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SR and FEL sources and centers

Study on secondary electron emission of a quarter wavelength coaxial cavity for triode type thermionic RF electron gun


  • Mr. Konstantin TORGASIN

Primary authors



Free Electron Lasers (FEL) require generation of electron beam of high quality. Some infrared FEL facilities apply thermionic RF guns due to their advantage of compactness and cost effectiveness as compared to RF photo-cathode electron guns. Other remarkable advantages are the long lifetime and moderate vacuum condition requirements. On the other hand, thermionic RF guns are suffering from back-bombardment phenomena, which limit the bunch charge and macro-pulse duration. In order to overcome this disadvantage a novel configuration named the triode type thermionic RF electron gun, which has an additional small pre-bunching cavity around the cathode, was developed at the Institute of Advanced Energy (IAE), Kyoto University. The triode concept has already been verified by numerical simulation. However, the tests of the prototype cavity have revealed the appearance of the secondary electron emission, which makes the operation of the cavity as a pre-buncher impossible. The objective of this study is the investigation of the origin of secondary electron emission and discussion of possible solution methods.