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Last SEISM magnetic field measurements and general considerations on ion sources

EUROnu – 6 th WP4 meeting, 8-9 November 2010, LNL Legnaro. ( SEISM : S ixty G Hz E CR I on S ource using M egawatt Magnets). Last SEISM magnetic field measurements and general considerations on ion sources. Mélanie MARIE-JEANNE

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Last SEISM magnetic field measurements and general considerations on ion sources

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  1. EUROnu – 6th WP4 meeting, 8-9 November 2010, LNL Legnaro (SEISM: Sixty GHz ECR Ion Source using Megawatt Magnets) Last SEISM magnetic field measurements and general considerations on ion sources Mélanie MARIE-JEANNE J. Angot, C. Fourel, J. Giraud, J. Jacob, T. Lamy, L. Latrasse, J. Morfin, P. Sole, T. Thuillier, J.-L. Vieux-Rochaz from LPSC Grenoble C. Auternaud, F. Debray, M. Kamke, J. Matera, R.  Pfister, C. Trophime, E. Verney from LNCMI Grenoble

  2. Outline • SEISM magnetic structure characterization • Technical challenges of the tests • Last magnetic field map • Towards a 60GHz ECR ion source • Next steps for the development of the SEISM prototype • General considerations on ECR ion sources • Indicative planning Mélanie MARIE-JEANNE 6th WP4 - Legnaro, Italy

  3. Magnetic field measurements (1) Technical challenges on the test stand Inlet Injection tank Extraction tank Radially cooled helices (LNCMI technique) • REMINDER • February 2010: • Hydraulic tests withcopperhelices • Measurements up to 7000A appliedcurrent • 10bar - 12l/s in each tank • 280kW dissipated power • 14m/s water speed in the radial helicesslit • Excessive cavitation Water distribution flange Outlet Mélanie MARIE-JEANNE 6th WP4 - Legnaro, Italy

  4. Magnetic field measurements (1) 28l/s waterflow in each tank ∆P ~ 0.5 bar in the helices ∆P ~ 2.5 bar in the helices 19.5 bar on the poral disc 16.5 bar on the poral disc Technical challenges on the test stand SOLUTION: Porous discs to slow down the flow in SEISM, but not in the LNCMI magnet running in parallel • July 2010: first try • Measurements up to 10500A applied current (0.7 MW) • no more cavitation, but a filter damaged after 24 hours of run • October 2010: second try • Measurements up to 15000A applied current (1.5 MW) • SUCCESS ! Disc deformation Mélanie MARIE-JEANNE 6th WP4 - Legnaro, Italy

  5. Magnetic field measurements (2) AFTER:direct electrical connection • 2x 15000A applied • Electric power needed • M5 ≈ 0 MW (off) • SEISM ≈ 1.5 MW • Cooling ≈ 1.2 MW • TOTAL ≈ 2.7 MW LIMITATIONS: minimum water flow needed: 120 l/s porous discs lifetime Validating independent electrical connection BEFORE: electrical connection in series with a running magnet (M5) hydraulic connection in parallel with M5 15000A - 400V power supplies • 2x 13000A applied • Electric power needed • M5 ≈ 6 MW • SEISM ≈ 1.1 MW • Cooling ≈ 1.2 MW • TOTAL ≈ 8.3 MW + - A1 + - A2 13T - 10MW M5 magnet LIMITATIONS: minimum water flow needed: 120 l/s maximum current applied: 2x13000A SEISM prototype Mélanie MARIE-JEANNE 6th WP4 - Legnaro, Italy

  6. Magnetic field measurements (3) z 0mm x 30mm 15mm 0mm Magnetic field map up to 15000A Hall probes Jack Mélanie MARIE-JEANNE 6th WP4 - Legnaro, Italy

  7. Magnetic field measurements (4) 28 GHz 28 GHz 28 GHz 14 GHz 14 GHz - 18 GHz Magnetic field map 60 GHz Half-magnetic field objectives completed ! Mélanie MARIE-JEANNE 6th WP4 - Legnaro, Italy

  8. Towards the ion source (1) Unexplained discrepancies No consequence for plasma tests Mélanie MARIE-JEANNE 6th WP4 - Legnaro, Italy

  9. Towards the ion source (2) Temperature calculations Snapshot of the outer coil insulators after 40 hours of run up to 7000A Inserting a camera to have a look: ++ insulators still aligned ! -- color indicates local temperature is higher than expected insulators Ways of improvement • « prepreg » for pre-impregnated composite fibres G11 dry woven glass fabric impregnated with epoxy resin Specified maximum continuous operating temperature: 165°C Specified breakdown voltage condition: 35kV/mm Heating tests on prepreg Damaged resin insulators Height calibrating pieces Mélanie MARIE-JEANNE 6th WP4 - Legnaro, Italy

  10. Towards the ion source (3) mass separation dipole all charge states calibrated leak one charge state O5+ O4+,... O6+ O+ O2+ O3+ Xen+ 2) Total efficiency: 80% for gas, 1% < eff < 10% for metal 3) Efficiency distributed between various charge states General considerations on ECR ion sources extraction optics 1) Classical ion source (min B) Mélanie MARIE-JEANNE 6th WP4 - Legnaro, Italy

  11. Towards the ion source (3) number of particles General considerations on ECR ion sources O5+ O4+,... Without Xe+ injection With Xe+ injection O6+ O+ O2+ O3+ Xen+ November 8, 2010 Mélanie MARIE-JEANNE 6th WP4 - Legnaro, Italy 11/16

  12. Towards the ion source (4) High Voltage to extract high currents anode voltage Child’s law: anode space charge -limited current anode-cathode distance A few parameters of interest Pulse duration and total extracted current 1013 at/s in continuous mode: 1 pµA 1013 at/s in a 100 µs pulse : 10 pmA + buffer gas in a 100 µs pulse ! Experimental Ar4+ preglow pulse from PHOENIX V2 at 28GHz Izotov I.V. et al IEEE Transactions on Plasma Science36/4 (2008) 1494-1501 --> Space charge problems expected Mélanie MARIE-JEANNE 6th WP4 - Legnaro, Italy

  13. Towards the ion source (5) O5+ O4+,... O6+ O+ O2+ O3+ 2) Charge state distribution Xen+ Challenges of the SEISM prototype A test bench to study SEISM 28GHz plasma 28GHz SEISM 2x15000A - 1.5MW mass separation dipole extraction optics all charge states calibrated leak one charge state 1) Beam extracted from the cusp 3) Pulsed mode tests (pulse duration, efficiency) Mélanie MARIE-JEANNE 6th WP4 - Legnaro, Italy

  14. Indicative planning (1) Year 2011 • Plasma chamber design • Permanent room at LNCMI is under funding request for first tests at 28 GHz Mélanie MARIE-JEANNE 6th WP4 - Legnaro, Italy

  15. Indicative planning (2) Near future • Preparation to raise the current to full intensity (30kA) • Adding direct voltage reading on each individual helix • Adding temperature reading on local non-cooled parts (insulators) • Insulators replacement ? What kind ? • 60 GHz gyrotron is currently under construction at IAP-NN (ISTC contract) Mélanie MARIE-JEANNE 6th WP4 - Legnaro, Italy

  16. Conclusion • The SEISM magnetic structure was characterized • The prototype works independently using LNCMI current and water supplies • The magnetic field produced at 15000A allows ECR at 28GHz • The SEISM ECR ion source will now be designed • Discrepancies with the expected magnetic field should be understood, alternative insulation methods should be investigated in order to raise the current to 30000A • One aims first at producing a 28GHz plasma to study the ion extraction from the CUSP structure (total current) and the charge state distribution (efficiency for one given beam) • The design and construction • of the source components (plasma chamber, gas and RF injection, ion extraction optics) • of an independent test stand (possibly at LNCMI) will take place in 2011. Mélanie MARIE-JEANNE 6th WP4 - Legnaro, Italy

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