  The new method to stabilize the beam energy of the KEK 40MeV proton linac, is
developed now. In this method, the signal of the velocity monitor installed
upstream the debuncher in the 40MeV beam line, is processed and then fed to the
phase shifter of the debuncher rf system so as to cancel the fluctuation of the
beam energy. In this article, the beam tests to prove the validity of this
method and the system are described.
