CERN Accelerating science

Article
Title	Normal-Conducting High Current RF Photoinjector for High Power CW FEL
Author(s)	Kurennoy, Sergey ; Christina, Vincent ; Nguyen, Dinh C ; Rathke, John ; Schrage, Dale L ; Schultheiss, Tom ; Wood, Richard L ; Young, Lloyd M
Affiliation	(AES, Medford, NY) ; (AES, Princeton, New Jersey) ; (LANL, Los Alamos, New Mexico) ; (LANL/LANSCE, Los Alamos, New Mexico) ; (TechSource, Santa Fe, New Mexico)
Publication	2005
In:	21st IEEE Particle Accelerator Conference, Knoxville, TN, USA, 16 - 20 May 2005, pp.2866
Subject category	Accelerators and Storage Rings
Abstract	An RF photoinjector capable of producing high average current with low emittance and energy spread is a key enabling technology for high power CW FEL. The design of a 2.5-cell, pi-mode, 700-MHz normal-conducting RF photoinjector cavity with magnetic emittance compensation is completed. With average gradients of 7, 7, and 5 MV/m in its three accelerating cells, the photoinjector will produce a 2.5-MeV electron beam with 3-nC charge per bunch and transverse rms emittance below 7 mm-mrad. Electromagnetic modeling has been used extensively to optimize ridge-loaded tapered waveguides and RF couplers, and led to a new, improved coupler iris design. The results, combined with a thermal and stress analysis, show that the challenging problem of cavity cooling can be successfully solved. Fabrication of a demo 100-mA (at 35 MHz bunch repetition rate) photoinjector is underway. The design is scalable to higher average currents by increasing the electron bunch repetition rate, and provides a path to a MW-class FEL. This paper presents the cavity design and details of RF coupler modeling.