| Paper | Title | Page |
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| WEPMS063 | Preliminary Results from Prototype Niobium Cavities for the JLab Ampere-Class FEL | 2487 |
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Funding: This manuscript has been authored by Jefferson Science Associates, LLC under U. S. DOE Contract No. DE-AC05-06OR23177, and by the office of Naval Research under contract to the Department of Energy.
In a previous paper the cavity* design for an Ampere-class cryomodule was introduced. We have since fabricated a 1500 MHz version of a single cell cavity with waveguide couplers for HOM and fundamental power, attached to one end of the cavity, a 5-cell cavity made from large grain niobium without couplers and a complete 5-cell cavity from polycrystalline niobium featuring waveguide couplers on both ends. A 750 MHz single cell cavity without endgroups has also been manufactured to get some information about obtainable Q-values, gradients and multipacting behavior at lower frequency. This contribution reports on the various tests of these cavities.
* R. A.Rimmer et al.; EPAC 2006, paper MOPCH182 |
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| WEPMS089 | Multipacting Analysis of a Quarter Wave Choke Joint used for Insertion of a Demountable Cathode into a SRF Photoinjector | 2544 |
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Funding: Work done under the auspices of the US DOE. The multipacting phenomena in accelerating structures and coaxial lines are well documented and methods of mitigating or suppressing it are understood. The multipacting that occurs in a quarter wave choke joint designed to mount a cathode insertion stalk into a superconducting RF photoinjector has been analyzed via calculations and experimental measurements and the effect of introducing multipacting suppression grooves into the structure is analyzed. Several alternative choke joint designs are analyzed and suggestions made regarding future choke joint development. Furthermore, the problems encountered in cleaning the choke joint surfaces, factors important in changes to the secondary electron yield, are discussed and evaluated. This design is being implemented on the BNL 1.3 GHz photoinjector, previously used for measurement of the quantum efficiency of bare Nb, to allow for the introduction of other cathode materials for study, and to verify the design functions properly prior to constructing our 703 MHz photoinjector with a similar choke joint design. |
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| WEPMS068 | JLab High-Current CW Cryomodules for ERL and FEL Applications | 2493 |
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Funding: Authored by Jefferson Science Associates, LLC under U. S. DOE Contract No. DE-AC05-06OR23177, and by The Office of Naval Research under contract to the Dept. of Energy. We describe the developments underway at JLab to develop new CW cryomodules capable of transporting up to Ampere-levels of beam currents for use in ERLs and FELs. Goals include an efficient cell shape, high packing factor for efficient real-estate gradient and very strong HOM damping to push BBU thresholds up by two or more orders of magnitude compared to existing designs. Cavity shape, HOM damping and ancillary components are optimized for this application. Designs are being developed for low-frequency (750 MHz), Ampere-class compact FELs and for high-frequency (1.5 GHz), 100 mA configurations. These designs and concepts can easily be scaled to other frequencies. We present the results of conceptual design studies, simulations and prototype measurements. These modules are being developed for the next generation ERL based high power FELs but may be useful for other applications such as high energy light sources, electron cooling, electron-ion colliders, industrial processing etc. |