The development of mono energetic photon sources using $K_{alpha}$ fluorescence X-ray of pure material was carried out in the energy range below 100 keV. The monoenergetic photons are very useful in the calibration of the radiation measuring instruments and can be produced as the $K_{alpha}$ fluorescence X-ray by irradiating the bremsstrahlung to the thin pure metal foils called ‘radiators’. In this experiment, several radiators such as $_{47}Ag,;_{50}Sn,;_{68}Er,;_{70}Yb,;and;_{82}Pb$ provide the wide monoenergetic photon energy ranging from 20 keV to 80 keV. By the spectrometry with HpGe LEPS, spectral purity factors which measure the monochrometicity for the $K_{alpha}$ fluorescence X-ray, were determined as $0.64{sim}0.94$. Dosimetry for the purpose of the determination of the exposure rate with a 600cc thin window ionization chamber, which was calibrated by the standard free-air ionization chamber, was performed. Exposure rates ranging $8.3{sim}232.5mR/h$ was obtained according to the $K_{alpha}$ fluorescence X-ray energy for each radiator.