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

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.

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The new superconducting RF system consisting of four single-cell cavity modules is an important part of the CESR Luminosity Upgrade.We describe the commissioning of the first three accelerating modules. This includes in situ testing and conditioning, pulsed power and beam processing of RF windows, commissioning of various cryogenic feedback loops, measuring cavity spacing and phasing with beam, and high-current operation.

Recent progress in developing digital low-level RF controls for accelerators has made digital systems an option of choice. At Cornell we are presently working on two projects: upgrading the RF controls of the Cornell Electron Storage Ring (CESR) for charm-tau operation (CESR-c) and developing a new low-level RF system for the proposed Cornell energy-recovery linac (ERL). The present CESR RF control design is based on classic analog amplitude and phase feedback loops. In order to address the required flexibility of the RF control system in the CESR-c upgrade and to implement a true vector sum control we have designed and built a new digital control system. The main features of the new controller are high sampling rates, high computation power and very low latency. The digital control hardware consists out of a powerful VME processing board with a Xilinx FPGA, an Analog Devices digital signal processor (DSP) and memory. A daughter board is equipped with four fast analog-todigital converters (up to 65 MHz sampling rate) and two digitaltoanalog converters (up to 50 MHz update rate). The first set of new electronics will be used in the CESR RF system. However, the described digital control hardware can also be used for the Cornell ERL as it was designed to meet its challenging field stability requirements (see [1] ).