Analysis and suppression of RF radiation from the PSI 590 MeV cyclotron Flat Top Cavity

Abstract

The Flat Top Cavity, located in the PSI HIPA Ring Cyclotron leaks RF power of several kilo Watts into the cyclotrons vacuum space causing several complications. A detailed electromagnetic model was created and simulations performed to analyze the mechanisms by which power is leaking out of the Flat Top Cavity. The tolerances needed to limit the leaked power in future iterations of the Flat Top cavity are reported. Comparison of the model to measurements are described as well as two potential methods to limit power leakage. These studies will have direct impact on future RF cavity designs for cyclotrons as power levels increase and higher RF fields are required.

Examination of the plasma located in PSI Ring Cyclotron

“…Once ignited though, the plasma changes the overall impedance of the cyclotron vacuum chamber and pulls additional power out of the cavity. Overall this provides consistent narrative and directs us to interventions to limit the leaked power from the FTC [10].…”

“…Interventions have been planned to suppress the plasma by attenuating the power leaked out of the cavity and are discussed in Pogue [10]. Additionally, elemental analysis using electron backscatter techniques will be performed on components when available to verify the elements being deposited are those being excited in the plasma.…”

“…Comparing the no plasma scenario to the ideal model, one can see a 2.4 kW difference exists, which happens to match the leaked power seen in the finite element model. Image from [10] show that approximately ∼5 kW of power at 500 kV is being pulled out of the cavity when the plasma is ignited.…”

“…The blue curve in Figure 11 is generated from a finite element model of the cavity based upon the CAD drawing of the FTC [10]. Interferometry measurements were made of the cavities interior and the dimensions of the FTC Finite element model were altered to reflect these findings.…”