New PXIe-based LLRF architecture and test bench for heavy ion linear acceleration

This work 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 80MHz in CW mode has been designed and built, being under test in the laboratory. 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 good quality signal generator used as master frequency reference, an analog front end for reference modulation and signal conditioning, small RF components completing the circuit, as well as an aluminium tunable resonant cavity at 80 MHz, whose RF amplitude, phase and frequency are realtime 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 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 much easier the prototyping process and its reconfigurability. The test bench comprises the core LLRF digital PXIe platform together with the cavity, which are connected together through an RF amplifier before the cavity input. Several tests are currently under way using the presented test bench to evaluate the performance of the proposed digital PXIe LLRF architecture for heavy ion linear acceleration following the specifications of the projected future Huelva accelerator.