| Paper | Title | Page |
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| MOPEC055 | Status of the CW Power Couplers for the SRF Linac of the IFMIF Project | 585 |
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The driver of the International Fusion Material Irradiation Facility (IFMIF) consists of two 125 mA, 40 MeV CW deuteron accelerators. A superconducting option for the 5 to 40 MeV linac based on Half-Wave Resonators (HWR) has been chosen. The first cryomodule houses 8 HWR's supplied by high power RF couplers; each of them should be able to operate at 200 kW in CW. This paper will give an overview of the RF design of the 175 MHz CW power coupler. The detailled mechanical studies and the realization will be performed by the Industry. Global approach of the contract with the Industry and the organization of the intermediate validation tests will be discussed. In a second part, the choices and the last advances concerning the couplers RF power test stand will be described. |
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| MOPD026 | Unsegmented vs. Segmented 4-Vane RFQ: Theory and Cold Model Experiments | 735 |
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The RF design of a RFQ should satisfied several conditions, namely: voltage profile required by beam dynamics, a tunable structure, RF stability and reasonable sensitivity to possible perturbations induced by power operation. Voltage profile may be obtained either by a dedicated profiling of 2D cross-section and/or slug tuner adjustment. Tunability is directly related to spatial distribution of tuners. RF stability requires sufficient separation between accelerating quadrupole mode and (i) adjacent quadrupole modes, or (ii) adjacent dipole modes. Quadrupole modes separation is directly related to RFQ length, and can be increased if necessary via segmentation; position of dipole modes spectrum w.r.t. quadrupole spectrum may be adjusted using rod stabilizers inserted at RFQ ends and on either side of coupling circuits. We present a thorough comparison of these two options for a 6-meter long structure at 352 MHz, and show they both lead to a tunable structure. The design includes 3D electromagnetic simulation and application of transmission line to tuning. The sensitivity of both designs to perturbations is also evaluated. |
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| MOPD027 | The RF Design of the Linac4 RFQ | 738 |
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In the Linac 4 and the SPL, a 3 MeV RFQ is required to accelerate the H- beam from the ion source to the DTL input energy. While the 6-meter long IPHI RFQ was initially chosen for this application, a CERN study* suggested that a dedicated, shorter 3-meter RFQ might present several advantages. The 2D cross-section is optimized for lower power dissipation, while featuring simple geometrical shape suitable for easy machining. RF stability is evaluated using a 4-wire transmission model and 3D simulations, taking electrode modulation into account. The resulting RFQ is intrinsically stable and do not require rod stabilizers. End circuits are tuned with dedicated rods. RF power is fed via a ridged waveguide and a slot iris. Vacuum port assemblies are positioned prior to brazing to minimize RF perturbation. The 32 tuning slugs form a set of stable sampling, able to tune 9 modes. Tuner parameters are derived from bead-pull accuracy specification and fabrication tolerances. Signals delivered by pickup loops inserted in 16 of these tuners will be used to reconstruct the voltage profile under operation. Thermo-mechanical simulations are used to design temperature control specifications. |
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| WEPEC001 | Cryogenic Tests of a 704 MHZ 1MW Power Coupler | 2884 |
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Coaxial power couplers capable of handling 1MW peak power have been developped for high intensity superconducting proton linacs. They have been conditioned in travelling wave up to the maximum power available on the Saclay test bench, 1.2 MW forward peak power, up to 10% duty cycle. One coupler has been assembled on a 5-cell medium beta cavity in the class 10 area of the clean room, and installed in our horizontal test cryostat CryHoLab. This paper focusses on the RF operation of the coupler in this cryogenic environment and thermal aspects. |