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| MOPKF012 | A 7T Multipole Wiggler in BESSY II: Implementation and Commissioning Results | gun, radiation, damping, alignment | 324 | ||
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To generate hard X-ray beams for residual stress analysis and for magnetic scattering with the BESSY II SR source, a 7T wiggler with 17 poles has been implemented. Several problems had to be solved. Wake fields induced by smaller steps in the geometry of the radiation shield inside the beam chamber led to intolerable LHe consumption, which have been analysed numerically and then cured by improving the shield geometry. Much of the routine operation procedures are influenced by the unusually high radiation power level of max. 55 kW. For system protection an interlock system dumps the electron beam automatically in case of relevant error events. This wiggler is by far the strongest perturbation of the linear beam optics, breaking seriously the symmetry of the ring. Beam optical parameters including tune shift and beta beat have been measured to quantify these perturbations and develop efficient cures to limit the negative effects on beam lifetime and dynamic aperture. So far the wiggler is operated at 2.8 T and max. currents up to 250 mA in normal user shifts.
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| MOPKF013 | The Influence of the Main Coupler Field on the Transverse Emittance of a Superconducting RF Gun | radiation, damping, gun, alignment | 327 | ||
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For the Rossendorf superconducting RF gun project the influence of the additional RF field, created in the cavity by the RF power flow at the main coupler, is discussed. One end of the gun cavity is occupied by the cathode insert, so all flanges are concentrated on the other end. In the "flange plane" of the cavity two HOM coupler, the pic up and the main coupler are located. If we normalize the RF field in the cavity by the condition Eacc = 25MV/m and assume a beam power of 10kW (CW mode), we obtain an quality factor Qext = 2.2*10**7. A three dimensional field calculation using the MAFIA code, gives the field perturbation near the main coupler. Tracking calculation with ASTRA show,that this perturbation increases the transversel emittance between 1 and 4%, nearly independent from the bunch charge. This result shows, that for average beam powers in the vicinity of 10kW effects, connected with the assymetric input of RF power can be neglected.
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| MOPKF014 | Emittance Compensation of a Superconducting RF Photoelectron Gun by a Magnetic RF Field | radiation, damping, gun, alignment | 330 | ||
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For compensation of transverse emittance in normal conducting RF photoelectron guns a static magnetic field is applied. In superconducting RF guns the application of a static magnetic field is impossible. Therefore we put instead of a static field a magnetic RF field (TE - mode) together with the corresponding accelerating mode into the superconducting cavity of the RF gun. For a 3 _ cell cavity of the superconducting gun with frequencies f = 1.3GHz for the accelerating mode and f = 3.9 GHz for the magnetic mode and a bunch charge of 1 nC a transversal emittance of 0.5 mm mrad has been obtained. In this case the maximal field strength on the axis were Ez = 50 MV/m for the accelerating mode and Bz = 0.34 T for the magnetic mode.(This corresponds to Bs(max) = 0.22T on the surface of the cavity). Possibilities for the technical realization (input of RF power for the TE mode, tuning of two frequencies in one cavity, phase stability) are discussed.
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| MOPKF015 | A Superconducting Photo-Injector with 3+1/2- Cell Cavity for the ELBE Linac | radiation, damping, gun, alignment | 333 | ||
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After successful tests of an SRF gun with a superconducting half-cell cavity [*], a new SRF photo-injector for CW operation at the ELBE linac has been designed. In this report the design layout of the SRF photo-injector, the parameters of the superconducting cavity and the expected electron beam parameters are presented. The SRF gun has a 31/2-cell niobium cavity working at 1.3 MHz and will be operated at 2 K. The three full cells have TESLA-like shapes. In the half-cell the photocathode is situated which will be cooled by liquid nitrogen.
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* D. Janssen et. al., First operation of a superconducting RF-gun, Nucl. Instr. and Meth. A507(2003)314 |
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| MOPKF016 | S2E Simulations on Jitter for European XFEL Project | radiation, damping, gun, alignment | 336 | ||
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In order to generate stable 0.1 nm wavelength SASE source at the European X-ray laser project XFEL, we should supply high quality electron beams with constant beam characteristics to a 200 m long undulator. Generally, beam parameters such as peak current and energy spread are significantly dependent on jitter or error in RF phase and RF amplitude of superconducting accelerating modules, and magnetic field error of bunch compressors. In this paper, we describe the start-to-end simulations from the cathode to the end of linac to determine the jitter and error tolerances for the European XFEL project.
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| MOPKF017 | New Simulations on Microbunching Instability at TTF2 | damping, gun, alignment, emittance | 339 | ||
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Microbunching instability in the FEL driver linac can be induced by collective self-fields such as longitudinal space charge, coherent synchrotron radiation, and geometric wakefields. In this paper, we describe the first start-to-end simulations including all important collective self-fields from the cathode to the end of TTF2 linac with 1.5 million macroparticles.
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| MOPKF018 | Injector and Bunch Compressor for the European XFEL Project | damping, gun, alignment, linac | 342 | ||
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For the proper operation of European XFEL project, we should supply high quality electron beams with low emittance, short bunch length, and low energy spread to a 200 m long undulator. In this paper, we describe the optimization and design concepts of the XFEL injector and bunch compressors to control the beam parameter dilution due to the microbunching instability and CSR.
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| MOPKF020 | Proposal for a Sub-100 fs Electron Bunch Arrival-time Monitor for the VUV-FEL at DESY | laser, electron, damping, gun | 345 | ||
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For pump-probe experiments at the VUV-Free Electron Laser at DESY, an external optical laser system will be installed, capable of delivering ultra-short pulses of high intensity. The laser pulses with a center wavelength of 800 nm are synchronized with the VUV-FEL beam which covers the wavelength range between 6 nm and 80 nm. The expected pulse durations are typically 100 fs FWHM or below. For high-resolution pump-probe experiments a precise knowledge of the time difference between both pulses is mandatory. In this paper we describe the layout and the design of a high-precision electron bunch arrival time monitor based on an electro-optic technique. We present the numerical results of simulations that include: the laser propagation in a specifically designed demanding optical system, the laser transport through a 150 m long optical fibre, the electro-optically induced effect in different types of crystals and for different electron bunch shapes as well as the effects of wake fields on the co-propagating electric-fields and their impact on the observable signals.
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| MOPKF021 | Properties of Cathodes Used in the Photoinjector RF Gun at the DESY VUV-FEL | laser, electron, damping, alignment | 348 | ||
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The new injector of the DESY VUV-FEL is being commissioned in spring 2004. Several cathodes have been tested in the photoinjector RF Gun. We report on quantum efficiency, dark current, and the overall appearance of the cathodes after their use.
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| MOPKF022 | Commissioning of the VUV-FEL Injector at TTF | laser, electron, damping, alignment | 351 | ||
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The VUV-FEL at the TESLA Test Facility (TTF) at DESY is being upgraded to an FEL user facility serving high brilliance beams in the wavelength range from the VUV to soft X-rays. The photoinjector has been redesigned to meet the more demanding beam parameters in terms of transverse emittance, peak current, and energy spread. The first phase of the injector upgrade has been finished in spring 2004. We report on its commissioning, including first measurements of beam parameters.
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| MOPKF025 | Planar and Planar Helical Superconductive Undulators for Storage Rings, State of the Art | laser, electron, damping, alignment | 354 | ||
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Planar superconductive undulators for low beam currents were successfully tested in the past. In a next step devices suitable for small gaps in storage rings are in preparation. The tests will clarify experimentally the heat load generated by the beam in the cold bore and will allow to optimize the control system of such devices. In addition, the layout of the next generation of planar superconductive undulators with electrically variable polarization direction are introduced in this paper.
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| MOPKF026 | Conditioning and High Power Test of the RF Guns at PITZ | laser, gun, damping, alignment | 357 | ||
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This paper describes the recent results of conditioning and high power tests of the photocathode RF guns at the Photo Injector Test Facility at DESY Zeuthen (PITZ). For successful operation of high gain SASE FELs, high phase space density of the electron beam is required. A high gradient in the gun has to be applied to improve the quality of the space charge dominated beams. In addition, long RF pulses and high repetition rate should be achieved to provide a high average power of FEL radiation. The first PITZ RF gun has been successfully tested at a mean power of 27 kW (900μseconds, 10 Hz, and 3 MW) and has been installed at the VUV-FEL at DESY Hamburg. Another RF gun has been installed at PITZ in January 2004 and is being conditioned for high power tests. The dark current behavior for various cathodes and for all operating schemes is also presented.
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| MOPKF027 | Optimizing the PITZ Electron Source for the VUV-FEL | electron, damping, alignment, linac | 360 | ||
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The goal of the Photo Injector Test Facility at DESY Zeuthen (PITZ) is to test and optimize electron sources for Free Electron Lasers and future linear colliders. At the end of 2003 the first stage of PITZ (PITZ1) has been successfully completed, resulting in the installation of the PITZ RF gun at the Vacuum Ultra Violet - Free Electron Laser (VUV-FEL) at DESY Hamburg. The main results achieved during the PITZ1 extensive measurement program are discussed in this paper. A minimum normalized beam emittance of about 1.5 pi mm mrad for 1 nC electron bunch charge has been reached by optimizing numerous photo injector parameters, e.g. longitudinal and transverse profiles of the photocathode laser, RF phase, main and bucking solenoid current. The second stage of PITZ (PITZ2), being a large extension of the facility and its research program, has started now. Recent progress on the PITZ2 developments will be reported as well.
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| MOPKF029 | Seeding High Gain Harmonic Generation with Laser Harmonics produced in Gases | damping, alignment, linac, laser | 363 | ||
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Free electron lasers employing High Gain Harmonic Generation (HGHG) schemes are very promising coherent light sources for the soft X-ray regime. They offer both transverse and longitudinal coherence, inversely to Self Amplified Spontaneous Emission schemes, where the longitudinal coherence is limited. We propose here to seed HGHG with high harmonics produced by a Ti:Sa femtosecond laser focused on a gas jet, tuneable in the 100-10 nm spectral region. Specifities concerning the implementation of this particular laser source as a seed for HGHG are investigated. Theoretical ad numerical calculations (using PERSEO in particular) are given, for the cases of the SCSS and ARC-EN-CIEL projects.
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| MOPKF030 | "ARC-EN-CIEL" a Proposal for a 4th Generation Light Source in France | damping, alignment, laser, photon | 366 | ||
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An accelerator based 4th generation source is proposed to provide the user community with coherent femtosecond light pulses in the UV to X ray range. The project is based on a CW 700 MeV superconducting linac delivering high charge, subpicosecond, low emittance electron bunches with high repetition rate. This facility allows for testing High Gain Harmonic Generation seeded with high harmonics in gases, as well as the standard SASE mode, covering a spectral range down to 0.8 nm and 5 nm respectively. In addition, two beam loops are foreseen to increase the beam current in using the energy recovery technique. They will accommodate undulators for the production of femtosecond synchrotron radiation in the IR, VUV and X ray ranges together with a FEL oscillator in the 10 nm range.
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| MOPKF031 | SOLEIL Insertion Devices: The Progress Report | insertion, vacuum, radiation, damping | 369 | ||
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The French national synchrotron radiation source SOLEIL is planned to start operation in 2006 with several different insertion devices installed in the storage ring either from "day one" or within the first year. The list of high-priority insertion devices includes: 3 planar hybrid in-vacuum undulators with the period of 20 mm; 3 Apple-II type PPM undulators with the period of 80 mm; 3 electromagnet elliptical undulators with the period of 256 mm, and a 640 mm period elliptical electromagnet undulator offering advanced possibilities for fine-tuning of polarization states of the emitted radiation. The emission of all these undulators is covering wide spectral range extending from hard X-rays to UV. Pre-design of the IDs was done by SOLEIL. The construction will be done by industrial companies and institutions with production capabilities. Magnetic assembly of the Apple-II and in-vacuum undulators is planned to be done in collaboration with ELETTRA and ESRF. The final magnetic measurements of all the IDs will be made in the SOLEIL magnetic measurements laboratory. The paper will present peculiarities of the magnetic design, calculated maximum-flux spectra and associated heat load in various modes of operation.
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| MOPKF032 | Status of the ESRF Insertion Devices | undulator, radiation, damping, alignment | 372 | ||
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The ESRF insertion devices are the object of a continuous refurbishment in order to follow the changing needs of the beamlines and increase their performances. The successful development of the narrow aperture aluminum chambers pumped by non evaporable getter has resulted in the reduction of the minimum gap from 16 mm to 11 mm . A new set of undulator magnetic assemblies with shorter magnetic periods are being prepared that make use of the lower gap. .A prototype of a new type of revolver undulator support has been completed and successfully tested. Such a structure allows the beamline user to switch between two different undulator periods in less than a minute. Three additional devices will be constructed in 2004. Three new in-vacuum undulators have been installed on the ring. One of them is based on an hybrid magnetic structure and achieves a peak field 20% higher than a pure permanent magnet undulator of identical period. Their main magnetic measurements results and interactions with the stored beam are presented.
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| MOPKF033 | Operational Improvements in the ESRF Injection Complex | injection, undulator, booster, radiation | 375 | ||
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The ESRF injection complex, comprising a 200MeV linac, a booster accelerator with a top energy of 6GeV and two transfer lines, has been routinely injecting beam to the storage ring since the beginning of its operation. The newly implemented injection with ‘‘front-end open'' triggered several operational improvements in order to maximise the reliability of the complex. A series of diagnostics (sychnotron light monitors, striplines, fast current transformers) were implemented allowing the measurement and monitoring of several components of the injected beam. New optics models were constructed and several application systems as the closed orbit correction or tune measurements have been upgraded. The operational procedures of injection at 100MeV in the booster and the injection efficiency maximisation were renewed and improved. Further developments for the uninterrupted operation of the storage ring during injection, such as the bunch cleaning in the booster were successfully tested.
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| MOPKF034 | Status of the Development of Superconducting Undulators at the ESRF | injection, undulator, booster, radiation | 378 | ||
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This note describes the present status of the development of superconducting undulators at the ESRF. Magnetic models of superconducting undulators suitable for the ESRF storage ring have been developed and evaluated. The superconducting undulators studied are horizontally polarizing undulators with a flat field profile and the vertical physical aperture of the undulator is 6 mm. Both 2D models of the local field in a period of the undulator and 3D models of the complete superconducting undulator, including the end sections and current leads, have been evaluated. The practical limit for the obtainable magnetic field has been estimated from the known performance of superconducting wire available from the cabling industry. This note also describes the conceptual design of the cryostat of the superconducting undulator and estimations of the expected heat load to the cryostat at different filling modes of the storage ring.
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| MOPKF035 | Stabilization of the Pulsed Regimes on Storage Ring Free Electron Laser: The Cases of Super-ACO and Elettra | injection, booster, electron, damping | 381 | ||
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In a Storage Ring Free Electron Laser (SRFEL) a relativistic electron beam interacts with the magnetostatic periodic field of an undulator, thus emitting synchrotron radiation. The light is stored in an optical cavity and amplified during successive turns of the particles in the ring. The laser intensity may appear as a "continuous wave (cw)" or show a stable pulsed behaviour depending on the value of the temporal detuning, i.e. the difference between the electron beam revolution period and the round trip of the photons in the cavity. It was recently shown, that the loss of stability in a SRFEL occurs through an Hopf bifurcation [*]. This observation opens up the perspective of introducing a derivative self-controlled feedback to suppress locally the bifurcation and enlarge the region of stable signal. A feedback of this type has been implemented on Super-ACO and shown to produce a significant and reproducible extension of the stable "cw" region. We review here these results and discuss new experiments performed on the Super-ACO and ELETTRA SRFELs.
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* G. De Ninno and D. Fanelli, Phys. Rev. Lett. in press; M.E. Couprie et al. Nucl. Instrum.and Meth. A., in press |
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| MOPKF036 | Wideband Infrared FEL | injection, undulator, booster, vacuum | 384 | ||
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The infrared free-electron laser offers the advantage of a potential large tunability since the FEL gain itself remains subtantially high throughout the infrared spectral range, provided that the electron beam quality remains sufficient at low energy. Moreover, the reflectivity of metal mirrors used in the optical cavity remains close to unity from the near infrared up to the microwave range. The main limitation comes from the diffraction of the optical beam due to the finite size of the vacuum chamber of the undulator and other optical cavity elements. The undulator magnetic gap, and thus magnetic chamber inner heigth, cannot be made arbitrarily large since one needs a K parameter sufficiently large to produce a large wavength tunability (typically K > 2). The diffraction losses can however be further reduced by using an elliptical vacuum chamber inside the undulator and elliptical, instead of spherical, mirrors. Then the optical beam is partially guided inside the chamber. Working in this regime at CLIO, we have obtained an FEL tunable from 3 to 120 μm by operating the accelerator between 50 and 14 MeV. This is the largest spectral range ever obtained with a single optical cavity. We plan to use larger mirrors to further reduce the diffraction produced at the edges of the undulator chambers in order to increase the maximum wavelength to approximately 200 μm
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| MOPKF037 | FERMI@ELETTRA: 100 nm - 10 nm Single Pass FEL User Facility | injection, booster, linac, vacuum | 387 | ||
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The FERMI@ELETTRA project is an initiative from ELETTRA, INFM and other Italian institutes, to construct a single-pass FEL user-facility for the wavelength range from 100 nm (12 eV) to 10 nm (124 eV), to be located next to the third-generation synchrotron radiation facility ELETTRA in Trieste, Italy. The project is concentrated around the existing 1.2-GeV S-band linac, i.e., the injector for the storage ring. Presently the linac is only operational for approximately 2 hours per day. The remaining time is available for the construction and operation of an FEL but modifications and operation must be planned such that operation of the storage ring can be guaranteed until the completion of a new full-energy injector (spring 2006). At this moment the FEL project evolves from a conceptional design stage towards a technical design and the actual implementation. Key issues are: incorporation of the free-electron laser in the infrastructure of the Sincrotrone Trieste, adjustments of the linac to facilitate FEL operation, required additional civil engineering, undulator design, FEL seeding options, and beamline design. This paper serves as an overview of the project in combination with a discussion of the critical issues involved.
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| MOPKF050 | Current Heart-like Wiggler | injection, linac, booster, cathode | 423 | ||
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A new wiggler structure for free electron lasers is presented. Current hart-like wiggler produced magnetic fields which were spatially periodic. The current wiggler structure was in the shape of stacks of modified circle wires. The current had alternating directions. The magnetic field components for each wire present a C2 symmetry (for a model with 3 branches). The wiggler transverse cross - section in arbitrary units was given by the following expressions: x = R(d+sin(3j))cos(j) , y = R(d+sin(3j))sin(j) , z = constant, where d and R are the parameters. In cylindrical coordinates the Biot - Savart law was evaluated numerically. The magnetic field aspect was mainly transversal and also easily adjusted with the current . The versatility of this structure permits new geometrical forms and developments in the wiggler and wiggler design .
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| MOPKF052 | Design of an In Archromatic Superconducting Wiggler at NSRRC | injection, linac, booster, cathode | 425 | ||
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A 15-pole superconducting wiggler with period length of 6 cm is designed for National Synchrotron Research Center (NSRRC) in Taiwan. The compact superconducting wiggler will be installed near the second bending magnet of the triple bend achromat section in the 1.5 GeV storage ring. This wiggler magnet with maximum peak field of 3.2 T at pole gap width of 19 mm is operated in 4.2 K liquid helium vessel. A 5-pole prototype magnet is tested and measured to verify the magnetic field performance in the testing dewar. Furthermore, the cryogenic considerations and thermal analysis in the 4.2 K wiggler magnet and the 77 K vacuum chamber are also presented in this work.
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| MOPKF053 | Pulsed-wire Method of Field Measurement on Short Elliptically Polarized Undulator | injection, linac, booster, cathode | 428 | ||
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With two sets of photo illuminator and detector, scientists already have applied pulsed-wire method to measure the magnetic field along two mutually perpendicular directions. Two-dimensional pulsed-wire method is useful for the test of elliptically polarlized undulator (EPU). We tried to use this method to observe the first integral and second integral fields of a short EPU in real time during the polarization tuning. We have taken care more details than the pulsed-wire measurement of planner undulators. The phase difference, the relative field strength along two direction as well as the precise centerline can be achieved.
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| MOPKF054 | Generation of Femtosecond Electron Pulses | injection, booster, radiation, cathode | 431 | ||
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Femtosecond electron pulses have become an interesting tool for basic and applied applications, especially in time-resolved experiments and dynamic studies of biomolecules. Intense, coherent radiation can be generated in a broad far-infrared spectrum with intensities, which are many orders of magnitude higher than conventional sources including synchrotron radiation sources. At the Fast Neutron Research Facility (FNRF), Chiangmai University (Thailand), the SURIYA project has been established with the aim to produce femtosecond pulses utilizing a combination of a S-band thermionic rf-gun and an alpha-magnet as the magnetic bunch compressor. A specially designed rf-gun has been constructed to obtain the optimum beam characteristics for best bunch compression. Simulation results show that the bunch lengths as short as 50 fs rms can be expected at the experimental station. This rf- gun, an alpha-magnet and a 20 MeV linac with beam transport system were installed and are being commissioned to generate femtosecond electron bunches. To measure the bunch length of the electron pulses, a Michelson interferometer will be used to observe the spectrum of coherent FIR transition radiation via optical autocorrelation. The main results of numerical simulations and experimental results will be discussed in this paper.
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| MOPKF055 | A Study of CSR Induced Microbunching Using Numerical Simulations | injection, booster, bunching, cathode | 434 | ||
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Microbunching due to Coherent Synchrotron Radiation (CSR) has been predicted for high density bunches and has been 'observed' using numerical simulations by the code ELEGANT of M. Borland, which includes a 1D model of CSR. However, there is currently a debate as to whether this micro-bunching is a real physical effect or is a numerical artefact, possibly introduced by having to use macro-particles to model the electrons. In particular, the amplitude of the micro-bunching diminishes as the number of macroparticles increases, but the question remains open as to whether the amplitude converges to zero or a finite value. The micro-bunching produced by ELEGANT is being studied as a function of the numerical parameters of the code and also as a function of the range of bunch parameters and bending magnet strengths of relevance to the 180 degree bending arcs required for the proposed 4GLS at Daresbury Laboratory. Calculations with up to 2 million macroparticles have been carried out on a Linux workstation using gaussian bunches of FWHM of 2psec and charge of 1 nC, and show the existence of microbunching at the end of a 180 degree arc containing 5 TBA cells with magnet strengths of 0.5T. Further investigation of this problem is required.
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| MOPKF056 | Injector Design for the 4GLS Energy Recovery Linac Prototype | injection, bunching, cathode, gun | 437 | ||
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Daresbury Laboratory has been given funding for the construction of an Energy Recovery Linac Prototype (ERLP) that operates at a target electron beam energy of 35 MeV and drives an IR oscillator FEL. The ERLP serves as a test-bed for the study of beam dynamics and accelerator technology important for the design and construction of the proposed 4th Generation Light Source (4GLS). A key component of the ERLP is a high-brightness injector. The injector consists of a DC photocathode gun, which is currently being built at Daresbury Laboratory and based on the design of the gun for the IR demonstrator FEL at Thomas Jefferson National Accelerator Facility. The gun section is followed by a conventional buncher cavity, a super-conducting booster and a transfer line to the main linac. In this paper, the design of the ERLP injector is discussed. The performance of the injector has been studied using the particle tracking code ASTRA.
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| MOPKF058 | Construction of an APPLE-II Type Undulator at Daresbury Laboratory for the SRS | injection, bunching, cathode, gun | 440 | ||
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A new variable polarisation undulator of the APPLE-II type has been designed and constructed at Daresbury Laboratory. Testing of the 56mm period device has recently started in the new Magnet Test Facility at Daresbury Laboratory. This paper presents the magnetic and mechanical design of the undulator, and the first magnetic measurement results.
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| MOPKF059 | Magnet Specification for the Daresbury Laboratory Energy Recovery Linac Prototype | bunching, cathode, gun, insertion | 443 | ||
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Daresbury Laboratory has funding for the design and construction of an Energy Recovery Linac (ERL) prototype to facilitate the R&D necessary for the 4th Generation Light Source (4GLS). In the prototype a 35MeV electron beam will be used to drive an Infra-Red Oscillator Free-Electron Laser. The ring consists of two 180°; triple bend achromats, two straight sections, an injection chicane, an extraction chicane and two bunch compression/decompression chicanes. A number of pre-existing magnets will be used in the ring so the new magnets have been designed to ensure compatibility with the existing designs, enabling common power supply, vacuum and control system specifications. This paper gives an overview of the magnet requirements for the facility and details of the engineering realisation.
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| MOPKF060 | Space Charge Effects for the ERL Prototype at Daresbury Laboratory | bunching, cathode, gun, insertion | 446 | ||
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Daresbury Laboratory is currently building an Energy Recovery Linac Prototype (ERLP) that will operate at a beam energy of 35 MeV. In this paper we examine the Space Charge effects on the beam dynamics in the ERLP injector line. This is done in two distinct ways. The first is based on an analytic formula derived by Vinokurov through the envelope equations and a Kapchinsky-Vladimirsky (KV) distribution. This formula gives a rough estimate of the space charge effects in the case that no quadrupoles or dipoles are present in the injector line. The second estimate is given by the multi-particle tracking code ASTRA for the whole injector line both with and without quadrupoles. Both methods are compared and are found to be in good agreement. Typical examples of injector lines are given together with specific calculations for the ERLP.
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| MOPKF061 | Optics Layout for the ERL Prototype at Daresbury Laboratory | bunching, cathode, gun, insertion | 449 | ||
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The overall optics for the Energy Recovery Linac Prototype (ERLP) at Daresbury Laboratory is summarised. This includes the layout of the injector line, all chicanes used, as well as details of both the outward and return TBA arcs. The tunability in several sections of the machine is examined under different operational modes and starting parameters from the end of the booster to the dump.
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| MOPKF062 | Choice of Arc Design for the ERL Prototype at Daresbury Laboratory | bunching, cathode, gun, insertion | 452 | ||
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The choice of arc design for the Energy Recovery Linac Prototype (ERLP) to be built at Daresbury Laboratory is investigated. Both the overall merits and disadvantages of a TBA arc and Bates bend are considered, and space restrictions particular to Daresbury Laboratory given. Some magnet parameters are given together with a summary of the layout of the ERLP.
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| MOPKF063 | 4GLS and the Prototype Energy Recovery Linac Project at Daresbury | bunching, cathode, gun, insertion | 455 | ||
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The 4GLS project is a novel next generation solution for a UK national light source proposed to be sited at Daresbury. It is based on an energy recovery linac (ERL) operating at high average beam currents up to 100mA and with compression schemes producing pulses in the 10-100 fs range. This would provide a unique spontaneous emission source with high average brightness output both from undulators and bending magnets. In addition to this operating regime a high peak current mode would also be possible at lower duty cycle, enabling a high gain FEL amplifier to generate XUV radiation. Longer wavelength FELs are also planned. This challenging accelerator technology, new to Europe, necessitates a significant R&D programme and as a major part of this a low energy prototype, the ERLP, is being constructed at Daresbury. The paper summarises the ERLP design specification, describes the component solutions adopted and explains the 4GLS project status and plans.
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| MOPKF064 | Design Considerations for a Helical Undulator for the Production of Polarised Positrons for TESLA | bunching, cathode, gun, insertion | 458 | ||
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An efficient and simple method for the production of positrons, in the necessary quantities, is one of the problems facing proposals for any future e+ e- Linear Collider project. The possibility of colliding polarised beams would also be an advantage. One method to produce a polarised positron beam uses circularly polarised radiation generated by the main electron beam passing through a helical undulator. Design considerations and calculations for two undulators, based on super-conducting and pure permanent magnet technologies, for the TESLA machine, are presented.
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| MOPKF065 | Magnet Block Sorting for Variably Polarising Undulators | bunching, cathode, gun, insertion | 461 | ||
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Effective sorting of permanent magnet blocks for undulators can reduce the adverse effects of magnetic in-homogeneities and engineering tolerances on the electron beam. For variably polarising undulators the number of different modes of operation make defining the objective function of a particular permutation more difficult than for a planar device. Factors required in defining a good objective function for a new APPLE-II type helical undulator for the SRS are discussed. These factors include calculating the magnetic field integrals, the particle trajectory and rms optical phase error. The effects of different weighting of these functions in the objective function are also discussed. A comparison of different optimisation techniques, including simulated annealing and Monte Carlo methods is also made.
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| MOPKF066 | Magnetic Design of a Focusing Undulator for ALPHA-X | undulator, bunching, cathode, gun | 464 | ||
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ALPHA-X is a four-year project shared between several research groups in the UK to build a laser-plasma accelerator and produce coherent short-wavelength radiation in an FEL. The FEL undulator will be a 1.5m long, 100 period permanent magnet device with a minimum gap of 3.5mm and a peak field of 0.7T. To focus the beam inside the undulator, several schemes were examined. In the scheme that was selected, the magnet blocks are designed so that the pole face is an approximation of a parabola. This focuses the beam horizontally and vertically. The magnetic design of the undulator is complete; design of the support structure is well under way. Test pieces have been built to ensure that the clamping arrangement is strong enough to cope with the magnetic forces involved. The complete undulator will be built in late 2004 at Daresbury Laboratory, and tested on-site in the new magnet test facility.
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| MOPKF067 | Comparison of Different Buncher Cavity Designs for the 4GLS ERLP | undulator, bunching, cathode, gun | 467 | ||
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A DC photocathode gun is part of the injector of the Energy Recovery Linac Prototype (ERLP) currently built at Daresbury Laboratory. A buncher is required for the ERLP to decrease the bunch length off the gun. Three different single-cell cavity designs were investigated: The Cornell buncher, the Elbe Buncher and an EU cavity without Higher Order Mode (HOM) dampers. The properties of these cavities were studied with the computer codes CST's Microwave Studio and ASTRA. The fundamental frequency and field pattern was investigated in Microwave Studio. The EU cavity had to be scaled from 500MHz as the required frequency for the buncher is 1.3GHz. As the anticipated kinetic energy of the electron beam after the gun is about 350keV a particle tracking code including the space charge forces is mandatory to study the effect of the different buncher cavity designs on the beam dynamics. The particle tracking code ASTRA was used to study the performance of the bunchers for a variety of beam parameters. From these investigations it was found that the three bunchers produce very similar effects on the particle bunch.
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| MOPKF068 | Experimental Study of the Stability Margin with Beam Heating in a Short-Period Superconducting Undulator for the APS | undulator, bunching, cathode, gun | 470 | ||
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A superconducting undulator with a period of 15 mm is under development at the Advanced Photon Source (APS). The undulator is designed to achieve a peak field on the beam axis of 0.8 T with an 8 mm pole tip gap and an NbTi coilpack current density of 1 kA/mm2. Because of the high current density in the coilpack, the superconducting magnet operates at about 75% of the short sample limit at 4.2K. Additional heat load to the coilpack, mainly due to the image currents and synchrotron radiation from the electron beam in the storage ring, will reduce the stability margin. An experiment was conducted to measure the reduction in the stability margin of the coilpack due to heat load on the beam chamber. The heat load was deposited in a 12-period prototype undulator using thin-film heaters attached to the inner surface of a simulated vacuum chamber. Evaluation of the stability margin based on the experiment and calculations of the beam heating and thermal conduction between the undulator and beam chamber will be discussed.
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| MOPKF069 | Engineering Design of the LUX Photoinjector | undulator, bunching, cathode, gun | 473 | ||
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The photoinjector for the LBNL LUX project, a femtosecond-regime X-ray source, is a room-temperature 1.3 GHz 4-cell structure producing a 10 MeV, nominal 30 psec, 1 nanocoulomb electron bunch at a 10 kHz rate. The first cell is of reentrant geometry, with a peak field of 64 MV/m at the photocathode surface, the geometry of which will be optimized for minimum beam emittance. The high repetition rate and high peak power results in a high average surface power density. The design of the cavity, its cooling structure and power couplers, is coordinated with the configuration of the RF system, including a short, high-power driving pulse and active removal of stored energy after the beam pulse to reduce the average power dissipated in the cavity. An RF and thermal analysis will be presented, along with plans for a high average and peak power test of the first cell.
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| MOPKF070 | Design of Injector Systems for LUX | undulator, bunching, cathode, insertion | 476 | ||
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The LUX concept [1] for a superconducting recirculating linac based ultrafast x-ray facility features a unique high-brightness electron beam injector. The design of the injector complex that meets the baseline requirements for LUX are presented. A dual-rf gun injector provides both high-brightness electron beams to drive the cascaded, seeded harmonic generation VUV-soft x-ray FELs as well as the ultra- low-vertical emittance ('flat') beams that radiate in hard x-ray spontaneous emission synchrotron beamlines. Details of the injector complex design and performance characteristics are presented. Contributions by the thermal emittance and optical pulse shaping to the beam emission at the photocathode and to the beam dynamics throughout the injector are presented. Techniques that seek to optimize the injector performance, as well as constraints that prevent straightforward optimization, are discussed.
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| MOPKF071 | Study of Row Phase Dependent Skew Quadrupole Fields in Apple-II type EPUs at the ALS | undulator, bunching, cathode, insertion | 479 | ||
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Since about 5 years, Apple-II type Elliptically Polarizing Undulators (EPU) have been used very successfully at the ALS to generate high brightness photon beams with arbitrary polarization. However, both EPUs installed so far cause significant changes of the vertical beamsize, especially when the row phase is changed to change the polarization of the photons emitted. The effect has been measured in detail and turned out to be caused by a row phase dependent skew quadrupole term in the EPUs. Magnetic measurements revealed the same effect for the third EPU to be installed later this year. All measurements to identify and quantify the effect with beam will be presented, as well as results of magnetic bench measurements and numeric field simulations.
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| MOPKF072 | Towards Attosecond X-ray Pulses from the FEL | undulator, bunching, cathode, laser | 482 | ||
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The ability to study ultrafast phenomena has been recently advanced by the demonstrated production and measurement of a single, 650-attosecond, soft x-ray pulses precisely synchronized to the pump laser pulse consisted of just few optical cycles. The next frontier is a production of attosecond x-ray pulses at even shorter wavelengths. Here we propose the method of ?seeded attosecond x-ray radiation? where an isolated, attosecond duration, short-wavelength x-ray pulse is radiated by electrons selected by their previous interaction with a few-cycle, intense laser pulse. In principle this method allows excellent synchronization between the attosecond x-ray probe pulse and a pump source that can be the same few-cycle laser pulse or another signal derived from it.
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| MOPKF073 | Design Study of the Bending Sections between Harmonic Cascade FEL Stages | undulator, cathode, laser, insertion | 485 | ||
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The present design of LUX (linac based ultra-fast X-ray facility) includes a harmonic cascade FEL chain to generate coherent EUV and soft X-ray radiation. Four cascade stages, each consisting of two undulators acting as a modulator and a radiator, respectively, are envisioned to produce photons of approximate wavelengths 48 nm, 12 nm, 4 nm and 1 nm. Bending sections may be placed between the modulator and the radiator of each stage to adjust and maintain bunching of the electrons, to separate, in space, photons of different wavelengths and to optimize the use of real estate. In this note, the conceptual design of such a bending section, which may be used at all four stages, is presented. Preliminary tracking results show that it is possible to maintain bunch structure of nm length scale in the presence of errors, provided that there is adequate orbit correction and there are 2 families of trim quads and trim skew quads, respectively, in each bending section.
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| MOPKF074 | Harmonic Cascade FEL Designs for LUX | electron, cathode, laser, insertion | 488 | ||
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LUX is a proposed facility for ultrafast X-ray science, based on an electron beam accelerated to GeV energies in a recirculating linac. Included in the design are short duration (200 fs or shorter FWHM) light sources using multiple stages of higher harmonic generation, seeded by a 190–250 nm laser of similar duration. This laser modulates the energy of a group of electrons within the electron bunch; this section of the electron bunch then produces radiation at a higher harmonic after entering a second, differently tuned undulator. Repeated stages in a cascade yield increasing photon energies up to 1 keV. Most of the undulators in the cascade operate in the low-gain FEL regime. Harmonic cascades have been designed for each pass of the recirculating linac up to a final electron beam energy of 3.1 GeV. For a given cascade, the photon energy can be selected over a wide range by varying the seed laser frequency and the field strength in the undulators. We present simulation results using the codes GENESIS and GINGER, as well as the results of analytical models which predict FEL performance. We discuss lattice considerations pertinent for harmonic cascade FELs, as well as sensitivity studies and requirements on the electron beam.
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| MOPKF076 | An Overview of the Cryomodule for the Cornell ERL Injector | electron, cathode, laser, insertion | 491 | ||
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The first stage of the Cornell ERL project will be a 100 MeV, 100 mA (CW) prototype machine to study the energy recovery concept with high current, low emittance beams. In the injector, a bunched 100 mA, 500 keV beam of a DC gun will be compressed in a normal-conducting copper buncher and subsequently accelerated by five superconducting 2-cell cavities to an energy of 5.5 MeV. We will present an overview of the injector status to include the status of the cryomodule design along with the status of the 2-cell HOM-free cavity, the twin-input coupler and the ferrite HOM dampers in related papers.
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| MOPKF077 | Reducing the Synchrotron Radiation on RF Cavity Surfaces in an Energy-recovery Linac | electron, linac, radiation, cathode | 494 | ||
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In Energy Recovery Linac (ERL) light sources, a high energy, high current beam has to be bend into a superconducting linac to be decelerated. The synchrotron radiation produced in the last bending magnet before the linac shines into the superconducting structures if not collimated appropriately. Due to the length of the linac, the radiation cannot be completely guided through the superconducting structure, as in existing SRF storage rings. For the example of an ERL extension to the existing CESR storage ring at Cornell we estimate the magnitude of this problem by quantifying the heat load that can be accepted on a superconducting surface and by analyzing how much radiation is deposited on the cavity surfaces for different collimation schemes.
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| MOPKF078 | ERL Upgrade of an Existing X-ray Facility: CHESS at CESR | electron, cathode, linac, laser | 497 | ||
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CORNELL has proposed an Energy-Recovery Linac (ERL) based synchrotron-light facility which can provide improved x-ray radiation due to the high beam quality that can be available from a linac. To additionally utilize beam currents that are competitive with ring-based light sources, the linac has to operate with the novel technique of energy recovery, the feasibility of which CORNELL plans to demonstrate in a downscaled prototype ERL. Here we present an ERL upgrade of the existing 2nd generation light source CHESS at CESR. This proposed upgrade suggests how existing storage rings can be extended to ERL light sources with much improved beam qualities.
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| MOPKF079 | The Linac Coherent Light Source Photo-Injector Overview and Some Design Details | linac, cathode, gun, insertion | 500 | ||
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The Linac Coherent Light Source (LCLS)[*] is a SASE free electron laser using the last 1/3 of the SLAC two mile linac to produce 1.5 to 15 angstrom x-rays in a 100 meter long undulator. A new 135 MeV photo-injector will be built in an existing, off-axis vault at the 2/3 point of the main linac. The injector accelerator consists of a BNL/SLAC/UCLA s-band gun followed by two 3-meter long SLAC accelerator sections. The 5.6 MeV beam from the gun is matched into the first accelerator section and accelerated to 135 MeV before injection onto the main linac axis with a 35 degree bend [**]. Several modifications have been made to the rf gun, linac and beamline as well as the inclusion of several diagnostics have been incorporated into the injector design to achieve the required 1.2 micron projected emittance at a charge of 1 nC. In addition, a laser heater [***], will increase the uncorrelated energy spread to suppress coherent synchrotron radiation and longitudinal space charge instabilities in the main accelerator and bunch compressors [****]. The configuration and function of the major injector components will be described.
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* Linac Coherent Light Source (LCLS) CDR No. SLAC-R-593 UC-414, 2002 ** C. Limborg et al., Proc. of the 2003 International FEL Conf *** R. Carr et al, Contrib. to these proceedings **** Z. Huang et al., Contrib. to these proceedings |
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| MOPKF080 | Controlling Emittance Growth in an FEL Beam Conditioner | linac, cathode, gun, electron | 503 | ||
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It has been proposed [*] to 'condition' an electron beam prior to the undulator of a Free-Electron Laser (FEL) by increasing each particle's energy in proportion to the square of its transverse betatron amplitude. This conditioning enhances FEL gain by reducing the axial velocity spread within the electron bunch. Previosly [**] we presented a system that allows conditioning of the beam on a relatively short distance, however, it suffers from projected beam emittance growth to the extent that makes it impractical for application for X-ray FELs. In this paper we extend analysis proposed by A. Wolski for general requirements to the conditioner which does not have such emittance growth. We also present a possible implementation of a beam conditioner consisting of multiple solenoid cells in combination with quadrupole magnets. Simulations show that in such a system the emittance growth can be suppressed to acceptable level, albeit in a longer system.
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* A. Sessler et al., Phys. Rev. Lett., 68, 309 (1992).** P. Emma and G. Stupakov. PRSTAB, 6, 030701 (2003). |
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| MOPKF081 | Peak Current Optimization for LCLS Bunch Compressor 2 | linac, cathode, gun, electron | 506 | ||
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The performance of an FEL will be a function of both the driving bunch's current and its slice emittance. We have studied a set of parameters for the bunch compression section of the LCLS, simulating the effects of Coherent Synchrotron Radiation (CSR) on the slice emittance of the bunch core as a function of peak current. We use the code TraFiC4 for a three-dimensional, self-consistent simulation on parallel computers. While higher currents will increase FEL performance, its detrimental effects, due to CSR, on slice emittance will counteract this beneficial effect. From our simulations, we determine a near-optimum current, balancing these effects.
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| MOPKF082 | A Multi-bunch, Three-dimensional, Strong-strong Beam-beam Simulation Code for Parallel Computers | linac, cathode, gun, electron | 509 | ||
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We have developed a parallel simulation code allowing the self-consistent, three-dimensional simulation of the strong-strong beam-beam effect, using a particle-on-mesh technique and fast elliptic solvers. It is able to operate with sufficiently high logitudinal resolution to treat phase-averaging and hourglass effects in the interaction point (IP) correctly. This code has been generalized to handle the collisions of an arbitrary set of bunches at arbitrary positions in the ring (parasitic crossings), using appropriately reduced longitudinal resolution of collisions not in the design IP. We provide benchmarking results and parameter studies based on PEP-II.
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| MOPKF083 | Inverse Free Electron Laser Heater for the LCLS | laser, gun, electron, undulator | 512 | ||
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The LCLS Free Electron Laser employs an RF photocathode gun that yields a 1 nC charge bunch a few picoseconds long, which must be further compressed to yield the high current required for SASE gain. The very cold electron beam from the RF photocathode gun is quite sensitive to microbunching instabilities such as coherent synchrotron radiation (CSR) in the compressor chicanes and longitudinal space charge (LSC) in the linac. These effects can be Landau damped by adding energy spread to the electron bunch prior to compression. We propose to do this by interacting an infrared laser beam with the electron bunch in an undulator added to the LCLS gun-to-linac injector. The undulator is placed in a 4-bend chicane to allow the IR laser beam to propagate co-linearly with the e-beam while it oscillates in the undulator. The IR laser beam is derived from the photocathode gun laser. Simulations presented elsewhere in these proceedings show that the laser interaction damps the microbunching instabilities to a very great extent. This paper is a description of the implementation of the laser heater
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| MOPKF084 | Beam Instabilities in Lepton Ring of eRHIC | laser, lepton, gun, undulator | 515 | ||
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The eRHIC is a high luminosity lepton-hadron collider planned to be built in Brookhaven National Lab, Upton, New York, USA. The lepton machine of eRHIC is a completely newly designed machine complex to provide highly polarized lepton beams at up to 10 GeV energy for the high luminosity lepton-hadron collisions. This paper decribes major issues of collective effects in this lepton storage ring. Besides conventional impedance-driven instabilities, the electron cloud effects in positron operation and fast beam-ion effects in electron operation are of major conserns. The analytical and numerical estimats for major collective effects are made with different machine operation conditions.
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| MOPKF085 | Design Optimizations of X-ray FEL Facility at MIT | lepton, undulator, cathode, emittance | 518 | ||
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MIT is exploring the construction of a linac-based x-ray laser user facility on the campus of the Bates Linear Accelerator Center. The facility under consideration would span the wavelength range from 100 to 0.3 nm in the fundamental, move into the hard X-ray region in the third harmonic, and preserve the possibility of an upgrade to even shorter wavelengths. The accelerator configuration would include a high brightness electron gun, a superconducting electron linac and multiple undulators and beam lines to support a growing user community. This paper will present the recent progress on the start-to-end simulations including the parameter optimizations and sensativity analysis.
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| MOPKF086 | Modifications of the LCLS Photoinjector Beamline | lepton, undulator, cathode, damping | 521 | ||
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The LCLS Photoinjector beamline is now in the Design and Engineering stage. The fabrication and installation of this beamline is scheduled for the summer 2006. The Photoinjector will deliver 10 ps long electron bunches of 1nC with a normalized transverse emittance of less than 1 mm.mrad for 80% of the slices constituting the core of the bunch at 135 MeV. In this paper, we describe some modifications of the beamline: new exit energy, additional focusing, insertion of a laser heater. We also describe an alternate tuning which is based on a laser pulse of 20ps. The advantages and drawbacks of this long pulse tuning are reviewed. A comparison of sensitivity to field errors and misalignment between the long pulse tuning and the nominal tuning is given.
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| MOPKF087 | The Cebaf Energy Recovery Experiment: Update and Future Plans | lepton, undulator, cathode, damping | 524 | ||
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A successful GeV scale energy recovery demonstration with a high ratio of peak-to-injection energies (50:1) was carried out on the CEBAF (Continuous Electron Beam Accelerator Facility) recirculating superconducting linear accelerator in the spring 2003. To gain a quantitative understanding of the beam behavior through the machine, data was taken to characterize the 6D phase space during the CEBAF-ER (CEBAF with Energy Recovery) experimental run. The transverse emittance and energy spread of the accelerating and energy recovered beams were measured in several locations to ascertain the beam quality preservation during energy recovery. Measurements also included the RF system's response to the energy recovery process and transverse beam profile of the energy recovered beam. One of the salient conclusions from the experiment is that the energy recovery process does not contribute significantly to the emittance degradation. The current status of the data analysis will be presented as well as plans for a GeV scale energy recovery experimental run with current doubling.
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| MOPLT001 | Acceleration of Electrons by Spatially Modulated Laser Wave | acceleration, lepton, undulator, cathode | 527 | ||
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We study the acceleration of electrons in a system of linearly polarized laser wave, propagating at small angles to the direction of electron motion. The parameters of electron bunch and laser wave are chosen so, that during driving electrons in a band of a wave, the electric field of a wave has not changed the direction. The requirements of deriving of maximum rate of acceleration are found depending on parameters of electronic bunch and laser wave. It is shown, that the dependence of growth of electrons energy from number of light bands has nonlinear character. The influence of light diffraction on process of acceleration is considered. It is shown, that the discussed scheme of acceleration allows a possibility of deriving of high acceleration rate owing to existence of modern powerful lasers.
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| MOPLT003 | Upgrading the LNLS Control System from a Proprietary to a Commercial Communications Environment | acceleration, lepton, undulator, cathode | 530 | ||
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The LNLS Control System was built over a proprietary technology, due to governmental policy of information technology in the mid 80's. This made interfacing to commercial systems difficult, limited the technology transfer to the private sector, required a staff with specific knowledge and reduced the possibility of new implementations on the system. Nowadays, the cost to move all of our hardware to a commercial one is out of our budget. This paper describes a proposal, the viability study and first results to move only the communication interfaces to a commercial environment, keeping most of our hardware unchanged and opening the way to gradually move the system to widely accepted standards, when and if necessary. This solution allows a smooth implementation without long periods of machine shutdown and keeps the possibility to operate the machine concurrently between old and new communication interfaces.
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| MOPLT004 | Control of the LHC 400 MHz RF System (ACS) | acceleration, lepton, undulator, cathode | 533 | ||
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The LHC ACS RF system is composed of 16 superconducting cavities, eight per ring. Each ring has two cryomodules, each containing four cavities. Each cavity is powered by a 300 kW klystron. The klystrons are grouped in fours, the klystrons in each group sharing a common 58 kV power converter and HV equipment bunker. The ACS RF control system is based on modern industrial programmable controllers (PLCs). A new fast interlock and alarm system with inbuilt diagnostics has been developed. Extensive use of the FIPIO Fieldbus drastically decreases the cabling complexity and brings improved signal quality, increased reliability and easier maintenance. Features of the implementation, such as system layout, communication and the high level software interface are described. Operational facilities such as the automatic switch on procedure are described, as well as the necessary specialist tools and interfaces. A complete RF chain,including high voltage, cryomodule and klystron is presently being assembled in order to check, as far as possible, all aspects of RF system operation before LHC installation. The experience gained so far in this test chain with the new control system is presented
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| MOPLT005 | An Improved Collimation System for the LHC | acceleration, lepton, undulator, cathode | 536 | ||
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The LHC design parameters extend the maximum stored beam energy 2-3 orders of magnitude beyond present experience. The handling of the high-intensity LHC beams in a super-conducting environment requires a high-robustness collimation system with unprecedented cleaning efficiency. For gap closures down to 2mm no beam instabilities may be induced from the collimator impedance. A difficult trade-off between collimator robustness, cleaning efficiency and collimator impedance is encountered. The conflicting LHC requirements are resolved with a phased approach, relying on low Z collimators for maximum robustness and hybrid metallic collimators for maximum performance. Efficiency is further enhanced with an additional cleaning close to the insertion triplets. The machine layouts have been adapted to the new requirements. The LHC collimation hardware is presently under design and has entered into the prototyping and early testing phase. Plans for collimator tests with beam are presented.
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| MOPLT006 | The New Layout of the LHC Cleaning Insertions | acceleration, lepton, undulator, cathode | 539 | ||
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The improved LHC collimation system required significant changes in the layout and design of the warm insertion IR7. Requirements for collimation, optics, impedance, vacuum, and additional infrastructure are described and the adopted layout is discussed. Various design principles have been explored during the re-design, ranging from a regular 90 degree lattice and special low impedance lattices to an option with additional warm quadrupole units that could have extended the usable space for collimator installations in the insertion. The various constraints for the optics and cleaning design in the LHC cleaning insertions are summarized. Magnet positions and collimators were moved significantly, such that a good cleaning efficiency was maintained while impedance was reduced by a factor of two. Metallic phase 2 collimators allow a better efficiency than originally achievable and additional scrapers were allocated. The required infrastructure was specified, including a powerful cooling system for the collimators.
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| MOPLT007 | Base Line Design for a Beta-beam Neutrino Facility | lepton, acceleration, undulator, cathode | 542 | ||
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The term beta-beam has been coined for the production of pure beams of electron neutrinos or their antiparticles through the decay of radioactive ions circulating in a storage ring. The neutrino source itself consists of a high energy storage ring (gamma ~150), with long straight sections in line with the experiment(s). The radioactive ions (6He and 18Ne) will be produced in an ISOL type target system. Due to the short life times of around 1s at rest, the beam needs to be accelerated as quickly as possible. For this a staged system of accelerators is proposed. The chain starts with a linac followed by a rapid cycling synchrotron for acceleration up to ~300 MeV/u. For further acceleration the existing PS and SPS machines are used. Finally, after acceleration to SPS top energy, the ions are transferred to the decay ring where they are merged with the already circulating bunch through a longitudinal stacking procedure. The base line design of the beta beam facility will be presented and the major design problems encountered as well possible solutions will be discussed.
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| MOPLT008 | The Mechanical Design for the LHC Collimators | lepton, acceleration, undulator, cathode | 545 | ||
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The design of the LHC collimators must comply with the very demanding specifications entailed by the highly energetic beam handled in the LHC: these requirements impose a temperature on the collimating jaws not exceeding 50°C in steady operations and an unparalleled overall geometrical stability of 25micro-m on a 1200 mm span. At the same time, the design phase must meet the challenging deadlines required by the general time schedule. To respond to these tough and sometimes conflicting constraints, the chosen design appeals to a mixture of traditional and innovative technologies, largely drawing from LEP collimator experience. The specifications impose a low-Z material for the collimator jaws, directing the design towards graphite or such novel materials as 3-d Carbon/Carbon composites. An accurate mechanical design has allowed to considerably reduce mechanical play and optimize geometrical stability. Finally, all mechanical studies were supported by in-depth thermo-mechanical analysis concerning temperature distribution, mechanical strength and cooling efficiency.
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| MOPLT009 | The Design of the New Fast Extraction Channel for LHC | extraction, lepton, acceleration, undulator | 548 | ||
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The Large Hadron Collider (LHC) project requires the modification of the existing extraction channel in the long straight section 6 of the CERN Super Proton Synchrotron (SPS). The new extraction will be used to transfer protons at 450 Gev/c as well as ions via the 2.8 km long transfer line TI 2 to the clockwise ring of the LHC. As the resonant extraction to the present SPS west area will be stopped after 2004, the electrostatic septa will be replaced by new fast extraction kicker magnets. The girder for the existing DC septa will be modified to accommodate a new septum protection element. Other modifications concern the replacement of a machine quadrupole, a new scheme for the extraction bumpers, new instrumentation and interlocks. The requirements and the design of the new extraction channel will be described as well as the modifications which will mainly be carried out in the long SPS shutdown 2005.
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| MOPLT010 | Collimation of Heavy Ion Beams in LHC | extraction, lepton, collimation, acceleration | 551 | ||
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The LHC collimation system is designed to cope with requirements of proton beams having 100 times higher beam power than the nominal LHC heavy ion beam. In spite of this, specific problems occur for ion collimation, due to different particle-collimator interaction mechanism for ions and protons. Ions are subject to hadronic fragmentation and electromagnetic dissociation, resulting in a non-negligible flux of secondary particles of small angle divergence and Z/A ratios slightly different from the primary beam. These particles are difficult to intercept by the collimation system and can produce significant heat-load in the superconducting magnets when they hit the magnet vacuum chamber. A computer program has been developed to obtain quantitative estimates of the magnitude and location of the particle losses. Hadronic fragmentation and electromagnetic dissociation of ions in the collimators were considered within the frameworks of abrasion-ablation and RELDIS models, respectively. Trajectories of the secondary particles in the ring magnet lattice and the distribution of intercept points of these trajectories with the vacuum chamber are computed. Results are given for the present collimation system design and potential improvements are discussed.
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| MOPLT012 | Collimation in the Transfer Lines to the LHC | extraction, lepton, acceleration, undulator | 554 | ||
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The intensities foreseen for injection into the LHC are over an order of magnitude above the expected damage levels. The TI 2 and TI 8 transfer lines between the SPS and LHC are each about 2.5 km long and comprise many magnet families. Despite planned power supply surveillance and interlocks, failure modes exist which could result in uncontrolled beam loss and serious transfer line or LHC equipment damage. We describe the collimation system in the transfer lines that has been designed to provide passive protection against damage at injection. Results of simulations to develop a conceptual design are presented. The optical and physical installation constraints are described, and the resulting element locations and expected system performance presented, in terms of the phase space coverage, local element temperature rises and the characteristics of the beam transmitted into the LHC.
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| MOPLT013 | Fatigue Testing of Materials by UV Pulsed Laser Irradiation | extraction, lepton, acceleration, undulator | 557 | ||
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The energy dissipated by the RF currents in the cavities of high-power pulsed linacs induces cycles of the surface temperature. In the case of the CLIC main linac the expected amplitude of the thermal cycles is about hundred degrees, for a total number of pulses reaching 10e11. The differential thermal expansion due to the temperature gradient in the material creates a cyclic stress that can result in surface break-up by fatigue. The materials for cavity fabrication must therefore be selected in order to withstand such constraints whilst maintaining an acceptable surface state. The fatigue behaviour of Cu and CuZr alloy has been tested by inducing larger surface peak temperatures, thus reducing the number of cycles to failure, irradiating the surface with 50 ns pulses of UV light (308 nm) from an excimer laser. Surface break-up is observed after different number of laser shots as a function of the peak temperature. CuZr appears to withstand a much larger number of cycles than Cu, for equal peak temperature. The characterization of the surface states and possible means of extrapolating the measured behaviour to the expected number of pulses of CLIC are discussed in detail.
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| MOPLT014 | Testing of the LHC Magnets in Cryogenic Conditions: Current Experience and Near Future Outlook | extraction, lepton, acceleration, undulator | 560 | ||
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For the Large Hadron Collider under construction at CERN, a necessary and primordial condition prior to its installation is that all the main twin-aperture Dipole and Quadrupole magnets are tested in the 1.9K cryogenic conditions. These tests are not feasible at the manufacturers and hence, are carried out at CERN at a purpose built facility on the site. This presentation will give an overall view of the issues related to the operation of the tests facility. In particular, it will give the goals that need to be met to ensure the magnet integrity and performance and the context & constraints on the test programme. Results accumulated from the tested magnets and the ensuing tests stream-lining will be presented, together with some of the explanations and hard limits. Finally, some improvements planned for efficient operation will be given within the confines of the testing programme as was foreseen and the project goals and deadlines.
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| MOPLT015 | Reliability Issues of the LHC Beam Dumping System | lepton, acceleration, undulator, cathode | 563 | ||
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The Beam Dumping System of the Large Hadron Collider, presently under construction at CERN, must function with utmost reliability to protect the personnel, minimize the risk of severe damage to the machine and avoid undue impact to the environment. The dumping action must be synchronized with the particle free gap and the field of the extraction and dilution elements must be well adjusted to the beam energy. The measures taken to arrive at a reliable and safe system will be described, like the adoption of fault tolerant design principles and other safety related features as comprehensive monitoring, diagnostics and protection facilities. These issues will be discussed in the general framework of the IEC standard recommendations for safety critical systems. Some examples related to the most critical functions will be included.
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| MOPLT016 | Upgrade and Tests of the SPS Fast Extraction Kicker System for LHC and CNGS | extraction, lepton, acceleration, undulator | 566 | ||
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A fast extraction kicker system has been installed in the SPS and successfully used in extraction tests in 2003. It will serve to send beam to the anticlockwise LHC ring and the CNGS neutrino facility. The magnets and pulse generators have been recuperated from an earlier installation and upgraded to fit the present application. Hardware improvements include diode stacks as replacement of the previous dump thyratron switches, a cooling system of the magnets, sensors for its ferrite temperatures and magnetic field quality assessment. In preparation of the future use for 450 GeV/c transfer to LHC and double batch extraction at 400 GeV/c for CNGS the tests comprised extractions of single bunches, twelve bunches in a single extraction and single bunches in a double extraction. The simulated and measured kick characteristics of the upgraded system are presented, along with results from uniformity calculations of the magnetic field after the modifications to accommodate the cooling circuitry. Further improvements will be discussed which are intended to make the system comply with the specifications for CNGS.
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| MOPLT017 | Beam Commissioning of the SPS LSS4 Extraction and the TT40 Transfer Line | lepton, acceleration, undulator, cathode | 569 | ||
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The new fast extraction system in LSS4 of the SPS and the transfer line TT40 were installed between 2000 and 2003, and commissioned with beam in late 2003. The extraction system and transfer line will serve both the anti-clockwise ring of the Large Hadron Collider (LHC), and the long baseline neutrino (CNGS) facility. The layout and functionality of the main elements are briefly explained, including the various hardware subsystems and the controls system. The safety procedures, test objectives and results of the system commissioning with beam are described, together with the test methodology. Conclusions are drawn concerning the performance of the system elements, agreement between predicted and expected activation levels and test efficiency and procedures. The test results are also briefly discussed in the context of future LHC beam commissioning activities.
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| MOPLT018 | Aperture and Delivery Precision of the LHC Injection System | injection, lepton, acceleration, undulator | 572 | ||
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The main LHC injection elements in interaction regions 2 and 8 comprise the injection septa (MSI), the injection kicker (MKI), together with three families of passive protection devices (TDI, TCDD and TCLI). The apertures of the injection septa for the injected and two circulating beams are detailed with a new enlarged vacuum chamber and final septum alignment. The circulating beam aperture of the TDI is detailed with a new TDI support design and modified vacuum tank alignment. A modified TCDD shape is also presented and the implications for the aperture and protection level discussed. The various errors in the SPS, the transfer lines and the injection system, which contribute to injection errors, are analysed, and the expected performance of the system is derived, in terms of the expected delivery precision of the injected beam.
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| MOPLT019 | Experience Gained in the SPS for the Future LHC Abort Gap Cleaning | lepton, acceleration, undulator, cathode | 575 | ||
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Abort gap cleaning using a transverse damper (feedback) has been previously shown in the RHIC accelerator. We report on experimental results in the SPS, where the transverse damper was used to excite transverse oscillations on part of an LHC test beam, and by the induced losses, creating a practically particle free zone. It is proposed to use the same principle for abort gap cleaning in the LHC. For the LHC abort gap cleaning may be required at injection energy, during the ramp and at top energy. It is shown how the transverse excitation can be optimized taking into account the actual bandwidth of the damper systems and the possibility to fully modulate their input signal to match the beam batatron tune distribution. The cleaning efficiency and speed is estimated considering the porcesses involved, the cleaning (with damper) and the filling of the abort gap.
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| MOPLT020 | Limits to the Performance of the LHC with Ion Beams | lepton, acceleration, undulator, cathode | 578 | ||
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The performance of the LHC as a heavy-ion collider will be limited by a diverse range of phenomena that are often qualitatively different from those limiting the performance with protons. We summarise the latest understanding and results concerning the consequences of nuclear electromagnetic processes in lead ion collisions, the interactions of ions with the residual gas and the effects of lost ions on the beam environment and vacuum. Besides these limitations on beam intensity, lifetime and luminosity, performance will be governed by the evolution of the beam emittances under the influences of synchrotron radiation damping, intra-beam scattering, RF noise and multiple scattering on residual gas. These effects constrain beam parameters in the LHC ring throughout the operational cycle with lead ions.
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| MOPLT021 | Attenuation and Emittance Growth of 450 GeV and 7 TeV Proton Beams in Low-Z Absorber Elements | lepton, acceleration, injection, undulator | 581 | ||
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The intensity of the LHC beams will be several orders of magnitude above the damage thresholds for equipment, at 7 TeV, but also already at injection energy of 450 GeV. Passive protection of the equipment against failures during beam transfer, injection and dumping of the beam with absorbers and collimators is foreseen to ensure safe operation. Since these protection devices must be robust in case of beam impact, low-Z materials such as graphite are favored. The reduction of the energy density of the primary beam by the absorber is determined by the attenuation of the beam due to nuclear collisions and the emittance growth of the surviving protons due to scattering processes. Absorbers with low density materials tend to be several meters long to ensure sufficient reduction of the transverse energy density of the impacting beam. The physics principles leading to attenuation and emittance growth for a hadron beam traversing matter are summarised, and FLUKA simulation results for 450 GeV and 7TeV proton beams on low-Z absorbers are compared with theoretical predictions. Design criteria for the LHC absorbers can be derived from these results. As an example, for the transfer line from SPS to LHC a short, low-Z absorber has been proposed to protect the LHC injection elements.
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| MOPLT022 | The Expected Performance of the LHC Injection Protection System | lepton, acceleration, injection, undulator | 584 | ||
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The passive protection devices TDI, TCDD and TCLI are required to prevent damage to the LHC in case of serious injection failures, in particular of the MKI injection kicker. A detailed particle tracking, taking realistic mechanical, positioning, injection, closed orbit and local optical errors into account, has been used to determine the required settings of the absorber elements to guarantee protection against different MKI failure modes. The expected protection level of the combination of TDI with TCLI, with the new TCLI layout, is presented. Conclusions are drawn concerning the expected damage risk level.
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| MOPLT023 | Electron Model of an FFAG Muon Accelerator | lepton, injection, undulator, cathode | 587 | ||
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Parameters are derived for the lattice and RF system of electron models of a non-scaling FFAG ring for accelerating muons. The models accelerate electrons from about 10 to about 20 MeV, and have circumferences between 10 and 17 m. Magnet types and dimensions, spacings, half apertures, about 12~mm by 20~mm,and number of cells are presented. The magnetic components are compared to existing magnets. The tune variation with momentum covers several integers, similar to that in a full machine, and allows the study of resonance crossing. The consequences of misaligned magnets are studied by simulation. The lattices are designed such that transition is at about 15 MeV. The variation of orbit length with momentum is less than 36~mm, and allows the study of acceleration outside a bucket. A 100~mm straight section, in each of the cells, is adequately long for an RF cavity operating at 3 GHz. Hamiltonian dynamics in longitudinal phase space close to transition is used to calculate the accelerating voltage needed. Acceleration is studied by simulation. Practical RF system design issues, e.g. RF power, and beam loading are estimated.
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| MOPLT024 | Flexibility, Tolerances, and Beam-Based Tuning of the CLIC Damping Ring | lepton, injection, undulator, cathode | 590 | ||
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The present design of the CLIC damping ring can easily accommodate anticipated CLIC parameter changes. Realistic misalignments of magnets and monitors increase the equilibrium emittance. In simulations we study both the sensitivity to magnet displacements and the emittance recovery achieved by orbit correction, dispersion-free steering and coupling compensation.
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| MOPLT025 | Status and Plans for the SPS to LHC Beam Transfer Lines TI 2 and TI 8 | lepton, injection, undulator, cathode | 593 | ||
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Beam transfer from the CERN Super Proton Synchrotron (SPS) to the Large Hadron Collider (LHC) will be done through the two transfer lines TI 2 and TI 8, presently under construction, with a combined length of about 5.6 km. The final layout, optics design and correction scheme for these lines will be presented. The requirement of simultaneously matching their geometry and optics with that of the LHC will be treated, including the methodology for alignment of the elements along the line and a proposed solution in the final matching section. After the commissioning of the short transfer line TT40 just upstream of TI 8 in 2003, beam tests of the whole of TI 8 are scheduled for autumn 2004, with the aim to validate many of the new features and mechanisms involved in the future control and operation of these lines. The status of the installation will be described, comprising the progress with infrastructure, services and line elements. An outlook will be given for the work remaining until 2007.
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| MOPLT026 | Equipment Manufacturing and Test Data Tracking for the LHC | lepton, injection, undulator, cathode | 596 | ||
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The MTF system was developed at CERN to capture the design, manufacturing and test data of equipment built for LHC. Today, more than 80.000 descriptions of LHC equipment are managed using the MTF. The system handles both production data and non-conformance issues. The acquisition of the equipment data is both an organisational and a technical challenge. On the organisational side many different aspects of production and management have to be taken into account. The LHC equipment suppliers, wherever their production facilities are located, whatever their computer skills or rates of production are, need a user friendly environment to provide the data with a very limited effort on the shop floor. For expensive equipment such as the LHC dipoles a reliable and robust non-conformance methodology must be put in place, the MTF provides the required information technology support tools. The EDMS Service has developed methods, training processes and tools to cope with an extensive use of the system, a use that will grow during the next years until the LHC is installed. This paper presents the experience acquired and the solutions put in place.
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| MOPLT027 | Cold Beam Vacuum Interconnects for the LHC Insertion Regions | lepton, injection, undulator, cathode | 599 | ||
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The LHC machine is composed of arcs and insertion regions where superconducting magnets, working at temperatures of 1.9 K and 4.5 K, have flexibly interconnected beam vacuum chambers. These interconnects must respect strict requirements in terms of impedance, aperture, space optimization and reliability. A complete interconnect design was first developed for the arc regions, and from which a total of 20 variants have been created according to the different functional requirements of each pair of cryostats along the machine. All design features and manufacture processes were validated through extensive testing. Manufacture and assembly cost was minimised by using a modular interconnect design, with common components shared among different design variants. A detailed quality assurance structure was implemented in order to achieve the high level of reliability required. This paper presents the layout of cold beam vacuum interconnects along with details of development and testing performed to validate design and integration.
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| MOPLT028 | In-Situ Vibration Measurements of the CTF2 Quadrupoles | lepton, injection, undulator, cathode | 602 | ||
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The Compact LInear Collider (CLIC), presently under study at the European Organization for Nuclear Research (CERN), aims at colliding high-energy ‘‘nanobeams'' at a luminosity of 1035 cm-2s-1. Vibrations of the lattice elements, if not properly corrected, can result in a loss in performance by creating both unacceptable emittance growth in the linear accelerator and relative beam-beam offsets at the interaction point. Of particular concern are the vibrations induced by the accelerator environment. For example, the circulating water used to cool the lattice quadrupoles will increase magnet vibration levels. In the framework of the CLIC stability study, in-situ measurements of quadrupole vibrations have been performed at the CLIC Test Facility 2 (CTF2) with all accelerator equipment switched on. Since the CTF2 quadrupoles and their alignment support structures are realistic prototypes of those to be used in the CLIC linac, the measurements provide a realistic estimate of the CLIC magnet vibrations in a realistic accelerator working environment.
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| MOPLT029 | All Digital IQ Servo-system for CERN Linacs | lepton, injection, undulator, cathode | 605 | ||
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A VME based control system has been developed and built at CERN for the servo loops regulating the field in linac accelerating structures. It is an all-digital system built on a single VME card, providing digital detection, processing, and modulation. It is foreseen to be used, in different versions, for the needs of both present and future CERN hadron linacs. The first application will be in the energy ramping RF chain of the CERN Heavy Ion Linac (linac 3). In addition to regulating the cavity field, the system incorporates the measurement and control of the cavity resonance as well as an imbedded loop stabilizing the gain and the phase of the final amplifier operating near saturation. The design principle and the experimental results are described.
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| MOPLT030 | Performance Limits and IR Design of a Possible LHC Luminosity Upgrade Based on Nb-Ti SC Magnet Technology | lepton, injection, undulator, cathode | 608 | ||
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We investigate the maximum LHC performance for a possible IR design based on classical Nb-Ti insertion magnets. We then extend our analysis to a ternary Nb-based ductile alloy such as Nb-Ti-Ta, a less developed but relatively cheap super-conducting material which would allow us to gain about 1 T of peak field on the coils, and discuss the corresponding luminosity reach for a possible LHC upgrade compared to that based on Nb3Sn magnet technology.
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| MOPLT031 | LHC Abort Gap Filling by Proton Beam | lepton, injection, undulator, cathode | 611 | ||
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Safe operation of the LHC beam dump relies on the possibility of firing the abort kicker at any moment during beam operation. One of the necessary conditions for this is that the number of particles in the abort gap should be below some critical level defined by quench limits. Various scenarios can lead to particles filling the abort gap. The relevant time scales associated with these scenarios are estimated for top energy where the synchrotron radiation losses are not negligible for uncaptured particle motion. Two cases are considered, both with RF on and RF off. The equilibrium distribution of lost particles in the abort gap defines the requirements for maximum tolerable relative loss rate and as a consequence the minimum acceptable longitudinal lifetime of the proton beam in collision.
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| MOPLT032 | Breakdown Resistance of Refractory Metals Compared to Copper | lepton, injection, undulator, linac | 614 | ||
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The behaviour of Mo, W and Cu with respect to electrical breakdown in ultra high vacuum has been investigated by means of a capacitor discharge method. The maximum stable electric field and the field enhancement factor, beta, have been measured between electrodes of the same material in a sphere/plane geometry for anode and cathode, respectively. The maximum stable field increases as a function of the number of breakdown events for W and Mo. In contrast, no systematic increase is observed for Cu. The highest values obtained are typically 500 MV/m for W, 350 MV/m for Mo and only 180 MV/m for Cu. This conditioning, found for the refractory metals, corresponds to a simultaneous decrease of beta and is therefore related to the field emission properties of the surface and their modification upon sparking. Accordingly, high beta values and no applicable field increase occur for Cu even after repeated breakdown. The results are in agreement with rf breakdown experiments [*] performed on prototype 30 GHz accelerating structures for the CLIC accelerator.
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* W. Wuensch, C. Achard, S. Döbert, H. H. Braun, I. Syratchev, M. Taborelli, I. Wilson, "A Demonstration of High Gradient Acceleration", CERN-AB-2003-048-RF; CLIC-Note-569, Proc. PAC2003. |
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| MOPLT033 | Experimental Studies of Controlled Longitudinal Emittance Blow-up in the SPS as LHC Injector and LHC Test-Bed | lepton, injection, undulator, linac | 617 | ||
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The longitudinal emittance of the LHC beam must be increased in a controlled way both in the SPS and the LHC itself. In the first case a small increase is sufficient to help prevent coupled bunch instabilities but in the second a factor three is required to also reduce intra-beam scattering effects. This has been achieved in the SPS by exciting the beam at the synchrotron frequency through the phase loop of the main RF system using bandwidth-limited noise, a method that is particularly suitable for the LHC which will have only one RF system. We describe the tests that have been done in the SPS both for low and high intensity beams, the hardware used and the influence of parameters such as time of excitation, bandwidth, frequency and amplitude on the resulting blow-up. After taking into account intensity effects it was possible to achieve a controlled emittance increase by a factor of about 2.5 without particle loss or the creation of visible tails in the distribution.
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| MOPLT034 | Possible Causes and Consequences of Serious Failures of the LHC Machine Protection System | lepton, injection, undulator, linac | 620 | ||
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The LHC machine protection systems, including the beam dumping system, are designed to ensure that failures leading to serious damage to the LHC during its lifetime are extremely unlikely. These kind of failures have to date been considered as being ?beyond the design case?, for instance requiring a combination of equipment failure and surveillance failure. However, they need to be evaluated to determine the required safety levels of the protection systems. A second objective is to understand if measures can and should be taken to further reduce the probability of such failures, or to minimise their impact. This paper considers various serious failure modes of the different machine protection systems. The probable consequences and possible ameliorating measures of the worst-case scenarios are discussed. The particular case of having a stored beam with an unavailable beam dumping system is mentioned, together with possible actions to be taken in such an event.
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| MOPLT035 | Beam Induced Heating of the SPS Fast Pulsed Magnets | lepton, undulator, linac, dumping | 623 | ||
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Fast pulsed magnets with ferrite yokes are used in CERN?s SPS accelerator for beam injection, extraction and excitation for tune measurements. The impedance of the ferrite structures can provoke significant beam induced heating, especially for beams with high peak currents as for LHC operation, even beyond the Curie temperature. The expected heating in the different kicker systems for various operational modes is compared with beam measurements. Estimates of the beam induced power have been derived from measured beam spectra. A fast extraction kicker system has recently been equipped with a cooling system. The measured cooling performance is compared with data from laboratory setups and numerical simulations.
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| MOPLT037 | Simulation of Transient Beam-feedback Interaction with Application to the Extraction of the CNGS Beam from the SPS | lepton, feedback, undulator, linac | 626 | ||
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For actual and future high energy proton accelerators, such as the LHC, transverse feedback systems play an essential role in supplying the physics experiments with high intensity beams at low emittances. We developed a simulation model to study the interaction between beam and transverse feedback system in detail, bunch-by-bunch and turn-by-turn, considering the real technical implementation of the latter. A numerical model is used as the nonlinear behavior (saturation) and limited bandwidth of the feedback system, as well as the transient nature at injection and extraction, complicates the analysis. The model is applied to the practical case of the CNGS beam in the SPS accelerator. This beam will be ejected from the SPS in two batches causing residual oscillations by kicker ripples on the second batch. This second batch continues to circulate for some 1000 turns after the first batch has been extracted and oscillations are planned to be damped by the feedback system. It is shown how the model can be extended to the case of transients at injection (LHC), and to include coupled bunch instability effects.
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| MOPLT038 | Conceptual Design of the LHC Beam Dumping Protection Elements TCDS and TCDQ | lepton, feedback, extraction, undulator | 629 | ||
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The Beam Dumping System for the Large Hadron Collider, presently under construction at CERN, consists, per ring, of a set of horizontally deflecting extraction kicker magnets, vertically deflecting steel septa, dilution kickers and finally, a couple of hundred metres further downstream, an absorber block. A fixed diluter (TCDS) will protect the septa in the event of a beam dump that is not synchronised with the particle free gap or a spontaneous firing of the extraction kickers which will cause the beam to sweep over the septum. A mobile diluter block (TCDQ) will protect the superconducting quadrupole immediate downstream of the extraction as well as the arc at injection energy and the triplet aperture at top energy from bunches with small impact parameters. The conceptual design of the protection elements will be described, together with the status of the mechanical engineering.
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| MOPLT039 | QCD Explorer Based on LHC and CLIC-1 | lepton, feedback, extraction, undulator | 632 | ||
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Colliding 7-TeV LHC super-bunches with 75-GeV CLIC bunch trains can provide electron-proton collisions at very high centre-of-mass energies, opening up a new window into QCD. At the same time, this QCD explorer would employ several key components required for both an LHC upgrade and CLIC. We here present a possible parameter set of such a machine, study the consequences of the collision for both beams, and estimate the attainable luminosity.
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| MOPLT040 | Test Results of Superconducting Cavities Produced and Prepared Completely in Industry | lepton, feedback, extraction, undulator | 635 | ||
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Superconducting cavities for a variety of recent projects are produced and prepared for operation in industry. We report on test results of those cavities produced and prepared at ACCEL. The preparation of the cavities includes chemical treatment (BCP), rinsing with high pressure water and assembly in a clean room. The following cavity types were treated: 400 MHz single cell cavities for LHC, 500 MHz single cell cavities of the Cornell CESR design for our superconducting accelerating modules, 1300 MHz TESLA type cavities, 176 MHz and 160 MHz halfwave resonators and a 352 MHz CH-mode cavity for ion accelaration.
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| MOPLT041 | Production of Superconducting Accelerator Modules for High Current Electron Storage Rings | lepton, feedback, extraction, undulator | 638 | ||
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For Diamond Light Source, ACCEL was awarded to produce three more superconducting 500 MHz accelerator modules of the Cornell CESR design. With the already 6 modules produced for Cornell, NSRRC and CLS, this module can now be considered as a kind of standard product. In this paper we describe the basic parameters and guaranteed values of this module and will also report on the performance of delivered modules.
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| MOPLT042 | Interaction of the CERN Large Hadron Collider (LHC) Beam with Solid Metallic Targets | lepton, target, feedback, extraction | 641 | ||
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The LHC will operate at 7 TeV with a luminosity of 1034 cm-2s-1. This requires two beams, each with 2808 bunches. The nominal intensity per bunch is 1.1 1011 protons. The energy stored in each beam of 350 MJ could heat and melt 500 kg of copper. Protection of machine equipment in the presence of such powerful beams is essential. In this paper the mechanisms causing equipment damage in case of a failure of the machine protection system are discussed. An energetic heavy ion beam induces strong radial hydrodynamic motion in the target that drastically reduces the density in the beam heated region [*], leading to a much longer range for particles in the material. For the interaction of the LHC proton beams with a target a similar effect is expected. We carried out two-dimensional hydrodynamic simulations of the heating of a solid copper block with a face area of 2cm x 2cm irradiated by the LHC beam with nominal parameters. We estimate that after an impact of about 100 bunches the beam heated region has expanded drastically. The density in the inner 0.5 mm decreases by about a factor of 10. The temperature in this region is about 10 eV and the pressure about 15 GPa. The material in the heated region is in plasma state while the rest of the target is in a liquid state. The bulk of the following beam will not be absorbed and continue to tunnel further and further into the target. The results allow estimating the length of a sacrificial absorber, if such device should be installed for an LHC upgrade. A very interesting "spinoff" from this work would be the study of high-energy-density states of matter induced by the LHC beam, because a specific energy deposition of 200 kJ/g is achieved after 2.5 micros.
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* N.Tahir et al., Phys. Rev. E, 63, 2001 |
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| MOPLT044 | Longitudinal Positron Polarisation in HERA-II | lepton, target, feedback, extraction | 644 | ||
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Following the installation of two more pairs of spin rotators in the course of the HERA Luminosity Upgrade, longitudinal positron spin polarisation has now been generated simultaneously at all three positron(electron) interaction points in HERA at the routine energy of 27.5 GeV. The maximum attained so far is 54 percent. The theoretical maximum for this configuration and in the presence of realistic errors is 57.0 percent. This is the first time in the history of high energy electron storage ring physics that the naturally occurring vertical polarisation has been, with the aid of spin rotators, converted to longitudinal polarisation at three interaction points simultaneously. We describe the measures needed to attain polarisation in light of the HERA Upgrade and the resulting recent performance.
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| MOPLT045 | Vacuum Induced Backgrounds in the New HERA Interaction Regions | background, target, feedback, extraction | 647 | ||
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After the rebuild of the HERA interaction regions the experimental detectors were limited by beam induced backgrounds. Four types of background mechanisms were observed and identified - proton gas scattering, lepton gas scattering, synchrotron radiation and proton beam-halo losses. With some refined beam steering methods it was possible to tune the synchrotron radiation background to acceptable limits. The remaining most important effect was the scattering of the beam particles, mostly the protons, at the residual gas. In this contribution we describe our systematic attempts to investigate the complex behavior of the beam gas background and the measures taken to improve the situation. This includes dynamic pressure profile simulations and measurements, experimental determination of the background sensitivity profile along the beamline, the pressure development with current and time, and residual gas analysis. The background conditions were finally improved due to long term conditioning with beam, modifications of internal masks which were heated by higher order mode losses and moderate improvements of the pumping speed at strategic locations.
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| MOPLT046 | Overcoming Performance Limitations due to Synchrobetatron Resonances in the HERA Electron Ring | background, target, extraction, undulator | 650 | ||
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The HERA Electron Ring was suffering from strong synchrobetatron resonances which have been particularly detrimental after the HERA luminosity upgrade because of a reduced sychrotron tune due to stronger transverse focusing and a shift in the damping distribution in favor of transverse damping. It turned out to be most difficult to store a beam at the preferred working point for high electron spin polarization between the 2nd and the 3rd synchro-betatron satellite of the horizontal integer resonance. A comparative study of the resonance strength did not reveal any significant additional disadvantage of the new beam optics. However, a mechanism driven by closed orbit distortions was discovered which can increase the width of the resonance Qx+2Qs=0 by a large factor. This explains the operational difficulties. The remedy against this effect is quite straight forward. The Fourier component of the closed orbit near the horizontal tune must be avoided. This is enforced in HERA operations by rigerous orbit corrections and an orbit feedback system which reproduces well-corrected orbits reliably. Synchrobetatron resonances do not constitute a performance limitation of polarized lepton proton collisions in HERA any more.
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| MOPLT047 | Lattice Design Study for HESR | background, extraction, undulator, scattering | 653 | ||
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The important feature of High Energy Storage Ring is the combination of phase space cooled beams with internal targets, which allows to reach high luminosities up to 2*1032cm-2s-1. However, the requirement to have the strongly focused beam on the target causes the high chromaticity value on the target straight section and as in result to the squeezing of dynamic aperture after sextupole correction of the chromaticity. Simultaneously, the momentum-compaction factor is one of the most important characteristics of an accelerator, which defines the collective instability threshold. Therefore, the HESR lattice has to have the following features: low or negative momentum compaction factor, dispersion free straight sections, convenient method to correct the chromaticity by the sextupoles, sufficiently large dynamic aperture. In this work we develop lattice, which meets all these requirements for HESR.
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| MOPLT048 | High Current Switch-mode Power Converter Prototype for LHC Project 6kA, 8V | background, extraction, undulator, scattering | 656 | ||
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For the Large Hadron Collider (LHC) accelerator being constructed on the CERN site, very precise variable DC currents are required. The company JEMA had during year 2002, designed, manufactured and tested a power converter prototype according to CERN specifications, particularly demanding in terms of dc stability and dynamic response. The power converter is formed by four sub-converters 8V, 2kA in parallel. Isolation between mains input and magnet load is at high frequency done, 40 kHz, which means a volume reduction and better mains perturbations rejection. IGBT inverter soft switch-mode power conversion in ZVS operation reduces dramatically commutation losses, increasing total efficiency of the power converter. The sub-converter, regulated by a wide band width current loop in ACC mode, follows the current reference calculated by the overall voltage loop, providing a good sharing of the output currents and high output stability. The design of the water cooled power converter, results in a very reduce volume and modular structure, providing the system a very flexible exchangeability. The power converter was tested and accepted by CERN into year 2003, some minor points were left to be adjusted during the pre-series stage.
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| MOPLT049 | A Very High-beta Optics to be used for an Absolute Luminosity Determination with Forward Detectors in ATLAS | background, extraction, undulator, resonance | 659 | ||
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Atlas detector at the LHC pursues a number of different approaches to obtain an estimate of the absolute luminosity. Measuring elastic scattering at very small angles (3 mu rad) represents a different and complimentary approach that will improve the precision of the final luminosity estimate. In this paper we show the required very hihg-beta optics, detector acceptance studies, and running conditions and calculated performance for the proposed forward detectors located near the ATLAS interaction region.
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| MOPLT050 | High-beta and Very High-beta Optics for LHC | background, extraction, undulator, resonance | 662 | ||
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New high-beta and very high-beta optics has been sought in order to find the best possible configuration for measuring total cross section in TOTEM and absolute luminosity in ATLAS. They are based on nominal powering scheme of the low-beta triplet. A list of the various possible solution is given in this report. A particularly interesting solution has been found for a case where the phase advance in both planes at the detector location are close to pi/2.
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| MOPLT051 | Experimental Characterization of PEP-II Luminosity and Beam-beam Performance | background, extraction, undulator, resonance | 665 | ||
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The beam-beam performance of the PEP-II B-Factory has been studied by simultaneously measuring the instantaneous luminosity, the horizontal and vertical e+ and e- beam sizes in the two rings, and the spatial extent of the luminous region as extracted from BaBar dilepton data. These quantities, as well as ring tunes, beam lifetimes and other collider parameters are recorded regularly as a function of the two beam currents, both parasitically during routine physics running and in a few dedicated accelerator physics experiments. They are used to quantify, project, and ultimately improve the PEP-II performance in terms of achieved beam-beam parameters, dynamic-beta enhancement, and current-dependence of the specific luminosity.
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| MOPLT052 | Emittance Growth and Beam Lifetime Limitations due to Beam-beam Effects in e+e- Storage Ring Colliders | background, extraction, undulator, resonance | 668 | ||
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In this paper we give analytical expressions for the maximum beam-beam parameter and related beam-beam limited beam lifetime in e+e- storage ring colliders. After analysing the performances of existing or existed machines, we make some discussions on the parameter choice for the Super-B factory design.
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| MOPLT053 | On Parasitic Crossings and their Limitations to e+e- Storage Ring Colliders | background, extraction, undulator, resonance | 671 | ||
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We treat the problem of parasitic crossing in e+e- storage ring colliders analytically. Analytical formulae for the beam lifetime limited by the combined effects of beam-beam interactions at interaction point and at parasitic crossings are derived, and applied to the by-2 colliding mode of PEP-II low energy ring.
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| MOPLT054 | High Current Operation of Pre-bunching Cavities in the CTF3 Accelerator | background, extraction, undulator, resonance | 674 | ||
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In the framework of the CLIC studies for a 3 TeV centre of mass linear collider the CLIC Test Facility-3 accelerator (CTF3) is developed to validate the novel concept of CLIC drive beam generation. The front end of the CTF3 linac uses a 140 kV thermionic gun capable to deliver a beam with currents of up to 10 A during 1.5 microseconds. Theμtime structure of this beam is generated with two standing wave single-cell 3 GHz pre-buncher cavities. The high current demands special care in the design of the pre-bunchers to preserve beam quality and transmission. A particular concern was beamloading in the second pre-buncher. In this paper, the design and the conditioning of the pre-bunchers are reported but the main focus is on the commissioning with the electron beam, which showed unexpected results. Indeed, contrary to our expectations, the unbunched beam seems to induce a kind of beamloading in the first pre-buncher while the second one shows none.
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| MOPLT055 | RF Excitation of Linear and Curved Sections of the CRFQ Project | background, extraction, undulator, resonance | 677 | ||
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The Circular Radiofrequency Quadrupole is basically a Linear Radio-Frequency Quadrupole completely bent on a circle. A 30-keV prototype is being presently designed and manufactured for testing of the fundamental principles within the scope of a collaboration between BNL and Italian research centers. The storage ring is made of a proton source, a Linear RfQ section 70 cm long, for injection and matching, and eight Curved sections also each about 70 cm long. The proton beam is provided by a modified RF source with electrostatic acceleration at the emittance, intensity and energy required by the beam dynamics.The design of the initial linear prototype is based on a 4-rods geometry having a beam gap diameter of 10mm, and circular 10mm diameters rods. The sector is placed in a 150mm diameter pipe, making it as a very compact structure. The dimensions of the device are adjusted to resonate at 202.56 MHz. A RF power source will be soon available to test the device. The paper describes the compact RF cells arrangement in the design of the two sections.
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| MOPLT056 | Feasibility Study for a Very High Luminosity Phi-factory | background, extraction, undulator, resonance | 680 | ||
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Particle factories are facing their future by looking at the possibility of upgrading the luminosity by orders of magnitude. The upgrade challenges are more stringent at lower energies. Double symmetric rings, enhanced radiation damping, negative momentum compaction and very short bunches at the collision point are the main features of a phi-factory feasibility study presented in this paper. The bunch length of few millimeters at the crossing point of the beams is obtained by applying the Strong RF Focusing principle which provides a modulation of the bunch length along the ring by means of a large momentum compaction factor together with a very high RF gradient. The collider design fits the existing DAFNE infrastructures with completely rebuilt rings and upgraded injection system.
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| MOPLT057 | Proposal of a Strong RF Focusing Experiment at DAFNE | background, extraction, undulator, resonance | 683 | ||
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The strong RF focusing is a recently proposed technique to obtain short bunches at the interaction point in the next generation colliders. A large momentum compaction factor together with a very high RF gradient across the bunch provide a modulation of the bunch length along the ring, which can be minimized at the Interaction Point (IP). No storage ring has been so far operated in such a regime, since it requires uncommonly high synchrotron tune values. In this paper we present the proposal of creating the experimental conditions to study the strong RF focusing in DAFNE. The proposed machine lattice providing the required high momentum compaction value, the upgrade of the RF system including the installation of a multi-cell superconducting cavity, the upgrade of the cryogenic plant and a list of the possible beam experiments are illustrated and discussed.
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| MOPLT058 | Status of CTF3 Stretcher-compressor and Transfer Line | background, extraction, vacuum, undulator | 686 | ||
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The first part of the CTF3 transfer line is under installation. It includes a chicane which, because of its very flexible lattice and large aperture vacuum chamber, can change the bunch length in a wide range. The chicane can be used as a stretcher to lengthen the pulses coming from the linac in order to reduce the coherent synchrotron radiation (CSR) in the recombination rings. A possible use as a bunch compressor is also foreseen in order to make CSR experiments and to characterize beam instrumentation. This paper describes the final design of the vacuum chambers, including beam diagnostics components, and their laboratory tests. The installation status of the magnetic and vacuum chamber components together with the ancillary systems is reported.
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| MOPLT059 | Design Options for the RF Deflector of the CTF3 Delay Loop | background, vacuum, undulator, resonance | 689 | ||
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Injection and extraction of bunch trains in the CTF3 Delay Loop for the recombination between adjacent bunch trains is performed by a specially designed RF deflector. A standing wave structure has been chosen. Three possible solutions have been studied and designed, and a comparative analysis is presented. All of them satisfy the essential requirements of the system up to the maximum foreseen energy with the existing klystron.
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| MOPLT060 | New RF Measuring System for Cavity Characterization | background, vacuum, undulator, resonance | 692 | ||
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New computer based mobile measuring system for laboratory and online characterization of superconducting cavities has been put into operation at LNL. The system covers the frequency range from 80 to 350 MHz and represents a reliable, fast and precise instrument for cavity testing. The list of automatic and semiautomatic procedures includes line calibrations, frequency sweep, decay time measurement, Q(Eacc) curve acquisition and pulse conditioning.
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| MOPLT061 | Design Study for Advanced Acceleration Experiments and Monochromatic X-ray Production @ SPARC | background, vacuum, undulator, resonance | 695 | ||
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We present a design study for an upgrade of the SPARC photo-injector system, whose main aim is the construction of an advanced beam test facility for conducting experiments on high gradient plasma acceleration and for the generation of monochromatic X-ray beams to be used in advanced medical applications and condensed matter physics studies. Main components of the proposed plan of upgrade are: two additional beam lines with interaction regions for synchronized high brightness electron and high intensity photon beams and the upgrade of the SPARC Ti:Sa laser system to reach a multi-TW power level (in excess of 1 J in pulse energy). Results of numerical simulations modeling the interaction of the SPARC electron beam and the counter-propagating laser beam are presented with detailed discussion of the monochromatic X-ray beam spectra generated by Compton backscattering: X-ray energies are tunable in the range 20 to 500 keV, with pulse duration from sub-ps to 30 ps. Preliminary simulations of plasma acceleration of the SPARC electron beam, generated in ultra-short bunches, via the LWF mechanism and with external injection are also shown: experiments of self-injection are also foreseen and illustrated.
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| MOPLT062 | The Design of a Prototype RF Compressor for High Brightness Electron Beams | background, vacuum, undulator, resonance | 698 | ||
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The generation of sub-ps electron bunches with low transverse emittance at nC charge level is a crucial requirement in the design of injectors for short wavelength FEL's. The technique of velocity bunching has been by now experimentally proven in various laboratories, where bunches below the ps bunch length were obtained: however, preservation of a low transverse emittance after the bunch compression is still to be demonstrated. To this aim, the use a slow wave RF structure as a rectilinear compressor has been proposed in the past to overcome the inherent difficulties of magnetic compressors. In this paper we will review the work carried out in the last 2 years and focused on the design a RF compressor based on a 3 GHz slow-wave copper structure. The rationale of the conceptual design along with a description of the main experimental activities will be presented and the future application of such a scheme to the SPARC project will be discussed.
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| MOPLT063 | Reconfigurable Hardware Resources in Accelerator Control Systems | background, vacuum, undulator, resonance | 701 | ||
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The development of modern accelerator control systems has taken advantage of the possibility to use standard architecture designs based on the experience gained in industrial applications. Communication buses, board formats, operating systems, network protocols and operator interface software are the main elements of this new approach. In this paper we will discuss the way to apply this method also to the design of electronic boards which call for custom design of particular circuits and capabilities. The use of FPGA based standard modules along with the possibility to customize them using a standard LabVIEW environment to obtain reconfigurable hardware resources will be presented.
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| MOPLT066 | Induction Accelerating Cavity for a Circular Ring Accelerator | background, vacuum, undulator, resonance | 704 | ||
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This paper reports details of an induction accelerating cavity employed for induction synchrotron POP experiments [*] using the KEK 12GeV PS. This cavity is the first induction cavity in the history of accelerator that is used in a circular ring. We focus our attention on crucial aspects distinguished from well-know properties of RF cavity. The single cavity is capable of generating an acceleration voltage of 2.5kV with a pulse width of 250ns, which is operated at a repetition rate in the range of 667kHz - 882kHz. The cavity is driven by its own pulse modulator through a 25m long transmission cable of 125W, the end of which is connected with a matching resistance so as to minimize reflection in a wide range of frequency. Accelerating field characteristics are discussed and matching features of the cavity as a one-to-one transformer are presented. A longitudinal and transverse coupling impedance have been measured using a net-work analyzer.
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* K.Takayama et al., 'POP Experiments of the Induction Synchrotron' in this conference |
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| MOPLT067 | KEKB Performance | background, vacuum, undulator, resonance | 707 | ||
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The KEKB B-Factory is an electron-positron double ring collider working at KEK. Its peak luminosity surpassed 1034 /cm2/sec in May 2003 for the first time in the history of colliders. In this report, we summarize the history of KEKB with an emphasis of recent progress.
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| MOPLT069 | Investigation of Injection for the Low-emittance Lattice with New-6.25 ohm Kicker Magnet System at the Photon Factory | injection, background, vacuum, undulator | 710 | ||
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We installed 6.25ohm traveling-wave kicker magnet in the Photon Factory to obtain a wide acceptance for the injected beam into the low-emittance lattice of the Photon Factory. We investigate the injection for the low-emittance lattice with this 6.25ohm kicker magnet system. Hence we have optical beam diagnostic systems which source point is inside of injection bump, we use this system for the investigation of injection. The pulse shape of the injection bump was measured by the optical beam profile monitor with high-speed gated camera by using a stored beam. The result of pulse shape of injection bump was agreed with the predicted one by using result of magnetic field measurement, and pulse duration was shorter than twice of revolution time. The instantaneous beam profile of injected beam was observed in turn by turn by using the same beam profile monitor system. We measure the turn by turn position of the injected beam from this observation and compare with a simulation. We also observe a smear out of beam oscillation by nonlinear effect from this instantaneous beam profile measurement.
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| MOPLT070 | FFAG as Phase Rotator for the PRISM Project | injection, background, vacuum, undulator | 713 | ||
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A Fixed Field Alternating Gradient (FFAG) ring will be used as a phase rotator in the PRISM project. We report a design of the PRISM-FFAG in this paper. PRISM stands for "Phase Rotated Intense Slow Muon beam". It is a project to realize a super muon beam, which combines high-intensity, low-energy, narrow energy-spread and high purity. Its aimed intensity is about 1011-1012 muons per sec. The muon beam will be provided with a low kinetic energy of 20MeV to optimize for the stopped muon experiments. FFAG has some advantageous characteristics to achieve such superb beam. These are a large momentum (longitudinal) acceptance, a wide transverse acceptance with strong focusing, and synchrotron oscillation, which is needed to perform phase rotation. According to simulations, initial energy spread of 20MeV±40% is reduced down to ±6% after 5 turns of muons in the FFAG ring. In the FFAG ring almost all pions decay into muon, hence extracted beam has extremely low pion contamination. A program to construct the PRISM-FFAG ring has been started. It would be completed by the end of JFY 2005.
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| MOPLT071 | EPICS Based Control System for the KOMAC RF System | injection, background, vacuum, undulator | 716 | ||
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This paper presents the RF control system for Korea Multi-purpose Accelerator Complex (KOMAC). KAERI (Korea Atomic Energy Research Institute) has been performing the project named KOMAC. As the 3nd phase of the project, 20MeV proton accelerating structure is under development. The new design is based on the use of VME based Multi-function modules connected to the specific low level RF Controllers(LLRF) via distributed I/O modules and Serial communication modules. The control system was based on EPICS (Experimental Physics and Industrial Control System) from the end of 2003. Installation and commissioning of the RF module is scheduled on 2004. Control system to integrated the RF System to the KOMAC control system is implemented. Hardware, software and various applications are developed to support the operation of RF Control system. This paper EPICS based control system for KOMAC RF
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| MOPLT072 | Effects of Positrons on Relativistic Solitons in Laser-Plasma Interactions | injection, background, vacuum, undulator | 719 | ||
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An extended 1D kinetic model of relativistic solitons by high power lasers in three species plasmas is suggested and it is applied to analysis on the effects of electron-positron pairs on the solitons. Stability condition of the solitons is derived. The range of parameters for the stable solitons are specified in the frequency-temperature plane. With the creation of electron-positron pairs, relativistic solitons appear stable in wider range of frequencies and temperatures. The regions are expanded toward higher values in overall ranges in the frequency-temperature plane. The stability conditions are affected by the density of positrons. The variation of shapes, peak E-field, and width of the solitons by varying the positron density are analyzed. We discuss the implications of the variation in the soliton on the ion accelerations by it.
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| MOPLT073 | Picosecond High Voltage Switching for Pulsed DC Acceleration | acceleration, background, laser, vacuum | 722 | ||
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Laser wakefield acceleration promises the production of high energy electrons from table-top accelerators. External injection of a (low energy) electron bunch into a laser wakefield requires acceleration gradients of the order GV/m. In principle DC acceleration can achieve GV/m acceleration gradients. If high voltage pulses of the order MV can be switched with picosecond precision, the performance of such an accelerator would be greatly enhanced and even multistage DC acceleration would become feasible. Presently risetime and jitter of high voltage pulses in high voltage laser triggered spark gaps are limited to the nanosecond regime by the initial stochastic breakdown process in the gap. A way to overcome this limitation is to create a line focus between the electrodes with an intensity above 1018 W/m2 using a high power femtosecond Ti:Sapphire laser. Because of the instantaneous ionization and high degree of ionization in the plasma channel, picosecond switching precision can be achieved and jitter is reduced significantly. A spark gap test setup with 3 mm interelectrode distance has been build and the first measurements have been done. Femtosecond diagnostics for characterization of the laser induced plasma and electro-optic diagnostics for the high voltage pulse have been developed.
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| MOPLT075 | Ideal Waterbag Electron Bunches from an RF Photogun | background, laser, acceleration, vacuum | 725 | ||
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With the implementation of fs mode-locked Ti:Sapphire lasers in high-gradient RF photoguns, a new charged particle acceleration regime has emerged, the so-called pancake regime. Pancake bunches have by definition a restframe length which is much smaller than the bunch radius. This geometry allows a relatively simple, but effective analytical description of the space-charge dominated, critical initial part of the acceleration trajectory. In high-gradient RF photoguns the pancake regime can be relevant up to several MeV. The general opinion is that extremely short bunches should be avoided during the initial stages of the acceleration process, because high space charge densities are always detrimental to the final beam quality. We show that this is not necessarily true: shorter bunches may even lead to better beams.
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| MOPLT078 | The Coupling Compensation and Measurement in the Interaction Region of BEPCII | background, laser, acceleration, vacuum | 728 | ||
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The detector solenoid field in the BEPCII interaction region will be compensated by 6 anti-solenoids, which are located nearby the interaction point. The coupling compensation scheme and the method to tune the x-y coupling at the interaction point will be introduced in detail.
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| MOPLT081 | Low Energy Ion Beam Dynamics in Axisymmetric RF Undulator Linac | background, laser, vacuum, resonance | 731 | ||
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The ion beam focusing and acceleration in an axisymmetric periodic RF undulator structure is considered. There is suggested that RF field has no a synchronous wave and accelerating force is to be driven by a combination of two non-synchronous waves. The influence of non-synchronous harmonics on ion beam dynamics is studied by means of a smooth approximation. Choice and optimization of RF field harmonics are made to obtain maximal transmission coefficient. The result is verified by a numerical simulation. The comparison with a conventional RF linac, where a synchronous harmonic accelerates a beam and non-synchronous one is focusing a beam, is described. This comparison is suitable for demonstration of the capabilities of an undulator linac.
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| MOPLT086 | Upgrading the Control System at KCSR | background, laser, vacuum, resonance | 734 | ||
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Till now Kurchatov Centre of Synchrotron Radiation facility control system is based on a CAMAC-oriented computers network. In this paper the project of upgrading and results of prototyping of the new equipment is submitted. Upgrading includes two levels. First, it is possible to create the modern CAMAC crate-controller, connected with standard network. More advanced variant will consist in replacement of CAMAC modules with the embedded controllers of equipment. Second level is a creation of a local managing network of personal computers, as consoles of the control system. The control system is functionally divided into four levels: 1) the controllers managing in a real-time mode by the executive equipment; 2) the workstations which are supporting the link with controllers by CAN-network; 3) the server of applications containing a dynamic database; 4) the PCs network for users applications. Examples of realisation of the software are presented.
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| MOPLT087 | Research of Possibility to use Beam Polarization for Absolute Energy Calibration in High-precision Measurement of Tau Lepton Mass at VEPP-4M | background, laser, vacuum, induction | 737 | ||
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Experiments of 2002-2003 years on measurement of duration of beam polarization existence in VEPP-4M electron-positron storage ring after injection of polarized beams from VEPP-3 booster at energies in the vicinity of tau-lepton production threshold (1777 MeV) are described. Polarized beams in such conditions are planned to use in the experiment at VEPP-4M with KEDR detector on high precision measurement of tau-lepton mass wiyh the help of resonant depolarization technique for absolute calibration of particle energy. It was shown that despite of closeness of the strong depolarizing integer spin resonance (1763 MeV) the polarization lifetime though is limited, but still is sufficient for realization of energy calibration procedure with a high accuracy (10-6).
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| MOPLT088 | Experimental Plasma Wake-field Acceleration Project at the VEPP-5 Injection Complex | plasma, background, laser, acceleration | 740 | ||
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The project of an experimental facility based on the VEPP-5 injection complex is described. Due to a good quality of electron or positron beams and special beam preparation system, the facility opens several possibilities for studies of the plasma wakefield acceleration: high peak beam currents, arbitrary beam profiles, long term beam-plasma interaction (up to the full driver depletion), and precise beam diagnostics. Various wakefield regimes can be experimentally demonstrated and studied: the efficient blow-out regime with a low energy spread and high acceleration rate (up to several GeV per meter); multibunch regime; long bunch instabilities; beam self-organization in plasma; plasma lens. If successfully realized, this experiment becomes a solid argument for feasibility of a high-energy collider based upon the plasma wakefield acceleration.
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| MOPLT089 | SOS-diode Based Pulser for the Injection System of the Collider VEPP-2000 | plasma, background, laser, acceleration | 743 | ||
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We describe high voltage pulsers for supplying of kickers of the collider VEPP-2000 injection system. The high voltage pulse is formed as a result of a sharp break of a high current, accumulated previously in storage elements, by means SOS-diode. Pulse forming lines or inductances could be used as the storage elements. The generators form the quasi-rectangular pulses on the 50-Ohm load. The generator scheme is described also.
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| MOPLT090 | High Pulse and Average Power Low-induction Load | plasma, background, laser, acceleration | 746 | ||
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A high pulse and average power low-induction load with a built-in divider is described in this report. The load has a nominal resistance of 25 Ohm and is designed to operate with a repetition rate of up to 50 Hz at a pulse duration (FWHM) of 100 ns, a rise/fall time of 50 ns and a pulse amplitude of up to 40 kV. In this mode the dissipated energy is equal to about 8 J per pulse and average power is up to 400 W. The load can be used as an absorbing load and as a block element in high-voltage engineering.
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| MOPLT091 | Accelerator Physics Issues of the VEPP-4M at Low Energy | plasma, background, laser, acceleration | 749 | ||
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The VEPP-4M electron-positron collider is being prepared for a new high-energy physics run in the 1.5 - 2.0 GeV energy range. During the first run (2001-2002), precision mass measurements of the J/psi and psi' mesons using the KEDR detector have been carried out with a record accuracy. To provide high performance, efforts for investigation and further development of the machine have been done. The most important results are described. A record absolute accuracy of energy measurement was achieved using the resonant depolarization method. A possibility to use this method for the absolute energy calibration in tau-lepton mass measurements is studied. For the first time, the Moeller polarimeter based on an internal polarized gas jet target has been developed and successfully used at the VEPP-3 booster storage ring. A system of energy measurement using Compton back-scattering has been put into operation. To increase the machine luminosity, operation with dipole wigglers is studied, and a project of turn-by-turn feedback system to suppress beam instabilities has been started. For beam diagnostics, a multi-anode photomultiplier tube and a white light coronograph were installed. The VEPP-4M operation experience with the longitudinal magnetic field within the KEDR detector is also described.
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| MOPLT092 | Single Mode RF Cavity for VEPP-2000 Storage Ring Based Collider | plasma, background, laser, acceleration | 752 | ||
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Accelerating cavity 172 MHz with strong damped higher-order modes (HOM) for VEPP-2000 electron-positron collider have been made in Novosibirsk. Resonance frequences and Q values of cavity HOMs are measured and analysed. Most of HOMs have Q values less than 300. We compare these results with computer calculations of HOM.
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| MOPLT096 | Machine Induced Background in the High Luminosity Experimental Insertion of the LHC Project | plasma, laser, acceleration, vacuum | 755 | ||
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The methodical approach, developed for the solution of the radiation problems in the LHC project, is used for the estimation of the machine induced background in the high luminosity experimental insertion IR1. The results of the cascade simulations are presented for the cases of the proton losses in the cold and warm parts of the collider. The formation of the machine induced background in the interaction region is discussed.
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| MOPLT097 | Co-sourcing Development of Accelerator Controls | plasma, laser, acceleration, vacuum | 758 | ||
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Frequently, accelerator facilities make use of products and services offered by the industry. This paper's focus is on such outsourcing of control system hardware and software. Firstly, an attempt is made to explain the facility's motivation for seeking outside help, which is typically due to lack of resources, technology or knowledge. Then, the risks of outsourcing are enumerated. To mitigate them, the industrial partner should have not only the adequate technical expertise, but also a reliable, yet agile management and quality assurance process that meets the facility's expectations, schedule, budget constraints, maintenance and support needs. Finally, Cosylab's business model is presented, designed to provide lasting open-source solutions that help not only a single facility, but the entire community.
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| MOPLT099 | NSC KIPT Accelerator on Nuclear and high Energy Physics | plasma, vacuum, electron, wakefield | 761 | ||
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One of the main reasons for the outflow of experts in nuclear physics and adjacent areas of science from Ukraine is the absence of modern accelerating facilities, for conducting research in the present fields of interest worldwide in this area of knowledge. A qualitatively new level of research can be achieved by the construction of a new generation accelerator applying the latest developments in the field of electron beam acceleration, in particular on the basis of superconducting accelerating structures of the TESLA type. Such structures may be used for continuous, polarized electron beams, which is crucial e.g. for thin(?) experiments checking modern theoretical models of interactions of nuclear substance, and for beams with high current and extremely short pulses for research in free electron laser and neutron physics. Such a facility will create an opportunity for carrying out research representing the interest of scientists from other countries, which will promote the integration of Ukrainian science into European and worldwide research.
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| MOPLT100 | Magnetic Structure of the NSC KIPT Nuclear-and-high-energy-physics Electron Accelerator | plasma, vacuum, wakefield, beamloading | 764 | ||
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Design options of the magnetic structure of a new proposed accelerator facility at NSC KIPT with a continuous-wave electron beam are described. The accelerator represents a recirculator, based on standard TESLA superconducting accelerating sections in one or two straight sections with a length of 5 or 19 meters. The magnetic system is designed on the basis of the magnetic elements of storage ring EUTERPE, transferred by Eindhoven University to NSC KIPT. The focusing and dispersion functions for several design choices of the magnetic structure are reported. Modeling of the beam movement in the accelerator has been carried out; the beam parameters during acceleration and on accelerator output have been calculated.
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| MOPLT101 | Performances of the Beam Generated by Metal-Dielectric Cathodes in RF Electron Guns | gun, electron, wakefield, beamloading | 767 | ||
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The paper describes results of the experimental research of the metal-dielectric cathode operation in RF electron gun. Application of these cathodes permits RF guns to generate intense beams with nanosecond current pulse duration. Electron beam is extracted from plasma sheath developed during the surface vacuum flashover dielectric. Simulated and experimental parameters of the beam obtained at the single-cavity RF gun output are summarized in the paper. The beam formation and its interaction with microwave field of high strength are analyzed qualitatively. Results are compared with experimental results obtained before in the 1.5-cavity RF electron gun. First experimental results on electron beam generation by the RF gun with a ferroelectric cathode are discussed in the paper.
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| MOPLT102 | To the Problem of Wake-field Excitation for Advanced Accelerator Concept | gun, electron, wakefield, beamloading | 770 | ||
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The advanced accelerator concept to use the wake-fields exited in dielectric by a sequence of electron bunches for high-gradient particle acceleration has been proposed and investigated in [*-***]. Two essential merits are being exploited. First of them [**] is the excitation by a regular sequence of electron bunches that allows superposing coherently the wake-fields excited by each bunch. The second one [***] concludes to multi-mode operation that leads to peaking of the resulting HF-field that is represented by a sequence of spikes of alternative signs with essentially higher amplitude comparatively to only principle mode excitation. The recent works performed in NSC/KIPT on theoretical studies, simulation, and experimental investigations of the wake-fields excitation by a train of 2 MeV electron bunches in a dielectric waveguide are presented. Transition and Cerenkov radiation excited by short bunches in a limited dielectric medium was theoretically investigated. The measurements of wake-fields output power and the electron energy spectrum were experimentally performed.
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* W.Gai, P.Schoessow, B.Cole et al. Phys. Rev. Lett. 61, 2756 (1988) ** I.N.Onishchenko, V.A.Kiselev, G.V.Sotnikov et al. Proc. 1995 Particle Accelerator Conf., p. 782-3*** T.B.Zhang, J.L.Hirshfield, T.C.Marshall et al Proc. 1997 Particle Accelerator Conf., V.42, No.3, p.1341 |
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| MOPLT103 | Radiation Resistant Magnetic Sensors for Accelerators | gun, electron, radiation, wakefield | 773 | ||
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The technology of obtaining the radiation resistant magnetic sensors, which characteristics remain stable under the irradiation with high dose of fast neutrons was designed. Radiation resistant sensors are developed on the base of InSb. While irradiation with neutron flux of 1010 n*cm-2*c-1 with energies 0.1…13 MeV, with the thermal neutrons part in the general flux of 20% and intermediate fluxes of 25%, the main sensors’ characteristics, that is their sensitivity to the magnetic field, change no more than for 0.05% up to the fluence of 1*1015 n*cm-2 and no more than for 1% up to the fluence of 3*1016 n*cm-2. Radiation resistant sensors are used for development of magnetic field monitoring system with measuring channels accuracy of 0,01%, which have a function of temperature measurement with the accuracy of 0.1 С at the place of sensor location, moreover, it has self diagnostics and self correction functions. This system passed the long-term testing of continuous 3 months operation at the Neutron Physics Laboratory, JINR, Dubna at the IBR-2 neutron reactor.
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| MOPLT104 | Quantitative Optimisation Studies of the Muon Front-End for a Neutrino Factory | gun, electron, radiation, wakefield | 776 | ||
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In a Neutrino Factory, short proton pulses hit a target, producing pions at widely varying angles and energies. Efficient pion capture is required to maximise the yield of decayed muons, which proceed via acceleration stages into a muon storage ring to produce neutrinos. This paper presents optimisation of a solenoidal decay channel designed for high-emittance pions, based on schemes from CERN and RAL. A non-linear tracking code has been written to run under an optimisation algorithm where every beamline element can be varied, which is then deployed as a distributed computing project. Some subsequent stages of muon beamline are also simulated, including RF and non-RF phase-rotation techniques and in one option, initial muon acceleration to 400MeV. The objective is to find optimal transmissions for each front-end concept.
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| MOPLT105 | Implementation of MICE at RAL | gun, electron, radiation, wakefield | 779 | ||
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The Muon Ionisation Cooling Experiment (MICE) is motivated by the vision of the neutrino factory (NF). The cost and practicality of the NF depends on an early control of the emittance of the muon beam that will be accelerated and stored to produce the neutrino beams. A number of possibilities for transverse cooling of the emittance have been proposed including ionisation cooling. In such a concept, the muon beam is alternatively slowed down in cryogenic absorbers (energy loss by ionisation) and then re-accelerated in RF cavities to replace the lost energy. This process reduces the transverse momentum of the beam while maintaining the average momentum in the z-direction. The energy absorbing material should be characterised by a high stopping power and low multiple scattering: The material of choice is liquid hydrogen. MICE will replicate a piece of the NF cooling channel. The engineering of a safe system with thin windows for the containment of the liquid hydrogen and other features needed to safely operate will test the practical application of the cooling scheme and its performance. MICE is proof of principle for this untried technology. The paper reviews progress in MICE and the plans for its implementation at RAL.
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The MICE Collaboration |
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| MOPLT106 | MICE: the Muon Ionisation Cooling Experiment | gun, electron, radiation, wakefield | 782 | ||
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The provision of intense stored muon beams would allow the properties of neutrinos to be measured precisely and provide a route to multi-TeV lepton-anti-lepton collisions. The short muon-lifetime makes it impossible to employ traditional cooling techniques while maintaining the muon-beam intensity. Ionisation cooling, a process in which the muon beam is passed through a series of liquid hydrogen absorbers followed by accelerating RF-cavities, is the proposed cooling technique. The international Muon Ionisation Cooling Experiment (MICE) collaboration proposes to perform an engineering demonstration of ionisation cooling. The MICE cooling channel, the instrumentation and the implementation at the Rutherford Appleton Laboratory is described together with the predicted performance of the channel and the measurements that will be made.
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| MOPLT107 | Nanosecond-timescale Intra-bunch-train Feedback for the Linear Collider: Results of the FONT2 Run | feedback, gun, electron, radiation | 785 | ||
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We report on experimental results from the December 2003/January 2004 data run of the Feedback On Nanosecond Timescales (FONT) experiment at the Next Linear Collider Test Accelerator at SLAC. We built a second-generation prototype intra-train beam-based feedback system incorporating beam position monitors, fast analogue signal processors, a feedback circuit, fast-risetime amplifiers and stripline kickers. We applied a novel real-time charge-normalisation scheme to account for beam current variations along the train. We used the system to correct the position of the 170 nanosecond-long bunchtrain at NLCTA, in both 'feed forward' and 'feedback' modes. We achieved a latency of 53 nanoseconds, representing a significant improvement on FONT1 (2002), and providing a demonstration of intra-train feedback for the Linear Collider.
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| MOPLT108 | TESLA Linac-IP Simulations | gun, radiation, luminosity, acceleration | 788 | ||
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We have formulated integrated simulations of the transport of the electron and positron bunches in the Linear Collider from the linac entrance through the beam delivery system and the interaction region, taking wakefield effects into account. We have set up the simulations to run on the 64-cpu prototpye Grid cluster at QMUL and generated results for various sets of input parameters for the TESLA and NLC machines. For TESLA we have evaluated the distortion of the phase-space of the bunches at the interaction point due to wakefields. We have calculated the luminosity degradation and the production of photons and e+e- pairs. We have simulated the performance of the intra-train beam feedback systems based on bunch position, angle and luminosity measures, and have evauated the luminosity recovery potential of these systems for TESLA and NLC.
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| MOPLT109 | Longitudinal Schottky Spectra of Bunched Beams | gun, radiation, luminosity, acceleration | 791 | ||
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In this paper we derive an expression for longitudinal Schottky spectrum of a bunched beam in a stationary bucket. The expression is then used to calculate longitudinal emittance of the antiproton beam in the Fermilab Recycler ring. The Recycler beam is bunched longitudinally by a barrier-bucket rf waveform. Under certain bucket conditions, dependence of synchrotron frequency on particle energy becomes non-monotonic. It complicates the Schottky spectrum derivation and interpretation; we address these difficulties in our paper.
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| MOPLT110 | Stochastic Cooling in Barrier Buckets at the Fermilab Recycler | gun, radiation, luminosity, acceleration | 794 | ||
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The Fermilab Recycler is a fixed 8-GeV kinetic energy storage ring located in the Fermilab Main Injector tunnel near the ceiling. The role of stochastic cooling in the Recycler is to pre-cool the transverse phase-space of injected antiprotons for efficient electron cooling. This requires a gated stochastic cooling system working on beam confined in a barrier bucket. The performance of this system is reviewed. In addition, a study of the cooling rates and asymmptotic emittances as a function of beam intensity is presented.
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| MOPLT111 | On using NEA Cathodes in an RF Gun | radiation, electron, luminosity, acceleration | 797 | ||
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RF guns have been proven to deliver high brightness beams and therefore appear attractive as electron source for a linear collider. Only so far no polarized beams have been produced. To create a polarized electron beam GaAs NEA cathodes are used. Operating rf guns with a NEA cathode poses concerns in three areas, oxidation by residual gas, ion bombardment, and electron bombardment. In this paper we report about an attempt to reduce the vacuum pressure inside the gun by cooling it to cryogenic temperatures. Furthermore the energy deposition by ions and electrons will be quantified.
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| MOPLT112 | Optimizing Non-Scaling FFAG Lattices for Rapid Acceleration | acceleration, radiation, luminosity, beamloading | 800 | ||
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A linear approach to fixed field acceleration was first proposed [*,**] and successfully developed to support the rapid and large-emittance acceleration of muons for a Neutrino Factory or Muon Collider. Lattices have evolved from a simple F0D0-cell base as first proposed to a slightly more complex layout that has been referred to as a triplet configuration. In this work a methodology is developed for optimizing nonscaling lattices which demonstrates that the appropriate description is minimum momentum compaction, alpha=(dL/L)/(dp/p). Further, the triplet configuration is not used conventionally as a focusing telescope, but rather its optics is shown to resemble that of a F0D0-cell. This methodology is then used to propose and compare lattices for muon acceleration. Specifically a 2.5-5, 5-10, and 10-20 GeV/c lattice is proposed for muon acceleration and also one for a small, 10-20 MeV/c electron prototype machine.
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* C. Johnstone, "FFAG Non-scaling Lattice Design", talk, Proc 4th Int Conf on the Physics Potential and Development of the m+ m- Colliders, San Francisco, CA Dec.10-12, 1997, pgs 696-698** F. Mills, "Linear Orbit Recirculators", ibid, pgs 693-696 |
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| MOPLT114 | Modeling of Beam Loss in Tevatron and Backgrounds in the BTeV Detector | acceleration, radiation, luminosity, beamloading | 803 | ||
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Detailed STRUCT simulations are performed of beam loss rates in the vicinity of the BTeV detector in the Tevatron C0 interaction region due to beam-gas nuclear elastic interactions, outscattering from the collimator jaws and an accidental abort kicker prefire. Corresponding showers induced in the machine components and background rates on the BTeV Detector are modeled with the MARS14 code. It is shown that a steel mask located in front of the last four dipoles upstream the C0 can reduce the accelerator-related background rates in the detector by an order of magnitude.
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| MOPLT115 | Numerical Simulations and Analyses of Beam-Induced Damage to the Tevatron Collimators | acceleration, radiation, luminosity, beamloading | 806 | ||
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Numerical simulations are performed to analyze the Tevatron collimator damage happened in December 2003 that was induced by a failure in the CDF Roman Pot detector positioning during the collider run. Possible scenarios of this failure resulted in an excessive halo generation and superconducting magnet quench are studied via realistic simulations using the STRUCT and MARS14 codes. It is shown that the interaction of a misbehaved proton beam with the collimators result in a rapid local heating and a possible damage. A detailed consideration is given to the ablation process for the collimator material taking place in high vacuum. It is shown that ablation of tungsten (primary collimator) and stainless steel (secondary collimator) jaws results in creation of a groove in the jaw surface as was observed after the December's accident.
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| MOPLT117 | An Electron Front End for the Fermilab Multi-species 8 GeV SCRF Linac | acceleration, electron, radiation, linac | 809 | ||
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Fermilab is considering 8 GeV superconducting linac whose primary mission is to serve as an intense H- injector for the main injector. This accelerator is also planned to be used for accelerating various other species (e.g. electrons and muons). In the present paper we investigate the possibility of such a linac to accelerate a high brightness electron beam to ~7 GeV. We propose a design for the electron front end, based on a photoinjector, and consider the electron beam dynamics along the linac. Start-to-end simulations of the full accelerator for electrons are presented. Finally the potential applications of the such an electron beam are discussed.
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| MOPLT118 | Muon Test Area at Fermilab | acceleration, electron, radiation, luminosity | 812 | ||
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A construction of a new experimental area designed to develop, test and verify muon ionization cooling using the 400- MeV Fermilab Linac proton beam was finished in fall of 2003. This area will be used initially for cryogenic tests of liquid-hydrogen absorbers for the MUCOOL R&D program and, later, for high-power beam tests of these absorbers and other prototype muon-cooling apparatus. The experimental scenarios being developed for muon facilities involve collection, capture, and cooling of large-emittance, high-intensity muon beams–~1013 muons at a repetition rate of 15Hz, so that conclusive tests of the apparatus require full Linac beam, or 1.6 x 1013 p at 15 Hz. The area has 12MW 805MHz, 5MW 201MHz RF, 4K Helium, 500W refrigeration and 400MeV H-/proton beam.
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| MOPLT119 | Fabrication of X-band Accelerating Structures at FERMILAB | acceleration, vacuum, electron, radiation | 815 | ||
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The RF Technology Development group at Fermilab is working together with the NLC and GLC groups at SLAC and KEK on developing technology for room temperature X-band accelerating structures for a future linear collider. We built seven 60cm long, high phase advance, detuned structures (HDS or FXB series). These structures have 150 degrees phase advance per cell, and are intended for high gradient tests. The structures were brazed in a vacuum furnace with a partial pressure of argon, rather than in a hydrogen atmosphere. We have also begun to build 60cm long, damped and detuned structures (HDDS or FXC / FXD series). So far, we have built 3 FXC structures. Our goal is to build 4 FXC and 2 FXD structures for the 8-pack test at SLAC by the end of March 2004, as part of the GLC/NLC effort to demonstrate the readiness of room temperature RF technology for a linear collider. This poster describes the RF structure factory infrastructure (clean rooms, vacuum furnaces, vacuum equipment, RF equipment etc.), and the fabrication techniques utilized (the machining of copper cells / couplers, quality control, etching, vacuum brazing, cleanliness requirements etc.) for the production of FXB and FXC structures.
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| MOPLT120 | Proposals for Improvements of the Correction of Sextupole Dynamic Effects in the Tevatron Dipole Magnets | acceleration, vacuum, electron, radiation | 818 | ||
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It is well known that the sextupole (b2) components in the superconducting dipole magnets decay during the injection plateau and snap back rapidly at the start of the ramp to flat top current. These so-called dynamic effects were originally discovered in the Tevatron. They are compensated for by the chromaticity correctors distributed around the ring. Imperfect control of the chromaticity during the snapback can contribute to beam loss and emittance growth. A thorough investigation of the chromaticity correction in the Tevatron was launched in the context of Run II, including beam chromaticity measurements and extensive magnetic measurements on a series of spare Tevatron dipole magnets. The study has yielded new information about the effect of the powering history on the dynamic b2. A companion paper at this conference describes in detail the results of these magnetic measurements [reference to George Velev's paper]. Study findings have given directive to new proposals for improvement of the b2 snapback correction in the Tevatron, including a revised functional form for the snapback algorithm and the elimination of the beam-less pre-cycle. This paper reports the results of beam studies performed recently to test these improved procedures.
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| MOPLT121 | Water Flow Vibration Effect on the NLC RF Structure-girder System | acceleration, vacuum, electron, radiation | 821 | ||
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In order to meet the vibration budget for the Next Linear Collider main Linac components, the vibration sources in the NLC girder are being studied. The activity is focused on the vibration induced by the cooling water flow for the 60 cm long accelerating copper structures. Understanding the vibration in the structures will enable us to push forward the design of the interface between the structures and the quadrupoles. This paper reports on the ongoing work and presents results from experimental data as well as finite element simulations.
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| THPLT031 | Comparison of Rate Equation Models for Equilibrium Beam Parameters | antiproton, positron, gun, lattice | 2541 | ||
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We calculate equilibrium beam parameters from the counteraction of intrabeam scattering (IBS), electron cooling (EC) and target interaction for typical beams in the GSI cooler storge ring ESR and in the proposed HESR. This work is complementary to kinetic modeling efforts at GSI. We developed an easy to use simulation tool that includes various models for the EC rates and the IBS rates, averaged of the detailed ring lattices. The obtained scaling of the equilibrium parameters with beam current and energy are compared with existing experimental data from the ESR and with kinetic simulation results for the HESR.
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| THPLT032 | Computer Controlled Beam Diagnostics for the HICAT Facility | antiproton, positron, gun, lattice | 2544 | ||
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A set of 93 diagnostic devices for beam diagnostics in the heavy ion cancer therapy facility (HICAT) at the university hospital in Heidelberg is currently under development at GSI. For the HICAT facility that is presently under construction, all beam diagnostic devices are fully computer controlled and allow an automated detection of all relevant beam parameters. The HICAT rasterscan method with active variation of intensity, energy and beam size requires the exact knowledge of the time resolved and spatial structure of the ion beam. An overview of the integrated devices is presented and the intensity measurement of both, the DC and AC beam in the different parts of the accelerator facility are reviewed. Additionally, the timing and control of the diagnostic devices are described.
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