High-power, high-brightness electron beams are of interest for many applications, especially as drivers for free electron lasers and energy recovery linac light sources. For these particular applications, photoemission injectors are used in most cases, and the initial beam brightness from the injector sets a limit on the quality of the light generated at the end of the accelerator. At Cornell University, we have built such a high-power injector using a DC photoemission gun followed by a superconducting accelerating module. Recent results will be presented demonstrating record setting performance up to 65 mA average current with beam energies of 4-5 MeV. V

Methods exist in today’s published literature which establish proximity to the ratchet boundary of a given load set by decomposing a cyclic load history into constant and cyclic components. Such methods operate by calculating the utilisation of yield capacity throughout the structure in response to the cyclic load. The remaining yield capacity is then available to support the constant load. In this paper, a hybrid procedure is described which uses established finite element techniques to obtain a stable response to the cyclic load component, followed by a limit load analysis based on the remaining yield capacity, to calculate the maximum primary load. This approach is particularly useful in conjunction with Fourier based cyclic procedures which, although capable of predicting the existence of a stable cyclic response, are not based on classical shakedown theory and are therefore unable to predict proximity to ratchet, unless a search procedure is used. The hybrid approach provides the combined benefit of an efficient cyclic response calculation scheme with a measure of proximity to the ratchet boundary. In this paper, the hybrid method is applied to the Bree case before application to a more complex thermo-mechanical transient, typical of nuclear power plant loading. The generation of interaction diagrams for both cases is considered.

The Cornell University energy recovery linac (ERL) photoinjector has recently demonstrated operation at 20 mA for approximately 8 hours, utilizing a multialkali photocathode deposited on a Si substrate. We describe the recipe for photocathode deposition, and will detail the parameters of the run. Post-run analysis of the photocathode indicates the presence of significant damage to the substrate, perhaps due to ion back-bombardment from the residual beam line gas. While the exact cause of the substrate damage remains unknown, we describe multiple surface characterization techniques (x-ray fluorescence spectroscopy, x-ray diffraction, atomic force, and scanning electron microscopy) used to study the interesting morphological and crystallographic features of the photocathode surface after its use for high current beam production. Finally, we present a simple model of crystal damage due to ion back-bombardment, which agrees qualitatively with the distribution of damage on the substrate surface.

Beginning in April 2008, we propose to employ the Cornell Electron Storage Ring (CESR) in a program of research and development for the International Linear Collider (ILC) Damping Rings (DR). This paper provides an update on the conceptual design issues for the CESR reconfiguration and details of the experimental program that will follow.

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