 An incoming electron is accelerated to the wall, where it removes more electrons, in such a way that an electron avalanche is created, until a measurable current pulse is obtained.In laboratory systems, either 10-30 mm beam diameter non-monochromatic Al Kα or Mg Kα anode radiation is used, or a focused 20-500 micrometer diameter beam single wavelength Al Kα monochromatised radiation.Monochromatic Al Kα X-rays are normally produced by diffracting and focusing a beam of non-monochromatic X-rays off of a thin disc of natural, crystalline quartz with a <1010> orientation.