| Paper | Title | Page |
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| PM01 | Position Monitoring of Accelerator Components as Magnets and Beam Position Monitors | 159 |
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| In third generation light sources a large amount of heat load from synchrotron radiation must be dissipated from the vacuum chamber. The synchrotron radiation hits the outer chamber wall and leads to a bending of the vacuum chamber. Due to the fact that very often beam position monitors are included into the vacuum chamber, they start to move with increased heat load onto the vacuum chamber. An inexpensive and precise method to monitor this movement has been tested at the Dortmunder Electron Test Accelerator (DELTA). Commercially available Linear Variable Differential Transformers (LVDTs) have been used. In addition it was possible to demonstrate that due to the vacuum chamber contact to quadrupole magnets the quadrupoles were moving with increasing beam current leading to a significant orbit drift. | ||
| PM02 | Signal Processor for Spring8 Linac BPM | 162 |
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| A signal processor of the single shot BPM system consists of a narrow-band BPF unit, a detector unit, a P/H circuit, an S/H IC and a 16-bit ADC. The BPF unit extracts a pure 2856MHz RF signal component from a BPM and makes the pulse width longer than 100ns. The detector unit that includes a demodulating logarithmic amplifier is used to detect an S-band RF amplitude. A wide dynamic range of beam current has been achieved; 0.01 ~ 3.5nC for below 100ns input pulse width, or 0.06 ~ 20mA for above 100ns input pulse width. The maximum acquisition rate with a VME system has been achieved up to 1kHz. | ||
| PM03 | Accuracy Of The LEP Spectrometer Beam Orbit Monitors | 165 |
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| At the LEP e+/e- collider, a spectrometer is used to determine the beam energy with a target accuracy of 10-4. The spectrometer measures the lattice dipole bending angle of the beam using six beam position monitors (BPMs). The required calibration error imposes a BPM accuracy of 1 æm corresponding to a relative electrical signal variation of 2×10-5. The operating parameters have been compared with beam simulator results and non-linear BPM response simulations. The relative beam current variations between 0.02 and 0.03 and position changes of 0.1mm during the fills of last year lead to uncertainties in the orbit measurements of well below 1μm. For accuracy tests absolute beam currents were varied by a factor of three. The environment magnetical field is introduced to correct orbit readings. The BPM linearity and calibration was checked using moveable supports and wire position sensors. The BPM triplet quantity is used to determine the orbit position monitors accuracy. The BPM triplet changed during the fills between 1 and 2μm RMS, which indicates a single BPM orbit determination accuracy between 1 and 1.5μm. | ||
| PM04 | Stripline Beam Position Monitors For "ELBE" | 168 |
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| At the Forschungszentrum Rossendorf (FZR), the superconducting electron linear accelerator ELBE is under construction. It will deliver an electron beam with an energy of up to 40 MeV at an average beam current of up to 1mA. The accelerator uses standing wave DESY type RF cavities operating at 1.3 GHz. A non-destructive system for the measurement of the beam position at about 30 locations is needed. To obtain the required resolution of 100μm, a system of stripline beam position monitors (BPM) is under design. | ||
| PM05 | Functionality Enhancement of the Multiplexing BPM System in the Storage of SRRC | 171 |
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| An extension of existing multiplex BPM electronics to provide capability for turn-by-turn beam position and phase advance measurement is implemented. The system can be configured as turn-by-turn beam position measurement or phase advance and coupling measurement. For turn-by-turn mode, the system performed four consecutive measurements of four BPM buttons. Data acquisition is synchronize with beam excitation. Turn-by-turn beam position is reconstructed by these four independent measurements. This system was named as pseudo-turn-by-turn beam position monitor system (PTTBPM). Resonance excitation of the stored beam and adopting lock-in techniques can measure betatron phase and local coupling. Design considerations of the system and preliminary beam test results are presented in this report. | ||
| PM06 | The Low Gap BPM System at ELETTRA: Commissioning Results | 174 |
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| Two Low Gap BPMs have been successfully installed at ELETTRA and have now completed the commissioning phase. The main purpose of these new devices is to provide stable beam position measurement, at sub-micron level, to monitor the stability of the light delivered to the Users. The improvements with respect to the normal BPM system have been obtained adopting both a new Low Gap BPM sensor and a new non-multiplexed BPM detector, the latter being developed in co-operation with the SLS diagnostic group at the PSI. Beside the Closed Orbit mode, thanks to the digitally selectable bandwidth, the new BPM detector can be operated also in the Turn-by-Turn mode and provide the position signal to feedback loops. In this paper we first briefly review the system architecture, describing its mechanical and electronic parts. Then, we present the digital BPM detector set-up used at ELETTRA and the associated firmware required by the four-channel BPM detector to guarantee performance over the full dynamic range. The BPMposition monitoring system is also described and its integration in the BPM system presented. Laboratory tests confirmed sub-micron resolution at 10kHz data rate. A series of beam based measurements have been performed in order to test this system and to verify the improvement in performance. The system is presently used in the control room as a powerful beam quality monitor; its extension to other Storage Ring straight sections is under evaluation. | ||
| PM07 | Orbit Control at the Advanced Photon Source
Work supported by the US Department of Energy |
177 |
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| The Advanced Photon Source (APS) began operation in 1995 with the objective of providing ultra-stable high-brightness hard x-rays to its user community. This paper will be a review of the instrumentation and software presently in use for orbit stabilization. Broad-band and narrow-band rf beam position monitors as well as x-ray beam position monitors supporting bending magnet and insertion device source points are used in an integrated system. Status and upgrade plans for the system will be discussed. | ||
| PM08 | Advanced Photon Source RF Beam Position Monitor System Upgrade Design and Commissioning | 180 |
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| This paper describes the Advanced Photon Source (APS) storage ring mono-pulse rf beam position monitor (BPM) system upgrade. The present rf BPM system requires a large dead time of 400 ns between the measured bunch and upstream bunch. The bunch pattern is also constrained by the required target cluster of six bunches of 7 mA minimum necessary to operate the receiver near the top end of the dynamic range. The upgrade design objectives involve resolving bunches spaced as closely as 100 ns. These design objectives require us to reduce receiver front-end losses and reflections. An improved trigger scheme that minimizes systematic errors is also required. The upgrade is in the final phases of installation and commissioning at this time. The latest experimental and commissioning data and results will be presented. | ||
| PM09 | Design of a Multi-Bunch BPM for the Next Linear Collider
Work supported by the US Department of Energy, contract DE-AC03-76SF00515 |
183 |
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| The Next Linear Collider (NLC) design requires precise control of colliding trains of high-intensity (1.4×1010 particles/bunch) and low-emittance beams. High-resolution multi-bunch beam position monitors (BPMs) are required to ensure uniformity across the bunch trains with bunch spacing of 1.4ns. A high bandwidth (~350 MHz) multi-bunch BPM has been designed based on a custom-made stripline sum and difference hybrid on a Teflon-based material. High bandwidth RF couplers were included to allow injection of a calibration tone. Three prototype BPMs were fabricated at SLAC and tested in the Accelerator Test Facility at KEK and in the PEP-II ring at SLAC. Tone calibration data and single-bunch and multi-bunch beam data were taken with high-speed (5Gsa/s) digitisers. Offline analysis determined the de-convolution of individual bunches in the multi-bunch mode by using the measured single bunch response. The results of these measurements are presented in this paper. | ||
| PM10 | A Logarithmic Processor for Beam Position Measurements Applied to a Transfer Line at CERN | 186 |
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| The transfer line from the CERN proton synchrotron (PS) to the super proton synchrotron (SPS) requires a new beam position measurement system in view of the LHC. In this line, the single passage of various beam types (up to 7), induces signals with a global signal dynamics of more than 100 dB and with a wide frequency spectral distribution. Logarithmic amplifiers, have been chosen as technical solution for the challenges described above. The paper describes the details of the adopted solutions to make beam position measurements, with a resolution down to few 10-4 of the full pickup aperture over more than 50 dB of the total signal dynamics. The reported performances has been measured on the series production cards, already installed into the machine and on one pickup in the transfer line. | ||
| PM11 | Injection Matching Studies Using Turn-By-Turn Beam Profile Measurements in the CERN PS | 189 |
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| The very small emittance beam needed for the LHC requires that the emittance blow-up in its injector machines must be kept to a minimum. Mismatch upon the beam transfer from one machine to the next is a potential source of such blow-up. The CERN PS ring is equipped with 3 Secondary Emission Grids (SEM-Grids) which are used for emittance measurement at injection. One of these has been converted to a multi-turn mode, in which several tens of consecutive beam passages can be observed. This allows the study of mismatch between the PS-Booster and the PS. This paper describes the instrument and experimental results obtained during the last year. | ||
| PM12 | The SPS Individual Bunch Measurement System | 192 |
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| The Individual Bunch Measurement System (IBMS) allows the intensity of each bunch in an LHC batch to be the measured both in the PS to SPS transfer lines and in the SPS ring itself. The method is based on measuring the peak and valley of the analogue signal supplied by a Fast Beam Current Transformer at a frequency of 40MHz. A 12 bit acquisition system is required to obtain a 1 % resolution for the intensity range of 5×109 to 1.7×1011 protons per bunch, corresponding to the pilot and ultimate LHC bunch intensities. The acquisition selection and external trigger adjustment system is driven by the 200MHz RF, which is distributed using a single-mode fibre-optic link. A local oscilloscope, controlled via a GPIB interface, allows the remote adjustment of the timing signals. The low-level software consists of a realtime task and a communication server run on a VME Power PC, which is accessed using a graphical user interface. This paper describes the system as a whole and presents some recent uses and results from the SPS run in 2000. | ||
| PM13 | Control Modules for Scintillation Counters in the SPS Experimental Areas | 195 |
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| The hardware used in the SPS Experimental Areas to control the beam instrumentation electronics and mechanics of the particle detectors is based on CAMAC and NIM modules. The maintenance of this hardware now presents very serious problems. The modules used to operate the Experimental Areas are numerous and older than 20 years so many of them cannot be repaired any more and CAMAC is no longer well supported by industry. The fast evolution of technology and a better understanding of the detectors allow a new equipment-oriented approach, which is more favourable for maintenance purposes and presents fewer data handling problems. VME and IP Modules were selected as standard components to implement the new electronics to control and read out the particle detectors. The first application implemented in this way concerns the instrumentation for the Scintillation Counters (formerly referred to as triggers). The fundamental options and the design features will be presented. | ||
| PM14 | LHC Beam Loss Monitors | 198 |
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| At the Large Hadron Collider (LHC) a beam loss system will be installed for a continuous surveillance of particle losses. These beam particles deposit their energy in the super-conducting coils leading to temperature increase, possible magnet quenches and damages. Detailed simulations have shown that a set of six detectors outside the cryostats of the quadrupole magnets in the regular arc cells are needed to completely diagnose the expected beam losses and hence protect the magnets. To characterize the quench levels different loss rates are identified. In order to cover all possible quench scenarios the dynamic range of the beam loss monitors has to be matched to the simulated loss rates. For that purpose different detector systems (PIN-diodes and ionization chambers) are compared. | ||
| PM15 | Sensitivity Studies with the SPS Rest Gas Profile Monitor | 201 |
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| During the SPS run in the year 2000 further test measurements were performed with the rest gas monitor. First, profiles of single circulating proton bunches were measured and the bunch charge progressively reduced, in order to determine the smallest bunch intensity which can be scanned under the present operating conditions. The image detector in this case was a CMOS camera. Using a multi-anode strip photo-multiplier with fast read-out electronics, the possibility to record profiles on a single beam passage and on consecutive turns was also investigated. This paper presents the results of these tests and discusses the expected improvements for the operation in 2001. Moreover, the issue of micro channel plate ageing effects was tackled and a calibration system based on electron emission from a heating wire is proposed. The gained experience will be used for the specification of a new monitor with optimised design, to be operated both in the SPS and in the LHC. | ||
| PM16 | The Measurement and Optimisation of Lattice Parameters on the ISIS Synchrotron | 204 |
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| The ISIS Synchrotron accelerates a high intensity proton beam from 70 to 800 MeV at 50 Hz. Recent hardware upgrades to the diagnostics, instrumentation and computing have allowed turn by turn transverse position measurements to be made. A special low intensity beam can also be injected for detailed diagnostic measurements. The analysis of such data at many points around the ring has allowed the extraction of lattice parameters. This information will have significant application for improved beam control. The methods of analysis as well as some applications for setting up and optimising the machine are described in this paper. Future plans and relevance for high intensity performance is also given. | ||
| PM17 | First Beam Tests for the Prototype LHC Orbit and Trajectory System in the CERN-SPS | 207 |
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| The first beam tests for the prototype LHC orbit and trajectory system were performed during the year 2000 in the CERN-SPS. The system is composed of a wide-band time normaliser, which converts the analogue pick-up signals into a 10 bit position at 40MHz, and a digital acquisition board, which is used to process and store the relevant data. This paper describes the hardware involved and presents the results of the first tests with beam. | ||
| PM18 | Beam Diagnostics for Low-Intensity Radioactive Beams | 210 |
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| In order to perform imaging, profiling and identification of low intensity (Ibeam<105 pps) Radioactive Ion Beams (RIB), we have developed a series of diagnostics devices, operating in a range of beam energy from 50 keV up to 8 MeV/A. These characteristics do them especially suitable for ISOL RIB facilities. | ||
| PM19 | The Dynamic Tracking Acquisition System for DAΦNE e+/e--Collider | 213 |
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| The goal of this paper is to describe the dynamic tracking acquisition system implemented for the DAΦNE e+/e--collider at LNF/INFN. We have been using the system since last year and it has been possible to collect useful information to tune-up the machine. A four-button BPM is used to obtain the sum and difference signals in both the transverse planes. The signals are acquired and recorded by a LeCroy LC574A oscilloscope with the capability to sample the input waveforms using a beam synchronous external clock generated by the DaFne Timing System. The start of acquisition is synchronised to a horizontal kick given by an injection kicker. After capturing up to 5000 consecutive turns, data are sent through a GPIB interface to a PC, for processing, presentation and storage. A calibration routine permits to convert voltage data to millimeters values. The acquisition and control program first shows the decay time in number of turns. Then it draws a trajectory in the phase space (position and speed) in both the transverse planes. To do this the software builds a data vector relative to a second "virtual" monitor advanced by 90 degrees. This is done by two alternative ways: applying the Hilbert transform or using the transport matrix method. Examples of data acquired during the collider tune-up are shown. | ||
| PM20 | A High Dynamic Range Bunch Purity Tool | 216 |
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| The European synchrotron radiation facility uses a stored electron beam in order to produce x-rays for the study of matter. Some experiments make use of the time structure of the x-ray beam which is a direct reflection of the time structure in the electron beam itself. Avalanche photo-diodes have been used in an x-ray beam in a photon counting arrangement to measure the purity of single or few bunch filling modes. Conventional techniques measuring the photon arrival times with a time to analogue converter (TAC) achieve dynamic ranges in the 10-6 range. We report here the use of a gated high count rate device achieving a measurement capability of 10-10. Such high purity filling modes are required in synchrotron light sources producing x-ray pulses for experiments looking at very weak decay signals as seen in M”ssbauer experiments.. | ||
| PM21 | DSP and FPGA Based Bunch Current Signal Processing | 219 |
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| The current in electron storage rings used as synchrotron light sources must be measured to a very high precision in order to determine the stored beam lifetime. This is especially so in high-energy machines in which the lifetime may be very high. Parametric current transformers (PCT) have traditionally been used to measure the DC or average current in the machine, which offer a very high resolution. Unfortunately these do not allow the different components of a complex filling pattern to be measured separately. A hybrid filling mode delivered at the ESRF consists of one third of the ring filled with bunches with a single highly populated bunch in the middle of the two-thirds gap. The lifetime of these two components may be very different. Similarly the two components are injected separately and can be monitored separately using a fast current transformer (FCT) or an integrating current transformer (ICT). The signals from these devices can be analysed using high speed analogue to digital converters operating at up to 100MHz and digital signal processing (DSP) techniques involving the use of field programmable gate arrays (FPGAs) in order to process the continuous data stream from the converters. |