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RF design of a high-gradient medical linac accelerating structure

RF design of a high-gradient medical linac accelerating structure. Stefano Benedetti, TERA Foundation. Project summary and goals. Design the prototype of a high gradient 3 GHz proton accelerator operating in a backward Travelling Wave mode with 5pi/6 phase advance. Compact size.

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RF design of a high-gradient medical linac accelerating structure

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  1. RF design of a high-gradient medical linac accelerating structure Stefano Benedetti, TERA Foundation CLIC Workshop, 03-07 February 2014, CERN

  2. Project summary and goals Design the prototype of a high gradient 3 GHz proton accelerator operating in a backward Travelling Wave mode with 5pi/6 phase advance Compact size Acceptable BDR A general overview on the TULIP project will be given Thursday 6 at 2pm by Prof.Amaldi

  3. Cell design

  4. Tuning by dimple tuners tuner tuner A. Degiovanni

  5. Tapered structure • Coupling hole radii have been adjusted from cell to cell in order to get a group velocity between 0.4% and 0.2% of c in the tank • Cell diameter has been adjusted accordingly, to maintain the resonant frequency of 2.9985 GHz • A precision of 1 μm in the cell diameter has been reached

  6. Tank design acD11=(acD010+acD011)/2 acD2=(acD01+acD02)/2 Rc01 -> acD01 1st and 12th cell diameters depend on the couplers design

  7. Out cell coupling - preliminary -47 dB

  8. In cell coupling - issues Regular coupling holes radius By reducing the coupling holes radius closer to the coupling slot the problem is solved Sc up to 40% higher than in the regular cells holes But we affect the vg, so the Ez

  9. In cell coupling - preliminary -44 dB

  10. Tank optimization • Minimization of the SW pattern by adjusting the out-coupler • Final optimization of the in-coupler to get the final design of the tank

  11. Electric field distribution P0 Pload

  12. A bwTW structure P0 Pload Pw Beam

  13. ModifiedSc plot The Sc/Ea^2 < 7e-4 A/V constraint is respected

  14. Reflection from input (red) and from output (brown) -27 dB -67 dB

  15. Electric field EZ – 2.5 MW Good agreement between the analytical and the simulatedresults To reach the desiredaccelerating gradient Ea=EzT of 50 MV/m, the needed power isapproximately 9 MW The energy gain in the first tank willbe of about 9-10 MeV

  16. RF phase advance The RF phase advance per cellis 150° at 2.9985 GHz

  17. What next… To summarize… Few modifications to the geometryafter the discussion with VDL but the overall impact isnegligible Cellsshouldbeready by the end of autumn at most Low and high power tests on the structure to studyoverall performances and BDR Thanks for your attention! Special thanks to KT for financing the project

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