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TDI longitudinal impedance simulation with CST PS

TDI longitudinal impedance simulation with CST PS. Grudiev 20/03/2012. Geometry. All metal and dielectric parts are from PEC. No losses. No ferrites are included. Magnetic wall BC is applied at the horizontal plane PML BCs are applied at the up/downstream ends. Mesh, sigma_z =500mm.

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TDI longitudinal impedance simulation with CST PS

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  1. TDI longitudinal impedance simulation with CST PS Grudiev 20/03/2012

  2. Geometry All metal and dielectric parts are from PEC. No losses. No ferrites are included. Magnetic wall BC is applied at the horizontal plane PML BCs are applied at the up/downstream ends

  3. Mesh, sigma_z=500mm

  4. Longitudinal Wake, sigma_z=500mm

  5. Longitudinal impedance, sigma_z=500mm

  6. Longitudinal impedance, sigma_z=500mm

  7. Mesh, sigma_z=200mm

  8. Longitudinal Wake, sigma_z=200mm

  9. Longitudinal impedance, sigma_z=200mm

  10. Longitudinal impedance, sigma_z=200mm

  11. Mesh, sigma_z=100mm

  12. Longitudinal Wake, sigma_z=100mm

  13. Longitudinal impedance, sigma_z=100mm

  14. Longitudinal impedance, sigma_z=100mm

  15. Mesh, sigma_z=50mm

  16. Longitudinal Wake, sigma_z=50mm

  17. Longitudinal impedance, sigma_z=50mm

  18. Mesh, sigma_z=20mm

  19. Longitudinal Wake, sigma_z=20mm

  20. Longitudinal impedance, sigma_z=20mm

  21. Longitudinal Wake, Summary plots

  22. Longitudinal Wake, Summary plots

  23. Longitudinal Impedance, Summary plots

  24. Longitudinal Impedance, Summary plots

  25. Longitudinal Impedance, Summary plots

  26. Longitudinal Impedance, Summary plots

  27. Different beam locations: b0, b1, b2 b2; X=-68mm b1; X=-8mm b0; X=0

  28. Longitudinal Wake, σz=100mm: b0, b1, b2

  29. Longitudinal Impedance, σz=100mm: b0, b1, b2

  30. Longitudinal Impedance, real part, σz=100mm: b0, b1, b2

  31. Longitudinal Impedance, imaginary part, σz=100mm: b0, b1, b2 Half gap = 8mm b0: Z/n = 155 Ohm/250MHz * 400.8MHz/35640 = 7.0 mOhm b1: Z/n = 150 Ohm/250MHz * 400.8MHz/35640 = 6.7 mOhm b2: Z/n = 70 Ohm/200MHz * 400.8MHz/35640 = 3.9 mOhm

  32. Longitudinal Wake, σz=100mm: b0 PML8 -> PML16

  33. Longitudinal Impedance, real part, σz=100mm: b0, PML8 -> PML16 Almost no difference

  34. Longitudinal Wake, σz=100mm: b0 beam pipe length: 200mm -> 100mm and 300mm

  35. Longitudinal Impedance, σz=100mm: b0, beam pipe length 200mm -> 100mm and 300mm

  36. Longitudinal Impedance, σz=100mm: b0, beam pipe length 200mm -> 100mm and 300mm Beam pipe length of 300 mm is better, but the difference is only at f ~ 0 And the negative offset of the ReZl is always there at the same level.

  37. Ti coating of hBN blocks Dear all, Here is a coating report from Wil (please follow the link), for a batch of BN coated in 2010. The specifications we had been asked to meet were Rsquare<0.5 Ohm. For a thickness of about 5 µm that means a resistivity of about 250 e-8 Ohm.m , larger than the nominal Ti value. This is likely due to the large amount of outgassing from the porous BN material. Cheers, Sergio & Wil See EDMS link https://edms.cern.ch/document/1085514/1 For this coating skin depth in the range from 10 MHz to 1 GHz is 250 um to 25 um which is bigger than the coating thickness of 5 um.

  38. Longitudinal Wake, σz=100mm: b0 PEC -> hBN

  39. Longitudinal Impedance real part, σz=100mm: b0, PEC -> hBN

  40. Longitudinal Impedance, imaginary part, σz=100mm: b0, PEC hBN Half gap = 8mm b0, PEC: Z/n = 155 Ohm/250MHz * 400.8MHz/35640 = 7.0 mOhm b0, hBN: Z/n = 2620 Ohm/400MHz * 400.8MHz/35640 = 73.7 mOhm

  41. Longitudinal Impedance, real part, : b0, hBN, σz=100 - > 50 mm

  42. Influence of the ferrite 4S60

  43. Influence of the ferrite 4S60

  44. Longitudinal impedance gap 16mm hBN, withand w/o 4S60 NO DIFFERENCE

  45. Influence of Mask for RF fingers region

  46. Longitudinal impedance gap 16mm hBN, σz = 100 mm , with and w/o Mask No big difference in CST wakefield solver BUT Saves a lot of mesh in HFSS eigenmode solver

  47. Longitudinal impedance gap 16mm hBN, σz = 50 mm , with and w/o Mask No big difference in CST wakefield solver BUT saves a lot of mesh in HFSS eigenmode solver

  48. R/Q estimate from PEC impedance Reminder from classical P. Wilson, SLAC-PUB-4547 For impedance of N modes with Q >> f/df, where df=c/s_max, for PEC Q~∞

  49. R/Q estimated from longitudinal impedance, hBN, b0, σz = 50 mm 4(Zl-Zl0)*df/πf is plotted where Zl0 = 71 Ohm to make the real part positive

  50. Go to HFSS results

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