Methodical errors in measuring the field in an accelerator with HF quadrupole focusing

The method of field electric component calculation in the linear ion accelerator with the quadrupole focusing intended for the reduction of systematic errors, occuring in the course of accelerating and focusing electromagnetic field structure investigation by the small perturbed method, is suggested. Formulas for the determining of the resonator frequency detuningdependence in quadrupole gap geometrical centre on the disturbing body radius are derived. It is shown, that using these formulas allows to reduce the systematic error to the random level. Thus, when using a disturbing body with 6-8 mm diameter the maximum measurement error does not exceed 1.5%