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Radioactive Ion Beam (RIB) Production at ISOLDE by the Laser Ion Source and Trap (LIST) Sven Richter for the LIST-, RILIS- and ISOLDE IS456 Collaborations. Content. Upgrade of the ISOLDE RILIS towards full suppression of isobaric contaminations Standard operation of the ISOLDE RILIS

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slide1

Radioactive Ion Beam (RIB) Production at ISOLDEby the Laser Ion Source and Trap (LIST)Sven Richter for the LIST-, RILIS- and ISOLDE IS456 Collaborations

content
Content
  • Upgrade ofthe ISOLDE RILIS towardsfullsuppressionofisobariccontaminations
  • Standard operationofthe ISOLDE RILIS
  • Principleofthe Laser Ion Source and Trap
  • LIST offline & LIST online run 2011
  • LIST online run 2012
  • Motivation:
  • Experimental Setup:
  • Results:
  • Summary
motivation reduction of isobaric contamination
Motivation: Reduction of Isobaric Contamination

Mass-marker

Hot cavityatomizer

Laser beams

Protons

1,4 GeV

Nuclear

Reaction

Extraction

Target

  • Nickel-78 ion beam: Exampleofisobariccontamination
  • Cross-sectionproductionof different isotopes in a UCxtargetwith 1.4 GeVprotons
scheme of rilis at isolde
Schemeof RILIS at ISOLDE

Element unique RILIS schemes

Principleof RILIS

AIS

Ion

IP

Rydberg

state

E2

RILIS lasers

E1

Atom

Very efficient and element selective ionization!

E0

Panoramic view of the RILIS laser setup:

Slide: D. Fink

dual rilis laser setup
Dual RILIS Laser Setup

Nd:YAG

Dye 2

l–meter

SHG

Dye 1

THG

10 kHz Master clock

NarrowbandDye

RILIS Dye Laser System

GPS/HRS

Delay generator

RILIS Ti:Sa Laser System

Target &

Ion Source

Nd:YAG

Ti:Sa 1

SHG/THG/FHG

Ti:Sa 2

Faraday cup…

Ti:Sa 3

l–meter

LabVIEWbased DAQ

pA – meter

Slide: S. Rothe

ion source beam purity
Ion Source & Beam Purity

SurfaceIonization

  • Nonselectivesurfaceinonization in hotcavity
  • Strong interference in experimentsbyisobariccontamination
ion source beam purity1
Ion Source & Beam Purity

RILIS

  • Increaseofionizationefficiencyfortheelementofinterest
  • Betterselectivity but nosuppressionofisobariccontaminants
ion source beam purity2
Ion Source & Beam Purity

Laser Ion Source & Trap

Mg24

Mg26

Mg25

Al27

Na23

ion current [A]

  • Suppression ofsurfaceionsbyelectrostaticrepeller
  • High selectivelaserionizationinsidethe LIST
  • Ion guidetowardsextractionbytransverserf-trappingfield

mass [u]

principle of using the list at isolde
Principle of using the LIST at ISOLDE

RILIS cabin

High voltagecage

1. 285 nm (UV)

Glass fiber

Repellervoltage

Nd:YAG

  • Dye 1

SHG

2. 552 nm

Rf-generator

Remote control

Dye 2

3. 532 nm

̴ 20m

Mg RILIS setup

+

Target area

+

+

+

ISOLDE hall

+

GPS

Separator magnet

60 keV

Detectors: tapestation, Faraday cup, MCP, WINDMILL

Slide: D. Fink

list run in 2011 results
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
  • Nosignificantchangesof LIST performanceduring online run

Effective suppression of surface ions but with lower laser ionization efficiency.

list run in 2012 overview
LIST run in 2012: overview

Annular Si

Si

UCxtarget

  • Goals of 2nd LIST online run:
  • First real online applicationof LIST at ISOLDE
  • Providehighlypurifiedbeamsof Mg and Po
  • Proofofprinciplewithstrongly outgassing UCxtarget
  • Test ofimproved LIST design forhigherefficiency

216Po

beam

RILIS schemesforPo

C-foils

20 mg/cm2

α detector (Windmill, Leuven)

list run in 2012 suppression
LIST run in 2012: suppression

Analysis ofsuppressionfactorsfor different isotopes

Suppression factor

RILIS vs. LIST mode

Suppression

  • Usually > 3 ordersofmagnitude
  • Exceptionsobservedforsome isotopes
  •  Limits by LIST electrodestructure

(2011) 27Mg:

30Mg:

208Po:

(2012)

list run in 2012 suppression limits
LIST run in 2012: suppression limits
  • Suppression Limits
  • Depositof neutral atoms on quadrupolerods
  • Decayinsidethe LIST
  • Other ionizationmechanisms
  •  Secondaryisobariccontamination
unexpected production of short lived isotopes
Unexpected production of short-lived isotopes

α-spectrum at mass 216u:

α-spectrum at mass 217u:

216At: T1/2 = 300µs,

α-decayof 220Fr

217Rn: T1/2 = 540µs,α-decayof 221Ra

217Rn

  • Depositofmothernuclei (e.g. 220Fr, 221Ra) on quadrupolerods
  • Decayinsidethe LIST
  • Other ionizationmechanismsandextractiontowards ISOLDE beam line
  • 0.2 counts/sec ofshort-lived isotopes (216At, 217Rn)general half lifeofproduced isotopes at ISOLDE: > 1 ms
list run in 2012 laser spectroscopy on po
LIST run in 2012: Laser Spectroscopy on Po

Two measurement campaigns in 2007 and 2009 at ISOLDE/CERN

Mean square radii of Po-isotopes among other elements:

  • Several Po-isotopes remained unstudied due to strong Fr-contamination
  • Using LIST to suppress Fr contamination in 2012

Work of T. E. Cocolios, M. Seliverstov et al.

polonium spectroscopy hfs and is
Polonium Spectroscopy: HFS and IS
  • New Po-decay data on mass 219

Preliminary

  • 216Po and 217Po in one measurement
  • Direct measurement of IS of 216Po and 217Po

Laser frequency offset, GHz

Slide: D. Fink

summary
Summary
  • Suppression of isobaric contamination and selectivity improvement of RILIS by LIST
  • Proof of principle by 2011 on-line run:
    • Suppression of > 1000
    • Ionization efficiency reduction of ≈50 (Mg)
  • First real physics application in 2012:
    • Laser spectroscopy of 216-217Po possible due to suppression of Fr by LIST
    • Suppression factor > 1000(limited by depositon and decay inside the LIST for few isotopes)
    • Ionization efficiency reduction of ≈20 (Mg,Po)
    • Production of ion beams of short-lived ions by in-trap decay

LIST demonstrateditsability – a newoptionfor ISOLDE users

thank you for list ening
ThankyouforLISTening

… andspecialthanksto all thecollaborators:

outlook
Outlook
  • Improvementsforthenext LIST version
    • Ensuringsuppressionfor all isotopes
    • Avoiddepositof neutral atoms on quadrupolestructure
    • Surfacereductionofquadrupolerods
  • Analyzingrf-fieldofthe LIST bysimulations
  • Almostthe same rf-field in centeraswith large roddiameter
  • 5 timeshigherrf-voltagenecessary
  • nextstep: planning a prototype
list parameters
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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