Status and commissioning-results of BESSY II
The new Storage Ring BESSY II in Berlin Germany is a dedicated third generation synchrotron radiation source for the VUV and soft X-ray spectral range. On April 22/sup nd/, 1998 a 1.7 GeV electron beam was stored for the first time. Despite a relatively short time for commissioning of the synchrotron radiation source, the milestones were met as scheduled. Accelerator parameters that determine the quality of the synchrotron radiation are as designed or the design goals were even exceeded. The only parameter that is still not according to design is the beam lifetime, as the baking of the vacuum system is not completed yet. The regular scientific program started according to plan in January 1999 with experiments. The front-end for 22 additional beamlines are installed and scheduled for use before the end of next year. Thus required shutdown periods will also be used to install additional hardware to improve the performance of the ring.
Experiences with commissioning software tools at BESSY II
Software requirements evolve rapidly during the short commissioning period of a third generation light source. Main focus moves from atomic device control to complex conditioning, experiment performance, measurement data taking, beam quality maintenance and performance monitoring tasks. From the very beginning the essential tools have to be set up properly and need to be sufficiently adaptive to easily absorb the actual findings of the running in procedures. In this paper the major software modules at BESSY II are depicted and their relevance for the progress of the commissioning is rated. Implemented functionalities and used methods are described in more detail for the basic workhorses (like compound devices, handling of snapshot files, orbit control). Explanations are given why certain tools turned out to be less accepted or useful (yet).
Operation and performance of the PEP-II prototype longitudinal damping system at the ALS
A modular programmable longitudinal feedback system has been developed as a component of the PEP-II R+D program. This system is based on a family of VME and VXI packaged signal processing functions which implement a general purpose digital feedback controller for accelerators with bunch spacings of 2 ns. A complete PEP-II prototype system has been configured and installed for use at the LBL Advanced Light Source. The system configuration used for tests at the ALS is described and results are presented showing the action of the feedback system. Open and closed loop results showing the detection and calculation of feedback signals from bunch motion are presented and the system is shown to damp coupled-bunch instabilities in the ALS. Use of the system for accelerator diagnostics is illustrated via measurement of grow-damp transients which quantify growth rates without feedback, damping rates with feedback, and identify unstable modes.