Status of the modulated 3 MeV 325 MHz Ladder-RFQ

Based on the positive results of the unmodulated 325 MHz Ladder-RFQ from 2013 to 2016, a modulated 3.3 m Ladder-RFQ is currently under construction and will be tested with beam at GSI FAIR, Darmstadt. The unmodulated Ladder-RFQ showed a very constant voltage along the axis. It could withstand more than 3 times the operating power of which is needed in operation at a pulse length of 200 µs. That corresponds to a Kilpatrick factor of 3. The 325 MHz RFQ is designed to accelerate protons from 95 keV to 3.0 MeV according to the design parameters of the p-linac at FAIR. This particularly high frequency for a 4-Rod type RFQ creates difficulties, which are challenging in developing an adequate cavity. The results of the unmodulated prototype have shown, that the Ladder-RFQ is a suitable candidate for that frequency. Inspired by the successful RF power test, the nominal vane-vane voltage was increased from 80 kV to 96 kV. The basic design and tendering of the RFQ has been successfully completed in 2016. Electrodynamic simulations of a modulated full structure, especially in terms of field-flatness and frequency tuning, are shown. Furthermore, the mechanical design, which includes a direct cooling of the structure for duty cycles up to about 5%, will be discussed.