K. H. Hu

Commissioning of FPGA‐based Transverse and Longitudinal Bunch‐by‐Bunch Feedback System for the TLS

Multi‐bunch instabilities deteriorate beam quality, increasing beam emittance, or even causing beam loss in the synchrotron light source. The feedback system is essential to suppress multi‐bunch instabilities caused by the impedances of beam ducts, and trapped ions. A new FPGA based transverse and longitudinal bunch‐by‐bunch feedback system have been commissioned at the Taiwan Light Source recently, A single feedback loop is used to simultaneously suppress the horizontal and the vertical multi‐bunch instabilities. Longitudinal instabilities caused by cavity‐like structures are suppressed by the longitudinal feedback loop. The same FPGA processor is employed in the transverse feedback and the longitudinal feedback system respectively. Diagnostic memory is included in the system to capture the bunch oscillation signal, which supports various studies.

Turn-by-turn BPM electronics based on 500 MHz log-ratio amplifier

Log-ratio processor working at 500 MHz applied to turn-by-turn beam position measurement was implemented. The processor circuit consists of two logarithmic amplifiers and a subtraction circuit. The output value is proportional to beam position. Before, the upper usable frequency of logarithmic amplify is lower than 500 MHz. At present, several manufacturers support higher upper usable frequency of logarithmic amplifiers. In this paper, we present the performance test result of the 500 MHz log-ratio processor applied to turn-by-turn BPM electronics.

Performance of the rejuvenated injector control system in SRRC

The original injector control system is a turnkey design and it was separated from the storage ring control system. It is not easy to maintain and install new devices. The control system of injector has been rejuvenated recently. There are two basic requirements for this plan, to provide more efficient and stable light source operation, and to reduce the maintenance resource need. Its implementation will also be helpful for improvement on reliability and control response time. Upgrade injector from 1.3 GeV to 1.5 GeV will be done before the end of 1999. The renewed injector control system will be able to provide improved environment for application program development and new devices installation. Automatic control operation for full energy injection will be implemented in SRRC.

Beam position monitoring system for the 1.5 GeV transport line of NSRRC

The extracted 1.5 GeV electron beams from the booster synchrotron are transported via a transport line and injected into the storage ring. This booster-to-storage ring transport line equipped with seven stripline beam positions monitors. Commercial log-ratio BPM electronics were adopted to process the 500 MHz bunch signal directly. The position of the passing beam is digitized by VME analog interface. This report addresses the system architecture, software tools, and performance of the BTS trajectory measurement. This system will provide an elegant tool for optimizing the performance of the transport line. Preliminary results and possible applications are included.

Upgrading the orbit feedback system in the Taiwan light source

The global orbit feedback system plays a crucial role in the operation of the Taiwan Light Source (TLS). Various issues must be addressed to achieve maximize performance. The orbit feedback system was upgraded recently to meet increasing demand. Based upon operational experience during the last few years, a new system was designed to provide an environment for easy maintenance, real-time monitoring of performance, and trouble-shooting of the feedback loop. Highly robust and flexible controllers are now also supported. A general-purpose CPU real-time operation system has replaced the former DSP boards to reduce the resources required and provide a superior software development environment. Performance analysis tools were also developed to monitor system performance. Highly integrated commercial off-the shelf products (COTS) were used to support various beam studies and evaluation of the performance of the system. The implementation of these systems is discussed herein

Simple Amplitude and Phase Detector for Accelerator Instrumentation

Amplitude and phase are important parameters of an RF system and beam properties. Commercial RF/IF gain and phase detector chip can be simply used to extract amplitude and phase information. This detector can measure the amplitude log ratio and phase difference between OR of two RF signals simultaneously. The method is simpler to implement than other methods. Design consideration and implementation details will be discussed in this report. Preliminary test results and possible applications will be summary in this report.

Preliminary transverse and longitudinal phase space study at TLS

Turn-by-turn beam position monitors and phase detectors have been implemented recently for the Taiwan Light Source (TLS). Transverse as well as longitudinal phase space has been explored using turn-by-turn beam position and phase measurement in single bunch mode. Single bunch longitudinal beam transfer function measurement is also performed with various excitation amplitudes. Preliminary results of these experiments are summarized.

Insertion devices control development at SRRC

Insertion devices are the most important gadget of the third generation Taiwan Light Source at SRRC. These insertion devices include the turn-key systems and in-house developed systems in SRRC. The corresponding control configurations are different due to historical reason. However precision, fastness, simplicity, and uniformity in insertion devices control are the most desirable from practical viewpoint. The proposed uniform control systems are first applied successfully to undulator U10 prototype and experimental one meter length adjusted polarizing undulator. The new system provides several features which are not available in existed insertion device control system. The residual field compensation procedure can be done with 100 times per second. The compensation table is updated from the server of the control system. The software design supports the beamline users to adjust the gap after granting permission from the control room operator. The detailed descriptions about the features and performances will be presented in this report.

Beam loss studies at the Taiwan Photon Source

PIN-photodiodes and RadFETs are installed in the storage ring of the Taiwan Photon Source (TPS) to study beam loss distributions and mechanisms. In the highest dose area, the radiation comes mainly from hard X-rays produced by synchrotron bending magnets. During beam cleaning and after replacing a vacuum chamber, losses due to inelastic Coulomb scattering occur mostly downstream from bending magnets while elastic scattering causes electrons to get lost mainly after an elliptically polarizing undulator which has a limited vertical aperture. During the injection period, the beam loss pattern can be changed by modifying injection conditions or lattice settings. The beam loss usually happens in the injection section and small-aperture section. The injection efficiency can be improved by minimizing the detected injection loss.

Methods to detect error sources and their application at the TPS

For a low-emittance photon light source, beam stability is a very important property to attain a high-quality photon beam. While it is hard to avoid beam perturbations in a storage ring, it is more important to quickly find the source locations and to remove or eliminate the sources as soon as possible. In this report, we develop a method to identify the locations of multiple sources. For a source with a particular frequency, the relative phase between sources can also be obtained. This method has been a useful tool during TPS operation and its methodology and practical applications are described in this report.