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ISOLDE RILIS: from proof of principle to a standard versatile technique

ISOLDE RILIS: from proof of principle to a standard versatile technique. By V. Fedosseev CERN, EN-STI-LP. A + + e -. Laser Resonance Ionization of Atoms. P sat. = Ɛ sat. × f laser × S laser beam Ɛ sat. = ћ ω i /2 σ i f laser = 10 kHz Ø laser = 3 mm. Autoionization. E i

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ISOLDE RILIS: from proof of principle to a standard versatile technique

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  1. ISOLDE RILIS: from proof of principle to a standard versatile technique By V. Fedosseev CERN, EN-STI-LP

  2. A+ + e- Laser Resonance Ionization of Atoms Psat. = Ɛsat. × flaser × Slaser beam Ɛsat. = ћωi/2σi flaser = 10 kHz Ølaser = 3 mm Autoionization Ei 4 ÷ 11 eV Continuum DC electric field Blackbody radiation RF IR Collisions 3000 - 1100 Å 0.6 Step 3 Rydberg level Ionization ω3 Ion yield Psat ≈ 10 W 1st or 2nd excited level 0.6 Step 2 ω2 ω1 1st excited level Selective excitation Psat ≈ 100 mW ω1 0.6 Ground atomic level Step 1 ωi(laser) = ωi(atom);Pi(laser) ≥ Pi(saturation) Psat ≈ 10 mW Laser power

  3. Early proposals: 1984 (V. S. Letokhov and V. I. Mishin)

  4. Early proposals: 1988

  5. Ionization in a hot metal cavity Demonstrated: Yb, Nd, Ho - off-line Ho - on-line Yb, Tm, Sn, Li - off-line Yb – on-line

  6. (Richardson equation) Thermo electron emission Fp Plasma potential + 2 eV 0 +U Typical values of U for L=30 mm, d=3 mm, t=1 mm W - 1.5 V Nb - 2 V, 4 V (t=0.5mm) TaC - 3 V Lower j Higher efficiency Higher plasma potential Better extraction Lower temperature Lower thermal ionization Higher selectivity Ions in a hot cavity

  7. P e = Ionisation + P P Ionisation Effusion n e e = rep ion 2dv n e + rep ion 3 L2 Laser Ionization Efficiency Selectivity = Surface Ionization Efficiency elaser = 2% - 30% Hot Cavity Laser Ion Source Efficiency: Laserslocated ~ 18 m away HOT CAVITY TARGET > 5% - alkalies esurface = 0.1% -2% - In, Ga, Ba, lanthanides < 0.1% - others => depends on the ionization potentials of isobar atoms

  8. RILIS RILIS at ISOLDE Facility

  9. Ion beam lines + + + Mass separator Laser system Proton beam 60 kV Extraction Electrode + + Laser beams Ionizer Target Target DC Target - Ion Source Unit RILIS at ISOLDE-PSB CVL lasers: nrep=11.000 Hz Oscillator + 2 amplifiers 2-3 dye lasers with amplifiers, nonlinear crystals BBO:

  10. 287.9 nm Separation of the 3 -decaying isomers in 70Cu ~13 GHz 68mCu 68gCu 327.4 nm 68Cu K. Blaum, PRL vol. 92 (2004) 11 (6-) (3-) (3-) (1+) (1+) Isomer selectivity with RILIS m / g = 20 g / m = 20 Applied also at REX/MINIBALL Worlds first post accelerated isomer purified beams

  11. 511 nm CVL Ei=8.42 eV 6p3 8p 532.34 nm 538.89 nm 6p3 7p 843.39 nm 6p3 7s 5S2 245.01 nm 255.80 nm 6s2 6p43P2 Ground state Po In-source laser spectroscopy Techniques used to detect Po ions: • a – detector with energy resolution • g – detectors • b – counter • Faraday cap 6p3 7s 3S1 Spectral resolution is limited by Doppler width For transition at 843 nm D nD= 0.8 GHz

  12. IS and HFS spectra of Polonium Even isotopes Odd isotopes (low spin)

  13. Latest achievement: At beam - Worlds 1st laser ionized astatine beam was generated in Nov 2010 All measurements had to be made On-Line since there is no stable astatine isotope. 1) Two first step laser wavelengths were measured. Ionization Potential previously unknown 2) The ionization potential was determined by scanning the second laser. At 310 -335 nm 224 nm 216 nm

  14. Replacement of CVL by SSL Advantages: Better beam quality Stability of operation Spectral coverage UV-NIR without gaps Complications: New ionization schemes are needed (Mn, Au) Service by manufacturer only Wavelength tuning range: Fundamental (w) 390 - 850 nm 2nd harmonic (2w) 210 - 425 nm 3rd harmonic (3w) 213 - 265 nm Wavelength tuning range: Fundamental (w) 530 - 850 nm 2nd harmonic (2w) 265 - 425 nm 3rd harmonic (3w) 213 - 265 nm Wavelength tuning range: Fundamental (w) 390 - 850 nm 2nd harmonic (2w) 210 - 425 nm 3rd harmonic (3w) 213 - 265 nm Upgrade of RILIS laser system CVL: 15 years of service for at ISOLDE SSL: installed in 2008

  15. Main green beam Residual green beam New Nd:YAG lasers at ISOLDE RILIS Copper Vapor Lasers are replaced by Diode Pumped Solid State Nd:YAG Lasers • Two lasers are available: • one in use, second as a backup UV beam Laser generates 3 beams at 10 kHz: • Main green beam – 532nm, 60-90 W, 8 ns • Residual green beam – 532 nm, 40-15 W, 9 ns • UV beam - 355 nm, up to 20 W, 11 ns

  16. Replacement of the scheme which uses the CVL green beam. Fortuitous Auto-ionizing transition at CVL wavelength AIS search at LARIS Outcome of RIS study of Mn at LARIS: Many new auto-ionizing states found Various promising Nd:YAG based schemes tested New scheme applied at RILIS Efficiency > 8 % A new RILIS scheme for manganese - LARIS result

  17. Copper vapor lasers retired in 2010

  18. New dye laser installed CREDO dye lasers made by Sirah GmbH installed in Feb/Mar 2010 • Optimized for 10 kHz EdgeWave pump • Accept both 355 and 532 pumping beams • Equipped with FCU (up to 2W of UV)

  19. RILIS ion beams • Ion beams of 30 elements are produced at ISOLDE with RILIS • RILIS web page: http://isolde-project-rilis.web.cern.ch/isolde-project-rilis/intro/principle.html

  20. RILIS operation in 1994-2010 Laser ON time in 2010: • 2096 h – total • 2000 h - on-line Laser time per beam for the operation year 2010

  21. More laser power -> higher ionization efficiency High stability of SSL power -> ion current stability much better Time from cold start of SSL to nominal operation ~ 30 min. No electromagnetic noise to experimental hall from RILIS New ionization scheme of Mn is developed RILIS after CVL-YAG transition • SSL alignment and repair is possible only at EdgeWave • UV power is limited by the optical resistance of harmonics crystals • Efficiency of dye lasers is reduced due to shorter pump pulse • Lifetime of dyes is reduced • Operation of dye lasers and harmonics generators still requires continuous supervision by laser specialists

  22. Next step: addition of Ti:Sapphire lasers • Nd:YAG pumped Ti:Sa system • An additional independent fully solid state RILIS laser system • Reduction of the reliance on laser dyes. • Better coverage of the IR and blue spectral ranges • Dual RILIS system could enable simultaneous RILIS setup and operation. • Pump laser: 2 commercial Nd:YAG, 532 nm, 60 W at 10 kHz • Tunable lasers: 3 single sided Uni-Mainz Ti:Sapphire lasers • - frequency doubling, tripling and quadrupling • - computerized temporal and spectral control, 3 GHz, 30 ns • - specs: 3 - 5 W @ 690-980 nm • 1 W @ 350-470 • 150 mW @ 200 – 315 nm

  23. New lasers for RILIS • Three Ti:sapphire laser units were constructed and tested • (PhD student S.Rothe) • Wavelengths in the near infra-red range 690 - 940 nm are obtained • The Frequency Conversion Unit (FCU) allows generation of wavelengths in the blue and UV range • Installed at the ISOLDE off-line mass separator for testing the Laser Ion Source Trap (LIST) • To be installed at RILIS during the winter shut down Ti:Sapphire laser Frequency Conversion Unit

  24. RILIS Ti:Sa + dye laser system 3, 4 Sirah 2 Ti:Sa Dye laser Ti:Sa 3, 4 Ti:Sa Ti:Sa design Sirah 1 Photonics Photonics Edgewave NB-DL NB-DL Edgewave +Photonics Power Sirah 1 Sirah 1 Edgewave Edgewave Power + chiller Chillers on roof outside Frequency conversion unit (Prototype)

  25. Dye + Ti:Sa range Ti:Sa ionization schemes for Si, Ti, Fe, Ge, Pd, Hf, Pr are available Released Dye scheme tested Ti:Sa and Dye schemes tested from ISOLDE target Ti:Sa scheme tested Feasible Not released

  26. Spiral-2 ? hot cavity ? SPES GSI-LEB ALTO RIKEN ? gas catcher ? ? hot cavity ? ? gas catcher ? ? hot cavity ? RILIS ISOLDE, Geneva hot cavity rep. rate 10 kHz dye laser ORNL Oak Ridge (off-line) hot cavity rep. rate ~10 kHz ti:sa laser TIARA LISOL PNPI Takasaki hot cavity rep. rate 300Hz dye laser Gatchina hot cavity rep. rate ~10 kHz dyelaser Louvain-la-Neuve gas cell rep. rate <200Hz dye laser Resonance laser ion sources worldwide FURIOS Jyväskylä gas cell rep. rate ~10 kHz dye & ti:sa laser TRILIS Vancouver hot cavity rep. rate ~10 kHz ti:sa laser updated from C. Geppert, EMIS, Deauville, 2007

  27. Acknowledgements CERN Geneva, Switzerland Institute of Spectroscopy, Troitsk, Russia University of Mainz Germany Sebastian Rother Klaus Wendt Volker Sebastian Gehrard Huber Jurgen Kluge Viatcheslav Mishin VladilenLetokhov Yuri Koudriavtsev Bruce Marsh Marica Sjödin Mats Lindroos Roberto Losito Jacques Lettry Ulli Köster HelgeRavn Richard Catherall Erik Kugler, …… Petersburg Nuclear Physics Institute, Gatchina, Russia KU Leuven Belgium DimaFedorov Yuri Volkov Pavel Molkanov Anatoly Barzakh Maxim Seliverstov Yuri Koudriavtsev Piet Van Duppen KTH – Royal Institute of Technology Stockholm, Sweden Lars-Erik Berg Olli Launila GöranTranstromer Ulf Sassenberg Funding: Knut and Alice Wallenberg Foundation

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