International Workshop on Stopping and Manipulation of Ions, Groningen, 28 March 2006 Latest developments at the IGISOL laser ion source Iain Moore University of Jyväskylä Iain Moore University of Jyväskylä

International Workshop on Stopping and Manipulation of Ions, Groningen, 28 March 2006 Mass & decay spectroscopy Collinear laser spectroscopy Ion guide & SPIG (see T. Sonoda talk) RFQ cooler & buncher – optical manipulation (see B. Cheal talk) FURIOS laser cabin The IGISOL Beamline at JYFL

International Workshop on Stopping and Manipulation of Ions, Groningen, 28 March 2006 Why do we need to develop a laser ion source? The IGISOL is both FAST and UNIVERSAL. However there are deficiencies in this technique that arise when working far from stability: UNSELECTIVE Combining the laser ion source with the light ion bombardment of heavy actinide targets (fission) will help to reduce the overwhelming isobaric background. The laser ion source (trap) LIST technique will be used for this purpose (T. Sonoda talk). INEFFICIENT In some cases the IGISOL is not so efficient. In fission, a combination of ~1% stopping and severe recombination of ions due to the intense plasma reduces the efficiency (few ×10 -4 ). In addition, the laser ion source will be combined with the heavy- ion induced fusion evaporation (HIGISOL) work to improve the efficiency (~0.5%).

International Workshop on Stopping and Manipulation of Ions, Groningen, 28 March ms lifetime line JYFLTRAP + Fission ion guide JYFLTRAP + HIGISOL (new ion guide) 80 Y t ½ = 33.8 s  c precision trap 900ms exc. time 101 Y t ½ = 448 ms Switchyard pulsing 100 ms, 1-2 ions/bunch  c precision trap 400ms exc. time

International Workshop on Stopping and Manipulation of Ions, Groningen, 28 March 2006 Principles of resonance laser ionization for exotic nuclei target cyclotron beam laser gas cell RF-ion guide to mass separator Ar - He gas cell LISOL- Louvain-la-Neuve Mainz (trans-U spectroscopy) Y. Kudryavtsev,- NIM B179 (2001) 412 M. Facina,- NIM B226 (2004) 401 M. Sewtz,- PRL 90 (2003) Efficient (> 10 %) Fast (element dependent) Selective: (laser >> 10 6 ) Universal λ2λ2 λ1λ1 λ2λ2 λ a.i. λ1λ1 ~ P.V. Duppen, ENAM 2004 talk

International Workshop on Stopping and Manipulation of Ions, Groningen, 28 March 2006 Ti:Sapphire lasers Nd:YAG 100W, 11 kHz Pulsed dye lasers Copper vapour laser 45W, 10kHz cw dye laser cw pump laser Isotope separator Ion guide Fast Universal Resonant laser IOn Source, FURIOS

International Workshop on Stopping and Manipulation of Ions, Groningen, 28 March 2006 First laser ionization study - yttrium Off-line studies in an atomic beam unit.

International Workshop on Stopping and Manipulation of Ions, Groningen, 28 March 2006 Typical AI state resonance Typical bound state resonance Three sharp resonances found from 2 different atomic levels but at exactly the same wavelength! These correspond to the dye laser driving second step transitions. The chosen scheme for the ion guide work therefore involves both Ti:Sapphire and dye laser second step transitions – more efficient than using the discovered AI states.

International Workshop on Stopping and Manipulation of Ions, Groningen, 28 March 2006 A laser ion guide for heavy-ion fusion evaporation reactions

International Workshop on Stopping and Manipulation of Ions, Groningen, 28 March 2006 First on-line HIGISOL run November 2005 nat Ni target - 3.7mg/cm 2, Y target – 3.5mg/cm 2, 165 MeV 32 S 7+ beam (35 enA) He pressure 40 mbar. Ions detected on MCP plates. Y filament, 6.4mg/cm 2, 2.8 mm at thinnest point Beam ionization Yttrium filament Y+Y+ Laser Exit hole Y + + e - Y Laser Y + O 2 YO +O Y + + O 2 YO + + O Beam Y + + O Beam Y + + e - Y Laser YO + + e- YO UNWANTED CONTAMINANTS! Y+Y+

International Workshop on Stopping and Manipulation of Ions, Groningen, 28 March 2006 Impurities – yttrium reacting with oxygen  exit = 1.0mm, t evac of whole chamber ~600ms, t evac of neutralization channel ~250  s dn/dt = -kn[M] where [M] is impurity concentration, k = 4.1× cm 3 /s for this reaction  = 1/k[M], for 40 mbar He τ ~2.2ms, for 200 mbar He τ ~460  s. 250  s 2.2ms 250  s 460  s

International Workshop on Stopping and Manipulation of Ions, Groningen, 28 March 2006 YO Without the plasma the ratio of Y + to Y0 + is equal. Evacuation times of small channel simulated to be ~10µs, hence yttrium can survive without reacting with impurities. Y+Y+ With plasma, no laser effect seen on YO +

International Workshop on Stopping and Manipulation of Ions, Groningen, 28 March 2006 Elastic scattering/sputtering from target with 32 S 7+ beam Fitted decay time ~450 ms Simulation of flow of created sputtered ions Simulated decay time ~650 ms From elastic scattering ~0.5% recoils stopped in 40mbar He. Sputtering process yields ~0.1%, yet these recoils are stopped only 1mm from the target, therefore the extraction time is long and most are lost to the walls through diffusion. NO LASER EFFECT SEEN

International Workshop on Stopping and Manipulation of Ions, Groningen, 28 March 2006 Immediate future (on-line and off-line) 1.Later this week we have an on-line run to compare the Leuven laser ion guide with the HIGISOL laser ion guide. Yttrium filament, combined with yttrium from an α beam impinging on an yttrium target. (Collaboration with Leuven/Mainz – Yuri/Klaus to attend) 2. Later in the summer we will combine the new MIVOC technique used by the cyclotron to produce an yttrium beam which will be used to make a direct efficiency measurement. The immediate goal is to improve the present HIGISOL efficiency of ~0.5% - then we can reach exotic nuclei such as the N=Z nucleus 78 Y.

International Workshop on Stopping and Manipulation of Ions, Groningen, 28 March A new off-line rig enables continuous development work to be done. This rig allows us to simulate the IGISOL conditions yet is far cleaner. At present a new cold baffle is being installed between the roots pump and the gas cell. In addition a QMA system will allow us to study impurities AFTER the gas has flowed through the ion guide – and how the filament produced yttrium laser ion current is affected. 4. A comparison is to be made between a 50 Hz repetition rate Nd:YAG pumped dye laser system and that of a 11 kHz CVL pumped system. Bismuth is the element of choice, with a two step dye laser scheme to a known autoionizing state. The laser ion current will be measured under identical conditions to see if there is anything more fundamental happening than the expected yield increase with a higher repetition rate laser system.

International Workshop on Stopping and Manipulation of Ions, Groningen, 28 March 2006 Thanks to the following people involved in the laser ion source project: T. Kessler, K. Peräjärvi, T. Sonoda, B. Tordoff, P. Karvonen, S. Rinta-Antila, P. Ronkanen and J. Äystö and to: The IGISOL group, Manchester University and the University of Mainz Financial support: Centre of Excellence Programme / Academy of Finland, Marie Curie Foundation (EC), NIPNET RTD project. THANKS FOR YOUR ATTENTION!

International Workshop on Stopping and Manipulation of Ions, Groningen, 28 March 2006 Second on-line HIGISOL run December 2006 Beta gated gamma spectrum nat Ni( 32 S 7+, 5p3n ) 82 Y 32 S MeV 40 enA on target With 300 mbar He, 82 Y yield = 1.8 ions/s/pnA M. Oinonen et al., NIMA 416 (1998) Y yield ~2 ions/s/pnA 3 rd HIGISOL run (December) Mass measurements made on: Nb, Y and Zr using the new ion guide with an efficiency ~0.5%. Beta efficiency ~57% Gamma eff. ~1.9% NO LASER EFFECT SEEN