| Paper | Title | Page |
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| TUPC001 | Simulations of the Interaction Point for TeV-scale e+ e− Colliders | 985 |
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| The design of a detector and post collisional line of a future linear collider calls for detailed knowledge of the beam-beam dynamics at the interaction point. We here describe the implementation and results of new simulation tools in the program GUINEA-PIG. The subjects are direct trident production relevant in the deep quantum-regime, incoherent muon generation, synchrotron radiation from secondary particles and depolarization effects. We choose beam parameters in the range relevant for CLIC and comment on the implications for the design of such a machine. | ||
| TUPC002 | Study of a Large Piwinski’s Angle Configuration for Linear Colliders | 988 |
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| The application of a Large Piwinski’s Angle configuration to the interaction region of a linear collider is studied. The calculation of the equivalent disruption parameter and beamstrahlung parameter in the presence of a crossing angle are necessary to estimate the beam-beam effects in such a configuration. The reduction of the beam-beam interaction effects, based on these parameters, while keeping same luminosity is presented for both ILC and CLIC parameters. | ||
| TUPC004 | The Luminosity for the ILC Travelling Focus Regime with Offsets and Angle Scans* | 991 |
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| One of the crucial challenges of a future linear collider is to provide high luminosity. In the current ILC design a luminosity of 2x1034 is foreseen. In order to enhance the luminosity, use of the “travelling focus” scheme is under discussion. Within this regime the hourglass effect at the interaction point can be effectively overcome by judiciously arranging for the head and tail of the bunches to be focused at a proportionally displaced longitudinal position. The effect is further enhanced by the strong beam-beam interaction which continuously focuses the bunches during collision. In principle travelling focus could provide an additional 30% luminosity. Nevertheless the regime is highly sensitive to beam-beam transverse and angular offsets at the collision point. The study of the luminosity stability for various ILC parameters using traveling focus will be presented. | ||
| TUPC005 | Evolution of Pressure in Positron Source for Future Linear e+e− Collider | 994 |
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Funding: This work is supported by the German Federal Ministry of Education and Research, Joint Research Project R&D Accelerator "Spin Management", contract number 05H10GUE Energy deposition in the conversion targets of positron sources for future linear colliders induces an immense thermal load and create pressure waves in the material. This stress could substantially reduce the lifetime of the target or other target materials impinged by the incident intense photon or electron beam. We have studied the evolution of acoustic pressure waves in target materials based on the parameter assumptions for the International Linear Collider (ILC) baseline source. The fluid model is employed by taking into account the target and the incident photon beam parameters. Initial results of these new simulations are presented and compared with earlier studies. Prospects for further studies are outlined. |
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| TUPC006 | Production of Highly Polarized Positron Beams* | 997 |
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Funding: This work is supported by the German Federal Ministry of Education and Research, Joint Research Project R&D Accelerator "Spin Management", contract number 05H10GUE Using of polarized electron and positron beams significantly increases the physics potential of future linear colliders. The generation of an intense and highly polarized positron beam is a challenge. The undulator-based positron source located at the end of electron linac is the baseline source for the International Linear Collider. In case of a 250 GeV drive beam energy, an helical undulator with K = 0.92, an undulator period of 11.5 mm and a titanium alloy target of 0.4 radiation length thickness, the average polarization of the generated positrons is relatively low (about 22 percent). In this contribution, the possibilities of increasing the positron polarization have been considered by adjusting the undulator field and selecting those photons and positrons that yield a highly polarized beam. The detailed simulations have been performed with our developed Geant4-based application PPS-Sim*. * http://pps-sim.desy.de |
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| TUPC007 | Kicker and Monitor for CTF3 Phase Feed Forward | 1000 |
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Funding: Work partially supported by the EuCARD research programme, Grant Agreement 227579, within the 'Assessment of Novel Accelerator Concepts'. In the Compact LInear Collider (CLIC) the synchronization of the Drive Beam and the Main Beam has to be assured in the femtosecond range to avoid luminosity reduction of the collider. The Drive and Main Beams arrival time is measured with longitudinal monitors and the correction is applied changing the path length of one beam respect to the other in a magnetic chicane by means of two transverse fast stripline kicker. The performance of the feed forward system will be tested in the CLIC Test Facility (CTF3) measuring the phase at the linac exit, correcting in the chicane after the combination rings and comparing the longitudinal position change before the power RF production system. The developed phase monitors and kicker magnets for the test in CTF3 are described. |
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| TUPC008 | CLIC Two-Beam Module for the CLIC Conceptual Design and Related Experimental Program | 1003 |
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| The Compact LInear Collider (CLIC), being studied at CERN, involves the design and integration of many different technical systems, tightly bound and influencing each other. For the construction of two main linacs it has been decided to proceed with a modular design, and repetitive two-beam modules of a few types were defined. The modules consist of micro-precision components operating under ultra-high vacuum as required by the beam physics. For the CLIC Conceptual Design Report, the development and system integration is mainly focused on the most complex module type containing the highest number of components and technical systems. For proving the proper functioning of the needed technical systems and confirming their feasibility it has been decided to build four prototype modules and test them without beam. In addition, three modules have to be produced in parallel for tests in the CLIC Experimental Area with beam. This paper is focused on the design of the different technical systems and integration issues of the two-beam module. The experimental program for the prototype modules is also recalled. | ||
| TUPC009 | The Recent JINR Advances in Technology Development on Linear Accelerators | 1006 |
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| JINR experts take part in a few ILC related projects including photo injector prototype, participation in design and construction of cryomodules, RND on design of a new version of superconducting niobium resonator, laser metrology, etc. Some new results of this activity as well as recent data of ILC siting investigations in the Dubna region are presented. | ||
| TUPC010 | Status of the Manufacturing of Accelerating Structures for LINACs | 1009 |
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Funding: HTS, DMP, ZEHATZ, CERN Particle accelerators need ongoing development in the state of the art of the field: high-quality manufacturing of accelerating structures, PETS, but also drift tubes, bunchers, high-power couplers, alignment systems, precision test stands, etc. They also require engineering projects in the range of mechatronics, thermodynamics, microwaves, ultra high vacuum, cryogenics, joining techniques, high precision manufacturing, 3D high precision scanning, etc. HTS together with DMP are actually working on all this fronts. In this paper, the actual status of the manufacturing capabilities concerning some accelerating structures will be described. |
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| TUPC011 | Striplines for CLIC Pre-Damping and Damping Rings* | 1012 |
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| The Compact Linear Collider (CLIC) study explores the scheme for an electron-positron collider with high luminosity and a nominal center-of-mass energy of 3 TeV: CLIC would complement LHC physics in the multi-TeV range. The CLIC design relies on the presence of Pre-Damping Rings (PDR) and Damping Rings (DR) to achieve, through synchrotron radiation, the very low emittance needed to fulfil the luminosity requirements. The specifications for the kicker systems are very challenging and include very low beam coupling impedance and excellent field homogeneity: striplines have been chosen for the kicker elements. Analytical calculations have been carried out to determine the effect of tapering upon the high frequency beam coupling impedance. In addition detailed numerical modeling of the field homogeneity has been performed and the sensitivity of the homogeneity to various parameters, including stripline cross-section, has been studied. This paper presents the main conclusions of the beam impedance calculations and field homogeneity predictions. | ||
| TUPC012 | Fabrication and Validation of the Prototype Supporting System for the CLIC Two-beam Modules | 1015 |
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| The Compact LInear Collider (CLIC), currently under study at CERN, aims at the development of a Multi-TeV e+ e- collider and relies upon a novel two-beam acceleration concept. In the two-beam acceleration, the Radio Frequency (RF) power is extracted from a low energy but high-intensity particle beam, and it is transferred to a parallel high energy main beam. The two-beam modules are the smallest repetitive units which compose the two linacs. The RF structures are the most precise components and they are mounted and aligned on specially developed supporting system, which provides stability and quick re-positioning. The supporting girders have stringent stiffness and damping requirements, imposed by beam physics requirements. In addition, several constraints, such as allocated space and weight limitation have to be taken into consideration. This paper describes different girder configurations following various fabrication techniques and materials. Extensive qualification measurements have been performed on the first prototype units, and the main results are also presented. | ||
| TUPC013 | Simulation of Phase Stability at the Flat Top of the CLIC Drive Beam | 1018 |
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Funding: University of Oxford The drive beam phase stability is one of the critical issues of the Compact Linear Collider (CLIC). In this paper the generation and propagation of drive beam phase errors is studied for effects that vary during the drive beam pulse. This includes the influence of drive beam current and phase errors as well as of drive beam accelerator RF phase and amplitude errors on the drive beam phase after the compressor chicanes and the analysis of the propagation of these errors through the drive beam combination scheme. The impact of the imperfections on the main beam is studied including the possible correction with help of a feedforward system. |
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| TUPC014 | System Control for the CLIC Main Beam Quadrupole Stabilization and Nano-positioning* | 1021 |
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| The conceptual design of the active stabilization and nano-positioning of the CLIC main beam quadrupoles was validated in models and experimentally demonstrated on test benches. Although the mechanical vibrations were reduced to within the specification of 1.5 nm at 1 Hz, additional input for the stabilization system control was received from integrated luminosity simulations that included the measured stabilization transfer functions. Studies are ongoing to obtain a transfer function which is more compatible with beam based orbit feedback; it concerns the controller layout, new sensors and their combination. In addition, the gain margin must be increased in order to reach the requirements from a higher vibration background. For this purpose, the mechanical support is adapted to raise the frequency of some resonances in the system and the implementation of force sensors is considered. Furthermore, this will increase the speed of repositioning the magnets between beam pulses. This paper describes the improvements and their implementation from a controls perspective. | ||
| TUPC015 | Comparative Wakefield Analysis of a First Prototype of a DDS Structure for CLIC Main Linac | 1024 |
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| A Damped Detuned Structure (DDS) for CLIC main linac has been proposed as an alternative to the present baseline design which is based on heavy damping. A first prototype, CLICDDSA, for high power tests has been already designed and is under construction. It is also foreseen to design a further prototype, CLICDDSB, to test both the wakefield suppression and high power performances. Wakefield calculations for DDS are, in the early design stage, based on single infinitely periodic cells. Though cell-to-cell interaction is taken into account to calculate the wakefields, it is important to study full structure properties using computational tools. In particular this is fundamental for defining the input parameters for the HOM coupler that is crucial for the performances of DDS. In the following a full analysis of wakefields and impedances based on simulations conducted with finite difference based electromagnetic computer code GdfidL will be presented. | ||
| TUPC016 | Status of the ATF2 Lattices | 1027 |
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| The latest status for the ATF2 Nominal and Ultra-low beta lattices designs obtained to minimize the detrimental effect of the measured multipoles are presented in this paper. A set of correction knobs for the most important aberrations at the IP have been obtained for both lattices in order to perform the tuning under realistic imperfections. Starting from the tuned ATF2 Nominal lattice a squeeze sequence reducing betay is performed to reach the ultra-low beta lattice. Tuning results are shown for both options. | ||
| TUPC017 | Civil Engineering Studies for Major Projects after LHC | 1030 |
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| CERN civil engineers are heavily involved in studying several major projects to succeed/complement the LHC. Infrastructure works typically represent one third of the cost of major physics projects, so it's critical that the construction costs are well understood from the conceptual stage. For example, CERN are studying infrastructure requirements for the Linear Collider (CLIC & ILC) and the LHeC projects. This poster presents some of the key civil engineering challenges faced in such large scale projects. | ||
| TUPC018 | Progress on Modelling of the Thermo-Mechanical Behavior of the CLIC Two-Beam Module | 1033 |
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| The luminosity goal of the CLIC collider, currently under study, imposes micrometer mechanical stability of the 2-m long two-beam modules, the shortest repetitive elements of the main linacs. These modules will be exposed to variable high power dissipation during operation resulting in mechanical distortions in and between module components. The stability of the CLIC module will be tested in laboratory conditions at CERN in a full-scale prototype module. In this paper, the FEA model developed for CLIC prototype module is described. The thermal and structural results for the new module configuration are presented considering the thermo-mechanical behavior of the CLIC collider in its primary operation modes. These results will be compared to the laboratory measurements to be done during 2011 and 2012 with the full-scale prototype module. The experimental results will allow for better understanding of the module behaviour and they will be propagated back to the present thermo-mechanical model. | ||
| TUPC019 | Beam-based Alignment of CLIC Drive Beam Decelerator using Girders Movers | 1036 |
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| The CLIC drive beams will provide the rf power to accelerate the colliding beams: in order to reach the design performance, an efficient transport of the drive beam has to be ensured in spite of its challenging energy spread and large current intensity. As shown in previous studies, the specifications can be met by coupling a convenient optics design with the state-of-the-art of pre-alignment and beam-based alignment techniques. In this paper we consider a novel beam-based alignment scheme that does not require quadrupole movers or dipole correctors but uses the motors already foreseen for the pre-alignment system. This implies potential savings in terms of complexity and cost at the expense of the alignment flexibility: the performance, limitations and sensitivity to pre-alignment tolerances of this method are discussed. | ||
| TUPC020 | Alignment and Wake Field Issues in the CLIC RTML | 1039 |
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| At main linac injection the particle beams need to stay within tight tolerances for the transverse emittances and the pointing stability. We study how these tolerances influence alignment requirements for the RTML components and the stability of the beams entering the RTML. An emphasize is put on the booster linac and the RF cavities of the second bunch compression stage since short and long range wake fields might strongly influence beam dynamics in these parts of the RTML. | ||
| TUPC021 | The CLIC Feasibility Demonstration in CTF3 | 1042 |
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| The objective of the CLIC Test Facility CTF3 is to demonstrate the feasibility issues of the CLIC two-beam technology: the efficient generation of a very high current drive beam, used as the power source to accelerate the main beam to multi-TeV energies with gradient over 100MeV/m, stable drive beam deceleration over long distances. Results on successful beam acceleration with over 100 MeV/m energy gain are shown. Measurements of drive beam deceleration over a chain of Power Extraction Structures are presented. The achieved RF power levels, the stability of the power production and of the deceleration are discussed. Finally, we overview the remaining issues to be shown until the end of 2011. | ||
| TUPC022 | Design of the CLIC Drive Beam Recombination Complex | 1045 |
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| The CLIC Drive Beam Recombination Complex (DBRC) is designed to compress beam pulses from a current of 4.1 A to 100 A before using them to produce RF power in the deceleration lines. The beam is transported isochronously through a complex system consisting of a delay loop, two combiner rings and final turn around. The system is designed to preserve transverse and longitudinal emittances. During the optics design, chromaticity and non-linear dispersion were identified as the main single particle dynamics causes for transverse emittance increase. Different sextupole families are used to compensate these chromatic effects while keeping isochronicity. The bunch length is also adjusted to minimize coherent synchrotron radiation effects on bunch length, energy spread and transverse emittance. Finally, the injection scheme of the combiner rings was improved making the time variable bump created with help of the RF deflectors truly achromatic. | ||
| TUPC023 | Status of Ground Motion Mitigation Techniques for CLIC | 1048 |
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| The Compact Linear Collider (CLIC) accelerator has strong stability requirements on the position of the beam. In particular, the beam position will be sensitive to ground motion. A number of mitigation techniques are proposed - quadrupole stabilisation and positioning, final doublet stabilisation as well as beam based orbit and interaction point (IP) feedback. Integrated studies of the impact of the ground motion on the CLIC Main Linac (ML) and Beam Delivery System (BDS) have been performed, which model the hardware and beam performance in detail. Based on the results future improvements of the mitigation techniques are suggested and simulated. It is shown that with the current design the tight luminosity budget for ground motion effects is fulfilled and accordingly, an essential feasibility issue of CLIC has been addressed. | ||
| TUPC025 | Calibration Errors in the Cavity Beam Position Monitor System at the ATF2 | 1051 |
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| It has been shown at the Accelerator Test Facility at KEK, that it is possible to run a system of 37 cavity beam position monitors (BPMs) and achieve high working resolution. However, stability of the calibration constants (position scale and radio frequency (RF) phase) over a three/four week running period is yet to be demonstrated. During the calibration procedure, random beam jitter gives rise to a statistical error in the position scale and slow orbit drift in position and tilt causes systematic errors in both the position scale and RF phase. These errors are dominant and have been evaluated for each BPM. The results are compared with the errors expected after a tested method of beam jitter subtraction has been applied. | ||
| TUPC026 | Status of the Crab Cavity Design for the CLIC | 1054 |
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| RF design of a crab cavity (2π/3, 11.9942 GHz) for the Compact Linear Collide (CLIC) is presented. As part of the UK-CLIC collaboration, CERN is building two copper prototypes, designed by Lancaster University / Cockcroft Institute. The first prototype to be made will be a 12 cell undamped cavity and the second will be waveguide damped cavity. The RF test at CERN will help characterisation of the dipole mode with X-band RF pulses of 15 MW peak power and pulse length of ~242 ns. Since the cavity frequency and phase advance per cell are identical to those of the CLIC main linac, the first prototype could exploit CERN’s X-band cavity characterisation facilities. A fully damped cavity will be required for the actual machine in order to meet the luminosity specs. The damped prototype will use an identical coupler type as the undamped one, but the cells will have damping waveguides with / without dielectric material. | ||
| TUPC027 | CLIC Post-Collision Line Luminosity Monitoring | 1057 |
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| The CLIC post collision line is designed to transport the un-collided beams and the products of the collided beams with a total power of 14 MW to the main beam dump. Full Monte Carlo simulation has been done for the description of the Compact Linear Collider (CLIC) luminosity monitoring at the post collision line. One method of the luminosity diagnostic is based on the detection of high energy muons produced by the beamsstrahlung photons in the main beam dump. The disrupted beam and the beamsstrahlung photons produce at the order of 106 muons per bunch crossing, with energies greater than 10 GeV. Currently threshold Cherenkov counters are considered after the beam dump for the detection of these high energy muons. A second method using the direct detection of the beamsstrahlung photons is also considered. | ||
| TUPC028 | Background and Energy Deposition Studies for the CLIC Post-Collision Line* | 1060 |
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| The CLIC post-collision line is designed to transport the spent-beam products of collision to their respective dumps, with minimal losses and thus minimal background contributions. With nanometre spot-sizes at TeV energies, large beam-beam effects induce divergence and dispersion of the outgoing beams, with a large production cross-section of Beamstrahlung photons and subsequently coherent pairs. The post-collision line should provide sufficient divergence of the beam to avoid damage to the vacuum exit and dump entrance windows. In this study, the beam losses are investigated, with the production of secondary particles from the interaction with matter simulated. The particle flux leakage from absorbers and dumps is modelled to determine the total energy deposited on magnets of the post-collision line. Finally, both electromagnetic and hadronic backgrounds at the CLIC experiment are considered. | ||
| TUPC030 | Recommendation for Mitigations of the Electron Cloud Instability in the ILC | 1063 |
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Funding: Work supported by the Director, Office of Science, High Energy Physics, U.S. DOE under Contract No. DE-AC02-76SF00515. Electron cloud has been identified as one of the highest priority issues for the ILC Damping Rings (DR). A working group has evaluated the electron cloud effect and instability, and mitigation solutions for the electron cloud formation. Working group deliverables include recommendations for the baseline and alternate solutions for the electron cloud mitigation in various regions of the ILC Positron DR, which is presently assumed to be the 3.2km design. Detailed studies of a range of mitigation options including coatings, clearing electrodes, grooves and novel concepts, were carried out over the previous several years by nearly 50 researchers, and the results of the studies form the basis for the recommendation. The assessments of the benefits or risks associated with the various options were based on a systematic ranking scheme. The recommendations are the result of the working group discussions held at numerous meetings and during a dedicated workshop. The mitigation choices will be also presented in a more detailed report later in 2012. In addition, a number of items requiring further investigation were identified and studies will be carried out at CesrTA and other institutions. |
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| TUPC031 | Advanced Research Electron Accelerator Laboratory Based on Photocathode RF Gun | 1066 |
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| The low energy sub-picosecond duration electron bunches with extremely small beam emittance have wide applications in advanced research of new accelerator concepts, radiation physics, time-resolved pulse radiolysis and electron diffraction. The conceptual design and experimental program of the Advanced Research Electron Accelerator Laboratory (AREAL) at CANDLE based on photocathode RF gun are presented. The AREAL design implies single and multibunch operation modes with variable beam energy of 5-20 MeV and 10-100 pC bunch charge. The design is based on 3 GHz 1.6 cells RF gun followed by S-Band accelerating linac. | ||
| TUPC032 | Beam Phase-Space Study for AREAL RF Photogun Linac | 1069 |
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| In order to produce high brightness electron beams with sub-picosecond bunch duration, the creation of Advanced Research Electron Accelerator Laboratory (AREAL) at CANDLE based on photocathode RF gun is under consideration. For several experimental setup purposes the linac will operate in single and multibunch modes with final beam energy 5-20 MeV and the bunch charge 10 100 pC. The study of beam phase space evolution along the linac is performed to optimize the beam main characteristics: emittance, bunch length and energy spread. The dependence of longitudinal and transverse distribution of electrons in photocathode region on RF cavity performances is analyzed. | ||
| TUPC033 | Verifying the Single Bunch Capability of the New Injector at ELSA* | 1072 |
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Funding: Funded by the DFG within the SFB / TR 16 and the Helmholtz Alliance HA 101 "Physics at the Terascale". In order to enhance the operating capabilities of the Bonn University Accelerator Facility, ELSA, a new injector is currently under commissioning. One of its main purpose is to allow a single pulse mode. The injector produces a single electron bunch with 1.5 A pulse current. Design and optimization of the injector have been performed with EGUN, PARMELA and numerical simulations based on the numerical integration of the paraxial equation. A 1 ns long pulse is produced by a thermionic electron source with 90 kV anode - cathode voltage, then compressed and pre-accelerated by a subsequent 500 MHz RF cavity and a four-cell travelling wave buncher. Finally, the bunch will be accelerated to 20 MeV by the main LINAC section. Measurements have been conducted concerning the resulting pulse length and pulse charge to confirm the predictions made by simulations and to investigate the efficiency of the injector system. |
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| TUPC034 | Design Studies on 100 MeV/100 kW Electron Linac for NSC KIPT Neutron Source on the Base of Subcritical Assembly Driven by Linac | 1075 |
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| In NSC KIPT, Kharkov, Ukraine, a neutron source on the base of subcritical assembly driven by 100 MeV/100 kW electron linear accelerator is under design and development. To provide neutron flux value of about 1013 neutron/s the electron linear accelerator with 100 MeV beam and average beam power of 100 kW will be used. Construction and manufacture of the linear accelerator of such high beam intensity with low emittance and beam losses is a challenging task. In the report the project of the electron linear accelerator of the required beam energy and intensity is described. The accelerator structure and main technical solutions are presented. To overcome the BBU effect of this high average beam current, several effective measures are adopt, such as using constant gradient structure to spread the HOMs frequencies different cells, larger inner radius and shorter section length make the higher group velocity and optimize the structure geometry to keep the shunt impedance as good as possible. After the beam bunching system, a chicane is followed to chopper the beam to avoid the beam lost in the higher energy part. | ||
| TUPC036 | S-band ps Pulse Photoinjector for THz Radiation Source | 1078 |
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| S-band photoinjectors with ps pulse are becoming promising as e-guns for high-intensity sub-mm wavelength pulse source. Development of accelerating system for photoinjector with ps bunch is reported. The main aim is to develop a model of accelerating structure that provide top accelerating fields in respect to high electric strength and low RF power uses. The accelerating structures consisting of 1.6 cell of disk-loaded waveguide (DLW), 3 cells and 2 half-cells of DLW, 7 cels and 2 half-cells of DLW and accelerating structure based on running wave resonator with 7 cells and 2 half-cells of DLW are studying. The resonant models of these structures and the structures with power ports were designed. Electrodynamics characteristics, electric field distribution for all models were acquired. Accelerating structure consisting of 1.6 cells will operate in pi mode of standing wave, all other structures operate in pi/2 mode traveling wave. Accelerating structure based on running wave resonator with 7 cells and 2 half-cells of DLW has most suitable electrodynamics characteristics and field distribution for sub-mm pulse source according to simulation results. | ||
| TUPC038 | A Low Energy Thermionic RF Gun Linac for Ultrashort Electron Beam | 1081 |
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| A low energy test linac is being constructed at NSRRC for technological development of high brightness electron injector. It is a 29 MeV S-band linac that equipped with a high gradient thermionic cathode rf gun for generation of ultrashort relativistic electron beam by velocity bunching in the rf linac section located at downstream. High quality GHz-repetition-rate electron pulses of about 30 pC in bunch charge, pulse duration as short as 100 fsec can be produced from this test facility. It can be used as the driver for future light source experiments such as ultrafast head-on inverse Compton scattering (ICS) X-ray source and intense coherent THz free electron lasers. | ||
| TUPC039 | Proposals for Electron Beam Transportation Channel to Provide Homogeneous Beam Density Distribution at a Target Surface | 1084 |
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| NSC KIPT neutron source will use 64x64 mm rectangular tungsten or uranium target. To generate maximum neutron flux, prevent overheating of the target and reduce thermal stress one should provide homogeneous electron beam distribution at the target surface. In the facility transportation channel three different possibilities of electron beam density redistribution along the target surface can be realized. It can be the fast beam scanning with two dimensional scanning magnets; the method of uniform beam distribution formation with linear focusing elements (dipole and quadrupole magnets) and nonlinear focusing elements (octupole magnets), when final required rectangular beam shape with homogeneous beam density is formed at target; and combined method, when one forms the small rectangular beam with homogeneous beam density distribution and scan it over the target surface with scanning magnets. In the report the all tree methods are considered and discussed considering the layout of the NSC KIPT transportation channel. Calculation results show that the proposed transportation channel lattice can provide uniform beam of rectangular shape with sizes 64x64 mm without target overheating. | ||
| TUPC040 | Modified Lattice of the Compton X-ray Source NESTOR | 1087 |
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| NESTOR is Compton X-ray source that is under commissioning in NSC KIPT. One of the main parts of the facility is the middle energy storage ring (40-225 MeV). The storage ring has comprehensive lattice to provide low emittance, low beam size in the interaction point and big value of the energy acceptance. One of the NESTOR storage ring lattice feature is use of bending magnets of 0.5 m radius with combined focusing function. It leads to increasing of 3D magnetic field effects on electron beam dynamics. After NESTOR magnetic element manufacturing characteristics of element magnetic fields were measured and the effect of the real magnetic field distribution on beam dynamics was calculated. As a result, to provide project X-ray source characteristics the parameters of NESTOR storage ring lattice should be modified. The second reason for the lattice modification was the desire to increase the interaction point straight section length. The results of the beam dynamics simulation after lattice modification and optimization show that the storage ring will provide all project electron beam parameters. The results of the electron beam simulations are presented in the paper. | ||
| TUPC041 | Self-consistent Time-dependent Quasi-3D Model of Multipactor in Dielectric-loaded Accelerating Structures | 1090 |
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Funding: This work is supported by the Office of High Energy Physics of the US Department of Energy. Multipactor (MP) manifests itself as a rapid growth of the number of secondary electrons emitted from a solid surface in the presence of the RF field under vacuum conditions. The secondary electrons appear as the result of surface impacts of energetic primary electrons accelerated by the RF field. MP occurs in various microwave and RF systems and usually severely degrades their performance. Therefore, theoretical and experimental studies of MP are of great interest to researchers working in related areas of physics and engineering. In this paper we study MP in dielectric-loaded accelerating (DLA) structures. We started our work with the development of a self-consistent time-dependent 2D model of MP in such structures*. To benchmark that model, we compared its results with available experimental data**. The comparison showed good agreement between theory and experiment for DLA structures of larger diameter, however for structures of smaller diameter a significant discrepancy was observed. Therefore, we decided to develop a new quasi-3D model of MP that would allow us to take into account the effects ignored in our 2D studies. Results of our 3D analysis are presented in this paper. * O. V. Sinitsyn, G. S. Nusinovich and T. M. Antonsen, Jr., Phys. Plasmas, 16, 073102 (2009). ** O. V. Sinitsyn, G. S. Nusinovich and T. M. Antonsen, Jr., AIP Conf. Proc., 1299, 302 (2010). |
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| TUPC042 | First Beam to FACET | 1093 |
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Funding: This work was supported by the Department of Energy contract DE-AC02-76SF00515. The SLAC 3km linear electron accelerator has been reconfigured to provide a beam of electrons to the new FACET facility while simultaneously providing an electron beam to the Linac Coherent Light Source (LCLS). FACET is a new experimental facility constructed in the linac tunnel that can transport, compress, and focus electron bunches to support a variety of accelerator R&D experiments. In this paper, we describe our first experiences with the operation of the linac for this new facility. |
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| TUPC043 | SEM Field Emission Probe Surface Science Study | 1096 |
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Funding: This work is supported by Department of Energy Contract No. DE-AC03- 76SF00515. After decades of rf breakdown research, a common acknowledgement among researchers is that a better understanding of what is happening on the surface at a microscopic level needs to be the impetus for future studies. We are designing and fabricating an electron microscope-based high-electric-field current-emission probe to study topographic material features which will enable us to better understand and further advance the technology of high-brightness photocathode rf guns and enable the study of high gradient phenomena. The SEM field emission probe will provide an important diagnostic tool allowing cathodes and high gradient surfaces to be evaluated before and after testing and will help identify and understand the relationship between high field emission locations and vacuum breakdown, non-uniform emission, surface cracking, hotspots, etc. The preliminary results and 2012 goals will be presented. |
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| TUPC045 | Recirculating Electron Linacs (REL) for LHeC and eRHIC | 1099 |
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Funding: Work performed under a Contract Number DE-AC02-98CH10886 with the auspices of the US Department of Energy. We present a design of a CW Electron Recovery Linacs (ERL) for future electron hadron colliders eRHIC and LHeC. In eRHIC, a six-pass ERL would be installed in the existing tunnel of the present Relativistic Heavy Ion Collider (RHIC). The 5-30 GeV polarized electrons will collide with RHIC’s 50-250 (325) GeV polarized protons or 20-100 (130) GeV/u heavy ions. In LHeC a 3-pass 60 GeV CW ERL will produce polarized electrons for collisions with 7 TeV protons. After collision, electron beam energy is recovered and electrons are dumped at low energy. Two superconducting linacs are located in the two straight sections in both ERLs. The multiple arcs are made of Flexible Momentum Compaction lattice (FMC) allowing adjustable momentum compaction for electrons with different energies. The multiple arcs, placed above each other, are matched to the two linac’s straight sections with splitters and combiners. |
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| TUPC046 | Alignment Tolerances for Vertical Emittance | 1102 |
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| Alignment tolerances for the CLIC main damping ring magnetic lattice elements are presented. Tolerances are defined by the design equilibrium vertical emittance of 1 pm rad. The sensitivity of the uncorrected lattice to magnet misalignments is presented. Misalignments considered included quadrupole vertical offsets and rolls, sextupole vertical offsets, and main dipole rolls. Seeded simulations were conducted in MAD-X, and compared with expectation values calculated from theory. The lattice was found to be sensitive to betatron coupling as a result of sextupole vertical offsets in the arcs. Alignment tolerances, BPM and corrector requirements are presented also. For the same misalignment types, the equilibrium emittance of the corrected lattice is simulated. These are compared with expectation values calculated from theory. The vertical alignment tolerance of arc sextupoles is again demanding. | ||
| TUPC048 | First Measurement Results of the LHC Longitudinal Density Monitor | 1105 |
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Funding: The primary author is funded by the E.U. under the DITANET Marie Curie network. Knowledge of the longitudinal distribution of particles is important for various aspects of accelerator operation, for example to check the injection quality and to characterize the development of ghost bunches before and during the physics periods. A new detector, the LHC Longitudinal Density Monitor (LDM) is a single-photon counting system measuring synchrotron light by means of an avalanche photodiode detector. The unprecedented energies reached in the LHC allow synchrotron light diagnostics to be used with both protons and heavy ions. The LDM is able to longitudinally profile the whole ring with a resolution close to the target of 50 ps. On-line correction for the effects of the detector deadtime, pile-up and afterpulsing allow a dynamic range of 105 to be achieved. The LDM operated during the 2010 lead ion run and during 2011 with protons. Measurements from both runs are presented in this contribution along with an analysis of the LDM performance and an outlook for future upgrades. |
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| TUPC049 | Optics considerations for the Delay Loop in the CLIC Damping Rings Complex | 1108 |
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| For the recombination of the two trains coming from the CLIC damping rings, a delay loop will be used in order to obtain the nominal 0.5~ns bunch spacing. The optics design of the loop is based upon an isochronous ring, in order to preserve the longitudinal beam distribution. Analytical expressions for achieving isochronous conditions in high order for Theoretical Minimum Emittance cells are obtained. A parametrisation of the quadrupole settings for achieving these conditions is presented, along with general considerations regarding the choice of bending magnet characteristics. | ||
| TUPC050 | Impedance Effects in the CLIC Damping Rings | 1111 |
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| Due to the unprecedented brilliance of the beams, the performance of the Compact Linear Collider (CLIC) damping rings is affected by collective effects. Single bunch instability thresholds based on a broad-band resonator model and the associated coherent tune shifts have been evaluated with the HEADTAIL code. Simulations performed for positive and negative values of chromaticity proved that higher order bunch modes can be potentially dangerous for the beam stability. This study also includes the effects of high frequency resistive wall impedance due to different coatings applied on the chambers of the wigglers for e-cloud mitigation and/or ultra-low vacuum pressure. The impact of the resistive-wall wake fields on the transverse impedance budget is finally discussed. | ||
| TUPC052 | Normal Mode BPM Calibration for Ultralow-Emittance Tuning in Lepton Storage Rings | 1114 |
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| BPMs capable of high-resolution turn-by-turn measurements offer the possibility of new techniques for tuning for ultra-low beam emittance. In this paper, we describe how signals collected from individual buttons during resonant beam excitation can be used to calibrate BPMs to read the beam position in a normal mode coordinate system. This allows for rapid minimization of the mode II emittance, simply by correcting the mode II dispersion. Simulations indicate that the technique is effective and robust, and has the benefit of being insensitive to BPM gain and alignment errors that can limit the effectiveness of other techniques. | ||
| TUPC053 | Superconducting Positron Stacking Ring for CLIC | 1117 |
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| The generation of polarized positrons for future colliders based on Compton storage rings is a promising method. A challenging key ingredient of this method is the necessary quasi-continuous positron injection into a stacking ring. The ordinary methods of multi-turn injection are not appropriate for this purpose, because the required number of injection-turns is a few hundred, and the emittance of the injected positron bunches is large. This paper describes a possible solution based on 5 GeV superconducting stacking ring, where a novel method of the combined longitudinal and transverse injection process is used to stack positrons. The ring dynamic aperture allows to inject the positron beam with normalized emittance up to 2000 micrometers during a few hundred turns. The injection efficiency is larger than 90% in simulation. The number of the injection turns is only limited by the synchrotron radiation power. The ring lattice and the results of injection simulations are presented. | ||
| TUPC054 | LHeC ERL Design and Beam-dynamics Issues | 1120 |
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| We discuss machine and beam parameter choices for a Linac-Ring option of the Large Hadron electron Collider (LHeC) based on the LHC. With the total wall-plug power limited to 100 MW and a target current of about 6 mA the desired luminosity of 1033 cm-2 s-1 can be reached, providing one exploits unique features of the Energy Recovery Linac (ERL). Here, we describe the overall layout of such ERL complex located on the LHC site. We present an optimized multi-pass linac optics enabling operation of the proposed 3-pass Recirculating Linear Accelerator (RLA) in the Energy Recovery mode. We also describe emittance preserving return arc optics architecture; including layout and optics of the arc switch-yard. Furthermore, we discuss importance of collective effects such as: beam breakup in the RLA, as well as ion accumulation, with design-integrated mitigation measures, and the electron-beam disruption in collision. Finally, a few open questions are highlighted. | ||
| TUPC055 | Strongly Space Charge Dominated Beam Transport at 50 keV | 1123 |
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Funding: supported by DFG (SFB/TR16) A pulsed (100 nC in 1 us), low energetic beam of polarized electrons is routinely provided by an inverted source of polarized electrons at ELSA. The beam transport to the linear accelerator is strongly space charge dominated due to the beam energy of 50 keV. Thus, the actual beam current has an impact on the beam dynamics, and the optics of the transfer line to the linear accelerator must be optimized with respect to the chosen beam intensity. Numerical simulations of the beam transport demonstrate that an intensity upgrade from 100 mA to 200 mA is feasible. In order to successfully adjust the focussing strength of the magnets according to the final results of the simulation, dedicated beam diagnostics like wire scanners suitable for extreme-high vacuum applications are required. |
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| TUPC057 | Femtosecond Photoinjector and Relativistic Electron Microscopy | 1126 |
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| A new rf gun driven by a femtosecond laser has been developed successfully for the relativistic electron diffraction in Osaka University for the study of ultrafast dynamics of intricate molecular and atomic processes in materials. The beam dynamics of femtosecond electron bunch in the rf gun were investigated to achieve a low-emittance and low-energy-spread; i.e. 0.1 mm-mrad and 10-4. A time-resolved relativistic electron microscopy is being developed to reveal the hidden dynamics on the femtosecond and nanometer scales. The same demonstrations of the MeV electron diffraction/imaging measurements were reported. | ||
| TUPC058 | Design of a Chirping Cell Attached RF Gun for Ultrashort Electron Generation | 1129 |
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Funding: Work supported by JSPS Grant-in-Aid for Scientific Research (A) 10001690 We have been developing an S-band photocathode rf electron gun at Waseda university. Our rf-gun cavity was firstly designed by BNL and then, modified by our group. In this paper, we will introduce a newly designed rf-gun cavity with energy chirping cell. To generate an energy chirped electron bunch, we attached extra-cell for 1.6cell rf-gun cavity. Cavity design was done by Superfish and particle tracing by PARMELA. By optimizing the chirping cell, we observed linear chirped electron bunch. The front electron have lower energy than rear. Then transporting about 2m, the bunch can be compressed down to 200fsec electron bunch with the charge of 160pC. This ultrashort bunch will be able to use for generating CSR THz radiation, pumping some material to be studied by pulse radiolysis method, and so on. In this conference, the design of chirping cell attached rf-gun, the results of tracing simulation and plan of manufacturing will be presented. |
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| TUPC059 | Study on Energy Compensation by RF Amplitude Modulation for High Intense Electron Beam Generated by a Photocathode RF-Gun | 1132 |
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Funding: Work supported by JSPS Grant-in-Aid for Scientific Research(A)10001690 and JST Quantum Beam Program. At Waseda University, we have been studying a high quality electron beam generation and its application experiments with a Cs-Te photocathode RF-Gun. To generate more intense and stable electron beam, we have been developing the cathode irradiating UV laser which consists of optical fiber amplifier and LD pumped amplifier. As the result, more than 100 multi-bunch electron beam with 1nC each bunch charge was obtained. However, it is considered that the accelerating voltage will decrease because of the beam loading effect. So we have studied the RF amplitude modulation technique to compensate the beam energy difference. The energy difference will caused by transient accelerating voltage in RF-Gun cavity and beam loading effect. As the result of this compensation method, the energy difference has been compensated to 1%p-p, while 5%p-p without compensation. In this conference, we will report the details of energy compensation method using the RF amplitude modulation, the results of beam experiments and the future plans. |
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| TUPC060 | A Multi-mode RF Photocathode Gun | 1135 |
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| A photocathode injection gun based on standard emittance compensating techniques and driven by several (N ≥ 2) harmonically related RF sources is considered. Multi-harmonic excitation can provide high-quality flatness in time of the field at the cathode when a bunch is being injected. This allows one to obtain ≥1 nC, 20-40 ps electron bunches with preservation of low emittance. Another advantage is a reduction of Ohmic losses and the required input RF power (for a given cathode field). Preliminary calculations show that input power in a three-mode cavity (0.65 GHz, 1.3 GHz, 2.6 GHz) is nearly half the power needed to feed a single mode with the same cathode field. A further appealing property is the predicted increase of breakdown threshold due to a reduction of surface exposure time to high fields in a symmetric cavity, and due to the so-called anode-cathode effect in a longitudinally asymmetric cavity. These properties may help one to reach bunch energies as high as 3-5 MeV after the first half cell. | ||
| TUPC062 | Electron Beam Energy Measurement at the Australian Synchrotron Storage Ring | 1138 |
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| The technique of resonant spin depolarization was used to precisely measure the electron beam energy in the storage ring at the Australian Synchrotron. A detector and data acquisition system dedicated to the measurement were developed. Using the system, the long term energy stability of the storage ring was monitored and a mechanical realignment of the ring was clearly seen in the energy data. Details of the parameters used to optimize the measurement are also discussed. | ||
| TUPC063 | Energy Verification in Ion Beam Therapy | 1141 |
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Funding: Austrian Federal Ministry for Science and Research, CERN Technology Doctoral Student Program The adoption of synchrotrons for medical applications necessitates a comprehensive on-line verification of all beam parameters, autonomous of common beam monitors. In particular for energy verification, the required precision of down to 0.1 MeV, in absolute terms, poses a special challenge regarding the betatron-core driven 3rd order extraction mechanism which is intended to be used at MedAustron. Two different energy verification options have been studied and their limiting factors were investigated: 1) A time-of-flight measurement inside the synchrotron, limited by the orbit circumference information and measurement duration as well as extraction uncertainties. 2) A calorimeter-style system in the extraction line, limited by radiation hardness and statistical fluctuations. The paper discusses in detail the benefits and specific aspects of each method. |
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| TUPC064 | Transverse Phase Space Tomography in TRIUMF Injection Beamline | 1144 |
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Funding: TRIUMF receives funding via a contribution agreement through the National Research Council of Canada. By tomography is meant the reconstruction of a 2-dimensional distribution from a number of 1-dimensional projections. In the case of transverse phase space, one records many profiles while varying a focusing device such as a quadrupole. Our aim was to investigate the two transverse phase space distributions in our 300keV H-minus beamline. We performed a series of measurements of beam profiles as a function of the voltage of an electrostatic quadrupole and used these along with the corresponding calculated transfer matrices in an iterative program based upon the Maximum Entropy algorithm, to find the phase space distributions. As well, we made measurements using an Allison-type emittance scanner to scan both planes. In this paper we present the details of these measurements, calculations, and we compare the two techniques. |
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| TUPC065 | Upgrade of the ISAC Time-of-flight System | 1147 |
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| The ISAC facility at TRIUMF produces stable and radioactive ion beams in a wide range of intensities and energies. The beam diagnostics was designed to support the beam delivery in every possible operating regime. Thus, the time-of-flight system is capable of measuring the beam velocity with accuracy of better than 0.1% at beam intensities from 1011 down to ~ 104 ions per second. It consists of three high resolution timing secondary electron emission monitors and has been in operation since 2006. Recently all three monitors were rebuilt with the aim to facilitate monitor alignment with respect to the beam. The system was also equipped with an UV laser that allows perform an accurate absolute calibration and monitor tuning with no beam present. | ||
| TUPC066 | Charged Particle Beam Profile Detector based on Yb-doped Optical Fibers | 1150 |
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Funding: The Danish National Advanced Technology Foundation, contract # 002-2005-1 A radiation robust, high dynamic range beam profile detector based on scintillating fibers will be presented. The beam profile detector has been developed for particle therapy type ion beams of multiple hundreds MeV/n in the intensity range from 105 to 109 ions/s as a simple and less expensive replacement for MWPC based detectors. Scintillating fibers are typically based on doped polymers, which are sensitive to radiation damage. Here we report on the advantage of using silica optical fibers doped with rare-earth elements for the purpose of detecting ionizing radiation. Specifically, we find that ytterbium doped fibers generate a strong emission signal in the near-infrared from the Yb3+ state when penetrated by ionizing radiation, and that the emission has a high resistance against the accumulated dose in the fiber. We demonstrate the use of such fibers in a beam profile detector for charged particle beams in medical applications (radionuclide production and hadron therapy); more generally they are a promising alternative for prolonged used in ionizing radiation, such as accelerator diagnostics equipment or space applications. |
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| TUPC067 | Simulations of Effects of Detector Materials and Geometry to the Beam Properties of Super-FRS | 1153 |
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The Super-FRS is a superconducting fragment separator that will be built as part of the FAIR facility. For the slow-extraction part of the beam diagnostics system a total of 32 detectors are needed for the beam monitoring, tracking and characterization of the produced ions. GEM-TPC detectors are planned to be used for the diagnostics at slow extraction mode of the separator*,**. The detectors will be placed in focal planes along the separator. Simulations have been made to study the effects of the detector materials and geometries in order minimize their influence to the performance of the separator. Results of the optimization using different simulation tools will be presented.
* F. Garcia et al., 2009 IEEE NSS Conference Record, Orlando, USA, N13-7 (2009). ** M. Kalliokoski et al., Proc. of IPAC'10, Kyoto, Japan, p.888 (2010). |
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| TUPC068 | SOLEIL Beam Orbit Stability Improvements | 1156 |
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| The electron beam orbit stability has been significantly improved at synchrotron SOLEIL. Low frequency noise sources have been localized and identified: the fans installed on the storage ring to cool down the ceramic chambers of the kickers, shaker and FCT, were slightly wobbling the electron beam orbit at 46, 50, 54 and 108 Hz. The localization method and the solutions that will allow reducing the noise from 0.8 μm RMS down to 0.3 μm are presented. Besides, a new 160 m long beamline, NANOSCOPIUM, is being installed on a canted straight section. Its photon beam position stability requirements are very tight calling for the following improvements: addition of 2 more BPMs and fast correctors in the orbit feedback loops, new INVAR stands for BPM and XBPM integrating Hydrostatic Level System sensors. The paper is also discussing other projects that did or will contribute to improving the beam orbit stability: installation of 145 temperature sensors on the storage ring, a new analog feedforward correction system for insertion devices, and the use of the bending magnet X-BPM measurements in the slow and fast orbit feedback loops. | ||
| TUPC069 | Bunch Length Measurements from the Incoherent Synchrotron Radiation Fluctuation at SOLEIL | 1159 |
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Bunch length measurements can be made by analysing the pulse to pulse intensity fluctuation of the incoherent synchrotron radiation as it has been reported elsewhere*. Such a method has been tested at SOLEIL for picosecond bunch durations, at several wavelengths and bandwidths in the visible range, using an avalanche photodiode. Thanks to the low-alpha optics the lengths of 10 μA bunches as short as 3 ps have been measured in good agreement with the streak camera results. We first used the radiation from a bending magnet, and then from a HU640 undulator that enhances the photon flux. Moreover, taking advantage of using the radiation from an undulator, we show that the method can still be used when the number of spikes emitted by the electron bunch is reduced to a few hundreds. This could be of interest for bunch length measurements of X-ray SASE FELs. Furthermore, we intend to use a single crystal diamond detector in order to perform these measurements in the X-ray range.
* F. Sannibale et al., "Absolute bunch length measurements by incoherent radiation fluctuation analysis", PRST AB 12, 032801 (2009). |
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| TUPC070 | SAFARI, an Optimized Beam Stop Device for High Intensity Beams at the SPIRAL2 Facility | 1162 |
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| The SPIRAL2 facility at GANIL-Caen is now in its construction phase, with a project group including the participation of many French laboratories (CNRS, CEA) and international partners. The facility will be able to produce various accelerated beams at high intensities: 40 MeV Deuterons, 33 MeV Protons with intensity until 5mA and heavy ions with A/Q=3 up to 14.5MeV/u until 1mA current. We will present the final status of the 200kW beam stop located in the high energy beam transport lines. From the beam characteristics (HEBT line up to beam stop) and activation constraints, we studied and developed a complete design of a new high efficiency Beam Stop that has been nicknamed SAFARI (Système Arrêt Faisceau Adapté Rayons Intenses - Optimized Beam Stop Device for High Intensity Beams). Special focus will be done on the adequacy between beam dynamic and thermo-mechanical behavior. The Beam Stop shape marries to the beam characteristics in order to smooth for the best power density and improve thermo-mechanical behavior under nominal and critical beams. Optimization by various fluids studies and calculations led us to a new high efficiency counter-current water cooling system. | ||
| TUPC072 | Accurate Electron Beam Size Measurement at the Metrology Light Source | 1165 |
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For the operation of the Metrology Light Source (MLS)*, the dedicated electron storage ring of the Physikalisch-Technische Bundesanstalt (PTB), as the national primary radiation source standard from the near infrared to the vacuum ultraviolet spectral region, all storage ring parameters which are relevant for the calculation of the radiant intensity by the Schwinger equation have to be known absolutely with small uncertainties. For the measurement of the effective vertical electron beam size a Bragg polarimeter, operating at a photon energy of 1103 eV, has been designed and put into operation. This system also serves as a detection system for the image of the electron beam through a set of narrow slits. The results obtained with the new device are compared to those measured by an optical beam imaging system**.
* R. Klein et al., Phys. Rev. ST-AB 11, 110701 (2008). ** C. Koschitzki et al., Proc. IPAC10, 894-896 (2010). |
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| TUPC073 | Emittance Variation Dependence on Resonance Extraction Parameters at ELSA | 1168 |
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Funding: Funded by the DFG within the SFB / TR 16. The Electron Stretcher Facility ELSA consists of several accelerator stages, the last one being a stretcher ring providing a beam of polarized electrons with an energy of up to 3.5~GeV. In order to guarantee a high duty cycle, a slow extraction via a third integer resonance is applied to the stretcher ring. The emittance of the extracted beam as well as the efficiency of the extraction process depend on different parameters as the sextupole strength being necessary for the excitation of the third integer resonance or the adjusted tune. In order to optimize the quality of the extracted beam, an accurate comprehension of the influence of these parameters is indispensable. Beam profiles are detected using dedicated synchrotron light monitors optimized for low intensities. The emittance was investigated by the method of quadrupole scan. The experimental studies are accompanied by numerical simulation studies. The results of the change of the emittance depending on different resonance extraction setups obtained by the experimental as well as by the theoretical studies will be presented. |
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| TUPC074 | A New Counting Silicon Strip Detector System for Precise Compton Polarimetry | 1171 |
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Funding: Supported by the German Research Foundation within the SFB/TR16 A Compton polarimeter is currently being installed at the Electron Stretcher Facility ELSA to monitor the degree of polarization of the stored electron beam. For this purpose, circularly polarized light that is emitted by a laser and backscattered off the beam has to be detected. Above all, as a result of ELSA's beam energies, it is necessary to measure the shift of the center of the photon spatial distribution which is obtained when the polarization of the laser is switched from left-hand to right-hand circular polarization with an accuracy of a few microns. In order to meet the required specifications, a new counting silicon strip detector system has been developed in cooperation with the SiLab/ATLAS group of the Physics Institute of the University of Bonn. In this contribution, the design of the system will be presented and first results will be shown. |
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| TUPC075 | Diagnostic Devices for Beam Intensity Measurement at FAIR | 1174 |
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Funding: Work supported by EU, DITANET, Project No. ITN-2008-215080. Precise determination of beam intensity is important for any accelerator facility. At FAIR, the Facility for Antiproton and Ion Research presently in the planning phase at GSI, the requirements set by beam intensities in the various accelerators, storage rings and transport lines differ significantly. A set of beam diagnostic instruments is foreseen to detect the large variety of ion beams ranging from less than 104 antiprotons up to high intensity of 5·1011 uranium ions. This contribution presents an overview of destined current measurement devices, both intercepting, like scintillators, ionization chambers or secondary electron monitors, and non-intercepting current-transformer type devices. Ongoing developments are discussed for non-intercepting devices, i.e. a dc current transformer with large dynamic range and a cryogenic current comparator, purpose-built for the detection of lowest beam intensities at FAIR. |
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| TUPC076 | Realization of a High Bandwidth Bunch Arrival-time Monitor with Cone-shaped Pickup Electrodes for FLASH and XFEL | 1177 |
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Funding: Funded by the Federal Ministry of Education and Research (BMBF): 05K10RDA In the Free Electron Laser in Hamburg (FLASH) an electro-optical system is used as a Bunch Arrival time Monitor (BAM). The time-of-arrival resolution is proportional to the steepness of the beam pick-up signal at the first zero-crossing*. Future experiments will be conducted using significantly lower bunch charges resulting in a reduced signal steepness. This requires BAM pickup electrodes with increased bandwidth as introduced in **. This paper presents the implementation and measurement results of a high bandwidth cone-shaped pickup capable of operating in the frequency range up to 40 GHz. The slope steepness at the zero crossing is investigated for a simplified equivalent circuit model. RF-measurements have been performed using a non-hermetic prototype of the BAM pickups for assessing the influence of manufacturing tolerances on the sensor performance. The measurements are compared to simulation results obtained by CST PARTICLE STUDIO®. * F. Loehl et al., Proc. of DIPAC2007, WEPB15, p. 262 (2007). ** A. Angelovski et al., "Pickup design for a high resolution Bunch Arrival time Monitor for FLASH and XFEL", DIPAC2011. |
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| TUPC077 | Investigations on High Sensitive Sensor Cavity for Longitudinal and Transversal Schottky for the CR at FAIR | 1180 |
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Funding: Funded by the Federal Ministry of Education and Research (BMBF): 06DA90351 For the Collector Ring (CR) at the FAIR (Facility for Antiproton and Ion Research) accelerator complex a sensitive Schottky sensor is required. The CR covers different modes of operation, like pre-cooling of antiprotons at 3 GeV, pre-cooling of rare isotope beams at 740 MeV/u and an isochronous mode for mass measurements. For longitudinal Schottky measurements the concept of a resonant cavity had been introduced [Hansli2011]. Due to limited space inside the ring, the integration of transversal Schottky analysis into this cavity is desired. In this paper the demands and required changes to implement also transversal Schottky measurements are discussed. An analysis of the expected signal characteristics featuring equivalent circuit is shown, as well as numerical full wave simulations of the cavity. * M. Hansli, A. Penirschke, R. Jakoby, W. Kaufmann, W. Ackermann, T. Weiland, "Conceptual Design of a High Sensitive Versatile Schottky Sensor for the Collector Ring at FAIR", DIPAC2011. |
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| TUPC078 | The Impact of the Duty Cycle on Gamma-particle Coincidence Measurements | 1183 |
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Funding: Supported by BMBF under 06DA9041I Radioactive ion beam facilities deliver a great variety of different nuclei and thus open new possibilities for gamma-ray spectroscopy with radioactive isotopes. One of the challenges for the experimentalist is the high gamma background. To obtain nearly background-free spectra a gamma-particle coincidence measurement in inverse kinematics is well suited. Also for stable beams this method offers a lot of advantages. A crucial point for experimentalists for such kind of experiments is the duty cycle and the beam structure of the accelerator. For a typical set-up, the effect of the duty cycle and beam structure, e.g. resulting from different ion-sources, on data acquisition and thus the experiment will be shown from the experimentalist's point of view. The results will be discussed for selected accelerators, i.e. UNILAC (GSI, Germany), REX-ISOLDE (CERN, Switzerland) and ATLAS (ANL, USA). |
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| TUPC079 | Sensitivity and Tolerance Analysis of a New Bunch Arrival-time Monitor Pickup Design for FLASH and XFEL | 1186 |
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Funding: Supported by the Graduate School of Computational Engineering at TU Darmstadt and the Federal Ministry of Education and Research (BMBF): 05K10RDA "Weiterentwickung eines Ankunftszeitmonitors" The Free Electron Laser in Hamburg (FLASH) is equipped with Bunch Arrival Time Monitors (BAM)*, which provide for a time resolution of less than 10 fs for bunch charges higher than 0.2 nC. Future experiments, however, will aim at generating FEL light pulses from a broad range of bunch charges down to 10 pC. In these circumstances the requirements on the time resolution will no longer be fulfilled, which demands for a larger bandwidth of the pickup system. A new cone-shaped pickup, which has a bandwidth greater than 40 GHz has been proposed**. At high frequencies, small manufacturing tolerances might have great influence on the pickup signal. A sensitivity analysis of several manufacturing tolerances in the pickup design regarding their influence on the output signal was carried out (by means of CST PARTICLE STUDIO®). These results are utilized for setting limits to the manufacturing tolerances. * M.K. Bock et al., IPAC2010, WEOCMH02, Kyoto, Japan, 2010. ** A. Kuhl et al., "Design eines hochauflösenden Ankunftszeitmonitor für FLASH", DPG Frühjahrstagung 2011, Karlsruhe, Germany. |
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| TUPC080 | Pickup Design with Beta Matching | 1189 |
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Funding: Work supported by GSI The main goal of this project is to investigate the Schottky noise of an ion beam in the frequency range from 3 to 5 GHz. In order to accomplish this task, a pickup design is required. For an efficient study of this Schottky noise the pickup sensitivity for low beta must be increased. A design for such a problem has been developed by McGinnis for a fixed beam velocity but can also be used for variable beta by using a tunable material (ferroelectric) inside the waveguide. Since such tunable materials like for instance BST (Barium Strontium Titanate) are lossy, the impact of dielectric losses on the pickup sensitivity will also be investigated in this work. Additionally to the classical parameter studies where multiple simulation runs based on the original numerical model are initiated to characterize the various design parameters it is also possible to utilize a reduced model instead. In particular one is interested in a fast evaluation of the frequency response while taking also material variations into account. In this work, a multivariate parameterized dynamical system is set up and used complementary to the full model for the required beam characterization. |
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| TUPC081 | Diagnostics of Femtosecond Low-charge Electron Bunches at REGAE | 1192 |
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| A new linac is constructed at DESY as the electron source fo "Relativistic Electron Gun for Atomic Exploration (REGAE)". REGAE is mainly established for a Femtosecond electron diffraction experiment presenting structural information on atomic transition states occurring in the sub-hundred femtosecond time-scale. REGAE comprises a photo-cathode gun followed by normal conducting 1.5 cell RF cavity to provide sub pico-Coulomb charge of 2 to 5 MeV energy with a coherent length in the range of 30nm. In order to produce and maintain such high quality electron bunches, sophisticated single-shot diagnostics is mandatory to monitor the properties. Diagnostics include emittance, energy, energy spread and bunch length measurement. In this paper the conceptual ideas and steps toward realization of these diagnostics are presented with a detailed focus on transverse diagnostics. As for photon source of transversal diagnostics, scintillators are studied. Simulation results show which material suits the best for REGAE parameters. Layout of a home-made intensified camera is presented. The method discussed in this paper would also be advantageous for low-charge Free Electron Lasers. | ||
| TUPC082 | Beam Current Measurements at the TSR Heidelberg | 1195 |
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| To conduct experiments using low energy ion beams at the TSR heavy ion storage ring, the beam deceleration process must be well understood. During deceleration of the beam the revolution frequency decreases, resulting in low current, which is difficult to measure with a common DC transformer. The number of particles in a bunch is determined by measuring the voltage signal in the time domain using a capacitive pick-up. If the ratio of bunch length and RF period does not change during the deceleration or acceleration, measuring the pick-up signal spectrum, where the signal is directly proportional to the number of particles in a bunch, is a more sensitive method. An alternative method is using a beam profile monitor (BPM) for determining the number of particles in the storage ring via ionization rate measurements of the residual gas. A summary of these different methods to determine the number of particles is presented. | ||
| TUPC083 | Comparative Studies into 3D Beam Loss Simulations | 1198 |
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Funding: Work supported by the Helmholtz Association and GSI under contract VH-NG-328. A detailed understanding and monitoring of potential beam loss mechanisms is crucial for every particle accelerator. The main motivation in low energy facilities, such as the Ultra-low energy Storage Ring (USR) at the future Facility of Low energy Antiproton and Ion Research (FLAIR), comes from the very low number of particles available which in such machine ought to be conserved. In High Energy accelerators it is the concern about activation or even physical damage of machine parts which has to be taken into serious account. The CLIC Test Facility (CTF3) at CERN provides an ideal testing ground for studies into novel BLM systems and is well suited for benchmarking the results from numerical simulations in experiments. This contribution summarizes the three-dimensional beam loss pattern as found with the commonly used codes FLUKA and Géant4. The results from these codes are compared and analyzed in detail and used for the identification of optimum beam loss monitor locations. |
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| TUPC084 | Performance of the Scintillation Profile Monitor in the COSY Synchrotron | 1201 |
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| Residual gas scintillation is used for measuring profile of the proton beam circulating in the COSY synchrotron. The problem of low rate of scintillation events detected by a multichannel photomultiplier is coped with by injecting small amounts of pure nitrogen into the SPM vacuum chamber. This leads to a temporary local pressure bump of no more than an order of magnitude. A commercially available piezo-electric dosing valve allows good control over the amplitude and duration of the pressure bump. Since the average pressure in the machine is hardly changed, the method is fully compatible with experiment operation. This approach offers a robust and inexpensive way to measure the beam profile. The design of the SPM is discussed. The latest measurement results and comparison to the ionization profile monitor data is presented. | ||
| TUPC085 | Observation of Microwave Radiation using Low-cost Detectors at the ANKA Storage Ring | 1203 |
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Funding: Work supported by the Initiative and Networking Fund of the Helmholtz Association under contract number VH-NG-320 Synchrotron light sources emit Coherent Synchrotron Radiation (CSR) for wavelengths longer than or equal to the bunch length. At most storage rings CSR cannot be observed because the waveguide cuts off radiation with long wavelengths. There are different approaches for shifting the CSR to shorter wavelengths that can propagate through the beam pipe, e.g.: The accelerator optics can be optimized for a low momentum compaction factor, thus reducing the bunch length. Alternatively, laser slicing can modulate substructures on long bunches. Both techniques extend the CSR spectrum to shorter wavelengths, so that CSR is emitted at wavelengths above the waveguide cut off. Usually fast detectors, like superconducting bolometer detector systems or Schottky barrier diodes, are used for observation of dynamic processes in accelerator physics. In this paper, we present observations of microwave radiation at ANKA using an alternative detector, a LNB (Low Noise Block) system. These devices are usually used in standard TV-SAT-receivers and are very cheap. We determined the time response of LNBs to be below 100 ns. The sensitivity of LNBs is optimized to detect very low intensity "noise-like" signals. |
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| TUPC086 | A Setup for Single Shot Electro Optical Bunch Length Measurements at the ANKA Storage Ring | 1206 |
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Funding: Supported by the Initiative and Networking Fund of the Helmholtz Association under VH-NG-320. Sponsored by the German Federal Ministry of Education and Research under contract number 05K10VKC Single shot electro optical bunch length measurements, in particular using spectral decoding, are foreseen for the ANKA storage ring. This will allow to resolve fast changes of bunch deformation and structure during the low alpha operation (2-15 ps rms bunch length). This technique uses a chirped laser pulse to probe the field induced birefringence in an electro optical crystal. The laser pulse is then analyzed in a single shot spectrometer. To obtain the birefringence modulation one can either use the near field of the electron bunch (placing the crystal close to the electron bunch in the UHV system of the storage ring), or the far field (coherent synchrotron radiation in the THz range at a THz-/IR-Beamline). The laser needs to supply: sufficient tunability of pulse length, a wide spectrum to allow for a sub-ps resolution. Additionally it must provide a mode-locked operation synchronized to the bunch revolution clock. For this purpose, a mode locked Ytterbium fibre laser system which operates at 1030 nm has been developed at the Paul-Scherrer Institute in Switzerland. We give an overview over the experimental set up in the ANKA storage ring and the status of the project. |
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| TUPC087 | Filling Pattern Measurements at the ANKA Storage Ring | 1209 |
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| For many accelerator physics studies, e.g. the investigation of coherent synchrotron radiation (CSR), a precise knowledge of the quantitative filling pattern (i.e. the number of electrons per bunch) is essential. This can be achieved by either using a linear detector (analog recording) or by employing the method of time-correlated single photon counting (TCSPC). At the ANKA storage ring both methods are in use. The analogue detection is based on the signal from a stripline or annular electrode, the TCSPC uses a Single Photon Avalanche Diode (SPAD). In this paper, we describe the experimental set-ups and present results of a comparison of the two techniques for single as well as for multi bunch filling patterns. | ||
| TUPC088 | An Ionization Profile Monitor for the Determination of the FLASH and PITZ Beam Parameters | 1212 |
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| To operate FLASH (Free-electron LASer at Hamburg) successfully, accurate measurements of the photon beam parameters, like position and profile, are essential. The development of a specific Ionization Profile Monitor (IPM) is one contribution to the photon beam diagnostics, and currently one horizontal and one vertical oriented IPM are installed at FLASH. The working principle of the IPM is based on the detection of ions generated by interactions of the photon beam with the residual gas, which is always present in the beam line. An essential advantage of this method is that the beam is not influenced by the IPM, so it is possible to analyze the beam parameters without beam destruction. Moreover, the monitor is able to determine the relative position and the spatial profile of the beam with the precision of a few um. In this poster, the design and first measurements with the IPM taken at FLASH are presented. A good measuring accuracy of the IPM is obtained. Moreover, first results of measurements at PITZ (PhotoInjector Testfacility at Zeuthen) are given for one vertical oriented IPM with a up to 25 MeV electron beam. | ||
| TUPC089 | New Digital NMR System for an Old Analyzing Magnet | 1215 |
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| The analyzing magnet of the ATOMKI cyclotron measures the beam energy with high precision and can lower its energy spread to ~5x10-4. The highly stable magnetic field is achieved by a NMR-feedback in the control loop of the power supply. The original analog system was designed and built over 25 years ago applying mainly obsolete, partly nowadays unavailable components. Maintaining and keeping the system running required increasing efforts every year. A new digital system has been developed to replace the old one. Except the high-frequency signal domain (HF oscillator and preamplifier) it performs every processing digitally. Its heart is a mixed-signal microcontroller that generates the signals for the NMR-probe, measures the amplitude and frequency of the oscillation, evaluates the demodulated signal and controls the power supply. A fast NMR-pulse detection algorithm was developed; as a result the embedded program can perform all measuring, detecting and controlling tasks in real-time. A PC connects to the controller, sends commands and displays the received signals and status data. The control software allows easy handling of the complete system with nearly automated operation. | ||
| TUPC091 | Operational Results of the Diamond-based Halo Monitor during Commissioning of SPring-8 XFEL (SACLA) | 1218 |
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Funding: This work is partly supported by Japan Society for the Promotion of Science, Grant-in-Aid for Scientific Research (c) 21604017. Measurement of electron beam halo is very important issue for X-ray free electron laser and synchrotron radiation facilities, because the beam halo may cause radiation damage of undulator magnets. Furthermore, it may cause degradation in quality of electron beam, and radio activation of beam ducts and components. In order to prevent these situations, a diamond-based halo monitor (HM) has been developed for the SPring-8 Angstrom Compact free electron LAser (SACLA). We have achieved excellent detection limit of 0.3 fC/pulse for single-shot measurement, which corresponds to the ratio of 10-6 to the beam core. The commissioning of the HM, which was installed at the upstream of 90m undulator, has been carried out, and it has been figured out that the intensity of the beam halo can be measured very nicely since secondary electrons and bremsstrahlung that are emitted in the accelerator components have not been observed. We also describe systematic profile measurements of the beam halo and operational results of the HM during the commissioning of SACLA. |
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| TUPC092 | Transverse C-band Deflecting Structure for Longitudinal Phase Space Diagnostics in the XFEL/SPring-8 “SACLA” | 1221 |
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| In SPring-8, the 8 GeV compact XFEL “SACLA” is under commissioning. A single bunch of electrons is compressed down to about 30 fs for brilliant SASE X-ray lasing. It is an important key of stable lasing to investigate the longitudinal phase space and the sliced emittance of a lasing part of the bunch by using a transverse RF deflector. We developed a high gradient C-band deflecting structure operated at 5712 MHz for the bunch diagnosis with a resolution of femtosecond regime at a limited space in the SACLA. The backward travelling-wave of the HEM11-5pi/6 mode is excited in the cylindrical structure periodically loaded with racetrack-shaped irises. The featuring irises suppress rotation of the deflection plane and generate strong cell-to-cell coupling for stable resonance. Two 1.8m-long structures were fabricated and installed in the SACLA. They successfully generated a deflection voltage over 40 MV and pitched the bunch at the zero-crossing RF phase. In this paper, we present the details of the fabrication and the deflecting performance of the structures applied to the diagnosis. | ||
| TUPC093 | CSR Bunch Length Monitor for XFEL/SPring-8 - SACLA | 1224 |
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| SPring-8 Angstrom Compact Free Electron Laser (SACLA) is now under commissioning operation, aimed at the generation of a sub-angstrom free electron laser (FEL). In order to ensure the stable FEL generation, non-distractive bunch length monitors utilizing coherent synchrotron radiation (CSR) are installed. The monitors are located at the downstream of individual bunch compressor (BC1-BC3), and they measure the radiation emitted at the individual last magnets of the chicanes. At the magnets, beams with bunch lengths form 10 fs to 1000 fs generate the CSRs with a spectrum ranging the almost whole infrared region (0.03 - 3 THz). The CSRs are detected by a Schottky diode at the BC1, or pyroelectric detectors and a simple organic lens optical system at BC2 and 3. The bunch length monitor systems are used for bunch length feedback control to obtain the stable lasing by changing the rf parameter of acceleration cavities before the BCs. A preliminary system for the above mentioned system was tested at the SCSS test accelerator, and it showed sufficient performance to measure bunch length up to 300 fs. In this report, we describe the design and the results of the first operation. | ||
| TUPC094 | Development of High-speed Differential Current-transformer Monitor | 1227 |
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| The XFEL, which was named SACLA, was constructed in the SPring-8 site. In the SACLA, the bunch length of an electron beam is compressed from 1 ns to 30 fs, and the beam charge is decreased to obtain a genuine electron beam from 1nC to 0.3 nC for lasing. A new current-transformer (CT) monitor, which should measure the charge of the electron beam and make bunch length observation in velocity bunching process, was developed with two advantageous properties. One is differential output signal which suppresses common-mode noise from the thyratron of a klystron modulator by a factor of ten. Another property is high-speed signal output which provides a possibility to measure the bunch length and the time-of-flight (TOF) at the injector part of the SACLA. The output signal has 200 ps rise-time and a pulse width of 400 ps (FWHM) for an impulse beam. We successfully observed the bunch length between 1 ns and 400 ps around a 238 MHz buncher cavity. Moreover, we measured the TOF between two CTs with a few picoseconds resolution for a low-energy beam around 1 MeV. Thus, the new CT performance was confirmed to be sufficient for the SACLA. | ||
| TUPC095 | Bucket-by-bucket On/Off-axis Injection with Variable Field Fast Kicker | 1230 |
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| Dynamic aperture of ultra-low emittance storage rings is expected to be as small as a few mm; one order smaller than that of current rings, because of their high nonlinearity. The conventional injection scheme with bump formation may not be applied for such small aperture. On-axis injection with fast magnet is one of the solutions, however, it requires the injection beam of long trains of bunches, which impose serious limitation on the injector and the filling pattern. We propose a bucket-by-bucket on-axis/off-axis injection scheme, which manipulates the injection and stored beams bucket-by-bucket with a variable field fast kicker. For on-axis injection, this scheme eliminates the limitation on injectors and filling pattern, and also it can reject the contaminated electrons from the injector to keep the bunch purity. Those advantages allow the SPring-8 XFEL low emittance linac to be an injector matched with ultra-low emittance rings like the SPring-8 II: upgrade plan of SPring-8. By changing the drive power to the kicker, it can also produce position dependent kick required for the off-axis injection, with minimal perturbation on the stored beam achieved by bucket-by-bucket scheme. | ||
| TUPC096 | Solid-state Marx Generator Driven Einzel Lens Chopper | 1233 |
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A new type of pulse chopper called an Einzel lens chopper* is described. The Einzel lens, placed immediately after an electron cyclotron resonance ion source, is driven by high-voltage pulses generated by a newly developed solid-state Marx generator. A rectangular negative barrier pulse-voltage is controlled in time. The barrier pulse is switched on only when a beam pulse is required. When the barrier pulse is off, the DC voltage across the Einzel lens reflects ions back upstream with almost zero velocity. The device has been actually used as a chopper for the KEK Digital Accelerator, which is a small-scale induction synchrotron employing no a large injector and capable of providing a wide variety of ions, has been constructed at KEK**. A He ion beam of 50 micro-ampere was chopped in 5 micro-sec with rise/fall time of 40 nsec.
* T.Adachi et al., “A Solid-State Marx Generator Driven Einzel Lens Chopper”, submitted to Appl. Phys. Lett. ** T. Iwashita et al., “KEK Digital Accelerator”, Phys. Rev. ST-AB, published in 2011. |
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| TUPC097 | Status of Cold Cavity Beam Position Monitor for STF | 1236 |
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| Cold cavity BPM was developed to meet high position resolution and bunch to bunch measurement time. It is designed based on re-entrant cavity and has Low-Q to achieve short signal decay time in L-band frequency with large aperture as 78mm. The beam test was performed to demonstrate position resolution at ATF main linac, which is operating with 1.6nC bunch charge, while BPM will be installed inside the ILC cyomodule with 3.2nC spacing 369ns like as ILC at STF. Stripline BPMs, ML2P and ML3P installed upstream and downstream of the BPM’s location respectively were used to predict its position. Reference cavity was optimized to use for synchronous detection. We had achieved ~340nm position resolution since position resolution was estimated due to limitation of system with noise, namely in case of ideal state. We will present configuration of beam test, procedure to measure position resolution and the result on the test. Furthermore, new design will be introduced to improve signal intensity and have heavy coupling. | ||
| TUPC098 | Beam Profile Measurement using Flying Wire Monitors at the J-PARC Main Ring* | 1239 |
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| Transverse beam profiles have been measured using flying wire monitors at the main ring of the Japan Proton Accelerator Research Complex (J-PARC). The flying wire is a beam profile monitor using a thin carbon fiber as a target. The beam is scanned with the wire target at the maximum speed of 5 m/s. The secondary particles from the beam-wire scattering are detected using a scintillation counter as a function of the wire position. The measurement has revealed a characteristic temporal change of the beam profile during the injection period of 120 ms. A multiparticle tracking simulation program, SCTR, taking account of space charge effects has successfully reproduced the beam profiles. | ||
| TUPC099 | New Measurements of Proton Beam Extinction at J-PARC | 1242 |
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| Proton beam extinction, defined as a residual to primary ratio of beam intensity, is one of the most important parameters to realize the future muon electron conversion experiment (COMET) proposed at J-PARC. To achieve the required extinction level of 10-9, we started measuring extinction at main ring (MR) as its first step. According to the various measurements done at the different positions, empty RF buckets of RCS, which were considered to be swept away by the RF chopper, contained about 10-7 ~ 10-5 of the main beam pulse due to chopper inefficiency. We have developed a new beam monitor with improved performance for further studies at the abort line. In addition, we have started new measurements at the Hadron experimental hall by using slow-extracted beam. In this paper, we present recent results and future prospect of beam extinction measurements. | ||
| TUPC100 | Longitudinal Beam Profile Measurement at J-PARC Separated Drift Tube Linac | 1245 |
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| We measured longitudinal beam profile at Separated Drift Tube Linac (SDTL) injection part by scanning beam transmission and beamloss at the downstream of SDTL section by changing SDTL injection phase. As the beam goes to acceptance edge, part of the beam which is out of acceptance isn't accelerate and finally it is lost by hitting to beam duct. Thus beam transmission shows sliced bunch shape by acceptance edge, it is possible to reconstruct the beam bunch shape. The result shows about 60% wider profile in both phi and E direction against to design. | ||
| TUPC101 | Generation of Multimode Quasi-monochromatic Terahertz | 1248 |
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| Generation of quasi-monochromatic terahertz (THz) using multimode Coherent Cherenkov Radiation (CCR) on the order of 0.1 THz was investigated. CCR was generated by a hollow dielectric tube covered by a metal and an electron bunch from a photocathode radio-frequency (RF) gun linac. The intensity and frequency of CCR were measured directly by a Michelson interferometer and a bolometer. The frequency spectra measured by the interferometer indicated sharp peaks close to frequencies of 0.09 THz and 0.14 THz, which corresponded to TM03 and TM04 modes, respectively, according to theoretical calculation for a tube with inner and outer radii of 5 mm and 7 mm. The maximum gain of TM03 mode due to the tube length was obtained as 1.5 dB/cm. The other higher modes, e. g. 0.36 THz (TM09) and 0.40 THz (TM010), were also observed from a 150 mm long tube at a bunch charge of 15 pC, which decreased space charge effect and the bunch length. Finally, a new method for bunch diagnostic based on multimode CCR was proposed. The bunch length was estimated to be 0.45 ps at a bunch charge of 5 pC with the intensity ratio of TM03 to TM09 mode. | ||
| TUPC102 | Measurement of Beam Loss Tracks by Scintillating Fibers at J-PARC Linac | 1251 |
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| Highest beam loss in the J-PARC linac has been observed that the ACS (Annular-Coupled Structure linac) section. Since the observed beam loss is proportional to the residual gas pressure, the source of the beam loss is considered as H0 produced in an interaction of H− beams with remnant gas. If this assumption is valid, H0 hits the beam duct and changes into H+ and escapes from the beam duct. We constructed scintillation fiber hodoscopes to detect H+s and eventually identify the particle species as H+. The hodoscopes are made of 4 planes of hodoscopes which consists of 16 scintillation fibers of 64mm long and with 4mmx4mm cross section. We installed the hodoscopes at the upstream part of the ACS section and measured beam loss. The results are shown in this paper. | ||
| TUPC103 | Monitoring of the Betatron Tune and Amplitude at Multi-batch Injection of J-PARC MR | 1254 |
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| The beam power of J-PARC Main Ring Synchrotron (MR) increased gradually from 2008, and came to be able regularly to supply the beam of 145kW February, 2011. Many of current beam losses are localized to the collimator located on the injection section. One of the problems of the beam injection is that the orbit of the beam transportation line is unstable. It causes sometimes large transverse injection error. Because the transverse injection error is essentially proportional to the amplitude of the betatron oscillation, it is possible to observe by measuring the turn-by-turn position for every bunch of injected beam by using BPMs located on the injection section. In this report, it is described the method how to measure injection error from beam position. It is also discussed about the effect of reflection wave of injection kicker magnets. | ||
| TUPC104 | Beam Loss Detected by Scintillation Monitor | 1257 |
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| Ar gas proportional BLMs have measured the beam loss through operations, but they are also sensitive to background noise of X-ray emitted from RF cavities. We have tried to measure the beam loss using scintillation monitors which would bring more accurate beam loss measurements with suppression of X-ray noise. We measured beam loss using scintillation beam loss monitors. Because this scintillation BLM is sensitive for low energy gamma-rays and fast neutrons, small signals from X-rays would be also detected. As the measurement results, a good signal to noise ratio is observed for the scintillation monitor with quite low sensitivity to the background X-ray. And many single events are observed in the intermediate pulse bunch with about 600 ns as pulse width. In addition, because we fabricated the filter and integrated circuit, total amount of X-ray noise can become smaller. We obtained the good performances of scintillation BLM with small effect of X-ray noise. This monitor can be used for beam loss measurement and a knob for tuning. Furthermore, because the detail structure can be detected, this monitor could be employed for another diagnostic device. | ||
| TUPC105 | Improvement of Beam Current Monitor with High Tc Current Sensor and SQUID at the RIBF | 1260 |
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| A highly sensitive beam current (position) monitor with a high Tc (Critical Temperature) current sensor and a SQUID (Superconducting QUantum Interference Device), that is the HTc-SQUID monitor, has been developed for the RIBF (RI Beam Factory) in RIKEN. The purpose of our work is to measure the DC of high-energy heavy-ion beams nondestructively in such a way that the beams are diagnosed in real time and the beam current extracted from the cyclotron can be recorded without interrupting the beam user's experiments. Both the HTc magnetic shield and the HTc current sensor were dip-coated by thin layer of Bi-Sr-Ca-Cu-O (2223-phase, Tc=106 K) on 99.9 % MgO ceramic substrates. Unlike other existing facilities, all these HTS fabrications are cooled by a low-vibration pulse-tube refrigerator. These technologies enable us to downsize the system. As a result, 1 uA Xe beam intensity (50 MeV/u) was successfully measured with a 100 nA resolution. From last year, aiming at the higher resolution, improvement of the new HTc current sensor with two turn coils has been started. We will report the present status and the measurement results of the HTc-SQUID monitor. | ||
| TUPC106 | Courant-Snyder Invariant Density Screening Method for Emittance Analysis | 1263 |
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| The emittance is an important characteristic of describing charged particle beams. In hadron accelerators, we often meet irregular beam distributions that are not appropriate to be described with a single rms or 95% or total emittance. In many cases beam halo should be described with very different Courant-Snyder parameters from the ones for beam core. A new method – Courant-Snyder invariant density screening method is developed for analyzing emittance data clearly and accurately. The method treats emittance data from both measurements and numerical simulations. The method uses the statistical distribution of the beam around each particle in phase space to mark its local density parameter, and then uses the density distribution to calculate the beam parameters such as Courant-Snyder parameters and emittance for different beam boundary definitions. The method has been used in the calculations for the beams from difference sources, and shows its advantages over other methods. An application code based on the method including the graphic interface has also been designed using the Matlab software. | ||
| TUPC107 | Some Preliminary Experiments using LIBERA BPMs in BEPCII* | 1266 |
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Funding: Supported by the National Natural Science Foundation of China (10805051) There are total 16 LIBERA BPMs in BEPCII, which is a double ring e+e− collider. The turn-by-turn BPMs serve as only tune measurement system in most cases during normal operation. We tried to do some more machine study using them: the local coupling parameter at the BPM, the resonance driving term, the decoherence parameter which could be used to calibrate the strength of octupole in the ring. We also compare the difference from the different exciting method: single time kick with injection kicker or sinusoidal kick with feedback system. |
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| TUPC108 | Beam Diagnostics Based on Higher Order Mode for High Repetition Beam | 1269 |
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| The signals from the HOM ports on superconducting cavities can be used as beam position monitors. The HOM amplitude of dipole mode is proportional to the beam offset. For high repetition bunches operation, the spectrum is consist of the HOMs peaks and the peaks which is integer times of the bunch repetition. The HOMs amplitudes should be separated from the two kinds of peaks. Based on the simulation from a TESLA 2-cell cavity, the transform matrix between the HOMs amplitudes and beam offsets has been found, as well as the cavity axis. The simulation results have demonstrated that beam diagnostics based on HOMs is feasible while high repetition bunches operation. | ||
| TUPC109 | Electron Bunch Slice Emittance Measurement with the Space Charge Effects* | 1272 |
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Funding: supported by the National Natural Science Foundation of China (Grant Nos. 10735050, 10805031, 10875070 and 10925523), and the National Basic Research Program of China (Grant No. 2007CB815102). Since slice transverse emittance of the electron beam is critical to a high-gain short-wavelength FEL, its characterization is very important. For space charge dominated electron beam, conventional emittance measurement techniques, such as solenoid scanning and quadruple scanning, without considering space charge forces lead to large errors of emittance evaluations. This essay introduces a modified solenoid-scan method of slice emittance measurement for space charge dominated beam, and simulations show that the new method brings the emittance evaluations much closer to actual values. |
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| TUPC110 | Ultrashort Bunch Train Longitudinal Diagnostics using RF Deflecting Structure | 1275 |
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| Ultrashort electron bunch train has been produced using UV laser stacking in Tsinghua University. With an S-band deflecting cavity inserted into the Tsinghua Thomson Scattering beamline, it is possible to characterize the bunch train longitudinal property. This paper briefly introduced the measurement layout in our lab and reported the recent experiment results, including bunch train profile measurement and longitudinal phase space. The main sources of error are also discussed. | ||
| TUPC111 | Design of Cavity Beam Monitor at HLS | 1278 |
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Funding: Work supported by the Natural Science Foundation of China, National “985 Project”, China Postdoctoral Science Foundation and “the Fundamental Research Funds for the Central Universities” X-FEL requires precious control of beam position and transverse emittance. Non-destructive on-line beam diagnostic methods are required. During the upgrading of HLS a high brightness injector based on photocathode RF electron gun, which can also be used to study FEL, is installed. The cavity beam monitor system designed for the HLS photocathode RF electron gun consists of a cavity beam position monitor and a beam quadrupole moment monitor system. The cavity beam position monitor uses a re-entrant position cavity tuned to TM110 mode as position cavity and cut-through waveguides to suppress the monopole signal. Cold test results showed that position resolution of prototype BPM is better than 3 μm. Beam quadrupole moment monitor system consists of a square pill-box quadrupole moment cavity, a cylindrical pill-box reference cavity, a waveguide coupling network and a superheterodyne receiver used as front-end signal processing system. The whole system works at 5.712 GHz. Strength of quadrupole magnets is adjust to construct a matrix which can be used to work out beam parameters. |
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| TUPC112 | Photon Beam Position Monitor based on Position-sensitive Detector for HLS* | 1281 |
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| In order to overcome the limitation that the existing photon beam position monitors (PBPM) cannot measure the beam position in vertical and horizontal at the same time, a new photon beam position monitor based on position-sensitive detector (PSD) has developed at HLS (Hefei Light Source). The new PBPM based on the PSD has very fast response speed, high sensitivity and wide dynamic range. This PBPM system also includes the C4674 signal processing circuit, NI USB-9215 data acquisition device and the LABVIEW data acquisition program. This PBPM system has been calibrated vertically and horizontally on-line, then has been applied in the beam line B3EA of HLS to measure the position of the synchrotron light. Some results are given. | ||
| TUPC115 | Application of Libera Brilliance Single Pass at NSRL Linac BPM System | 1284 |
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| Libera Brilliance Single Pass is a digital beam position processor with capabilities of single pass position measurement. This device can be used on the stripline beam position monitor (BPM) of the linac and transfer lines on light sources as well as injector system for the FELs. The linac of Hefei light source (HLS) was equipped with 2 stripline beam position monitors, which will be increased to 20 BPMs after upgrading. The existing BPM electronics were the homemade electronics with logarithm detector. To enhance the functionality of the BPM system, the Libera Brilliance Single Pass is employed to replace the existing BPM electronics. The newly buying devices have made test of characterization. The mapping of stripline BPM is made on a workbench with Libera Brilliance Single Pass. The beam position is tested at linac using Libera Brilliance Single Pass. And the results of these measurement performed on Libera are reported to compared to measurements with the linac’s existing BPM electronics. | ||
| TUPC116 | Beam Diagnostics Global Data Warehouse Implementation and Application at SSRF* | 1287 |
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| A fully functional beam diagnostics system has been developed at SSRF serving user operation and machine study since 2009. Global orbit disturbances, BPM failures and DCCT noise signal have been observed randomly. Without correct event trigger it is hard to capture real time data and analyze the cause of the above failures. A BI global data warehouse has been implemented as a solution to buffer online data and do correlation analyze at SSRF. | ||
| TUPC117 | Embedded EPICS IOC Data Acquisition System for Beam Instability Research | 1290 |
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Funding: This research is supported by National Natural Science Fund(No.Y155131061). To be a part of beam diagnostics system in SSRF 3.5 GeV electron storage ring, a high performance oscilloscope is introduced to build a bunch by bunch data acquisition and processing dedicated system, which is mainly used to observe individual bunch position in transverse plane and bunch charge. By analysis of Betatron oscillation amplitude distribution and corresponding filling pattern, we hope to find phenomenon about multi-bunch Wakefield effect[1] on beam Betatron oscillation for beam instability research. The system is configured as a scope IOC, and integrated into the EPICS based control system. Application of this system and some data analysis results are also discussed in this paper. |
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| TUPC118 | Test Results on Beam Position Resolution for Low-Q IP-BPM at KEK-ATF2 | 1293 |
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| We have performed the beam tests on the beam position resolution for the Low-Q IP-BPM (Interaction Point-Beam Position Monitor) at ATF2 which is an accelerator test facility for the International Linear Collider. The main goals of KEK-ATF2 are to achieve beam size of 37 nm and beam resolution of nano-meter for beam stabilization. Resolution tests for the Low-Q IP-BPM were performed with KEK BPM doublet in Jan. 2011. We got the results of beam position resolution 70 nm during the experimental periods and will present the detailed experimental procedures and results. | ||
| TUPC119 | A Comprehensive Study of Nanometer Resolution of the IPBPM at ATF2* | 1296 |
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Funding: Work supported in part by Department of Energy Contract DE-AC02-76SF00515. High-resolution beam position monitors (IPBPMs) have been developed in order to measure the electron beam position at the focus point of ATF2 to a few nanometers in the vertical plane. To date, the IPBPM system has operated in test mode with a highest demonstrated resolution of 8.7 nm in the ATF extraction line during 2008. After expected noise source calculations there still remains 7.9 nm of noise of unexplained origin. We summarize the experimental work on the IPBPM system since this measurement and outline the possible origins of these sources. We then present a study plan to be performed at the ATF2 facility designed to identify and to improve the resolution performance and comment on the expected ultimate resolution of this system. |
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| TUPC121 | Development of MCP Based Photon Detectors for the European XFEL | 1299 |
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| To provide successful operation of SASE XFEL the radiation detectors should operate in wide dynamic range from the level of spontaneous emission to the saturation level, in wide wavelength range from 0.05 nm to 0.16 nm for SASE1 and SASE2 and from 0.4 nm to 4.4 nm for SASE3. High relative accuracy of measurements is crucial for detection of a signature of lasing, tuning of amplification process, and characterization of statistical properties of the radiation. The XFEL radiation detector based on micro-channel plates (MCP) meets these requirements. Two types of the photon detector are used for measurements of the pulse radiation energy and the image of the photon beam. The dynamic range of photon pulse energies is between 1 nJ and 10 mJ. This applies to spontaneous and FEL radiation. The relative accuracy of pulse energy measurements is better than 1%. The visualization of a single bunch in a train, or average image over the full train will perform by the MCP imager at a spatial resolution of 30 μm. | ||
| TUPC122 | Use of a Grid Waveguide for Particle Energy Determination | 1302 |
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Funding: The Education Agency of Russian Federation and the Russian Foundation for Basic Research (09-02-00921). We consider prospect of use of a grid waveguide for determination of energy of charge particles in bunches. The method under consideration is based on measurement of a waveguide mode frequency. Earlier we developed two variants of this method*. One of them is based on use of a thin dielectric layer in a waveguide. Other variant is based on use of a waveguide loading with a system of wires coated with a dielectric material. In this paper we offer a new version of the method under consideration. It consists in application of a circular waveguide having a grid wall instead a solid one. The grid cells are assumed to be small. The particle bunch moves along the waveguide axis. The analytical solution of the problem is obtained by means of the averaged boundary conditions. It is shown that there is the single propagating mode. The main advantage of the method consists in an enough strong dependency of particle energy on the mode frequency in some wide frequency range. Note as well that this structure is easy for manufacture and can be embedded in the accelerator channel without big difficulty. * A.V.Tyukhtin et al., PAC’07, p.4156; A.V. Tyukhtin, EPAC’08, p.1302; A.V. Tyukhtin, Tech. Phys. Lett. 35, p.263 (2009); A.V. Tyukhtin et al., IPAC’10, p.1071. |
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| TUPC123 | Evaluation of New Generation Heavy Particle Beam Diagnostics Instrumentation | 1305 |
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| Abstract: This paper presents the achievements in the field of heavy particle beam diagnostics instrumentation. Two different instruments are presented: Libera Single Pass H and Libera Hadron, designed for linear and circular heavy particle beam diagnostics applications respectively. Beside high precision beam position measurement application, these instruments offer much more. Accurate beam arrival time measurements, high resolution single bunch position and charge measurements, beam current and fill pattern measurements are performed. The instruments are evaluated through extensive laboratory measurements, on the real beam and on stepper-motor driven test-benches. Libera instruments are network attached devices, developed on uTCA based platform that enables smooth integration of many instruments in the control system network and a simplified implementation of custom signal processing algorithms. | ||
| TUPC124 | Laser Wire Emittance Measurement Line at CLIC* | 1308 |
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| A precise measurement of the transverse beam size and beam emittances upstream of the final focus is essential for ensuring the full luminosity at future linear colliders. A scheme for the emittance measurements at the RTML line of the CLIC using laser-wire beam profile monitors is described. A lattice of the measurement line is discussed and results of simulations of statistical and machine-related errors and of their impact on the accuracy of the emittance reconstruction are given. Modes of operation of the laser wire system and its main characteristics are discussed. | ||
| TUPC125 | Test of the Front-end Electronics and Acquisition System for the LIPAC BPMs | 1311 |
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Funding: Work partially supported by Spanish Ministry of Science and Innovation under project AIC10-A-000441 and ENE2009-11230. Non-interceptive Beam Position Monitors pickups (BPMs) will be installed along the beamlines of the IFMIF/EVEDA linear prototype accelerator (LIPAC) to measure the transverse beam position in the vacuum chamber in order to correct the dipolar and tilt errors. Depending on the location, the BPMs response must be optimized for a beam of 175 MHz bunch repetition, an energy range from 5 up to 9 MeV, a current between 0.1 and 125 mA and continuous and pulse operation. The requirements from beam dynamics for the BPMs are quite stringent, aiming for the position an accuracy below 100 μm and a resolution below 10 μm, and for the phase an accuracy below 2° and a resolution below 0.3°. To meet these specifications, the BPM electronics system developed by ESS-Bilbao has been adapted for its use with the BPMs of LIPAC. This electronics system is divided in an Analog Front-End unit, where the signals are conditioned and converted to baseband, and a Digital Unit to sample them and calculate the position and phase. The electronics system has been tested at CIEMAT with a wire test bench and a prototype BPM. In this contribution, the tests performed will be fully described and the results discussed. |
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| TUPC126 | Indirect Measurement of Power Deposition on the IFMIF/EVEDA Beam Dump by means of Radiation Chambers | 1314 |
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Funding: Work partially supported by Spanish Ministry of Science and Innovation under project AIC10-A-000441 and ENE2009-11230 The beam stop of the IFMIF/EVEDA accelerator will be a copper cone receiving a total power of ~1 MW, coming from 9 MeV D+ at 125 mA. The mechanical stresses in this beam dump come mainly from the thermal gradients generated in the cone, being therefore related with the power deposition profile. Anomalous situations such as beam misalignments or incorrect focusing can lead to variations in this profile outside the normal operation range. These variations must be detected and corrected for beam dump protection. Due to the interaction between D+ and the copper cone important neutron and gamma fluxes are generated around the beam dump (1010 – 1011 n/cm2/s, 1010 p/cm2/s) with a spatial profile which is directly linked to the power deposition. In this work, a diagnostic based on a set of radiation chambers is proposed to measure on-line this radiation field, giving indirect information about the power deposition on the beam dump. The sensitivity of the radiation field to the power deposition profile is demonstrated and the diagnostic strategy explained, establishing the main specifications and requirements of the detectors. |
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| TUPC127 | Optical Transition Radiation System for ATF2 | 1317 |
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Funding: Funding Agency: FPA2010-21456-C02-01 Work supported in part by Department of Energy Contract DE-AC02-76SF00515 In this paper we present the first measurements performed during the fall 2010 and early 2011 runs. Software development, simulations and hardware improvements to the Multi-Optical Transition Radiation System installed in the beam diagnostic section of the Extraction (EXT) line of ATF2 are described. 2D emittance measurements have been performed and the system is being routinely used for coupling correction. Realistic beam simulations have been made and compared with the measurements. A 4D emittance procedure, yet to be implemented, is also discussed. A demagnifier lens system to improve the beam finding procedure has been designed and will be implemented in a future run. Finally, we discuss further verification work planned for the next run period of ATF. |
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| TUPC128 | Transverse Beam Jitter Propagation in Multi-bunch Operation at ATF2 | 1320 |
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| Pulse-to-pulse orbit jitter, if not controlled, can drastically degrade the luminosity in future linear colliders. The second goal of the ATF2 project at the KEK accelerator test facility is to stabilize the vertical beam position down to approximately 5% of the nominal rms vertical beam size at the virtual interaction point (IP). This will require control of the orbit to better than 1 micrometer at the entrance of the ATF2 final focus system. In this paper, by means of computer simulations, we study the vertical jitter propagation along the ATF2 from the start of the extraction line to the IP. For this study pulse-to-pulse vertical jitter measurements using three stripline beam position monitors are used as initial inputs. This study is performed for the case of a bunch-train with three bunches, but could easily be extended for a larger number of bunches. The cases with and without intra-train orbit feedback correction in the extraction line of ATF2 are compared. | ||
| TUPC129 | A Beam Position System for Hadrontherapy Facilities | 1323 |
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Funding: MICINN-FPA:AIC10-D-000518 Essential parts of the needed instrumentation for the beam control in the Hadrontherapy accelerators are the Beam Position Monitors (BPM). The measurement of the beam position in Hadronterapy accelerators become more important at the secondary transport lines towards the patient room where this parameter must be completely determined. The BPM described in this paper is a new type of BPM based on four scintillating fibers coupled to four photodiodes to detect the light produced by the fibers when intercepting the beam. We present here the study of the different photodiodes able to read the light emitted by the scintillating fiber, the tests performed in order to find the most suitable photodiode to measure the beam position from the variations in the beam current, the mechanical design and the corresponding acquisition electronics. |
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| TUPC130 | Beam Test Performance of the Beam Position Monitors for the TBL Line of the CTF3 at CERN | 1326 |
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Funding: Funding Agency: FPA2010-21456-C02-01 A series of Inductive Pick-Ups (IPU) for Beam Position Monitoring (BPM) with its associated electronics were designed, constructed and tested at IFIC. A full set of 16 BPMs, so called BPS units, were successfully installed in the Test Beam Line (TBL) of the CLIC Test Facility (CTF3) at CERN. In this paper we present the results of the beam test carried out on the BPS units of the TBL in order to determine their beam performances and check the specified operational requirements. We focus particularly on the position resolution parameter which is the BPS figure of merit according to TBL demands and is expected to reach the 5um resolution at maximum beam current (28A). The beam test results of the BPS units are also compared with the parameters from their previous characterization test at lab. |
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| TUPC131 | Overview of ESS Beam Loss Monitoring System | 1329 |
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| European Spallation Source (ESS) is a multi-MW proton linear accelerator that will be built in Lund, Sweden. Due to the high power of the machine, losses need to be minimized to avoid damaging the accelerator components and quenching superconducting magnets. Loss monitors have to be positioned all across the accelerator, so that they form a reliable protection system. A careful analysis of the loss nature for ESS is in progress to determine the locations for the loss detectors. This paper presents preliminary results of the simulations for the detector response functions, which are calculated for several different energies and incident angles of protons, at certain parts of the accelerator. A simple, baseline geometry configuration is used in the calculations. This paper also gives an overview of the considered ESS beam loss monitoring system. It describes the types of the detectors which are planned to be used at ESS, and discusses the number of detectors needed along different parts of the machine. As planned, a primary tool for measuring losses at ESS will be ionization chambers, the conceptual design of which is given in this paper based on the response time considerations. | ||
| TUPC132 | Imaging of the MAX III Electron Beam Profile Using Visible Synchrotron Radiation | 1332 |
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| The recently assembled MAX III diagnostic beam line utilizes the bending magnet synchrotron radiation (SR) in the visible to ultraviolet range to form images of the transverse electron beam profile. Computer simulations model the generation and propagation of the SR through the beam line, taking into account effects such as diffraction, the longitudinally distributed source point and the curvature of the electron orbit. Using the diagnostic beam line, the electron beam size and the emittance in the MAX III synchrotron light source has been determined. | ||
| TUPC133 | Instrumentation for the 12 GHz Stand-alone Test-stand to Test CLIC Acceleration Structures | 1335 |
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| Vacuum breakdown is one of the primary limitations in the design and construction of high energy accelerators operating with warm accelerating structures (ACS) such as CLIC linear collider because the mechanisms that cause the breakdown are still a mystery. The ongoing experimental work is trying to benchmark the theoretical models focusing on the physics of vacuum breakdown which is responsible for the observed discharges. The CLIC collaboration is preparing a dedicated 12 GHz test-stand to observe the characteristics of the RF discharges and their eroding effects on the ACS. The instrumentation for the test-stand must be versatile and allow for the conditioning of the ACS with measurements of the breakdown rates at different power levels as well as detection of the dark current and light emission directly relevant to breakdown physics. For that purpose we are developing 2 novel instruments. A pepper-pot chamber with an external magnetic spectrometer for measurement of the spatial and energy distributions of the electrons emitted from the ACS and an optical laser system for probing the ACS to observe the effect of a discharge on the transmitted light. | ||
| TUPC134 | Phase Detection Electronics for CLIC | 1338 |
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| The Compact Linear Collider (CLIC) requires very tight RF phase synchronisation in order to preserve high luminosity. The electronics required for processing the signals delivered from the phase pick-ups present a significant challenge. This paper discusses the strategy adopted to achieve a sufficiently accurate measurement of the phase. Performance measurements performed in the lab of some of the sub-systems are also presented. | ||
| TUPC135 | Beam Loss Monitors Comparison at the CERN Proton Synchrotron | 1341 |
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| CERN is planning the renovation and upgrade of the beam loss detection system for the Proton Synchrotron (PS). Improved performance in speed–to be able to monitor beam loss on a bunch-by-bunch basis–and in long-term stability–to reduce or avoid the need for periodic calibration–are aimed for. To select the most suitable technology, different detectors were benchmarked in the machine with respect to the same beam loss. The characteristics of the different detectors, the results of the measurement campaign and their suitability as future monitors for the PS are presented. | ||
| TUPC136 | Analysis of Fast Losses in the LHC with the BLM System | 1344 |
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| About 3600 Ionization Chambers are located around the LHC ring to detect beam losses that could damage the equipment or quench superconducting magnets. The BLMs integrate the losses in 12 different time intervals (from 40 us to 83.8 s) allowing for different abort thresholds depending on the duration of the loss and the beam energy. The signals are also recorded in a database at 1 Hz for offline analysis. During the 2010 run, a limiting factor in the machine availability were sudden losses appearing around the ring on the ms time scale and detected exclusively by the BLM system. It is believed that such losses originate from dust particles falling into the beam, or being attracted by its strong electromagnetic field. This document describes some of the properties of these "Unidentified Falling Objects" (UFOs) putting special emphasis on their dependence on beam parameters (energy, intensity, etc). The subsequent modification of the BLM beam abort thresholds for the 2011 run that were made to avoid unnecessary beam dumps caused by these UFO losses are also discussed. | ||
| TUPC137 | UFOs in the LHC | 1347 |
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| One of the major known limitations for the performance of the Large Hadron Collider are so called UFOs (”Unidentified Falling Objects”). UFOs were first observed in July 2010 and have since caused numerous protection beam dumps. UFOs are thought to be micrometer sized dust particles which lead to fast beam losses with a duration of about 10 turns when they interact with the beam. In 2011, the diagnostics for such events was significantly improved which allows estimates of the properties, dynamics and production mechanisms of the dust particles. The state of knowledge and mitigation strategies are presented. | ||
| TUPC139 | Overview of the CLIC Beam Instrumentation | 1350 |
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| Driven by beam dynamic considerations the Compact Linear Collider (CLIC) is expected to require extremely tight tolerances on most beam parameters. An important milestone was reached in 2011 with the completion of the CLIC conceptual design report. In this context the requirements for CLIC beam instrumentation has been reviewed and studied in detail for the whole accelerator complex with the aim of demonstrating feasibility. A preliminary choice has been made for every CLIC instrument, serving as a baseline scenario for the next phase of the project which will concentrate on the detailed design, engineering and test of CLIC devices. Whenever possible existing solutions have been studied, focusing on any improvements necessary to meet the CLIC performance criteria. When no such devices exists, or if cost considerations come into play, new technologies have been under study. Several prototypes are already well advanced and are currently under test. This paper presents an overview of CLIC beam instrumentation, the possible reach of their performance and an outlook on future developments. | ||
| TUPC141 | LHC Beam Loss Pattern Recognition | 1353 |
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| One of the systems protecting CERN's Large Hadron Collider (LHC) is the Beam Loss Monitoring system (BLM). More than 3600 monitors are installed around the ring. The beam losses are permanently integrated over 12 different time intervals (from 40 microseconds to 84 seconds). When any loss exceeds the thresholds defined for the integration window, the beam is removed from the machine. Understanding the origin of a beam loss is crucial for machine operation, as it can help to avoid a repeat of the same scenario. The signals read from given monitors can be considered as entries of a vector. This article presents how a loss map of unknown cause can be decomposed using vector based analysis derived from well-known loss scenarios. The algorithms achieving this decomposition are described, as well as the accuracy of the results. | ||
| TUPC142 | The Particle Identification System for the MICE Beamline Characterization | 1356 |
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| The International Muon Ionization Cooling Experiment (MICE) will carry out a systematic investigation of a ionization cooling section of a muon beam, for the future Neutrino Factory and the future Muon Collider. As the emittance measurement will be done on a particle-by-particle basis, a sophisticated beam instrumentation is needed to measure both particle coordinates and timing vs RF in a harsh environment due to high particle rates, fringe magnetic fields and RF backgrounds. A PID system, based on three time-of-flight stations (with resolutions up to 50-60 ps), two Aerogel Cerenkov counters and a KLOE-like calorimeter (KL) has been constructed and has allowed the commissioning of the MICE muon beamline in 2010. It will be complemented in 2011 by an Electron Muon Ranger to determine the muon range at the downstream end of the cooling section. Detector performances, as obtained in the 2010 run, will be shown and the use of PD detectors for the beamline characterization, including a preliminary measure of emittance, fully illustrated. | ||
| TUPC143 | New Techniques in the Synchronization of High-frequency Multichannel Acquisition Systems | 1359 |
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| Today, high-speed digitizer systems operating at well above 100 MSa/s are being used in a diverse range of applications including operation of single-pulse linear induction accelerators for flash radiographic facilities, neutron energy measurement through time-of-flight, and propulsion research. A growing number of such applications require simultaneous measurement of high-frequency signals over many channels. Most of today’s high-speed digitizers or oscilloscopes feature a maximum of only four channels. For applications requiring more than four channels, and needing very precise time correlation between channels or accurate phase of continuous signals, it is necessary to synchronize the sampling clocks of the multiple instruments within the system. This paper presents methods of synchronization, with reference to large-scale multichannel data acquisition requirements in particle acceleration applications using modular instrumentation. A range of system architectures are presented, and advantages and disadvantages of each scheme are discussed. | ||
| TUPC144 | Preliminary BPM Electrics Testing for the Taiwan Photon Source Project | 1362 |
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| The preliminary BPM electrics are developing and testing for Taiwan Photon Source (TPS), is a 3 GeV synchrotron light source which being in construction at NSRRC. This new BPM electronics with integrated FPGA based hardware, and will be testing in the TLS (Taiwan Light Source) with real beam at first. The enhance functionality of current generation will be adopted in the TPS. The electronic prototype testing and relative property will be reported in this report. | ||
| TUPC145 | Vibration and Beam Motion Monitoring in TLS | 1365 |
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| Due to asynchronous nature of various vibration and beam motion related subsystems, it is hard to analysis the correlation between them. Therefore, the synchronous distributed data acquisition system is designed to make an improvement for better analysis. For different circumstances, the system supports two data flow: one is display the real-time data which could be archived continuously and the other is waveform which could be acquired on demand or triggered by event with high sampling rate. In addition, the viewer will improve some useful features, such as trigger by customize signal or EPICS PV record, automatic screenshot and plot the multiple history events. The preliminary test results and implementation details will be summarized in this report. | ||
| TUPC146 | Beam Profiles Analysis for Beam Diagnostic Applications | 1368 |
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| Beam profile and its analysis play an important role in beam diagnostics of a particle accelerator system. Use of destructive screen monitor or non-destructive synchrotron radiation monitor for beam profile measurement is a simple way and has been widely used in synchrotron light source facility. Analyze beam profiles can obtain beam parameters including beam center, σ, and tilt angle which has become a useful tool for beam diagnostic. In this report the comparison of fitting strategies affect the analysis results are studied. The computer simulated beam profiles with different background noise level and conditions are used to evaluate the computing time, and the estimated fitting errors. | ||
| TUPC147 | A Micro-Channel Plate Based Gas Ionization Profile Monitor with Shaping Field Electrodes for the ISIS H− Injector | 1371 |
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| Beam profile measurements within the ISIS H− injector line are achieved using destructive devices such as moving wire scanners. To avoid damage to the wires, measurements are made with the injector operating on reduced power. This paper reports the development of a Micro-Channel Plate based profile monitor which allows beam measurements to be made under normal operating conditions. The monitor produces profiles by measuring the +ion current resulting from the interaction of the H− beam with the surrounding residual gas. The 32 channel Micro-Channel Plate is mounted on a rotating arm to enable it to be positioned parallel to the beam for calibration (all channels then measure the same +ion current) and perpendicular to the beam for profile measurements. A 15kV drift field is used together with field shaping electrodes to ensure a flat electric field gradient across the monitor, thereby minimising distortion of the profile due to the electric field. This paper details all aspects of the design and construction of this profile monitor. Beam profiles are compared to previous wire scanner results. Shaping field upgrades are discussed to improve the longitudinal field shape. | ||
| TUPC148 | Measuring Emittance with the MICE Scintillating Fibre Trackers | 1374 |
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| The Muon Ionization Cooling Experiment (MICE) aims to measure a 10% reduction in a muon beam emittance to within 0.1%. To achieve this two scintillating fibre trackers will be placed within a 4T solenoidal field. The trackers utilize fibres with a diameter of 350 microns to provide a position resolution of less than 0.5 mm. Details of the tracker hardware, electronics and its calibration and reconstruction methods will be presented, along with the measured performance under cosmic ray tests and the simulated performance in MICE. | ||
| TUPC149 | Measurements at the ALICE Tomography Section | 1377 |
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Funding: STFC This paper reports the results of tomography measurements of the electron beam transverse phase space distribution in the ALICE accelerator at Daresbury Laboratory. These measurements have two main aims. The first is to give a detailed picture of the phase space distribution of the electron beam injected from ALICE into the EMMA prototype non-scaling FFAG accelerator. The second is to provide data for the development and testing of a variety of techniques for tomographic reconstruction. We summarize the measurement results which we have obtained and discuss the advantages and disadvantages of some different tomography methods. |
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| TUPC150 | The Effect of Space-Charge on the Tomographic Measurement of Transverse Phase-Space in the EMMA Injection Line | 1380 |
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Funding: STFC Phase-space tomography for particle beams depends upon detailed knowledge of the particle transport through specified sections of a beam line. In the simplest case, only the effects of magnets (such as quadrupoles) and drift spaces need to be taken into account; however, in certain parameter regimes (high charge density and low energy) space charge forces may play a significant role. The ALICE accelerator is the electron source for EMMA, a prototype ns-FFAG machine. Results are presented of investigations into these effects on phase-space tomography in the injection line between ALICE and EMMA. The application of suitable correction techniques* to the EMMA injection line tomography measurements in the presence of space-charge is also discussed. * D. Stratakis et al., Phys. Rev. ST Accel. Beams 9, 112801 (2006). |
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| TUPC151 | Cherenkov Fibre Optic Beam Loss Monitor at ALICE | 1383 |
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| The need for real-time monitoring of beam losses, including evaluation of their intensity and the localization of their exact position, together with the possibility to overcome the limitations due to the reduced space for the diagnostics, makes optical fibres (using the Cherenkov Effect) one of the most suitable and explored candidate for beam loss monitoring. In this contribution, we report on an optical fibre beam loss monitor based on large numerical aperture pure silicon fibres and silicon photomultipliers, tested at ALICE, Daresbury Laboratories, UK. The original design of the sensor has the advantage to combine the functions of a real time detector and a transmission line. It also allows reading the signals independently and determining the time and position of the losses without the use of an external trigger. | ||
| TUPC152 | Comparative Study of Performance of Silicon Photomultipliers for Use in Cherenkov Fibre Optic Beam Loss Monitors | 1386 |
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| Silicon Photomultipliers (SiPMs) are semiconductor photo-sensitive devices built from a matrix of Single Photon Avalanche Diodes (SPADs) on a common silicon substrate, working in the limited Geiger mode and with a common readout. The fast counting ability, high timing resolution, immunity to magnetic field up to 15 T, low power consumption and relative small temperature dependence together with the small dimensions make SiPMs excellent candidates as commercially available solid state detectors, and a promising alternative to traditional photomultiplier tubes for single photon detection. Nevertheless, SiPMs do suffer from erroneous counting due to noise effects that can deteriorate their performances. These effects are, in general, heavily dependent on manufacturing quality. In this contribution, results are reported of the characterization of different models of SiPMs in terms of noise spectra and response to light, and a procedure for determining quality manufacturing parameters is described. | ||
| TUPC153 | Study of the Response of Silicon Photomultipliers in Presence of Strong Cross-talk Noise | 1389 |
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Funding: Work supported by STFC, the EU under GA-ITN-215080, the Helmholtz Association and GSI under VH-NG-328. Silicon Photomultipliers (SiPM) are interesting detectors for beam diagnostics applications where they could replace photomultiplier tubes as large dynamic range photon counting devices due to their reduced dimensions and costs, higher photon detection efficiency, immunity to magnetic fields and low operation voltage. Possible applications include longitudinal beam profile measurements by synchrotron light imaging, detection of optical transition radiation for energy spectrum measurements and medical imaging. However, quantitative measurement with SiPMs are jeopardized by the systematic reading error due to Optical Cross-talk (OC), i.e. optical coupling between neighboring diodes in the array. OC results in overestimation of the impinging light level, and reflects the probability of a triggered avalanche creating a photon of suitable energy and direction to fire a second avalanche in another diode. In this paper, we derive a generalized response distribution for SiPM in presence of cross-talk noise, which overcomes the limitations of assumptions currently made in literature and provides a correction of the SiPM response distribution valid for arbitrary large levels of cross-talk. |
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| TUPC154 | Commissioning of the Detection System for a Supersonic Gas-jets Based Transverse Beam Profile Monitor | 1392 |
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Funding: Work supported by STFC, the EU under GA-ITN-215080, the Helmholtz Association and GSI under VH-NG-328. We present the commissioning results of the Micro-Channel-Plate (MCP) based, ion extraction and detection system currently in use for an experimental test stand aimed at demonstrating the operation of a least-interceptive transverse beam profile monitor based on a planar supersonic gas-jet. This monitoring design features least-interceptive operation under excellent vacuum conditions and provides fast acquisition of a fully bi-dimensional transverse profile. It bears application for ultra-low energy particle beams at future storage rings, but also for e.g. linacs at high currents and light source injectors. For instance, the Ultra-low energy Storage Ring (USR), part of the Facility for Antiproton and Ion Research (FAIR) in Germany will store antiprotons at energies of 20-300 keV. In this contribution, we report numerical simulations and experimental results obtained by calibration of the detection system with a low energy electron beam to demonstrate a 1 mm imaging resolution only limited by recoiling ion drift. |
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| TUPC155 | Optimisation of the LHC Beam Current Transformers for Accurate Luminosity Determination | 1395 |
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| During the 2010 and 2011 LHC runs a series of dedicated fills were used for luminosity calibration measurements at each of the LHC experiments. A major contribution to the final precision of these luminosity calibration campaigns originated from the absolute accuracy of the bunch current population estimation. The importance of these measurements for the LHC physics community triggered a large and fruitful collaboration between the CERN Beam Instrumentation Group and the LHC Experiments to push the LHC Beam Current Transformers performance to their limit. This paper will report on the available instruments for beam current measurements, the methodology used to improve them and the results obtained. | ||
| TUPC157 | Design and Initial Results of a Turn-by-Turn Beam Position Monitoring System for Multiple Bunch Operation of the ATF Damping Ring | 1398 |
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| An FPGA-based monitoring system has been developed to study multi-bunch beam instabilities in the damping ring (DR) of the KEK Accelerator Test Facility (ATF), utilising a stripline beam position monitor (BPM) and existing BPM processor hardware. The system is designed to record the horizontal and/or vertical positions of up to three bunches in the DR in single-bunch multi-train mode or the head bunch of up to three trains in multi-bunch mode, with a bunch spacing of 5.6 ns. The FPGA firmware and data acquisition software were modified to record turn-by-turn data for up to six channels and 1–3 bunches in the DR. An overview of the system and initial results will be presented. | ||
| TUPC158 | Micron-scale Laser-wire at the ATF-II at KEK Commissioning and Results | 1401 |
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| We present the first results from the commissioning of the upgraded laser-wire experiment at the Accelerator Test Facility 2 (ATF2) at KEK. A new laser transport line and beam diagnostics were used to collide 150 mJ, 167 ps long laser pulses with 1.28 GeV, 30 ps long electron bunches to measure the vertical transverse size. Additionally, a new detector was installed with a reduced area for lower background. Initial scans showing a convoluted beam size of 19.2 ± 0.2 microns were used to tune the electron beam optics and reduce this down to 8.1 ± 0.1 microns. Laser pulse energy and charge dependency were investigated showing a linear relationship in both with a minimum laser energy of 20 mJ required for observable signal with this laser and setup. | ||
| TUPC159 | Energy Measurements with Resonant Spin Depolarisation at Diamond | 1404 |
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| A precise knowledge of the electron beam energy is critical for the accurate determination of many light source parameters, such as momentum compaction factor, natural chromaticity, energy stability and undulator spectra. In common with other facilities, a method of energy measurement based on resonant spin depolarisation has been developed at Diamond. In this paper we report on progress towards storage ring characterisation using this method, as well as describing the diagnostics developments that have enabled these measurements to be made. | ||
| TUPC160 | Recent Developments of Diagnostics at Diamond | 1407 |
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| This contribution summarizes some recent development of diagnostics system to improve the operation of Diamond Light Source. Firstly, we are advancing the integration of photon beam diagnostics with the orbit feedback system. Measurements have shown the correlation between recorded electron and photon beam motion on the short timescales (ms-minutes) and the potential for improvement on long timescales (minutes-days). Secondly, with the addition of more elliptically polarized undulators at Diamond, measurement of their photon beam position require a solution that reliably operates with the changing photon beam profiles emitted by these devices. To this end, we have developed an X-ray beam position monitor that analyzes the backscatter from an aperture in the front end. Thirdly, as operation in low-alpha mode with few ps bunch lengths receives increasing interest from users, we have been evaluating various techniques for the measurement of these short bunch lengths that could serve as alternatives to streak camera measurements. | ||
| TUPC161 | Cavity Beam Position Monitor System for ATF2 | 1410 |
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| The Accelerator Test Facility 2 (ATF2) in KEK, Japan, is a prototype scaled demonstrator system for the final focus required for a future high energy lepton linear collider. The ATF2 beam-line is instrumented with a total of 41 high resolution C and S band resonant cavity beam position monitors (BPM) with associated mixer electronics and digitizers. In addition 4 high resolution BPMs have been recently installed at the interaction point, we briefly describe the first operational experience of these cavities in the ATF2 beam-line. The current status of the overall BPM system is also described, with a focus on operational techniques and performance. | ||
| TUPC162 | Thin Foil-based Secondary Emission Monitor for Low Intensity, Low Energy Beam Profile Measurements | 1413 |
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Funding: Work supported by STFC, the EU under GA-ITN-215080, the Helmholtz Association and GSI under VH-NG-328. A secondary emission monitor (SEM) was developed for beam profile measurements at the Ultra-low energy Storage Ring (USR) that will be installed at the future Facility for Low-energy Antiproton and Ion Research (FLAIR) in Darmstadt, Germany. The detector consists of an Aluminium foil on negative potential, a grounded mesh placed in front of the foil, a chevron type microchannel plate (MCP), a phosphor screen and a camera connected to a PC. Simulations of the optimized design together with experimental results with keV protons are presented in this contribution. In addition, the usability of the detector for low energy antiproton beam profile measurements is discussed. |
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| TUPC163 | Experimental Results from Test Measurements with the USR Beam Position Monitoring System | 1416 |
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Funding: Work supported by STFC, the EU under GA-ITN-215080, the Helmholtz Association and GSI under VH-NG-328. A diagonal-cut capacitive pick-up (PU) was optimised for monitoring slow (v < 0.025c), long (~1 m) bunches consisting of only about 106 antiprotons at the future Ultra-low energy Storage Ring (USR). Ultra-low noise (0.5 nV/Hz0.5) FET pre-amplifiers are used to allow detection of the weak signals generated in the PU plates. The amplified signals are then digitized by a 16-bit, 200 MS/s ADC and processed in a digital manner. The following contribution presents the beam monitoring system as it was tested with a stretched-wire method and compares the measurements with the results from 3D electromagnetic simulations. |
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| TUPC164 | Position Determination of Closely Spaced Bunches using Cavity BPMs | 1419 |
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| Cavity Beam Position Monitor (BPM) systems with high-Q form a major part of precision position measurement diagnostics for linear accelerators with low emittance beam. Using cavity BPMs, the position resolution of less than 100 nm has been demonstrated in single bunch mode operation. In the case of closely spaced bunches, where the decay time of the cavity is comparable to the time separation between bunches, the BPM signal from a bunch is polluted by the signal induced from the previous bunches in the same bunch-train. This paper discuss our ongoing work to develop the methods to extract the position of the closely spaced bunches using cavity BPMs. A signal subtraction code is being developed to remove the signal pollution from previous bunches and to determine the individual bunch position. Another code has been developed to simulate the BPM data for the cross check. Performance of the code is studied on the experimental and simulated data. Application of the analysis techniques to the linear colliders, such as International Linear Collider (ILC) and Compact LInear Collider (CLIC), are briefly discussed. | ||
| TUPC165 | DITANET - Investigations into Accelerator Beam Diagnostics | 1422 |
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Funding: Work supported by the EU under GA-PITN-215080. DITANET is a Marie Curie initial training network in beam diagnostics. The network members, universities, research centres and industry partners, are developing diagnostics methods for a wide range of existing or future particle accelerators, both for electron and for ion beams. This is achieved through a cohesive approach that allows for the exploitation of synergies, whilst promoting knowledge exchange between partners. In addition to its broad research program, the network organizes schools and topical workshops for the beam instrumentation and particle accelerator communities. This contribution gives an overview of the Network's research outcomes to date and summarizes past and future training activities. |
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| TUPC166 | Accelerator R&D in the QUASAR Group | 1425 |
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Funding: Work supported by STFC, the EU under GA-PITN-215080, the Helmholtz Associations and GSI under VH-NG-328. Since its start in 2007, the QUASAR Group’s research activities have grown considerably: Whilst the research program towards an ultra-low energy storage ring (USR) at the future facility for low-energy antiproton and ion research (FLAIR) is still the main research focus, developments of beam diagnostics tools for accelerators and lights sources, investigations into superconducting linear accelerators and medical applications, including the potential use of antiproton beams for cancer therapy purposes, widen the Group’s activities and international collaboration considerably. An overview of the QUASAR Group’s research achievements in accelerator science and technology to date is given in this contribution. |
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| TUPC168 | Results from the LHC BRAN Luminosity Monitor at Increased Luminosities | 1428 |
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Funding: This work supported by the US Department of Energy through the US LHC Accelerator Research Program (LARP). The LHC BRAN luminosity monitors are used to monitor and optimize the luminosity at the LHC high luminosity interaction points IP1 and IP5. The Argon gas ionization chambers detect showers produced in the TAN absorbers by neutral particles emerging from pp collisions. The detectors have been operated during the 2010 run by counting the shower rate. As the current 2011 run has the multiplicity of proton-proton collisions per bunch crossing near ten, the detector sees more than one collision per bunch crossing. Therefore, the operation of the detector has been switched to pulse height mode to detect the average shower flux. This paper presents results from recent pulse height mode measurements, including the total and bunch-by-bunch luminosity as well as a determination of the crossing angle at these IPs. Comparisons with luminosity measurements from ATLAS and CMS are also presented. |
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| TUPC169 | Single-shot Electro-optic Sampling of Coherent Transition Radiation at the A0 Photoinjector | 1431 |
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Funding: Work supported by Fermi Research Alliance, LLC under U.S. Dept. of Energy Contract No. DE-AC02-07CH11359, and Northern Illinois Univ. under US Dept. of Defense DURIP program Contract N00014-08-1-1064. Future collider applications and present high-gradient laser plasma wakefield accelerators operating with picosecond bunch durations place a higher demand on the time resolution of bunch distribution diagnostics. This demand has led to significant advancements in the field of electro-optic sampling over the past ten years. These methods allow the probing of diagnostic light such as coherent transition radiation (*) or the bunch wakefields (**) with sub-picosecond time resolution. Potential applications in shot-to-shot, non-interceptive diagnostics continue to be pursued for live beam monitoring of collider and pump-probe experiments. Related to our developing work with electro-optic imaging, we present results on single-shot electro-optic sampling of the coherent transition radiation from bunches generated at the A0 photoinjector. * J. van Tilborg et al., Phys. Rev. Lett. 96, 014801 (2006). ** M. J. Fitch et al., Phys. Rev. Lett. 87 034801 (2001). |
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| TUPC170 | Resonant TE Wave Measurements of Electron Cloud Densities at CesrTA | 1434 |
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Funding: This work is supported by the US National Science Foundation PHY-0734867, and the US Department of Energy DE-FC02-08ER41538. The Cornell Electron Storage Ring has been reconfigured as a test accelerator (CesrTA). Measurements of electron cloud densities have been made at CesrTA using the TE Wave transmission technique. However, interpretation of the data based on single pass transmission is problematic because of the reflections and standing waves produced by discontinuities in the beam pipe - from pumps, bellows, etc. that are normally present in an accelerator vacuum chamber. An alternative model is that of a resonant cavity, formed by the beampipe and its discontinuities. The theory for the measurement of plasma densities in cavities is well established. This paper will apply this theory to electron cloud measurements, present some simplified measurements on waveguide, and apply this model to the interpretation of some of the data taken at CesrTA. |
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| TUPC171 | 2D Optical Streaking for Ultra-short Electron Beam Diagnostics | 1437 |
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| We propose a novel approach to measure the short electron bunch profile at micrometer level. Low energy electrons generated during beam-gas ionization are simultaneously modulated by the transverse electric field of a circularly-polarized laser, and then they are collected at a down-stream screen where the angular modulation are converted to a circular shape there. The longitudinal bunch profile is simply represented by the angular distribution of the electrons on the screen. We only need to know the laser wavelength for calibration and there is no phase synchronization problem. Meanwhile the required laser power is also relatively low in this setup. Some simulations examples and resolution of this method will be discussed. | ||
| TUPC172 | Evaluation and Correction of the Non-linear Distortion of CEBAF Beam Position Monitors | 1440 |
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Funding: Notice: Authored by Jefferson Science Associates, LLC under U.S. DOE Contract No. DE-AC05-06OR23177. The beam position monitors at CEBAF have four antenna style pickups that are used to measure the location of the beam. There is a strong nonlinear response when the beam is far from the electrical center of the device. In order to conduct beam experiments at large orbit excitation we need to correct for this nonlinearity. The correction algorithm is presented and compared to measurements from our stretched wire BPM test stand. |
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| TUPC178 | Charge Lifetime Study of K2CsSb Photocathode Inside a Jlab DC High Voltage Gun | 1443 |
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Funding: Work supported by Brookhaven Science Associates, LLC under Contract No. DE-AC02-98CH10886 with the U.S. DOE Two photocathodes are frequently considered for generating high average current electron beams and/or beams with high brightness for current and future accelerator applications: GaAs:Cs and K2CsSb. Each photocathode has advantages and disadvantages, and need to demonstrate performance at “production” accelerator facilities. To this end a K2CsSb photocathode was manufactured at Brookhaven National Lab and delivered to Jefferson Lab within a compact vacuum apparatus at pressure ~ 5x10-11 Torr. This photocathode was installed inside a dc high voltage photogun biased at voltages up to 200 kV, and illuminated with laser light at 440 or 532 nm, to generate beams up to 20 mA. Photocathode charge lifetime measurements indicate that under some conditions this cathode has exceptionally high charge lifetime, without measurable QE decay, even from the center of the photocathode where operation using GaAs photocathodes is precluded due to ion bombardment. These studies also suggest a complex QE decay mechanism likely related to chemistry and localized heating via the laser beam. |
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