Abstract
With the growing demand from scientific projects such as the X-ray free electron laser (XFEL), ultrafast electron diffraction/microscopy (UED/UEM) and electron ion collider (EIC), the semiconductor photocathode, which is a key technique for a high brightness electron source, has been widely studied in China. Several fabrication systems have been designed and constructed in different institutes and the vacuum of most systems is in the low 10−8 Pa level to grow a high QE and long lifetime photocathode. The QE, dark lifetime/bunch lifetime, spectral response and QE map of photocathodes with different kinds of materials, such as bialkali (K2CsSb, K2NaSb, etc.), Cs2Te and GaAs, have been investigated. These photocathodes will be used to deliver electron beams in a high voltage DC gun, a normal conducting RF gun, and an SRF gun. The emission physics of the semiconductor photocathode and intrinsic emittance reduction are also studied.
Highlights
Many scientific projects such as a high repetition rate X-ray free electron laser (XFEL) [1,2,3], electron-ion collider (EIC) [4], ultrafast electron diffraction/microscopy (UED/UEM) [5,6,7], etc., are being built or proposed in China
At SARI [53], the researcher gave a special view on the emission process of K2 CsSb photocathode as shown in Figure 12: the electron bunch is divided by “electron slice” inside the cathode material, which separately contributes to the intrinsic emittance, just as the slice emittance contributes to the final emittance [71]
These results show that part of the emittance growth is caused by plasQE offield the (PNF)
Summary
Many scientific projects such as a high repetition rate XFEL [1,2,3], electron-ion collider (EIC) [4], ultrafast electron diffraction/microscopy (UED/UEM) [5,6,7], etc., are being built or proposed in China. In these big projects, the demand for a high-performance photocathode has become more crucial and urgent, especially for a semiconductor photocathode [8]. The cathode performance in guns and the study of emission physics are included
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