Post on 18-Dec-2015
First Experiments with theLaser Ion Source and Trap (LIST)
Daniel Fink
15th EN-STI Students’ Coffee, CERN
EN Department, CERN, Geneva and University of Heidelberg
Daniel Fink - EN-STI Students' Coffee - CERN24/1/2013
Daniel Fink - EN-STI Students' Coffee - CERN
Content
1. ISOLDE: CERN’s playground for modern alchemists
2. Motivation: reduction of isobaric contamination
3. Introduction to resonance ionization laser ion source (RILIS)
4. Principle of the laser ion source and trap (LIST)
5. LIST on-line run 2011
6. LIST on-line run 2012
7. Summary
24/1/2013
Daniel Fink - EN-STI Students' Coffee - CERN
ISOLDE: CERN’s Playground for Modern Alchemists?P
N
Alchemist, England 1576
24/1/2013
Gold
Lead
7982
Daniel Fink - EN-STI Students' Coffee - CERN
ISOLDE: CERN’s Playground for Modern Alchemists?
Asymmetric fission, etc.
Size and shape of exotic nuclei
Nucleosynthesis in the universe
+ Laser spectroscopy
+ Biophysics
+ Solid state physics
… and much more
New nuclear reactions
Halo nucleus 11B
24/1/2013
Supernovae, neutron stars, …
Nuclear medicine
PET, α-therapy, etc.
N
P
Daniel Fink - EN-STI Students' Coffee - CERN
Extraction/Ionization
Effusion
Ionization
Isotope Separation
Q/A
Post acceleration or to Experiment
ISOLTRAP
The Isotope Separator On-Line (ISOL) Process
24/1/2013
Production
MINIBALL
Daniel Fink - EN-STI Students' Coffee - CERN
The ISOLDE Target Unit
24/1/2013
1.4 GeV Protons
1.4 GeV Protons
Transfer line and
ion source
Target Ion source
Ions
Daniel Fink - EN-STI Students' Coffee - CERN
New hall extension
Control room
Separator magnets
Radioactive laboratory
Experimental hall
1.4 GeVprotons
Target area
RILIS
The ISOLDE Laboratory
24/1/2013
Daniel Fink - EN-STI Students' Coffee - CERN24/1/2013
Motivation: Reduction of Isobaric Contamination
78Ni0.2 s
78Cu0.34 s
78Zn1.5 s
78Ga5.5 s
78Ge88 m
78As1.5 h
78Se78Se
N=50
Z=28
1
102
104
srelative
Fission of U with 1 Gev protons
10-2
Q/A
Example: isobaric contamination in a 78Ni ion beam:
Daniel Fink - EN-STI Students' Coffee - CERN24/1/2013
Motivation: Reduction of Isobaric Contamination
• Nonselective surface ionization in hot cavity• Strong isobaric contamination might harm or prevent experiments
Resonance Ionization Laser Ion Source (RILIS)
A panoramic view of the RILIS laser setup:
Resonant laser photons on atoms + Stepwise excitation of e-
Very efficient and element selective ionization!
Element unique RILIS schemes: Principle of RILIS:
E0
E1
E2
Rydbergstate
AIS
IP
Daniel Fink - EN-STI Students' Coffee - CERN24/1/2013
Daniel Fink - EN-STI Students' Coffee - CERN24/1/2013
RILIS Dye Laser System GPS/HRS
Target & Ion Source
RILIS Ti:Sa Laser System
pA – meter
Faraday cup…
SHG/THG/FHG
l – meter
Ti:Sa 2
Dye 2 SHG
Narrowband Dye
THGDye 1
Ti:Sa 1
Ti:Sa 3 (narrowband)
Nd:YAG 2
Nd:YAG 1
LabVIEW based DAQ
Scheme of RILIS at ISOLDE
Isobaric contamination in RILIS beams
• Nonselective surface ionization in hot cavity• Strong isobaric contamination might harm or prevent experiments
Daniel Fink - EN-STI Students' Coffee - CERN24/1/2013
Daniel Fink - EN-STI Students' Coffee - CERN
Isobaric contamination in RILIS beams
24/1/2013
• Strong increase of ions of interest• Higher selectivity but isobaric contaminants remain in beam
Daniel Fink - EN-STI Students' Coffee - CERN
Isobaric contamination in RILIS beams
24/1/2013
• Deflection of surface ions by electrostatic deflection• Increased energy spread of laser ions due to high extraction field gradient• Ineffective mass separation and poor transport efficiency
high field gradient
Daniel Fink - EN-STI Students' Coffee - CERN
Principle of Laser Ion Source and Trap (LIST)
24/1/2013
• Deflection of surface ions by electrostatic deflection• High selectivity due to laser ionization outside hot cavity• Transverse rf-trapping field guides ions towards extraction region
Daniel Fink - EN-STI Students' Coffee - CERN
LIST Target Assembly
Necassary target modifications:
• Radiation hard components
• Stable support
• Automatic rf-connector
• Stable line- and target holder
• Transducer box
24/1/2013
LIST device: LIST target unit:
1 cm
Proposal: K. Blaum et al., NIMB 204 (2003) 331
protons
Daniel Fink - EN-STI Students' Coffee - CERN
LIST Setup at ISOLDERILIS cabin High voltage cage
Target areaISOLDE hall
Nd:YAG Dye 1
1. 285 nm (UV)
3. 532 nm
SHG
60 keV
2. 552 nm
Repeller voltage
Rf-generator
+
++
Detectors: tape station, Faraday cup, MCP, Windmill
Separator magnet
Remote control
GPS
+
+
20m
Glass fiber
24/1/2013
Dye 2
Mg RILIS setup
Daniel Fink - EN-STI Students' Coffee - CERN
LIST Run 2011: Proof of Principle
24/1/2013
Effective suppression of surface ions but with lower laser ionization efficiency.
0
1. Suppression of stable surface ions: 2. Reliability and robustness:
3. Suppression of radioactive ions: 4. Laser ionization of radiactive ions:
Suppression:> 3000
Daniel Fink - EN-STI Students' Coffee - CERN24/1/2013
LIST On-Line Run 2012: First Physics
Goals of second LIST on-line run:
• Test of improved LIST design for higher efficiency
• Proof of principle with strongly outgassing UCx-target
• Provide highly purified beams of Mg and Po
• First real on-line applications of LIST at ISOLDE
RILIS schemes for Mg and Po:
Annular Si Si216Pobeam
C-foils20 mg/cm2
α detector (Windmill, Leuven):UCx-target:
repeller
heat shield
source
rf - rods endcap
atoms
laser
Improved LIST:
Daniel Fink - EN-STI Students' Coffee - CERN24/1/2013
LIST Performance 2012: Efficiency and SuppressionScans of repeller voltage for different masses with β-detector:
• Overall suppression:
3 orders of magnitude
But limits for certain isotopes
Supp
ress
ion
fact
or• Ion Guide vs. LIST:
30Mg: 0208Po: 0
( 2011: 0 )
Daniel Fink - EN-STI Students' Coffee - CERN
Motivation: Laser Spectroscopy on Polonium
24/1/2013
T. E. Cocolios & M.E. Seliverstov 2008
Two measurement campaigns in 2007 and 2009 at ISOLDE/CERN
• Several Po-isotopes remained unstudied due to strong Fr-contamination
• Using LIST to suppress Fr contamination in 2012
Mean square radii of Po-isotopes among other elements:
Po invisible due to Fr contamination:
Daniel Fink - EN-STI Students' Coffee - CERN24/1/2013
Polonium Spectroscopy: HFS and IS • New Po-decay data on mass 219
Direct measurement of IS of 216Po and 217Po
Prelim
inary
• 216Po and 217Po in one measurement
Laser frequency offset, GHz
Daniel Fink - EN-STI Students' Coffee - CERN24/1/2013
Summary
• LIST suppresses isobaric contaminants and improves selectivity of RILIS
• Proof of principle by 2011 on-line run:
o Suppression of > 1000
o Ionization efficiency reduction by ≈50x (Mg)
• First real physics application in 2012:
o Suppression of > 1000, but limited by in-trap decay for certain isotopes
o Ionization efficiency reduction by ≈20x (Mg,Po)
o Laser spectroscopy of 217,219Po possible due to suppression of Fr by LIST
LIST is now an established ion source option for ISOLDE users
Ongoing characterization and improvement of LIST for physics in 2014. But …
Daniel Fink - EN-STI Students' Coffee - CERN
...and special thanks to the collaborators:
Klaus Blaum, Richard Catherall, Thomas E. Cocolios Bernard Crepieux, Valentine Fedosseev, Alexander Gottberg, Nobuaki Imai,
Tobias Kron, Matthias Kronberger, Bruce Marsh, Christoph Mattolat, Michael Moore, Sebastian Raeder, Sven Richter, Ralf Rossel,
Sebastian Rothe, Maxim Seliverstov, Pekka Suominen, Marica Sjodin, Thierry Stora, Klaus Wendt, ...
… and the whole IS456 collaboration
Acknowledgements
24/1/2013
Daniel Fink - EN-STI Students' Coffee - CERN
LIST Run 2011: First On-Line Test
24/1/2013
Goals of LIST-run 2011:
1. Proof of principle using Mg beams
2. Characterizing LIST with radioactive isotopes
3. Test of reliability and robustness
4. Compare on-line- to off-line performance
Mg scheme: