The theory of the ion-ripple laser, which consists of a relativistic e
lectron beam obliquely travelling through an ion ripple, has been exte
nded to include the partial dielectric guiding effects. When the beam
electron current I greater-than-or-equal-to 2 kA it is found that cohe
rent radiation of any high frequency may be guided and localized by th
e partial dielectric waveguide.