High-frequency linear accelerators (linacs) are devices that accelerate charged particles using electromagnetic fields oscillating at high frequencies, typically within the radio frequency (RF) range. Their ability to accelerate various particles to a range of energies over relatively short distances, combined with their compact design, makes them suitable for a wide array of scientific, industrial, and medical applications.
The NIMMS group at CERN is conducting exploratory research to design an efficient and cost-effective linac for a medical accelerator complex intended for particle therapy and scientific research. This linac is primarily envisioned as a carbon and helium ion injector (A/q = 1/2) for a compact synchrotron used in patient treatment. Additionally, a second implementation will focus on helium and proton acceleration at higher energies to enable radioisotope production for Targeted-Alpha-Therapy (TAT) and diagnostic purposes.
NIMMS developed two LINAC injectors for therapy synchrotrons, one designed for carbon ions and the other for helium ions. Both designs can produce radioisotopes at energies of 20 MeV, 28 MeV or 40 MeV with alpha particles. Each LINAC is made of three sections. Depending on the chosen LINAC the first section will differ since it is developed to accelerate designed ions up to the corresponding optimal injection energy in the synchrotron. It is composed of an RFQ and an accelerating section. The second and third sections are required only to exploit the beam pre-accelerated in section 1 for the production of radioisotopes for imagining and therapy that can be used in a program of research in parallel with the main ion therapy plan. The beam pulses that go to the synchrotron, generated at the low repetition frequency imposed by the slow pulsing synchrotron, will be transported through the unpowered and detuned structures of sections 2 and 3 before injection into the ring. All other pulses – generated by the proton source - can go through all sections and be accelerated at the required energies to produce isotopes in a target placed on a straight line after the LINAC. The energy of section 2 has been defined to reach the optimum energy for the production of Astatine-211, one of the most promising alpha-emitter for targeted cancer therapy.
LINAC's for Radioisotope Production
Besides Astatine-211, both LINAC designs can be used for the production of a huge variety of radioisotopes used in PET (Positron Emission Tomography) and SPECT (Single Photon Emission Computed Tomography) for patient imaging processes, or in 
- therapy and TAT (Targeted Alpha Therapy) for patient cancer treatment. Some of the most frequently used radioisotopes nowadays and their primary usage, which can be produced with both LINAC designs developed by NIMMS, are shown in Table 1.
Table 1. The most frequently used radioisotopes produced with LINACs developed by NIMMS.
LINAC's for Synchrotron Injection
....