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SRF2003 Show Abstract

Title Development of Superstructures for High Current Application
Type Poster new projects
Abstract Devices for acceleration of electron currents beyond 100 mA are becoming increasingly interesting for high power FELs or for ERLs. To achieve photon beams of several hundreds of kWs, low emittance electron beams of up to 1 A have to be delivered to undulators from a driving linear accelerator. High quality beams and stable operation of the accelerating sections are only possible if the Higher Order Modes (HOM) generated by the beams can be sufficiently damped. The positive experience with the HERA cavities [1], in which the dominant monopole modes are damped to Qext about 700 and all dipole modes to Qext < 6000 makes it highly likely that a superstructure (SST) consisting out of two weakly coupled subunits and employing coaxial HOM dampers of the DESY design can be successfully adapted to a properly designed cavity for acceleration of a 1 A beam. This contribution describes a 750 MHz  SST design for a 1 A electron beam. The calculated R/Q ? values of the HOMs of this SST are quite favorable. The total impedance of the first 16 monopole modes is about 140 Ohm, app. a factor of 3 smaller than the impedance for the fundamental mode. It seems very likely that the HOM?s can be suppressed to the appropriate levels for stable beam operation. In order to explore the achievable damping, a 1500 MHz Cu 1:2 model of the SST was built and the Qext ? value of the dominant HOM?s were measured with various HOM coupler configurations. As a result it can be concluded with some confidence that the necessary damping for a 1A machine can be achieved with the proposed superstructure configuration. However, in a next step it is essential to repeat these measurements on a 1:1 model.

List of authors...

Principle author first.

Last (Family) Name First Name (Initials only) Affiliation or Organization (abbreviations if possible)
Sekutowicz J JLAB/DESY
Kneisel P JLAB

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