Comparison of 352 MHZ structures for injection into an ion therapy accelerator

In the frame of ongoing initiatives for the design of a new generation of synchrotron-based accelerators for can-cer therapy with ion beams, an analysis of linac designs has been started, to address a critical element with a strong im-pact on the performance and cost of the accelerator. The goal is to identify alternatives at lower cost and a similar or possibly smaller footprint than the standard 217 MHz in-jector presently used in all carbon therapy facilities in Eu-rope. As an additional feature, a new linac design can be tailored to produce radioisotopes for treatment and diag-nostics in parallel with operation as a synchrotron injector. In this paper, the attractive option of moving to 352 MHz frequency is analyzed, to a profit of reliable mechanical de-signs already developed for protons and of the cost savings that can be obtained using Radiofrequency (RF) power sources klystrons with a much lower cost per Watt than tubes or solid-state units. The paper is presenting a Quasi-Alvarez Drift Tube Linac (QA-DTL) version of an injector linac for carbon ions at q/A=1/3 and compare it with Inter-Digital H-Mode DTL (IH-DTL) designs. The option of a Separated-tank IH-DTL structure (S-IH-DTL) is also dis-cussed, along with a standard IH-DTL, both at 352 MHz. Finally, a DTL design at 352 MHz for the injection of fully stripped helium ions into the synchrotron is presented.