Solar blind detector for operation in the 1 to 180 nanometer region. It is encased in a vacuum tight housing for vacuum operation. The Model 425 is ideal for measurements in the Extreme and Vacuum UV (EUV and VUV) where the solar blind feature eliminates potential interference from long wavelength ultraviolet and visible light. It may be operated in pulse-counting mode or DC. The CEM is also available with coatings like Cesium Iodide or Magnesium Fluoride to enhance response in different energy regions.