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HOM Status Summary

HOM Status Summary. Binping Xiao On behalf of DQWCC team, BNL In collaboration with CERN. Quick Reminder: achievements. Filter design wide stop band (<80dB, several tens of MHz) at 400MHz, high pass at frequency 570MHz~2GHz Hook coupler design 471 Qext at 579.8MHz (1 st HOM),

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HOM Status Summary

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  1. HOM Status Summary Binping Xiao On behalf of DQWCC team, BNL In collaboration with CERN

  2. Quick Reminder: achievements • Filter design • wide stop band (<80dB, several tens of MHz) at 400MHz, high pass at frequency 570MHz~2GHz • Hook coupler design • 471 Qext at 579.8MHz (1st HOM), • 507 Qext at 682.6MHz (2nd HOM), • 233 Qext at 697.3MHz (3rd HOM). • HOM mapping • frequency, Qext, R/Q, mode configuration etc., up to 2GHz are calculated by Silvia (without filter) and Zenghai (with filter). 10mm x 20mm

  3. Quick Reminder: problems • Qext problem (Silvia) • with filters, the calculated Qextfrom CST MWS for the 1st HOM is ~7000 (Silvia), while from Ace3P is ~2000 (Zenghai). • Some high Qext modes (Binping) • caused by impedance mismatch between the hook and the filter. • High Qext -> high shunt impedance • High magnetic field area (Binping) • For the fundamental mode, a high magnetic field area (14% higher than the max on the cavity inner surface) appears in the corner between the first rod inductor and the hook. 81mT/ 3.4MV

  4. Recent R&D • Filter optimization • Qext optimization • Power estimation • Prototyping

  5. Recent R&D: filter optimization Slope for multipactingsuppression Bleding for field suppression Next: Put the output port aside, Mod to avoid conflict on flange. 20mm in diameter 580 MHz -2.6 dB 742 MHz -1.9 dB 683 MHz -10.7 dB 400±30 MHz

  6. Recent R&D: Qext(1) Idea: change the LC of filter and hook to get better impedance match. 45°, possible 60°? Plate 3mm Hook shape Hook position

  7. Recent R&D: Qext(2) Longitudinal shunt impedance (Ohm/cavity) Meet the requirement

  8. Recent R&D: Qext(2) Vertical shunt impedance (Ohm/m/cavity) 1.172GHz Qext Original design: w/o filter 900 w/ filter 10^4 Modified design: w/ filter 10^7 Mismatch? 45/60degree solution: what happened at 1.172GHz?

  9. Recent R&D: Qext(2) Horizontal shunt impedance (Ohm/m/cavity) 45/60degree solution: needs a little bit more optimization

  10. Recent R&D: power estimation • Use the beam spectrum provided by Rama • Use the shunt impedance provided by Zenghai • Direct calculation gives 115 Watt/Cavity • Manually adjust each HOM frequency in ±1 MHz range to match the “worst case” of beam spectrum, the HOM power changes to 1003 Watt/Cavity • Calculation needs to be re-done before finalizing the HOM design.

  11. Recent R&D: Prototyping Will figure out the ports connection based on new design.

  12. miscellaneous • Difference on R/Q (Silvia and Rama) • Shunt impedance budget (Sergey) • Bead pulling is on-going based on PoP cavity • Find a solution for 45 degree ports (Binping)

  13. End

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