- R&D 100 Awards
A photocathode is photoemissive material that emits electrons when exposed to light or other radiation. It is used to convert incident light photons into electrons, a process called photoemission. It occurs in three steps: 1) the absorption of an incident photon and transfer of energy to an electron within the photoemissive material; 2) the migration of the electron to the surface; and 3) the escape of the electron from the photocathode surface. A typical acceleration region in most X-ray detectors consists of an anode and a cathode separated by a small gap. Electric fields as high as 10 kV/mm are typically used to accelerate electrons into the detector. Geometrically Enhanced Photocathodes have been designed to withstand high electric fields without field emission and with minimal introduction of temporal dispersion to the emitted electron distribution. Quantum efficiency of photocathodes has been stuck at 1 percent in the soft x-ray region. Geometrically Enhanced Photocathodes increase the measured total electron yield by up to three times in the 1–12 keV energy range.