| Paper |
Title |
Page |
| TUP93 |
Results of a 3D-EM-Code Comparison on the TRISPAL Cavity Benchmark
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495 |
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- P. Balleyguier
CEA/DAM, Bruyères-le-Châtel
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Several 3D electromagnetic codes (MAFIA, CST MicroWave-Studio, Vector-Fields Soprano, Ansoft HFSS, SLAC Omega3P) have been tested on a 2-cell cavity benchmark. Computed frequencies and Q-factors were compared to experimental values measured on a mock-up, putting the emphasis on the effect of coupling slots. It comes out that MAFIA limitations due to the staircase approximation is overcome by all other codes, but some differences still remain for losses calculations in re-entrant corners
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| TUP94 |
Parallel Particle in Cell Computation of an Electron Gun with GdfidL
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498 |
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- W. Bruns
TU Berlin TET, Berlin
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The paper describes an efficient algorithm to integrate the equations of a fast moving charge cloud of small size in a large electron gun. Particle in cell computations of a realistic electron gun is challenging due to the large discrepancy between the size of the cavity and the size of the cloud. A fine grid must be used to resolve the small volume of the charge, with a grid spacing in the order of 0.1 mm. The cavity has extensions of about 100 mm. Therefore one has to deal with about 1000 million gridcells. Such a large grid is handled best with parallel systems. Each node of the parallel system computes the electromagnetic field in its subvolume. As the extension of the charge keeps being small during the flight, at each timestep the charged particles will be located in only a few subvolumes of the nodes of the parallel system. This would lead to a strong load imbalance, if the particle related computations for each particle would be performed by the node where the particle is in. GdfidL instead spreads the data of all particle over all processors, which perform the particle related computations, and send back the results to the processors where the particles are in.
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| TUP95 |
Evaluation of Magnetic Field Enhancement Along a Boundary
|
501 |
| |
- Y. Iwashita
Kyoto ICR, Kyoto
- T. Higo
KEK, Ibaraki
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Generally, a cavity has convex corners on its inner surface, where the surface field becomes higher than the average accelerating gradient. This effect has been paid attention not to exceed a criterion only on surfaces that have high electric field gradient. A high magnetic field area, however, sometimes seems harmful on a stable operation too. Such enhancement factors are evaluated in a 2D model to show a feasible crossing angle limit on a convex angle of two surfaces.
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| TUP96 |
Mechanical Stability Simulations on a Quarter Wave Resonator for the SPIRAL II Project
|
504 |
| |
- H. Saugnac, J.-L. Biarrotte, S. Blivet, S. Bousson, M. Fouaidy, T. Junquera, G. Olry
IPN, Orsay
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In the framework of the SPIRAL II project, IPN Orsay is studying a 88 MHz β=0.12 super conducting quarter wave resonator prototype. Due to its low RF bandwidth (around 60 Hz) the resonator must have a very high mechanical stability and have small sensitivity to dynamic mechanical loads. To simulate the effects of geometrical deformations on the fundamental RF frequency a three dimensional analysis is required. The simulations were made by coupling mechanical FEM analysis performed in COSMOS/GEOSTAR™ with the RF electromagnetic FEM code MICAV™ integrated in the COSMOS/GEOSTAR™ interface. Static mechanical loads were first studied to reduce the effects of external pressure on the RF frequency shift and evaluate the tuning sensitivity of the cavity. Then, simulations on the dynamic response of the resonator, using the modal superposition analysis method, with random external pressure variations and harmonic excitation of the cavity were performed. This paper presents the results of the simulations and mechanical solutions chosen to increase the cavity RF frequency stability.
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| TUP97 |
Some Estimations for Correlation Between the RF Cavity Surface Temperature and Electrical Breakdown Possibility
|
507 |
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- V.V. Paramonov
RAS/INR, Moscow
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The electrical breakdown in accelerating cavities is the complicated phenomenon and depends on many parameters. Some reasons for breakdown can be avoided by appropriate vacuum system design and the cavity surface cleaning. This case, for normal conducting accelerating cavities free electrons - the dark currents due to Fowler-Nordheim emission can be considered as the main reason of possible electrical breakdown. It is known from the practice - the combination of the high electric field at the cavity surface with high surface temperature is the subject for risk in the cavity operation. In this paper the dependence on the surface temperature is considered and 'effective' electric field enhancement is discussed.
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