| Paper | Title | Other Keywords | Page |
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| MOPS072 | Broadband Electromagnetic Characterization of Materials for Accelerator Components | impedance, simulation, kicker, damping | 769 |
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| Electromagnetic (EM) characterization of materials up to high frequencies is a major requirement for the correct modeling of many accelerator components: collimators, kickers, high order modes damping devices for accelerating cavities. In this scenario, the coaxial line method has gained much importance compared to other methods because of its applicability in a wide range of frequencies. In this paper we describe a new coaxial line method that allows using only one measurement setup to characterize the material in a range of frequency from few MHz up to several GHz. A coaxial cable fed at one side is filled with the material under test and closed on a known load on the other side. The properties of the material are obtained from the measured reflection coefficient by using it as input for a transmission line (TL) model or for 3D EM simulations, which describe the measurements setup. We have applied this method to characterize samples of SiC (Silicon Carbide) which could be used for LHC collimators and for CLIC accelerating structures and NiZn ferrite used for kicker magnets. | |||
| TUPC008 | CLIC Two-Beam Module for the CLIC Conceptual Design and Related Experimental Program | alignment, linac, vacuum, quadrupole | 1003 |
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| The Compact LInear Collider (CLIC), being studied at CERN, involves the design and integration of many different technical systems, tightly bound and influencing each other. For the construction of two main linacs it has been decided to proceed with a modular design, and repetitive two-beam modules of a few types were defined. The modules consist of micro-precision components operating under ultra-high vacuum as required by the beam physics. For the CLIC Conceptual Design Report, the development and system integration is mainly focused on the most complex module type containing the highest number of components and technical systems. For proving the proper functioning of the needed technical systems and confirming their feasibility it has been decided to build four prototype modules and test them without beam. In addition, three modules have to be produced in parallel for tests in the CLIC Experimental Area with beam. This paper is focused on the design of the different technical systems and integration issues of the two-beam module. The experimental program for the prototype modules is also recalled. | |||
| TUPC012 | Fabrication and Validation of the Prototype Supporting System for the CLIC Two-beam Modules | alignment, radiation, tandem-accelerator, linac | 1015 |
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| The Compact LInear Collider (CLIC), currently under study at CERN, aims at the development of a Multi-TeV e+ e- collider and relies upon a novel two-beam acceleration concept. In the two-beam acceleration, the Radio Frequency (RF) power is extracted from a low energy but high-intensity particle beam, and it is transferred to a parallel high energy main beam. The two-beam modules are the smallest repetitive units which compose the two linacs. The RF structures are the most precise components and they are mounted and aligned on specially developed supporting system, which provides stability and quick re-positioning. The supporting girders have stringent stiffness and damping requirements, imposed by beam physics requirements. In addition, several constraints, such as allocated space and weight limitation have to be taken into consideration. This paper describes different girder configurations following various fabrication techniques and materials. Extensive qualification measurements have been performed on the first prototype units, and the main results are also presented. | |||
| TUPC018 | Progress on Modelling of the Thermo-Mechanical Behavior of the CLIC Two-Beam Module | vacuum, simulation, linac, collider | 1033 |
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| The luminosity goal of the CLIC collider, currently under study, imposes micrometer mechanical stability of the 2-m long two-beam modules, the shortest repetitive elements of the main linacs. These modules will be exposed to variable high power dissipation during operation resulting in mechanical distortions in and between module components. The stability of the CLIC module will be tested in laboratory conditions at CERN in a full-scale prototype module. In this paper, the FEA model developed for CLIC prototype module is described. The thermal and structural results for the new module configuration are presented considering the thermo-mechanical behavior of the CLIC collider in its primary operation modes. These results will be compared to the laboratory measurements to be done during 2011 and 2012 with the full-scale prototype module. The experimental results will allow for better understanding of the module behaviour and they will be propagated back to the present thermo-mechanical model. | |||
| TUPO034 | Longitudinal Stability of ERL with Two Accelerating RF Structures | linac, cavity, electron, simulation | 1509 |
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Modern ERL projects use superconductive accelerating RF structures. Their RF quality is typically very high. Therefore, the RF voltage induced by electron beam is also high. In ERL the RF voltage induced by the accelerating beam is almost canceled by the RF voltage induced by the decelerating beam. But, a small variation of the RF voltage may cause the deviations of the accelerating phases. These deviations then may cause further voltage variation. Thus the system may be unstable. The stability conditions for ERL with one accelerating structure are well known [*, **]. The ERL with split RF structure was discussed recently [***, ****]. The stability conditions for such ERLs are discussed in this paper.
* L. Merminga et al.,Annu. Rev.Nucl. Part. Sci. 53 (2003) 387. ** N.A. Vinokurov et al.,Proc. SPIE 2988 (1997) 221. *** D. Douglas, ICFA BD-Nl 26 (2001) 40. ****N.A. Vinokurov et al.,Proc. IPAC’10. |
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| WEPC098 | Automatic Pole and Q-Value Extraction for RF Structures | resonance, scattering, cavity, cryomodule | 2241 |
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| The experimental characterization of RF structures like accelerating cavities often demands for measuring resonant frequencies of Eigenmodes and corresponding (loaded) Q-values over a wide spectral range. A common procedure to determine the Q-values is the -3dB method, which works well for isolated poles, but may not be applicable directly in case of multiple poles residing in close proximity (e.g. for adjacent transverse modes differing by polarization). Although alternative methods may be used in such cases, this often comes at the expense of inherent systematic errors. We have developed an automation algorithm, which not only speeds up the measurement time significantly, but is also able to extract Eigenfrequencies and Q-values both for well isolated and overlapping poles. At the same time the measurement accuracy may be improved as a major benefit. To utilize this procedure merely complex scattering parameters have to be recorded for the spectral range of interest. In this paper we present the proposed algorithm applied to experimental data recorded for superconducting higher-order-mode damped multi-cell cavities as an application of high importance. | |||
| WEPZ007 | Multi-mode, Two-beam Accelerator with Feedback | cavity, feedback, impedance, accelerating-gradient | 2778 |
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| A high-gradient accelerator consisted of the test and the drive beam structures is reported. The accelerating structure can be based on dielectric or corrugated cavities separated each other by irises. Each cavity is operated by several axisymmetric, TM-like eigen-modes with longitudinal indices to be related to frequencies. These modes are excited at Fourier harmonics of the drive current which consists of bunches spaced with the same period as test bunches. The superposition of the excited modes introduces a short RF pulse propagated in-phase with a moving test bunch and after reflection by iris (a feedback) this pulse can accelerate next bunch. Such longitudinally-sweeping RF field promises a reduction of the exposure time and due to compact space shape can help to obtain high shunt impedance. | |||
| THPS094 | New Approaches in High Power RFQ Technology | rfq, vacuum, linac, resonance | 3654 |
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| There is a clear tendency for the utilization of continuous wave c.w. high power RFQs in a huge variety of applications like nuclear waste transmutation or material research. They can serve as injectors for the production of secondary particles like neutrons or rare isotopes and can be applied for post acceleration of the latter ones. These RF-structures have to withstand an enormous amount of RF-power dissipated on the surfaces (up to several 10s kW per meter) and the associated thermal load. NTG Company gained lots of experience especially in the field of 4-rod c.w. RFQ design. Most recent developments to handle such high RF-power dissipation shall be reported. | |||