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High Q

Transverse Modes in SLAC Collimator. High R/ Q_t. High Q. Only the lowest two transverse modes have stronger R/ Q_t and are harmful to the beam. Lower Transverse Modes in SLAC Collimator. SLAC collimator with larger EM foils without support rods.

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High Q

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  1. Transverse Modes in SLAC Collimator High R/Q_t High Q Only the lowest two transverse modes have stronger R/Q_t and are harmful to the beam. Liling Xiao, Oct.6,2011

  2. Lower Transverse Modes in SLAC Collimator SLAC collimator with larger EM foils without support rods F=80.485, Q0=260, R/Q_t=9.4e5Ω/structure F=202.29, Q0=488, F=347.088, Q0=676 R/Q_t=2.2e4Ω/structure F=390.097, Q0=1732 F=432.470, Q0=1495 F=495.699, Q0=854 F=515.148, Q0=1580 F=559.633, Q0=2270 F=592.400, Q0=1994 The lowest two transverse modes have stronger EM fields in between the two jaws. 2 F=622.405, Q0=917 Liling Xiao, Oct.6,2011

  3. Higher Q Transverse Modes in SLAC Collimator SLAC collimator with larger EM foils without support rods F=1.303GHz, Q0=6405, R/Q_t=3.6e-2Ω/structure F=1.805GHz, Q0=7574, R/Q_t=6.6Ω/structure F=1.907GHz, Q0=9334, R/Q_t=9.4Ω/structure Higher Q transverse modes have EM fields have very lower R/Q_t. They might be hard to be measured. Liling Xiao, Oct.6,2011

  4. Some Observations • Below 2GHz, there are 90 transverse modes from the simulations and 52 modes from the measurements. The measured Q-values are lower than the simulated results. • However, the most dangerous transverse modes are found in the measurements and the measured results agree well with the simulations. • The possible reasons that cause the differences between the simulations and measurements might be: • The missing modes in the measurements are higher Q modes that have smaller R/Q_ts. Therefore, they are hard to be excited by the loop. • The real material (copper jaws or stainless steel tank) conductivity is larger than the one used in the simulations, thus the measured Qs are lower than the simulations. • The simulation model omits some mechanical parts , therefore the simulated Qs are higher than the measured results. Liling Xiao, Oct.6,2011

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