A gas filled cathode ray tube produces bright flashes of light for a stroboscope.It has a cathode & anode,inner grid & outer grid.If the potential of the outer grid is increased the conduction starts & it can be stopped by removing the anode potential.
When the tube is ionized & start giving out flashes the capacitor C is discharged & heavy current drawn will reduce the anode potential and thereby stopping the flashing of light.In a mean time the ācā is recharged & wait for the next pulse to start the flashing again.