence of using faster Gaussian fall-off and small model space.
!
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11Be: Laser Spectroscopy
W. Nörtershäuseret al., PRL 102, 062503 (2009)
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11Be: Comparison to Models