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ECR LIGHT ION SOURCES at CEA/SACLAY

ECR LIGHT ION SOURCES at CEA/SACLAY. R. Gobin, P-Y. Beauvais, A. Ben Ismail, D. Bogard, O. Delferrière, D. De Menezes, R. Duperrier, Y. Gauthier, F. Harrault, P-A.  Leroy, O. Tuske, D. Uriot, Commissariat à l'Energie Atomique, CEA-Saclay, DSM/DAPNIA/SACM 91191 Gif sur Yvette Cedex, France.

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ECR LIGHT ION SOURCES at CEA/SACLAY

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  1. ECR LIGHT ION SOURCES at CEA/SACLAY R. Gobin, P-Y. Beauvais, A. Ben Ismail, D. Bogard, O. Delferrière, D. De Menezes, R. Duperrier, Y. Gauthier, F. Harrault, P-A. Leroy, O. Tuske, D. Uriot, Commissariat à l'Energie Atomique, CEA-Saclay, DSM/DAPNIA/SACM 91191 Gif sur Yvette Cedex, France R. GOBIN ECPM 06, NICE, France

  2. HPPA projects In the 90’s, as HPPA projects grew, CEA started the IPHI project with the SILHI source to produce 100 mA H+ at few MeV Few years ago, the current list of projects was as follow: One of the main request, especially for ADS is the reliability  ECR ion sources (no filament, no antenna) R. GOBIN ECPM 06, NICE, France

  3. Silhi source (1) ECR Source  Resonance zone:  = e B / m , pulsation e, electron charge B, magnetic field m, electron mass. 2.45 GHz  875 Gauss External Collaborations CEA Grenoble, IPNO, LANL, INFN, GSI, GANIL, U. Frankfurt, Industrial Companies Students Thesis or training sessions R. GOBIN ECPM 06, NICE, France

  4. Bat 706 Silhi source (2) SILHI operates at 2.45 or 3 GHz 1 ECR zone at RF entrance Pentode extraction system Since 1996, SILHI produces H+ beams with good characteristics: H+ Intensity > 100 mA at 95 keVH+ fraction > 80 % Beam noise < 2% 95 % < Reliability < 99.9 % Emittance < 0.2  mm.mrad CW or pulsed mode R. GOBIN ECPM 06, NICE, France

  5. * Due to neutron production Nominal results In CW mode, the source routinely produces 130 mA total (> 80% H+) at 95keV R. GOBIN ECPM 06, NICE, France

  6. Automatic procedures I total 114 mA +/- 0.2 (Proton 77 %) 7 breaks (1 spark), automatic restart (2.5 mn) 2.5 min. 20 sec. Reliability ECR sources are especially well known for the reliability R. GOBIN ECPM 06, NICE, France

  7. Short "holes" in CW mode Tests performed with SILHI source producing 80 mA total beam with a 9 mm extraction aperture. Beam off: 500 µs/200 ms Beam off: 300 µs/200 ms Orange curves directly report current measured on FC with 50 Ohms (no capacitance) Fall time and rise time :  20 - 30 µs Same rise and fall time has been observed with 1 Hz repetition “holes”. R. GOBIN ECPM 06, NICE, France

  8. 2 solenoids LEBT when HI beam interacts with residual gas, space charge compensation occurs : H+ + H2 H+ + H2+ + e- Generally, electrons are confined in the beam and secondary ions are repelled towards the walls. Space charge can reach close to 100 % in drifts but in solenoid magnetic field, the compensation dramatically decreases. R. GOBIN ECPM 06, NICE, France

  9. Emittance measurement Frankfurt EMU (slit + multi wire scanner) has been installed on the SILHI LEBT, downstream the 2nd solenoid. High intensity (100 mA total) beam Emittances have been measured in pulsed mode (600 µs, 5 Hz) by changing focusing (sol 1 and sol 2). • ion source shows a stable and reproducible operation • small fraction of impurities in the beam (100 mA with H+  90%) • ε(95 %) = 0.3-0.5 π.mm.mrad (rms norm), • emittance increases with Sol 2 focusing • emittance dominated by the LEBT and not by the ion source. R. GOBIN ECPM 06, NICE, France

  10. Nitrogen Injection • Space charge effects is generally observed in the LEBT • Additional studies are expected Additional gas injection (N2) influences the space charge and the emittance (confirmed by this campain) with N2 3.5 x 10-5 mbar R. GOBIN ECPM 06, NICE, France

  11.  The SILHI source and LEBT already moved twice. It is now installed in the IPHI building 2006 80 mA 95 keV through RFQ cone SILHI: easy restart After each move and a complete cleaning and reassembly, the first beam reached 70mA within a few minutes. It took only few days to obtain > 100mA with low spark rate. 2003 R. GOBIN ECPM 06, NICE, France

  12. RFQ entrance optimisation Hα Balmer line of H2at 646.2 nm June 2006 January 2006 RFQ entrance Sol 2 Cone ACCT Behind the cone H2+ and H3+ disapeared Without cone The RFQ entrance cone (water cooled copper) has been recently installed Optical beam measurement (Doppler shift analysis) An automatic routine allows beam matching by tuning both solenoids and steerers. R. GOBIN ECPM 06, NICE, France

  13. SILHI technical choices To limit possible failures and to optimize the reliability: • Quartz window protected (water cooled bend) • Electrode shape optimization to minimize electric field • Large safety margins on all PS (HV and others) • Optimization of PS air or water cooling • Separate cable path and shielding for signals and power • Galvanic insulation of analog and digital signals • Use of EMI hardened devices for all sensitive electronics • Development of EPICS automatic start/rest. procedures • Development of beam current feedback • Development of specific beam diagnostics rjgobin@cea.fr R. GOBIN ECPM 06, NICE, France

  14. C D n 1+ n+ UCx IS ECR DEUTERON needs Few years ago, GANIL at Caen proposed an upgrade of SPIRAL SPIRAL 2 facility plans to use 40 MeV-5mA D+ beam to produce neutron flow leading to Radio-Active Beam by interaction with Uranium Carbide Target. SILHI already produced Deuteron beam in pulsed mode (130mA – 100 keV – D+ 96 %) in 2001  capability to easily restart after displacement with a known magnetic structure andstandard parameters. Proposition: SILHI type source, 2.45 GHz ECR source with permanent magnets R. GOBIN ECPM 06, NICE, France

  15. Kept Options (efficient on SILHI):  BN discs Window behind a bend Tunable puller Electron repeller D+ source original design Spiral 2 RFQ requests: Source running in CW or pulsed mode Particles: D+ and H2+ (for conditioning), Energy: 40 keV Intensity: 0.15 or 5 mA (continuously tunable from 0 to I max for conditioning) Emittance < 0.2  mm.mrad High D+ fraction, High stability and reliability Long life time (> 3 months) New technical choices Coils replaced by permanent magnets No magnetic shielding Dedicated extraction system 40 kV  no HV platform RF Injection via DC break R. GOBIN ECPM 06, NICE, France

  16. D+ source (general design) Penning discharges pushed us to install iron shielding. High impurity fraction forced to install waveguide pumping. R. GOBIN ECPM 06, NICE, France

  17. D+ beam characterization The magnetic configuration has been optimized in H+ and then the source has been characterized in D+ 20 to 30 minutes to switch from H+ to D+ beam Gas mixing: Gas mixing injection into plasma chamber (ex: Deuterium and Nitrogen) has been done to obtain very low current (from 100 µA to 2 mA) with good stability. R. GOBIN ECPM 06, NICE, France

  18. New test bench (BETSI) is under construction, it will be dedicated to PM source studies. High Intensity PM source With hydrogen injection, Spiral 2 source produced: 1) Intensity: 9.2 mA total RF power 800 W and extraction hole 3 mm; beam density : 130 mA/cm2 2) Species Fraction: H+ 71%, H2+ 12%, H3+ 1.6%, Impurities 15% 3) Reliability: 6 days run with no beam off (40 kV – 9 mA) By changing the plasma electrode, total extracted beam reached 109 mA à 85 kV (75% H+) with extraction hole 9 mm The source then produced 85 mA total beam at 80 kV, for 4 days with no beam off R. GOBIN ECPM 06, NICE, France

  19. Experimental set up and plasma zoom Installation of a stainless steel grid in the plasma chamber allows separating ECR plasma generation and H- ion production H- test stand Technical options Rectangular plasma chamber 2 tunable coils 5 mm extraction aperture Source working at 2.45 GHz Protected window ECR zone at RF entrance Available plasma diagnostics R. GOBIN ECPM 06, NICE, France

  20. Now, max extracted current in pulsed mode: 3.5 mA (few ms, 10 Hz) Magnetic configuration Radial field Axial field Axial field remains in production zone Intensité de H- collectée en fonction du champ du déviateur d’électrons Radial field due to electron steerer also exists in production zone H- ion production depends on radial field R. GOBIN ECPM 06, NICE, France

  21. Paroi Interne BR R Multipolar magnetic structure Axe de la source A new magnetic structure is ready for tests 24 permanent magnets In Halbach configuration Tubular resonance zone r No longitudinal magnetic field on the axis R. GOBIN ECPM 06, NICE, France

  22. General developments Knowledge improvement is expected A better understanding of RF and plasma interaction would allow source efficiency improvement and more efficient extraction simulations.  theoretical program under progress •  plasma diagnostics • - spectroscopy • - Langmuir probe • - interferometer •  new ridge waveguide and coupling system In parallel, Prepare the conditioning and running mode of Iphi Prepare a long run test for ADS program R. GOBIN ECPM 06, NICE, France

  23. Conclusion The first Saclay ECR light ion source currently produces 100 mA of H+ beam for several years with good performance in term of reliability, stability, beam noise, emittance… The beam is now ready to be injected into the IPHI RFQ. Moreover, recent developments allow us to produced such high intensity beams with a permanent magnet source. High intensity H- ion beam production looks difficult with this kind of source but few mA are routinely produced in pulsed mode. Future developments will allow a better understanding of the different sources and help for the design of new installations. To conclude, such ECR light ion sources are really powerful and efficiently fit in with the high intensity accelerator requests. R. GOBIN ECPM 06, NICE, France

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