cesium telluride (Cs2Te) is a highly efficient photocathode with a high quantum efficiency. It is used as an electron source in free-electron lasers and other accelerators.
Quantum Efficiency: QE is defined as the number of electrons emitted for each unit photon. It is a very useful metric to characterize a photocathode’s performance.
Work Function: The work function of a photocathode is important for its performance as an electron source. It is a measurable property of the device which is directly related to the energy of the incident laser pulses and the number of electrons generated per pulse.
Rejuvenation: The work function of a photocathode can be restored by heating the material to 150-200 degC. This is a time-consuming process and requires careful monitoring of the temperature of the device.
Vapourization of Cs2Te: Knudsen-cell mass spectrometry has been used to study the vapourization of Cs2Te in an operating CANDU reactor and in a loss of coolant accident (LOCA). The results show that the vapourization process proceeds incongruently, resulting in the release of different vapour-phase species with increasing atomic concentrations of elemental tellurium.
Codeposited CsTe: Real-time in situ x-ray techniques including XRF, XRD and XRR have been used to examine the growth of a codeposited CsTe photocathode. The codeposited cathode exhibits higher quantum efficiency (19% at 266 nm) than the sequentially grown one and has a smoother surface with a roughness of about
The work function of the sequentially deposited and codeposited photocathodes were examined in a fabrication chamber before and after exposure to air. The QE of the sequentially deposited Cs2Te dropped dramatically after air exposure, while the codeposited Cs2Te returned to its original state with about 20% of the QE before air exposure.
