Abstract: An apparatus provides in-situ radiation treating utilizing a miniature energy transducer to produce x-rays, wherein the energy transducer includes a Schottky cathode tip. More specifically, the energy transducer includes a transducer body, an anode provided at a first end of the transducer body, and a cathode provided at a second end of the transducer body opposite the anode. The energy transducer is coupled to an energy source by a flexible insertion device. The energy source provides electrical and/or light signals to the energy transducer via the flexible insertion device. Light transmitted from the energy source to the energy transducer by the flexible insertion device is focused on a Schottky cathode tip of the cathode by the optical fiber provided in the hollow core of the anode.