Feedthrough Simulations

• The results of the RF measurements showed that the external Q of the BPM was much higher than anticipated.
• A study was done to reduce the Q factor and return the Q to its goal value of 500.

Position Cavity RF Measurement

• Results from RF measurement

• Effect of removing seals, i.e. the antennae protrude 0.45 mm further into the waveguides.

• The external Q has reduced to a value closer to the expected number.
• However, the loaded Q is too small, caused by a low internal Q.

Position Cavity Simulation

• The effect of the antenna length on the Q was studied in simulation.

• Removing the seals means the antenna separation changes by -0.45 mm, decreasing the overall Q.
• Comparing the simulated and measured Q's, the measured value was 444 and the simulated was 343.
• The separation change that gives a loaded Q of ~500 is about -0.15 mm.

Reference Cavity Simulation

• The above simulations were performed for the reference cavity