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Radioactive Ion Beam (RIB) Production at ISOLDEby the Laser Ion Source and Trap (LIST)
Sven Richter for the LIST-, RILIS- and ISOLDE IS456 Collaborations
222nd of February 2013 | LA³NET Laser Based Particle Sources 2013 | Sven Richter | [email protected]
Content
− Upgrade of the ISOLDE RILIS towardsfull suppression of isobaric contaminations
− Standard operation of the ISOLDE RILIS− Principle of the Laser Ion Source and Trap
− LIST offline & LIST online run 2011− LIST online run 2012
• Motivation:
• Experimental Setup:
• Results:
• Summary
322nd of February 2013 | LA³NET Laser Based Particle Sources 2013 | Sven Richter | [email protected]
Motivation: Reduction of Isobaric Contamination
Protons1,4 GeV
NuclearReactionTarget
Hot cavity atomizer Laser beamsMass-marker
Extraction
• Nickel-78 ion beam: Example of isobaric contamination
• Cross-section production of different isotopes in a UCx target with 1.4 GeV protons
422nd of February 2013 | LA³NET Laser Based Particle Sources 2013 | Sven Richter | [email protected]
Scheme of RILIS at ISOLDE
Slide: D. Fink
Panoramic view of the RILIS laser setup:
Very efficient and element selective ionization!
Element unique RILIS schemes Principle of RILIS
E0
E1
E2
Rydbergstate
AIS
IP
Atom
Ion
RILI
S la
sers
522nd of February 2013 | LA³NET Laser Based Particle Sources 2013 | Sven Richter | [email protected]
Dual RILIS Laser Setup
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
l – meterDye 2 SHG
Narrowband Dye
THGDye 1
Ti:Sa 1
Ti:Sa 3
Nd:YAG
Nd:YAG
10 kHz Master clock
Delay generator
LabVIEW based DAQSlide: S. Rothe
622nd of February 2013 | LA³NET Laser Based Particle Sources 2013 | Sven Richter | [email protected]
Ion Source & Beam Purity
• Nonselective surface inonization in hot cavity
• Strong interference in experiments by isobaric contamination
Surface Ionization
722nd of February 2013 | LA³NET Laser Based Particle Sources 2013 | Sven Richter | [email protected]
Ion Source & Beam Purity
• Increase of ionization efficiency for the element of interest
• Better selectivity but no suppression of isobaric contaminants
RILIS
822nd of February 2013 | LA³NET Laser Based Particle Sources 2013 | Sven Richter | [email protected]
• Suppression of surface ions by electrostatic repeller• High selective laser ionization inside the LIST• Ion guide towards extraction by transverse rf-trapping field
Ion Source & Beam PurityLaser Ion Source & Trap
Na23
Mg24
Al27Mg25 Mg26
ion
curr
ent [
A]
mass [u]
922nd of February 2013 | LA³NET Laser Based Particle Sources 2013 | Sven Richter | [email protected]
Principle of using the LIST at ISOLDE
Slide: D. Fink
RILIS 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
Dye 2
Mg RILIS setup
1022nd of February 2013 | LA³NET Laser Based Particle Sources 2013 | Sven Richter | [email protected]
LIST run in 2011: results
• First on-line test of the LIST in May 2011Physics case: Mg
• Realistic on-line conditions over 48 hours
• Suppression limited by backgroundof Faraday cup
• No significant changes of LIST performance during online run
50LIST
RILIS
IC
IC6001
LIST
RILIS
IC
IC
-200 -100 0 100 2001E-12
1E-11
1E-10
39K before p 39K after p
Ion
Curre
nt (A
)Repeller Voltage (V)
Effective suppression of surface ions but with lower laser ionization efficiency.
1122nd of February 2013 | LA³NET Laser Based Particle Sources 2013 | Sven Richter | [email protected]
LIST run in 2012: overview
RILIS schemes for Po
UCx target
Annular Si Si216Pobeam
C-foils20 mg/cm2
α detector (Windmill, Leuven)
Goals of 2nd LIST online run:
• First real online application of LIST at ISOLDE
• Provide highly purified beams of Mg and Po
• Proof of principle with strongly outgassing UCx target
• Test of improved LIST design for higher efficiency
1222nd of February 2013 | LA³NET Laser Based Particle Sources 2013 | Sven Richter | [email protected]
LIST run in 2012: suppression
RILIS vs. LIST mode
(2011) 27Mg:
30Mg:
208Po:20
LIST
RILIS
IC
IC
50LIST
RILIS
IC
IC
(2012)
Analysis of suppression factors for different isotopes
Suppression
• Usually > 3 orders of magnitude
• Exceptions observed for some isotopes
Limits by LIST electrode structure
Supp
ress
ion
fact
or
1322nd of February 2013 | LA³NET Laser Based Particle Sources 2013 | Sven Richter | [email protected]
LIST run in 2012: suppression limits
Suppression Limits
• Deposit of neutral atoms on quadrupole rods
• Decay inside the LIST
• Other ionization mechanisms
Secondary isobaric contamination
1422nd of February 2013 | LA³NET Laser Based Particle Sources 2013 | Sven Richter | [email protected]
Unexpected production of short-lived isotopes
217Rn: T1/2 = 540µs,α-decay of 221Ra
α-spectrum at mass 217u:
217 R
n
α-spectrum at mass 216u:
216At: T1/2 = 300µs,α-decay of 220Fr
• Deposit of mother nuclei (e.g. 220Fr, 221Ra) on quadrupole rods
• Decay inside the LIST
• Other ionization mechanisms and extraction towards ISOLDE beam line
0.2 counts/sec of short-lived isotopes (216At, 217Rn)
general half life of produced isotopes at ISOLDE: > 1 ms
1522nd of February 2013 | LA³NET Laser Based Particle Sources 2013 | Sven Richter | [email protected]
LIST run in 2012: Laser Spectroscopy on Po
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:
Work of T. E. Cocolios, M. Seliverstov et al.
1622nd of February 2013 | LA³NET Laser Based Particle Sources 2013 | Sven Richter | [email protected]
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
Slide: D. Fink
1722nd of February 2013 | LA³NET Laser Based Particle Sources 2013 | Sven Richter | [email protected]
Summary
• Suppression of isobaric contamination and selectivity improvement of RILIS by LIST
• Proof of principle by 2011 on-line run:
o Suppression of > 1000
o Ionization efficiency reduction of ≈50 (Mg)
• First real physics application in 2012:
o Laser spectroscopy of 216-217Po possible due to suppression of Fr by LIST
o Suppression factor > 1000
(limited by depositon and decay inside the LIST for few isotopes)
o Ionization efficiency reduction of ≈20 (Mg,Po)
o Production of ion beams of short-lived ions by in-trap decay
LIST demonstrated its ability – a new option for ISOLDE users
1822nd of February 2013 | LA³NET Laser Based Particle Sources 2013 | Sven Richter | [email protected]
Thank you for LISTening
… and special thanks to all the collaborators:
1922nd of February 2013 | LA³NET Laser Based Particle Sources 2013 | Sven Richter | [email protected]
Outlook
• Analyzing rf-field of the LIST by simulations
• Almost the same rf-field in centeras with large rod diameter
• 5 times higher rf-voltage necessary
• next step: planning a prototype
• Improvements for the next LIST version
• Ensuring suppression for all isotopes
• Avoid deposit of neutral atoms on quadrupole structure
Surface reduction of quadrupole rods
2022nd of February 2013 | LA³NET Laser Based Particle Sources 2013 | Sven Richter | [email protected]
LIST Parameters
• Two operational modes of LIST:− RILIS (ion guide) mode− LIST (repelling) mode
• Electrode potential (Repeller):− -50 V (ion guide)− 10 V (repelling)
• LIST RF field ( 1 MHz)− Amplitude 10 – 1000 Vpp
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