studies for developing the mw-station ion source
DESCRIPTION
Studies for Developing the MW-station Ion Source. A compact and efficient design to get 10 15 fissions/s Cylindrical liquid Hg converter (~10 l.) Surrounding annular fission target (~5 l.) The annular fission target split up in 8 independent fission targets - PowerPoint PPT PresentationTRANSCRIPT
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Christophe Lau et al. EURISOL-DS Town Meeting, CERN 27-28 Nov. 2006
Studies for Developingthe MW-station Ion Source
A compact and efficient design to get 1015 fissions/s
Cylindrical liquid Hg converter
(~10 l.)
Surrounding annular fission target
(~5 l.)
The annular fission target split up
in 8 independent fission targets
8 x 1,6 kg of Uranium
standard UCX (3 g/cm3 of U).
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Christophe Lau et al. EURISOL-DS Town Meeting, CERN 27-28 Nov. 2006
Overall issues
• How to connect ion source to such a target system?
– Multiple ion sources? Acceptable for the design of radioactive beam line?
– Multiple transfer lines? Cf. Thierry STORA’s presentation.
• What kind of ion source?
– Capable of operating under the vapour from the bulky target.
– Capable of withstanding the level of radiation generated close to the target.
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Christophe Lau et al. EURISOL-DS Town Meeting, CERN 27-28 Nov. 2006
Basic scheme
Q = C x ∆P with C order of 1 l/s. (molecular flow)
~10-6 < PIS < ~10-5 mbar Qout < ~10-5 mbar.l/s (negligible)
PIS ~ Ptarget
If no specific device on transfer line, most target out-gassing goes into the ion source.
Ctransfer
PIS
Ptarget
[UC2 @ 2000 °C] ~10-5 mbar
ion sourcetarget
Corifice
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Christophe Lau et al. EURISOL-DS Town Meeting, CERN 27-28 Nov. 2006
Vapour from the fission target
Considering a piece of 1/8 target
(1,6 kg of nat.U):
• Overall radioactive nuclei production
~1016 nuclei/s in target; if 10% released
~1015 nuclei/s ⇔ ~10-4 mbar.l/s
• Stable out-gassing
UC2 out-gassing is dominant (x100 larger than Ta out-gassing);
Target surface at least x10 wider than standard
> 10-1 mbar.l/s (equilibrium) only a part reaches the ion source.
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Christophe Lau et al. EURISOL-DS Town Meeting, CERN 27-28 Nov. 2006
What kind of ion source?
• Target out-gassing surface is a few x10 wider than standard
for efficient ion sources (εion ~ 1%): total extracted beam ~mA
• Ion source close to the target 1014 neutrons/cm2/MW of beam
ion source position
A. Herrera-Martinez et al.
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Christophe Lau et al. EURISOL-DS Town Meeting, CERN 27-28 Nov. 2006
What about ECRIS ?
• OK for operating with such out-gassing conditions
• Possibility of transfer-line cooling to reduce metal vapours
• RF injection issue
• Radiation damage of magnetic confinement system:
– Possibility of using coils instead of permanent magnets
– Radiation damage of insulators? e.g. glass fibres ~10 MGy
Such studies are in progress for SPIRAL-2…
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Christophe Lau et al. EURISOL-DS Town Meeting, CERN 27-28 Nov. 2006
FEBIAD-type Ion Source ?
• Not dedicated for operating with high vapour flow:
– Standard FEBIAD operate up to 10-3 mbar.l/s
– EBGP (radial type, by J.M. Nitschke) up to 10- 4 mbar.l/s
• Nielsen and Nier-Bernas ion sources can operate:
– e.g. beams of a few mA with an emittance of 20 π.mm.mrad @ 40 kV.
– But quick wearing of the cathode.
• Radiation damage of the refractory insulators
– {cathode/anode} need of refractory insulators close to ionization chamber.
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Christophe Lau et al. EURISOL-DS Town Meeting, CERN 27-28 Nov. 2006
IRENA prototype
IRENA prototype based on EBGP (Nitschke, LBL 1985).
Main features:
Minimum of components (no magnet!)
Insulators away from the ion. chamber
Radial cathode more reliable
Cathode Design
hazard of cathode/anode
short
residual pressure in chamber
strong e- emisssion required
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Christophe Lau et al. EURISOL-DS Town Meeting, CERN 27-28 Nov. 2006
IRENA 1st prototype: First results (1)
0
0,5
1
1,5
2
2,5
3
3,5
10 15 20 25 30 35 40 45 50 55 60 65 70 75 80 85 90 95
Mass [u.m.a]
Inte
nsit
y [n
A]
2,7 kW
2,9 kW
Optimal conditions not yet reached: ionization efficiency (Kr): 0.03 % @ 2.10-5 mbar.
Tests interrupted in March 06; to be pursued with a prototype supplied by NIPNE.
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Christophe Lau et al. EURISOL-DS Town Meeting, CERN 27-28 Nov. 2006
IRENA 1st prototype: First results (2)
Total beam intensity comparable to EBGP (~µA)expected by 2000 °C within these operation conditions.
Total beam extracted @ 10-5 mbar as function of cathode heating.
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Christophe Lau et al. EURISOL-DS Town Meeting, CERN 27-28 Nov. 2006
Optimizing IRENA design
Increasing e- emission by
103 to get a prototype
working with MW-target out-gassing.
Another cathode material or
cathode surface x103
(the ionization chamber may reach the typical size of ECRIS)
Further studies using
IES Lorentz code planned in 2007.
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Christophe Lau et al. EURISOL-DS Town Meeting, CERN 27-28 Nov. 2006
What about RILIS ?
• High pressure in the hot cavity
Larger production of non-selected positive ions
Deterioration of the plasma conditions in the cavity
• Possible remedy
Increasing cavity diameter (keeping /L2 ~ constant)
larger conductance and larger surface for increasing e- emission.
Changing cavity material to increase e- emission.
Or…
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Christophe Lau et al. EURISOL-DS Town Meeting, CERN 27-28 Nov. 2006
a plasma confinement structure
Using IRENA radial structure with low voltage to generate lots of radial electrons only for confinement
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Christophe Lau et al. EURISOL-DS Town Meeting, CERN 27-28 Nov. 2006
Resume
• Important to minimize target size as much as possible
Cf. also D. Ridika’s poster
• To get beams from Multi-MW target, many aspects have to be considered: specification on transfer tube, beam extraction,
beam contamination etc.
• Some possibilities for developing MW-station ion sources but requires important R&D works need for support
Acknowledgment:
Many thanks to all collaborators, special thanks to R. Catherall, V. Fedoseev,
A. Herrera-Martinez, Y. Kadi, J. Lettry, D. Ridikas, T. Stora, F. Wenander)