  The CLIC study of a high-energy (0.5 - 5 TeV), high-luminosity (1034 - 1035
cm-2 sec-1) e+e- linear collider is presented. Beam acceleration using high
frequency (30 GHz) normal-conducting structures operating at high accelerating
fields (150 MV/m) significantly reduces the length and, in consequence, the
cost of the linac. Using parameters derived from general scaling laws for
linear colliders, the beam stability is shown to be similar to lower frequency
designs in spite of the strong wake-field dependency on frequency. A new
cost-effective and efficient drive beam generation scheme for RF power
production by the so-called "Two-Beam Acceleration" method is described. It
uses a thermionic gun and a fully-loaded normal-conducting linac operating at
low frequency (937 MHz) to generate and accelerate the drive beam bunches, and
RF multiplication by funnelling in compressor rings to produce the desired
bunch structure. Recent 30 GHz hardware developments and CLIC Test Facility
(CTF) results are described.
