January 30, 2007 CERN Resonant laser ion sources By V. Fedosseev

January 30, 2007 CERN Laser Ion Sources for On-Line Mass Separators Applied at : IRIS, St. Petersburg Institute of Nuclear Physics, Gatchina, Russia, present time GSI, Darmstadt, Germany, 1993 ISOLDE, CERN, Switzerland, present time ISAC, TRIUMF, Canada, 2004 – present time ORNL, USA, 2004 – present time Hot Cavity Laser Ion Source Buffer Gas Cell Laser Ion Source Produced RIB: Ho, Yb, Tm, Eu, Gd Produced RIB: Sn Produced RIB: Yb, Ag, Ni, Mn, Zn, Be, Cu, Cd, Sn, Al, In, Ga, Mg, Pb, Tl, Bi, Tb, Sb, Po Applied at : LISOL, Leuven, Belgium, present time IGISOL, Jyväskylä, Finland, 2006 – present time Produced RIB: Ni, Rh, Co, Cu, Ti, Ru, Mn, Fe Produced RIB: Ga, Al Off-line tests Produced RIB: Y

January 30, 2007 CERN The Ion Sources Electron impact ionization Surface ionization Resonance Laser ionization

January 30, 2007 CERN Hot Cavity Laser Ion Source Efficiency: L2L2 3  2dv ionrep ionrep   P PP EffusionIonisation   Extraction Electrode Hot Target T=2300K D.C. 60kV +  laser = 2% - 30% Selectivity = Laser Ionization Efficiency Surface Ionization Efficiency => depends on the ionization potentials of isobar atoms  surface = 0.1% -2% - In, Ga, Ba, lanthanides < 0.1% - others > 5% - alkalies

January 30, 2007 CERN Extraction of Ions From the Hot Cavity Plasma potential 0+U pp + (Richardson equation) Thermo electron emission 2 eV Typical values of U for L=30 mm, d=3 mm, t=1 mm W V Nb - 2 V, 4 V (t=0.5mm) TaC - 3 V Lower  Higher plasma potential Lower temperature Better extraction Lower thermal ionization Higher efficiency Higher selectivity

January 30, 2007 CERN The Ion Sources - Efficiency and Suitability RILIS efficiency is scalable with laser power and laser pulse rate

January 30, 2007 CERN Application of different ion sources at ISOLDE

January 30, 2007 CERN Annual running time of RILIS at ISOLDE

January 30, 2007 CERN Isomer Selectivity with RILIS m / g = 20 g / m = nm nm 68 Cu 68gCu 68mCu ~13 GHz Separation of the 3  -decaying isomers in 70 Cu (6 - ) (3 - ) (1 + ) (3 - ) (1 + ) K. Blaum, PRL vol. 92 (2004) 11 Recently applied for an experiment at REX / MINIBALL, Post accelerated isomer beams - world first!

January 30, 2007 CERN Recent RILIS development: Polonium Po 6s 2 6p 4 3 P 2 Ground state 6p 3 7p 6p 3 8p 6p 3 7s 5 S 2 6p 3 7s 3 S nm CVL nm nm nm Ei=8.42 eV nm nm Schemes tested online using the alpha spectroscopy setup used for the in-source RIS studies Efficiency estimated to be comparable to that of The Mk5 plasma ion source Possibility of in-source RIS down to 192 Po!

January 30, 2007 CERN Development of a new laser system for RILIS Replacement of CVL by SSL Advantages:  Better beam quality  Stability of operation  Spectral coverage UV-NIR without gaps Questions:  New ionization schemes  Reliability  Service

January 30, 2007 CERN Requirements to Solid State Lasers Beam A nm High quality beam for ionization Beam B – 532 nm Medium quality beam for dye laser pumping Beam C – 355 nm Medium quality beam for dye laser pumping Pulse repetition rate 8-15 kHz Pulse duration ns10-20 ns Output pulse timing jitter < 3 ns Average power 40 W30-40 W15-20 W Power stability +/- 5% over 24 hours Beam divergence or M 2 < 0.1 mrad after expanding to 20 mm diameter M 2 = 5-20M 2 = Beam pointing stability < 0.02 mrad after expanding to 20 mm diameter

January 30, 2007 CERN RILIS at high ion current  Quenching of laser excitation  Ion confinement in the high charge density environment  Ion extraction  Non-resonant laser ionization Plasma potential is reduced if the electron emission is not sufficient – materials with low work function may help Could be expected if the vacuum is really bad ( >1 mbar ) General problem, not specific for RILIS Negligible for atoms, but may appear for molecules At ISOLDE RILIS: no efficiency reduction up to 100 nA

January 30, 2007 CERN Conclusion  Element-Selective ( + isomer selectivity)  Efficient – some %, scalable to >50%  Applicable for ~80% of elements  All complicated parts are far away from the target RILIS is attractive because it is Effects of the high current operation are to be studied !