The AXUV63HS1 from Opto Diode Corporation is a circular photodiode with an active area of 63 sq. mm and sensitivity to electron energy levels as low as 100eV. It has a capacitance of under 85 pF, a reverse breakdown voltage of 160 volts and a rise time of 10 nsec. This photodiode operates over a temperature range from -10 °C to +40 °C in ambient environments and from -20 °C to +80 °C in nitrogen or vacuum environments. The device is shipped with a protective cover plate to protect the photodiode chip and wire bonds.