Dipole stabilizers for a four-vane high current RFQ : Theoretical analysis and experimental results on a real-scale model

The Dipole Stabilizing Rods (DSRs) are devices used in order to reduce a priori the effect of perturbation on the operating mode of a four-vane RFQ caused by neighboring dipole modes by increasing the frequency spacing between the TE210 mode and dipole modes, without, in principle, affecting the quadrupole TE210 mode. They have proven to be particularly useful in the case of coupled RFQ's whose overall length is significantly greater than the operating wavelength. In this article we present a circuit model of such DSRs, that, used in combination with a Transmission Line Model of a four vane RFQ, has allowed us to predict the dimensioning of the DSRs in the case of the aluminium model of TRASCO RFQ. The DSR parameters and, in general, the accuracy of the model have been also confirmed by HFSS simulations and by RF measurements on the above-mentioned model.