CERN, Geneva
The protection of the LHC equipment against beam-induced destruction is given by losses lasting up to three revolutions and longer losses. For the fast losses a passive system consisting of collimators, absorbers and masks is used. For the others an active system consists of beam loss monitors, a beam interlock system and the beam dump. The LHC protection requirements are different to other accelerators. The differences are mainly due to its energy, its stored beam intensity and its dimension. At the LHC top energy the beam intensity is about 3 orders of magnitude above the destruction limit of the superconducting magnet coils and 11 orders above their fast loss quench limit. These extreme conditions require a very reliable damage protection and quench prevention with a high mean time between failures. The numerous amounts of loss locations require an appropriate amount of detectors. In such a fail safe system the false dump probability has to be kept low to keep high operation efficiency. A balance was found between a reliable protection and operational efficiency. The main protection systems and beam instrumentation aspects of the measurement systems will be discussed.
IHEP Beijing, Beijing
As the upgrade project of Beijing Electron Positron Collider (BEPC), BEPCII will still serve both high energy physics experiments and synchrotron radiation applications. The storage ring of BEPCII consists of electron ring (BER), positron ring (BPR) and synchrotron radiation ring (BSR). Up to now, we have completed two stages run. The first stage run started on Nov. 13, 2006 by using conventional magnets instead of superconducting (SC) magnets in the interaction region (IR). The second stage operation started on Oct. 24, 2007 by using SC magnets and without BESIII detector. In this paper, we will present the progress of the BEPCII storage ring diagnostics system along with the BEPCII commissioning, such as how Libera BPM has been used for the BPR first turn measurement and the injection residual orbit research of BER; COD measurement can satisfy the resolution requirement for the beam-beam scan in the IR and for the slow orbit feedback; BCM can help us on the different injection pattern; and the TFB system is important to suppress the strong multibunch instabilities when the higher beam current run. The tune meters and the beam-loss monitors are also described in this paper.
ANL, Argonne
The Advanced Photon Source (APS) monopulse beam position monitor (BPM) system, designed to measure single- and multi-turn beam positions, is one of three BPM systems currently in use to measure and control both AC and DC orbit motions. Recently, one sector of the monopulse BPM system was upgraded by replacing its ca 1992 12-bit signal conditioning and digitizing unit (SCDU) with a field-programmable gate array (FPGA)-based system for signal processing. The system is comprised of a repackaging of the broadband rf receiver modules together with a VME Extensions for Instrumentation (VXI) module housing eight 14-bit digitizers and one FGPA. The system will be described in detail, including an overview of its new functionality, and performance will be discussed. Of particular interest is the noise floor, which will be contrasted with the previous system and with other systems in use at the APS.
Fermilab, Batavia
SLAC, Menlo Park, California
KEK, Ibaraki
A beam position monitor (BPM) upgrade at the KEK Accelerator Test Facility (ATF) damping ring is currently in progress, carried out by a KEK/FNAL/SLAC collaboration under the umbrella of the global ILC R&D effort. The upgrade consists of a high resolution, high reproducibility read-out system, based on analog and digital downconversion techniques, digital signal processing, also implementing a novel automatic gain error correction schema. The technical concept and realization, as well as preliminary results of the beam studies are presented.
CERN, Geneva
Wire scanners are instruments to measure the transverse beam profile. The measurement is performed by moving a thin wire across the path of the particle beam while monitoring the secondary particles. One of the limiting factor in application of wire scanners for high-intensity beams is the wire resistance to high temperature. In this work a heat flow equation for a carbon wire passing through a particle beam is solved. The equation contains modeling of wire heating induced by electromagnetic field of the beam and by electronic energy loss of the protons passing through the wire. The cooling processes considered are conduction, radiation, thermionic emission and sublimation enthalpy. Due to the equation nonlinearity a numerical approach based on discretization of the wire movement is used. An estimation of the wire sublimation rate is made. The model is tested on SPS and LEP data. An other limitation of a wire scanner application is a superconducting environment. The energy deposition in the magnet coils of downstream superconducting LHC magnets is estimated using Geant4 simulation package. In conclusions the limits of Wire Scanner operation on LHC beams are drawn.
Diamond, Oxfordshire
Top up is becoming more and more a standard mode of operation for synchrotron light sources. Although it brings a very stable source in terms of position and intensity, the regular injections potentially perturb the beam. In order to investigate the perturbation of the beam from imperfections of the injection kickers (i.e. non-closure of the bump), we use an X-ray pinhole camera equipped with a fast CMOS-sensor giving a rate of up to 3200 frames per second to monitor the image of the beam. The analysis of the observed beam size as well as position allows quantifying the perturbation from the kickers that can be seen on beamlines. In addition we compare the observed motion to bunch-by-bunch position data recorded in both vertical and horizontal planes, which reveals to be very complementary.
Fermilab, Batavia
Several complementary transverse emittance monitors have been developed and used at the Fermilab accelerator complex. These include Ionization Profile Monitors (IPM's), Flying Wires, Schottky detectors and a Synchrotron Light Monitor. Mechanical scrapers have also been used for calibration purposes. This paper describes the various measurement devices by examining their basic features, calibration requirements, systematic uncertainties, and applications to collider operation. A comparison of results from different kinds of measurements is also presented.
LBNL, Berkeley, California
At the Advanced Light Source (ALS), imperfections in the injection system plus electron diffusion result in storage ring RF bucket contamination. A Virtex-4 FPGA is used to generate a Direct-Digital Synthesized (DDS) sinewave waveform at the vertical betatron tune frequency, which is synchronously gated on or off at the 1.6MHz ring orbit frequency. Any pattern on/off/invert in 328 buckets by 2ns at the ring orbit frequency can be set. An embedded Power-PC core in the FPGA provides TCP access for control and monitoring via a remote PC running LabVIEW.
ANL, Argonne
A cw tune measurement system for the IPNS RCS is described. The pinger magnets are energized by a solid-state, transformer-coupled power supply operating at 30 Hz. In its present configuration, the power supply provides a 160-A pulse to a pair of series-connected, single-turn ferrite magnets. The magnet pair drive separately x- and y-plane orbit bumps in the h=1 beam. The dipole oscillations generated in the beam are sensed with pairs of split-can, "pie" electrodes. Raw signals from the H and V electrodes are carried on matched coax-cables to 0/180-degree combiners. The output difference signals are recorded with gated spectrum analyzers. Bunch circulation frequency varies from 2.21 MHz at injection to 5.14 MHz at extraction. With a fixed frequency span of 24 MHz, between 4 and 10 bunch harmonics and sidebands (SBs) are present in the difference spectra. Software has been developed to use the multi-harmonic SBs present over the span to improve the accuracy of the tune measurements. The software first identifies and then fits the multiple SBs to determine the tune. Sweeping the beam across the momentum aperture provides a method for measuring the chromaticity.