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| MOPP097 | Measurements on the Rf Cavity for the ALBA Storage Ring | impedance, coupling, storage-ring, vacuum | 781 | ||
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ALBA storage ring will use 6 ambient temperature nose cone HOM damped cavities tuned at 500 MHz, designed at BESSY and known as the EU cavity. A first one, manufactured by ACCEL, was delivered in 2007 to investigate on its behaviour. This paper describes the data collected during investigation. First, bead-pull measurements were performed to assess impedance, both on fundamental and high order modes. Emphasis was put on E011, due to the discrepancy between expected values and results for this mode. The vacuum bake-out and related pressure are shown. Then, the cavity was conditioned and observations were made on multipacting levels, conditioning time and surface temperatures. The latter were found inhomogeneous and leads are detailed to avoid local overheating.
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| MOPP135 | Vertical and Horizontal Test Results of 3.9 GHz Accelerating Cavities at FNAL | electron, resonance, instrumentation, alignment | 874 | ||
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The 3rd harmonic 3.9GHz accelerating cavity was proposed to improve the beam performance of the electron/positron linear accelerators. In the frame of a collaborative agreement, Fermilab will provide DESY with a cryomodule containing a string of four cavities. Several 9-cell Nb cavities were tested and they did reach accelerating gradient up to 24 MV/m almost twice more than design value of 14 MV/m. Two of these cavities are with new HOM couplers with improved design. In this paper we present all results of the vertical and horizontal tests.
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| MOPP157 | Critical Magnetic Field Determination of Superconducting Materials | coupling, pulsed-power, klystron, electromagnetic-fields | 919 | ||
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Using a 11.4 GHz, 50-MW, <1 μs, pulsed power source and a TE013-like mode copper cavity, we have been measuring critical magnetic fields of superconductors for accelerator cavity applications. This device can eliminate both thermal and field emission effects due to a short pulse and no electric field at the sample surface. A model of the system is presented in this paper along with a discussion of preliminary experimental data.
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| MOPP159 | Results of Vertical Tests for the KEK-ERL Single Cell Superconducting Cavities | acceleration, linac, insertion, superconductivity | 925 | ||
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The development of the superconducting cavities is indispensable for realizing the 5 GeV-class energy recovery linacs. The KEK-ERL cavity had been recently designed. Its features are the optimized cell shapes and adoption of the enlarged beampipes with eccentric-fluted structures. In order to confirm our cavity design, two types of single cell cavities had been fabricated. One is a center-cell type cavity, whose aim is a validation of the cell shape, and another is an end-cell type cavity, which has complex structure such as the eccentric-fluted beampipes. After applying a series of surface treatments, we had assembled the cavities and performed vertical tests at KEK D10 area. Promising results have been obtained. In this presentation, we will present the results of vertical tests for these cavities.
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| TUPC004 | The Diagnostic Line of Elettra Booster 100MeV Pre-injector | diagnostics, controls, bunching, booster | 1044 | ||
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In order to fully characterize the beam of the new 100MeV linac pre-injector for the Elettra Booster, a standard diagnostic set-up has been designed which includes strip line BPMs, scintillating screens and current transformers. During the initial tuning of the pre-injector, a thermo-ionic gun followed by a 500MHz pre bunching cavity, an S-band bunching structure and two LIL accelerating sections, some extra diagnostics have been used to get a deeper understanding of the pre-injector operating point. In particular some prototypes of the FERMI@elettra diagnostics, installed on the same booster pre-injector, have been used to better characterize the beam transverse and longitudinal beam axis. An improved resolution screen system, equipped with a YAG screen, has been used as well as a wideband longitudinal pick-up. The measurement results as well as the tuning procedure are here presented.
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| TUPC019 | A Retarding Field Detector to Measure the Actual Energy of Electrons Participating in E-cloud Formation in Accelerators | electron, controls, simulation, power-supply | 1086 | ||
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Electron cloud related phenomena can cause potentially detrimental effects on beam stability in many planned and under construction accelerators. The possibility to reduce such unwanted phenomena lies on the observation that, machine commissioning does reduce Secondary Electron Yield (SEY). Such SEY reduction (scrubbing) is due to the fact that electrons produced during e-cloud formation hit the accelerator wall, modifying their surface properties. ‘Scrubbing” has been studied only as a function of impinging electron dose but never as a function of the e-cloud electron energy. Simulations predict that the e-cloud is formed by electrons with very low energies (<50 eV). Given the potentially lower scrubbing efficiency for equal dose of very low energy electrons compared to medium energy one, it would be important to measure the actual energy of the electrons forming the cloud in real accelerators. For this reason we decided to construct an optimized retarding Field energy electrometer to be installed in accelerators. Here we will describe what solutions have been adopted during the design phase of such “home made” detector and some laboratory test will be showed and discussed.
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| TUPC020 | Development of Non-destructive Beam Current Measurement for the iThemba LABS Cyclotrons | cyclotron, diagnostics, proton, target | 1089 | ||
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The 200 MeV separated-sector cyclotron and its two 8 MeV solid-pole injector cyclotrons at iThemba LABS deliver beams of light and heavy ions, as well as polarized protons, with variable energy for nuclear physics research, a low-intensity proton 200 MeV beam for proton therapy and a high-intensity 66 MeV proton beam for neutron therapy and the production of radioisotopes. The intensity of the 66 MeV proton beam has recently been increased to 250 μA. This necessitated development of non-destructive beam diagnostic equipment, amongst others, for beam current measurement at various positions in the different beamlines. It was decided to determine the beam current by digitizing and analyzing the signals from capacitive phase probes on-line, instead of using more costly DC beam-current transformers. It was also important to design the phase probes with as low as possible inductance in their support to the diagnostic vacuum chambers to eliminate ringing in the probe signals. The design of the probes, the analyses of the probe signals and the results that were obtained with the equipment will be presented.
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| TUPC028 | Design and Construction of an Inductive Pick-up for Beam Position Monitoring in the TBL Line of the CTF3 | vacuum, linac, electron, monitoring | 1110 | ||
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In order to determine the beam position respect to the vacuum chamber, the IPU senses the azimuthal distribution of the beam image current flowing along its inner wall when a high frequency bunched beam passes through. The inner wall of the pick-up is divided into four electrodes, each of which forms the primary winding of a toroidal transformer. Therefore the beam image current component flowing through each electrode is transformed to a secondary winding connected to a pick-up output. The closer the beam is to the transformer electrode, the greater is the induced signal in its secondary winding. This basic sensing mechanism will allow to determine the beam position through the four transformers distributed orthogonally around the vacuum pipe. The bandwidth of the IPU and the amplifier is set above 200 MHz to let pass, with low distortion, the 20-140 ns pulse train signal induced from the beam. Also, its expected resolution at maximum current is 5μm. This paper reports on the design, construction as well as testing and calibration processes of two IPU prototypes. They will be installed in the Test Beam Line (TBL) of the 3rd CLIC Test Facility (CTF3) at CERN by Spring 2008.
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| TUPC035 | The Beam Position Monitor System of the J-PARC RCS | injection, controls, linac, vacuum | 1128 | ||
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The Beam Position Monitor (BPM) system of the J-PARC RCS has been fabricated, installed and operated successfully during the beam commissioning. There are 54 BPMs around the ring and most of them are placed inside steering magnets. The BPM is electro static type and it has four electrodes. A pair of electrode gives a linear response with diagonal cut shape and they were calibrated before their installation. The signal processing unit, which is equipped with 14-bit 14MSPS ADC and 600MHz DSP, has been developed for the system. In order to measure small signal, especially during the initial phase of the commissioning, careful design also done for cabling. The paper presents the current performance of the system.
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| TUPC043 | Towards Sub-micrometer Resolution of Single Bunch Strip Line BPM | feedback, vacuum, coupling, simulation | 1152 | ||
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A high resolution single bunch BPM set-up is designed based on a strip line pickup. One of the BPM modifications developed is a Difference-Sum BPM. In this BPM, each strip line signal is converted into a three 600MHz square wave burst in a cascaded irregular strip line coupler. The Difference and Sum bursts produced by a hybrid junction are detected in a pair of synchronous detectors. The synchronous detector reference signals, and single-sample ADC triggers are manufactured from the Sum burst. The set-up and features of this BPM are presented. The BPM resolution was measured using a KEK ATF beam. For a bunch intensity above 109 electrons the resolution is about 1 μm (for BPM effective aperture 1/5). With appropriate ADCs, this BPM can measure individual bunches at a rate of up to 50 MHz. The BPM latency to the ADC inputs is as low as 10 ns. High resolution and low latency together, make this BPM suitable for beam-based fast feedback/feed-forward systems.
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| TUPC044 | Towards Routine Operation of the Digital Tune Monitor in the Tevatron | proton, betatron, antiproton, feedback | 1155 | ||
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The digital tune monitor (DTM) was designed to measure bunch-by-bunch tunes in the Tevatron collider. 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. Once the system is shown to be able to cope with orbit changes and different bunch intensities in an automatic manner while reliably delivering data it will be expanded to measure horizontal proton as well as antiproton tunes. The motivation and the technical description of the DTM as well as the latest experimental results are presented. Major challenges from the design and operation point of view are discussed.
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| TUPC048 | Application of a 5 GSPS Analogue Ring Sampling Chip for Low-cost Single-shot BPM Systems | linac, single-bunch, electron, undulator | 1167 | ||
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In contrast to storage ring BPMs with continuously sampling ADCs, BPMs of single-bunch linear accelerators with typical repetition rates of 10-100Hz may also use waveform digitisers that sample just during a short interval when the bunch is passing the pickup. At PSI a 12-channel analogue sampling chip called "DRS" has been developed (*) that samples input signals in an array of 1024 capacitors per channel at up to 5GSPS. The acquisition can be stopped by a trigger signal and then the capacitor voltages of all 12 channels can be digitised with a single commercial external ADC at 33MSPS, achieving ~11 bit effective DC resolution and 450MHz max. bandwidth. The DRS chip was originally developed for low-cost digitization of 3000 detector signals of a particle physics experiment, using the PSI "VPC" VME64x FPGA board as digital back-end equipped with two PMC mezzanine modules with two DRS chips each. However, such DRS-based systems are also an attractive solution for inexpensive direct sampling and FPGA-based post-processing of suitable BPM pickup signals. This paper discusses BPM-related properties, limitations, possible improvements and measurement results of DRS-based electronics.
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*S. Ritt. The DRS chip: Cheap waveform digitizing in the GHz range, Nucl. Instrum. Meth. A518: 470-471, 2004. |
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| TUPC097 | Beam Diagnostics for the Prototype of the Cryogenic Storage Ring CSR | ion, diagnostics, electron, vacuum | 1287 | ||
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The Cryogenic Storage Ring CSR at the MPI-K Heidelberg will be a 35m circumference, electrostatic ring, which is mainly dedicated to Molecular- and Atomic Physics experiments. To reach the low pressures (10-15 mbar), which are necessary to achieve the required long liftetimes of the stored ions, the complete ring has to be operated at a temperature below 4K (2K in sections), which means, that it will be installed inside a large cryostat. To prove the novel cryogenics and vacuum concept of the CSR, we have built up a prototype, which is basically a segment of the CSR, housing an electrostatic ion trap. The ion trap is in the first instance used for vacuum measurements and equipment tests in the XHV range, in a later stage, it shall be an experimental facility of its own. Test operation of the Prototype is currently starting. Since the boundary conditions in the CSR are highly demanding for the beam diagnostics system, we have to perform some tests of the CSR diagnostics devices in our Prototype setup. The Poster will describe these devices and present first experimental results.
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| TUPC102 | Cooled Beam Diagnostics on LEIR | ion, electron, diagnostics, controls | 1296 | ||
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Electron cooling is central in the preparation of dense bunches of lead beams for the LHC. Ion beam pulses from the LINAC3 are transformed into short high-brightness bunches using multi-turn injection, cooling and accumulation in the Low Energy Ion Ring, LEIR. The cooling process must therefore be continuously monitored in order to guarantee that the lead ions have the required characteristics in terms of beam size and momentum spread. In LEIR a number of systems have been developed to perform these measurements. These include Schottky diagnostics, ionisation profile monitors and scrapers. Along with their associated acquisition and analysis software packages these instruments have proved to be invaluable for the optimisation of the electron cooler.
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| TUPC111 | Overview of the Diagnostics Systems of PETRA III | feedback, diagnostics, emittance, laser | 1323 | ||
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Since mid-2007, the existing storage ring PETRA at DESY is reconstructed towards a dedicated third generation hard x-ray light source operating at 6 GeV with 100 mA stored current. The reconstruction includes the total rebuilding of one-eights of the storage ring. In this part the FODO lattice of the arcs is replaced by double-bend achromat cells, resulting in straight sections for 14 insertion device beamlines. Damping wigglers with a total length of 80 m are installed to reduce the emittance down to the design value of 1 nm rad. In order to fully benefit from this low emittance, beam stability is a crucial issue. For the achievement of the required performance and to allow a safe machine operation a number of beam instrumentation is required. Here the diagnostics system for the electron beam is presented with special emphasis on the essential instruments, i.e. the high resolution BPM system, profile monitors, feedback systems, and the machine protection system.
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| TUPC139 | LLRF Electronics for the CNAO Synchrotron | controls, synchrotron, acceleration, proton | 1392 | ||
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The Italian National Centre for Oncological hAdrontherapy (CNAO) is undergoing its final construction phase in Pavia and will use proton and carbon ion beams to treat patients affected by solid tumours. At the hearth of CNAO is a 78 meters circumference synchrotron, capable of accelerating particle up to 400 MeV/u with a repetition rate of 0.4 Hz. Particle acceleration is done by a unique VITROVAC load RF cavity operating at a frequency between 0.3 and 3MHz and up to 3kV peak amplitude. In order to control this cavity a digital LLRF system has been designed at LPSC. It is based mainly upon Digital Signal Processors (DSPs), Field Programmable Gate Arrays (FPGA) and Direct Digital Synthesizers (DDS). The LLRF system implement both cavity control and beam control capabilities in a compact, remotely programmable and configurable, Ethernet controlled electronic module. It also allows an easy regulation loop tuning, thanks to an embedded acquisition system that stores all input and output signals during a given acceleration cycle. This paper describes the electronics architecture, lab measurements and test results obtained with the system coupled with the CNAO cavity.
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| TUPD003 | Upgrading the Fast Extraction Kicker System in SPS LSS6 | kicker, extraction, impedance, proton | 1437 | ||
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A fast extraction system, located in the LSS6 region of the CERN SPS accelerator, transfers 450 GeV/c protons, as well as ions, via the transfer line TI 2 towards the LHC. The system includes three travelling wave kicker magnets, all powered in series, energised by a single Pulse Forming Network (PFN) and terminated by a short circuit. The specification for the system requires a kick flattop of 7800 ns duration with a ripple of not more than ±0.5%. Recent measurements with beam show that the ±0.5% kick specification is achieved over the initial 7100 ns of the kick flattop; however the ripple over 7800 ns is ±0.7%. Electrical measurements have been carried out on each of the three magnets: these have been compared with the beam measurements and the contribution of each magnet to the detailed shape of the flattop kick has been determined. This paper reports the results of measurements and describes the plans to upgrade the system to fully meet the kick specification.
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| TUPP049 | Experimental Electron Cloud Studies in the CERN Proton Synchrotron | electron, vacuum, extraction, proton | 1655 | ||
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Indications for a beam-induced electron cloud build-up are observed since 2000 for the nominal LHC beam in the PS to SPS transfer line and during the last turns before ejection from the PS. A new electron cloud setup was designed, built, and installed in the PS. It contains shielded button-type pickups, a dipole magnet, a vacuum gauge, and a dedicated stripline electrode to experimentally verify the beneficial effect of electron cloud clearing electrodes. During the 2007 run, the electron cloud effect was also clearly observed in the PS and efficient electron cloud suppression has been obtained for negative and positive bias voltages on the clearing electrode. Here, we present electron cloud measurements with different filling patterns and bunch spacings in the PS.
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| TUPP050 | Electron Cloud Mitigation by Fast Bunch Compression in the CERN PS | extraction, electron, synchrotron, proton | 1658 | ||
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A fast transverse instability has been observed with nominal LHC beams in the CERN Proton Synchrotron (PS) in 2006. The instability develops within less than 1 ms, starting when the bunch length decreases below a threshold of 11.5 ns during the RF procedure to shorten the bunches immediately prior to extraction. An alternative longitudinal beam manipulation, double bunch rotation, has been proposed to compress the bunches from 14 ns to the 4 ns required at extraction within 0.9 ms, saving some 4.5 ms with respect to the present compression scheme. The resultant bunch length is found to be equivalent for both schemes. In addition, electron cloud and vacuum measurements confirm that the development of an electron cloud and the onset of an associated fast pressure rise are delayed with the new compression scheme. Beam dynamics simulations and measurements of the double bunch rotation are presented as well as evidence for its beneficial effect from the electron cloud standpoint.
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| WEPC144 | Test Results of the AC Field Measurements of Fermilab Booster Corrector Magnets | booster, quadrupole, dipole, sextupole | 2347 | ||
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Multi-element corrector magnets are being produced at Fermilab that will enable correction of orbits and tunes through the entire cycle of the Booster, not just at injection. The corrector package includes six different corrector elements - normal and skew orientations of dipole, quadrupole, and sextupole - each independently powered. The magnets have been tested during typical AC ramping cycles at 15Hz using a fixed coil system to measure the dynamic field strength and field quality. The fixed coil is comprised of an array of inductive pick-up coils around the perimeter of a cylinder which are sampled simultaneously at 100kHz with 24-bit ADC’s. The performance of the measurement system and a summary of the field results are presented and discussed.
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| WEPC145 | A Fast-sampling, Planar Array for Measuring the AC Field of Fermilab Pulsed Extraction Magnets | linac, extraction, dipole, booster | 2350 | ||
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A system employing a planar array of inductive pick-up coils has been developed for measurements of the rapidly changing dipole field in pulsed extraction magnets of the Fermilab MuCool project. The magnets are of C-type design, and have a peak field of 0.65 T during 8.33 millisecond half-sine pulse with 15 Hz repetition rate. The coils of the measurement system are fabricated on a single, 97.5 mm wide, 2-layer circuit board. The top layer of the circuit board has 15 unbucked coils distributed over its width. The bottom layer has a similar arrangement of coils, except each is bucked against the central winding to suppress the main dipole field and allow for more sensitive measurements of higher-order harmonics across the magnet mid-plane. The array of coils is simultaneously sampled at data rates of up to 100kHz with 10kHz bandwidth using 24-bit ADC’s. A detailed overview of the system and data analysis is presented, along with a characterization of results and system performance.
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| WEPD007 | Detection and Location of Electrical Insulation Faults on the LHC Superconducting Circuits during the Hardware Commissioning | diagnostics, instrumentation, cryogenics, quadrupole | 2413 | ||
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As part of the electrical quality assurance program, all superconducting circuits of the LHC have to be subjected to a (high) DC voltage, up to 1.9 kV DC, for the testing of the electrical insulation. Circuits with an insulation fault have to be repaired before powering. Fault location within a ± 3 m range over the total length of 2700 m has been achieved in order to limit the number of interconnection openings. In this paper, the methods, tooling, and procedures for the detection and location of electrical faults will be presented in view of the practical experience gained in the LHC tunnel. Three cases of faults detected and localized during the hardware commissioning phases of the LHC will be discussed.
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| WEPD016 | Electrical Quality Assurance of the Superconducting Circuits during LHC Machine Assembly | cryogenics, dipole, controls, quadrupole | 2440 | ||
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Based on the LHC powering reference database, all-together 1712 superconducting circuits have been electrically wired and interconnected in the various cryogenic lines of the LHC machine. Continuity, magnet polarity, and the quality of the electrical insulation have been the main objectives of the Electrical Quality Assurance (ELQA) activities during the LHC machine assembly. Another activity aimed at ensuring the coherence between the reference database on one side, and the polarity conventions used for beam simulation and magnetic measurements. With the assembly of the LHC now completed, the paper reviews the methods and procedures established for the ELQA, as well as the employed time and resources. The qualification results will be presented with the emphasis on the detected electrical non-conformities and their possible impact on the performance of the LHC machine.
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| THPC074 | Observation of Coherent Oscillations of Colliding Bunches at the Tevatron | proton, antiproton, collider, beam-beam-effects | 3158 | ||
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Commissioning of the new digital tune monitor (DTM) at the Tevatron made it possible to observe vertical dipole oscillations of individual bunches at any time during an HEP store. Since all the bunches have significantly different collision conditions, this device provides vast possibilities for investigation of coherent beam-beam effects. We present theoretical model and experimental observations of coherent beam-beam modes. Analysis of the DTM data and its agreement with theory are discussed.
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| THPC117 | Measurements and Analysis of Beam Transfer Functions in the Fermilab Recycler Ring Using the Transverse Digital Damper System | diagnostics, feedback, kicker, antiproton | 3254 | ||
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The Fermilab Recycler Ring Transverse Digital Damper System was designed to facilitate Beam Transfer Function measurements using a Network Analyzer connected to auxiliary system ports for timing and diagnostic purposes. The Digital Damper System has the capability for both open and closed loop measurements. The Beam Transfer Function measurements provide direct measurements of the machine impedance, beam stability, and beam parameters such as betatron tune and chromaticity. An overview of the technique is presented along with analysis and results from open and closed loop measurements in the Fermilab Recycler Ring.
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| THPC122 | Digital Signal Processing for the Multi-bunch LHC Transverse Feedback System | kicker, feedback, betatron, damping | 3269 | ||
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For the LHC a VME card has been developed that contains all functionalities for transverse damping, diagnostics and controlled bunch by bunch excitation. It receives the normalized bunch by bunch position from two pick-ups via Gigabit Serial Links (SERDES). A Stratix II FPGA is responsible for resynchronising the two data streams to the bunch-synchronous clock domain (40.08 MHz) and then applying all the digital signal processing: In addition to the classic functionalities (gain balance, rejection of closed orbit, pick-up combinations, one-turn delay) it contains 3-turn Hilbert filters for phase adjustment with a single pick-up scheme, a phase equalizer to correct for the non-linear phase response of the power amplifier and an interpolator to double the processing frequency followed by a low-pass filter to precisely control the bandwidth. Using two clock domains in the FPGA the phase of the feedback loop can be adjusted with a resolution of 10 ps. Built-in diagnostic memory (observation and post-mortem) and excitation memory for setting-up are also included. The card receives functions to continuously adjust its parameters as required during injection, ramping and physics.
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| THPC126 | Performance and Features of the Diamond TMBF System | feedback, damping, controls, single-bunch | 3281 | ||
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The Diamond Transverse Multibunch Feedback System (TMBF) comprises an in-house designed and built analogue frontend to select and condition the position signals for each bunch. This is combined with the Libera Bunch-by-Bunch system to digitise the signal and perform the relevant calculations before driving the output stripline kickers. As the electronics are based on an FPGA this has allowed us to implement several features in addition to the basic feedback calculations. We report on improvements to both the analogue and digital parts of the TMBF system, along with recent achievements in using the system for instability mode stabilisation and for tune measurement. Also we discuss the potential of the system and additional functionality we plan on introducing in the near future.
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| THPC133 | Layout and Simulations of the FONT System at ATF2 | kicker, extraction, simulation, feedback | 3300 | ||
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We describe the adaptation of a Feedback On Nano-second Timescales (FONT) system for the final focus test beam line ATF2 at KEK. This system is located in the ATF2 extraction line, and is mainly conceived for cancellation of transverse jitter positions originated in the damping ring and by the extraction kickers. This jitter correction is performed by means of a combination of feed-forward (FF) and fast-feedback (FB) beam stabilisation. We define optimal positions for the kicker and BPM pairs of the FONT FF/FB system, and estimate the required kicker performance and BPM resolutions. Moreover simulation results are presented.
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| THPC144 | A Beam Quality Monitor for LHC Beams in the SPS | extraction, dipole, luminosity, injection | 3324 | ||
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The SPS Beam Quality Monitor (BQM) system monitors the longitudinal parameters of the beam before extraction to the LHC to prevent losses and degradation of the LHC luminosity by the injection of low quality beams. It is implemented in two priority levels. The highest level is related to machine protection, e.g. verifying SPS-LHC synchronization and global beam structure. If the specifications are not met, the beam is dumped in the SPS before extraction. On the second level, individual bunch position, length and stability are checked for beam quality assessment. Tolerances are adapted to the mode of operation and extraction to the LHC can also be inhibited. Beam parameters are accessed by acquiring bunch profiles with a longitudinal pick up and fast digital oscilloscope. The beam is monitored for instabilities during the acceleration cycle and thoroughly checked a few ms before extraction for a final decision on extraction interlock. Dedicated hardware and software components implementing fast algorithms are required. In this paper the fast algorithms and their possible implementations are presented.
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| THPC148 | Interlock – the Machine Protection Function of Libera Brilliance | instrumentation, brilliance, electron, controls | 3336 | ||
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The basic task of Libera Brilliance is electron beam position measurement. A secondary, but no less important, task is machine protection. Libera Brilliance activates Interlock output when the beam position is outside predefined limits. The Interlock subsystem also activates when the analog-to-digital converters (AD) are saturated and the beam position is only virtually centered. AD converter saturation is detected in the multiplexed fast peak detectors using AD converter rate data. The Interlock is designed for fail-safe operation. Within the FPGA window, a comparator function is performed on the Fast Acquisition position data delivered at a 10 kHz rate. Comparison is done separately for X and Y positions. Limits and operation mode are settable through the CSPI library. To avoid manual resetting of the Interlock, logic output is designed as a monostable cell. The described circuitry has been successfully implemented and tested in both laboratory and accelerator environments.
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| THPP046 | Applicability of Stochastic Cooling in Small Electrostatic Storage Rings | ion, storage-ring, electron, kicker | 3464 | ||
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Several small electrostatic storage rings have been built or are being built for experiments in atomic and molecular physics. One example is the DESIREE double electrostatic storage ring* under construction at the Manne Siegbahn Laboratory. At the KEK electrostatic storage ring, electron cooling of 20 keV protons has been demostrated**. For heavy molecules, however, including bio-molecules, electron-cooling times are unrealistically long because of the low ion velocity and the correspondingly low electron energy which results in very small electron currents. For this reason, electron cooling is not foreseen for DESIREE. The rates of stochastic cooling, on the other hand, are at first glance unrelated to beam energy. Furthermore, the low particle numbers expected for many heavy molecules seem to make stochastic cooling attractive, theoretical rates being inversely proportional to particle numbers. In this paper, the rates of stochastic cooling for slow heavy particles are investigated with respect to, mainly, the bandwidths and signal strengths that can be expected at the low particle velocieties that are of interest at, e.g., DESIREE, and some numerical examples are presented.
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* P. Löfgren et al., these proceedings |
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| THPP051 | Stochastic Cooling in the Framework of the FAIR Project at GSI | antiproton, storage-ring, vacuum, cryogenics | 3479 | ||
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Stochastic cooling at FAIR will be one of the instruments to get cooled beams of rare isotopes and antiprotons for high resolution experiments. Stochastic cooling systems will be installed in the CR and RESR storage rings. The Collector Ring CR is a dedicated storage ring for the first step cooling of antiproton beams (3 GeV or β=0.97) produced at the antiproton production target, and of radioactive beams (740 MeV/u or β=0.83) prepared in the Super Fragment Separator. The pick-up and kicker systems have designs which allow very efficient cooling for both particle velocities. There will be different ring optical settings for optimum cooling of antiprotons or rare isotopes. Whereas the next cooling step for rare isotopes will be electron cooling, antiprotons will be accumulated in the RESR using a similar accumulation scheme which was formerly applied at the AA at CERN. The paper presents the CR and RESR system layouts and new hardware developments.
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| THPP120 | Measurements on an A/D Interface Used in the Power Supply Control System of the Main Dipoles of CNAO | dipole, synchrotron, power-supply, controls | 3638 | ||
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The CNAO (the Italian Centre of Oncological Hadrontherapy, near Pavia) is in its final step of construction and is about to be fully operative. It is based on a synchrotron that can accelerate protons up to 250MeV and carbon ions up to 400MeV/u for the treatment of patients. In this paper we describe an A/D interface, used in the power supply control system of the synchrotron main dipoles, called B-Train. The field is measured in a dedicated dipole connected in series with the sixteen ones of the synchrotron and is then fed back to the power supply. The field is obtained integrating and digitizing the voltage induced on a pickup coil inserted in the gap of the seventeenth dipole. The A/D interface under study is based on a 64-channel current to frequency converter ASIC, in CMOS 0.35 μm technology, followed by a counter and uses a recycling integrator technique. The digital signal obtained is then used to generate a feedback signal for control system of the dipoles power supply. We present the electronic structure, the lab measurements and the behavior for various setups of the A/D interface described.
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