Dempster mass spectrograph is a semicircular tube through which positive rays of the element are produced by heating a suitable salt of the element electrically and bombarding the vapours with electrons. The positive particles thus produced aare passed through a silt between two plates where it is exposed to an electric field to accelerate particles from the salt element. After exiting the two plates it passes through a magnetic field in the middle of the tube. From here the particles are passed to another silt at the opposite end and towards the electrometer to measure the ion current.
