Integration of New Digital Bpm in the Taiwan Light Source

Integration of new generation digital beam position monitor (DBPM) was performed recently. The BPM electronics are commercial available by using direct RF sampling technology, FPGA, and embedded control environment running GNU/Linux. The implementation is emphasized on control system integration and compatible with existing system to enhance functionality and performance of the BPM system. The programmable nature of DBPM system is beneficial for multi-mode high precision beam diagnostics purposes. Sub-micron resolution is achieved for averaged beam position measurement. Medium resolution is obtain for turn-by-turn beam position measurement. Tune and other diagnostic measurements are also supported. The DBPM are seamless integrated with existed control system. System structure and preliminary test results will presented in this report. INTRODUCTION The newly deploy Libera series DBPM system is tested now. This digital BPM electronics are commercial products [3]. That is a four symmetrical channels structure system. It consists of analogyto-digital converter (ADC) in the analog signal processing, digital down converter (DDC), digital filter in the digital signal processing and FPGA is for the data acquisition and control purposes. The four channels digital down converter is that convert 500 MHz beam signal into intermediately basic frequency coherently. Four signals of RF are digitized and processed by quad-digital receiver based on FPGA. The resolution of beam position measurement can be achieved around 10 μm turn-by-turn resolutions. The ADC is based on AD9433. It is used for the analogy to digital conversion. This is a high speed, high performance, low power, and monolithic 12-bit analogy-to-digital converter. All necessary functions, including track-and-hold and reference are included on chip to provide a complete conversion solution. The programmable DDC is composed of synchronization, input, input level detector, carrier mixer, CIC decimating filter, half-band decimating Filter, programmable FIR filter, automatic gain control, Cartesian to Polar converter. The digital data are separated to two ways for outside access after filter. One is wideband access with the circular buffer, other is narrowband access. CONTROL SYSTEM INTERFACE FOR DBPM To simply the complexity, the network access is separated to two ways in this implementation. One is slow access by the Ethernet; other is fast access by rocket I/O. In the fast access, the control system interface is separated to two layers. The embedded layer is planned by the VME64x crate with PowerPC module running the real time operation system of LynxOS. This interface is for fast orbit feedback and provides 10 KHz data update rate for feedback system. In the slow access, the data is acquired from console of user interface via Ethernet. The server host is a Linux server that is between user interface and DBPM. This server is a client for DBPM server. In the same time, it is also a server for user interface. It receives control parameters from user interface by Ethernet and disturbs this setting to DBPM. These parameters include that change operation mode either turn-by-turn mode or closed orbit mode, adjust gain in each channel and access length. The data of DBPM is replied to user interface after receive software trigger from Ethernet. Network connection of the digital BPM testbed is shown in figure 1. The software environment is shown in the figure 2. The DBPM is seamless 10th ICALEPCS Int. Conf. on Accelerator & Large Expt. Physics Control Systems. Geneva, 10 14 Oct 2005, PO1.050-6 (2005)