SCDTL 7-71 MeV

SCDTL is the most innovative part of the TOP IMPLART accelerator.

It is composed of two groups of fours accelerating structures each:

· SCDTL-1

· SCDTL-2

· SCDTL-3

· SCDTL-4

· SCDTL-5

· SCDTL-6

· SCDTL-7

· SCDTL-8

· PMQ

SCDTL (Side Coupled Drift Tube Linac) structure substitutes the commonly used CCL (Coupled Cavity linac) in the intermediate energy part of the protontherapy Linac. It has been chosen for its higher efficiency the low-velocity part of the Linac. It can be used up to 65-70 MeV, but it is really irreplaceable below say 30 MeV. After, it is a matter of convenience, balancing the decision between lower power needed (SCDTL) r more compact linac (CCL).

It is composed by a sequence of small Drift Tube Alvarez tanks coupled by side coupling cavities, and with Permanent Magnet Quadrupoles placed on axis in the intertank space arranged in FODO lattice.

SCDTL was patented by ENEA in 1995. SCDTL theory was widely studied all throughout these years and several prototypes and models were constructed, tested and, some, operated at high power and/or with particles.

In general SCDTL was conceived in the ‘90s along the mainstream of low energy proton linear accelerator structure development, like the similar CCDTL or SDTL structures, but the originality of the structure is mainly in the operating frequency, 3 GHz, never used before it for proton acceleration. It is the application to protontherapy, indeed, where accelerated current is very low, that made it possible a miniaturization of the structure, while CCDTL and SDTL were developed for high current proton linacs for spallation neutron production.

Several mechanical solutions were tried for a successful and reliable construction.

The SCDTL shunt impedance and therefore the efficiency is considerably larger than common Coupled Cavity linac structures for proton energies below 60 MeV