BNL, Upton, Long Island, New York
Four ionization profile monitors (IPMs) in RHIC measure vertical and horizontal beam profiles in the two rings. These work by measuring the distribution of electrons produced by beam ionization of residual gas. In 2007 a prototype of a new design was installed in the yellow ring. During the 2007-2008 run it proved to be almost completely free from backgrounds from rf coupling, electron clouds and x-rays from upstream beam loss. In 2009 two more IPMs of this new design were installed and in the 2010 shutdown we will complete installation of four identical IPMs. This paper describes the new IPMs and shows data from the 2010 beam run. The new IPMs have been extremely important in the commissioning of the RHIC stochastic cooling system.
LANL, Los Alamos, New Mexico
The goal of the design LANSCE-R Wire-Scanner Analog Front-end Electronics is to develop a high-performance, dual-axis wire-scanner analog front-end system implemented in a single cRIO module. This new design accommodates macropulse widths as wide as 700 us at a maximum pulse rate of 120 Hz. A lossey integrator is utilized as the integration element to eliminate the requirement for providing gating signals to each wire scanner. The long macropulse and the high repetition rate present conflicting requirements for the design of the integrator. The long macropulse requires a long integration time constant to assure minimum integrator droop for accurate charge integration, and the high repetition rate requires a short time constant to assure adequate integrator reset between macropulses. Also, grounding is a serious concern due to the small signal levels. This paper reviews the basic Wire Scanner AFE system design implemented in the cRIO-module form factor to capture the charge information from the wire sensors and the grounding topology to assure minimum noise contamination of the wire signals.
Diamond, Oxfordshire
JAI, Egham, Surrey
UCL, London
Royal Holloway, University of London, Surrey
This paper describes the design of a cavity BPM for use in single pass machines. The design was modelled using a number of different EM codes to allow cross comparison of the simulation results. Furthermore, in addition to existing designs, the geometry has been modified to introduce a frequency separation between the horizontal and vertical dipole signals, as well as a reduction of the sensitivity of the position monitor to the monopole sum signal. The next stage of this project will be the manufacture of a prototype for tests in the transfer path at Diamond Light Source.
Fermilab, Batavia
Fermilab is jointly developing capabilities in high gradient and high Q superconducting accelerator structures based on the 1.3 GHz TESLA technology. Based on an INFN/TESLA design, a wire-position-monitor (WPM) system is integrated to monitor cavity alignment and cold mass vibrations. The system consists of a reference wire carrying a 325 MHz signal, 7 stripline pickups (per cryomodule), and read-out electronics using direct digital signal down-conversion techniques. We present technical details of the system, and preliminary results on resolution and stability measured at a mock-up test stand.
Fermilab, Batavia
CERN, Geneva
In the context of the development of a high resolution BPM system for the CLIC Main Linac we present the design of a cavity BPM prototype. It consists of a waveguide loaded dipole mode resonator and a monopole mode reference cavity, both operating at 15 GHz, to be compatible with the bunch frequencies at the CLIC Test Facility. Requirements, design concept, numerical analysis, and practical considerations are discussed.
KEK, Ibaraki
Button-type beam position monitors for SuperKEKB rings have been designed. The RF characteristics such as beam response, trapped modes or wake functions have been simulated using 3-D E-M codes such as GdfidL and HFSS. The estimated instability threshold from the trapped modes was much higher than the radiation damping time. The prototype units have been tested in the prototype-antechambers installed in KEKB and KEK-PF BT line. The mechanical reliability and the beam responses are also reported.
Cockcroft Institute, Warrington, Cheshire
The University of Liverpool, Liverpool
Capacitive pick-ups for closed-orbit measurements are presently under development for an Ultra-low energy Storage Ring (USR) at the future Facility for Low-energy Antiproton and Ion Research (FLAIR). Low-intensity, low-energy antiprotons impose challenging demands on the sensitivity of the monitoring system. The non-destructive beam position monitors (BPMs) should be able to measure 107 particles and give sufficient information on the beam trajectory. This contribution presents the status of the BPM project development. Main goals of the investigation include optimization of the mechanical design and preparation of a narrowband signal processing system.
CERN, Geneva
The fast beam current transformers (FBCTs) for the Large Hadron Collider (LHC) were designed to provide bunch to bunch and turn by turn intensity measurements. The required bunch to bunch measurements together with a large machine circumference call for stringent control of the transmission bandwidth, droop and DC offsets in the front-end electronics. In addition, two measurement dynamic ranges are needed to achieve the required measurement precision, increasing the complexity of the calibration. This paper reports on the analysis of the measurement and calibration methods, discusses theoretical precision limits and system limitations and provides a comparison of the theoretical results with the real data measured during the LHC start-up.
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.
BNL, Upton, Long Island, New York
Throughout RHIC Run-9 (polarized protons) and Run-10 (gold), numerous modifications to the Baseband Tune (BBQ) system were made. Hardware and software improvements resulted in improved resolution and control, allowing the system to overcome challenges from competing 60 Hz mains harmonics, other spectral content, and other beam issues. Test points from the Analog Front End (AFE) were added and connected to diagnostics that allow us to view signals, such as frequency spectra on a Sr785 dynamic signal analyzer, in real time. Also, additional data can now be logged using a National Instruments DAQ. Development time using tune feedback to obtain full-energy beams at RHIC has been significantly reduced from many ramps over a few weeks, to just a few ramps over several hours. For many years BBQ was an expert-only system, but the many improvements allowed BBQ to finally be handed over to the Operations Staff for routine control.
SLAC, Menlo Park, California
Measurement of time-of-arrival or instantaneous longitudinal position is a fundamental beam diagnostic. We present results from a stripline transversal periodic coupler structure which forms the heart of a sub-ps beam timing detector. This filter structure approximates a sinx/x response in the frequency domain which corresponds to a limited pulse length response in the time domain. These techniques have been used extensively in beam feedback systems at 3 GHz center frequencies with operational single-shot resolutions of 200 fs[1]. We present a new design, based on a 11.424 GHz center frequency, which is intended to offer a factor of four improvement in time resolution. Two-dimensional electromagnetic simulation results are shown, and the design optimization approach leading to the final circuit implementation is illustrated. The prototype circuit has been fabricated on 60mil Rogers 4003 and lab frequency domain and time domain data are compared to the 2-D simulation results. Performance of the prototype circuit is shown with applicability to sub-ps beam measurements in LINAC and FEL applications.
ANL, Argonne
SLAC, Menlo Park, California
A large-solid-angle Cherenkov detector beam loss monitor has been built and tested as part of the Linac Coherent Light Source machine protection system (MPS). The MPS is used to protect the undulator magnets from high-energy electron beam loss that can lead to demagnetization. Lost primaries create a shower of secondary electrons that transit through the radiator medium. The radiator consists of an Al-coated plate of high-purity, fused silica, formed into a tuning fork geometry that envelopes the beam pipe preceding each undulator. The radiator transports Cherenkov photons via internal reflection through a tapered neck into a compact photomultiplier tube (PMT). A simple model based on line sources summed across image planes is used to calculate the radiator optical coupling efficiency etac as a function of the electron's transverse position. The results are compared for the case of normally incident electrons with a more detailed Monte Carlo random-walk simulation called RIBO. Both analytical and numerical models show etac to be relatively uniform over the full range of transverse positions in the radiator and to be a strong function of surface reflectivity.