Neutron irradiation test of the fine pixel CCD vertex detector for the ILC

The Fine Pixel CCD (FPCCD) is one of the candidate vertex detectors for the ILC. We performed neutron irradiation test of the FPCCD with CYRIC proton beam line at Tohoku University. After the irradiation of 19-year neutron fluence at the 500 GeV high luminosity ILC, the performance of the FPCCD was tested. The dark current increased but was still three order of magnitude smaller than signal charge. The fraction of hot pixels increased to 1.2 × 10⁻⁵ which is enough small for operation. Charge transfer inefficiencies for horizontal and vertical directions were measured to be 3.49 × 10⁻⁵ and 6.34 × 10⁻⁵, respectively. Even for the farthest pixel from a readout channel, 63% of signal remains after the transfer. We conclude that neutron fluence at the 500 GeV high luminosity ILC is not a problem for the FPCCD.