Progress of the modulated 325 MHz Ladder RFQ

Abstract

Based on the positive results of the unmodulated 325 MHz Ladder-RFQ prototype from 2013 to 2016 [1], we developed and designed a modulated 3.3 m Ladder-RFQ. The idea of the Ladder type RFQ firstly came up in the late eighties [2, 3] and was realized successfully for the CERN Linac3 operating at 101 MHz [4] and for the CERN antiproton decelerator ASACUSA at 202 MHz [5].The unmodulated Ladder-RFQ features a very constant voltage along the axis. The RFQ was high power tested at the GSI test stand [6]. It accepted 3 times the RF power level needed in operation [7]. The highest level corresponds to a Kilpatrick factor of 3.1 with a pulse length of 200 μs. The 325 MHz RFQ is designed to accelerate protons from 95keV to 3.0 MeV according to the design parameters of the proton linac within the FAIR project. This particular high frequency creates difficulties for a 4-ROD type RFQ, which triggered the development of a Ladder RFQ with its higher symmetry. The results of the unmodulated prototype have shown, that the Ladder-RFQ is a suitable candidate for that frequency. For the present design duty cycles are feasible up to 5%. The basic design and tendering of the RFQ has been successfully completed in 2016 [8]. Manufacturing will be completed until May 2018. In this paper we present the latest results of manufacturing and beam dynamics simulations for the matching between LEBT and RFQ.