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In this paper, explained the process of calculation and design of cyclotron proton accelerator cavity and effects of cavity’s fundamental parts for tuning the frequency to produce radioactive isotope FDG (FluoroDeoxyGlucose) using in PET imaging system. Rf cavity in 71 MHz resonant frequency is designed to accelerate the ions with an energy output of 10 MeV. It should be small cyclotron to be installed in hospitals to produce FDG. System design process with high quality factor and small size, require to optimize the different parts of RF system. The optimization of this system have been done at frequency of 71 MHz by HFSS and CST software and compared with each other. And also the thermal consideration are examined. Introduction Most numerous of circular accelerators, cyclotrons are characterized by magnetic field and accelerating RF frequency which are constant in time. The Dees are driven by an RF voltage whose frequency matches the constant cyclotron frequency f =qB/2πm of non-relativistic ions. Ions from a central ion source are repetitively accelerated in and out of the Dees on a spiral path to maximum energy. In practice, the magnetic field must decrease with r to assure stability in the axial direction, and the accelerating voltage must be high for ions to reach the design energy before they get out of the accelerating phase of the RF cycle. Ions from a central ion source are repetitively accelerated in and out of the Dees on a spiral path to maximum energy. In practice, the magnetic field must decrease with r to assure stability in the axial direction, and the accelerating voltage must be high for ions to reach the design energy. Large energy gain per turn and change of voltage values with energy, during the passage of the four gap in each round will be earn for 60 or 80 round as follow; ∆T=(10MeV-30keV)/(4×60{80}) = 41514.6{31156.25} V=∆T/(τ sin(hα/2) sinφ) = 42.36kV {31.8kV} The maximum electric field achievable is limited by a process known as RF breakdown which is known as the Kilpatrick Limit. frf=1.64E2ke-8.5/Ek According to our RF frequency, 71MHz, Kilpatrick limit will be; Ek = 10.05 MV/m And so Es as the maximum surface electric field level is obtained as follows; Es=15.075 MV/m Therefore, The minimum distance between Dee and Liner to prevent electric spark will be; dmin =3.316mm Calculate the Stem Dimension Total Stems length is considered λ/2. So due to the design frequency it will be calculated. Also, the set of Stem and Liner will be considered as a coaxial cable with the desired impedance. So diameter of Stems could be determined by this approach. In the fact, Stem plays the role of inner conductor and the Liner as an outer conductor. This means that for a 50ohm specific impedance, the Liner to Stem diameter should be equal to 2/3. Hence, Stem diameter was estimated with this phrase. Liner diameter, size of the magnet and valley dimension are related to each other . This research, explain the process of calculation and design of H- ion accelerator cyclotron cavity to produce radioactive isotope FDG using in PET imaging system. H- ion in 71MHz resonant frequency of the cavity is designed to accelerate the ions with an 10 Mev energy. Calculate the Dee Dimension Particle should obtain energy equal to10MeV during the 60 to 80 revolution. As a sample, for 80 revolution, Dee angle will be calculated accurately as follow. The obtained particle energy through the four Gap is: E=4q VDee Sin( h/2 θDee), h=4 The energy gained by the particle in each round: 10Mv/80=125000=4 VDee Sin( h/2 θDee) If VDee =50kV Sin(2 θDee)=0.625 2 θDee =79.32 θDee =39.66° And also, for 60 revolution, the energy gained by the particle in each round: 10Mv/60=166.6kv =4q VDee Sin( 2 θDee)= 166666.6 If VDee =50kv Sin(2 θDee)=0.833 2 θDee =56.4 θDee =28.2° And if VDee =42kv Sin(2 θDee)=0.992 2 θDee =82.74 θDee =41.3° Conclusion This paper explain the general principles of the cyclotron accelerator RF system and specially consider the Dee angle and Stem-Liner distance effect to achieve desired energy, 10MeV. The results illustrate that the RF power transmit with minimum loss. Specifications of system Therefore, in our design θDee should be about 40° for VDee about 40kV . 1