In order to find a simple and higher accuracy approach to estimate the vacuum state in a vacuum interrupter

a method utilizing X-ray variation without exerting outer magnetic field was presented.The Field emission electrons escape from cathode surface at very high speed and bombard the anode when the vacuum interrupter is under power frequency voltage wiht a designated gap length.Based on the bremsstrahlung principle

the X-ray is released from the anode surface with varying intensities due to different vacuum states.The relationship between vacuum and X-ray intensity is derived and verified with test results.