Precise energy measurement of the continuous proton beam

The method and the results of the proton beam energy measurements carried out on the INR (Institute for Nuclear Research) linac injection line are described. The measurements are made by a two-cavity buncher. The first cavity is used for beam bunching, and the second one serves as a beam harmonic detector. To find a particle energy distribution, the phase difference of the RF fields in the two cavities is measured. To measure the absolute value of beam energy, a mechanical movement of the second cavity is used. A cavity displacement corresponds to a 2 π phase shift of the induced field. Random errors of absolute energy measurement are due mainly to energy instability, and the values are in the range (1/4)×10^-3 depending on the experimental condition. There is a systematic error because of a beam energy drift while moving the cavity. This value was 2×10^-3 when special care was taken to decrease energy drift. The accuracy of the energy distribution measurements was about 10^-4