PXIe-Based LLRF Architecture and Versatile Test Bench for Heavy Ion Linear Acceleration

This paper describes the architecture of a digital LLRF system for heavy-ion acceleration developed under the specification of the projected future heavy-ion accelerator facility in Huelva, Spain. A prototype LLRF test bench operating at 80 MHz in CW mode has been designed and built. The core LLRF control has been digitally implemented on a PXIe chassis, including an FPGA for digital signal processing and a real time controller. The test bench is completed with a low phase and amplitude noise signal generator used as master frequency reference, an analog front end for reference modulation and signal conditioning, some RF components completing the circuit, as well as a tunable resonant cavity at 80 MHz, whose RF amplitude, phase and frequency are real-time controlled and monitored. The presented LLRF system is mainly digitally implemented using a PXIe platform provided by National Instruments , and is based on IQ modulation and demodulation. The system can be configured to use both direct sampling and undersampling techniques, resulting thus in a high performance and versatile RF control system without the need of excessive computational resources or very high speed acquisition hardware. All the system is programmed using the LabVIEW environment, which makes the prototyping process and its reconfigurability much easier.