A RF accelerator system includes an accelerator, a RF source coupled to the accelerator for providing RF power to the accelerator, a control for adjusting a frequency of the RF power provided by the RF source through a frequency range, and a sensor for sensing a response resulted from an operation of the accelerator based at least in part on the adjusted frequency of the RF power through the frequency range. A method of diagnosing a RF spectrum in an accelerator system includes providing RF power to an accelerator, adjusting a frequency of the RF power through a frequency range, and sensing a response resulted from an operation of the accelerator, the response being based at least in part on the adjusted frequency of the RF power through the frequency range.