In-trap decay and trap-assisted decay spectroscopy at ISOLTRAP

Transcription

1 In-trap decay and trap-assisted decay spectroscopy at ISOLTRAP ISOLTRAP experimental setup In-trap decay: principle application for mass measurements Trap-assisted decay spectroscopy: principle and purpose proposed setup 1st physics cases Summary and outlook Magdalena Kowalska, CERN PH-Dept., ISOLDE

2 Collaboration G. Audi, S. Baruah, D. Beck, K. Blaum, G. Bollen, M. Breitenfeldt, M. Dworschak, S. George, U. Hager, F. Herfurth, A. Herlert, A. Kellerbauer, H.-J. Kluge, D. Lunney, S. Schwarz, R. Savreux, L. Schweikhard, C. Yazidjian,..., and the ISOLTRAP and ISOLDE collaboration The funding and support: BMBF, GSI, CERN, ISOLDE, EU networks EUROTRAPS, EXOTRAPS, NIPNET EU Marie Curie EIF programme

3 ISOLTRAP experimental setup Rb Ar MCP 5 Time of flight [µs] Mean TOF (µs) q ω c = m B Excitation frequency ν [Hz] RF (Hz) stable alkali ion reference source 10 cm Measurement Theoretical Fit m precision Penning trap MCP 3 precision Penning trap determination of cyclotron frequency preparation Penning trap stable alkali ion reference source cooling Penning trap Removal of contaminant ions MCP 1 ISOLDE beam (DC) 60 kev RFQ structure HV platform ion beam cooler and buncher carbon cluster ion source 2.8-keV ion bunches laser beam ISOLTRAP at ISOLDE/CERN C 60 pellet

4 In-trap decay Use: nearly simultaneous ω c measurement for mother and daughter nucleus: -More precise determination of mass differences -Measurements on isotopes of elements unavailable otherwise -Different chemical elements reached without changing ion source or/and target Method: Decay in the buffer-gas-filled preparation trap one of tasks of EURONS TRAPSPEC JRA Important 100 Kinetic energy of recoiling ions: β-decay ev 2 Q / 2 meq Q m + m e recoil Charge state after decay (for singly-charged ions): β+: neutral, e- shake-off needed β-: doubly charged or more 50 z (mm) 0 Half-life Herlert et al., New J. Phys. 7, 44 (2005) U z (V)

5 Mass measurements using in-trap decay suspicion of shell effects at N= Mn -> Fe 28 β - decay K -> 37 Ar β + decay 2 proof of principle

6 Mn and Fe results difference mass excess (ISOLTRAP-AME2003) / kev Mn preliminary gs isomer gs isomer 63 Ge contaminant? mean TOF / µs Fe (ν c Hz) / Hz mass number A 400 Fe difference mass excess (ISOLTRAP-AME2003) / kev preliminary Other possible cases: Xe -> I 32Ar->32Cl mass number A Herlert et al., in preparation

7 Trap-assisted decay spectroscopy Motivation: decay spectroscopy on isomerically and/or isobarically pure beams (purification in the preparation or precision Penning trap) Beyond present tasks of EURONS TRAPSPEC JRA Physics use: -Penning traps used only as purifiers: for beams valuable as isomerically and isobarically pure -Decay spectroscopy used to assist mass measurements and distinguish between species Important: Minimum excitation time (s) to resolve g.s. and isomer Amount of contaminants ISOLTRAP limit ratio: ca.10 3 Mass difference Determines purification time ISOLTRAP limit: ca. 100keV Half-life Decay losses Collected counts Herlert et al., Czech. J. Phys. 56, F287 (2006)

8 Decay spectroscopy planned setup Tape station above last ISOLTRAP Penning trap Beta-, gamma-detection in the air Differential pumping necessary Technical design by Ulrike Hager

9 Decay spectroscopy planned setup Present status channeltron MCP To be exchanged by: tape station entrance MCP precission trap channeltron

10 Decay spectroscopy planned setup Ion path simulations Ulrike Hager GSI Tape station Detectors: Beta plastic scintillators Gamma ISOLDE Ge detectors

11 Decay-spectroscopy 1st physics case Aim: measurements in regions with large amounts of surface-ionised contaminants 1st planned case: excited states in neutron-rich Tl and Pb isotopes Fr contamination Proposal in preparation for INTC meeting in May Physics interest: little data in this region Proton hole neutron interaction Single-particle configurations Possible isomers Bi Pb α,β,9/ α,β, α,9/ α, α,9/ α, Tl α,β,0-207 α,β,1/ α,β, α,(1/2+) 210 α,5+# 211 1/2+# Hg

12 Decay-spectroscopy 1st physics case 207Tl: 81p, 126n π h11/2 π s1/2

13 Decay-spectroscopy physics case 1E+09 1E+08 yield 1E+07 1E+06 1E+05 1E+04 1E+03 1E+02 1E+01 Hg-estimate Fr-measured 1E+00 Tl-estimate 1E-01 Mass number

14 Decay-spectroscopy other cases Isomeric purification: g.s. and isomer not assigned unambiguously known isomer yields (20) known g.s. yields (40) known yields in this isotope chain (20) Tl, Pb, Bi C s In La Pm

15 Summary In-trap decay for mass measurements: Access to elements not produced at ISOLDE First measurements performed Plans for Qb measurements Trap-assisted decay spectroscopy Decay spectroscopy on isobarically and isomerically pure beams Setup in preparation 1st physics cases found Measurements anticipated in 2008

16

17 From: Herlert et al., New J. Phys. 7, 44 (2005) In-trap decay

18 half-live (s) 1.E+21 1.E+18 1.E+15 1.E+12 1.E+09 1.E+06 1.E+03 1.E+00 1.E-03 stable Hg Tl Pb Bi Fr 1.E-06 1.E-09 mass

19 Mg(p,n) 26 Al 26 Mg( 3 He,t) 26 Al Na(α,γ) 27 Al Mass difference / kev % 25 Mg(p,γ) 26 Al 21.68% 26 Mg( 3 He,t) 26 Al - 14 N() 14 O 6.93% 4.22% 42 Ca( 3 He,t) 42 Sc - 26 Mg() 26 Al ame2003 Mass difference / kev Al(p,α) 24 Mg 24 Mg(α,p) 27 Al 16.07% 26 Mg(p,γ) 27 Al Ame Al(p,γ) 28 Si 83.93% Na(α,γ) 27 Al new new? (evaluation in progress...) Mass difference / kev % 27 Al(p,γ) 28 Si 24 Mg(α,p) 27 Al 26 Mg(p,γ) 27 Al 27 Al(p,α) 24 Mg 67.20% 19.94% PT

20 in-trap decay Mn and Fe masses Decay in the buffer-gas-filled preparation trap produced at ISOLDE A ZX not produced at ISOLDE A Z-1 Y + e + Make more radioactive species available Nearly simultaneous ω c c measurement of of mother and and daughter nuclei z (mm) He 4 He 4 He e + 4 He e + 4 He A Z-1Y A Z-1Y A Z-1Y 4 He e + 4 He 4 He A ZX A ZX 4 He A ZX A ZX 4 He A ZX e + e + 20 cm U z (V) Herlert et al., New J. Phys. 7, 44 (2005)

21 Measured

22 Principle of a Penning trap B Cyclotron frequency: ν c 1 = 2 π q m B + q/m Superposition Frans Michel Penning strong homogeneous magnetic field weak electrostatic quadrupole field z 0 r0 PENNING trap

23 Ion motion in the Penning trap Three harmonic eigenmotions Axial oscillation Magnetron motion (slow): ω ωc = Cyclotron motion (fast): 2 2 ω ωc ω c z ω+ = ω ω = + ω 2 c 4 ω c ω z = 2 z ω 2 qv md 0 2 axial (z) magnetron (-) cyclotron (+) A=100, A=100, B=6T B=6T ν MHz MHz ν 1 khz khz ν z z khz khz

24 Mass measurement procedure Scan QP-excitation freq. ν rf about ν c Magnetron excitation Quadrupolar excitation ν rf radial axial energy Time-of-flight (TOF) Time-of-flight [µs] TOF vs. excitation frequency t 1 =TOF 85 Rb t 0 =0 2 m q ω c = m B MCP 5 Measurement Theoretical Fit Excitation frequency [Hz] Determine atom mass from frequency ratio with with a well well known reference Remark: The time-of-flight cyclotron resonance detection has the Advantage: very high resolving power (up to 10 8 ) Disadvantage: destructive! FT-ICR detection method

25 Publications since last DPG-Tagung High-precision mass measurements of nickel, copper, and gallium isotopes and the purported shell closure at N=40, C. Guénaut, et al., Phys. Rev. C, accepted A new Channeltron-detector setup for precision mass measurements at ISOLTRAP, C. Yazidjian et al., Hyperfine Interact., accepted High-accuracy mass measurements of neutron-rich krypton isotopes, P. Delahaye et al., Phys. Rev. C 74, (2006) High-accuracy mass measurements on neutron deficient neon isotopes, A. Herlert et al., AIP Conf. Proc. 831, (2006) ISOLTRAP Mass Measurements for Weak-Interaction Studies, A. Kellerbauer et al.,, AIP Conf. Proc. 831, (2006) Towards high-accuracy mass spectrometry of highly charged short-lived ions at ISOLTRAP, A. Herlert et al., Int. J. Mass Spectrom. 251, (2006) Accurate mass measurements on neutron-deficient krypton isotopes, D. Rodríguez, Nucl. Phys. A 769, 1-15 (2006) Webpage:

26 ISOLTRAP mass measurements in Nuclides measured in in 2004/ Xe, Xe, Xe Xe 127,128, ,128, Sn Sn 118,120, ,120, Cd Cd Kr, Kr, Kr Kr Highlights Mg Mg Na Na K, 43-46, K Zn Zn Nuclide Half-life Uncertainty 17 Ne 22 Mg 109 ms 530 ev 3.86 s 270 ev Ne, Ne, Ne Ne 35 K 178 ms 530 ev 81 Zn 290 ms 3.45 kev

27 Publications since last DPG-Tagung High-precision mass measurements of nickel, copper, and gallium isotopes and the purported shell closure at N=40, C. Guénaut, et al., Phys. Rev. C, accepted Penning trap mass spectrometry for nuclear structure studies, K. Blaum, et al. Hyperfine Interact., accepted Spin-related aspects of mass determination of radionuclides, A. Herlert et al., Czech. J. Phys. 56, F287 (2006), in print A new Channeltron-detector setup for precision mass measurements at ISOLTRAP, C. Yazidjian et al., Hyperfine Interact., accepted High-accuracy mass measurements for a test of the Standard Model, A. Herlert et al., "Proceedings of the EPS-13 Conference 'Beyond Einstein' Physics for the 21st Century" (Bern, July 2005) High-precision mass measurements for reliable nuclear astrophysics calculations, A. Herlert et al., "Proceedings of the International Symposium on Nuclear Astrophysics - Nuclei in the Cosmos - IX" (CERN, June 2006) High-accuracy mass measurements of neutron-rich Kr isotopes, P. Delahaye et al., Phys. Rev. C 74, (2006) High-accuracy mass measurements on neutron deficient neon isotopes, A. Herlert et al., AIP Conf. Proc. 831, (2006) ISOLTRAP Mass Measurements for Weak-Interaction Studies, A. Kellerbauer et al.,, AIP Conf. Proc. 831, (2006) Towards high-accuracy mass spectrometry of highly charged short-lived ions at ISOLTRAP, A. Herlert et al., Int. J. Mass Spectrom. 251, (2006) Accurate mass measurements on neutron-deficient krypton isotopes, D. Rodríguez, Nucl. Phys. A 769, 1-15 (2006) Webpage: