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| MOPLT037 | Simulation of Transient Beam-feedback Interaction with Application to the Extraction of the CNGS Beam from the SPS | lepton, wiggler, 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, wiggler, 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, wiggler, 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, wiggler, 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, wiggler, 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, wiggler, 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, wiggler, 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, wiggler, 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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| MOPLT107 | Nanosecond-timescale Intra-bunch-train Feedback for the Linear Collider: Results of the FONT2 Run | wiggler, 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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| THPLT016 | LHC Orbit Feedback Tests at the SPS | antiproton, laser, target, lattice | 2496 | ||
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The real-time orbit feedback system foreseen for the LHC will be an essential component for reliable and safe machine operation. A test setup including a number of beam position monitors equipped with the LHC acquisition and readout system have been installed in the SPS ring to perform prototyping work on such an orbit feedback. A closed loop digital feedback was implemented and tested with LHC beams on the SPS during the 2003 machine run. The feedback loop was tested successfully at up to 100 Hz. The performance of the feedback loop and of its constituents will be described.
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| THPLT017 | Review and Comparison of Simulation Codes Modeling Electron-Cloud Build Up and Instabilities | antiproton, laser, target, lattice | 2499 | ||
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Several computer codes written at various laboratories are employed for modelling the generation and the consequences of an electron cloud. We review the most popular of these programs, which simulate either the build of an electron cloud or the instabilities it produces, and we compare simulation results for identical, or similar, input parameters obtained from the various codes.
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| THPLT018 | Electron Beam Dynamics Simulations for the Low Emittance Gun | antiproton, gun, electron, target | 2502 | ||
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We report on theoretical simulation performed for the development of a high brightness, field emitter based electron gun suitable for an Angstrom wavelength free electron laser\cite{LEG}. First simulations have been done with available codes in 2 1/2D and 3D for basic gun configurations showing the global and local (due to the granularity of the emitter array) effects on the emittance dilution.Design and construction started on a test setup consisting of a 100 keV electron gun with solenoidal focusing and a diagnostics module. In addition to solenoid focussing, anode shaping will be investigated in order to compensate for non-linear fields leading to space charge blow-up. For advanced simulations of field emitter based guns allowing to resolve individual emitters and to capture the influence of mechanical imperfections, a massive parallel code for 3D particle-in-cell simulations is in development. The electromagnetic field solver is fully functional and the particle tracker has been completed in its basic structures.
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| THPLT020 | The DSP-based Betatron Tune Feedback of the Ramped 1.5 GeV Electron Storage Ring BoDo | antiproton, gun, electron, target | 2508 | ||
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The ramped storage ring BoDo is the full energy injector of the 1.5 GeV synchrotron light source DELTA. All ramped booster magnet power supplies, RF power and beam diagnostics of BoDo are handled by a distributed VME-based DSP (digital signal processor) multiprocessing system developed at DELTA. The VME DSP boards of this system are interconnected by DeltaNet, a novel reflective memory ring network. DeltaNet transmits the measurement data from each DSP board to all other boards in real-time via fibre optic links. The generic hardware and software architecture of the system allows the implementation of different kinds of global real-time feedbacks with correction rates in the range from some 100 Hz to some 10 kHz. This paper presents architecture and performance of a real-time betatron tune feedback that was implemented with the DSP system. The betatron tune is measured and corrected in both planes at a rate of typically 700 Hz for arbitrary beam optics and energy ramps of BoDo. In combination with the global Bodo orbit feedback, the tune feedback increases the performance of Bodo both as an injector and as a testbed for machine studies and newly developed accelerator components.
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| THPLT021 | A DSP-Based Fast Orbit Feedback System for the Synchrotron Light Source DELTA | antiproton, gun, electron, target | 2511 | ||
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A DSP-based Fast Orbit Feedback (FOFB) system has been designed for the synchrotron light facility DELTA. DELTA consists of a 60 MeV linac, the ramped storage ring BoDo as full-energy injector and the 1.5 GeV storage ring Delta. BoDo and Delta have the same dipole, quadrupole and corrector magnet design, the same beam pipe design and the same BPM RF frontends, therefore BoDo was used as a testbed for the newly developed FOFB hardware and software. Using the fast corrector magnet power supplies of BoDo, the FOFB could damp orbit perturbations up to 90 Hz. The envisaged future use of the FOFB for the Delta storage ring will require either the partial or full replacement of the present slow (1 Hz bandwidth) Delta corrector power supplies, or additional fast power supplies with dedicated FOFB corrector magnets. A first test of the FOFB in Delta for local orbit stabilization at one beamline is in preparation. This paper presents the results of a successful test of the FOFB at BoDo, where it achieves a correction rate of 4 kHz for a global SVD-based feedback in both planes. The FOFB is based on the "DeltaDSP" VMEbus DSP boards that are also used for the BoDo betatron tune feedback.
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| THPLT053 | Fast Orbit Feedback Developments at ELETTRA | vacuum, antiproton, positron, radiation | 2601 | ||
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A number of fast local orbit feedback stations are being sequentially installed at ELETTRA to improve the stability of the electron beam at the Insertion Device source points. They rely on Beam Position Monitors equipped with digital detector electronics that provides high precision and readout rate. The local feedback stations will be integrated in a fast global orbit feedback system, which is the goal of the ongoing developments. The performance and the operational experience gained with the local feedback systems are presented together with the planned road map towards the global system.
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| THPLT054 | Emittance Diluition due to 3D Perturbations in RF Photoinjectors. | vacuum, antiproton, positron, radiation | 2604 | ||
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The predictions from different simulation codes are compared to investigate the effects of non axis-symmetric conditions, fluctuations in cathode's quantum efficiency and other sources of dishomogeneities in the performances of a typical RF photoinjector. The layout includes a RF gun and a focusing solenoid in a configuration aimed at minimizing the emittance growth due to space charge effects.
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| THPLT055 | Longitudinal Phase Space Characterization of the CTF3 Beam with the RF Deflector | vacuum, antiproton, positron, radiation | 2607 | ||
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The characterization of the longitudinal phase space of the CTF3 beam is an important item for tuning all machine parameters and increase the 30 GHz power production. By means of an RF deflector and a dispersive system the longitudinal phase space can be completely characterized. In this paper we present the simulation of the measurement and the mechanical layout of the full system.
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| THPLT056 | Horizontal Instability and Feedback Performance in DAFNE e+ Ring | vacuum, antiproton, radiation, scattering | 2610 | ||
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In DAFNE, after the 2003 shutdown for the installation of FINUDA, a strong horizontal multibunch instability was found to limit the positron beam current at the level of ~450 mA. We have performed transverse grow-damp measurements in order to estimate the instability growth rates as well as the feedback damping rates for each bunch at different beam currents and to evaluate the tune shift along the bunch train. In particular, a strong dependence of oscillation amplitudes on the relative position of the bunch in the train has been observed. In this paper we describe the setup for multibunch oscillation amplitude recording, discuss the transverse feedback performance and summarize some observations on the transverse instability. The feedback rises the threshold by about a factor of two, depending on the machine configuration.
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| THPLT057 | An RF Deflector Design for 6d Phase Space Characterization of the Sparc Beam | vacuum, antiproton, radiation, scattering | 2613 | ||
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The characterization of the longitudinal and transverse phase space of the beam provided by the SPARC photoinjector is a crucial point to establish the performance quality of the photoinjector itself. By means of an RF deflector and a dispersive system, the six dimensional beam phase space can be analyzed. A five cell SW aluminum prototype of the SPARC RF deflector has been realized and tested. We report in this paper the design issues together with the RF measurement results. The simulation results of the 6D phase space reconstruction of the SPARC beam are also presented.
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| THPLT058 | Commissioning of the OTR Beam Profile Monitor System at TTF/VUV-FEL Injector | vacuum, antiproton, scattering, cyclotron | 2616 | ||
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The TESLA Test Facility (TTF) linac at DESY is being extended to an energy of 1 GeV to drive a new Free Electron Laser facility (VUV-FEL)with wavelengths between 100 nm and 6 nm.Beam profile monitors based on optical transition radiation (OTR) are one of the most important electron beam diagnostics tools. The OTR imaging system is designed to measure the transverse beam size and shape with a resolution down to 10 um. The images are digitized by CCD cameras. A network structure allows a simpler topology to connect the large number of cameras (24).This paper considers the commissioning of the OTR beam profile monitors during the first running period of the injector in spring 2004.
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| THPLT059 | Design Study of a Movable Emittance Meter Device for the SPARC Photoinjector | vacuum, antiproton, emittance, scattering | 2619 | ||
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Preliminary studies of the SPARC rf gun are planned to obtain an accurate analysis and optimization of the emittance compensation scheme, measuring the beam emittance evolution downstream the RF gun with an appropriate diagnostic system. Since with a space charge dominated beam the use of the quad-scan method is not possible a 1D pepper-pot method will be used. A mask with narrow slits will be mounted on a movable support, spanning a 1.5 m meters region to measure the emittance in several positions and reconstruct its behavior in the post gun section. Numerical simulations of the measurement process, mainly based on PARMELA and TREDI, are used to estimate the achievable accuracy and to optimize the experimental setup. Wake field effects induced by the beam propagation through the long bellows have been also investigated with HOMDYN. Based on these simulations the design of the apparatus, called emittance-meter, has been realized and is under construction at LNF.
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| THPLT060 | An Automatic Beam Characterization Instrument for Proton Therapy Applications | vacuum, antiproton, emittance, scattering | 2622 | ||
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The characterization in the transverse plane of the beam is a fundamental step in the design of a proton therapy facility. In this paper we will describe an automatic system able to measure the transverse profiles of the proton beam used in the Catana facility at LNS-Catania. The system has been designed as an autonomous equipment able to acquire optical images of the beam (after an interaction with a converter) and to elaborate them to extract the relevant parameters. The equipment may be interfaced to the rest of the control system of the facility and to the operator interface to provide high level control and monitoring tools. Operational experience will be discussed and the results so far obtained will be outlined.
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| THPLT084 | Test Result of Slow Global Orbit Feedback using MATLAB at PLS | antiproton, emittance, booster, cyclotron | 2691 | ||
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A slow global orbit feedback using MATLAB has been tested to control the slow orbit movement for the PLS. The feedback program uses MATLAB tools such as matrix algebra, mathematical functions, and graphic display, and uses the SVD (singular value decomposition) method. The PLS uses 70 corrector magnets with the maximum angle of 2-mrad for each plane among which 11 use the 16-bit DAC power supplies for the insertion device orbit control and others the 12-bit corrector power supplies with the minimum step of 1-micro-rad, and thus the orbit feedback is not acceptable to beamline users. For the best performance of the feedback, the major hardware components have been upgraded: the replacement of 12-bit BPMs with 16-bit was completed, and the upgrade of corrector power supplies from DAC 12-bit to 18-bit or higher will be completed soon. In this paper, the orbit feedback test result using the current corrector power supplies is presented and the upgrade plan of orbit feedback is described.
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| THPLT085 | Reengineering and Refactoring Large-scale Scientific Programs with the Unified Process: A Case Study with OSIRIS PIC Program | antiproton, emittance, booster, cyclotron | 2694 | ||
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As science and engineering problems get more complex, programs which help modelling complicated problems larger and more sophisticated. This trend makes us recognize the importance of well-established engineering disciplines not only in designing large-scale scientific programs for special purposes in appropriate development time but also in importing the programs from other research group and refactor it for conveniences and more advanced applications. OSIRIS is a large-scale PIC code which was developed at UCLA for modelling of laser-plasma interactions. OSIRIS was reengineered and documented in UML by our group and ported to Linux cluster machine of 8 nodes. We report our current status of developing the extended version of OSIRIS, which was named as OSIRIS-X, and how a large-scale scientific programs can be enhanced efficiently with the Unified Process. Some guidelines in designing and refactoring large-scale scientific codes are presented and discussed. A common architecture model of numerically intensive programs for large-scale computing is suggested , and it is discussed how we can use it for rapid development and prototyping of scientific programs. We also discuss future challenges and prospects in OSIRIS-X development.
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| THPLT086 | High Temporal Resolution, Single-shot Electron Bunch-length Measurements | electron, antiproton, emittance, booster | 2697 | ||
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A new technique, combining the electro-optic detection of the Coulomb field of an electron bunch and the single-shot cross-correlation of optical pulses, is used to provide single-shot measurements of the shape and length of sub-picosecond electron bunches. As in our previous technique [I. Wilke et al., Phys. Rev. Lett. 88, 124801 (2002)], the electric field of the electron beam is encoded electro-optically on an optical pulse. Our earlier measurements, which involved encoding the time profile of the electron bunch on the spectrum of the optical pulse, showed electric field profiles with a FWHM of the order of 1.7 ps. The new method offers a much better time resolution since it avoids the significant measurement artifacts that can arise in our previous (spectral encoding technique due to the coupling between the temporal envelope and spectral content of the optical pulse. The cross-correlation technique has been applied to the measurement of electron bunches in FELIX, showing single bunches of around 500fs FWHM. The resolution is limited primarily by the electro-optic crystal thickness and the relatively low energy of the electrons (50 MeV).
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| THPLT089 | MATLAB Based TPSA Toolbox for the Particle Mapping Through Three-dimensional Magnetic Fields | electron, antiproton, emittance, booster | 2700 | ||
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Based on the object-oriented programming of MATLAB, a truncated power series algebra (TPSA) toolbox has been developed. The TPSA toolbox as a differential algebra has been applied to realize the algorithm of particle mapping through three-dimensional magnetic field configurations. The capability of symbolic calculation by using this MATLAB-based TPSA toolbox can be used for the theoretical simulation and modeling in accelerator physics. Associated with the use of MATLAB in the control of machines, one can derive the real machine with a virtual machine model built in MATLAB. In this paper, the method of symplectic mapping of three-dimensional magnetic fields is introduced and the structure of TPSA toolbox is presented. Applications of TPSA toolbox in the symplectic mapping of three-dimensional magnetic fields are demonstrated as well.
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| THPLT090 | The Operating of Digital Beam Position Monitor in NSRRC | electron, antiproton, emittance, booster | 2703 | ||
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The digital beam position monitors are configured to operation system in the NSRRC now. This integration includes of multi-channel access, channel calibration, gain control, and parameter control to meet various operation condition, perform functionality and performance evaluation. The programmability nature of DBPM system is essential for multi-mode high precision beam position measurement. The system will support high performance beam position, turn-by-turn beam position, tune and other diagnostic measurements. Control system interface was implemented to support the operation of DBPM system. T various aspects will be discussed and presented in this report.
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| THPLT091 | The Synchrotron Radiation Monitor Upgradation in NSRRC | electron, antiproton, emittance, cyclotron | 2706 | ||
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Synchrotron radiation monitor in the storage has been operated for a long time. This system is upgrading to booster operation now. The basic system includes optics, digital image acquisition, image analysis, compressed image transportation and visualization tools at workstation. The linearity and dynamic of new is discussed for some beam physics study. This system is also supported to the booster by new camera and addition operation. The hardware configuration and software structure will be summarized in this report.
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| THPLT093 | Particle-in-cell Numerical Simulations of Particle Dynamics in Beams and ECR Sources | plasma, antiproton, emittance, ion | 2709 | ||
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A summary of recent development of physical and mathematical basements and the first version of computer code library based on the particle-in-cell method are presented. The code library is aimed for the three-dimensional (3D) simulation of the ECR plasma and ion production in the ECR ion source. The particle-in-cell (finite particle) method is one of the most powerful methods for the numerical simulation of multicomponent ECR plasma and electron-ion beams. This method allows studying the detailed characteristics of plasma, taking into account the distribution functions of particles (spatial, velocity and energy distributions), real self and external fields, particle-particle interactions and many other effects. This technique promises to provide very precise numerical simulations and optimizations of ECR ion sources. The first results of simulations of ECR source plasma are presented. It has been shown that a complete and adequate description of ECR plasma requires the full-scale 3D model and computer codes. This is out of frames of existed project and could be an aim of some addition investigations.
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| THPLT094 | Ordered Ion Beam in Storage Rings | plasma, ion, antiproton, emittance | 2712 | ||
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The using of crystalline ion beams can increase of the luminosity in the collider and in experiments with targets for investigation of rare radioactive isotopes. The ordered state of circulating ion beams was observed experimentally at several storage rings. In this report a new criteria of the beam orderliness are derived and verified with BETACOOL code with using molecular dynamics technique. The sudden reduction of momentum spread observed on a few rings is described with this code. The simulation shows a good agreement with the experimental results. The code has then been used to calculate characteristics of the ordered state of ion beams for ion rings which will have experimental programs for the study of crystalline beams. A new strategy of the cooling process is proposed which permits to increase the linear density of the ordered ion beam.
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| THPLT095 | Nuclotron Extracted Beam Spill Control | plasma, ion, antiproton, emittance | 2715 | ||
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The first experiments with the Nuclotron Beam Slow Extraction System (BES) were carried out in December 1999. After the BES commissioning, the development of the system was continued together with experiments on relativistic nuclear physics. To realize the constant-current-beam or the constant-time-length spill and to suppress the low frequency spill structure in the range up to several hundred hertz, a spill control subsystem was designed and put into operation. It consists of a feedback loop in parallel with a feed-forward control. In the feedback loop the extracted particle flux is measured with beam current monitor and is compared with the request flux. The resulting error signal is fed into a feedback controller. The controller is an analog unit in which integration, differentiation and gain can be adjusted separately. The output control signal is added to the extraction quadrupoles power supply pattern generated by the corresponding function generator. The beam spill control subsystem has been improved in stages since its commissioning in 2000. The beam spill duration of more than 10s and the beam spill uniformity of about 0.9 were achieved in recent Nuclotron runs.
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| THPLT099 | The Analysis of the Electron Beam Scanning Method for the Beam Profile Monitoring. | plasma, antiproton, emittance, cyclotron | 2718 | ||
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The method of the beam profile monitoring with scanning electron beam is analyzed. Simulation model of the ion/electron beam interaction is presented and some simulation results are shown. In the report the estimation of overall performance characteristics of this method such as sensitivity, spatial resolution, frequency bandwidth etc. are given.
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| THPLT100 | Development of a Permanent Magnet Residual Gas Profile Monitor With Fast Readout | plasma, antiproton, emittance, cyclotron | 2721 | ||
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The beam profile measurement at modern ion synchrotrons and storage rings require high timing performances on a turn-by-turn basis. From the other hand, high spatial resolutions are very desirable for cold beams. We are developing a residual gas monitor to cover the wide range of beam currents and transversal distributions of particles. It supplies the needed high-resolution and high-speed tools for beam profiling. The new residual gas monitor, will operate on secondary electrons whose trajectories are localized within 0.1 mm filaments. The required magnetic field of 100 mT will be excited by a permanent magnet. In the fast turn-by-turn mode the beam profile will be read out with a resolution of 1 mm by a 100-channel photodiode-amplifier-digitizer. The high resolution mode of 0.1 mm is provided by a CCD camera with upstream MCP-phosphor screen assembly. In this paper the first results of the photodiode-digitizer device testing, the compact mechanical design features and simulation results of the permanent magnet device are presented.
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| THPLT102 | Characteristics of Sealed-off Electron Gun with Wide Beam | plasma, gun, antiproton, emittance | 2724 | ||
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Compact sealed-off electron gun is a new promising type of devices. The gun generates wide beam of electrons with energy up to 200 keV and high peak power in 2-microsecond pulses. The beam is extracted to the atmosphere or a gas through the foil being uniformly distributed over the area of exposure. The gun contains the long ribbon cathode of oxide type, the electrodes for forming required distribution of the beam, the output window with 20-micron titanium foil, the high-voltage ceramic insulator, and the vacuum casing of rectangular shape. The gun is applied in the radiation technology system intended for the treatment of continuously moving tapes with 300 mm width. The gun design provides 10% uniformity of the radiation dose on the tape width.
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| THPLT141 | Operational Experience Integrating Slow and Fast Orbit Feedbacks at the ALS | plasma, gun, proton, polarization | 2783 | ||
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A fast global orbit feedback system has been implemented at the ALS and is being used during user operation since this year. The system has two main purposes. The first is to meet the demands of some users for even improved (submicron) short term orbit stability. The second is to enable the use of more sophisticated insertion device compensation schemes (e.g. tune, beta-beating, coupling) for fast moving insertion devices like elliptically polarizing undulators, without deteriorating the orbit stability. The experience of routine user operation with the fast orbit feedback will be presented, as well as the overall feedback performance and how the integration issues with the already existing slow orbit feedback were solved.
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| THPLT142 | A Laser-Based Longitudinal Density Monitor for the Large Hadron Collider | plasma, gun, proton, polarization | 2786 | ||
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We report on the development of an instrument for the measurement of the longitudinal beam profile in the Large Hadron Collider. The technique used, which has been successfully demonstrated at the Advanced Light Source, mixes the synchrotron radiation with the light from a mode-locked solid state laser oscillator in a non-linear crystal. The up-converted radiation is then detected with a photomultiplier and processed to extract, store and display the required information. A 40 MHz laser, phase-locked to the ring radiofrequency system, with a 50 ps pulse length, would be suitable for measuring the dynamics of the core of each of the LHC 2808 bunches in a time span much shorter then the synchrotron period. The same instrument could also monitor the evolution of the bunch tails, the presence of untrapped particles and their diffusion into nominally empty RF buckets ("ghost bunches") as required by the CERN specifications. We also specify the required characteristics of the diagnostic light port in the LHC where our instrument would be installed.
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* Presently at Lawrence Livermore National Laboratory. |
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| THPLT143 | Development of an Abort Gap Monitor for the Large Hadron Collider | plasma, gun, proton, polarization | 2789 | ||
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The Large Hadron Collider, presently under construction at CERN, requires a monitor of the parasitic charge in the 3.3 ?s long gap in the machine fill structure, referred to as the abort gap, which corresponds to the raise time of the abort kickers. Any circulating particle present in the abort gap at the time of the kickers firing is lost inside the ring, rather than in the beam dump, and can potentially damage a number of the LHC components. CERN specifications indicate a linear density of 6x106 protons over a 100 ns interval as the maximum charge safely allowed in the abort gap at 7 TeV. We present a study of an abort gap monitor, based on a photomultiplier with a gated microchannel plate, which would allow for detecting such low charge densities by monitoring the synchrotron radiation emitted in the superconducting undulator dedicated to the measurement of the longitudinal beam properties. We show results of beam test experiments at the Advanced Light Source using an Hamamatsu 5916U MCP-PMT which indicate that such an instrument has the required sensitivity to meet LHC specifications.
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| THPLT145 | Automated High-power Conditioning of Medical Accelerators | plasma, gun, proton, polarization | 2792 | ||
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Medical accelerators require arc-free operation. Due to high-field emission, arcing and outgasing can occur in high-power accelerators. Therefore, the accelerator?s inner surfaces have to be conditioned before its use at high gradient levels in Radiation Therapy machine. At Siemens, we have developed a techniqu·101 to automatically condition an accelerator waveguide structure by continually inspecting the accelerator running conditions (arcing and vacuum) and stepping up the pulse repetition frequency (PRF) and RF power until reaching maximum power rating. The program implemented also reads, displays, and archives the data it collects along the full process of conditioning.
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| THPLT146 | Beam Diagnostics of the Small Isochronous Ring | plasma, gun, proton, polarization | 2795 | ||
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The purpose of this paper is to describe the beam diagnostic systems in the Small Isochronous Ring (SIR) developed and built at the National Superconducting Cyclotron Laboratory (NSCL) at Michigan State University (MSU). SIR is a small-scale experiment that simulates the dynamics of intense beams in large accelerators. A 20 to 30 keV hydrogen or deuterium ion bunch is injected in the ring, extracted after a variable number of turns and its longitudinal profile is studied. Some of the diagnostic tools available in SIR include an emittance measurement system in the injection line, scanning wires in different sections of the ring, phosphor screens at the injection and extraction points and a fast Faraday cup in the extraction line. The design of these systems and the kind of beam information they provide are discussed in detail.
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| THPLT147 | Beam Halo Monitoring on the CLIC Test Facility 3 | plasma, gun, proton, polarization | 2798 | ||
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In high intensity accelerators, the knowledge of the beam halo distribution and its generation mechanisms are important issues. In order to study these phenomena, dedicated beam diagnostics must be foreseen. In circular machines, beam halo was monitored by using scrapers and beam loss detectors. In the framework of the CLIC project, beam halo monitoring is currently under development. The proposed device is based on an imaging system and a masking technique, which suppresses the core of the beam to allow direct observation of the beam halo. A first test was performed on the CLIC test facility 3 in 2003. We discuss the performances and the limitations of this technique pointing out our plans for future developments.
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| THPLT148 | Beam Loss Monitoring on the CLIC Test Facility 3 | plasma, gun, proton, polarization | 2801 | ||
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The CLIC test facility 3 (CTF3) provides a 3.5A, 1.5s electron beam pulse of 150MeV at the end of the linac. The average beam power is 4 kW. Beam loss will be monitored all along the linac in order to keep the radiation level as low as possible. The heavy beam loading of the linac can lead to time transients of beam position and size along the pulse. To compensate these transients effectively a beam loss monitor (BLM) technology has to be chosen with a time response faster than a few nanoseconds. In this context, two different tests have been performed in 2003 on the already existing part of the CTF3 accelerator. Several detectors based on different technologies were first tested in parallel to determine which one was the most appropriate. A second test, in which the beam was intentionally lost in well defined conditions, was then made with the aim of comparing the measurements with simulation results. We present here the results of these tests and our conclusion for the new system to be developed.
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| THPLT150 | Results from Orbit and Optics Improvement by Evaluating the Nonlinear Beam Position Monitor Response in CESR | plasma, gun, proton, polarization | 2804 | ||
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In the Cornell Electron/positron Storage Ring (CESR), pretzel orbits with large horizontal oscillations are used to keep electron and positron beams out of collision except at the interaction point. Since a beam position monitor's (BPM's) response is only linear near the center of the beam pipe, the assumption of linearity does not allow for accurate orbit and phase measurements under colliding beam conditions. Using a numerical model of the BPMs' response to large offsets of the beam position, and an enhanced algorithm for real-time inversion of this nonlinear response function, we have extended our orbit and betatron phase measurements to beams with large pretzel amplitudes. Several measurements demonstrate the applicability, accuracy, and usefulness of this method.
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| THPLT151 | Evaluation of Beam Position Monitors in the Nonlinear Regime | plasma, gun, proton, polarization | 2807 | ||
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Here we present a new algorithm for processing BPM signals and extracting orbit and phase data for very large beam excursion where the BPM response function changes nonlinearly with the beam position. Using two dimensional models of each BPM geometry, we calculate the button response using numerical solution of Laplace's equation and Green's reciprocity theorem. The difference between the calculated signals and the measured signals is minimized in real time to calculate the beam position and measurement errors. Using the derivatives of the response functions, we model the effect of beam shaking, and from it, calculate the betatron phase.
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| THPLT152 | Operation of the Position Measurements for the Isotope Production Facility | plasma, gun, proton, polarization | 2810 | ||
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The Isotope Production Facility (IPF) will provide isotopes for medical purposes by using a 100-MeV H+-beam spur beam line from the Los Alamos Neutron Science Center (LANSCE) facility. Beam position measurements for IPF use a standard micro-stripline beam position monitor (BPM) with both an approximate 50-mm and 75-mm radius. The associated cable plant is unique in that it unambiguously provides a method of verifying the operation of the complete position measurement. The processing electronics module uses a log ratio technique with an error correcting software algorithm so that each the overall position measurement is periodically calibrated over a dynamic range of > 86 dB with errors less than 0.1 dB within this range. A National Instruments LabVIEW virtual instrument performs automatic periodic calibration and verification, and serves the data via the Experimental Physics and Industrial Control System (EPICS) channel access protocol. In order to report the data to the LANSCE facility operators and accelerator physicists, the served data are displayed and archived. This paper will describe the measurement system, commissioning and initial operating experiences.
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| THPLT153 | Commissioning and Initial Operation of the Isotope Production Facility at the Los Alamos Neutron Science Center | plasma, gun, proton, polarization | 2813 | ||
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The recently completed 100-MeV H+ Isotope Production Facility (IPF) at the Los Alamos Neutron Science Center (LANSCE) will provide radioisotopes for medical research and diagnosis, for basic research and for commercial applications. A change to the LANSCE accelerator facility allowed for the installation of the IPF. Three components make up the LANSCE accelerator: an injector that accelerates the H+ beam to 750-KeV, a drift-tube linac (DTL) that increases the beam energy to 100-MeV, and a side-coupled cavity linac (SCCL) that accelerates the beam to 800-MeV. The transition region, a space between the DTL and the SCCL, was modified to permit the insertion of a kicker magnet (23o kick angle) for the purpose of extracting a portion of the 100-MeV H+ beam. A new beam line was installed to transport the extracted H+ beam to the radioisotope production target chamber. This paper will describe the commissioning and initial operating experiences of IPF.
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| THPLT154 | Design of an X-ray Imaging System for the Low-Energy Ring of PEP-II | plasma, gun, proton, polarization | 2816 | ||
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An x-ray beam-size monitor for positrons in the low-energy ring (LER) of the PEP-II B Factory at SLAC is being designed to accommodate the present 2-A, 3.1-GeV beam and anticipated currents of up to 4.7 A. The final photon stop of an arc will be rebuilt to pass dipole radiation through cooled apertures to optics 17 m from the source. Zone-plate imaging there can achieve a resolution of 6 microns, compared to 35 for a pinhole camera. Two multilayer x-ray mirrors precede the zone plate, limiting the bandwidth to 1%, in order to avoid chromatic blurring and protect the zone plate. Despite the narrow bandwidth, the zone plate?s larger diameter compared to a pinhole camera allows for a comparable photon flux. We will image all 1700 LER bunches and also measure them individually, searching for variations along the train due to electron-cloud and beam-beam effects, using a scanning detector conceptually derived from a wire scanner. A mask with three narrow slots at different orientations will scan the image to obtain three projections. In one passage, signals from a fast scintillator and photomultiplier will be rapidly digitized and sorted to profile each bunch.
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| THPLT160 | Measurements of Transverse Coupled-bunch Instabilities in PEP-II | plasma, gun, proton, polarization | 2831 | ||
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At the design currents the PEP-II High and Low Energy Rings operate above the coupled-bunch instability thresholds in horizontal and vertical planes. Both machines have used analog bunch-by-bunch feedback systems to stabilize the beams since commissioning. Here we present a measurement technique that uses the capabilities of the PEP-II programmable digital longitudinal feedback system to provide transient diagnostics in X or Y directions. This technique allows one to measure instability growth or damping rates as well as oscillation frequencies in both open-loop and closed-loop conditions. Based on these measurements the configuration of the relevant transverse feedback channel can be optimized. The technique will be illustrated with instability measurements and feedback optimization examples. Comparisons of the measured modal patterns and growth rates to the theoretical predictions will be presented.
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| THPLT161 | Compton X-ray Source | plasma, proton, polarization, booster | 2834 | ||
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In an effort to develop a monochromatic, tunable source of X-rays in the 20-85 KeV energy range, a 5.5 cell X-band RF gun has been designed and tested. Together with a 1.05 m high gradient accelerating structure (an NLC Collider component), this system generates and accelerates a beam of electrons to energies greater than 60 MeV. Monochromatic X-rays are generated, via the Compton Effect, through a head-on collision of this beam with a multi-terawatt laser beam.We are currently measuring and analyzing the performance of the complete system, including the energy, monochromaticity and emittance of the electron beam, the laser system performance and the X-ray flux from the beam-laser interaction. A tunable, monochromatic X-ray source has important medical applications.We will report on the latest results as well as describe the experimental setup, components and diagnostics.
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| THPLT162 | Diagnosis of Coupling and Beta Function Errors in the PEP-II B-Factory | plasma, proton, polarization, booster | 2837 | ||
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The SLAC Control program has an automatic phase measuring system whereby the beta functions of the two storage rings are measured. This facility has recently been extended to measure coupling between the horizontal and vertical motion and to fit the measured values to their modes of propagation. This facility aids the diagnosis and correction of coupling and focusing errors.
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