| Paper | Title | Page |
|---|---|---|
| PS01 | Real-Time Tune Measurements on the CERN Antiproton Decelerator | 99 |
|
||
| A novel system for real-time tune measurement during deceleration of a low-intensity particle beam is presented. The CERN Antiproton Decelerator decelerates low intensity (2×107) antiproton beams from 3.5 GeV/c to 100 MeV/c. Because of the eddy-currents in the magnets, a tune-measurement during a pause in the deceleration would not be representative. One must thus be able to measure the tune in real time during the deceleration. The low intensity of the antiproton beam prevents the use of standard Schottky techniques, and swept Beam Transfer Function (BTF) measurements are too slow. A system was therefore developed which uses an M-shaped power spectrum, exciting the beam in a band around the expected frequency of a betatron side-band. Excitation at the betatron frequency, where beam response is highest, is thus minimized and measurements of BTF, and therefore the tune, can be made with much reduced emittance blowup. | ||
| PS02 | Bench Test of a Residual Gas Ionization Profile Monitor (Rgipm)
Work supported by U.S. Department of Energy |
102 |
|
||
| An RGIPM has been designed, constructed and bench tested to verify that all components are functioning properly and that the desired resolution of about 50μm× rms can be achieved. This paper will describe some system details and it will compare observed results to detailed numerical calculations of expected detector response. | ||
| PS03 | Optical Bunch-By-Bunch Diagnostic System in KEK-PF | 105 |
|
||
| An optical bunch-by-bunch beam diagnostic system, which can detect oscillations of individual bunches in a multibunch operation, has been developed. The system is composed of a high-speed light shutter and an optical beamoscillation detector. The shutter that consists of a pockels cell and polarizers can be opened or closed in a bunch spacing time (2ns in KEK-PF) and it can select a light pulse corresponding to a certain bunch in a bunch train. The beam oscillation detector can detect oscillations of the pickedout bunch with a spectral analysis method. The diagnostic system has been installed in KEK-PF Beamline-21, and observed vertical oscillation of individual bunches due to an instability in the multi-bunch operation. | ||
| PS04 | Design of a Magnetic Quadrupole Pick-Up for the CERN PS | 108 |
|
||
| A quadrupole pick-up is sensitive to the quantity σ2x - σ2y, where σx and σy are the horizontal and vertical r.m.s. beam sizes. Since it is a non-invasive device, it is potentially very useful for matching and emittance measurements. A magnetic quadrupole pick-up has been developed for the CERN PS. By coupling to the radial component of the magnetic field around the beam, it was possible to eliminate the common-mode problem, which is usually a limiting factor in the use of quadrupole pick-ups. This paper presents the final pick-up design, which is the result of a series of simulations and test prototypes. The performance of the pick-up and its associated electronics is discussed. Preliminary results from the two pick-ups recently installed in the PS machine are also presented. | ||
| PS05 | Measurement of the Time-Structure of the 72 MeV Proton Beam in the PSI Injector-2 Cyclotron | 111 |
|
||
| The time-structure monitor at the last turn of the 72MeV Injector-2 cyclotron has been improved in order to meet the stringent time-resolution requirement imposed by the short bunch length. Protons scattered by a thin carbon-fibre target pass through a first scintillator-photomultiplier detector and are stopped in a second one. The longitudinal bunch shape is given by the distribution of arrival times measured with respect to the 50 MHz reference signal from the acceleration cavities. From a coincidence measurement, the time resolution of the detectors has been determined to be 51 ps and 31 ps fwhm. Longitudinal and horizontal bunch shapes have been measured at beam currents from 25μA to 1700μA. Approximately circular bunches were observed with diameter increasing with current. The shortest observed proton bunch length was 38 ps fwhm. | ||
| PS06 | Laser Profile Measurements of an H-Beam | 114 |
|
||
| A non-intercepting beam profile monitor for H--beams is being developed at Brookhaven National Lab. An H- ion has a first ionization potential of 0.75eV. Electrons can be removed from an H--beam by passing light from a near-infrared laser through it. Experiments have been performed on the BNL linac to measure the transverse profile of a 750keV beam by using a Nd:YAG laser to photoneutralize narrow slices of the beam. The laser beam is scanned across the ion beam neutralizing the portion of the beam struck by the laser. The electrons are removed from the ion beam and the beam current notch is measured. | ||
| PS07 | New Schottky-Pickup for COSY-Jülich | 117 |
|
||
| A new Schottky-pickup for the Cooler Synchrotron COSY at the Forschungszentrum Jlich was developed, tested and installed. The new pickup with four diagonally arranged plates replaces the two 1 m long Schottky-pickups used until now in COSY. The previous ones were removed mainly to gain space for new installations (e.g. rf-cavity, experimental devices), but also to increase the horizontal aperture. The available space for the new pickup is only 0.8 m. The pickup plates can be combined by means of relays to measure either in the horizontal or in the vertical plane. The pickup can also be used either as a sensitive broadband beam position monitor or as a tuneable narrowband pickup for Schottky-noise analysis with ultahigh sensitivity. A new method for resonant tuning of the Schottky-pickups for transversal measurements was developed. The differentially excited resonant circuitry enhances the sensitivity by about a factor of 30. The pickups are also used for dynamical tune measurements (tune meter) in the acceleration ramp. | ||
| PS08 | Current Transformers for GSI's KeV/u to GeV/u Ion Beams - An Overview | 120 |
|
||
| At GSI's accelerator facilities ion beam intensities usually are observed and measured with various types of current transformers (CT), matched to the special requirements at their location in the machines. In the universal linear accelerator (UNILAC), and the high charge state injector (HLI) as well, active transformers with 2nd-order feedback are used, while passive pulse CTs and two DC-CTs based on the magnetic modulator principle are implemented in the heavy ion synchrotron (SIS) and the experimental storage ring (ESR). In the high energy beam transfer lines (HEBT) the particle bunch extraction/reinjection is monitored with resonant charge-integrating types. Since more than 10 years number and significance of beam current transformers for operating GSI's accelerators have grown constantly. Due to increased beam intensities following the last UNILAC upgrade, transmission monitoring and beam loss supervision with CTs have become the main tools for machine protection and radiation security purposes. All CTs have been constructed and developed at GSI, since no commercial products were available, when solutions were needed. | ||
| PS09 | Transverse Beam Profile Measurements Using Optical Methods | 123 |
|
||
| Two different systems are currently under development at GSI's heavy ion facility to measure transverse beam profiles using optical emitters. At the GSI-LINAC for energies up to 15 MeV/u residual gas fluorescence is investigated for pulsed high current beams. The fluorescence of N2 is monitored by an image intensified CCD camera. For all ion species with energies above 50 MeV/u slowly extracted from the synchrotron SIS a classical viewing screen system is used. Three different target materials have been investigated and their behavior concerning efficiency, saturation and timing performance is evaluated. Both systems (will) use CCD cameras with a digital read out using the IEEE 1394 standard. | ||
| PS10 | Control and Data Analysis for Emittance Measuring Devices | 126 |
|
||
| Due to the wide range of heavy ion beam intensities and energies in the GSI linac and the associated transfer channel to the synchrotron, several different types of emittance measurement systems have been established. Many common devices such as slit/grid or dipole-sweep systems are integrated into the GSI control system. Other systems like the single shot pepper pot method using CCD-cameras or stand-alone slit/grid set-ups are connected to personal computers. An overview is given about the various systems and their software integration. Main interest is directed on the software development for emittance front-end control and data analysis such as evaluation algorithms or graphical presentation of the results. In addition, special features for improved usability of the software such as data export, project databases and automatic report generation will be presented. An outlook on a unified evaluation procedure for all different types of emittance measurement is given. | ||
| PS11 | Test of Different Beam Loss Detectors at the GSI Heavy Ion Synchrotron | 129 |
|
||
| For the sensitive process of slow extraction from a synchrotron a reliable control of the beam losses is needed. We have tested several types of particle detectors mounted at the extraction path of the SIS: A BF-tube for pure neutron detection, a liquid and a plastic scintillator detecting neutrons, gammas and charged particles and an Argon filled ionization chamber mainly sensitive to charged particles. While the count rate is quite different, the time evolution of all detector signals during the spill are similar, but the plastic scintillator has the highest dynamic range. This type is going to be used for beam alignment. | ||
| PS12 | Source Imaging with Compound Refractive Lenses | 132 |
|
||
| PS13 | A Zone Plate Based Beam Monitor for the Swiss Light Source | 133 |
|
||
| At the Swiss Light Source, a source imaging set-up is planned on a dedicated dipole magnet beam-line. A transmission Fresnel Zone Plate will be used to generate a demagnified image of the source at a photon energy in the 1.8 keV range. The image will be acquired by scanning a pinhole in the image plane. A diffraction limited spatial resolution of approximately 2 microns can be anticipated. The concept has the advantage of having no components operated in reflection, and no components inside the frontend. | ||
| PS14 | Microwave Pickups for the Observation of Multi GHz Signals Induced by the ESRF Storage Ring Electron Bunches | 136 |
|
||
| The length of the bunches stored in ESRF lies in the 30 ps to 120 ps range (FWHM). The observation of single bunch phenomena like transverse or longitudinal oscillations or bunch length variation requires the acquisition and analysis of signals at frequencies higher than 10 GHz. A set of microwave cavity pick ups operating at 10 GHz and 16 GHz together with the appropriate electronics has been implemented on the ESRF storage ring; it detects the wall currents on the vacuum chamber due to the electron beams circulation. We describe the design of these cavities, give the result and analysis of measurements performed with the pick ups and indicate how we plan to use these devices as beam diagnostics | ||
| PS15 | A New Wirescanner Control Unit | 139 |
|
||
| Wires scanners are standard instruments for beam size measurements in storage rings: A wire is crossing the beam at a given speed and the secondary emission current of the wire and/or the photomultiplier signals produced from Bremsstrahlung or particles scattered at the wire are recorded together with the wire positions. The control unit described here is based on a previous CERN design. It now has additional features: Triggered fast scans (1m/s) with a trigger uncertainty below ±30μs (mechanics + electronics) used at the TTF Linac and at the proton synchrotron DESY III, Slow scans (e.g. 50μm/s) for the TTF Linac, Positioning of the wire within ±3μm for tail scans at the storage rings PETRA and HERA, A 10.5MHz data acquisition rate for bunch-by-bunch acquisitions in the accelerators at DESY. Another important design goal was the compatibility with CERN scanners; it is foreseen to operate them at LHC with the new control unit. First measurements with the new control unit at TTF and HERA will be presented. | ||
| PS17 | Beam Size Measurement of the Spring-8 Storage Ring by Two-Dimensional Interferometer | 142 |
|
||
| Two-dimensional interferometer using visible synchrotron radiation was developed in order to measure beam sizes at a source point in a bending magnet of the SPring-8 storage ring. The theoretical background of this method is described in the framework of wave-optics. Assuming designed optics parameters, transverse emittance was evaluated from measured beam size. | ||
| PS18 | Planned X-Ray Imaging of the Electron Beam at the SPRING-8 Diagnostics Beamline BL38B2 | 145 |
|
||
| X-ray imaging observation of the electron beam is planned at the SPring-8 storage ring diagnostics beamline BL38B2 to evaluate small vertical emittance. The resolution target is 1 micron of electron beam size (1s). The synchrotron radiation from a dipole magnet source will be imaged by a single phase zone plate. Monochromatic X-ray with energy of 8keV will be selected by a double crystal monochromator. The magnification factor of the zoneplate is 0.27, and an X-ray zooming tube will be used as a detector to compensate for demagnification. | ||
| PS19 | Status of the Delta Synchrotron Light-Monitoring-System | 148 |
|
||
| Synchrotron radiation sources like DELTA need an optical monitoring system to measure the beam size at different points of the ring with high resolution and accuracy. An investigation of the emittance of the storage ring can also be done by these measurements. Scope of this paper is the investigation of the resolution limit of the different types of optical synchrotron light monitors at DELTA, a third generation synchrotron radiation source. At first the normal synchrotron light monitor is analysed. The minimum measurable electron beamsize at DELTA is about 80μm. Emphasis is then put on a special synchrotron light interferometer, developed for DELTA, which has been built up and tested. This interferometer uses the same beamline and can measure beamsizes down to about 8μm. So its resolution is about ten times better and sufficient for the expected small vertical beamsizes at DELTA. Measurements of the electron beamsize and emittance were done with both (synchrotron light monitor and interferometer) at different energies. The image processing system based on a PC Framegrabber generates a gaussian fit to the images from different synchrotron light-monitors and calculates the beamsizes and positions. An investigation of possible reasons of beam movements will be appended, because the theoretical values of the present optics are smaller than the measured emittance. | ||
| PS20 | Beam Diagnostic for the Next Linear Collider | 151 |
|
||
| The Next Linear Collider (NLC) is proposed to study e+-e--collisions in the TeV energy region. The small beam spot size at the interaction point of the NLC makes its luminosity sensitive to beam jitter. A mechanism for aligning the beams to each other which acts during the bunch-train crossing time has been proposed to maintain luminosity in the presence of pulse-pulse beam jitter. We describe a beam-beam deflection feedback system which responds quickly enough to correct beam misalignments within the 265 ns long crossing time. The components of this system allow for a novel beam diagnostic, beam-beam deflection scans acquired in a single machine pulse. | ||
| PS21 | Diagnostics for the Photon Injector Test Facility in Desy Zeuthen | 154 |
|
||
| A Photo Injector Test facility (PITZ) is under construction at DESY-Zeuthen. The aim is to develop and operate an optimized photo injector for future free electron lasers and linear accelerators. This concerns especially minimal transverse emittances and proper longitudinal phase space. The commissioning of the photo injector will take place in summer 2001. In the rst phase the energy of the produced electrons is about 5 MeV. A short description of the setup and beam parameters are given. Optimization of an electron gun is only possible based on an extended diagnostics system. The diagnostics system for the analysis of the transversal and longitudinal phase space will be described. It consists of a measurement system of the transversal emittance, a TV-based image measurement system, a streakcamera measurement facility, a spectrometer using a dipole magnet and further detectors. Problems of the measurement of the longitudinal phase space are discussed in detail. |