Dielectric Based HG Structures II: Diamond Structures; BBU and Multipactor P. Schoessow, A. Kanareykin, C. Jing, A. Kust

2. More DLA Research Activities at Euclid Advances in diamond structure fabrication Beam breakup in dielectric structures Multipactor studies in rf driven DLAs

4. Schematic drawing of a CVD reactor similar to that being used by CTS for PECVD production of diamond tubes.Schematic drawing of a CVD reactor similar to that being used by CTS for PECVD production of diamond tubes.

5. llustration of the technology for the diamond tube CVD fabrication process, 2.4 cm inner diameter diamond tube developed by CTS, Inc. llustration of the technology for the diamond tube CVD fabrication process, 2.4 cm inner diameter diamond tube developed by CTS, Inc.

6. llustration of the technology for the diamond tube CVD fabrication process, 2.4 cm inner diameter diamond tube developed by CTS, Inc. llustration of the technology for the diamond tube CVD fabrication process, 2.4 cm inner diameter diamond tube developed by CTS, Inc.

8. Recent results

11. 2. DLA BBU Studies Experiments: BBU measurements in a number of high gradient and high transformer ratio wakefield devices. Numerics: particle-Green�s function beam dynamics code (BBU-3000) development. The code allows simulation of beam breakup effects in linear accelerators, emphasis on DLAs. 2D/3D Complementary to PIC approach Heuristic group velocity effects for multibunches Beam Dynamics Simulation Platform; access software via web browser, parallelism (cluster/multicore) Efficiency improvement space charge

13. BBU: Planned AWA Experiments

14. 26 GHz Power Extractor

15. 3. Multipactor Simulations

16. Multipactor Discharge Intensity (P=1 MW, Vaughan Parameter Dependence)

22. The present algorithm used in BBU-3000 computes pairwise particle interactions at each time step to determine the forces on each electron in the simulation. This algorithm scales as O(N2) where N is the number of particles used. While for small particle numbers this is not problematic, larger scale problems (particularly ramped bunch train and other multibunch) require a large number of particles and hence can become very inefficient. We are investigating to what extent this can be improved. The most promising approaches are based on a set of algorithms developed in recent years that factor particle-particle interactions into short and long range components. Interactions between particles in close proximity are computed as in the existing code. Forces on a given electron resulting from clusters of electrons at longer separations are handled by replacing the individual cluster particles in the force calculation by a single particle with effective properties computed through the use of spatial averaging. Two of the possible algorithms being considered are known as the Tree-code algorithm and the Fast Multipole Method. Both of these techniques were originally developed for Poisson-type problems involving static charge distributions or many body gravitational dynamics. It is expected that these methods can be adapted to the dynamics of a relativistic beam and will also simplify the implementation of the space charge calculation.

25. Multipactor Discharge, Axial Magnetic Field Ooopic Pro simulation of the evolution of the electron population of the discharge for three different magnetic field strengths (0 G, 150 G, 1500 G). We chose the Saito parameters [6] for the secondary emission model and assumed 2 MW rf power. The simulation shows the rise time of the discharge decreasing with magnetic field strength; however, all reach the same intensity at longer times. The origin of this effect is still being investigated. One possible explanation is that the secondary electrons are turned around by the axial magnetic field sooner after emission than in the zero field case. Since electrons with energies near Emax are more efficient in producing secondaries, the confinement of low energy electrons near the surface may result in a larger overall electron yield.Ooopic Pro simulation of the evolution of the electron population of the discharge for three different magnetic field strengths (0 G, 150 G, 1500 G). We chose the Saito parameters [6] for the secondary emission model and assumed 2 MW rf power. The simulation shows the rise time of the discharge decreasing with magnetic field strength; however, all reach the same intensity at longer times. The origin of this effect is still being investigated. One possible explanation is that the secondary electrons are turned around by the axial magnetic field sooner after emission than in the zero field case. Since electrons with energies near Emax are more efficient in producing secondaries, the confinement of low energy electrons near the surface may result in a larger overall electron yield.