1. Radioactive Ion-Beam Purification workshop CERN, September 4th 2007 Introduction J. Lettry CERN ATB

2. A “standard” ISOLDE target: ThO2-184, n-rich Cu
RILIS Cu
60 mm thick Nb cavity
m-bunching
R&D = Optimization of :
Cross section
Release
- Effusion (surf.-temp.)
- Diffusion (grain size, temp)
Ionization efficiency
Selectivity
Chemistry
Ta-Oven 2000º
Ta-transfer line
Re-sleeve
ThO2 Target,
High Resolution
mass Separator
E-field Alkali-
suppression
Ta-converter:
1.4 GeV p  neutrons
N-induced Fission
suppressed Spallation
CERN sept
J. Lettry

3. Kr, Xe and Cs yields, Ta-W spallation n-source Selectivity of n-induced U-fission vs. 1GeV induced U-spallation
The yields of very n-rich isotopes obtained
via neutron induced fission of Th or U
are close to those of high energy protons.
Further developments:
Geometrical optimum and n-reflectors
UC2 + W-converter
Spallation Fission
CERN sept
J. Lettry

4. High temperature cavities for RILIS
CERN sept
J. Lettry

5. RILIS’ Alkali suppression system
Hg Mass marker
Alkali suppression by 5 to 6 orders of magnitude
Micro bunching selectivity factor 30
Ionization efficiency reduction by ~ 2 orders of magnitude
CERN sept
J. Lettry

6. Target prototype: Quartz transfer line for alkali suppression
Independently temperature controlled transfer line with quartz insert for alkaline suppression.
On-line test results:
Temp. from 600º to 1000º
Cs and Rb reduced by 4 orders of magnitude
Zn minimally delayed (RILIS)
E. Bouquerel, R. Catheral, D. Carminati
CERN sept
J. Lettry

7. ISOLDE UCx target, alkali suppression
142Cs for ISOLDE UCx:
Yield = ions/mC
104 suppression factor
but time structure kept
Suppress Alkalis (Cs, Rb)
for pure beams of Cd, Zn
CERN sept
J. Lettry

8. Ion-Sources - selectivity
RILIS (Resonant Ionisation Laser Ion-sources)
Chemical, isotopic and state selectivity, micro bunching
FEBIAD (Forced Electron Beam Induced Arc Discharge)
Thermo-chromatographic and chemical selectivity
Molecular side bands
Hot Surface Ion-Sources Alkalis and rare earth
(LaB6, W, Ta, Nb, …)
ECR Ion-sources (Electron Cyclotron Resonance)
2.45 GHz singly charged, … > 18 GHz multi charged
KENIS (Kinetic Ejection Negative Ion-Source)
Cs-sputtering
CERN sept
J. Lettry

9. Suppression ratios f(T½)
Release function Pi(t) and suppression factor RF-ratio (T1/2) of 90Kr vs. an arbitrary contaminant.
The Released fractions RF(T1/2) of 90Kr and of the arbitrary contaminant are indicated.
CERN sept
J. Lettry

10. Conclusion We shall proceed towards numerical assessment
The Beam Purity BP is the ratio of the desired isotope yield to all other, including molecular side bands and multiple charge states.
BP is a function of:
Cross sections target thickness and projectile nature and flux
Mass resolution
Ion-source efficiencies
Release fractions (diffusion effusion ad-de-sorbtion enthalpies)
Chemical nature of element, surfaces (ad-ab-de-sorbtion enthalpies) and surface purities
Physics setup requirements, down stream recontamination (Traps, ECR 1-n+ EBIS) are mandatory inputs.
1st step BP is within reach, considering only element pairs for each target and ion-source.
CERN sept
J. Lettry