[PPT] - towards selective RIB production and studies of exotic atoms Iain PowerPoint Presentation

SLIDE 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-Based Particle Sources, Feb. 2013

SLIDE 2

General introduction to RIB production
Probing the gas jet
In-jet laser ionization
Outlook

Outline of talk

I.D. Moore, 1st Topical Workshop on Laser-Based Particle Sources, Feb. 2013

SLIDE 3

General methods of RIB production (I)

I.D. Moore, 1st Topical Workshop on Laser-Based Particle Sources, Feb. 2013

High-energy primary beam Radioactive atoms Low-energy ion beam Mass selection

ISOL method

kV

High yield but difficult for refractory elements, chemically active elements.

Z and T1/2 dependence

Born in 1951, Niels Bohr Institute

ISOL facilities: TRIUMF, GANIL, ALTO, ISOLDE (Wed. talks) SPES (Thurs.)

SLIDE 4

I.D. Moore, 1st Topical Workshop on Laser-Based Particle Sources, Feb. 2013

High-energy primary beam Projectile fragments Isotope selection Medium-energy ion beam

In-flight method

General methods of RIB production (II)

Very fast separation, access to μs half-lives and beams of ALL elements. Often poor beam quality. Precision experiments at low-energy not directly accessible.

First in-flight separator, Oak Ridge (1958)

SLIDE 5

The ion guide / gas catcher method

I.D. Moore, 1st Topical Workshop on Laser-Based Particle Sources, Feb. 2013

…an ISOL system for ALL elements, fast extraction

Projectile source Thin target mass separator Neutralization Laser re-ionization Z selectivity; Laser Ion Guide Ion survival IGISOL Fast beams Purification in-flight electrical fields

``The best of both worlds´´

SLIDE 6

~6 eV

(5-9 eV)

ground state first excited state higher excited states ionization potential

E1

energy

0 eV E0

non-resonant ionization excitation of auto-ionizing states ionization of Rydberg-states extraction field or collisional ionization

Principles of laser ionization

sR ~ 10-12 cm2 sI ~ 10-17 cm2 sI ~ 10-15 cm2

Efficiency × Selectivity N Z

I.D. Moore, 1st Topical Workshop on Laser-Based Particle Sources, Feb. 2013

SLIDE 7

I.D. Moore, 1st Topical Workshop on Laser-Based Particle Sources, Feb. 2013

repetition rate: ~10 kHz
tuning range:
fundamental 700 - 1000 nm
frequency doubled 350 - 500 nm
frequency tripled 240 – 330 nm
frequency quad. 205 - 250 nm
laser linewidth: >5 GHz (broad)

<1 GHz (narrow)

JYFL: a high-repetition rate laser system

Talk by Volker, 11:20

SLIDE 8

I.D. Moore, 1st Topical Workshop on Laser-Based Particle Sources, Feb. 2013

https://www.jyu.fi/fysiikka/en/research/accelerator/igisol

K=30 MeV cyclotron from K=130 MeV cyclotron

IGISOL-4: 2012 -

Off-line ion sources: (discharge, carbon cluster…) Laser transport for optical manipulation Mass spectrometry & post-trap spectroscopy Collinear laser spectroscopy Laser ionization in-source/in-jet Decay spectroscopy IGISOL – second floor

SLIDE 9

Yu. Kudryavtsev et al., NIM B 267 (2009) 2908

In-gas-cell laser ion source

Separation of stopping and laser ionization volume improves:

Laser ionization efficiency at

high cyclotron beam current

Increasing selectivity

(collection of non-neutral ions)

Laser beams Longitudinal

SPIG Ar/He from gas purifier

Ion Collector

Ionization chamber

Beam from Cyclotron Target Exit hole Ø 0.5 – 1 mm Ion collector Laser Ionization chamber Filament

Talk by Yuri,

Thurs. 15:50

I.D. Moore, 1st Topical Workshop on Laser-Based Particle Sources, Feb. 2013

SLIDE 10

General introduction to RIB production
Probing the gas jet
In-jet laser ionization
Outlook

I.D. Moore, 1st Topical Workshop on Laser-Based Particle Sources, Feb. 2013

SLIDE 11

Why do we wish to use the gas jet?

…a quest for PURE radioactive ion beams → (the Laser Ion Source ``Trap´´)

I.D. Moore et al., AIP Conf. Proc. 831 (2006) 511

Hot cavity LIST (talk by S. Richter, Fri. 10:40)

F. Schwellnus et al., Rev. Sci. Instrum. 81 (2010) 02A515

I.D. Moore, 1st Topical Workshop on Laser-Based Particle Sources, Feb. 2013

SLIDE 12

I.D. Moore, 1st Topical Workshop on Laser-Based Particle Sources, Feb. 2013

Improvements in resolution

(300 K) (2000 - 2500 K)

T. Sonoda et al., NIMB 267 (2009) 2918

The effect of temperature and pressure on the FWHM Hot cavity (ISOLDE) Gas cell (LISOL/JYFL)

Doppler broadening Pressure broadening

Laser resolution 1.8 GHz

SLIDE 13

Time overlap between fast atoms and laser pulses

I.D. Moore, 1st Topical Workshop on Laser-Based Particle Sources, Feb. 2013

What challenges do we face?

Velocity distribution laser ion guide (JYFL) 0 m/s Velocity distribution of jet (CFD simulations) Courtesy of J. Kurpeta (Warsaw) 1500 m/s

Gas cell Gas jet He 200 mbar

T. Sonoda et al., NIMB 267 (2009) 2918

Reference cell

7 GHz blue shift

= 1660 m/s jet

T. Kessler, PhD thesis (JYFL)

SLIDE 14

I.D. Moore, 1st Topical Workshop on Laser-Based Particle Sources, Feb. 2013

Solution: a high-repetition rate laser system

SPIG Vdc = +40 V

59Cu (T1/2=81.5 s)

On-line reaction: 58Ni(3He-25 MeV,np)59Cu

R. Ferrer-García, V. Sonnenschein et al., NIM B 291 (2012) 29

In-jet production ~60× < in-gas cell production

SLIDE 15

I.D. Moore, 1st Topical Workshop on Laser-Based Particle Sources, Feb. 2013

NASA Technical Reports Server, Record 59, J.A. Inman et al., (2008)

Planar laser-induced fluorescence

M. Jugroot et al., J. Phys. D 37 (2004) 1289

Numerical investigation of jet flows

Second challenge: laser-atom spatial overlap

Properties of the gas jet depends on nozzle shape and pressure boundaries

SLIDE 16

32 mm ~700 V

Imaging gas jets at JYFL

I.D. Moore, 1st Topical Workshop on Laser-Based Particle Sources, Feb. 2013

perspex SPIG

Create a gas discharge
Photograph the expanding jet
Vary background pressure
Vary nozzle type
Model rf sextupole
Analyse the jets

exit hole converging-diverging de Laval nozzle

SLIDE 17

From image to analysis

I.D. Moore, 1st Topical Workshop on Laser-Based Particle Sources, Feb. 2013

60
40
20

20 40 60 10

2

10

3

10

4

10

5

0.146 mbar 0.226 mbar 0.329 mbar 0.588 mbar 1.180 mbar 2.339 mbar 4.352 mbar 5.640 mbar

Intensity (arbitrary units) Radial position (mm)

1 2 3 4 5 6 7 1 10 100

1.45 mm exit hole, 25 mbar 1.45 mm exit hole, 56 mbar 1.45 mm con-div, 56 mbar 0.6 mm exit hole, 56 mbar

Jet FWHM (mm) Background pressure (mbar)

Variations in background pressure

φspig = 6 mm

~1 mbar is suitable for jet

acceptance into rf device

Not suitable conditions

due to discharge

SLIDE 18

I.D. Moore, 1st Topical Workshop on Laser-Based Particle Sources, Feb. 2013

M. Reponen, I.D. Moore, I. Pohjalainen et al., NIMA 635 (2011) 24

Probing the jet from a de Laval nozzle

PAr = 250 mbar

60 50 40 30 20 10

10
20

40 80 120 160 200 240 Stagnation pressure (mbar) Distance from the nozzle exit (mm)

Flow Direction

PAr = 300 mbar

𝑞𝑗 𝑞𝑗𝑜 = 𝛿 + 1 𝑁2 𝛿 − 1 𝑁2 + 2

𝛿 𝛿−1

𝛿 + 1 2𝛿𝑁2 − 𝛿 + 1

1 𝛿−1

With the Mach number we can also determine:

jet temperature
jet density

𝑊2 = 𝛿 − 1 2 𝑁2 1 + 𝛿 − 1 2 𝑁2

−1

∙ 𝑊

𝑛𝑏𝑦 2

Images and direct pressure measurements

SLIDE 19

General introduction to RIB production
Probing the gas jet
In-jet laser ionization
Outlook

I.D. Moore, 1st Topical Workshop on Laser-Based Particle Sources, Feb. 2013

SLIDE 20

Laser spectroscopy of Ni: gas cell vs. gas jet

231.164 231.166 231.168 231.170 231.172 0.0 0.4 0.8 1.2

Wavelength (nm)

0.0 0.4 0.8 1.2

Normalized count rate (a.u.)

0.0 0.4 0.8 1.2

He 50 mbar Gas cell Gas jet Reference cell ~5 GHz

5 GHz blue Doppler shift; ~1130 m/s jet velocity
Laser linewidth dominant (~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-Based Particle Sources, Feb. 2013

SLIDE 21

A stepwise improvement in laser linewidth

I.D. Moore, 1st Topical Workshop on Laser-Based Particle Sources, Feb. 2013

Thin etalon coated substrate d = 0.3mm R ≈ 40% Birefringent filter Thick etalon undoped YAG d = 6 mm R = 8%

Addition of a second etalon into the Ti:sapphire cavity

(Talk by T. Kron, Thurs. 17:10)

FWHM = 6.6 GHz FWHM = 2.0 GHz

Ref. cell

SLIDE 22

Spectroscopy of 63Cu (LISOL 2011)

R. Ferrer, V. Sonnenschein et al., NIMB 291 (2012) 29

Ion signal (a.u.)

Reference cell Gas cell Gas jet

Vjet ~600 m/s

PAr = 150 mbar

COG

I.D. Moore, 1st Topical Workshop on Laser-Based Particle Sources, Feb. 2013

n – 1227.45887 (THz)

FWHM = 2.9(2)GHz FWHM = 4.3(2)GHz FWHM = 3.2(2)GHz CoG = 2.5(2)GHz

SLIDE 23

First free jet ions in LIST geometry at JYFL (65Cu, Nov. 2012)

100 200 300 400 500 600 700

10000 20000 30000 40000

Count rate [s

1]

Laser intensity [mW cm

2]

1st step

5000 10000 15000 20000

10000 20000 30000 40000 50000 60000

Count rate [s

1]

Laser intensity [mW cm

2]

2nd step

20000
10000

10000 20000

0.0 0.2 0.4 0.6 0.8 1.0

65Cu (LIST)

4.3 GHz FWHM

Arbitrary Frequency (MHz) I.D. Moore, 1st Topical Workshop on Laser-Based Particle Sources, Feb. 2013

Isat = 17 mW/cm2 Isat = 119 mW/cm2

3rd step, Isat ~3.2 W/cm2

SLIDE 24

0,00 0,03 0,06 0,09 0,12 1000 2000 3000 4000

20
10

10 20 100 200 300

Ion signal (arb. u.)

Ref. cell

Gas cell Gas jet (LIST)

n - 915 423.95 (GHz)

I.D. Moore, 1st Topical Workshop on Laser-Based Particle Sources, Feb. 2013 FWHM = 1.8(2) GHz

Following computer control and power stabilization

FWHM = 6.7(3) GHz FWHM = 3.9(2) GHz CoG = -3.2(1) GHz

Vjet ~1040 m/s

0,0 0,5 1,0 0,0 0,5 1,0

15
10
5

5 10 15 0,0 0,5 1,0

Ion signal (arb. u.)

Ref. cell

Gas jet (LIST) Gas jet (crossed)

n - 915 424.0 (GHz)

FWHM = 2.0(1) GHz FWHM = 3.6(2) GHz FWHM = 3.0(2) GHz CoG = -2.5(3) GHz

Vjet ~800 m/s

SLIDE 25

Free jet laser spectroscopy of Cu at LISOL

I.D. Moore, 1st Topical Workshop on Laser-Based Particle Sources, Feb. 2013

Modify front end of separator
Install a 90° bent RFQ
Supersonic free gas jet
Use of narrowband laser for first

excitation step (pulsed amplified CW diode laser)

Spectral bandwidth only 88 MHz

Gas cell 90° bent RFQ L2 L1

Shaped rod segments Towards extraction RFQ

Gas cell chamber Gas cell

Ar 200 mbar Cu filament

Free jet expansion

L2 L1 90° bent RFQ

Extraction RFQ Extraction electrode Towards mass separator

SLIDE 26

Results: gas jet vs. reference cell

I.D. Moore, 1st Topical Workshop on Laser-Based Particle Sources, Feb. 2013

Yu. Kudryavtsev et al., NIMB 297 (2013) 7
Measured HFS of 995(30) MHz

agrees with literature: 1013.2(20) MHz

Doppler shift 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 limiting factor for

high-resolution spectroscopy in the free jet

Improve by using better collimated jets (Laval)

SLIDE 27

Proposed setup for gas jet spectroscopy at RIKEN

I.D. Moore, 1st Topical Workshop on Laser-Based Particle Sources, Feb. 2013

The PArasitic RI-beam production by Laser Ion-Source (PALIS) project

Dye laser pumped by Nd:YAG laser (rep. rate 10 kHz) Optical frequency combs Injection locked Ti:Sapphire laser pumped by Nd:YAG laser (rep. rate 10 kHz)

Ar gas inlet Filament atom source / RI beam

Gas cell (high pressure) MS & ion detection Ionization cell (low pressure) 1st step laser 2nd step laser Counter injection Vertical injection Mirror Mirror Multi-reflection

Gas-jet

free jet or jet through designed nozzle Prototype version: T. Sonoda, M. Wada et al., NIMB 295 (2013) 1

SLIDE 28

Demonstration: Nb spectroscopy using gas jet RIS

I.D. Moore, 1st Topical Workshop on Laser-Based Particle Sources, Feb. 2013

4d45s 0 cm

1

4d35s5p 28278.25 cm

1

Ionization Potential 54513.8 cm

1

6P3/2

6D1/2

353.63 nm A = 4.95×10

7 s

1

6 4 3 5 4 5 11.2 GHz 9.3 GHz

93Nb

30
20
10

10 20 30 0.5 1 Detuning frequency [GHz] Normalized intensity [A.U.] n0=847.758THz

FWHM = 10.4(4) GHz, vacuum = 11.3(1) GHz gas jet

T. Takatsuka, H. Tomita et al, submitted to Hyp. Int. (2013)

SLIDE 29

General introduction to RIB production
Probing the gas jet
In-jet laser ionization
Outlook

I.D. Moore, 1st Topical Workshop on Laser-Based Particle Sources, Feb. 2013

SLIDE 30

T. Kessler et al., Laser Phys. 18 (2008) 842

Nd:YAG pump laser (10kHz) CW Ti:sa input Pulsed narrow bandwidth output to experiments Feedback to locking unit

An injection-locked pulsed Ti:sapphire laser system

I.D. Moore, 1st Topical Workshop on Laser-Based Particle Sources, Feb. 2013

2000
1000

1000 2000 100 200 Detuning frequency (MHz) Detected ions (cps)

Fi→Ff : 3→4

3→3 3→2 2→3 2→2 2→1

Mark 1 (Mainz): ~20 MHz, >1.5 W
Mark 2 (Nagoya, Japan)
Mark 3 (JYFL, Finland)
cw Matisse laser ordered with pump
ring cavity being developed
TEM locking electronics bought

27Al

SLIDE 31

Towards the future…

I.D. Moore, 1st Topical Workshop on Laser-Based Particle Sources, Feb. 2013

In-gas-cell and in-gas-jet laser ionization at S3 facility, SPIRAL-2, GANIL

Continuation of jet studies with laser ionization (nozzles etc)
Spectroscopy of exotic nuclei in the jet with injection-locked lasers

SLIDE 32

Thank you

Mikael Reponen, Volker Sonnenschein, Ilkka Pohjalainen Tobias Kron, Klaus Wendt Yuri Kudryavtsev Hideki Tomita

SLIDE 33

Yu. Kudryavtsev et al., NIM B 267 (2009) 2908

Dual-chamber gas cell commissioning (2012)

Laser beams Longitudinal

SPIG Ar/He from gas purifier

Ion Collector

Ionization chamber

Beam from Cyclotron Target Exit hole Ø 0.5 – 1 mm

17% 11% 2%

M. Reponen, PhD thesis, JYFL (2012)

328.14 328.15 328.16 328.17 328.18 500 1000 1500 2000 2500 3000 3500 4000

107Ag

Counts/sec Wavelength (nm)

36Ar(natZn,pxn)101-97Ag

0.0 0.2 0.4 0.6 0.8 1.0 1.2 1.4 1.6 20 40 60 80 100 120 140

Argon Helium

Selectivity

36Ar beam intensity (pμA)

223Ra α-recoil source

efficiencies

SLIDE 34

FWHM= ~ 3 GHz FWHM= ~ 6 GHz FWHM= ~ 4 GHz He 200 mbar Gas cell Gas jet Reference cell

7 GHz

Laser spectroscopy of Ni: gas cell vs. gas jet

No sensitivity to nuclear structure however 

Gas cell

T. Sonoda et al., NIMB 267 (2009) 2918