The production of radioisotope 18F, which is used in early cancer diagnostic by Positron Emission Tomography and Computed Tomography (PET/CT), based on compound nuclear reaction 18O(p, n)18F. This radioisotope is produced mainly from cyclotron with low energy of proton beam from 8 to 20MeV. The negative ions H- , which are produced from ion source, are accelerated by electric field at accelerated gap. The energy of H- increase with each turn and reach fixed energy depend on type of cyclotron. After that, negative ion H- goes through carbon foil and lose 2 electrons in order to create positive H+ . Magnetic field control the movement direction of ion H+ to water target H2O18, in which nuclear reaction create radioisotope 18F. This report present in theory of some physical parameters, which are related to production capability of radioisotope 18F such as the cross section of nuclear reaction depend on energy of beam, the attenuation of beam when ion go through the material before contact with water target, the effect of cooling system, the target system,.. The report also present experimental results in order to estimate the production capability of 18F of HIC-KOTRON13 based on the value of Ysat about 94mCi/µA at beam current on target 43µA. With this value, the operators of HIC-KOTRON13 can estimate the time to produce radioisotope 18F with the order from hospitals