Results of the IPHI drift tube linac's hot model cw tests

In the course of the IPHI project (high intensity, cw proton injector), a drift tube linac hot model has been built and tested. The main difficulty associated with these machines is the high RF thermal losses inducing significant heating and deformations if not kept under strict control. Therefore the hot model has been tested under nominal RF conditions (40 kW cw for an accelerating field of 1.75 MV/m) to verify the suitability of the technical choices made: materials, mechanical designs, construction techniques, vacuum... This prototype includes four accelerating cells, three full drift tubes, two of which enclose a quadrupole electromagnet. Results show that a stainless steel envelope can be used even at these high power densities, provided that it is copper plated both inside and outside to enhance its thermal conductivity and lower the temperature gradients. This solution leads to a cheap and reliable machine. The new kind of drift tube/magnet assembly tested in this DTL model ("flooded drift tube"), where the whole drift tube is filled with water cooling simultaneously the magnet leads and the drift tube walls, is also a suitable solution, cheap and more efficient than the usual ones. With the successful tests of this hot model, one more step has been made towards a cw drift tube linac for high intensity light ions accelerators.