  We present a new scheme of compact Rubidium cold-atom clock which performs
the diffuse light cooling, the microwave interrogation and the detection of the
clock signal in a cylindrical microwave cavity. The diffuse light is produced
by the reflection of the laser light at the inner surface of the microwave
cavity. The pattern of injected laser beams is specially designed to make most
of the cold atoms accumulate in the center of the microwave cavity. The
microwave interrogation of cold atoms in the cavity leads to Ramsey fringes
whose line-width is 24.5 Hz and the contrast of 95.6% when the free evolution
time is 20 ms. The frequency stability of $7.3\times10^{-13}\tau^{-1/2}$ has
been achieved recently. The scheme of this physical package can largely reduce
the complexity of the cold atom clock, and increase the performance of the
clock.
