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MOZCH02 | Start to End Simulations of Low Emittance Tuning and Stabilization | collider, emittance, synchrotron, damping | 31 | ||||||
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The principal beam dynamics challenge to the subsystems between the damping ring and the collision point of future linear colliders is expected to be the tuning and stabilization required to preserve the transverse emittance and to collide nanometer-scale beams. Recent efforts have focused on realistically modelling the operation and tuning of this region, dubbed the Low Emittance Transport (LET). We report on the development of simulation codes which permit integrated simulation of this complex region, and on early results of these simulations. Future directions of LET simulation are also revealed.
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Video of talk
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MOOCH01 | Beam Based Alignment at the KEK-ATF Damping Ring | damping, alignment, emittance, synchrotron | 36 | ||||||
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The damping rings for a future linear collider will have demanding alignment and stability requirements in order to achieve the low vertical emittance necessary for high luminosity. The Accelerator Test Facility (ATF) at KEK has successfully demonstrated the <5 pm vertical emittance specified for the GLC/NLC Main Damping Rings [*]. One contribution to this accomplishment has been the use of Beam Based Alignment (BBA) techniques. The mode of operation of the ATF presents particular challenges for BBA, and we describe here how we have deduced the offsets of the BPMs with respect to the quadrupoles. We also discuss a technique that allows for direct measurements of the beam-to-quad offsets.
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* "Extremely Low Vertical-Emittance Beam in the Accelerator Test Facility at KEK", K. Kubo, et al., Phys.Rev.Lett.88:194801,2002 |
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Video of talk
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MOOCH02 | First Full Beam Loading Operation with the CTF3 Linac | acceleration, alignment, emittance, linac | 39 | ||||||
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The aim of the CLIC Study is to investigate the feasibility of a high luminosity, multi-TeV linear e+e- collider. CLIC is based on a two-beam method, in which a high current drive beam is decelerated to produce 30 GHz RF power needed for high-gradient acceleration of the main beam running parallel to it. To demonstrate the outstanding feasibility issues of the scheme a new CLIC Test Facility, CTF3, is being constructed at CERN by an international collaboration. In its final configuration CTF3 will consist of a 150 MeV drive beam linac followed by a 42 m long delay loop and an 84 m combiner ring. The installation will include a 30 GHz high power test stand, a representative CLIC module and a test decelerator. The first part of the linac was installed and commissioned with beam in 2003. The first issue addressed was the generation and acceleration of a high-current drive beam in the "full beam loading" condition where RF power is converted into beam power with an efficiency of more than 90%. The full beam loading operation was successfully demonstrated with the nominal beam current of 3.5 A. A variety of beam measurements have been performed, showing good agreement with expectations.
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Video of talk
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MOOCH03 | Status of a Linac RF Unit Demonstration for the NLC/GLC X-band Linear Collider | acceleration, alignment, emittance, damping | 42 | ||||||
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Designs for a future TeV scale electron-positron X-band linear collider (NLC/GLC) require main linac units which produce and deliver 450 MW of rf power at 11.424 GHz to eight 60 cm accelerator structures. The design of this rf unit includes a SLED-II pulse compression system with a gain of approximately three at a compression ratio of four, followed by an overmoded transmission and distribution system. We have designed, constructed, and operated such a system as part of the 8-Pack project at SLAC. Four 50 MW X-band klystrons, running off a common 400 kV solid-state modulator, drive a dual-moded SLED-II pulse compression system. The compressed power is delivered to structures in the NLCTA beamline. Four 60 cm accelerator structures are currently installed and powered, with four additional structures and associated high power components available for installation late in 2004. We describe the layout of our system and the various high-power components which comprise it. We also present preliminary data on the processing and initial high-power operation of this system.
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Video of talk
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MOPKF003 | Design of 2 T Wiggler Vacuum Chamber for the LNLS Storage Ring | acceleration, alignment, emittance, damping | 300 | ||||||
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A 2 T wiggler with 2.8 m long and a gap of 22 mm will be installed at LNLS storage ring. The main requirements of the chamber design are short conditioning time and low mechanical deformation. Two different designs in stainless steel are proposed for the prototypes, an elliptical tube and a machined sheet. A pressure profile simulation with and without a NEG coating were made for evaluating the life-time influence and the time necessary for conditioning. A simulation with finite element of mechanical deformation for both case show equivalent results. The first prototype was made with the elliptical tube and a NEG coating deposition will be made at ESRF. The second prototype with machined parts is under construction and will be TIG welded. Descriptions of mounting structure for the prototype are show and the evaluation the dimension tolerance of the chambers.
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THPKF062 | Comparison of Dose Distribution Prediction in Targets Irradiated by Electron Beams with Dosimetry | target, gun, beamlosses, laser | 2403 | ||||||
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The features of the absorbed depth-dose distribution (DDD) on boundaries of two contacting materials and material with air irradiated with an electron beam (EB) were predicted by simulation with the software ModeRTL (Modeling of the radiation-technological lines (RTL)). Validation of DDD prediction with dosimetry was fulfilled on the industrial RTL with linear electron accelerator LAE 13/9 at the INCT, Warsaw. Simulation and measurement of boundary effects of DDD were carried out for targets irradiated by scanning EB with energy 10 MeV on moving conveyer. The irradiated materials were represented as parallelepipeds with all sizes greater than range of electrons in material. Cellulose Triacetate (CTA) dosimetric film (FTR-125) in form of strips inserted between materials and air in parallel with an axis of EB was used for dosimetry. Such irradiation setup allows to receive the complete curve of DDD on the boundary of contacting materials by one dosimetric film. The physical regularities for DDD on the boundary of contacting materials predicted by simulation methods were experimentally confirmed. Investigation of those anomalies is necessary in practice to estimate the quality of an irradiation performed on RTL at realization of various industrial EB processing.
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THPKF063 | Parameters of X-ray Radiation Emitted by Compton Sources | target, gun, beamlosses, brilliance | 2406 | ||||||
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Presented are results of analytical study on Xray beam parameters generated in the Compton storage rings. A model with the given circulating electron bunch parameters and the laser splash as well is considered. For this model, the total yield of xray quanta is derived as a function of the crossing angle and geometric dimensions of both the bunch and splash. Also spectral characteristics of emitting xray beam are evaluated with account for the collimating conditions and both the angular and energy spreads in the bunch. As is shown the width of xray energy spectrum is narrowest for the x-ray beam collimated along the bunch orbit. With increasing the scattering angle (with respect to the bunch orbit) the spectrum of emitting quanta is widening. Problems of x-ray beam generation with required energy and brightness with the Compton storage rings are discussed.
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THPKF064 | Status of Kharkov X-ray Generator based on Compton Scattering NESTOR | target, vacuum, gun, beamlosses | 2409 | ||||||
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Nowadays the sources of the X-rays based on a storage ring with low beam energy and Compton scattering of intense laser beam are under development in several laboratories. In the paper the state-of-art in development and construction of cooperative project of a Kharkov advanced X-ray source NESTOR based on electron storage ring with beam energy 43 - 225 MeV and Nd:YAG laser is described. The layout of the facility is presented and main results and constructing timetable are described. The designed lattice includes 4 dipole magnets with combined focusing functions, 20 quadrupole magnets and 19 sextupoles with octupole component of magnetic field. At the present time a set of quadrupole magnet is under manufacturing and bending magnet reconstruction is going on. The main parameters of developed vacuum system providing residual gas pressure in the storage ring vacuum chamber up to 10-9 torr are presented along with testing measurement at NSC KIPT vacuum bench. The facility is going to be in operation in the middle of 2006 and generated X-rays flux is expexted to be of about 1013 phot/s.
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THPKF066 | Conception of X-ray Source Based on Compact Wakefield Undulator | target, vacuum, gun, undulator | 2412 | ||||||
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Study of interaction of bunched charged ultrarelativistic particles with own wakefields in periodic rf structures detects new applications in the area of accelerator physics and technology. Conception of monochromatic X-ray source based on wakefield undulator, WFU, with very short period is presented. In the base of photon generation by the WFU lies a new mechanism of undulator-type radiation emitted by an ultrarelativistic electron bunch that undulates due to non-synchronous spatial harmonics of its wakefields while the bunch moves along a periodic waveguide. The features of the hard radiation and yield of photons depending on waveguide sizes and charge distribution are considered. The creation of the WFU with sub-millimetre periods due to advanced accelerator technology, such as deep X-ray lithography, opens possibilities to obtain high brightness X-rays at employing comparatively low electron energies without external alternative fields. That can have commercial significance for technological and medical applications.
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THPKF067 | Progress of the DIAMOND Storage Ring and Injector Design. | target, vacuum, gun, undulator | 2415 | ||||||
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DIAMOND is a state of the art 3 GeV synchrotron light source that will be available to users in 2007. Considerable further progress has been made on the accelerator physics design of the storage ring, booster and other associated injector systems. Detailed analysis of injection processes, lifetime, coupling, instabilities, feedback systems and dynamic aperture have been undertaken driven by the procurement activity and the desire to fully understand all aspects of the accelerator's performance.
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THPKF070 | A Beam Based Alignment System at the CAMD Light Source | target, vacuum, gun, emittance | 2424 | ||||||
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Beam based alignment is being applied to the CAMD light source. It is implemented by a flexible and versatile system of electronic shunts which are applied to each of the storage ring lattice quadrupoles. The essential design features of the electronic shunts are described as is the routine operation of the full system. The improvement to the corrected closed orbit from using the system is shown. Preliminary results are presented of the use of the shunts for correcting the lattice functions.
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THPKF071 | Linear Coupling and Lifetime Issues in the DIAMOND Storage Ring | target, vacuum, coupling, gun | 2427 | ||||||
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In synchrotron light sources the correction of the linear coupling is an important issue related to the brightness of the photon beam and to the beam lifetime. The vertical emittance of the electron beam in the DIAMOND storage ring will be controlled using 168 skew quadrupoles embedded in the sextupoles of the ring. In this paper we report the linear coupling estimates for the expected misalignment errors and we compare the results of coupling correction with different correction strategies. The effect on lifetimes is also discussed.
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THPKF072 | Progress with the Diamond Light Source | coupling, gun, insertion, target | 2430 | ||||||
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Construction of Diamond, the UK?s new 3 GeV, 3rd generation synchrotron light source, is well underway and progressing in-line with the original target of starting storage ring commissioning in January 2006 and being operational for users in January 2007. Having completed the foundations, the main building works are now proceeding at their maximum rate. Most of the major machine components are also under construction, aiming towards the key target date of starting machine installation in September 2004. As well as reporting on the overall status, detailed design developments and component choices will be summarised. The results of tests of various prototype components, including magnets, vacuum vessels and girders, will also be presented.
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THPKF073 | CIRCE, the Coherent InfraRed CEnter at the ALS | coupling, gun, insertion, target | 2433 | ||||||
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CIRCE (Coherent InfraRed Center) is a new electron storage ring to be built at the Advanced Light Source (ALS) of the Lawrence Berkeley National Laboratory (LBNL). The ring design is optimized for the generation of coherent synchrotron radiation (CSR) in the terahertz frequency range. CIRCE operation includes three possible modes: ultra stable CSR, femtosecond laser slicing CSR and broadband SASE. CSR will allow CIRCE to produce an extremely high flux in the terahertz frequency region. The many orders of magnitude increase in the intensity is the basis of our project and enables new kinds of science. The characteristics of CIRCE and of the different modes of operation are described in this paper.
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THPKF075 | LUX - A Recirculating Linac-based Facility for Ultrafast X-ray Science | radiation, electron, linac, coupling | 2436 | ||||||
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We present design concepts for LUX - a proposed source of ultra-fast synchrotron radiation pulses based on a recirculating superconducting linac. The source produces high-flux VUV-x-ray pulses with duration of 100 fs or less at a 10 kHz repetition rate, optimized for the study of ultra-fast dynamics across many fields of science. Cascaded harmonic generation in free-electron lasers (FEL's) produces coherent radiation in the VUV-soft x-ray regime, and a specialized technique is used to compress spontaneous emission for ultra-short-pulse photon production in the 1 - 10 keV range. High-brightness electron bunches of 2-3 mm-mrad emittance at 1 nC charge in 30 ps duration are produced in an rf photocathode gun and compressed to 3 ps duration following an injector linac, and recirculated three times through a 1 GeV main linac. In each return path, harmonic cascades are inserted to produce seeded FEL radiation in selected photon energy ranges from approximately 20 eV with a single stage of harmonic generation, to 1 keV with a four-stage cascade. The lattice is designed to minimize emittance growth from effects such as coherent synchrotron radiation (CSR), and to propagate electron beams carrying nm-scale density modulation in the final stages of cascaded harmonic generation. Synchronization of tens of femtoseconds is achieved by use of an optical master oscillator distributing timing signals over actively stabilized fiber, and generation of rf signals from the optical master oscillator. We describe technical developments in key areas including injection from a high repetition rate rf photocathode gun, lattice design, UV and soft x-ray production by high-gain harmonic generation, a kicker design for rapid transfer of the electron beam between radiator beamlines, lasers systems concepts, and synchronization between experimental pump lasers and the x-ray pulse.
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THPKF076 | Plan to Upgrade the Advanced Light Source to Top-off Injection Operation | radiation, electron, linac, insertion | 2439 | ||||||
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The brightness and thermal stability of the Advanced Light Source (ALS) is lifetime limited. Brightness improvements such as narrower gap insertion devices, smaller emittance coupling, and higher currents all result in short lifetimes. In addition current changes over a fill impact the thermal stability of both the storage ring and beamlines. In order to mitigate these limitations there is a plan to upgrade the injector of the ALS to full energy injection and to operate in a quasi-continuous filling (Top-Off) injection operation. With Top-Off, the ALS will increase its time-averaged current by two, reduce the vertical emmittance, and operate with smaller gap insertion devices. In this paper we describe our upgrade plan.
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THPKF077 | A Fiber Optic Synchronization System for LUX | radiation, linac, laser, insertion | 2442 | ||||||
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The proposed LUX femtotsecond light source will support pump-probe experiments that will need to synchronize laser light pulses with electron-beam-generated X-ray pulses to less than 50fs at the experimenter endstations. To synchronize multiple endstation lasers with the X-ray pulse, we are developing a fiber-distributed optical timing network. A high stability clock signal from a modelocked laser is distributed via fiber to RF cavities (controlling X-ray probe pulse timing) and modelocked lasers at endstations (controlling pump pulse timing). The superconducting cavities are actively locked to the optical clock phase. Most of the RF timing error is contained within a 10kHz bandwidth, so these errors and any others affecting X-ray pulse timing (such as RF gun phase) can be detected and transmitted digitally to correct laser timing at the endstations. The lasers? timing jitter is limited to low frequency, and thus they will follow the controls (clock plus error correction) without adding much wideband error. Time delay through the fibers will be stabilized by comparing a retroreflected pulse from the experimenter endstation end with a reference pulse from the sending end, and actively controlling the fiber length. Numerical simulations and initial synchronization experimental results will be presented.
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THPKF078 | Coherent Infrared Radiation from the ALS Generated via Femtosecond Laser Modulation of the Electron Beam | electron, linac, laser, insertion | 2445 | ||||||
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Interaction of an electron beam with a femtosecond laser pulse co-propagating through a wiggler at the ALS produces significant modulation of the electron energies within a short ~100 fs slice of the electron bunch. Subsequent propagation of the energy-modulated bunch around the storage ring results in an appearance of a local temporal modulation of the electron density (micro-bunching) due to the dispersion of electron trajectories. The temporal width of this perturbation evolves as the electron bunch propagates around the ring. The shortest modulation, ~50 microns, appears in the ALS sector immediately following the wiggler magnet, and stretches to ~ 500 microns following propagation over 2/3 of a storage ring orbit. The modulated electron bunch emits single-cycle pulses of temporally and spatially coherent infrared light which are automatically synchronized to the laser pulses. The intensity and spectra of the infrared light were measured in two locations in the ring indicated above and were found to be in good agreement with analytical calculations. Ultra-short pulses of coherent infrared radiation are presently used for a fine tuning the laser ? electron beam interaction for generating femtosecond x-ray pulses.
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THPKF082 | The Completion of SPEAR 3 | electron, linac, laser, insertion | 2448 | ||||||
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On December 15, 2003, 8 1/2 months after the last electrons circulated in the old SPEAR2 storage ring and 5 days after the beginning of commissioning, the first electrons were accumulated in the completely new SPEAR3 ring. The rapid installation and commissioning is a testimony to the SPEAR3 project staff and collaborators who have built an excellent machine and equipped it with powerful and accessible machine modeling and control programs. The final year of component fabrication, system implementation and testing, the 7-month installation period leading up to the beginning of commissioning, and lessons learned are described.
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THPKF084 | Emerging Concepts, Technologies and Opportunities for Mezzo-scale Terahertz and Infrared Facilities | electron, radiation, linac, laser | 2451 | ||||||
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Recent advances in particle beam, laser and radiofrequency technologies, combined with innovative concepts and techniques such as energy recovery, coherent synchrotron radiation-induced bunching, laser-particle beam scattering, ultrashort pulse slicing, cw high current and brightness phtoinjectors, ultrafast laser switching and compact engineered end products have opened up new opportunities and vistas in terahertz/infrared radiation sources not available before. Such sources would complement the high energy short wavelength x-ray sources in that they will allow us to probe collective processes and their ?function? in complex systems and materials, in a fashion complementary to probing structure via x-rays. We will outline and give examples of both the scientific reach of such radiation sources as well as examples of a few conceived facilities and techniques worldwide spanning a diversity of spectral, coherence, brightness and application ranges in the long wavelength. Such facilities fall in the category of mezzo-scale facilities, bracketed by table top lasers on one hand and large scale synchrotron radiation sources on the other and offer very unique and directed advances in a few key areas in life, materials, imaging, instrumentation and communication sciences.
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THPKF088 | NSLS II: A Future Source for the NSLS | radiation, linac, laser, insertion | 2454 | ||||||
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The National Synchrotron Light Source at BNL was the first dedicated light source facility and has now operated for more than 20 years. During this time, the user community has grown to more than 2400 users annually. To insure that this vibrant user community has access to the highest quality photon beams, the NSLS is pursuing the design of a new ultrahigh brightness (~ 1E21) electron storage ring, tailored to the 0.3-20 keV photon energy range. We present our preliminary design and review the critical accelerator physics design issues.
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THPLT003 | Vibrating Wire Scanner Parameters Optimization | radiation, linac, laser, insertion | 2457 | ||||||
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The idea to use the metallic vibrating wire as a scanner of particles beams was experimentally confirmed [1, 2] and showed unprecedented sensibility and a huge dynamic rage of the output signal. In this work the response time of the system is estimated on the base of the dynamic model of heat transfer through the wire. A comparison of different materials of the wire is presented and the most suitable materials for different tasks are suggested. The dielectric materials are considered as possible materials of the wire, use of which allows to eliminate the electromagnetic induction from high current beams during the scanning of beam halo. The results of scanning of the iron ion beam of the mass spectrometer are presented. 1. Arutunian S.G., Avetisyan A.E., Dobrovolski N.M., Mailian M.R., Vasiniuk I.E, Wittenburg K., Reetz R., Problems of Installation of Vibrating Wire Scanners into Accelerator Vacuum Chamber. - Proc. 8-th Europ. Part. Accel. Conf. (3-7 June 2002, Paris, France), pp. 1837-1839. 2. Arutunian S.G., Dobrovolski N.M., Mailian M.R., Vasiniuk I.E., Vibrating wire scanner: first experimental results on the injector beam of Yerevan synchrotron.- Phys. Rev. Special Topics. - Accelerators and Beams, 2003, v. 6, 042801.
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THPLT004 | Toroidal Cavity Loaded with an Electron Beam | linac, laser, insertion, target | 2460 | ||||||
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Three problems have been considered in this paper: the development of Maxwell's equations strict solution method to define the electromagnetic own values and own functions of the toroidal cavity; the radiation of the charged bunch rotating along the average radius, and, at last, the consideration of the case of a toroid filled with dielectric medium. The peculiarities of this radiation have been investigated as well. We suppose to consider the case when toroid is filled with plasma like a disperse medium.
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THPLT005 | Ultra-high Frequency Scanning Cavities for Non-relativistic Electron Beam | linac, laser, insertion, target | 2463 | ||||||
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The different scanning schemes based on the RF cavities for non-relativistic electron beam are examined. Optimization criteria for various types of cavities were developed. A complete picture of the beamscanning at a given point of interest is obtained.
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THPLT006 | A Comparison of COSY DA Maps with Analytic Formulae for Orbit Functions of a Non-scaling FFAG Accelerator | linac, laser, insertion, target | 2466 | ||||||
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Fixed Field Alternating Gradient (FFAG) magnetic lattices with fixed, possibly high, radio-frequency proposed for muon acceleration have unusual requirements: relative momentum swing dp/p of ± 30% and relative spread of revolution frequencies < 10-3. It is not evident whether the existing accelerator optical design codes are sufficiently accurate for such a large momentum range. Analytic expressions for orbit displacements, tunes and path length have been derived for thick-element models of doublet, F0D0 and FDF triplet lattices; it is this paper's purpose to compare these with values computed by SYNCH and COSY, and truncated Taylor maps constructed by Lie algebra. The mutual agreement of results from independent sources will serve to validate them all. A mathematical necessity is that one at least of the magnets be of the combined-function type, and with entrance and exit faces disposed in a sector layout. It is sufficient to consider the triplet case because in the limit that the two F quadrupoles are combined, the cell reduces to the simpler F0D0. We use as our example a "nonscaling" FFAG ring proposed for accelerations of muons over the momentum range 10-20 GeV/c.
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THPLT007 | New Beam Profile Monitor Based on GEM Detector for the AD Transfer and Experimental Lines | antiproton, linac, laser, insertion | 2469 | ||||||
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Many multi-wire proportional chambers, (MWPC's), are installed on the CERN Antiproton Decelerator (AD) transfer and experimental lines. They are used for the steering and profile measurement of the low energy antiproton beam that is extracted at the energy of 5.3 MeV from the AD machine. At this very low energy, the standard MWPC's are not only destructive for the beam but also perturb strongly the 2D profile measurement. These chambers are also based on technology that is outdated and in recent years have shown to be fragile and expensive to repair. For these reasons a new, low cost profile monitor, based on a Gas Electron Multiplier (GEM) detector is under development as a possible replacement of the MWPC's. This new profile monitor will enable high precision, true 2D profile measurements of the low energy antiproton beam. In this paper, we present the modification of the standard GEM detector required by our specific application and the first results of the profile monitor with antiproton beams.
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THPLT008 | A Beam Condition Monitor for the Experimental Areas of the LHC | antiproton, linac, laser, insertion | 2472 | ||||||
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The CERN Large Hadron Collider (LHC) will store 2808 bunches per colliding beam, with each bunch consisting of 1·1011 protons at an energy of 7 TeV. If there is a failure in an element of the accelerator, the resulting beam losses could cause damage not only to the machine but also to the experiments. A Beam Condition Monitor (BCM) is foreseen to monitor fast increments of fluence rate near the interaction point and, if necessary, to generate an abort signal to the LHC accelerator control to dump the beams. The system is being developed initially for the CMS experiment, but is sufficiently general to find potential applications elsewhere. Due to its high radiation hardness, CVD diamond was chosen for investigation as the BCM sensor. Various samples of CVD diamond have been characterised extensively with both a Sr-90 source and in a high intensity testbeam in order to assess the capabilities of such sensors and to study whether this detector technology is suitable for a BCM system. A selection of results from these investigations is presented.
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THPLT009 | Comparative Transverse Distribution Measurements between the New SPS Rest Gas Ionisation Monitor and the Wire Scanner Monitors. | antiproton, linac, laser, insertion | 2475 | ||||||
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During the past two years, a new Ionization Profile Monitor was installed and tested in the CERN SPS. In parallel modifications were made on various wire scanner monitors. The aim is to develop instruments performing reliable measurements of transverse beam distributions in the SPS and in the LHC, in order to control the stringent emittance preservation requirements. Measurements made with the two types of monitors were performed under various conditions of LHC type beams, ranging from a pilot bunch up to beams having in the SPS nominal distributions in bunch number, intensity and energy for injection into the LHC. The data provided by the two types of instruments are compared. In the case of discrepancies, an analysis of the possible reasons is made. The cures implemented and the improvements foreseen are discussed.
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THPLT010 | Limiting High Frequency Longitudinal Impedance of an Inductive Pick-up by a Thin Metallic Layer | antiproton, laser, insertion, target | 2478 | ||||||
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An Inductive Pick-Up (IPU) was developed to measure the position and current of an electron beam of the CTF3 Drive Beam Linac. The pick-up construction is similar to a wall current monitor, but the pick-up inner wall is divided into 8 electrodes, each of which forms the primary winding of a toroidal transformer. The beam image current component flowing along each electrode is transformed to a secondary winding, connected to an output. The continuity of the vacuum chamber is taken care of by a ceramic insertion surrounded by the electrodes. The insertion is titanium coated on the inside and the end-to-end resistance of the layer is chosen in such a way that within the IPU bandwidth the image current flows over the electrodes. For higher frequencies the current is conducted by the coating to limit the longitudinal impedance of the device in the GHz range. This paper describes a simple electric network model, which was used to simulate the influence of the coating and to optimize its resistance. The model is built from sections of ideal transmission lines and resistors and is suitable for SPICE simulations. Results of measurements and simulations are compared.
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THPLT011 | Longitudinal Loss Distribution along the LHC | antiproton, laser, target, lattice | 2481 | ||||||
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For the design and calibration of the LHC beam loss monitoring system it is essential to have good predictions of the expected longitudinal loss distributions. For this purpose a complete and detailed aperture model of one LHC sector was compiled and included with the tracking code MAD. The positions of all beam pipe bellows are included in the model as well. Therefore, it allows investigating the loss pattern due to misalignment effects, in addition to steady beam losses (beam halo, beam-beam and beam-rest gas interactions) and orbit errors. Loss maps of halo particles originating from the betatron cleaning insertion have been created for proton and ion beams. The distribution of particle losses along the beam pipe is folded with the result of GEANT simulations of the shower development through the magnets and cold masses. They link the loss of a beam particle on the aperture to particle fluencies outside of the cryostats, where the beam loss monitors will be installed. These simulations determine the positioning of the loss monitors, the longitudinal distance one detector has to cover to achieve the required resolution as well as all calibration factors for the individual detectors. The model also serves to identify hot spots, which can limit the performance of the LHC.
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THPLT012 | Design of the Beam Loss Monitoring System for the LHC Ring | antiproton, laser, target, lattice | 2484 | ||||||
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The beam loss monitoring (BLM) system of the LHC is one of the most critical elements for the protection of the LHC. It must prevent the super conducting magnets from quenches and the machine components from damages, caused by beam losses. It helps in the identification of the loss mechanism by measuring the loss pattern. Special detectors will be used for the setup and control of the collimators. Furthermore, it will be an important tool during machine setup and studies. The specification requirements of the BLM system include a very high reliability
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THPLT035 | Development of a 3D-Gun-Code based on a Charge Conserving Algorithm | antiproton, ion, positron, electron | 2553 | ||||||
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Recent efforts in the development of electron sources are aiming at high intensity electron beams, beyond the limitations posed by space-charge effects in conventional guns. Field emitter arrays, multi-beam and sheet-beam guns are a few examples of emerging technology, which require an accurate characterization of the limiting current in complicated 3D-geometry. The newly developed gun code at the Technische Universität Darmstadt, implements a novel approach to the numerical simulation of space-charge-limited electron emission, which is based on the local conservation of charge for arbitrary cathode surfaces. It is shown that, imposing exact charge conservation using the CAD-data of the geometry eliminates the spurious oscillations in the charge density, which typically arise when the piecewise-planar diode approximation is applied in the simulation. The accuracy of this approach is demonstrated in the validation study of a spherical diode and in the large-scale simulation of a Traveling Wave Tube amplifier.
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THPLT036 | New Discretization Scheme for Wake Field Computation in Cylindrically Symmetric Structures | antiproton, ion, positron, electron | 2556 | ||||||
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Collective effects due to wake fields are a limiting factor in almost every new front line accelerator. Since the early 80's computer codes such as TBCI and MAFIA have been developed for computing wake fields in realistic accelerator structures. With the advent of linear collider studies and small wavelength FEL projects these codes had to face a severe limitation. For the very short bunches in these new accelerators combined with the need for an analysis of very long sections the discrete dispersion became a serious drawback. This effect of having only discrete field values rather than continous ones can be overcome by special algorithms such as semi-implicit integrators as used e.g. in the wake field code ECHO. In this paper we present a new explicit approach which combines the advantage of explicit algorithms (fast) with the absence of dispersion in beam direction.
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THPLT037 | Investigation of Numerical Noise in PIC-Codes | antiproton, ion, positron, electron | 2559 | ||||||
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For a detailed analysis of the dynamics of space charge dominated beams a combination of Particle-in-Cell methods with efficient FDTD schemes is widely used. Besides the calculation of the forces acting on the particles the interaction of the beam itself with the surrounding geometries is taken into account. A drawback of this method is its sensitivity to numerical noise in the spectral range nearby the grid cutoff frequency. In this paper we will present results of detailed studies of the impact of the bunch shape on the level of the numerical noise. Furthermore an a priori scheme for efficient noise suppression is derived which does not affect the FDTD update algorithm.
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THPLT038 | The Synchrotron Radiation Interferometer using Visble Light at DELTA | antiproton, ion, positron, synchrotron | 2562 | ||||||
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Synchrotron radiation sources such as DELTA, the Dortmund electron accelerator, rely on a monitoring system to measure the beam size and emittance with sufficient resolution. The resolution limits of the different types of optical synchrotron light monitors at DELTA have been investigated. The minimum measurable beam size with the standard synchrotron light monitor using visible light at DELTA is appr. 80 μm. Due to this limitation an interferometer was built up and tested using the same beamline in the visible range. A minimum measurable beam size of appr. 8 μm could be obtained, which gives an increased resolution of one order of magnitude with the new system.
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THPLT039 | SVD Based Orbit Correction Incorporating Corrector Limitations at DELTA | antiproton, ion, positron, synchrotron | 2565 | ||||||
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Singular Value Decompostion (SVD) of the orbit response matrix has become an invaluable tool for orbit correction at storage rings worldwide. SVD based orbit correction has now been realised at DELTA, a 1.5 GeV electron storage ring. However, due to special orbit demands at DELTA and possibly by magnetic imperfections within the storage ring, we frequently have to face corrector limitations during the process of orbit correction. This work focuses on presenting an analytic algorithm on how to treat these limitations when seeking for an optimal SVD based orbit correction. In contrast to previously published methods, this approach is fairly easy to implement and does not afford an numerical solver. Concepts and results will be presented.
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THPLT041 | Beam Test Stand of the RFQ-drifttube-combination for the Therapy Center in Heidelberg | antiproton, positron, synchrotron, lattice | 2568 | ||||||
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A beam test stand for the Heidelberg medicine RFQ has been installed at the IAP in Frankfurt. The installation consists of a 8 keV/u H+ duoplasmatron ion source, the 400 keV/u RFQ itself and several diagnostic elements comprising a slit-grid emittance measurement system for scanning the transverse beam profile and a bending magnet for measuring the longitudinal beam properties. The test installation will be described in detail, first measurements will be presented and compared to corresponding beam dynamic simulations.
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THPLT042 | Automated Orbit Control for the HERA ep Collider | antiproton, positron, synchrotron, lattice | 2571 | ||||||
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Successful operation of the HERA electron-proton collider requires maintaining stable orbits during the typically 12 hour luminosity runs, as well as during the fill and acceleration procedures. The primary sources of orbit errors for the electron ring are the interaction region magnets, whose support structures are integrated with the experimental detectors and susceptible to thermal and magnetic effects. The orbit correction algorithms are designed to correct these effects locally, while operating with somewhat reduced sensitivity on error sources in the rest of the ring. We describe the correction system and our operating experience.
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THPLT043 | Development of a New Orbit Measurement System | antiproton, positron, synchrotron, lattice | 2574 | ||||||
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Since DORIS III became a dedicated source for synchrotron radiation in 1993, the demands of the synchrotron-light-users concerning the beam position stability have permanently increased.In order to improve this stability, different measures have been adopted, all with success. The vacuum chambers have been renewed, since they were the source of quadrupole movement, which caused strong horizontal orbit distortion. In 2003 a new orbit position control was implemented, based on the ?Singular Value Decomposition? method. The position information comes from synchrotron light monitors, installed in the beam-lines, and from the orbit measurement system, which operates with a maximal measurement rate of 5Hz and a spatial resolution not less than 20μm. To satisfy the requirements for beam-position stability, the orbit measurement system has been further developed. The test stage is nearly finished and the new system will be installed soon. The orbit measurement rate will exceed 250Hz und the spatial resolution will be less than 2μm. In addition beam oscillations of up to 20Hz can be damped.
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THPLT046 | The Synchrotron Radiation Beamline at TTF2 | antiproton, positron, radiation, scattering | 2583 | ||||||
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The VUV-FEL at DESY, Hamburg, will require novel techniques to characterize the longitudinal charge distribution of the electron bunches that drive the free-electron laser. Conventional methods are inadequate at the short bunch lengths that will be obtained. One technique under study uses coherent far-infrared radiation to reconstruct the bunch shape through Fourier analysis of the spectrum. In a first step, a beam line to guide both far-infrared (50-1000 um) and optical synchrotron radiation from one of the bunch compressor magnets of the linear accelerator to a diagnostic station outside of the controlled area is currently under construction. It will also allow a comparison between streak camera and far-infrared measurements for features on length scales above some 100 um (the streak camera resolution). Later, infrared techniques extending to shorter wavelengths, i.e. to shorter bunch lengths, will also be used further downstream the accelerator, employing synchrotron, transition and undulator radiation. The beam line design, measurement principle and first measurements will be presented.
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THPLT047 | Beam Position Monitor Development for the IThemba LABS Cyclotron Beamlines | antiproton, positron, radiation, scattering | 2586 | ||||||
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In cooperation of iThemba LABS (South Africa) and Forschungszentrum Juelich the specification of a sensitive tunable rf narrowband beam position monitor system for cyclotron beamlines has been elaborated. iThemba LABS developed and manufactured the four section stripline monitor chamber. The monitor electronics were developed in the Forschungszentrum Juelich-IKP. The electronics consisting of an RF signal processing module (BPM-RF) and a data acquisition and control module (BPM-DAQ) sequentially processes and measures the monitor signals and deliver via serial network calculated horizontal and vertical beam position data. First measurements with cyclotron beam has been performed in the iThemba LABS in November 2003. Changed beam position due to changing different cyclotron parameters could be studied with high accuracy. The resolution of the beam position measurement was better than 0.1 mm with beam currents down to 0.0005 mA.
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THPLT048 | Progress in 3D Space-charge Calculations in the GPT Code | antiproton, positron, radiation, scattering | 2589 | ||||||
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The mesh-based 3D space-charge routine in the GPT (General Particle Tracer, Pulsar Physics) code scales linearly with the number of particles in terms of CPU time and allows a million particles to be tracked on a normal PC. The crucial ingredient of the routine is a non-equidistant multi-grid Poisson solver to calculate the electrostatic potential in the rest frame of the bunch. The solver has been optimized for very high and very low aspect ratio bunches present in state-of-the-art high-brightness electron accelerators. In this paper, we explore the efficiency and accuracy of the calculations as function of meshing strategy and boundary conditions.
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THPLT050 | End to End Simulations of the RX2 Beam Transport | antiproton, positron, radiation, scattering | 2592 | ||||||
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RX2 is a project aiming to produce a high flux of X-rays for radiography purpose. We proposed an RF linac using a DC photo-injector producing 20 bunches with 100nC each at 352 MHz. The beam is then injected in 4 RF superconducting cavities and accelerated to 40 MeV. It is then focused on a target producing X-rays. Here is presented the design, the specificities, and the beam simulations from the cathode to the target by coupling 2 multiparticle codes : PARMELA and PARTRAN.
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THPLT051 | End to End Multiparticle Simulations of the AIRIX Linac | antiproton, positron, radiation, scattering | 2595 | ||||||
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AIRIX is a working 3 kA, 20 MeV induction accelerator. It has been designed with an enveloppe code : ENV. A new set of multiparticle codes (PBGUNS, MAGIC, PARMELA and PARTRAN) has been used recently to simulate the beam transport with an higher accuracy especially taking into account the field non-linearities. A dedicated space-charge routine has been written. The calculation results have been compared to experimental measurements.
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THPLT077 | MPI Parallel Computation of Wake Fields by Using Time Domain Boundary Element Method | laser, antiproton, gun, cathode | 2670 | ||||||
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This paper presents wake field and wake potential calculation by using the Time Domain Boundary Element Method (TDBEM) on the MPI parallel computation system. The TDBEM is based on the electric field integral equation (EFIE) and the electric field integral equation (MFIE) in time domain. In wake field simulation, an important advantage of these equations is that electromagnetic fields in an accelerator cavity are explicitly expressed as a sum of charged particle self-fields and wake fields in time domain. On the other hand, the TDBEM has serious difficulties in practical numerical simulation, such as numerical instabilities, huge memory requirements, and heavy calculation cost. However, recent remarkable progress of computer performance makes the TDBEM possible to be used in practical simulations. According to these backgrounds, we apply the TDBEM to wake field simulation in the MPI parallel computer system. Simulation results are compared with that of a conventional method, the Finite Integration Techniques (FIT), and good agreements are shown.
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THPLT078 | Construction of FFAG Accelerators in KURRI for ADS Study | laser, antiproton, gun, booster | 2673 | ||||||
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KART (Kumatori Accelerator driven Reactor Test) project has started at Kyoto University Research Reactor Institute (KURRI) from the fiscal year of 2002. The purpose of this project is to demonstrate the basic feasibility of ADS, studying the effect of incident neutron energy on the effective multiplication factor of the subcritical nuclear fuel system. We are now constructing a proton FFAG accelerator complex as a neutron production driver for this project. Our accelerator complex consists of a 2.5 MeV FFAG betatron as an injector and 20 MeV and 150 MeV FFAG synchrotrons as a booster and a main ring, respectively. Our FFAG betatron is a spiral sector type. Both booster and main rings are radial sector type FFAG synchrotrons, but different in the production of required magnetic field with a certain magnetic field index. The distribution of magnetic field is determined by the shaped pole-face in the main ring while the magnetic field is realized by use of trim coils in the booster ring. This FFAG complex will be combined with our Kyoto University Critical Assembly (KUCA) in KURRI by the end of March 2006 and the experiments will begin as soon as the whole system is ready.
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