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| MPPE071 | Einstein's General Relativity Effects on Beam Dynamics in a Storage Ring | storage-ring, ground-motion | 3834 | ||
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Funding: The work is supported by National Science Foundation of China under Grant No. 10475094. |
In this paper we will discuss Einstein's tide force predicted by Einstein's general relativity, how the new tide force would affect the beam orbits in a storage ring, and how to pick up and recognize it from the beam signals in a storage ring. The result shows this effect can be accumulated by the charged particle beam in a storage ring, it is a very interesting result. |
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| MPPP002 | Stochastic Cooling Electrodes for a Wide Velocity Range in the CR | impedance, kicker, coupling, antiproton | 799 | ||
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The CR storage ring is part of the FAIR project at GSI. It serves as a first stage of stochastic cooling for secondary rare isotopes at v/c=0.83 as well as for antiprotons at v/c=0.97. To avoid the installation of dedicated structures for each kind of beam, electrodes have been developed which are usable for both beams. They are based on slotline structures mounted perpendicular to the beam. They are shorted at the ends, and their signal is extracted by two striplines on the rear side, placed a quarter wavelength away from the open ends. The width of the structures can be adjusted to the initial betatron oscillation amplitudes. Their length is 24 mm, and the signal from many of these structures mounted in a row can be combined. The signal combination can be matched to the different beam velocities. The paper shows results from field calculations, prototype tests, and estimates of the signal combination efficiency. The beam impedance of the novel structures is compared with the superelectrodes applied in the former CERN AC and with the slow-wave structures currently installed in the FNAL Debuncher.
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| MPPT024 | Rotating Coil Magnetic Measurement System and Measurement Results of Quadrupole Prototype for BEPCII Storage Ring | quadrupole, multipole, dipole, storage-ring | 1844 | ||
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A normal quadrupole prototype magnet with 266-mm long, 105-mm aperture has been designed and fabricated by IHEP. Total of 88 quadrupole magnets are under fabrication. The multipole components, magnetic field gradient and transfer function of the quadrupole magnets were measured in September 2004, using an updated measurement system, which includes a rotating coil measurement system and a Hall probe measurement system. This paper mainly describes the updated harmonic coil magnetic field measurement system and provides the measurement results for BEPC II quadrupole magnets.
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| TOAC003 | Stochastic Cooling for Bunched Beams | ion, synchrotron, kicker, heavy-ion | 310 | ||
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Funding: Work performed under the auspices of the U.S. DOE. |
A longitudinal stochastic cooling system for RHIC is under construction and partial commissioning is planned for the upcoming run. The state of the system and future plans are discussed. |
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| TPAE060 | Planned Enhanced Wakefield Transformer Ratio Experiment at Argonne Wakefield Accelerator | laser, simulation, electron, linac | 3487 | ||
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Funding: U.S. Department of Energy. |
In this paper, we present a preliminary experimental study of a wakefield accelerating scheme that uses a carefully spaced and current ramped electron pulse train to produce wakefields that increases the transformer ratio much higher than 2. A dielectric structure was designed and fabricated to operate at 13.625 GHz with dielectric constant of 15.7. The structure will be initially excited by two beams with first and second beam charge ratio of 1:3. The expected transformer ratio is 3 and the setup can be easily extend to 4 pulses which leads to a transformer ratio of more than 6. The dielectric structure cold test results show the tube is within the specification. A set of laser splitters was also tested to produce ramped bunch train of 2 - 4 pulses. Overall design of the experiment and initial results will be presented. |
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| TPAP008 | Measurements of the LHC Collimator Impedance with Beam in the SPS | impedance, betatron, collimation, vacuum | 1132 | ||
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The transverse impedance of the LHC collimators will likely dominate the overall transverse impedance in the LHC at high energies and potentially limit the maximum intensity. A prototype collimator was recently tested in the SPS. Small, but significant tune shifts depending on the collimator position have been observed using different independent high resolution tune measurement methods. In addition trapped modes predicted from numerical simulation at the ends of the collimator jaws have been identified by bench measurement techniques as well as with the beam. We present a description of the measurements and an analysis of the results.
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| TPAT086 | Enhanced Optical Cooling of Particle Beams in Storage Rings | undulator, kicker, betatron, radiation | 4179 | ||
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In this scheme undulators are installed in straight sections of a storage ring at distances determined by a phase advance 2pπ+π between first and second undulators and 2π between next undulators, where p=1,2,3.. . UR emitted in the first undulator pass through an optical system with movable screens 1,2 in the image plane of the particle beam. If screens let pass the UR then the past UR is amplified and pass through the second and next undulators together with the particle. Every particle loses its energy in the overlapped fields of the amplified UR and these undulators. Motion of screens in the optical system leads to particle energy losses in second and following undulators similar to losses in moving targets T1,2 in the schemes of enhanced ion cooling.* Energy losses are accompanied by a decrease of both energy spread and amplitudes of betatron oscillations that is enhanced cooling if, at first, the moving screen 2 will produce conditions of the energy loss for higher energy particles. When the screen 2 will open image of all particles the system must be closed and then the cooling process can be repeated*.
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*physics/0404142. |
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| TOAD002 | Novel Tune Diagnostics for the Tevatron | antiproton, proton, betatron, injection | 140 | ||
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The Tevatron collides protons and antiprotons in the same beam pipe. This poses a challenge in the measurement of tunes for both species simultanously because of the possibility of signal contamination from the other species. On top of this, since both beams are in the same beam pipe, tunes of individual bunches are also important because tune shifts from the beam-beam effect affects each bunch differently. Three different tune diagnostics used in the Tevatron will be discussed in this paper: 1.7GHz Schottky pickups, 21.4 MHz Schottky pickups and 27 kHz baseband pickups. These pickups look at the tune spectrum at different frequency bands and provide useful physics information for each frequency regime.
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| TOPC004 | Tevatron Beam Position Monitor Upgrade | antiproton, proton, injection, controls | 410 | ||
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Funding: Operated by Universities Research Association Inc. under Contract No. DE-AC02-76CH03000 with the United States Department of Energy. |
The Tevatron Beam Position Monitor (BPM) readout electronics and software have been upgraded to improve measurement precision, functionality and reliability. The original system, designed and built in the early 1980s, became inadequate for current and future operations of the Tevatron. The upgraded system consists of 960 channels of new electronics to process analog signals from 240 BPMs, new front-end software, new online and controls software, and modified applications to take advantage of the improved measurements and support the new functionality. The new system reads signals from both ends of the existing directional stripline pickups to provide simultaneous proton and antiproton position measurements. Measurements using the new system are presented that demonstrate its improved resolution and overall performance. |
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| TPPT041 | RF Tuning and Fabrication Status of the First Module for J-PARC ACS | coupling, linac, factory, vacuum | 2684 | ||
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J-PARC Linac starts with 180-MeV SDTL temporary, and it is upgraded to 400-MeV with 21 ACS (Annular Coupled Structure) modules and two ACS bunchers and two debunchers. First buncher module is under fabrication, and second buncher and a few accelerating modules are also planed until FY2006. The first ACS module consists of two 5-cells ACS tanks and a 5-cells bridge cavity for the buncher module. Three RF tuners are installed to the bridge cavity for fine RF tuning. An operating frequency should be tuned to 972 MHz within the fine-tuning range before a brazing process in a factory. The tuning procedure has been studied with RF simulation analysis and cold-model measurements for ACS and bridge cells. This paper describes RF tuning results, fabrication status and related development items.
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| TPPT058 | First Tests of the Superconducting CH-Structure | simulation, resonance, coupling, proton | 3414 | ||
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Funding: GSI, BMBF contr. No. 06F134I, EU contr. No. EFDA/99-507ERB5005, CT990061 and RII3-CT-2003-506395. |
The Crossbar-H-type CH-structure is a new H-mode drift tube-structure operating in the H11-mode. Due to its mechanical rigidity room temperature as well as superconducting cavities can be realized. The superconducting CH-structure has been developed at the IAP in Frankfurt, Germany. To prove the promising results obtained by simulations a 19-cell, 352 MHz (beta=0.1) prototype cavity has been designed and built. This is the first superconducting low energy multi-cell cavity. We present the first cold tests of the cavity which have been performed in the cryogenic laboratory in Frankfurt. |
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| TPPT071 | Preliminary Results on the Simultaneous Excitation of the TM010 and TE011 Modes in a Single Cell Niobium Cavity | focusing, coupling, emittance, superconducting-RF | 3844 | ||
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Funding: Work supported by the U.S. DOE Contract No DE-AC05-84ER40150. |
Simultaneous excitation of both TM010 and TE011 modes has been proposed recently for superconducting photoinjector applications to take advantage of the accelerating field of the TM mode, combined with the focusing magnetic field of the TE mode. Simultaneous excitation of both modes has been carried out on a CEBAF single cell cavity. The cavity has two beam pipe side-ports for each mode for input and pick-up couplers. Coupling to the TE011 mode is done by magnetic loop couplers while for the TM010 mode coaxial antennas are used. The TE011 mode has the property of having zero surface electric field, surface magnetic field orthogonal to the one in the TM010 mode and concentrated in the iris/wall regions of the cavity. The presence of both modes in the cavity at the same time can also be used to investigate the so-called high field Q-drop in the TM010 mode. This paper will present some preliminary result on the test of the single cell cavity at 2K. |
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| TPPT077 | Testing of HOM Coupler Designs on a Single Cell Niobium Cavity | coupling, superconductivity, vacuum, SNS | 4012 | ||
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Funding: Work supported by the U.S. DOE Contract No DE-AC05-84ER40150. |
Coaxial higher order mode (HOM) couplers were developed initially for PETRA cavitiesand subsequently for TESLA cavities. They were adopted later for SNS and Jlab upgrade cavities. The principle of operation is the rejection of the fundamental mode by the tunable filter configuration of the coupler and the transmission of the HOMs. It has been recognized recently that, in high average power applications, the pick-up probe of the HOM coupler must be superconducting in order to avoid substantial heat dissipation by the fundamental mode fields and deterioration of the cavity Q. In addition, the thermal conduction of existing rf feedthrough designs is only marginally sufficient to keep even the niobium probe tip superconducting in cw operation. We have equipped a single-cell niobium cavity with different HOM coupler configurations and tested the different designs by measuring Q vs Eacc behavior at 2 K for different feedthroughs and probe tipmaterials |
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| TPPT082 | High Thermal Conductivity Cryogenic RF Feedthroughs for Higher Order Mode Couplers | damping, higher-order-mode, simulation, SNS | 4108 | ||
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Funding: This manuscript has been authorized by SURA, Inc. under Contract No. DE-AC05-84ER-40150 with the U.S. Department of Energy. |
The use of higher-order-mode (HOM) pickup probes in the presence of significant fundamental rf fields can present a thermal challenge for cw or high average power SRF cavity applications. The electric field probes on the HOM-damping couplers on the JLab "High Gradient" and "Low Loss" seven-cell cavities for the CEBAF upgrade are exposed to approximately 10% of the peak magnetic field in the cavity. To avoid significant dissipative losses, these probes must remain superconducting during operation. Typical cryogenic rf feedthroughs provide a poor thermal conduction path for the probes, and provide inadequate stabilization. We have developed solutions that meet the requirements, providing a direct thermal path from the niobium probe, thorough single-crystal sapphire, to bulk copper which can be thermally stationed (or heat sunk). Designs, electromagnetic and thermal analyses, and performance data will be presented. |
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| WPAP007 | Status of the 3½ Cell Superconducting RF Gun Project in Rossendorf | gun, cathode, laser, electron | 1081 | ||
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In the paper, we report on the status and progress of the superconducting rf gun project in Rossendorf. The gun is designed for cw operation mode with 1mA current and 10 MeV electron energy. The gun will be installed at the ELBE superconducting electron linear accelerator. It will have a 3½ cell niobium cavity operating at 1.3 GHz. The cavity consists of three cells with TESLA geometry and a specially designed half-cell in which the photocathode will be placed. Two Nb cavities, with RRR 300 and 40 respectively, will be finished at the beginning of 2005. After delivery, the rf tests will be performed and the treatment of the cavities will be started. At the same time, the design of the cryostat is finished and the fabrication of its components is under way. Further activities are the design of the diagnostic beam line, the assembling of the new photocathode preparation system, and the upgrade of the 262 nm driver laser system.
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| WPAT012 | Status and Test Results of HPRF System for PEFP | rfq, klystron, proton, ion-source | 1288 | ||
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Funding: This work is supported by the 21C Frontier R&D program in the Ministry of Science and Technology of the Korean government. |
The PEFP 20MeV proton accelerator is composed of 3MeV RFQ and 20MeV DTL and two sets of 1MW, 350MHz RF system are required for each accelerating structure. The high power RF system for 3MeV RFQ was already installed and operated to drive the RFQ. The klystron was tested up to 600kW itself and operated in pulse routinely. The HPRF system for 20MeV DTL which consists of 4 tanks was installed, and the RF test for 4 tanks has been carried out. The ridge-loaded power coupler was designed and installed to drive RFQ and DTL. In this paper, the status and test results of the RF system for 20MeV proton accelerator are discussed. |
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| WPAT019 | Beam Tests of a New Digital Beam Control System for the CERN LEIR Accelerator | acceleration, booster, injection, proton | 1649 | ||
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We are developing a digital beam control and cavity servo system for controlling the RF acceleration in CERN’s Low Energy Ion Ring (LEIR), a major component in the LHC lead ion injector chain. As the LEIR ring will only start during summer 2005, we have tested a simplified prototype of the system with low intensity beams on the CERN PS Booster (PSB). The hardware and software have been developed within the framework of a CERN-BNL collaboration. This fully digital beam control system is contained in VME mother boards which can accommodate several daughter boards. The fast signal processing is implemented in Field Programmable Gate Arrays (FPGAs), while the slower signal processing and communication with the software layer above is implemented in programmable Digital Signal Processors (DSPs). The objectives of the tests with beam in the PSB are to verify the multiple DSP and FPGA architecture, the sampling rates and data flows and the feedback loop dynamics. An additional goal is to integrate a number of highly complex intelligent VME modules with many sub-functions in the CERN controls environment to provide adequate signal acquisition, control and diagnostics to operate the system.
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| WPAT022 | Low Level RF System for the Energy Recovery Linac Prototype | laser, linac, gun, feedback | 1781 | ||
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Funding: ASTeC Department, CCLRC Daresbury Laboratory. |
The Low Level RF system is described for the Energy Recovery Linac Prototype (ERLP) being constructed at Daresbury Laboratory. An analogue based feedback system, built around low cost proprietary components, has been designed to control the 1.3GHz RF system for this project. The system is scaleable, has digital control and can be easily upgraded as greater understanding of the accelerator becomes known. The design of the system is based around the central core of a very low phase noise master oscillator, which can provide, multiple outputs and timing pulses at all the required frequencies for the RF, laser and accelerator sub-systems. |
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| WPAT030 | Upgrade of the ATLAS Positive Ion Injector Bunching System | feedback, ion, bunching, linac | 2161 | ||
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Over the last few years, significant efforts were concentrated on improving the ATLAS Positive Ion Injector (PII) RF bunching system, consisting of a four-harmonic pre-buncher, Traveling Wave Chopper (TWC) and a single-frequency sinusoidal re-buncher. The primary goal was to improve RF field stability with a redesigned RF system and to improve buncher performance for higher current beams resulting in better bunch stability and time structure at the first PII superconducting resonator. The major parts of the system were redesigned and rebuilt, including the RF 12 – 48 MHz amplifiers for the harmonic pre-buncher and re-buncher, RF driver rack for the TWC, and the RF control chassis for both the pre-buncher and re-buncher. The four-harmonic resonant structure of the harmonic buncher itself was modified, too, mainly for better mechanical stability and better RF matching. These improvements will be described and the performance of the new system presented.
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| WPAT049 | The Penetrability of a Thin Metallic Film Inside the RF Field | cathode, electron, impedance, laser | 3073 | ||
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Funding: Under contract with the U.S. Department of Energy, Contract Number DE-AC02-98CH10886. |
Thin metallic film was widely applied in varies area. Especially, recently we are planning to apply it in a "Secondary emission enhanced photo-injector," of which a diamond cathode is coated with a golden film or so on its back to serve as a current path. The thickness of the film is originally considered to be in the order of 10 nm, which is much less than the skin depth, say 1/200. Since it is so thin, that intuitively the RF filed is penetrable. However, we found it is not true. The film will block most of the field. This paper addresses theoretic analysis as well as the experimental results. All demonstrated that the penetrability of a thin film is very poor. Consequently, most of the RF current will flow on the thin film causing a serous heating problem. |
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| WPAT082 | An Improved Pneumatic Frequency Control for Superconducting Cavities | vacuum, feedback, heavy-ion, ion | 4090 | ||
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Funding: U.S. Department of Energy. |
The ATLAS (Argonne Tandem Linear Accelerator System) superconducting cavities use a pneumatic system to maintain the cavity eigenfrequency at the master oscillator frequency. The present pneumatic slow tuner control has a limitation in the tuning slew rates. In some cases, the frequency slew rate is as low as 30 Hz/sec. The total tuning range for ATLAS cavities varies from 60 KHz to as high as 450 KHz depending on the cavity type. With the present system, if a cavity is at the extreme end of its tuning range, it may take an unacceptable length of time to reach the master oscillator frequency. We have designed a new slow tuner control system that increases the frequency slew rates by at least a factor of ten to a factor of three hundred in the more extreme cases. This improved system is directly applicable for use on the RIA (Rare Isotope Accelerator) cavities. This paper discusses the design of the system and the results of a prototype test. |
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| WPAT088 | Performance of TESLA Cavities After Fabrication and Preparation in Industry | vacuum, electron | 4221 | ||
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In order to demonstrate cw operation of TESLA cavities in linear accelerators driving FEL applications, two TESLA cavities were manufactured and prepared by ACCEL for BESSY. After production, both cavities were prepared for vertical test at ACCEL's premises using state of the art chemical polishing and high pressure water rinsing techniques. The cavities were tested in DESY's vertical RF test installation. Accelerating gradients close to 25 MV/m were reached. One cavity was completed with a helium vessel modified for cw operation and prepared with chemical polishing, high pressure water rinsing, and assembled with the required High Power Coupler at ACCEL. The fully dressed cavity was then shipped under vacuum to BESSY and tested in the horizontal cryostat HoBiCaT. Horizontal RF test results will be presented and compared with the vertical test results.
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| RPAP047 | DAQ System of BPM and BCT for the BEPCII Linac | linac, positron, monitoring, electron | 2980 | ||
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Following the BEPCII upgrade, total about 19 BPM and 12 BCT have been newly installed in the BEPCII Linac. Also, a set of distributed control system based on EPICS architecture has been built, and the BPM and BCT system are merged into the new control system for the data acquisition. In order to reduce the effects of RF noise, a special gated integrator was used to measure the beam current. In this paper we will describe the DAQ system of BPM and BCT including calibrations in detail.
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| RPAT005 | Beam Diagnostics for the J-PARC Main Ring Synchrotron | beam-losses, proton, electron, target | 958 | ||
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Beam diagnostics: beam intensity monitors (DCCT, SCT, FCT, WCM), beam position monitors (ESM), beam loss monitors (proportional chamber, air ion chamber), beam profile monitors (secondary electron emission, gas-sheet) have been designed, tested, and will be installed for the Main Ring synchrotron of J-PARC (Japan Proton Accelerator Research Complex). This paper describes the basic design principle and specification of each monitor, with a stress on how to cope with high power beam (average circulation current of ~12 A) and low beam loss operation (less than 1 W/m except a collimator region). Some results of preliminary performance test using present beams and a radiation source will be reported.
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| RPAT007 | Status of Beam Diagnostic Systems for the PEFP | proton, diagnostics, instrumentation, linac | 1090 | ||
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Funding: Supported by the PEFP (Proton Engineering Frontier Project). |
A proton linear accelerator is currently the construction at the KAERI (Korea Atomic Research Institute) to the PEFP (Proton Engineering Frontier Project) in Korea. We are accomplished the technique development of beam diagnostic system to be currently the construction. We treat beam diagnostics for the high power proton linear accelerator. Prototype beam position & phase monitor (BPPM) electronics was made and tested successfully in one of the beam diagnostic systems. The beam position monitor pickup electrode is a capacitive type (electrostatic type) which has a button form. Button form electrode, in common use around electron synchrotrons and storage rings, are a variant of the electrode with small button form (e.g., sub mm diameter). However, we are designed button form electrode to measure beam position of proton beam. The BCM (Beam Current Monitor) is developed Tuned CT (Current Transformer) for collaborate with Bergoz Instruments. This paper describes the status of beam diagnostic systems for the PEFP. |
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| RPAT011 | Digital Signal Processing the Tevatron BPM Signals | antiproton, closed-orbit, proton, controls | 1242 | ||
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Funding: Fermilab |
The Beam Position Monitor (BPM) readout system at Fermilab’s Tevatron has been updated and is currently being commissioned. The new BPMs use new analog and digital hardware to achieve better beam position measurement resolution. The new system reads signals from both ends of the existing directional stripline pickups to provide simultaneous proton and antiproton position measurements. The signals provided by the two ends of the BPM pickups processed by analog band-pass filters and sampled by 14-bit ADCs at 74.3MHz. A crucial part of this work has been the design of digital filters that process the signal. This paper describes the digital processing and estimation techniques used to optimize the beam position measurement. The BPM electronics must operate in narrow-band and wide-band modes to enable measurements of closed-orbit and turn-by-turn positions. The filtering and timing conditions of the signals are tuned accordingly for the operational modes. The analysis and the optimized result for each mode is presented. |
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| RPAT013 | Signal Processing for Longitudinal Parameters of the Tevatron Beam | proton, antiproton, emittance, synchrotron | 1362 | ||
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Funding: Operated by Universities Research Association Inc. under Contract No. DE-AC02-76CH03000 with the United States Department of Energy. |
The time profiles of the bunches in the Tevatron are obtained by sampling the output of a resistive wall current monitor with a 5GS/s, 2GHz bandwidth, Lecroy 6200 oscilloscope. The techniques for removing the effect of cable dispersion and for extending the dynamic range of the data by splitting the signal and using two input channels at different gains are described. The algorithms for taking these data in the time domain and deriving the momentum spread and longitudinal emittance are also given. |
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| RPAT018 | Simultaneous Position Measurements of Protons and Anti-Protons in the Tevatron | injection, proton, antiproton, closed-orbit | 1613 | ||
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Fermilab has embarked upon a program to upgrade the electronics of the Beam Position Monitor (BPM) system that measures the transverse position of the beams inside the Tevatron collider. The new system improves on the current system in precision, accuracy and reliability. A new feature in the upgraded system is the ability, when both protons and anti-protons are present in the Tevatron, make simultaneous measurements of the closed orbit position of both beam species. The method chosen for achieving the simultaneous measurement is an algorithm that deconvolutes the imperfect directionality of the BPM pickups from the raw measurements. This paper will discuss the algorithm, the calibration of the parameters used by the algorithm and the robustness of the algorithm. It will also present results from the upgraded system which demonstrate that the system meets the requirements set out at the start of the upgrade project.
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| RPAT019 | Use of a Reconfigurable VME Module To Measure Beam Energy at the Los Alamos Proton Storage Ring | linac, proton, injection, storage-ring | 1658 | ||
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Funding: U.S. Department of Energy. |
Custom instrumentation has been developed at the Los Alamos Neutron Science Center to measure the Proton Storage Ring (PSR) beam energy. The PSR accumulates up to 4x1013 protons from the linear accelerator for delivery to a spallation neutron source. The energy of the beam injected into the PSR must be adjusted so that the revolution frequency matches the ring buncher frequency, otherwise a large momentum spread will cause increased losses in high-dispersion areas. Errors in injected beam energy appear as deviations from the ideal revolution frequency. A low-cost, custom, reconfigurable VME module has been adapted to calculate the PSR revolution frequency in real-time. The module connects directly to an analog wall current monitor output and uses analog signal conditioning electronics, an analog to digital converter, field programmable gate arrays, and an embedded floating-point digital signal processor to calculate the revolution frequency. This is an improvement over the previously used method of manually measuring the frequency with an oscilloscope. Accelerator physicists can now simply observe the PSR frequency, which is dependent on beam energy, on a control room display. LA-UR-04-8661. |
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| RPAT045 | Beam Phase Detection for Proton Therapy Accelerators | cyclotron, proton, acceleration, feedback | |||
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The industrial application of proton cyclotrons for medical applications has become one of the important contributions of accelerator physics during the last years. This paper describes an advanced vector demodulating technique used for non-destructive measurements of beam intensity and beam phase over 360°. A computer controlled I/Q-based phase detector with a very large dynamic range of 70 dB permits the monitoring of beam intensity, phase and eventually energy for wide range of beam currents down to –130 dBm. In order to avoid interference from the fundamental cyclotron frequency the phase detection is performed at the second harmonic frequency. A digital low pass filter with adjustable bandwidth and steepness is implemented to improve accuracy. With a sensitivity of the capacitive pickup in the beam line of 30 nV per nA of proton beam current at 250 MeV, accurate phase and intensity measurements can be performed with beam currents down to 3.3 nA.
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| RPAT053 | Movement of BPMs Due to Thermal Stress in KEKB | sextupole, radiation, luminosity, synchrotron | 3253 | ||
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Movement of Beam Position Monitors (BPM) due to thermal stress in high beam current operation is observed in KEKB. For high luminosity operation of KEKB, the beam current as high as 1.6A is accumulated in the positron ring and a precise control of the beam orbit based on the BPM system is required. Though the every BPM chamber is fixed firmly on a support of each quadrupole magnet, the BPM chamber moves several hundred microns from the setting position depending on the beam current due to beam pipe heating by strong synchrotron light irradiation. Such movement introduces an unavoidable offset error in the BPM measurement, and is a serious problem not only for KEKB but also for the next generation of B-factory operated with extremely high beam current. We report the measurement of the movement by distance sensors and an attempt to correct the BPM offset error in real-time operation.
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| RPAT054 | Beam Position Monitor at the PLS BTL | linac, electron, monitoring, injection | 3289 | ||
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Funding: Work supported by the Ministry of Science and Technology, Korea. |
Electron Linac at the Pohnag Accelerator Laboratory (PAL) has been operated continuously as the full energy injector for storage ring. Linac and storage ring energy has been 2.0 GeV since Dec. 1994, and 2.5 GeV since Oct. 2002. In Aug. 2004, thirteen BPMs are newly installed at BTL(Beam Transport Line) for beam trajectory measurement and feedback. These BPMs consist of 100mm strip-line electrodes in 150mm long chamber, and 500MHz log-ratio signal processing circuits. BPM data acquisition system is developed as EPICS IOC using NI S-series data acquisition board and NI LabView 7.1. BTL BPMs will be used for optic correction and beam energy feedback for PLS beam injection. This paper describes on design, test results, installation and data acquisition system of the PLS BTL BPM. |
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| RPAT061 | New Electron Beam Position Monitoring and Feedback System Upgrades for the Synchrotron Radiation Source at Daresbury Laboratory | monitoring, feedback, storage-ring, electron | 3538 | ||
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Funding: ASTeC Department, CCLRC Daresbury Laboratory. |
The installation of a new APPLE/II undulator with user controlled polarisation has necessitated the upgrade of the Electron Beam Position Monitoring (EBPM) detector electronics and position feedback systems. The upgraded installation will utilise commercially available multiplexed detection electronics, coupled with a two phase control system interface replacement. Phase one involves the replacement of the existing G-64 based read-back system with direct analogue connections to the VME beam steering and Feedback system. This allows existing monitoring and feedback software to work with improved update rates (~ 1Hz -> ~ 8Hz). Phase two will see the installation of new high-performance control system front ends and will allow real-time monitoring at up to 100Hz and provide snapshots with resolution of 1-10 KHz. |
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| RPAT074 | PEP-II Transverse Feedback Electronics Upgrade | feedback, diagnostics, coupling, kicker | 3928 | ||
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Funding: Supported by the U.S. Department of Energy under contract No. DE-AC03-76SF00098 (LBNL) and DE-AC03-76SF00515 (SLAC). |
The PEP-II B Factory at the Stanford Linear Accelerator Center (SLAC) requires an upgrade of the transverse feedback system electronics. The new electronics require 12-bit resolution and a minimum sampling rate of 238 Msps. A Field Programmable Gate Array (FPGA) is used to implement the feedback algorithm. The FPGA also contains an embedded PowerPC 405 (PPC-405) processor to run control system interface software for data retrieval, diagnostics, and system monitoring. The design of this system is based on the Xilinx® ML300 Development Platform, a circuit board set containing an FPGA with an embedded processor, a large memory bank, and other peripherals. This paper discusses the design of a digital feedback system based on an FPGA with an embedded processor. Discussion will include specifications, component selection, and integration with the ML300 design. |
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| RPAT098 | Phase-Space Dynamic Tracking by a Two Pickups Data Acquisition System | octupole, sextupole, lattice, kicker | 4326 | ||
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A two pickups dynamic tracking data acquisition system has been developed at LNF for the DAFNE Phi-factory. Two oscilloscopes sample horizontal and vertical sum and difference signals from two pickups simultaneously; the sampling clock is locked to the DAFNE timing system. A horizontal kick excites the beam motion and initiates the acquisition. Turn-by-turn signals are converted to beam position and stored on a server in a database using timestamp labels. Oscillation amplitude versus time, phase space distribution and frequency domain analysis are shown for several lattices and different settings of sextupoles and octupoles. Results are used to check the DAFNE non-linear model.
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| RPPP053 | Simulations of Resistive-Wall Instability in the ILC Damping Rings | damping, feedback, simulation, radiation | 3241 | ||
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Funding: Work supported by U.S. Department of Energy, Director, Office of Science, Contract No. DE-AC03-76SF00098. |
Options being considered for the ILC Damping Rings include lattices with circumferences up to 17 km. The circumference, beam current and beam energy place the damping rings in a regime where resistive-wall instability is a concern, particularly as there are very demanding tolerances on the bunch-to-bunch jitter. Generally, it is possible to make good analytical estimates of the coupled-bunch growth rates in a storage ring, but particular features of the damping rings (including the fill pattern, large variations of the lattice functions and beam-pipe cross-section in different parts of the ring, and transverse beam coupling in the long straight sections) make it desirable to study the coupled-bunch instabilities using simulations. Here, we present the results of simulations of the transverse instabilities using a detailed lattice model. A bunch-by-bunch feedback system will be needed to suppress the instabilities, and a model for an appropriate feedback system is included in the simulations. |
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| RPPT045 | A Method to Calibrate Beam Position Monitor at HLS 200 MeV LINAC | linac, simulation, impedance, injection | 2896 | ||
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In order to improve injection efficiency of HLS 200Mev LINAC, we redesign a new strip line beam position monitor system, which is consisted of a strip line structure and a signal processing system. We decide on an online calibration method based on beam to find out the geometry centre displacement and relative gain offset. Before the BPM testing bench has been prepared, we make a simulation based on the model accounted for all factors influencing signal amplitudes and get the calibrating results. At last, we analyze the nonlinearity effect on the calibration results.
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| RPPT046 | Development and Application of Bunch-by-Bunch Measurement System of HLS | damping, synchrotron, betatron, single-bunch | 2932 | ||
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This paper is intended to present the newly implemented wideband (100MHz) bunch oscillation measurement system, which is in nature a different method from the narrow-band (<5MHz) facilities employed before. Basic formalism and implementation details of the system is introduced to illustrate the function of observing coupled bunch instabilities in time and frequency domain. The designed function includes detecting of transverse oscillation, synchrotron phase oscillation, as well as bunch filling pattern. Some diagnostics results of machine instabilities and application of this system are also discussed.
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| RPPT047 | Development of Measurement and Transverse Feedback System at HLS | feedback, single-bunch, storage-ring, simulation | 2974 | ||
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In order to observe and cure coupled bunch (CB) instabilities caused by the high order modes (HOMs) of the RF cavity and the resistive wall impedance of the Ring vacuum chamber, which were ineluctable during the operation of the accelerator, an observer system characterized by bunch by bunch measurement of transverse ßoscillation and longitudinal synchrotron phase oscillation has been constructed and commissioned at Hefei Light Source (HLS); meanwhile a transverse bunch-by-bunch feedback system is under construction. The design and development of the systems, as well as diagnostics results of machine instabilities will be presented in this paper.
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| RPPT048 | HLS Turn-By-Turn System and Its Application | injection, feedback, accumulation, storage-ring | 3022 | ||
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Design and experimental application of the turn-by-turn system of Hefei Light Source (HLS) are presented in this paper. The front-end signal measurement adopts a log-ratio electronics circuitry. The system is designed to be capable of up to 2 seconds data acquisition. Injection kickers are used to excite beam for monitoring ß oscillation and damping rate. Some of experimental applications are also illustrated, in commission of both the upgraded injection system of HLS and the lower frequency feedback system. The results shows that in order to improve the accumulation of the injected beam, it is very necessary to investigate integral magnet fields equilibrium of injected system and proper measures to control restrain remnants ß-oscillation caused by the injected system error.
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| RPPT050 | The Measurement of Tune and Phase Space at HLS | extraction, lattice, betatron, storage-ring | 3114 | ||
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Tune and phase space online monitor at the electronic storage ring of Hefei Light Source (HLS) have been realized by using of turn-by-turn beam position data. In this paper, we have compared many methods to compute tune and discussed how to choose the best fitting method for our online tune computing. We can compute and display tune online, at the same time, beam tracks were obtained on the transverse phase space by using turn-by-turn beam position data at two differently-located beam-position-monitor electrodes. With these instruments we can precise and attractive study machine instabilities
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| FPAE037 | SPIRAL 2 RFQ Prototype First Tests | rfq, vacuum, acceleration, ion | 2488 | ||
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The SPIRAL2 RFQ is designed to accelerate at 88MHz two kinds of charge-over-mass ratio, Q/A, particles. The proposed injector can accelerate a 5 mA deuteron beam (Q/A=1/2) or a 1 mA particles beam with q/A=1/3 up to 0.75 MeV/A. It is a CW machine which has to show stable operation, provide the request availability, have the minimum losses in order to minimize the activation constraints and show the best quality/cost ratio. The prototype of this 4-vane RFQ has been built and tested. It allowed to verify the mechanical assembly concept (RFQ without any brazing step). The full power was easily injected in the cavity, with no concerns for the RF joints. The paper describes the different achievements.
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| FPAT005 | A Betatron Tune Fitting Package for the Tevatron 21.4 MHz Schottky | betatron, synchrotron, antiproton, collider | 937 | ||
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Accurate control of the Betatron tunes and chromaticities is required to optimize the dynamical aperture of any large synchrotron. The Fermilab Tevatron is equipped with two independent Schottky monitors, one operating at 21.4 MHz and the other 1.7 GHz. While the latter one allows us to characterize individual bunches separated by 396 ns, the former one has a larger Q and can give precise tune measurements. A new front-end and related data acquisition for this 21.4 MHz resonator has been installed and commissioned during the FY04 Collider RunII. Output signal are digitized at 100 KHz. Frequency spectra are transfered to dedicated server nodes and fitted in real time. Such frequency spectra are quite complex, due to inherent noise, horizontal/vertical coupling and synchrotron motion. Sophisticated fitting strategies are required. Optimization of this fitting package on relatively powerful commodity computer allows us to report tune and chromaticity measurements at almost 1 Hz. The architecture of the data acquisition system and this fitting package are described and results taken during the FY04 and FY05 runs are presented.
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