Study on Interdigital H-Type Structure for Heavy-Ion Linear Accelerator

Due to the very low heavy-ion velocity at injection, the frequency must also be kept low enough and it turns out that Alvarez and twin-line structures become inefficient. Experimental works were carried out at Lyon on a new type of structures well suited for low velocity range, namely the interdigital H-type structure. The dimensions of this type of structure as well as their electrical characteristics proveto be very attractive at low frequency; furthermore, due to the particular field pattern in these resonators, radial focusing of the beam appears to be possible with magnetic quadrupoles at energy as low as 50-60 keV/nucleon and frequency in the range of 20-30 MHz. Such a field pattern also gives good acceptances for the whole cavity. This paper presents our last results, discusses various problems and gives the main parameters of Lyon´s 10 MeV/nucleon heavy-ionliner accelerator project.