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Iain Moore JYFL, Finland

Gas jet laser ionization: developments towards selective RIB production and studies of exotic atoms. Iain Moore JYFL, Finland. I.D. Moore, 1st Topical Workshop on Laser-Based Particle Sources , Feb . 2013. Outline of talk. General introduction to RIB production

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Iain Moore JYFL, Finland

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  1. Gas jet laser ionization: developments towards selective RIB production and studies of exotic atoms Iain Moore JYFL, Finland I.D. Moore, 1st Topical Workshop on Laser-BasedParticleSources, Feb. 2013

  2. Outline of talk • General introduction to RIB production • Probing the gas jet • In-jet laser ionization • Outlook I.D. Moore, 1st Topical Workshop on Laser-BasedParticleSources, Feb. 2013

  3. General methods of RIB production (I) ISOL method High-energy primary beam Born in 1951, NielsBohr Institute Radioactive atoms Low-energy ion beam kV Highyieldbutdifficult for refractory elements, chemicallyactiveelements. Mass selection Z and T1/2dependence ISOL facilities: TRIUMF, GANIL, ALTO, ISOLDE (Wed. talks) SPES (Thurs.) I.D. Moore, 1st Topical Workshop on Laser-BasedParticleSources, Feb. 2013

  4. General methods of RIB production (II) In-flightmethod High-energy primary beam Firstin-flightseparator, OakRidge (1958) Projectile fragments Isotope selection Medium-energy ion beam Veryfastseparation, access to μs half-lives andbeams of ALL elements. Oftenpoorbeamquality. Precisionexperiments at low-energynot directlyaccessible. I.D. Moore, 1st Topical Workshop on Laser-BasedParticleSources, Feb. 2013

  5. The ionguide / gascatchermethod …an ISOL system for ALL elements, fastextraction ``The best of bothworlds´´ Projectilesource Fastbeams Purificationin-flight Thintarget Neutralization Ionsurvival electricalfields massseparator Laser re-ionization Z selectivity; Laser Ion Guide IGISOL I.D. Moore, 1st Topical Workshop on Laser-BasedParticleSources, Feb. 2013

  6. non-resonant ionization excitation of auto-ionizing states ionization of Rydberg-states extraction field or collisional ionization ionization potential higherexcitedstates firstexcitedstate E1 energy groundstate 0 eV E0 Principles of laser ionization ~6 eV (5-9 eV) sI ~ 10-17 cm2 sI ~ 10-15 cm2 sR ~ 10-12 cm2 Z Efficiency× Selectivity N I.D. Moore, 1st Topical Workshop on Laser-BasedParticleSources, Feb. 2013

  7. JYFL: a high-repetition rate laser system • repetition rate:~10 kHz • tuning range: • - fundamental 700 - 1000 nm - frequency doubled350 - 500 nm • - frequency tripled 240 – 330 nm • - frequency quad. 205 - 250 nm • laser linewidth:>5 GHz (broad) • <1 GHz (narrow) TalkbyVolker, 11:20 I.D. Moore, 1st Topical Workshop on Laser-BasedParticleSources, Feb. 2013

  8. from K=130 MeV cyclotron IGISOL-4: 2012 - https://www.jyu.fi/fysiikka/en/research/accelerator/igisol Off-lineionsources: (discharge, carboncluster…) K=30 MeV cyclotron Laser transport foroptical manipulation Laser ionizationin-source/in-jet Collinear laser spectroscopy Decayspectroscopy Massspectrometry & post-trapspectroscopy IGISOL – secondfloor I.D. Moore, 1st Topical Workshop on Laser-BasedParticleSources, Feb. 2013

  9. In-gas-cell laser ion source Ar/He from gas purifier Laser beams Longitudinal • Separation of stopping and laser ionization volume improves: • Laser ionization efficiency at high cyclotron beam current • Increasing selectivity (collection of non-neutral ions) Beam from Cyclotron Target Laser Ionization chamber Ionization chamber Ion Collector Ion collector Filament Exit hole Ø 0.5 – 1 mm TalkbyYuri, Thurs. 15:50 SPIG Yu. Kudryavtsev et al., NIM B 267 (2009) 2908 I.D. Moore, 1st Topical Workshop on Laser-BasedParticleSources, Feb. 2013

  10. General introduction to RIB production • Probing the gas jet • In-jet laser ionization • Outlook I.D. Moore, 1st Topical Workshop on Laser-BasedParticleSources, Feb. 2013

  11. Why do we wish to use the gas jet? …a quest for PUREradioactiveionbeams → (the Laser IonSource ``Trap´´) I.D. Moore et al., AIP Conf. Proc. 831 (2006) 511 Hot cavity LIST (talkby S. Richter, Fri. 10:40) F. Schwellnus et al., Rev. Sci. Instrum. 81 (2010) 02A515 I.D. Moore, 1st Topical Workshop on Laser-BasedParticleSources, Feb. 2013

  12. Improvements in resolution The effect of temperature and pressure on the FWHM Hot cavity (ISOLDE) Dopplerbroadening (2000 - 2500 K) Pressurebroadening Gascell (LISOL/JYFL) (300 K) Laser resolution 1.8 GHz T. Sonoda et al., NIMB 267(2009) 2918 I.D. Moore, 1st Topical Workshop on Laser-BasedParticleSources, Feb. 2013

  13. What challenges do we face? • Time overlapbetweenfastatoms and laser pulses Velocitydistribution laser ionguide (JYFL) Reference cell T. Kessler, PhDthesis (JYFL) Velocitydistribution of jet (CFD simulations) He 200 mbar Gas cell 0 m/s 1500 m/s Courtesy of J. Kurpeta (Warsaw) 7 GHzblueshift = 1660 m/s jet Gas jet T. Sonoda et al., NIMB 267(2009) 2918 I.D. Moore, 1st Topical Workshop on Laser-BasedParticleSources, Feb. 2013

  14. Solution: a high-repetition rate laser system SPIG Vdc = +40 V 59Cu (T1/2=81.5 s) On-linereaction: 58Ni(3He-25 MeV,np)59Cu In-jetproduction~60× < in-gascellproduction R. Ferrer-García, V. Sonnenschein et al., NIM B 291 (2012) 29 I.D. Moore, 1st Topical Workshop on Laser-BasedParticleSources, Feb. 2013

  15. Second challenge: laser-atom spatial overlap Properties of the gas jet depends on nozzleshape and pressureboundaries Planarlaser-inducedfluorescence Numericalinvestigation of jet flows NASA Technical Reports Server, Record 59, J.A. Inman et al., (2008) M. Jugroot et al., J. Phys. D 37 (2004) 1289 I.D. Moore, 1st Topical Workshop on Laser-BasedParticleSources, Feb. 2013

  16. 32 mm Imaging gas jets at JYFL • Create a gasdischarge • Photograph the expanding jet • Vary backgroundpressure • Vary nozzletype • Modelrfsextupole • Analyse the jets ~700 V converging-diverging exithole perspex SPIG de Lavalnozzle I.D. Moore, 1st Topical Workshop on Laser-BasedParticleSources, Feb. 2013

  17. From image to analysis Variations in backgroundpressure • ~1 mbar is suitable for jet • acceptance into rfdevice • Notsuitableconditions • dueto discharge φspig = 6 mm I.D. Moore, 1st Topical Workshop on Laser-BasedParticleSources, Feb. 2013

  18. Probing the jet from a de Laval nozzle Images and directpressuremeasurements PAr = 250 mbar PAr = 300 mbar • With the Machnumberwecanalsodetermine: • jet temperature • jet density M. Reponen, I.D. Moore, I. Pohjalainen et al., NIMA 635 (2011) 24 I.D. Moore, 1st Topical Workshop on Laser-BasedParticleSources, Feb. 2013

  19. General introduction to RIB production • Probing the gas jet • In-jet laser ionization • Outlook I.D. Moore, 1st Topical Workshop on Laser-BasedParticleSources, Feb. 2013

  20. Laser spectroscopy of Ni: gas cell vs. gas jet Reference cell Gas cell He 50 mbar ~5 GHz Gas jet • 5 GHzblueDopplershift;~1130 m/s jet velocity • Laser linewidthdominant (~9 GHz at 232 nm) M. Reponen, I.D. Moore et al., EPJ A 48 (2012) 45 I.D. Moore, 1st Topical Workshop on Laser-BasedParticleSources, Feb. 2013

  21. A stepwise improvement in laser linewidth • Addition of a secondetalon into the Ti:sapphirecavity Thick etalon undoped YAG d = 6 mm R = 8% Thin etalon coated substrate d = 0.3mm R ≈ 40% Birefringent filter Ref. cell FWHM = 6.6 GHz FWHM = 2.0 GHz (Talkby T. Kron, Thurs. 17:10) I.D. Moore, 1st Topical Workshop on Laser-BasedParticleSources, Feb. 2013

  22. LARISSA Spectroscopy of 63Cu (LISOL 2011) Reference cell COG FWHM = 2.9(2)GHz Ionsignal (a.u.) PAr= 150 mbar Gas cell FWHM = 4.3(2)GHz Gas jet FWHM = 3.2(2)GHz CoG = 2.5(2)GHz n – 1227.45887 (THz) Vjet ~600 m/s R. Ferrer, V. Sonnenschein et al., NIMB 291 (2012) 29 I.D. Moore, 1st Topical Workshop on Laser-BasedParticleSources, Feb. 2013

  23. First free jet ions in LIST geometry at JYFL (65Cu, Nov. 2012) 2nd step 1st step Isat = 17 mW/cm2 Isat = 119 mW/cm2 3rd step, Isat~3.2 W/cm2 I.D. Moore, 1st Topical Workshop on Laser-BasedParticleSources, Feb. 2013

  24. Following computer control and power stabilization FWHM = 2.0(1) GHz FWHM = 1.8(2) GHz FWHM = 3.6(2) GHz Vjet ~800 m/s FWHM = 6.7(3) GHz CoG = -2.5(3) GHz FWHM = 3.0(2) GHz Vjet ~1040 m/s FWHM = 3.9(2) GHz CoG = -3.2(1) GHz I.D. Moore, 1st Topical Workshop on Laser-BasedParticleSources, Feb. 2013

  25. Free jet laser spectroscopy of Cu at LISOL Towardsextraction RFQ • Modifyfrontend of separator • Install a 90° bent RFQ • Supersonicfreegas jet • Use of narrowband laser for first • excitationstep (pulsedamplified • CW diode laser) • Spectralbandwidthonly 88 MHz 90° bent RFQ Gascell L1 L2 Shapedrodsegments Gascellchamber 90° bent RFQ Extraction electrode Gascell Extraction RFQ Ar 200 mbar L1 Towardsmass separator L2 Cufilament Free jet expansion I.D. Moore, 1st Topical Workshop on Laser-BasedParticleSources, Feb. 2013

  26. Results: gas jet vs. referencecell • Measured HFS of 995(30) MHz • agrees with literature: • 1013.2(20) MHz • Dopplershift of 1830(30) MHz; • gas jet velocity of 599(10) m/s • FWHM = 450 MHz (gas jet) • = 300 MHz (ref. cell) • The gas jet divergence is the limitingfactor for • high-resolutionspectroscopy in the free jet • Improvebyusingbettercollimatedjets (Laval) Yu. Kudryavtsev et al., NIMB 297 (2013) 7 I.D. Moore, 1st Topical Workshop on Laser-BasedParticleSources, Feb. 2013

  27. Proposedsetup for gas jet spectroscopy at RIKEN Vertical injection The PArasiticRI-beamproductionbyLaser Ion-Source (PALIS) project Mirror Gas-jet Counter injection Dye laser pumped by Nd:YAG laser (rep. rate 10 kHz) free jet or jet through designed nozzle 2nd step laser Multi-reflection Mirror Ar gas inlet 1st step laser Injection locked Ti:Sapphire laser pumped by Nd:YAG laser (rep. rate 10 kHz) MS & ion detection Filament atom source / RI beam Optical frequency combs Gas cell (high pressure) Ionization cell (low pressure) Prototype version: T. Sonoda, M. Wada et al., NIMB 295 (2013) 1 I.D. Moore, 1st Topical Workshop on Laser-BasedParticleSources, Feb. 2013

  28. Demonstration: Nbspectroscopyusinggas jet RIS FWHM = 10.4(4) GHz, vacuum = 11.3(1) GHzgas jet 93Nb T. Takatsuka, H. Tomita et al, submitted to Hyp. Int. (2013) I.D. Moore, 1st Topical Workshop on Laser-BasedParticleSources, Feb. 2013

  29. General introduction to RIB production • Probing the gas jet • In-jet laser ionization • Outlook I.D. Moore, 1st Topical Workshop on Laser-BasedParticleSources, Feb. 2013

  30. An injection-locked pulsed Ti:sapphire laser system • Mark 1 (Mainz): ~20 MHz, >1.5 W • Mark 2 (Nagoya, Japan) • Mark 3 (JYFL, Finland) • - cwMatisse laser ordered with pump • - ringcavitybeingdeveloped • - TEM lockingelectronicsbought 27Al Pulsednarrow bandwidth output toexperiments CWTi:sa input Feedback to lockingunit Nd:YAG pump laser (10kHz) T. Kessler et al., Laser Phys. 18 (2008) 842 I.D. Moore, 1st Topical Workshop on Laser-BasedParticleSources, Feb. 2013

  31. Towards the future… • Continuation of jet studies with laser ionization (nozzlesetc) • Spectroscopy of exoticnuclei in the jet with injection-lockedlasers In-gas-cell and in-gas-jet laser ionization at S3facility, SPIRAL-2, GANIL I.D. Moore, 1st Topical Workshop on Laser-BasedParticleSources, Feb. 2013

  32. Mikael Reponen, VolkerSonnenschein, Ilkka Pohjalainen Tobias Kron, Klaus Wendt YuriKudryavtsev HidekiTomita Thankyou

  33. Dual-chamber gas cell commissioning (2012) 36Ar(natZn,pxn)101-97Ag Ar/He from gas purifier Laser beams Longitudinal Beam from Cyclotron Target Ionization chamber 11% 2% Ion Collector 17% Exit hole Ø 0.5 – 1 mm 223Ra α-recoilsource efficiencies SPIG M. Reponen, PhDthesis, JYFL (2012) 36Ar beamintensity (pμA) Yu. Kudryavtsev et al., NIM B 267 (2009) 2908

  34. Reference cell FWHM= ~ 3 GHz He 200 mbar Gas cell FWHM= ~ 6 GHz Gas jet FWHM= ~ 4 GHz Laser spectroscopy of Ni: gas cell vs. gas jet T. Sonodaet al., NIMB 267(2009) 2918 Gas cell 7 GHz No sensitivity to nuclear structurehowever

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