ZTEC Instruments, Albuquerque
Modular oscilloscopes and digitizers, including those with embedded EPICS IOCs, provide powerful off-the-shelf solutions for accelerator controls and beamline data acquisition applications requiring fast sampling, high resolution and/or tight multi-channel synchronization. This presentation discusses features and capabilities of EPICS and non-EPICS LXI, VXI, PXI and PCI oscilloscopes and digitizers as they specifically relate to accelerator and beamline applications. Modular oscilloscopes and digitizers with on-board DSP and FPGAs provide the advanced waveform acquisition and analysis capabilities of benchtop instruments with the size and channel-density advantages of modular instruments. Instruments with on-board processing, such as those from ZTEC Instruments, enable real-time waveform math and waveform parameter analysis. Advanced triggering and multiple acquisition modes are other features found on some of today’s advanced modular instruments. Furthermore, instruments with embedded EPICS IOCs save users the time and money of developing their own EPICS drivers and display panels. Examples of specific accelerator applications using advanced modular instruments will be presented.
ELETTRA, Basovizza
Several diagnostic instruments for the FERMI@Elettra FEL, among them the Bunch Arrival Monitor (BAM) and the Cavity Beam Position Monitor (C-BPM), require accurate readout, processing, and control electronics. All systems must be also integrated within the main machine control system. The back-end platform, based on the MicroTCA standard, provides a robust environment for accommodating such electronics, including reliable infrastructure features. Two types of Advanced Mezzanine Cards (AMC) had been developed in-house and manufactured for meeting the demanding performance requirements. The first is a fast (160 MSps) and high-resolution (16 bits) Analog to Digital and Digital to Analog (A|D|A) Convert Board, hosting 2 A-D and 2 D-A converters controlled by a large FPGA (Virtex-5). The FPGA is also responsible for service and host interface handling. The latter board is Analog to Digital Only (A|D|O) Converter, derived from the A|D|A, with an analog front side stage made of four A-D converters. The overall systems’ architectures, together with the specific AMCs’ functionalities, are described. Results on performance measurements are also presented.
SLAC, Menlo Park, California
A new stripline beam position monitoring (BPM) readout and processing system was installed and successfully tested over a two-week period at the Accelerator Test Facility 2 (ATF2), in KEK, Japan during February 2010. The core analog processing board used in the system is a duplicate of that developed for, and in use at, the Linac Coherent Light Source (LCLS) at SLAC. The digitization, processing and control front-end were custom designed for ATF2 using a 14-bit 100-MHz VME digitizer and an EPICS Input/Output Controller (IOC) running on the VME controller. Control of the analog boards is via EPICS, which controls a serial-over-TCP/IP port server. Hardware for the readout of up to 14 BPMs with 3 spare analog boards was delivered. The goal of this installation was to provide ~<10 micron resolution, non-charge-dependent readout of the ATF2 electron beam with long-term gain stability compensation. These criteria were tested and successfully met. This design was found to be highly effective and to have many advantages, especially that it required minimal installation effort at ATF2.
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.
NewPath, Salt Lake City, Utah
We have derived algebraic expressions for the open-circuit voltage that is induced on a Rogowski coil, having imperfectly spaced turns, by a time-dependent current which passes through the aperture of the coil. The derivation of these expressions requires that the layer of the winding is thin, the number of turns is large, and the cross-section of the winding is uninform and rectangular. Examples are given in which these expressions are applied to determine the effects of the gap between the ends of the coil, as well as other irregularities in the spacing of the turns, on the position sensitivity–defined as the dependence of the induced voltage on the coordinates of the current. The results in these examples agree with those that others have obtained by numerical methods or measurements with Rogowski coils. This technique may be used to quickly define the design specifications which are required to satisfy a specific upper limit for the positional sensitivity.
NewPath, Salt Lake City, Utah
Others have shown that the voltages induced on one uniformly-wound toroidal coil and two sinusoidally-wound toroidal coils may be used to determine the current in a single filament and its coordinates. We have extended this technique to show that the voltages measured on a group of sinusoidally-wound toroidal coils may be used to approximate the distribution of current within their common aperture. This is possible because each measured voltage is proportional to the product of unique functions of the radial and azimuthal coordinates of each increment of the current [1,2]. We have developed matrix methods to determine the transverse distribution of the current and determined the sensitivity of these calculations to measurement errors. Shielded sinusoidally-wound coils with a precision of 0.02 cm have been prepared using rapid prototyping, and methods have been defined to prepare the next generation of these coils, which will have a precision of 0.001 cm, by using an engraving tool with the 4th axis of a vertical milling machine.
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.
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.
CERN, Geneva
The LHC Beam Loss Monitoring (BLM) system is one of the most complex instrumentation systems deployed in the LHC. In addition to protecting the collider, the system also needs to provide a means of diagnosing machine faults and deliver feedback of losses to the control room as well as to several systems for their setup and analysis. It has to transmit and process signals from over 4,000 monitors, and has nearly 3 million configurable parameters. In a system of such complexity, firmware reliability is a critical issue. The integrity of the signal chain of the LHC BLM system and its ability to correctly detect unwanted scenarios and thus provide the required protection level must be ensured. In order to analyze the reliability and functionality, a test bench has been developed that emulates different types of loss signals and monitors the performance and response of the FPGA-based data analysis firmware. This paper will report on the numerous tests that have been performed and on how the results are used to quantify the reliability of the system.
LBNL, Berkeley, California
A hardware system that acquires and stores a large buffer of bunch-by-bunch 16-bit data has been realized. A high resolution (up to 16-bit) analog-to-digital converter (ADC), or bank of ADCs, samples the analog signal at the bunch frequency. The digitized data is fed into a Field Programmable Gate Array (FPGA), which contains an interface to a bank of double data rate (DDR) SDRAM type memory. With appropriate data bus widths, the FPGA bursts the ADC data into the DDR SDRAM fast enough to keep up with the bunch-by-bunch ADC data continuously. The realized system demonstrates continuous data transfer at a rate of 1 GByte/sec, or 16-bit data at 500 MHz, into a 64MByte SDRAM. This paper discusses the implementation of this system and the future of this architecture for bunch-by-bunch diagnostics.
Agilent Technologies SA, Plan-les-Ouates
Agilent Technologies Inc., Loveland
Digital data acquisition in real time applications falls into two categories: digitizing a stream of data without missing a single sample point, and capturing a stream of triggered events without missing a single trigger. Maintaining these data streams over long periods requires an optimized combination of analog signal conditioning, and precise digitization, digital data reduction and high-speed data transfer. This paper describes suggested methods to reduce the amount of measurement data required, reduce the amount of that data that is to be transferred (to a measurement where possible), and then transfer this reduced data in the most rapid fashion. Our approach uses a combination of hardware, firmware and software elements that are designed to work together, optimizing performance and managing the data bottlenecks. New hardware standards and architectures are discussed that improve the capabilities of today's technologies, providing access to higher data and measurement flux. Applications presented in this paper include high trigger rate capture for beam steering and fill pattern monitoring in charged particle accelerators.