YerPhI, Yerevan
Thermal sensors based on the vibrating wire principle are distinguished by high accuracy and stability. An important advantage of these sensors is that they produce a frequency signal that can be transferred large distances without disturbance. Original vibrating wire sensors and monitors for the measurement of beam transversal characteristics of charged-particle and photon beams are described. By means of these devices, measurements of an electron beam in the Yerevan synchrotron, a proton beam at PETRA (DESY), and a hard x-ray undulator beam at the APS (ANL) have been performed.
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.
ORNL, Oak Ridge, Tennessee
Taking Advantage of recent successes with the Laser Profile monitor, a new protottype is being built to use the laser wire as both a profile monitor and a slit for an emittance measuring device. This improved system takes advantage of the steering dipole magnet prior to ring injection of SNS such that only the recently stripped H0 protons continue forward to the emmitance device. In this way we hope to make an emittance device that is both parasitic to neutron production, and capable of accurate measurements during full power applications.
Bira, Albuquerque, New Mexico
National Instruments, Austin
LANL, Los Alamos, New Mexico
The design and test of a new beam-profile-wire-scanner actuator for the LANSCE* 800-MeV proton linear accelerator is described. Previous actuator implementations use open-loop stepper-motor control for position indexing. A fixed-frequency, fixed-duration pulse train is sent to the stepper motor driving the linear actuator. This has lead to significant uncertainties in position, mechanical resonances and electrical noise. A real-time, closed loop control system has been developed at tested for more repeatable and accurate positioning of beam sense wires. The use of real-time controller allows one to generate a velocity profile for precise, resonance-free wire position indexing. High radiation levels in the beam tunnel, dictate the use of an electro-magnetic resolver, typically, used in servo applications, as the position feedback element. Since the resolver is an inherently analog device sophisticated digital signal processing is required to generate and interpret the wave forms that the feedback mechanism needs for positioning. All of the electronic and computational duties are handled in one National Instruments compact RIO real-time chassis with FPGA.**
*Los Alamos Neutron Science Center
**Field Programmable Gate Array
CEA, Gif-sur-Yvette
In the IFMIF-EVEDA framework, a high deuteron beam intensity (125 mA - 9 MeV) accelerator will be built and tested at Rokkasho (Japan). The development of this accelerator is shared between France, Italy and Spain. France (CEA-Saclay) and Spain (Ciemat-Madrid) are responsible of the beam instrumentation from the RFQ to the beam dump. One of the most challenging detectors is the Beam Transverse Profile Monitor (BTPM), and the Saclay group decided to investigate such a monitor based on residual gas ionisation. In order to study the feasibility, we plan in a first step to built a prototype. This monitor use a high electric field to drive the products (electrons and ions) of ionisation to resistive micro-strips. At first sight, no amplification is necessary! This prototype will be tested in the IPHI high intensity (100 mA) proton beam at Saclay to answer this question in particular, and to check the feasibility in general.
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.
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.
Fermilab, Batavia
Monitoring the tunes of individual proton and antiproton bunches is crucial to understanding and mitigating the beam-beam effects in the Tevatron collider. To obtain a snapshot of the evolving bunch-by-bunch tune distribution a simultaneous treatment of all the bunches is needed. The digital tune monitor (DTM) was designed to fulfill these requirements. It uses a standard BPM as a pickup. The vertical proton monitor is installed and allows us to gain valuable operational experience. A major upgrade is underway to implement an automatic bunch-by-bunch gain and offset adjustment to maintain the highest possible sensitivity under real operational conditions. We present the concept of the DTM along with its technical realization as well as the latest experimental results. Major challenges from the design and operation point of view are discussed.