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| MOP69 | RF Control Modelling Issues for Future Superconducting Accelerators | resonance, feedback, diagnostics, linac | 180 | ||||
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The development of superconducting accelerators has reached a high level of maturity following the successes of ATLAS at Argonne, CEBAF at Jefferson Lab, the TESLA Test Facility at DESY and many other operational accelerators. As a result many new accelerators under development (e.g. SNS) or proposed (e.g. RIA) will utilize this technology. Covering all aspects from cw to pulsed rf and/or beam, non-relativistic to relativistic particles, medium and high gradients, light to heavy beam loading, linacs, rings, and ERLs, the demands on the rf control system can be quite different for the various accelerators. For the rf control designer it is therefore essential to understand these issues and be able to predict rf system performance based on realistic rf control models. This paper will describe the features that should be included in such models and present an approach which will drive the development of a generic rf system model.
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| MOP70 | A Pass Band Performance Simulation Code of Coupled Cavities | simulation, linac, coupling, RF-structure | 183 | ||||
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A simulation code of accelerating cavities named PPSC is developed by the solutions of the microwave equivalent circuit equations. PPSC can give the pass band performance of periodic or non-periodic accelerating structures, such as the dispersion frequency and the reflection factor of the cavity, the field distribution of each mode and so on. The natural parameters of the structure, such as the number of the cavities, the resonant frequencies and Q-factors of each cavity, the coupling factor between two cavities, and the locations of the couplers, can be changed easily to see the different results of the simulation. The code is written based on MS Visual Basic under MS windows. With these, a user-friendly interface is made. Some simple examples was simulated and gave reliable results.
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| TUP43 | The Superconducting CW Driver Linac for the BESSY-FEL User Facility | linac, emittance, simulation, gun | 363 | ||||
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A CW FEL User Facility for the VUV to soft X-ray spectral range based on a cascaded HGHG-FEL scheme is planned at the BESSY site. The Technical Design Report has recently been submitted to the German Wissenschaftsrat. Beam acceleration to 2.3 GeV is provided by a 144-cavity superconducting driver linac based on TESLA technology modified for CW operation. Initially, a high-rep-rate normal-conducting photoinjector will be used but a fully CW superconducting version is being investigated for a future upgrade. Bunch compression to 2 kA peak current is achieved in a three-stage scheme involving two bunch compressors and an arc. An overview of the linac layout, including the rf and cryogenic distribution, is provided here. We also discuss the impact of CW operation and the modifications to the TESLA technology that are necessary. Predictions of the linac performance are also given.
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| THP59 | Low Level RF Including a Sophisticated Phase Control System for CTF3 | klystron, linac, collider, linear-collider | 748 | ||||
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CTF3 (CLIC Test Facility 3), currently under construction at CERN, is a test facility designed to demonstrate the key feasibility issues of the CLIC (Compact LInear Collider) two-beam scheme. When completed, this facility will consist of a 150 MeV linac followed by two rings for bunch-interleaving, and a test stand where 30 GHz power will be generated. In this paper, the work that has been carried out on the linac’s low power RF system is described. This includes, in particular, a sophisticated phase control system for the RF pulse compressor to produce a flat-top rectangular pulse over 1.4 μs.
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| THP66 | Measurement and Control of Microphonics in High Loaded-Q Superconducting RF Cavities | damping, linac, superconductivity, feedback | 763 | ||||
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Superconducting radio frequency (SRF) linacs with light beam loading, such as the CEBAF upgrade, RIA and energy recovery linacs, operate more efficiently with loaded-Q values >1·107. The narrow band-width puts stringent limits on acceptable levels of vibration, also called microphonics, that detune the SRF cavities. Typical sources of vibration are rotating machinery, fluid fluctuations and ground motion. A prototype RIA 805 MHz v/c=0.47 cryomodule is presently under test in realistic operating conditions [1]. Real-time frequency detuning measurements were made for modulation rates from DC to 1 kHz. At 2 K the maximum frequency deviation was less than 100 Hz peak-to-peak, and was consistent with high loaded-Q operation. The measured modulation spectrum was primarily made up of discrete Fourier components with modulation frequencies less than 80 Hz. Using an accelerometer and helium pressure transducer, the primary sources of vibration were determined to be the high power cryoplant motors and 2 K helium fluctuations. Adaptive feedforward was used to decrease the magnitude of individual Fourier components by four to ten times [2]. Details of the experimental setup and measurements will be presented.
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[1] “Experimental Study of an 805 MHz Cryomodule for the Rare Isotope Accelerator”, T.L. Grimm et al., THP70, these proceedings. [2] “Adaptive Feedforward Cancellation (AFC) of Sinusoidal Disturbances in SRF Cavities”, H. Khalil et al., TUP76, these proceedings. |
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