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MOPCH026 | A Biperiodic X-band RF Cavity for SPARC | coupling, simulation, controls, scattering | 101 | ||||
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The Frascati photo-injector SPARC (Pulsed Self Amplified Coherent Radiation Source) will be equipped with an X-band RF cavity for linearizing emittance to enhance bunch compression and for reducing bunch longitudinal energy spread. A biperiodic cavity working on the pi/2-mode offers some advantages in comparison to a conventional (periodic) cavity despite the need of accurate machining. A copper prototype made of 17 separated cells has been built following numerical simulation. In this paper we report on preliminary measurements of its RF properties. The main characteristics of the cooling system for the final device are also addressed.
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MOPCH121 | Ground Motion Measurement at J-PARC | ground-motion, site, KEKB, KEK | 330 | ||||
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In the next generation accelerator, construction of the machine on the stable ground is preferable for accelerator beam operation. We have measured ground motion at the J-PARC site under construction, where the ground is very close to the Pacific Ocean. In this paper, some of the observed results are shown, comparing the results of the previous observation at some accelerator facilities and next generation accelerator candidate sites in Japan.
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MOPCH178 | Tests on MgB2 for Application to SRF Cavities | laser, target, LANL, cryogenics | 481 | ||||
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Magnesium diboride (MgB2) has a transition temperature (Tc) of ~40 K, i.e., about four times higher than niobium (Nb). The studies in the last three years have shown that it could have about one order of magnitude less RF surface resistance (Rs) than Nb and seems much less power dependent compared to high-Tc materials such as YBCO. In this paper we will present results on the dependence of Rs on surface magnetic fields and possibly the critical RF surface magnetic field.
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MOPCH193 | SNS 2.1K Cold Box Turn-down Studies | cryogenics, SNS, controls, linac | 514 | ||||
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The Spallation Neutron Source (SNS) at Oak Ridge National Laboratory is nearing completion. The cold section of the Linac consists of 81 superconducting radio frequency cavities cooled to 2.1K by a 2400 watt cryogenic refrigeration system. The 2.1K cold box consists of four stages of centrifugal compressors with LN2-cooled variable speed electric motors and magnetic bearings. The cryogenic system successfully supported the Linac beam commissioning at both 4.2K and 2.1K and has been fully operational since June 2005. This paper describes the control principles utilized and the experimental results obtained for the SNS cold compressors turn-down capability to about 30% of the design flow, and possible limitation of the frequency dependent power factor of the cold compressor electric motors, which was measured for the first time during commissioning. These results helped to support the operation of the Linac over a very broad and stable cold compressor operating flow range (refrigeration capacity) and pressure. This in turn helped to optimise the cryogenic system operating parameters, minimizing the utilities and improving the system reliability and availability.
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MOPLS026 | Monitoring of Interaction-point Parameters using the 3-dimensional Luminosity Distribution Measured at PEP-II | luminosity, lattice, monitoring, coupling | 598 | ||||
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The 3-D luminosity distribution at the IP of the SLAC B-Factory is monitored using e+ e- -> e+ e-, mu+ mu- events reconstructed online in the BaBar detector. The transverse centroid and spatial orientation of the luminosity ellipsoid provide a reliable monitor of IP orbit drifts. The longitudinal centroid is sensitive to small variations in the average relative RF phase of the beams and provides a detailed measurement of the phase transient along the bunch train. Relative variations in horizontal luminous size are detectable at the micron level. The longitudinal luminosity distribution depends on the e± overlap bunch length and the vertical IP beta-function beta*y. In addition to continuous online monitoring of all the IP parameters above, we performed detailed studies of their variation along the bunch train to investigate a temporary luminosity degradation. We also used controlled variations in RF voltage and beam current to extract separate measurements of the e+ and e- bunch lengths. The time-history of the beta*y measurements, collected over a year of routine high-luminosity operation, are compared with HER & LER phase-advance data periodically recorded in single-bunch mode.
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MOPLS048 | Doubling the PEP-II Luminosity in Simulations | luminosity, simulation, damping, emittance | 649 | ||||
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The PEP-II luminosity reached 1x1034cm-2s-1 in October 2005. The question of how to increase the luminosity using modest improvements in the PEP-II accelerator in the coming years is the subject of this paper. We found that the parasitic collisions significantly degrade the simulated luminosity as the beam currents are increased from 3A and 1.7A to 4A and 2.2A in the low and high energy rings, respectively. Using the beam-beam code BBI, we systematically optimized the luminosity and showed that a luminosity of over 2x1034cm-2s-1 is achievable within the limits of machine parameters.
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MOPLS049 | Anomalous High Radiation Beam Aborts in the PEP-II B-factory | vacuum, background, radiation, luminosity | 652 | ||||
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The PEP-II B-factory at SLAC has recently experienced unexpected beam losses due to anomalously high radiation levels at the BaBar detector. The problem was finally traced to the occurrence of very high pressure (>100 nTorr) spikes that have a very short duration (few seconds). We describe the events and show analysis predicting where in the vacuum system the events originated and describe what was discovered in the vacuum system.
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MOPLS051 | Tracking Down a Fast Instability in the PEP-II LER | vacuum, beam-losses, damping, feedback | 658 | ||||
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During Run 5, the beam in the PEP-II Low Energy Ring (LER) became affected by a predominantly vertical instability with very fast growth rate of 10
60/ms - much faster than seen in controlled grow-damp experiments - and varying threshold. The coherent amplitude of the oscillation was limited to approx. 1 mm pk-pk or less and would damp down over a few tens of turns; however, beam loss set in even as the measured amplitude damped, causing a beam abort. This led to the conclusion that the beam was actually blowing up. The presence of a 2 nu_s line in the spectrum suggested a possible head-tail nature of the instability, although chromaticity was not effective in raising the threshold. In this paper we will describe the measurements and data taken to isolate and locate the cause of the instability and, eventually, the discovery and fix of the root cause.
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MOPLS053 | Beta-beat Correction Using Strong Sextupole Bumps in PEP-II | sextupole, luminosity, closed-orbit, coupling | 664 | ||||
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A method for correcting lattice beta mismatches has been developed for the PEP-II collider using orbit offsets in strong sextupoles. The solution is first predicted in the MAD program by modeling closed orbit bumps in the plane of correction at the sextupoles strongest in that plane. The derived solution is then tested in the machine to confirm the prediction and finally dialed into the machine under high-current conditions.
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MOPLS066 | Direct Measurement of Geometric and Resistive Wakefields in Tapered Collimators for the International Linear Collider | emittance, linear-collider, collider, impedance | 697 | ||||
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Precise collimation of the beam halo is required in the ILC to prevent beam losses near the interaction region that could cause unacceptable backgrounds for the physics detector. The necessarily small apertures of the collimators lead to transverse wakefields that may result in beam deflections and increased emittance. A set of collimator wakefield measurements has previously been performed in the ASSET region of the SLAC LINAC. We report on the next phase of this programme, which is carried out at the recently commissioned End Station A test facility at SLAC. Measurements of resistive and geometric wakefields using tapered collimators are compared with model predictions from MAFIA and GdfidL and with analytic calculations.
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MOPLS067 | Test Beam Studies at SLAC's End Station A, for the International Linear Collider | linac, synchrotron, emittance, linear-collider | 700 | ||||
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The SLAC Linac can deliver to End Station A a high-energy test beam with similar beam parameters as for the International Linear Collider for bunch charge, bunch length and bunch energy spread. ESA beam tests run parasitically with PEP-II with single damped bunches at 10Hz, beam energy of 28.5 GeV and bunch charge of (1.5-2.0)·1010 electrons. A 5-day commissioning run was performed in January 2006, followed by a 2-week run in April. We describe the beamline configuration and beam setup for these runs, and give an overview of the tests being carried out. These tests include studies of collimator wakefields, prototype energy spectrometers, prototype beam position monitors for the ILC Linac, and characterization of beam-induced electro-magnetic interference along the ESA beamline.
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MOPLS070 | Numerical Calculations of Collimator Insertions | simulation, impedance, insertion, CERN | 709 | ||||
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A series of collimator spoilers have been designed and manufactured for testing in the ESA wakefield tests. The purpose of the tests is a benchmarking exercise to assist with the understanding into the causes of wakefields due to spoiler profile and materials. Simulations of the spoiler designs have been used to understand the likely effects that would be observed with the beam tests. Simulations of these collimator insertions have been carried out in MAFIA and GDFIDL, and a comparison of the results completed. The wake potential has been measured, and the corresponding loss factor and kick factors have been calculated. The results from the simulations are discussed in this report.
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MOPLS071 | TDR Measurements in support of ILC Collimator Studies | impedance, simulation, electron, synchrotron | 712 | ||||
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In this report the outcome of the "wire method" cold test, experimental results and their relevance toward the ILC set-up is considered. A wire is stretched through the centre of a vessel along the axis that the electron beam would take, and a voltage pulse representing the electron bunch is passed along the wire. The parasitic mode loss parameter from this voltage can then be measured. The bunch length for the ILC is 0.3mm, requiring a pulse rise time of ~1ps. The fastest rise time available for a time domain reflectrometry (TDR) scope is ~10ps. Reference vessels have been examined to evaluate the suitability of the test gear at comparable bunch structures to the ILC.
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MOPLS073 | Shower Simulations, Comparison of Fluka, Geant4 and EGS4 | simulation, radiation, target, electron | 718 | ||||
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Computer simulations with different packages (Fluka, Geant4 and EGS4) were run in order to determine the energy deposition of an ILC bunch in a spoiler of specified geometry at various depths. The uncertainty in these predictions is estimated by comparison of their results. Various candidate spoiler designs (geometry, material) are studied. These shower simulations can be used as inputs to thermal and mechanical studies using programs such as ANSYS.
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MOPLS078 | Benchmarking of Tracking Codes (BDSIM/DIMAD) using the ILC Extraction Lines | extraction, beam-transport, quadrupole, optics | 733 | ||||
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The study of beam transport is of central importance to the design and performance assessment of modern particle accelerators. In this work, we benchmark two contemporary codes - DIMAD and BDSIM, the latter being a relatively new tracking code and built within the framework of GEANT4. We consider both the 20mrad and 2mrad extraction lines of the International Linear Collider and perform disrupted beam tracking studies of heavily disrupted post-collision electron beams. We find that the two codes in most cases give an equivalent description of the beam transport.
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MOPLS082 | Simulation of the ILC Collimation System Using BDSIM, MARS15 and STRUCT | collimation, extraction, simulation, radiation | 744 | ||||
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The simulation codes STRUCT, MARS15 and BDSIM are used to simulate in detail the collimation section of the ILC. A comparative study of the collimation system performance is performed, and the key radiation loads are calculated. Results for the latest ILC designs are presented together with their implications for future design iterations.
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MOPLS109 | Operational Experience with Undulator for E-166 | undulator, positron, electron, vacuum | 819 | ||||
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We represent results of operation of 2.54 mm period, K=0.2, up to 30 Hz undulator used in E-166 experiment for polarized positron production. One peculiarity is in usage of Ferrofluid for cooling.
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MOPLS110 | ILC Linac R&D at SLAC | klystron, linac, DESY, collider | 822 | ||||
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Since the ITRP recommendation in 2004 to use superconducting rf technology for a next generation linear collider, the former NLC group at SLAC has been actively pursuing a broad range of R&D for this collider (the ILC). In this paper, we review the progress of those programs relating to linac technology. These include the development of a Marx-style modulator (120 kV, 120 A, 1.5 ms, 5 Hz) and a 10 MW sheet-beam klystron, construction of an L-band (1.3 GHz) rf source using a SNS HVCM modulator and commercial klystrons, fabrication and testing of a five-cell L-band cavity prototype for the ILC positron capture accelerator, high power tests of cavity coupler components, beam tests of prototype S-band linac beam position monitors and measurements of the magnetic center stability of an ILC prototype superconducting quadrupole magnet built by the CIEMAT group in Spain.
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MOPLS123 | Performance of the FONT3 Fast Analogue Intra-train Beam-based Feedback System at ATF | feedback, kicker, linear-collider, CLIC | 852 | ||||
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We report on the design and testing of the 3rd generation Feedback On Nanosecond Timescales (FONT) prototype intra-train beam-based feedback system for beam control and luminosity optimisation at the International Linear Collider (ILC). The all-analogue FONT3 electronics was designed to have an ultra-short latency of c. 10ns. We describe the design of the BPM signal processor, feedback circuit and kicker-driver amplifier. We report on deployment of FONT3 at the Accelerator Test Facility (ATF) at KEK, where it was tested with the 56ns-long electron bunchtrain extracted from the ATF damping ring. Feedback, with delay-loop operation, on the beam was demonstrated with a latency close to design. We comment on the applicability of this technology to ILC, as well as future warm-RF based linear colliders, such as CLIC.
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TUPCH103 | New Developments on Single-shot Fiber Scope | laser, controls, feedback | 1253 | ||||
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New development has been done to reduce the noise and improve the stability of the single-shot fiber scope, which used an optical fiber recirculating delay line to regenerate the single-shot very short electrical pulse, so a sampling scope can recover the original signal. New measurements have been done and will be reported.
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TUPCH105 | Performance of a Nanometer Resolution BPM System | extraction, alignment, dipole, linear-collider | 1256 | ||||
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International Linear Collider (ILC) interaction region beam sizes and component position stability requirements will be as small as a few nanometers. It is important to the ILC design effort to demonstrate that these tolerances can be achieved ideally using beam-based stability measurements. It has been estimated that RF cavity beam position monitors (BPMs) could provide position measurement resolutions of less than one nanometer and could form the basis of the desired beam-based stability measurement. We have developed a high resolution RF cavity BPM system. A triplet of these BPMs has been installed in the extraction line of the KEK Accelerator Test Facility (ATF) for testing with its ultra-low emittance beam. The three BPMs are rigidly mounted inside an alignment frame on variable-length struts which allow movement in position and angle. We have developed novel methods for extracting the position and tilt information from the BPM signals including a calibration algorithm which is immune to beam jitter. To date, we have been able to demonstrate a resolution of approximately 20 nm over a dynamic range of ± 20 microns. We report on the progress of these ongoing tests.
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TUPCH118 | Manufacturing and Testing of 2.45 GHz and 4.90 GHz Biperiodic Accelerating Structures for MAMI C | coupling, MAMI, vacuum, resonance | 1292 | ||||
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At the Institut fur Kernphysik (IKPH) of Mainz University the fourth stage of the Mainz Microtron (MAMI), a 855MeV to 1500MeV Harmonic Double Sided Microtron*, is now on the verge of first operation. For this project ACCEL Instruments GmbH manufactured biperiodic, on axis coupled, standing wave accelerating structures at the frequencies of 2.45GHz and 4.90GHz. Four resp. eleven multicell sections were manufactured, low power characterized and after delivery tested at the high power test stand of IKPH. This paper describes the production and characterization of these structures, presents results of the high power tests, and compares these data with results gained at IKPH for an in house built 4.90GHz prototype and the 2.45GHz structures built in the 1980s.
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*A. Jankowiak et al. "Design and Status of the 1.5 GeV-Harmonic Double Sided Microtron for MAMI", Proceedings EPAC2002, Paris, p. 1085. |
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TUPCH155 | 2D and 1D Surface Photonic Band Gap Structures for Accelerator Applications | radiation, electron, plasma, undulator | 1388 | ||||
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High frequency (26.5GHz to 40GHz), high power (tens of MW) microwave sources are required for cavity testing and conditioning applications in accelerators such as CLIC. The first study of microwave radiation from a co-axial Free-Electron Maser (FEM) based on a two-mirror cavity formed by a 2D Surface Photonic Band Gap (SPBG) structure (input mirror 10.4cm) and 1D SPBG structure (output mirror 10cm) is presented. The electron beam source consisted of a magnetically insulated plasma flare emission carbon cathode. Application of a 450kV voltage pulse of duration ~250ns across the cathode and grounded anode resulted in the production of a 7.0cm diameter annular electron beam of current ~1500A. The output radiation power from the FEM was measured using a Ka-band horn with 60dB of attenuation in front of a microwave detector located at a distance of 1.5m from the output window. By integrating the microwave power measured at the detector over the radiation pattern a total power of 50 (±10) MW corresponding to an efficiency of ~9% was calculated. The location of the operating frequency was found to lie between 35GHz and 39GHz, which agrees with theoretically predicted frequency of 37.2GHz.
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TUPCH164 | Ka-band Test Facility for High-gradient Accelerator R&D | vacuum, cathode, CLIC, DIAMOND | 1408 | ||||
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Achievement of high acceleration gradients in room-temperature structures requires basic studies of electric and magnetic RF field limits at surfaces of conductors and dielectrics. Facilities for such studies at 11.4 GHz have been in use at KEK and SLAC; facilities for studies at 17.1 GHz are being developed at MIT and UMd; and studies at 30 GHz are being conducted at CERN using the CLIC drive beam to generate short intense RF pulses. Longer pulse studies at 34 GHz are to be carried out at a new test facility being established at the Yale Beam Physics Laboratory, built around the Yale/Omega-P 34-GHz magnicon. This high-power amplifier, together with an available ensemble of components, should enable tests to be carried at up to about 9 MW in 1 mcs wide pulses at up to four output stations or, using a power combiner, at up to about 35 MW in 1 mcs wide pulses at a single station. RF pulse compression is planned to be used to produce 100-200 MW, 100 ns pulses; or GW-level, 1 mcs wide pulses in a resonant ring. A number of experiments have been prepared to utilize multi-MW 34-GHz power for accelerator R&D, and users for future experiments are encouraged to express their interest.
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TUPCH166 | Multi-megawatt Harmonic Multiplier for Testing High-gradient Accelerator Structures | klystron, gun, electron, simulation | 1414 | ||||
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Basic studies for determining the RF electric and magnetic field limits on surfaces of materials suitable for accelerator structures for a future multi-TeV collider, and for the testing of the accelerator structures and components themselves, require stand-alone high-power RF sources at several frequencies, from 10 to 45 GHz. A relatively simple and inexpensive two-cavity harmonic multiplier at 22.8, 34.3, or 45.7 GHz is suggested to be the stand-alone multi-MW RF power source for this application. The design is based on the use of an existing SLAC electron gun, such as the XP3 gun, plus a beam collector as used on the XP3 klystron. RF drive power would be supplied from an 11.4 GHz, 50 or 75 MW SLAC klystron and modulator, and a second modulator would be used to power the gun in the multiplier. Preliminary computations show that 64, 55, and 47 MW, respectively, can be realized in 2nd, 3rd, and 4th harmonic multipliers at 22.8, 34.3, and 45.7 GHz using 75 MW of X-band drive power.
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WEPCH061 | SABER Optical Design | electron, positron, linac, sextupole | 2062 | ||||
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SABER, the South Arc Beam Experimental Region, is a proposed new beam line facility designed to replace the Final Focus Test Beam at SLAC. In this paper, we outline the optical design features and beam parameters now envisioned for SABER. A magnetic chicane to compress positron bunches for SABER and a bypass line that could transport electrons or positrons from the two-thirds point of the linac to SABER, bypassing the LCLS systems, are also discussed.
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WEPCH123 | Large Simulation of High Order Short Range Wakefields | simulation, higher-order-mode, dipole, DESY | 2209 | ||||
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We present a formalism for incorporating intra-bunch wake fields into particle-by-particle tracking codes, such as MERLIN and BDSIM. Higher order wake field effects are incorporated in a manner which is computationally efficient. Standard formulae for geometric, resistive and dielectric wake fields are included for various apertures, particularly those relevant for ILC collimators. Numerous examples are given.
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WEPLS139 | Operational Status of Klystron-modulator System for PAL 2.5-GeV Electron Linac | klystron, linac, electron, feedback | 2703 | ||||
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The klystron-modulator(K&M) system of the Pohang Accelerator Laboratory (PAL) generates high power microwaves for the acceleration of 2.5 GeV electron beams. There are 12 modules of K&M system to accelerate electron beams up to 2.5 GeV nominal beam energy. One module of the K&M system consists of the 200 MW modulator and an 80 MW S-band (2856 MHZ) klystron tube. The total accumulated high-voltage run-time of the oldest unit among the 12 K&M systems has reached nearly 88,000 hours as of December 2005. The overall system availability is well over 95%. In this paper, we review the overall system performance of the high-power K&M system and the operational status of the klystrons and thyratron lifetimes, and the overall system's availability will be analyzed for the period of 1994 to December 2005.
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THXFI01 | State of the Art in EM Field Computation | simulation, gun, dipole, TESLA | 2763 | ||||
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This presentation will provide an up-to-date survey of the methods and tools for the computation of electromagnetic fields in accelerator systems and components.
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THPCH036 | Wakefield Calculations for 3D Collimators | simulation, LEFT, impedance, DESY | 2859 | ||||
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The wakefield effects of the collimators is of concern for future projects. To relax the wakefield effects a gradual transition from a large to a small aperture is used. The impedance of a smooth round collimator is understood well and a good agreement between measurements, theory and simulations is achieved. However, for rectangular flat collimators there is noticeable difference between theory and experiment. Using recently developed time domain numerical approach, which is able to model curved boundaries and does not suffer from dispersion in longitudinal direction, we calculate the short-range geometric wakefields of 3D collimators. This method together with developed by us recently indirect 3D integration algorithm allows to obtain accurate numerical estimations, which are compared to measurements and to analytical results. The applicability range for the analytical formulas is highlighted.
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THPCH072 | Wakefields in the LCLS Undulator Transitions | LCLS, undulator, radiation, linac | 2952 | ||||
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We have studied longitudinal wakefields of very short bunches in non-cylindrically symmetric (3D) vacuum chamber transitions using analytical models and the computer program ECHO. The wake (for pairs of well-separated, non-smooth transitions) invariably is resistive, with its shape proportional to the bunch distribution. For the example of an elliptical collimator in a round beam pipe we have demonstrated thatas in the cylindrically symmetric (2D) casethe wake can be obtained from the static primary field of the beam alone. We have obtained the wakes of the LCLS rectangular-to-round transitions using indirect (numerical) field integration combined with a primary beam field calculation. For the LCLS 1 nC bunch charge configuration we find that the total variation in wake-induced energy change is small (0.03% in the core of the beam, 0.15% in the horns of the distribution) compared to that due to the resistive wall wakes of the undulator beam pipe (0.6%).
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THPCH073 | Reflectivity Measurements for Copper and Aluminum in the Far Infrared and the Resistive Wall Impedance in the LCLS Undulator | LCLS, undulator, impedance, FEL | 2955 | ||||
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Reflectivity measurements in the far infrared, performed on aluminum and copper samples, are presented and analyzed. Over a frequency range of interest for the LCLS bunch, the data is fit to the free-electron model, and to one including the anomalous skin effect. The models fit well, yielding parameters dc conductivity and relaxation times that are within 30-40\% of expected values. We show that the induced energy in the LCLS undulator region is relative insensitive to variations on this order, and thus we can have confidence that the wake effect will be close to what is expected.
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THPCH076 | Resistive Wall Wake Effect of a Grooved Vacuum Chamber | vacuum, impedance, electron, positron | 2961 | ||||
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To suppress the emission of secondary electrons in accelerators with positively charged beams (ions or positrons) it has been proposed to use a vacuum chamber that is longitudinally grooved (or, equivalently, one can say finned)*/**. One consequence of having such a chamber in an accelerator is an increased resistive wall impedance. In this paper, we calculate the resistive wall impedance of one such finned chamber, planned to be used in experimental studies of secondary emission suppression at SLAC. For rectangular fins, we use an analytical method based on a conformal mapping approach; we compare the results with a numerical solution of the field equation. We also numerically compute the impedance for rounded fins (as will be used in the SLAC experiment) and analyse how the impedance depends on geometric properties of the fins.
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*A. A. Krasnov. Vaccum, vol. 73, p. 195, (2004).**G. Stupakov and M. Pivi. Preprint SLAC-TN-04-045, (2004). |
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THPCH089 | The Electromagnetic Background Environment for the Interaction-point Beam Feedback System at the International Linear Collider | feedback, background, target, linear-collider | 2997 | ||||
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The Interaction Point (IP) feedback system is essential for maintaining the luminosity at the International Linear Collider (ILC). It is necessary to demonstrate the performance of the feedback beam position monitor (BPM) in an electron-positron pair background similar to that expected in the ILC interaction region (IR). We have simulated the ILC beam-beam interactions and used a GEANT model of the IR to evaluate the pair and photon flux incident on the BPM, for both the 2 mrad and 20 mrad crossing angle geometries. We present results as a function of the proposed machine parameter schemes, as well as for various system layouts within the IR. We plan to study the degradation of BPM resolution, and the long term survivability, in beam tests at End Station A at SLAC. To simulate the background environment of the ILC a 'spray beam' will be produced, which will scatter from a mechanical mock-up of the forward region of the IR, and irradiate the BPM with realistic flux of secondary pairs. We present the proposed experimental layout and planned beam tests.
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THPCH099 | A Turn-by-turn, Bunch-by-bunch Diagnostics System for the PEP-II Transverse Feedback Systems | feedback, controls, damping, injection | 3026 | ||||
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A diagnostics system centered around commercial fast 8-bit digitizer boards has been implemented for the transverse feedback systems at PEP-II. The boards can accumulate bunch-by-bunch position data for 4800 turns (35 ms) in the x plane and the y plane. A dedicated trigger chassis allows to trigger the data acquisition on demand, or on an injection shot to diagnose injection problems, and provides gating signals for grow-damp measurements. Usually, the boards constantly acquire data and a beam abort stops data acquitision, thus preserving the last 4800 turns of position information before a beam abort. Software in a local PC reads out the boards and transfers data to a fileserver. Matlab-based data analysis software allows to present the raw data but also higher-level functions like spectra, modal analysis, spectrograms and other functions. The system has been instrumental in diagnosing beam instabilities in PEP. This paper will describe the architecture of the system and its applications.
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THPCH100 | New Fast Dither System for PEP-II | feedback, luminosity, controls, closed-orbit | 3029 | ||||
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The PEP-II B-Factory uses multiple feedback systems to stabilize the orbits of its stored beams and to optimize their performance in collision [1]. This paper describes an upgrade to the feedback system responsible for optimizing the overlap of colliding beams at the interaction point (IP). The effort was motivated by a desire to shorten the response time of the feedback, particularly in the context of machine-tuning tasks. We describe the original feedback system, the design for the new one, and give a status report on the installation.
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THPCH120 | Development of a General Purpose Power System Control Board | controls, diagnostics, induction, impedance | 3083 | ||||
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As high frequency switching solid state devices are replacing tube devices and linear devices, power systems become more compact and modular. In those systems, it is desirable to have a high quality and multi-function control board per each power system module. In order to maintain reliable operation of the power system module, the control board requires having multiple and complex functions. Moreover, the control board needs to be compact and low power consuming. It also needs to have a fast communication with the main control station. However, there is no such control board available commercially. Therefore, a general purpose power system control board (PSCB) has been under development since 2005 as a collaboration effort between PAL and SLAC. The PSCB is an embedded, interlock supervisory, diagnostic, timing, and set-point control board. It is designed to use in various power systems such as sequenced kicker pulsers, solid state RF modulators, simple DC magnet power supplies, etc. The PSCB has the Ethernet communication with the TCP/IP Modbus protocol. This paper will describe detail functions and preliminary test results of the PSCB.
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THPCH149 | Active RF Pulse Compression using Electrically Controlled Semiconductor Switches | simulation, coupling, plasma, laser | 3140 | ||||
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In this paper, we present the recent results of our research on the ultra-high power fast silicon RF switch and its application on active X-Band RF pulse compression systems. This switch is composed of a group of PIN diodes on a high purity silicon wafer. The wafer is inserted into a cylindrical waveguide operating in the T·1001 mode. Switching is performed by injecting carriers into the bulk silicon through a high current pulse. Our current design uses a CMOS compatible process and the fabrication is accomplished at SNF (Stanford Nanofabrication Facility). The RF energy is stored in a room-temperature, high-Q 400 ns delay line; it is then extracted out of the line in a short time using the switch. The pulse compression system has achieved a gain of 11, which is the ratio between output and input power. Power handling capability of the switch is estimated at the level of 10MW.
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THPLS085 | Nonlinear Dynamics in the SPEAR 3 Double-waist Chicane | optics, dynamic-aperture, injection, insertion | 3475 | ||||
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A quadrupole triplet has been included in the center of a 7.6 m long chicane in SPEAR 3 to create a novel and technically challenging 'double waist' optics with betay=1.6m at the center of each of two future small-gap insertion devices. The new optics also reduces betay to 2.5m in the four adjacent 4.8m straight sections. In this paper, we discuss key issues associated with design of the machine optics, insertion device compatibility issues, optimization of dynamic aperture and initial measurements of machine performance in the new configuration.
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THPLS097 | Model of the CSR Induced Bursts in Slicing Experiments | laser, CSR, electron, undulator | 3502 | ||||
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In a recent experiment on 'femtoslicing' at the Advanced Light Source in LBNL, it has been observed that the beam slicing initiates correlated bursts of coherent synchrotron radiation (CSR) of the beam. In this paper, we suggest a model describing such bursts. The model is based on the linear theory of the CSR instability in electron rings. We describe how an initial perturbation of the beam generated by the laser pulse evolves in time when the beam is unstable due to the CSR wakefield. Although this model does not give quantitative predictions, it qualitatively explains the evolution of the induced CSR bursts.
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THPLS113 | Design of a Fast Extraction Kicker for the Accelerator Test Facility | kicker, impedance, extraction, damping | 3544 | ||||
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We present a study for the design of a fast extraction kicker to be installed in the Advanced Test Facility ring. The purpose of the project is to test the technologies to be used in the design of the extraction kickers for the ILC damping rings. The kicker's rise and fall times are important parameters in the design of the damping rings, as they limit the minimum distance between bunches and ultimately define a lower boundary for the ring length. We propose a stripline kicker composed of several 20-cm long sections, grouped in two locations in the ATF damping ring. An analytical study of the kicker's parameters and computer simulations using Microwave Studio* point out the strict requirements on the pulsers, in order to be able to satisfy the design parameters.
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*http://www.cst.com |
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