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| THP011 |
High Gradient Operation with the CEBAF Upgrade RF Control System
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589 |
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- C. Hovater, G. K. Davis, H. Dong, A. S. Hofler, K. King, J. Musson, T. E. Plawski
Jefferson Lab, Newport News, Virginia
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The CEBAF Accelerator at Jefferson Lab is presently a 6 GeV five pass electron accelerator consisting of two superconducting linacs joined by independent magnetic transport arcs. It is planned to increase the energy to 12 GeV with the addition of 10 new high gradient cryomodules (17+ MV/m). The higher gradients pose significant challenges beyond what the present analog low level RF (LLRF) control systems can handle reliably; therefore, a new LLRF control system is needed. A prototype system has been developed incorporating a large FPGA and using digital down and up conversion to minimize the need for analog components. The new system is more flexible and less susceptible to drifts and component nonlinearities. Because resonance control is critical to reach high gradients quickly, the new cryomodules will include a piezoelectric tuner for each cavity, and the LLRF controls must incorporate both feedback and feed-forward methods to achieve optimal resonance control performance. This paper discusses development of the new RF system, system performance for phase and amplitude stability and resonance control under Lorentz detuning measured during recent tests on a prototype cryomodule.
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| THP019 |
Commissioning of the Digital LLRF for the CEBAF Injector/Separator
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607 |
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- T. E. Plawski, H. Dong, C. Hovater, K. King, G. E. Lahti, J. Musson
Jefferson Lab, Newport News, Virginia
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The design and production of the CEBAF accelerator 499 MHz digital Low-Level RF control system has been completed. The first five systems were installed for use with the CEBAF Separator RF deflecting cavities operating at 499 MHz. The next four systems were installed in the injector on the chopping cavities (also 499 MHz deflecting cavities). The new LLRF system replaced an analog system that was over 15 years old. For initial testing an extensive acceptance plan along with a LLRF test stand was developed and incorporated to assure system performance as well as reliability. Various VHDL firmware was developed and modified to support operation of this system and included specific operational diagnostics. Once the acceptance tests were completed, the new systems were installed in the accelerator, in parallel with the existing analog LLRF, for extensive in-situ testing and comparison. After system commissioning, the new RF systems were assigned to the CEBAF accelerator and turned over to Accelerator Operations. This paper will address the VHDL firmware evolution, the automated tests and the performance measurements made through out the installation and commissioning process.
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