Abstract: CLIC (Compact LInear Collider) is an electron-positron collider with 3 TeV center of mass energy and at the moment is in feasibility study stage. CTF3 (CLIC Test Facility 3) was started to build to demonstrate the main issues of CLIC and will be finished at 2011. The main beam accelerator of CLIC is a RF electron (positron) linear accelerator which requires a high power RF source (â??400 MW/m) with high frequency (12 GHz) to produce a high field gradient of about 100 MV/m. With normal power sources (klystrons and magnetrons) this requirement is not achievable or very difficult and expensive then another RF accelerator with three rings is used to produce drive beam with high current (101 A) and 12 GHz repetition frequency and 2.37 GeV energy. Later this drive beam is decelerated in PETS (Power Extraction and Transfer Structures) to 237 MeV to produce RF electromagnetic waves as a source for main beam accelerator. This high current and repetition frequency is achievable by bunch interleaving method in drive beam complex rings. Recent experiments in CTF3 show the feasibility of this method. In this lecture this method and recent data will be introduced.