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Background: Iodine-123 (123I) is regarded as one of the best radionuclides for in vivo medical studies using single-photon emission computed tomography (SPECT) due to its suitable physical property. Materials and Methods: To design a new system in order to replace cryogenically solidified xenon target by the gas one, some necessary calculations are needed to be done such as finding the excitation functions variation of the production reactions, thick target yield of 123I production, etc. The computer codes Alice91 and SRIM have been used as a calculation tools. Results: According to the suggested design, a conical shaped irradiation vessel made of copper with thickness of 1mm, outlet diameter of 1 cm, 5 cm length and 12° angle at summit can be fixed inside a liquid nitrogen housing chamber. The 124Xe gas was sent to the inside of this very cold conical trap and eventually deposited on its surface in solid form. Calculation showed that during bombardment with 17- 28 MeV proton energy, the thickness of solidified xenon layer remained about 0.28 mm. Conclusion: The production yield of 123I can be predicted to be around 150 mCi/µAh.