We customized a laser calibration system and four
radioactive γ-ray calibration sources for the Jiangmen
Underground Neutrino Observatory (JUNO), a 20-kton liquid
scintillator-based neutrino detector. The laser source system was
updated to realize the isotropic light emission timing within
±0.25 nsec level and to allow the tuning of the laser intensity
covering more than four orders of magnitude. In addition, methods
to prepare four different radioactive sources (18F,
40K, 226Ra, and 241Am), covering
energies from 0 (10) keV to
0 (1) MeV, for the JUNO
detector were established in this study. The radioactivity of each
source and the risk of radioactive substance leaking into the
detector from the source were confirmed to meet the experimental
requirements.