international workshop on stopping and manipulation of ions, groningen, 28 march 2006 latest...

International Workshop on Stopping and Manipulation of Ions, Groningen, 28 March 2006International Workshop on Stopping and Manipulation of Ions, Groningen, 28 March 2006

Latest developments at the IGISOL laser ion source

Latest developments at the IGISOL laser ion source

Iain MooreUniversity of Jyväskylä

Iain MooreUniversity of Jyväskylä


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 JYFLThe IGISOL Beamline at JYFL


Why do we need to develop a laser ion source?Why do we need to develop a laser ion source?

The IGISOL is both FAST and UNIVERSAL. However there aredeficiencies in this technique that arise when working far from stability:

UNSELECTIVE

Combining the laser ion sourcewith the light ion bombardment ofheavy actinide targets (fission)will help to reduce the overwhelmingisobaric background.

The laser ion source (trap) LISTtechnique will be used for thispurpose (T. Sonoda talk).

INEFFICIENT

In some cases the IGISOL isnot so efficient. In fission, acombination of ~1% stoppingand severe recombination ofions due to the intense plasmareduces the efficiency (few ×10-4).

In addition, the laser ion sourcewill be combined with the heavy-ion induced fusion evaporation(HIGISOL) work to improve theefficiency (~0.5%).

International Workshop on Stopping and Manipulation of Ions, Groningen, 28 March 2006International Workshop on Stopping and Manipulation of Ions, Groningen, 28 March 2006100 ms lifetime line

JYFLTRAP +Fission ion guide

JYFLTRAP +HIGISOL (new ion guide)

80Y t½ = 33.8 sc precision trap 900ms exc. time

101Y t½ = 448 ms

Switchyard pulsing100 ms, 1-2 ions/bunch

c precision trap 400ms exc. time


Principles of resonance laser ionization for exotic nucleiPrinciples of resonance laser ionization for exotic nuclei

target

cyclotron beam

laser

gas cell

RF-ion guide

to mass separator

Ar - He

• gas cellLISOL- Louvain-la-NeuveMainz (trans-U spectroscopy)

Y. Kudryavtsev,- NIM B179 (2001) 412M. Facina,- NIM B226 (2004) 401 M. Sewtz,- PRL 90 (2003) 163002

• Efficient (> 10 %)• Fast (element dependent)• Selective: 100-1000 (laser >> 106)• Universal

λ2

λ1

λ2

λa.i.

λ1

~

P.V. Duppen, ENAM 2004 talk


Ti:Sapphire lasers

Nd:YAG100W, 11 kHz

Pulsed dye lasers

Copper vapour laser 45W, 10kHz

cw dye laser

cw pump laser

Isotope separatorIon guide

Fast Universal Resonant laser IOn Source, FURIOSFast Universal Resonant laser IOn Source, FURIOS


First laser ionization study - yttriumFirst laser ionization study - yttrium

Off-line studies in an atomic beam unit.


Typical AI state resonance

Typical bound state resonance

Three sharp resonances found from 2 different atomiclevels but at exactly the same wavelength! Thesecorrespond to the dye laser driving second steptransitions.

The chosen scheme for the ion guide worktherefore involves both Ti:Sapphire and dye lasersecond step transitions – more efficient than using thediscovered AI states.


A laser ion guide for heavy-ion fusion evaporation reactionsA laser ion guide for heavy-ion fusion evaporation reactions


First on-line HIGISOL run November 2005First on-line HIGISOL run November 2005

natNi target - 3.7mg/cm2, Y target – 3.5mg/cm2, 165 MeV 32S7+ beam (35 enA)

He pressure 40 mbar. Ions detected on MCP plates.

Y filament, 6.4mg/cm2, 2.8 mm at thinnest point

Cyclotron 3s on 3s off, 10 cycles Y

Laser on Laser off

Co

un

ts p

er

bin

an

d c

yc

le

Time (ms)

0.54

0.25

0.12

Beam ionization

Yttrium filament

Y+

Laser

Exit hole

Y+ + e- Y

Laser

Y + O2 YO +O

Y+ + O2 YO+ + O

Beam

Y+ + O

Beam

Y+ + e- Y

LaserYO+ + e- YO

UNWANTED CONTAMINANTS!

Y+


Impurities – yttrium reacting with oxygenImpurities – yttrium reacting with oxygen

exit = 1.0mm, tevac of whole chamber ~600ms, tevac of neutralization channel ~250s

dn/dt = -kn[M] where [M] is impurity concentration, k = 4.1×10-10 cm3/s for this reaction

= 1/k[M], for 40 mbar He τ ~2.2ms, for 200 mbar He τ ~460s.

250s

2.2ms

250s

460s


0 2000 4000

0.0

1.5

3.0

4.5

Cyclotron 1s on 5s off 20 cycles, laser on 2-3 sC

ou

nts

pe

r b

in a

nd

cy

cle

Time (ms)

YO+4.5

0.06

0 1000 2000 3000 40000.0

0.2

0.4

0.6

0.8

Cyclotron 1s on 5s off 20 cycles Y

Laser on 2-3 s Laser on 0.25-1 s

Co

un

ts p

er

bin

an

d c

yc

le

Time (ms)

0.63

0.3

0.07

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+

With plasma, no laser effectseen on YO+


0 500 1000 1500 2000 2500 3000 3500 4000 45000,0

0,2

0,4

0,6

0,8

1,0

1,2

1,4

1,6

Co

un

ts p

er b

in

Time (ms)

Elastic scattering/sputtering from target with 32S7+ beamElastic scattering/sputtering from target with 32S7+ beam

Fitted decay time ~450 ms

Simulation of flow of created sputtered ions

0 1 2 3 4 50

5

10

15

20

25

30

Co

un

ts /

0.0

5s

Time (s)

Simulated decay time ~650 ms

From elastic scattering ~0.5% recoils stopped in 40mbar He.Sputtering process yields ~0.1%, yet these recoils are stoppedonly 1mm from the target, therefore the extraction time is longand most are lost to the walls through diffusion.

NO LASER EFFECT SEEN


Immediate future (on-line and off-line)Immediate future (on-line and off-line)

1. Later this week we have an on-line run to compare the Leuven laser ion guide withthe HIGISOL laser ion guide. Yttrium filament, combined with yttrium froman 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 78Y.


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 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.


Thanks to the following people involved in the laserion 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 Universityand the University of Mainz

Financial support:

Centre of Excellence Programme / Academy of Finland,Marie Curie Foundation (EC), NIPNET RTD project.

THANKS FOR YOUR ATTENTION!


Second on-line HIGISOL run December 2006Second on-line HIGISOL run December 2006

Beta gated gamma spectrum natNi(32S7+, 5p3n )82Y32S7+ 165 MeV40 enA on target

With 300 mbar He, 82Y yield = 1.8 ions/s/pnA

M. Oinonen et al.,NIMA 416 (1998) 48582Y yield ~2 ions/s/pnA

3rd HIGISOL run (December)Mass measurements made on:85-88Nb, 79-83Y and 83-88Zrusing the new ion guide withan efficiency ~0.5%.

Beta efficiency ~57%Gamma eff. ~1.9%

NO LASER EFFECT SEEN

international workshop on stopping and manipulation of ions, groningen, 28 march 2006 latest...

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