  Fine pixel CCD (FPCCD) is one of the candidate sensor technologies for the
vertex detector used for experiments at the International Linear Collider
(ILC). FPCCD vertex detector is supposed to be cooled down to -40 degree for
improvement of radiation immunity. For this purpose, a two-phase CO2 cooling
system using a gas compressor for CO2 circulation is being developed at KEK.
The status of this R&D is presented in this article.
