For the confirmation of effectiveness of external neutron source experimentally, Accelerator Driven System (ADS) experiments coupled with FFAG proton accelerator and Kyoto University Critical Assembly as a subcritical system were conducted at February, 2011. By foil activation method with Gold/Indium wires and foils after neutron irradiation at three different external neutron source positions, the variation of neutron multiplication was compared at active core region. The neutron flux increment by 164% and 143% were confirmed when tungsten foils as external source were close to close. © Springer 2012.