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| MOP010 | Massively Parallel Wake Field Computations in Long Accelerator Structures | simulation, vacuum, shielding, electron | 52 | ||
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The X-FEL project and the ILC require a high quality beam with ultra short bunches. The knowledge of the short-range wakefields in the TESLA cavities and the collimators is needed to predict the beam quality in terms of the single bunch energy spread and emittance. Especially for the high energy collimators these calculations are limited by numerical dispersion. Earlier we presented wake field calculations for short bunches in long structures for rotationally symmetric components with the code ECHO. Now we present first results from our new wake field code in fully 3D. To calculate the effect of the longitudinal and transverse wakefields we have used the time domain numerical approach. For sufficient resolution of the geometric boundaries and the short bunches (down to the nm-range), huge computational resources are needed. Thus in 3D massive parallelisation of the code is necessary. In addition we used the technique of a moving grid, which gives access also to very long structures, i.e. a complete module of eight TESLA cells or a high energy collimator.
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| MOP020 | Status of the PITZ Facility Upgrade | gun, cathode, emittance, booster | 76 | ||
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The upgrade of the Photo Injector Test Facility at DESY in Zeuthen towards the PITZ2 stage is continuously ongoing. In Spring 2006, an intermediate stage was taken into operation (PITZ1.6), including a new gun cavity that has been tuned and conditioned. Currently, three new emittance measurement systems are being installed along the beamline. After their commissioning, studies of the emittance conservation principle will be possible when using the available booster cavity. In the paper, the results of the RF commissioning of the new gun and the first beam measurements using recently installed diagnostics devices will be presented. The ongoing developments of further new diagnostics components will be discussed as well.
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| MOP048 | Installation of the French High-Intensity Proton Injector at Saclay | rfq, proton, linac, shielding | 153 | ||
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The installation of the French high intensity injector “IPHI” is in progress on the Saclay site. The proton source, RF power system, cooling plant, diagnostics line as well as shielding are now in place. The first sections of the RFQ cavity are installed on their supports. Commissioning is planned during the first half of 2007. At the beginning of 2008, a beam chopper, developed at Cern, will be inserted between the RFQ and the diagnostics line and tested with a proton beam. At the end of 2008, part of IPHI will be moved from Saclay to Cern. New tests, intended for the LINAC4 project, will be carried out using a negative hydrogen beam. This paper describes the fabrication and assembly operations. The future of IPHI at Cern is evoked.
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| MOP054 | Status of the SARAF Project | rfq, ion, ion-source, emittance | 168 | ||
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Soreq NRC recently initiated the establishment of SARAF – Soreq Applied Research Accelerator Facility. SARAF will be a multi-user facility for basic, medical and biological research, non-destructive testing (NDT) and research, development and production of radio-isotopes for pharmaceutical purposes. An on going major activity is research and development of high heat flux (up to 80 kW on a few cm2) irradiation targets. SARAF is based on a continuous wave (CW), proton/deuteron RF superconducting linear accelerator with variable energy (5–40 MeV) and current (0.04-2 mA). SARAF is designed to enable hands-on maintenance, which implies beam loss below 10-5 for the entire accelerator. The commissioning of the Phase I of SARAF (full current, energy up to 4-5 MeV) is taking place during 2006 at Soreq. This paper describes the SARAF project and presents commissioning of the normal conducting injector (i.e., ECR ion source and RFQ). Test results of the β=0.09 half wave superconducting resonators are presented, and resonator geometry improvements with respect to electron multipacting behavior is discussed. An outlook on the project regarding reaching the final energy of 40 MeV is given.
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| MOP055 | Transport of LANSCE-Linac Beam to Proposed Materials Test Station | target, quadrupole, emittance, dipole | 171 | ||
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Refurbishment of Experimental Area A and installation of a Materials Test Station is planned at the Los Alamos Neutron Science Center (LANSCE). This paper describes the beamline to transport 800-MeV protons from the accelerator to Area A. The beamline has the minimum number of quadrupoles necessary to achieve the desired instantaneous beam parameters at the target, the appropriate beam-centroid excursions at the split target for painting the two target halves, and a beam-centroid crossover upstream of the target to facilitate shielding of upstream components from backstreaming neutrons. Options in the composition of the raster-magnet section represent trade-offs between the number of magnets and the severity of the effects of magnet failures. Beam diagnostics are an integral part of the beamline design. Instantaneous and painted beam sizes at the target can be inferred by observing the beam at properly chosen upstream locations. A beamline spur to a tune-up beam dump is planned.
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| TUP011 | Upgrade of Beam Diagnostics in LEBT and MEBT of J-PARC LINAC | monitoring, linac, vacuum, rfq | 268 | ||
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After tests in Tsukuba-site, Front end part (from an ion source upto the first drift tube linac) of J-PARC LINAC was transported to Tokai-site. From the coming December, testing with H- beam is planned. After the tests in Tsukuba, a few beam current monitors are added in the low and the medium energy transport line, and those monitors are used for the machine- and the person-protection system. In this paper, design and roles of each monitor are described.
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| TUP023 | Beam-Size Measurements in the IPNS 50-MeV Transport Line Using Stripline BPMs | linac, quadrupole, controls, monitoring | 296 | ||
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Continuing with the work started two years ago, the technique of using a two-beamlet model to measure beam size is presented. Beam signals are detected on terminated 50-ohm, stripline BPMs located in the transport line between the 50 MeV linac and rapid cycling synchrotron. Each BPM is constructed with four striplines: top, bottom, left and right. Using a fast-sampling oscilloscope to compare the signals from opposite strip lines allows one to determine beam size assuming a two beamlet model. Measurements made with the two-beamlet approach are compared with other standard profile diagnostics such as wire-scanners, segmented Faraday cups, and scintillators. Advantages of the two-beamlet method are that it is non intrusive and does not require the presence of a background gas necessary for an IPM. Disadvantages of the technique are that it does not provide a detailed profile and the longitudinal beam pulse length must be short relative to the stripline length.
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| TUP031 | Beam Dynamics Studies on the ISAC-II Superconducting Linac | linac, emittance, acceleration, bunching | 312 | ||
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The ISAC-II superconducting linac is presently in the beam commissioning phase. The linac lattice consists of modules of four quarter wave cavities and one superconducting solenoid. Beam steerers between cryomodules compensate for steering effects due to misalignments in the solenoids. Beam dynamics aspects of linac commissioning will be highlighted.
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| TUP080 | Tuning the Magnetic Transport of an Induction Linac Using Emittance | emittance, simulation, background, optics | 444 | ||
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The Lawrence Livermore National Laboratory Flash X-Ray (FXR) machine is a linear induction accelerator used to produce a nominal 20-MeV, 3-kA, 60-ns pulse width electron beam for hydrodynamic radiographs. A common figure of merit for this type of radiographic machine is the x-ray dose divided by the spot area on the bremsstrahlung converter. Several characteristics of the beam affect the minimum attainable x-ray spot size. The most significant are emittance, chromatic aberration, and beam motion. FXR is in the midst of a multi-year optimization project to reduce the spot size. This paper describes the effort to reduce beam emittance by adjusting the fields of the transport solenoids. If the magnetic transport is not correct, the beam will be mismatched and undergo envelop oscillations increasing the emittance. We measure the divergence and radius of the beam in a drift section after the accelerator by imaging the optical transition radiation (OTR) and beam envelope on a foil. These measurements are combined with transport simulations to calculate an emittance. Relative changes in the emittance can be quickly estimated allowing for an efficient, real-time study.
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| TH1001 | The Linac Coherent Light Source (LCLS) Accelerator | electron, linac, feedback, undulator | 511 | ||
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The Linac Coherent Light Source (LCLS) is a SASE x-ray Free-Electron Laser (FEL) based on the final kilometer of the Stanford Linear Accelerator. Such an FEL requires a high energy, high brightness electron beam to drive the FEL instability to saturation. When fed by an RF-photocathode gun, and modified to include two bunch compressor chicanes, the SLAC linac will provide such a high quality beam at 14 GeV and 1-micron normalized emittance. In this talk, we report on recent linac studies, including beam stability and tolerances, longitudinal and transverse feedback systems, conventional and time-resolved diagnostics, and beam collimation systems. Construction and installation of the injector through first bunch compressor will be complete by November 2006, and electron commissioning is scheduled to begin in December of that year.
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| TH2002 | Timing and Synchronization in Large-Scale Linear Accelerators | laser, radiation, electron, linac | 536 | ||
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New coherent light sources are based on large scale linear accelerator; the adopted single pass acceleration scheme allows the preservation of bunch 6D phase space leading to ultra short (<100fsFWHM) and ultra bright (average Brilliance = 1024 (1) ph/sec/mm2/mrad2/0.1%bw) pulses of coherent radiation in the DUV-x-ray regions. Femto-second lasers are deeply integrated in the electron bunch and photon pulse generation, in diagnostic set-ups and in time resolved experiments: the timing may be as low as 10% of pulse duration. The requirements on the stability of RF acceleration call for distribution of ultra-stable and ultra-low phase noise reference signal for the Low Level RF feedback loops. A non reversible breakthrough into the adoption of optical and O/E techniques is on-going which is taking advantage on five order of magnitude reduction in the period of the carrier. Being the current limit represented by the carrier-envelope stabilization techniques, sub-fs jitters have been demonstrated in the laboratory; the preservation of laboratory levels of jitters and stability over the whole accelerator premises is the next step. On-going efforts and results let us be optimistic.
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Interim Report of the Scientific and Technical Issues (XFEL-STI) Working Group ona European XFEL facility in Hamburg, January 11, 2005. |
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| THP001 | Conceptual LLRF Design for the European X-FEL | controls, feedback, klystron, resonance | 559 | ||
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The LLRF System for the superconducting cavities of the European X-FEL must support an amplitude and phase stability of the accelerating fields of up to 0.01% and 0.01 deg. respectively. The stability must be achieved in pulsed operation with one klystron driving 32 cavities. This goal can only be achieved with low noise downconverters for field detection, high gain feedback loops and sophisticated feedforward techniques. State-of-the art technology including analog multipliers for downconversion, fast ADCs (>100 MHz) with high resolution (up to 16 bit), and high performance data processing with FPGAs with low latency (few hundred ns) allow to meets these goals. The large number of input channels ( >100 including probe, forward and reflected signal of each of the 32 cavities) and output channels (>34 including piezo tuners for each cavity) combined with the tremendous processing power requires a distributed architecture using Gigalink interfaces for low latency data exchange.
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| THP021 | Study of Vacuum Insulator Flashover for Pulse Lengths of Multi-Microseconds | plasma, cathode, vacuum, electron | 610 | ||
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We have studied the flashover of vacuum insulators for applications where high voltage conditioning of the insulator and electrodes is not practical and for pulse lengths on the order of several microseconds. The study was centered about experiments performed with a 100-kV, 10-μs pulsed power system and supported by a combination of theoretical and computational modeling. The base line geometry for the experiments was a cylindrically symmetric, +45° insulator between flat electrodes. In the experiments, flashovers or breakdowns were localized by operating at field stresses slightly below the level needed for explosive emissions with the base line geometry. The electrodes and/or insulator were then seeded with an emission source, e.g. a tuff of velvet, or a known mechanical defect. Our study differs from most vacuum insulator studies in that our emphasis was on flashovers originating at the anode triple junction as well as bulk breakdowns within the insulator. Various standard techniques were employed to suppress cathode-originating flashovers/breakdowns. We present the results of our experiments and discuss the capabilities of modeling insulator flashover.
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| THP039 | Status of the RF Systems for the SPIRAL2 Linac at the Beginning of the Construction Phase | controls, rfq, ion, linac | 664 | ||
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The Spiral 2 project uses an RFQ and a superconductiong linac to accelerate high intensity beams of deuterons and heavier ions. The accelatoror frequency is 88 MHz. The construction phase was approved in Mai 2005 and the project organization was recently finalized. The RF Systems activity includes power amplifiers and control electronics for all the accelerator and some of the RF devices on the beam line: the slow and fast chopper and the rebunchers. The paper describes the status of the amplifiers prototypes, the architecture chosen for the digital LLRF and the preliminary studies on the other RF devices.
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| THP054 | Spoke Cavity Developments for the EURISOL Driver | vacuum, proton, cryogenics, linac | 704 | ||
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EURISOL is the next generation of Radioactive Ion Beam (RIB) facility which aims at the provision of high intensity beams of radioactive nuclei with variable energy, from a few keV to greater than 100 MeV per nucleon, at an intensity several orders of magnitude higher than those currently available. The driver of EURISOL has to accelerate protons at a final energy of 1 GeV and 5 mA current, but also deuterons at 200 MeV (total energy). For the intermediate energy part of the driver, a solution based on superconducting (SC) spoke cavities is under study at the IPN Orsay laboratory. In this paper are presented the results of beam dynamics simulations for the linac, experimental results on the β = 0.15 spoke cavity, as well as achievements on the power coupler and cold tuning system. A new horizontal cryostat for performing a test of a fully equipped spoke cavity is detailed and an optimized design for a new β ~0.35 spoke prototype is also presented.
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