The Bevatron requires an intense source of high‐energy protons. The machine should accept monoenergetic protons for a duration of approximately 500 microseconds once every 6 seconds. To satisfy the requirements of small loss due to scattering by the gas in the accelerating chamber, a 9.9‐Mev linear accelerator has been built and operated.A 500‐kilovolt Cockcroft‐Walton generator is used to inject 3‐ma peak proton current into the linear accelerator. Focusing grids intercept approximately half of the injected beam. Additional losses, including radial defocusing and acceptance phase angle, result in a peak accelerated beam of 225 microamperes. The energy spread of the accelerated protons has not been measured, but an upper limit is less than ±30 kev.