TY - GEN
T1 - Improvement of the Q factor measurement in RF cavities
AU - Xu, Wencan
AU - Belomestnykh, S.
AU - Ben-Zvi, I.
AU - Hahn, H.
PY - 2013
Y1 - 2013
N2 - The Q values of Higher Order Modes (HOMs) in RF cavities are usually calculated from the resonance bandwidth measured at -3 dB level by a network analyzer. The resonant curve distortion is caused by the resonance split due to the ellipticity caused by manufacturing tolerances, and RF ports. Therefore, the measured Q values are usually lower than the simulated or theoretical Q values. In some cases, only one mode's Q can be measured with the -3 dB method. There may be two reasons for this. One is that one mode is excited strongly, while the neighboring split-mode is close to 90 polarized and thus excited weakly; the other reason is that the resonant curve of one mode was distorted by the other mode too much to measure the -3 dB level. In this paper, we resolve this issue by looking into the RF measurement setup, including cavity, input coupler and pick-up coupler, from the equivalent circuit and wave point of view. Using HOM data for a copper prototype of the BNL3 cavity, we compare the results from measurements and simulations.
AB - The Q values of Higher Order Modes (HOMs) in RF cavities are usually calculated from the resonance bandwidth measured at -3 dB level by a network analyzer. The resonant curve distortion is caused by the resonance split due to the ellipticity caused by manufacturing tolerances, and RF ports. Therefore, the measured Q values are usually lower than the simulated or theoretical Q values. In some cases, only one mode's Q can be measured with the -3 dB method. There may be two reasons for this. One is that one mode is excited strongly, while the neighboring split-mode is close to 90 polarized and thus excited weakly; the other reason is that the resonant curve of one mode was distorted by the other mode too much to measure the -3 dB level. In this paper, we resolve this issue by looking into the RF measurement setup, including cavity, input coupler and pick-up coupler, from the equivalent circuit and wave point of view. Using HOM data for a copper prototype of the BNL3 cavity, we compare the results from measurements and simulations.
UR - https://www.scopus.com/pages/publications/84890593926
M3 - Conference contribution
AN - SCOPUS:84890593926
SN - 9783954501229
T3 - IPAC 2013: Proceedings of the 4th International Particle Accelerator Conference
SP - 2489
EP - 2491
BT - IPAC 2013
T2 - 4th International Particle Accelerator Conference, IPAC 2013
Y2 - 12 May 2013 through 17 May 2013
ER -