RF Field Measurement and Its Analysis on a Model Resonator of the Interdigital H Type Linac

RF field measurement and its analysis have been made on a model resonator of the interdigital H (IH) type linac in order to study the feasibility of the IH type as the injector linac for the NUMATRON. The measurement shows that the inductance of the resonator is dominated by the cross sectional area. It also shows that the capacitance is concentrated near the drift tubes and agrees with the one measured electrostatically. The resonant frequencies are well explained with an equivalent circuit analysis based upon the field distribution measurement. Electrostatic capacitance has been measured on the models of the drift tubes with quadrupole magnets for the velocity range of ß = 2 - 16 %. The effective shunt impedance has-been calculated by using the electrostatically measured capacitance. The result is 150 - 70 M ¿/m for ß= 2 - 6 %, which is two times higher than that of Wideröe type, 65 - 40 M ¿/m for ß = 6 - 10 %, which is 1.5 times higher than that of Alvarez type.