The ''v(p) x B'' effect is introduced into a traveling wave amplifier
trying to increase its output power arid efficiency. The numerical cal
culating results show that by introducing an tapered static magnetic f
ield into a traditional traveling wave amplifier, its output power and
efficiency can be increased obviously comparing with an ordinary trav
eling wave ampilfier, because of the effective interactive duration of
electron bunches and a rf field is extended by the ''v(p) x B'' effec
t.