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Laser

Laser cooling of Mg + and laser spectroscopy of HCI @ SPECTRAP. Laser. SpHERe. Zoran Andjelkovic Johannes Gutenberg U niversität Mainz GSI Darmstadt. Laser Sp ectroscopy of H ighly Charged Ions and E xotic R adioactive Nucl e i (Helmholtz Young Investigator Group). Introduction:

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Laser

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  1. Laser cooling of Mg+ and laser spectroscopy of HCI @ SPECTRAP Laser SpHERe Zoran Andjelkovic Johannes Gutenberg Universität Mainz GSI Darmstadt LaserSpectroscopy of Highly Charged Ions and Exotic Radioactive Nuclei (Helmholtz Young Investigator Group)

  2. Introduction: overview of SPECTRAP? trapping cycle Results from ion trapping and laser cooling: fast fourier transfom ion cyclotron resonance single and multiple ion fluorescence trapping time Further plans: for the not so near future and two immediate spectroscopy candidates outline Zoran Anđelković

  3. ion production andTOF • TOF of produced Mg ions • typical energy 100 eV to 1 keV • trap acceptance up to 500 V

  4. view of the trap and the magnet Zoran Anđelković

  5. injection of externally produced ions • dynamic ion capture cycle • low energy and TOF allow selection of captured ions • Option with a cooling mechanism: Stacking of successive ion bunches • 2 ms gate • up to 5 Hz • almost no ion loss Zoran Anđelković

  6. ion motion in a Penning trap • in a harmonic trap all three motions are independent • energy transfer in a non-ideal trap Zoran Anđelković

  7. resistive cooling and non-destructive detection „FT-ICR“ Fourier-Transform Ion Cyclotron Resonance q/m spectrum I I t f ion current signal endcap detect • Passive: - detects ion current • - cools the ion cloud • Active: - excite ions and • induce corr. motion • - heats the ion cloud L R C excite endcap Zoran Anđelković

  8. reduced cyclotron frequency • around 500 trapped and cooled 24Mg ions, excitation ~ 100 mVpp • measured via electronic pickup and fluorescence reduction • a small frequency shift due to the magnetic field imperfection Zoran Anđelković

  9. fluorescence and line profile • identified single ion signal via quantized fluorescence jumps • natural linewidth 42 MHz => final temperature < 1 K • if fully saturated => detection efficiency ~ 5*10-5 a single trapped ion ~ 1500 trapped ions real line profile Zoran Anđelković

  10. trapping time • Graph showing ions ejected and counted with an MCP • fast switched ejection electrode (adiabatic ejection) • additional einzel lense • if ejected after a long time the radial component gets too big • fluorescence showed that the real trapping time is much longer • estimated t1 ~ 100 s => in-trap vacuum ~ 10-11 mbar Zoran Anđelković

  11. further planned measurements final accuracy limited by the Doppler broadening • with resistive cooling Dn/n0 ≈ 10-6 to 10-7 • with sympathetic cooling Dn/n0 ≈ 10-7 to 10-8 Zoran Anđelković

  12. candidate no. 1 X. Feng, …, G. Werth; PRA 46 (1992) 207Pb ( I=1/2 ) 208Pb ( I=0 ) F=2 6 P1 T=1600 K Pb1+ F=1 c a b d e wavelength: 710.172 nm F=1 3 P0 F=0 pro contra • well known transition- no “fancy” ion source needed • „short“ lifetime (41 ms) • - improvement of the magnetic moment - difficult to trap - invisible for pickup detection - „long“ lifetime (41 ms)- how many can we make? Zoran Anđelković

  13. candidate no. 2 3P0-3P1 ... no hyperfine structure transition known from emission spectroscopy Ca14+ wavelength: 569.44 nm pro contra • known transition, but- accuracy can be increased by 3-4 orders of magnitude • “short” lifetime (10 ms) • easy to trap, easy to see • need an EBIT • need a beamline from the EBIT • - transported with 5 keV and needs large deceleration 13 Zoran Anđelković Zoran Anđelković

  14. pulsed elevator electrodes 300 eV; +200 V to -50 V; no mag. field with the magnetic field field – the ions are kept on axis by the field 300 eV; +200 V to -50 V; with mag. field 14 Zoran Anđelković no mag field – phase space conservation makes life difficult Zoran Anđelković

  15. outlook • current status: • UHV system and superconducting magnet in operation • ion trap with cryogenic electronics finished and working • demonstrated laser cooling of Mg+ to sub K temperature • fluorescence detection functioning • successfull ESR measurements of both Bi82+ and Bi80+ • further plans: • install a He recovery system • improve the UHV system (cryopums) • perform cooling and laser spectroscopy on Pb+ • new ion sources – EBIT, MEVVA, HITRAP • measurements on forbidden transitions in mid-Z ions • finally, high precision measurements on Bi82+ and Bi80+ Zoran Anđelković

  16. HITRAP and its experiments • HITRAP parameters: • IH deceleration to 0.5 MeV/u • RFQ deceleration to 6 keV/u • cooler trap decel. to 4 K • mass over charge ≤ 3 • N of extr. part. 106 from ESR 4 MeV/u Zoran Anđelković

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