VHF Photocathode Electron Gun
We are developing a design for a high-brightness, high-repetition rate electron gun that uses a normal conducting RF structure in the VHF range, between 50 to 100 MHz. The gun cavity has quarter-wave coaxial geometry, which is a mature RF technology similar, for example, to that employed in the NSLS VUV ring accelerating cavities. The lower frequency results in a larger cavity compared to the more common designs operating at ~1 to ~3 GHz. A significant benefit of using a larger cavity is a dramatic reduction of the power density on the cavity walls, which allows CW operation of the gun, and thus a bunch repetition rate of up to the RF frequency (dependent on photocathode-laser time structure). Calculations show that a VHF gun can achieve accelerating gradient at the cathode of approximately 20 MVm-1. Table 1 shows example parameters for a VHF photocathode cavity.
TABLE 1
Example parameters for a VHF coaxial cavity
