In-gas-cell and in-gas-jet laser ion sources at LISOL

Transcription

Laser
LISOL
Source
In-gas-cell and in-gas-jet laser ion sources at LISOL
Yuri Kudryavtsev
Instituut voor Kern- en Stralingsfysika, KU Leuven,
Celestijnenlaan 200 D, B-3001 Leuven, Belgium.
Yu. Kudryavtsev, SMI-13, Jyväskylä, June 11-13, 2013
Overview
1. In-Gas-Cell Laser Ionization
LISOL laser ion source
Laser system
Radioactive Ion Beams (RIB) for nuclear spectroscopy
2. In-Gas-Cell Laser Spectroscopy
Dual-chamber laser ion source
Laser spectroscopy of 57-59Cu, 97-101Ag,
3. In-Gas-Jet Laser Spectroscopy
What spectral resolution can be achieved?
Off-line high resolution laser spectroscopy in a free jet. Experiment
4. New developments
HELIOS project
S3 & GANIL
5. Conclusions
IGLIS - In Gas Laser Ionization and Spectroscopy
LISOL (since 1992)
SPIG
RF ion guide
gas
Gas cell
P0 T0 ρ0
500mbar
Ions towards
mass separator
+
target
accelerator
beam
laser beams
λ1, λ2
Thing target
1 mg/cm2
Autoionizing state
IP
λ2
λ1
Ground state
Q – conductance of the exit orifice, d=0.5 mm, Ar, 35 cm3/s
V – irradiated volume, 1 cm3
Laser pulse repetition rate – Q/V= 35 Hz (saturation, no recombination)
Gas purity !
- Refractory elements
- Isotopes with a short lifetime
- Pre separation, after in-flight mass separator
IGISOL / Jyväskylä - Volker Sonnenschein
PALIS / RIKEN
- Michiharu Wada
KISS / KEK
- Yoshikazu Hirayama
GSI
- Mustapha Laatiaoui
Dubna/JINR
- Sergey Zemlyanoy
S3 / GANIL
Louvain-la-Neuve Radioactive Beam Facility
CYCLONE 110
LISOL
Leuven Isotope Separator On-Line
Detection
LASER ION
SOURCE
Laser System (since 1994)
Excimer laser 2
LPX240, 200Hz,
15ns, 100 mJ
Dye Laser 2
SHG
Synchron.
Unit
Telescope
Excimer laser 1
LPX240, 200Hz,
15ns, 100 mJ
λ2
Telescope
Dye Laser 1
Energy meters
λ1
SHG
TOF
Energy (eV)
Autoionizing state
Laser Ion Source of the
LISOL mass separator
Reference
Cell
4
Tunable range
205 - 900 nm
0
15 m
SEM
Laser System
XeCl Excimer
lasers
Dye lasers
SHG
Reference cell
Yu.Kudryavtsev,
SMI06, March 27-28,
2006
Towards LIS, 15m
Two-step laser ionization schemes
Tunable range
205 - 900 nm
80% of all elements can in principle be ionized by the LISOL laser system
LISOL Laser Ion Source
Towards mass
separator
Energy (eV)
Gas cell for fusionevaporation reactions
SPIG
–210V
Target (~ mg/cm2)
4
Exit hole
Cyclotron
beam
Ar 500mbar
Ar/He
from gas
purifier
Filament
Laser
beams
200Hz
0
Ion source selectivity - Laser ON/OFF:
30-80 for proton-induced fission reactions
100-200 for fusion evaporation reactions
57Co
112Rh
- Eff. 6%
- Eff. 3.8%, 252Cf fission source
Pulsed operation mode
Cyclotron
on
off
off
on
Laser
Separator
on
Plasma created in the cell does not
allow to collect not neutralized ions
and causes partial recombination of
laser-produced ions
Front end of the LISOL mass separator
Cyclotron beam
Extraction
electrode
SPIG
Gas Cell
Gas from purifier
LISOL Radioactive Ion Beams (since 1992)
Heavy Ion-induced fusion
evaporation reactions:
Ac
Heavy Ion-induced fusion
Rh,Ru,Sn,In,Ag
Light Ion-induced fusion
Co,Ni,Mn,Cr,V,Cu
Proton-induced fission of 238U:
Spontaneous fission of 252Cf:
Rh,Ru,Mo,Pd
Proton-induced fission of
Fe,Co,Ni,Cu
238U:
Dual-Chamber Gas Cell Laser Ion Source
Ar, He from
gas purifier
Accelerator
beam
Stopping
chamber
Target
+
+
“Shadow” effect – laser
ionization region and ion
collector are not visible from
the cyclotron bam pass
+
500 mbar
CW operation of cyclotron
and separator
Reaction products
Ion
collector
Laser beams
λ1 λ 2
Ionization
chamber
+
+
Ion Collector
Yu. Kudryavtsev et al., NIM B 267 (2009) 2908–2917
Laser
ionization
chamber
+
+
Exit orifice
Stopping chamber – 4 cm in diameter
Laser ionization chamber – 1 cm in diameter
SPIG
+
Exit orifice diameter – 0.5 mm/1mm
Towards mass
separator
Fusion evaporation reactions:
Yield-LaserON
Selectivity = Yield-LaserOFF > 2200
Dual Chamber Laser Ion Source
SPIG
Prism
Cyclotron
beam
Laser selectivity in heavy-ion induced fusion evaporation reaction
94Rh
40Ar
+
58Ni
→ 98Pd* → Rh/Ru + xp yn
94Rh
94Rh
40Ar
beam
265 MeV
+
+
Laser beam
+
+
+
+
Selectivity - 450
Ion
collector
Ionization
chamber
+
Selectivity > 2200
In-Gas-Cell Laser Spectroscopy of 57,59Cu
Cu+ + e-
65Cu
Autoionizing State
First Ionization Limit
62317.4 cm-1
λ2 = 441.6 nm
1
4P0
40943.73
4
1/2
cm-1
3
2
3
4
F=2
F=1
λ1 = 244.164 nm
2S
1/2
µ ( Cu ) =
Ahf ( ACu )
63
Ahf ( Cu )
58Ni(p,
59Cu
F=2
F=1
CuI: ground state
A
63Cu
µ ( 63Cu )
T. Cocolios et al., PRL 103, 102501 (2009);
Phys. Rev. C 81, 014314 (2010)
57Cu:
6 ions/s
2n)57Cu (T1/2=199 ms)
Frequency [GHz]
In-gas-cell laser spectroscopy of 57,59Cu: total statistics
57Cu
and 63Cu & 59Cu and 65Cu were measured simultaneously – no systematic error
Measurement number
Results
57Cu
199 ms
55Ni 56Ni 57Ni 58
Ni
209 ms
6.0 d
T. E. Cocolios et al., PRL103 (2009) 102501
T. E. Cocolios et al., PRC81 (2010) 014314
36 h
55Co
17 h
54Co
Magnetic moment of 57Cu isotopes using the β-NMR technique
K. Minamisono et al., PRL 96 (2006) 102501
In source laser spectroscopy at ISOLDE down to 58,59Cu
N.J. Stone et al., PRC 77 (2008) 014315
Collinear laser spectroscopy at ISOLDE on 58-62Cu
P. Vingerhoets et al., PLB 703 (2011) 34
Laser spectroscopy of 97-101Ag
• Production
92Mo(14N – 130 MeV,2pxn)104−xAg
64,natZn(36Ar– 125 MeV,pxn)101−97Ag
101
Ag(9/2+)
1250
750
250
Laser ionization efficiency ~ 2%
101
Ag(1/2-)
1250
750
250
Counts (arb. u.)
• In-gas cell laser spectroscopy
520 mbar argon
Total width: 9-10 GHz • Isomeric beam
99
Ag(9/2+)
1000
800
600
400
99
Ag(1/2-)
105
55
5
97
Ag(9/2+)
600
500
• Detection
Beta- and gamma detection
400
-40
R. Ferrer et al., to be published
-20
0
20
Freq- CoG (GHz)
40
In-Gas-Cell Laser Spectroscopy of 57,59Cu
Cu+ + e-
65Cu
Autoionizing State
First Ionization Limit
62317.4 cm-1
λ2 = 441.6 nm
4P0
40943.73
Doppler broadening, T=300 K
Pressure broad. (P = 140 mbar, Ar)
Laser bandwidth – 1.6 GHz
1/2
63Cu
3.5 GHz
F=2
F=1
cm-1
λ1 = 244.164 nm
2S
1/2
F=2
F=1
CuI: ground state
µ ( Cu ) =
A
Ahf ( ACu )
63
Ahf ( Cu )
58Ni(p,
59Cu
µ ( 63Cu )
T. Cocolios et al.PRL 103, 102501 (2009);
Phys. Rev. C 81, 014314 (2010)
57Cu:
6 ions/s
2n)57Cu (T1/2=199 ms)
Frequency [GHz]
In-gas-jet laser spectroscopy
at LISOL, LIST mode
Reference cell
Ni
FWHM= ~ 2 GHz
Laser band width ~1.6 GHz, (excimer-pumped dye lasers,
second harmonic) perpendicular to the atomic beam
Ar 500 mbar
Gas cell
FWHM=6.5 GHz
Red shift of 2.5 GHz:
pressure dependence
Gas Jet
Doppler shift due to jet
velocity: ~560 m/s
Gas
Cell
FWHM= ~ 2 GHz
43089.2
43089.6
43090.0
Wavenumber [cm-1]
T. Sonoda et al., NIM B267 (2009) 2908
Resonance Laser Ionization in Supersonic Gas Jets
Crossed laser beams with a supersonic jet
NO laser ionization inside the cell !
Laser ionization only in the cold jet !
De Laval nozzle
gas
Gas cell
λ2 !
u
λ1
Po To ρo
flaser ≥ 1/ ( L / u )
≥ 10 kHz, argon jet - L = 5.5 cm
u – stream velocity, 550m/s
λ2
laser beam
expander
Autoionizing state
λ2
bent RFQ
L
IP
ν2= ν02
The parallel beam from de Laval nozzle !
No broadening due to the beam divergence
Very careful design of the nozzle is required
λ1 ν 1 = ν 01 × (1 − u / c)
Free jet
gas
Ground state
Po To ρo
zone of
silence
λ1
target
accelerator
beam
λ2
Doppler and Collision Contributions to the Spectral Line Width
RF ion guide
SPIG
λ1, λ2
Gas cell
gas
Po To ρo
target
accelerator
beam
laser beams
λ1, λ2
4s2S1/2 – 4p2P1/2, 327.4 nm 63Cu transition, ν0= 30535.3 cm-1
Gas jet
5000
4500
Linewidth, MHz
γ coll
γ coll × ρ
Hot cavity
63Cu
Collision/pressure contribution 4000
∆ν
=
coll
Gas cell
3500
- collision broadening
coefficient, 1.5·10-20 cm-1/cm-3
(8 MHz/mbar)
ρ – gas density (atom /cm3)
P=300 mbar
3000
2500
P=100 mbar
2000
{
1500
1000
Doppler contribution
500
0
1
3.3 MHz
10
200 MHz
100
Temperature, K
1000
10000
Properties of supersonic beams
y
x
z
One dimensional Maxwell-Boltzmann velocity distribution
Po To ρo
PTρ
 -mvi 2 
m
F (vi) =
exp 

2π kT 0
 2kT0 
th
 -m(vz-u)2 
m
F (vz) =
exp 

2π kT
2kT


ss
Radioactive atoms are in thermal
equilibrium with buffer gas atoms
Velocity distribution
0,030
0,025
0,020
M=25
63Cu
0,015
Fss(vi)
0,010
M=7
Fth(vi)
0,005
T=300K
M=1
0,000
-500 -400 -300 -200 -100 0
100 200 300 400 500 600 700 800
Velocity vz, m/s
δ ( F ) = 2 ln 2
2kT
m
- Full Width at Half Maximum (FWHM)
Doppler Gaussian and collision- and natural
Lorentzian contributions to the spectral line shape
Lorentzian
collision
300 K
500 mbar
G (ν )


2
2
 c (ν −ν o ) 
G0 exp  −

2 2 kT


ν0
m


1
Γ
L (ν −ν 0 ) =
2π (ν −ν 0 + Γsh )2 + ( Γ 2 )2
Laser bandwidth – δlaser Gaussian if
laser time profile is Gaussian
δ laser = 441/ τ pulse
τpulse = 5 ns δlaser =88 MHz
Gaussian
Doppler
Laser
-5000 -4000 -3000 -2000 -1000
0
1000 2000 3000 4000 5000
300K
100 mbar
Jet M=12
T=6 K
ρ=0.003ρ0
Laser
collision
Doppler
-500 -400 -300 -200 -100
0
100
Frequency, MHz
200
300
400
500
λ2
laser beam
Free jet
Two-Step Laser Ionization
in a Free Jet
1951 free jet – A. Kantrowitz, J. Grey
Pbg
zone of
silence
Po To ρo
Diameter of orifice d
λ1 laser beam
Mach disk, T, ρ ↑
Zt
ZM
ZM – position of the Mach disk
ZM
P0
= 0.67
d
Pbg
z
Mt - terminal Mach number
Zt – position of terminal Mach number
Mt = 3.32 ( P 0 d )
(mbar, mm)
0.4
1.5
Zt  Mt 
=

d  3.26 
Mach disk
Visualization of free jet
High T, P
M.Belan, S.De Ponte , D.Tordella, Exp. Fluids 45(2008)501-511
Properties of Free Jet
Centerline Mach number calculation
A
B
C1
C2
C3
C4
3.337 -1.541 3.232 -0.7563 0.3937 -0.0729
ρ
Po To ρo
z
coll
Γ=
γ coll × ρ
→ 3.3 MHz Mach=12
1
3
25
0,1
20
0,01
Mach number
atom density, ρ/ρ0
−2
Z
Z
M=
1.0 + A   + B  
d
d


(γ −1) 

C3
C2
C4 
Z
Z

M  
C +
+
+
> 0.5 =
 1  Z   Z  2  Z 3 
d
d
 


 d   d   d  

Z
0 < < 1.0
d
0,001
0,0001
0
5
10
15
Distance from orifice, z/d
20
15
10
5
0
0
5
10
15
Distance from orifice, z/d
20
Doppler Broadening in the Free Jet Supersonic Beam
λ2
λ1
Po To ρo
4s2S1/2 – 4p2P1/2, 327.4 nm 63Cu transition, ν0= 30535.3 cm-1
Doppler broadening, MHz
1.600
1000
Temperature, K
100
10
1
1.400
2 ln 2
∆ν Doppler =
1.200
ν0
1.000
800
c
2kT
m
Total broadening
600
400
200
Contribution due to beam divergence
0
0
5
10
15
20
Mach number
0,1
0
10
20
Mach number
30
∆ axDoppler = ν 0 ⋅ u (1 − cos θ ) / c - axial laser beam direction
T=6K, Doppler FWHM =200 MHz
Total broadening = 420 MHz
Amplification of CW Single Mode Diode Laser
Radiation in a Pulsed Dye Amplifier
Two-stages dye amplifier
Tunable single mode 654.98 nm
Amp. I
Amp. II
SHG
327.49 nm
CW diode laser
KDP
Output pulse energy, uJ
Excimer
XeCl Laser
5ns → 88 MHz
300
250
200
150
5ns
100
50
0
0
50
Towards gas
Jet & Atomic
Beam Unit
100
150
CW input laser power, mW
200
Resonance Ionization Spectroscopy in a Free Gas Jet (Experiment I)
Gas cell chamber
3d94s5s 2D3/2
Autoionizing state
65260.1 cm-1
63Cu
62317.4 cm-1
IP
I
λ2=287.9 nm
3d104p 2P1/2
30535.3 cm-1
λ1=327.395 nm
3d104s 2S1/2
Ground state
a
Extraction chamber
900 bended RFQ
Extraction
RFQ
Gas cell
P0=200
mbar
Extraction
electrode
Towards mass
separator
L1L1
Ar
F’
2
1
L2
Cu filament
Free jet
expansion
Towards
extraction RFQ
b
2
1
1E-4 mbar
0.1 mbar
900 bent segmented RFQ
Gas cell
L1
L2
Resonance Ionization Spectroscopy in a Free Gas Jet (Experiment II)
u=
{
kT 0γ M
mng 1 + ( γ − 1) 2  M 2
}
1830 MHz → T0 =355±3K
3d94s5s 2D3/2
+
Po To ρo
λ1
62317.4 cm-1
IP
30535.3 cm-1
λ1=327.395 nm
3d104s 2S1/2
Ground state
a
b
2
1
63Cu
0,8
Ion signal (arb. u.)
3d104p 2P1/2
1830 MHz
1,0
F’
2
1
+ +
Crucible
T=1250K
I
λ2=287.9 nm
Detector
Laser
beams
λ2
Autoionizing state
65260.1 cm-1
63Cu
Atomic
beam
2
0,6
0,4
Gas Jet b
450 MHz
300 MHz
a
a
0,2
0,0
30535,40
Atomic beam
b
30535,45
30535,50
a
65Cu
30535,55
Wavenumber (cm-1)
30535,60
Comparison of laser ionization spectroscopy in a gas cell and in a gas Jet
gas cell
3d94s5s 2D3/2
63Cu
Po To ρo
Autoionizing state
65260.1 cm-1
62317.4 cm-1
λ1
IP
I
λ1
λ2=287.9 nm
3d104p 2P1/2
30535.3 cm-1
F’
2
1
1,0
λ1=327.395 nm
a
cd
Ground state
b
2
1
Intensity (arb. u.)
0,8
3d104s 2S1/2
gas jet
0,6
0,4
In gas cell
In gas jet
P0=500 mbar
T0=300K
8 MHz/mbar
cd
a
0,2
b
0,0
-10
-5
0
5
10
First
First step
step
laser
frequency, GHz
GHz
Freq.laser
- CoGfrequency,
(GHz)
15
In-gas-cell and in-gas-jet laser RIS setup
for HELIOS and S3 projects
grant has been granted for HELIOS project
(Heavy Elements Laser IOnization and Spectroscopy)
New laser laboratory will be set up at KU Leuven
Gas cell chamber
Gas Cell
de Laval nozzle
S-shaped RFQ
IGLIS at S3 GANIL
S3 - Super Separator Spectrometer
Collaboration GANIL, IPN, CSNSM
Differential
pumping
chamber
Extraction
chamber
Towards
mass
separator
Ion collector
Gas jet
gas
Extraction
RFQ
Extraction
1·10-5-2·10 -3
mbar
< 1e-5 mbar
from in-flight
separator
electrode
One-dimension laser
beam expander
Thing
entrance
window
Position of the
stopped nuclei
λ1 λ2
In-gas-cell
ionization
λ2
λ1
In-gas-jet
ionization
1·10-2
-2 mbar
IGLIS laboratory at KU Leuven, HELIOS project
Separator room
Laser room
Clean room: ISO 100 000
ΔT=±0.5oC
HV platform
24 m2
Laser
power
supplies
Yu. Kudryavtsev,
May 30-31,
2013
Yu.Orsay,
Kudryavtsev,
SMI-13,
Jyväskylä, June 11-13, 2013
24 m2
IGLIS laboratory at KU Leuven, HELIOS project
laser room
dipole magnet
measuring
station
einzel lens
beam diagnostics
front-end vacuum chamber
pumping system
Laser equipment for IGLIS experiments @ HELIOS &S3
Two step laser ionization spectroscopy in the gas cell
• Two high-repetition-high-power Nd:YAG pump Laser
- Max. average power: 90 W (@ 532 nm) or 36 W (@ 355 nm)
- Max. repetition rate: 15 kHz
• Two high repetition rate dye lasers
- Tunable wavelength from 215 to 900 nm
- Linewidth: 0.06 cm-1 (1.8 GHz) – 0.25 cm-1 (7.5 GHz)
Pump Laser
Dye Laser
For high resolution spectroscopy in the gas jet first step
will consist of
• A continuous wave (CW) single mode tunable diode laser
- Linewidth: 0.1 MHz -> 60 MHz (pulsed)
- mode-hop-free tuning range: 20-30 GHz
• A dye amplifier with second harmonic generator
Diode Laser
Developments for S3 at SPIRAL2
LINAC: 14.5 A MeV HI, A/q=3 HI source Up to 1mA
Beam dump
& Movable
fingers
High power
Rotating targets
including actinides
Gas cell
Large
acceptance
Multipoles
S3 transmission: 50% (5 charge states), Beam spot – 3*5 cm2
58Ni(40Ca,p3n)94Ag:
few 10 pps amongst them the 21+ isomer 390 ms
208Pb(48Ca,2n)254No: about 1 pps
Detection
room
Laser
room
Pauline Ascher – Wednesday – 10:15
Workshop
“S3-Low Energy Branch”
Orsay, May 30 – May 31, 2013
Efficiency of the “Horn” Gas Cell (I)
The dual chamber approach remains
Gas flow
S3 beam
Calculations have done by Evgeny Mogilevskiy (Comsol)
width
Width – 40 mm, 20 mm
Exit orifice diameter d= 0.5 mm, 1 mm
Pressure (Ar) – 100, 300, 500 mbar
Evacuation time, ms
P=500 mbar, d=1 mm
40
Exit orifice
Efficiency, %
30
85
600
Gas-cell based laser ionization and spectroscopy: worldwide
With pre-Separator
Without pre-Separator
MARA JYFL
IGISOL-4 JYFL
DUBNA
LISOL LLN
SHIP GSI
ANL
S3 GANIL
LBL
TEXAS A&M
?
PALIS RIKEN
KISS RIKEN
Workshop on “Gas-Cell-Based Laser Ionization Spectroscopy”
Leuven, May 30 – June 1, 2012
RIKEN-Wako, December 10 -11, 2012
Dedicated website & newsletters
Sunchan Jeong
http://kekrnb.kek.jp/iglis-net/
Active from the beginning of June
Summary
1. Resonance laser ionization in a gas cell can be used for efficient
production of exotic isotopes to perform nuclear spectroscopy and
in-gas-cell laser spectroscopy
2. The novel approach based on the crossed laser beams with a
supersonic gas jet has been proposed and realized in a free jet at
off-line conditions.
3. Using this method, the spectral resolution can be improved by
more than one order of magnitude (200 MHz, Δν/ν =2.3E-7) in
comparison to the gas cell ionization.

In-gas-cell and in-gas-jet laser ion sources at LISOL

Transcription

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