Diamond, Oxfordshire
With refined lattice tuning it becomes increasingly important to monitor or feedback on many parameters to keep stable optimum operating conditions. To this end we present techniques to measure betatron tune, chromaticity, betafunction magnitude/phase, and orbit response matrices all in such a way that no disturbance to the stored beam can be observed by the users of the light source. Examples of measurements for the various categories are compared to established methods, and their use in feedback schemes is discussed.
LANL, Los Alamos, New Mexico
A beam position reproducibility measurement was performed using the beam position monitors in the Los Alamos Proton Storage Ring. The purpose of this measurement was to gain a better understanding of the quality, errors, and repeatability associated with such a measurement. Described here is a somewhat detailed understanding of how the beam position monitor measurement is made, and the procedure for this reproducibility experiment. Data and statistical analysis, and the fitting of the turn-by-turn position data are discussed in detail. Also reported are the errors found in the data acquisition, how often the errors occur, how the errors are identified and removed from the dataset, their effect on the quality of the beam position measurement, and scenarios of how these errors manifest in the data acquisition. The resulting conclusions of the repeatability of the beam position measurement is based on the spread of fitting parameters fit to the turn-by-turn beam position data.
SLAC, Menlo Park, California
SSRL designed and built beam position electronics for its SPEAR3 storage ring. We designed the electronics, using digital receiver technology, for highly accurate turn by turn measurements of both the position and arrival time of the beam, allowing us to use this system to measure the betatron and synchrotron tunes of the beam. The dynamic range of the system allows us to measure the properties of the beam at currents ranging from those of single bunch injection to those of the full SPEAR stored beam. This paper discusses the architecture of the electronics, presents their performance specifications, and shows a range of applications of this system for accelerator physics experiments.
SLAC, Menlo Park, California
BNL, Upton, Long Island, New York
Life Imaging Technology, Palo Alto, California
For top-up injection it is important to understand the time evolution of the incident charge in the transverse and longitudinal coordinate systems. In SPEAR3, the injection system has a vertically-deflecting Lambertson septum with the injected beam entering ~13mm to the inside. The resulting large-amplitude betatron oscillations give rise to rapid filamentation followed by nominal radiation damping and in some cases non-linear x-y coupling. Similarly, in the longitudinal dimension, a mis-match in beam arrival time or energy can result non-linear beam dynamics and damped synchrotron motion. To the next order, any betatron, bunch length or energy spread mismatch will generate damped ‘quadrupole’ oscillations or even higher-order motion. In this paper we report on measurements of injection beam dynamics in the transverse and longitudinal coordinate systems using a fast-gated, image-intensified CCD camera and a Hamamatsu C5680 streak camera, respectively. The injection beam dynamics are shown to contain relatively complicated evolution in the x-y-z beam distributions that change with injection conditions and storage ring lattice configuration.
CERN, Geneva
A high resolution beam position monitor (BPM) electronics based on diode peak detectors has been developed at CERN. The circuit processes the BPM electrode signals independently, converting the short beam pulses into slowly varying signals which are digitized with high resolution ADCs operating in the kHz range. For large enough amplitudes the non-linear forward voltage of the diodes is compensated by a simple network using signals from single-diode and double-diode peak detectors. This contribution discusses the performance of the built prototype with beam in the CERN-SPS and comments on possible future applications of the technique.