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.
I-Tech, Solkan
SOLEIL, Gif-sur-Yvette
Libera Photon is the new Photon Beam Position Processor (PBPM) from the Instrumentation Technologies. First measurements on real beam have been done at SOLEIL Synchrotron. The module was connected to a PBPM installed on the DIFFABS bending magnet beam line. Three different beam position experiments were done: measurement of position at beam bump (± 500 μm), beam current dependence and filling pattern dependence. Measurements were done with internal BIAS voltage source set to -70 V. Measured current was in the range up to 250 μA on the sensor. Measurements were done on standard 100 kS/s, 10 kS/s and 10 S/s data flows with different bandwidths. The article discusses the results and consequential improvements of the device.
BNL, Upton, Long Island, New York
Two most widely used BPM systems (manufactured by Bergoz and Instrumentation Technologies) implement switching technique to eliminate drifts caused by change in a channel gain. High stability is achieved by an alternative routing of signals from all pick-up electrodes through the same chain. In this paper we propose a different approach of separating signals in the frequency domain, which is based on advances of digital signal processing allowing identical gains for the separate frequencies. Experimental set-up and results are presented. Practical realization of the beam position monitors is also discussed.
ANL, Argonne
LBNL, Berkeley, California
Time-correlated single-photon counting (TCSPC) techniques have been used for bunch purity measurement since the Advanced Photon Source started operations. Over the past three years, improvements made in the monitor have increased the signal-to-noise ratio and dynamic range to above 10 billion. Recently, improvements of the timing resolution of TCSPC to < 50 ps FWHM allowed us to measure the longitudinal profile of individual bunches in the APS storage ring. The profile monitor uses a visible-light single-photon avalanche photodiode (SPAD) and a PicoHarp 300 TCSPC unit. Due to its robustness, the system operates continuously and measures the average longitudinal profile of the stored beam, updating the process variables for bunch phases and bunch lengths in intervals less than 30 seconds. In a third application, using a TCSPC x-ray detector with an x-ray wire scanner in the monochromatic beam of the diagnostics undulator, measurements of transverse profiles of individual bunches can be completed in less than 30 minutes. Since the beam sizes and phases are dependent on the bunch charge, these online tools will provide users with valuable information performing timing experiments.
Cockcroft Institute, Warrington, Cheshire
The University of Liverpool, Liverpool
For beam profile monitoring applications where low beam perturbation together with bi-dimensional imaging is required, ionization monitors based on neutral gas-jet targets shaped into a thin curtain are an interesting option. When integrated in ultra-high vacuum systems, such as in the Ultra-low energy Storage Ring (USR), where local vacuum preservation is of primary concern, such systems present severe difficulties linked to the creation and proper shaping of a high quality gas-jet curtain. In this contribution, investigations into the generation and evolution of the jet with the Gas Dynamics Tool (GDT) software and purpose-written C++ analysis modules are presented. By means of extensive numerical analysis, the advantages of a novel nozzle-skimmer system in terms of curtain quality are summarized as compared to traditional axisymmetric gas-jet creation and curtain shaping by means of scrapers. It is also shown that variable nozzle-skimmer geometries allow for modifying the gas-jet characteristics in a wide range, including jet splitting and local density modulation. Finally, the layout of a test stand that will be used for an experimental benchmark of these studies is shown.
ANL, Argonne
The Advanced Photon Source (APS) storage ring rf beam position monitors (BPMs) are impacted by the presence of beam-excited transverse electric (TE) modes. These modes are excited in large-aperture vacuum chambers and become trapped between the bellow end flanges. The TE modes are vertically oriented and are superimposed on the TEM beam position signals, corrupting the BPM measurements. Erroneous step changes in beam position measurements and systematic intensity dependence in the vertical plane have been traced to these modes, placing a fundamental limitation on vertical beam position stabilization. Experiments were conducted suppressing these modes on a test vacuum chamber. These experiments were simulated with MAFIA and Microwave Studio, confirming experimental results. We will describe the measurements, simulations, and prototype test results.
I-Tech, Solkan
ESRF, Grenoble
The lifetime of the electron beam in a Synchrotron Light Source is an important parameter. Its precise measurement within a short time is an essential tool to evaluate properties and stability of a storage ring. In some cases, for example during short gas outbursts in the UHV vacuum chamber leading to rapid lifetime drops, it can be used as a useful diagnostic tool as well. Traditionally, dedicated PCTs (Parametric Current Transformers) are mostly used for this purpose. The idea to use Libera Brilliance Beam Position Processor instead came after the excellent quality of its sum signal was observed. Moreover, the measurement accuracy is greatly increased by averaging the lifetime measurements of all the individual stations, bearing in mind that there are typically more than hundred BPMs positioned around the ring. First measurements were performed on ESRF, showing very good performance potential. The article discusses the measurements, their results, the comparison with more classical methods, and the implementation of this feature in the Libera Brilliance software.
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.
CELLS-ALBA Synchrotron, Cerdanyola del Vallès
Beam position monitors (BPM) characterization has been widely studied at ALBA Synchrotron Light Source. Special care has been taken on the analysis of their electrical offset in order to achieve submicron beam stabilities. This paper shows the results of the BPMs offset study for Booster and Storage Ring. The electrical effect of the different vacuum vessels housings the BPMs is also reported.
Bira, Albuquerque, New Mexico
IUCMB, Bloomington, Indiana
A four-channel magnet-power-supply ramp controller has been designed and deployed at the new ALPHA (Advanced Electron Photon Facility) at the IUCMB (Indiana University Center for Matter and Beams). The first application is a power-supply controller; however, the system is a versatile arbitrary voltage-waveform generator with full DAQ (data acquisition) capabilities that can be used in a variety of beam instrumentation settings. The real-time controller can generate four arbitrary, independently-triggerable ramp profiles. A normalized wave-form array is encoded as a Process Variable array and is uploaded and stored by the real-time controller as required. Each ramp array is clocked out to a 16-bit DAC (Digital to Analog Converter) via a DMA FIFO and built-in FPGA. The duration of the waveform is programmable with a minimum time resolution of 20 usec between profile values. Four bipolar DACs have an output range of ± 10V. Eight digital I/O control bits are allocated for each control channel. Typically, these bits are used to monitor and control the power-supply operational state. The control-system interface uses the EPICS Channel-Access server accessible on Labview RT 2009.
NSRRC, Hsinchu
Taiwan Photon Source (TPS) is a 3 GeV synchrotron light source which being in construction at NSRRC. Designs of various diagnostics are undergoing and will deploy in future to satisfy stringent requirements of TPS for commissioning, operation, and top-off injection. Design of the diagnostics for beam intensity observation, trajectory and beam positions measurement, destructive profile measurement, synchrotron radiation monitors, beam loss monitors, orbit and bunch-by-bunch feedbacks, filling pattern, etc. are in final design phase. Details of current status and implementation of the planned beam instrumentation system for the TPS will summary in this report.