Скачать презентацию Latest developments at the IGISOL laser ion source Скачать презентацию Latest developments at the IGISOL laser ion source

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

The IGISOL Beamline at JYFL FURIOS laser cabin Collinear laser spectroscopy Mass & decay The IGISOL Beamline at JYFL FURIOS laser cabin Collinear laser spectroscopy Mass & decay spectroscopy Ion guide & SPIG (see T. Sonoda talk) RFQ cooler & buncher – optical manipulation (see B. Cheal talk) 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 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: INEFFICIENT 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). 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 heavyion induced fusion evaporation (HIGISOL) work to improve the efficiency (~0. 5%). International Workshop on Stopping and Manipulation of Ions, Groningen, 28 March 2006

80 Y t½ = 33. 8 s wc precision trap 900 ms exc. time 80 Y t½ = 33. 8 s wc precision trap 900 ms exc. time JYFLTRAP + HIGISOL (new ion guide) 101 Y t½ = 448 ms Switchyard pulsing 100 ms, 1 -2 ions/bunch wc precision trap 400 ms exc. time 100 ms lifetime line JYFLTRAP + Fission guide International Workshop on Stopping and Manipulation of Ions, Groningen, 28 March 2006

Principles of resonance laser ionization for exotic nuclei λa. i. ~ λ 2 laser Principles of resonance laser ionization for exotic nuclei λa. i. ~ λ 2 laser • gas cell LISOL- Louvain-la-Neuve Mainz (trans-U spectroscopy) Ar - λ 2 gas cell He cyclotron beam target RF-ion guide λ 1 P. V. Duppen, ENAM 2004 talk to mass separator Y. Kudryavtsev, - NIM B 179 (2001) 412 M. Facina, - NIM B 226 (2004) 401 M. Sewtz, - PRL 90 (2003) 163002 • Efficient (> 10 %) • Fast (element dependent) • Selective: 100 -1000 (laser >> 106) International Workshop on Stopping and Manipulation of Ions, Groningen, 28 March 2006 • Universal

Fast Universal Resonant laser IOn Source, FURIOS Ion guide Isotope separator Pulsed dye lasers Fast Universal Resonant laser IOn Source, FURIOS Ion guide Isotope separator Pulsed dye lasers Copper vapour laser 45 W, 10 k. Hz Ti: Sapphire lasers Nd: YAG 100 W, 11 k. Hz cw dye laser cw pump laser 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 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 Three sharp resonances found from 2 different atomic levels but Typical AI 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. Typical bound state resonance 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 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 Y filament, 6. 4 mg/cm 2, 2. 8 First on-line HIGISOL run November 2005 Y filament, 6. 4 mg/cm 2, 2. 8 mm at thinnest point nat. Ni target - 3. 7 mg/cm 2, Y target – 3. 5 mg/cm 2, 165 Me. V 32 S 7+ beam (35 en. A) He pressure 40 mbar. Ions detected on MCP plates. Yttrium filament Y + O 2 0. 54 YO +O Beam Y+ + O 2 Y+ Laser Beam ionization Y+ YO+ + O Y+ + e - Beam 0. 25 Y Y+ + O Y+ + e - 0. 12 YO+ + e- YO Laser Y Laser UNWANTED CONTAMINANTS! Exit hole International Workshop on Stopping and Manipulation of Ions, Groningen, 28 March 2006

Impurities – yttrium reacting with oxygen 250 ms 2. 2 ms 460 ms Fexit Impurities – yttrium reacting with oxygen 250 ms 2. 2 ms 460 ms Fexit = 1. 0 mm, tevac of whole chamber ~600 ms, tevac of neutralization channel ~250 ms dn/dt = -kn[M] where [M] is impurity concentration, k = 4. 1× 10 -10 cm 3/s for this reaction t = 1/k[M], for 40 mbar He τ ~2. 2 ms, for 200 mbar He τ ~460 ms. International Workshop on Stopping and Manipulation of Ions, Groningen, 28 March 2006

4. 5 YO+ With plasma, no laser effect seen on YO+ 0. 06 Without 4. 5 YO+ With plasma, no laser effect seen on YO+ 0. 06 Without the plasma the ratio of Y+ to Y 0+ is equal. 0. 63 Y+ 0. 3 Evacuation times of small channel simulated to be ~10µs, hence yttrium can survive without reacting with impurities. 0. 07 International Workshop on Stopping and Manipulation of Ions, Groningen, 28 March 2006

Elastic scattering/sputtering from target with 32 S 7+ beam Simulation of flow of created Elastic scattering/sputtering from target with 32 S 7+ beam Simulation of flow of created sputtered ions Fitted decay time ~450 ms Simulated decay time ~650 ms From elastic scattering ~0. 5% recoils stopped in 40 mbar He. Sputtering process yields ~0. 1%, yet these recoils are stopped only 1 mm 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 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 2. 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 2006

3. A new off-line rig enables continuous development work to be done. This rig 3. 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 k. Hz 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, 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 Beta efficiency ~57% Gamma Second on-line HIGISOL run December 2006 Beta gated gamma spectrum Beta efficiency ~57% Gamma eff. ~1. 9% nat. Ni(32 S 7+, 5 p 3 n )82 Y 32 S 7+ 165 Me. V 40 en. A on target With 300 mbar He, 82 Y yield = 1. 8 ions/s/pn. A NO LASER EFFECT SEEN M. Oinonen et al. , NIMA 416 (1998) 485 82 Y yield ~2 ions/s/pn. A 3 rd HIGISOL run (December) Mass measurements made on: 85 -88 Nb, 79 -83 Y and 83 -88 Zr using the new ion guide with an efficiency ~0. 5%. International Workshop on Stopping and Manipulation of Ions, Groningen, 28 March 2006