An electron emitter assembly and a method for adjusting a power level of an electron beam are provided. The electron emitter assembly includes a laser configured to emit a first light beam. The electron emitter assembly further includes a light-attenuating device configured to receive the first light beam and to attenuate the first light beam between a first light intensity and a second light intensity greater than the first light intensity. The electron emitter assembly further includes a photo-cathode configured to receive the first light beam from the light-attenuating device. The photo-cathode is further configured to emit a first electron beam having a first power level in response to receiving the first light beam having the first light intensity. The photo-cathode is further configured to emit a second electron beam having a second power level greater than the first power level in response to receiving the first light beam having the second light intensity. The electron emitter assembly further includes an anode configured to receive the first and second electrons beams from the photo-cathode.