We derive a theory of the Raman regime ion-ripple laser in a plasma wa
veguide, which consists of a relativistic electron beam obliquely prop
agating through an ion-ripple channel surrounded by a plasma cladding.
When the beam electron current I(b) greater-than-or-equal-to 2 kA, th
e plasma waveguide may guide the radiation of any high frequency and e
nhance the growth rate.