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RF Probe for Mode Identification on TCTWs

This paper presents the use of an RF probe and loop for mode identification on TCTWs. It discusses the measurement techniques and provides insights into the resonances and Q values observed. The results show the effectiveness of the probe in distinguishing between different modes.

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RF Probe for Mode Identification on TCTWs

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  1. TCTW #3 /TCTW #4 Mode identification on the TCTWs by means of an RF probe and loop A. Passarelli Thanks for the help: N. Biancacci, V. Vlachodimitropoulos, L. Teofili

  2. The devices to measure

  3. Check previous works https://journals.aps.org/prab/pdf/10.1103/PhysRevAccelBeams.20.011003

  4. Wire measurements by Nicolò

  5. Nicolò probe measurements on TCT collimator N. BIANCACCI et al., Impedance simulations and measurements on the LHC collimators with embedded beam position monitors, Phys. Rev. Accel. Beams 20, 011003 (2017)

  6. Quarter-wave resonances Looking at the S11 (and similarly for the S22), the large resonances at ≃288 MHz and 576 MHz are the first two quarter-wave resonances characteristic of the coaxial resonator made by the probes (which acts like the inner conductor) and the device (which acts like the outer conductor). These modes can be easily distinguished from the device resonant modes as their frequency shifts when moving the probe position. Alternatively, one could use absorbing foam at the inner side of the probe mounting plates to damp these additional modes.

  7. Nicolò probe measurements on TCT collimator

  8. Nicolò probe measurements on TCT collimator The unloaded Q for the first three low frequency modes was calculated in transmission ensuring low coupling of the loops for different jaw gap positions. This can be achieved retracting the probes at the two ports until a minimal coupling factor, usually less than a percent, is obtained. F. Caspers, RF engineering basic concepts: The Smith chart, arXiv:1201.4068.

  9. NO MODE clearly visible with straight probe on TCTWs

  10. Probe with loop used to see the modes on TCTW #3 and TCTW #4

  11. Measurements on TCTW #3 Three modes clearly visible and Q values similar to Nicolo’s ones

  12. Measurements on TCTW #4 Three modes clearly visible and Q values similar to Nicolo’s ones

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