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The PMT (Trikon) MØRI source

Commercial helicon sources need heavy magnets and cannot cover large substrates. The PMT (Trikon) MØRI source. Solution 1: Use distributed sources. Experiment at PMT, ca 1995. However, still need a large electromagnet. Solution 2: Use permanent magnets. Material: NdFeB Bmax = 12 kG.

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The PMT (Trikon) MØRI source

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  1. Commercial helicon sources need heavy magnets and cannot cover large substrates The PMT (Trikon) MØRI source

  2. Solution 1: Use distributed sources Experiment at PMT, ca 1995 However, still need a large electromagnet

  3. Solution 2: Use permanent magnets Material: NdFeB Bmax = 12 kG The magnets are dangerous! The innovation involves two parts: 1. Novel use of PMs 2. Use of the low-field peak effect. UCLA

  4. Internal field External field The field of annular permanent magnets Plasma created inside the rings follows the field lines and cannot be ejected. The field reverses at a stagnation point very close to the magnet.

  5. External field Internal field Proof of principle on 3” diam tube The bottom curve is when the tube is INSIDE the magnet

  6. Mechanism of the Low Field Peak Constructive interference of reflected wave Basic helicon relations UCLA

  7. Low-field peak Design of discharge tube: maximize the loading resistance Calculations are done using the HELIC code of D. Arnush

  8. Final design of “stubby” discharge tube

  9. Medusa 2: An 8-tube linear test array Top view UCLA

  10. Probe ports The array source is vertically compact Side view The magnets can be made in two pieces so that they hold each other on an aluminum sheet. Once placed, the magnets cannot easily be moved, so for testing we use a wooden support. UCLA

  11. Wooden frame for safe storage UCLA

  12. The wooden magnet frame is used in testing UCLA

  13. Antenna connections For CW operation, all connections were solidly soldered, and RG/393 teflon-insulated cable was used. Cable connectors cannot take the startup voltage. UCLA

  14. Matching circuit for N tubes in parallel The problem with array sources is that the cable lengths cannot be short. The match circuit cannot be close to all the tubes. UCLA

  15. Matching sets limits on antenna inductance and cable lengths. There is a “sweet spot” for tube design when RF is considered. C1, C2 for N=8, L = 0.8mH, Z1 = 110 cm, Z2 = 90 cm

  16. A water-cooled, 50-W, low resistance, rectangular transmission line

  17. Medusa 2 in operation UCLA

  18. 0 3.5 Density profiles across the chamber Compact configuration, 3kW Side Langmuir probe << 4” below tubes << 7” below tubes UCLA

  19. -7 0 7 14 Density profiles across the chamber Staggered configuration, 3kW Bottom probe array UCLA

  20. Density profiles along the chamber Staggered configuration, 3kW Bottom probe array UCLA

  21. Density profiles along the chamber Compact configuration, 3kW Bottom probe array UCLA

  22. A compact, stackable module The match circuit fits on top of the array

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