Paper | Title | Other Keywords | Page |
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MO103 | SNS Superconducting Linac Operational Experience and Upgrade Path | cryomodule, linac, SRF, HOM | 11 |
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Funding: SNS is managed by UT-Battelle, LLC, under contract DE-AC05-00OR22725 for the U.S. Department of Energy |
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MO201 | Progress in the Beam Commissioning of J-PARC Linac and its Upgrade Path | linac, rfq, neutron, target | 16 |
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The beam commissioning of J-PARC linac has been started since November 2006, and the initial commissioning has been completed in September 2007. Since then, the linac beam has been supplied to the succeeding RCS (Rapid Cycling Synchrotron) for its commissioning with occasional linac beam studies for finer tuning. The emphasis of the linac tuning has been shifted to the characterization and stabilization of the beam parameters, and better beam availability has gradually been required for the linac operation. In this paper, we present the current linac performance and operational experience obtained so far after a brief review of the commissioning history. Remaining commissioning tasks and the future upgrade plan to increase the beam power are also discussed. |
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MO203 | The SARAF CW 40 MeV Proton/Deuteron Accelerator | rfq, simulation, ion, proton | 26 |
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The Soreq Applied Research Accelerator Facility, SARAF, is currently under construction at Soreq NRC. SARAF is based on a continuous wave (cw), proton/deuteron rf superconducting linear accelerator with variable energy (5-40 MeV) and current (0.04-2 mA). SARAF is designed to enable hands-on maintenance, which implies beam loss below 10-5 for the entire accelerator. Phase I of SARAF consists of an ECR ion source, a LEBT section, a 4-rod RFQ, a MEBT section, a superconducting module housing 6 half-wave resonators and 3 superconducting solenoids, a diagnostic plate and a beam dump. Phase II will include 5 additional superconducting modules. The ECR source has been in routine operation since 2006, the RFQ has been operated with ions and is currently under characterization. The superconducting module rf performance is being characterized off the beam line. Phase I commissioning results, their comparison to beam dynamics simulations and Phase II plans will be presented. |
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MO301 | Overview of the High Intensity Neutrino Source Linac R&D Program at Fermilab | linac, proton, solenoid, rfq | 36 |
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Funding: Fermilab is operated by Fermi Research Alliance, LLC under Contract No. DE-AC02-07CH11359 with the United States Department of Energy. |
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MOP003 | Performance of the Control System for the J-PARC Linac | controls, linac, vacuum, klystron | 52 |
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Linac of J-PARC began to operate in November, 2006, and a achieved an initial performance in January, 2007. Afterwards, the beam supply to RCS begins, and it is operating extremely well with stability up to now. Here, the evaluation for comparison of the design and realities of architecture and performance of the LINAC control system are shown. Especially, the conceptual idea of function arrangement in the hierarchy of the control system architecture is shown. Now, the linac control system is in the second phase for the high power beam and reducing the beam loss, and the analysis of the system response identification for the high precision beam control is started. |
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MOP006 | Stability of Normal Conducting Structures Operation with High Average Heat Loading | coupling, DTL, linac, simulation | 61 |
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Instead of proved application of superconducting structures for high energy part of intense linear proton accelerators, normal conducting structures are still considered for medium and low energy parts below 200 MeV. Operation with accelerating rate ~4 MeV/m and duty factor ~5% results for standing wave normal conducting structure in an average heat loading ~30 kW/m. Due to the high heat loading an operating mode frequency shift is significant during operation. In this paper conditions for field distribution stability against small deviations in time of individual cell frequencies are considered. For pi/2 structures these conditions were formulated by Y. Yamazaki and L. Young. General case of 0, pi/2 and pi operating modes is considered with common approach. |
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MOP008 | Development of a Cell-Coupled Drift Tube Linac (CCDTL) for Linac4 | linac, coupling, DTL, alignment | 67 |
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The 352 MHz CCDTL will accelerate the Linac4 beam from 50 to 102 MeV. It will be the first CCDTL used in a proton linac. Three short DTL tanks, each having two drift tubes, are connected by coupling cavities and form a chain of 5 resonators operating in the stable π/2 mode. The CCDTL section is made of 7 such chains, each fed by a 1.3 MW klystron. Focusing quadrupoles are placed between tanks, easing their alignment with respect to a conventional DTL thus making the structure less sensitive to manufacturing errors. In order to validate the design and to develop the production technology, two prototypes have been constructed and successfully tested. The first prototype, built at CERN, consists of two half-cavities and one coupling cell, whereas the second, with two full cavities and one coupling cell, was built at VNIITF and BINP in Russia in the frame of an R&D contract funded by the ISTC Organisation. Both prototypes have been tested at CERN slightly beyond their nominal power level, at the design duty cycle of 10%. In this paper we present the results of high-power tests, the results of the technological developments prior to production, and the final design of the CCDTL. |
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MOP011 | An 8 GeV CW Linac With High Potential Beam Power | linac, proton, cyclotron, injection | 76 |
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Modern technology allows us to consider operating an 8 GeV Linac in a cw mode to accelerate a high-current H- beam. By using appropriate accumulation rings, the linac could provide simultaneous beams for direct neutrino production, neutrino factories, fixed target experiments, and muon colliders. Several other unique accelerator applications could also be served and improved by the same continuous beam, including studies of energy production and nuclear waste reduction by transmutation, rare muon decay searches, and muon catalyzed fusion. The trade-offs between cw operation compared to pulsed operation that are considered include the maximum rf gradient and corresponding linac length or energy, the rf frequency, rf peak power and coupler requirements, and refrigeration. Methods for accumulating the beam from a cw linac to serve the special needs of the potential future Fermilab programs mentioned above are considered. In this paper we also examine the use of a cyclotron as a source of high current beams to reduce the cost and complexity of the linac front end. |
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MOP012 | High Power Test of Room Temperature Spoke Cavities for HINS at Fermilab | vacuum, linac, controls, ion | 79 |
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The High Intensity Neutrino Source (HINS) R&D program at Fermilab will build a new 65 MeV test linac to demonstrate new technologies for application in a high intensity hadron linac front-end. The HINS warm section is composed of an ion source, a radio frequency quadrupole, a medium energy beam transport and 16 room temperature Crossbar H-type (RT-CH) cavities that accelerate the beam to 10 MeV (β=0.1422). The RT-CH cavities are separated by superconducting solenoids enclosed in individual cryostats. Beyond 10 MeV, the design uses superconducting spoke resonators. In this paper, we illustrate the completion of four RT-CH cavities and explain latest modifications in the mechanical and radio frequency (RF) designs. Cavities RF measurements and tuning performed at Fermilab are also discussed. Descriptions of the HINS R&D Facility including high power RF, vacuum, cooling and low level RF systems will be given. Finally, the history of RF conditioning and the results of high power tests of RT-CH cavities will be discussed. |
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MOP016 | Operational Experience of the SNS Front End and Warm Linac | linac, target, beam-losses, DTL | 91 |
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Funding: SNS is managed by UT-Battelle, LLC, under contract DE-AC05-00OR22725 for the U.S. Department of Energy. |
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MOP018 | ISAC-II Superconducting Linac Upgrade - Design and Status | cryomodule, ISAC, linac, vacuum | 97 |
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The ISAC-II superconducting linac, operational since April 2006, adds 20 MV accelerating potential to the ISAC Radioactive Ion Beam (RIB) facility. An upgrade to the linac, in progress, calls for the addition of a further 20 MV of accelerating structure by the end of 2009. The new installation consists of twenty 141 MHz quarter wave cavities at a design beta of 11%. The cavities will be housed in three cryomodules with six cavities in the first two cryomodules and eight cavities in the last. A second Linde TC50 refrigerator has been installed and commissioned to provide cooling for the new installation. The design incorporates several new features as improvements to the existing cryomodules. They include a four point support frame for the cavity strongback, a modified LN2 circuit internal to the cryomodule and a new design for the mechanical motion of the rf coupling loop. A summary of the design and the current status of the cryomodule production and supporting infrastructure will be presented. |
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MOP019 | The HITRAP Decelerator Project at GSI - Status and Commissioning Report | rfq, ion, pick-up, diagnostics | 100 |
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For injection into the ion trap facility HITRAP, the GSI accelerator complex has the unique possibility to provide beams of highly stripped ions and even bare nuclei up to Uranium at an energy of 4 MeV/u. The HITRAP facility consists of linear 108 MHz-structures of IH- and RFQ-type to decelerate the beams further down to 6 keV/u for capturing in a large penning trap for cooling purpose. The installation is completed except of the RFQ-tank. During commissioning periods in 2007 64Ni28+ and 20Ne10+ beam was used to investigate the beam optics from the experimental storage ring extraction to the HITRAP double-drift-buncher system. In 2008 the IH-structure decelerator and the downstream matching section was examined with 197Au79+ beam. Comprehensive beam diagnostics were installed: Faraday cups, tubular and short capacitive pick ups, SEM grids, YAG scintillation screens, a single shot pepperpot emittance meter, and a diamond detector for bunch shape measurements. Results of the extensive measurements are presented. |
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MOP020 | Post-Accelerator LINAC Development for the RIB Facility Project at VECC, Kolkata | linac, ion, rfq, quadrupole | 103 |
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An ISOL (Isotope Separator On Line) type of RIB (Radioactive Ion Beam) facility* is being developed at our centre. The post-acceleration scheme will consist of a Radio Frequency Quadrupole** (RFQ) followed by a few IH LINAC cavities - further augumentation of energy using SC QWRs will be taken up at a later stage. The first two IH cavities have been designed for 37.6 MHz frequency like the preceding RFQ to keep the rf defocusing smaller. Explosively bonded copper on steel has been used for the fabrication of the IH cavities (1.72 m inner diameter, 0.6 m and 0.87 m lengths) and the inner components have been made out of ETP grade copper. Also, we have adopted an octagonal cavity structure to avoid fabrication complicacies. Thermal analysis of the cavities have been carried out and cooling configurations have been optimized accordingly to control the temperature rise of the LINACs. Detailed mechanical analysis has been carried out to reduce the deflection of the LINAC components under various loads. Design and fabrication aspects of these two cavities and results of the low power tests will be reported in this paper. * Alok Chakrabarti et. al. ; Proc. Part. Accl. Conf. 2005, pp-395. |
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MOP022 | The ALPI Super-Conducting Accelerator Upgrade for the SPES Project | acceleration, ion, quadrupole, diagnostics | 109 |
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The SPES project* at Laboratori Nazionali di Legnaro foresees the contruction of a RIB facility based on a fission target driven by a 40 MeV proton beam. After the 238U carbide target the 1+ charged ions will be selected by a high resolution mass spectometer, charge enhanced by a charge breeder and accelerated up to 10 MeV/A for 132Sn. The Legnaro superconducting accelerator complex, PIAVE injector and ALPI main accelerator, in its present configuration fits the requirements for SPES post acceleration. Nevertheless an upgrade of its performaces both in overall transmission and final energy is needed and a solution which minimizes the impact on the present structures will be presented. *http://www.lnl.infn.it/~spes/ |
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MOP024 | Low Energy Spread Beam Dynamics and RF Design of a Trapezoidal IH-RFQ | rfq, bunching, impedance, ion | 115 |
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Funding: Supported by NSFC (10775009) |
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MOP025 | An Intermediate Structure SFRFQ Between RFQ and DTL | rfq, DTL, focusing, ion | 118 |
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Funding: supported by NSFC 10455001 |
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MOP028 | A SC Upgrade for the REX-ISOLDE Accelerator at CERN | linac, ion, cryomodule, acceleration | 124 |
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The High Intensity and Energy ISOLDE (HIE-ISOLDE) proposal is a major upgrade of the existing ISOLDE and REX-ISOLDE facilities with the objective of increasing the energy and the intensity of the delivered radioactive ion beam. For the energy increase a staged construction of a superconducting linac based on sputtered quarter wave cavities is foreseen downstream of the present normal conducting linac. A funded R&D program has been launched at the end of 2007 in order to prepare a full Technical Design Report covering all the issues of such a linac, including cavity prototyping and testing, cryomodule design, beam dynamics and beam diagnostics. We report here on the status and planning of the R&D activities for the SCREX-ISOLDE linac. |
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MOP029 | Beam Dynamics Studies for the SCREX-ISOLDE Linac at CERN | cryomodule, linac, emittance, simulation | 127 |
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For the REX-ISOLDE upgrade a superconducting linac based on 101.28 MHz Quarter Wave Resonators (QWRs) is foreseen downstream the normal conducting (NC) linac. Currently the REX-ISOLDE linac can accelerate ions with a mass to charge ratio in the range of 3 < A/q < 4.5 and up to an energy of 3 MeV/u. The upgrade aims to reach a final beam minimum energy of 10 MeV/u for A/q=4.5 in two main stages. The first stage consists of installing two cryomodules loaded with 10 cavities able to reach 5.5 MeV/u at the end of the present linac and the second consists of replacing part of the existing NC linac and adding further cryomodules. We report here on a beam dynamics study of the accelerator for the two installation stages and the transport line to the experimental station. |
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MOP037 | RF Design of the IFMIF-EVEDA RFQ | rfq, vacuum, coupling, simulation | 148 |
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The RFQ of IFMIF-EVEDA project is characterized by very challenging specifications, with 125 mA of deuteron current accelerated up to 5 MeV. Upon beam dynamics studies, it has been chosen a law for the variation of R0 and voltage along the structure; this law provides a significant reduction in terms of structure length, beam losses and rf power consumption. Starting from these outcomes, the rf study of the RFQ, aimed at determining the optimum design of the cavity shape, was performed. The stabilization issues were also addressed, through the analysis of the RFQ sensitivity to geometrical errors, by means of perturbative theory-based algorithms developed for this purpose . Moreover the determination of the main 3D details of the structure was also carried out. In this article the results of the rf studies concerning the above-mentioned topics are outlined. |
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MOP039 | Design of a 2-Beam Type IH-RFQ Linac for High Intense Heavy Ion Beam Accelerations in Low Energy Region | rfq, linac, ion, acceleration | 154 |
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In order to obtain high intensity ion beams from a linear accelerator (linac) stably, it is necessary to suppress the defocusing force due to the space charge effect. The defocusing force is extremely strong in low energy and high intensity beams. Therefore, high intensity ion beam acceleration in the low energy region is one of the most difficult conditions to achieve. One of the solutions is the relaxation of the defocusing force by dividing the high intensity beam into several beams. Thus, a multibeam IH type Radio Frequency Quadrupole (IH-RFQ) linac has been proposed for a high intensity injector system. In particular, we have been developing a two-beam type IH-RFQ cavity as a prototype of the multibeam type IH-RFQ by using computer code. This prototype has the capability of accelerating charged particles to mass ratio (q/A) greater than 1/6 from 5 keV/u up to 60 keV/u. The expected total output current is 87.2 mA for the total input beam current of 120 mA. |
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MOP040 | The Radiofrequency Quadrupole Accelerator for the Linac4 | rfq, linac, emittance, quadrupole | 157 |
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The first stage of acceleration in Linac4, the new 160 MeV CERN H- injector, is a 352 MHz, 3 m long Radiofrequency Quadrupole (RFQ) Accelerator. The RFQ will capture a 70 mA, 45 keV beam from the rf source and accelerate it to 3 MeV, an energy suitable for chopping and injecting the beam in a conventional Drift Tube Linac. Although the RFQ will be initially operated at low duty cycle (0.1%), its design is compatible with higher duty cycle (10%) as the front-end for a possible high-intensity upgrade of the CERN linac facility. The RFQ will be of the brazed-copper design and will be built and assembled at CERN. Beam dynamics design allows for a compact structure made of a single resonant unit. Field symmetry is ensured by fixed tuners placed along the structure. In this paper we present the rf and mechanical design, the beam dynamics and the sensitivity to fabrication and to rf errors. |
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MOP043 | Simulation of Multipacting in HINS Accelerating Structures with CST Particle Studio | simulation, electron, accelerating-gradient, background | 166 |
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Recently high power tests of the room temperature cross-bar H-type resonators (CH resonators) and high gradient tests of a superconducting single spoke resonator (SSR) have been performed under the High Intensity Neutrino Source (HINS) project at Fermilab. The resonators have shown a tendency of having multipacting at various levels of input power and therefore longer processing time. To provide insights for the problem, detailed numerical simulations of multipacting for these resonators have become necessary. New generation of accelerating structures like superconducting spoke resonators and room temperature CH resonators need a full 3D treatment. Simulations and study of multipacting in the resonators have been carried out using CST Particle Studio. The problematic regions and power levels have been identified for both types of resonators. This presentation will give the result of simulations and comparison with experimental data. |
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MOP047 | Quadrupole Magnet Development for 132 MeV DTL of CSNS | DTL, quadrupole, linac, alignment | 178 |
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In the China Spallation Neutron Source (CSNS) linac, a conventional 324 MHz drift-tube linac (DTL) accelerating an H- ion beam from 3 MeV to 132 MeV has been designed with 1.05% duty, consisting of 7 tanks with a total length of approximately 59.6 m. Currently, R&D work has focused on Tank 1, which will have 61 drift-tubes (DT) each housing an electro-magnet quadrupole (EMQ). Some EMQs with SAKAE coil have been fabricated and are under rigorous magnetic measurements by means of Hall probe, single stretched wire, rotating coil in order to verify the design specifications and fabrication technology. Magnetic measurements on the EMQs with iron cores made from the electrical-discharge machining (EDM) and the stacking method will be compared and discussed. Work has been implemented to reduce the alignment discrepancies between the geometric center of the DT and magnetic center of EMQ to within ± 50 μm. |
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MOP049 | Drift Tube Linac Design and Prototyping for the CERN Linac4 | linac, DTL, quadrupole, alignment | 184 |
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The Drift Tube Linac (DTL) for the new linear accelerator Linac4 at CERN will accelerate H- ion beams of up to 40mA average pulse current from 3 to 50MeV. It is designed to operate at 352.2MHz and at duty cycles of up to 10%, if required by future physics programmes. The accelerating field is 3.2MeV/m over the entire length. Permanent magnet quadrupoles are used as focusing elements. The 3 DTL cavities consist of 2, 4 and 4 segments of about 1.8m each, are equipped with 35, 41 and 29 drift tubes respectively, and are stabilized with post-couplers. Several new features have been incorporated in the basic design. The electro-magnetic design has been refined in order to reduce peak field levels in critical areas. The mechanical design aims at reducing the complexity of the mechanical structure and of the adjustment procedure. Drift tubes and holders on the tanks that are machined to tight tolerances do not require adjustment mechanisms like screws or bellows for drift tube positioning. A scaled cold model, an assembly model and a full-scale prototype of the first half tank have been constructed to validate the design principles. The results of metrological and rf tests are presented. |
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MOP052 | Re-phasing of the ISAC Superconducting Linac with Computed Values | linac, emittance, ISAC, simulation | 193 |
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The ISAC superconducting linac is a fully operational machine that routinely provides beam to experiments. The linac consists of twenty superconducting independently phased cavities housed in five cryomodules. The initial tune is done manually aided by MATLAB routines to phase the linac and set the correct optics. From the initial tune we calculate the gradient at which each cavity operates based on the energy gain, the transit time factor and the geometry of the cavity itself. Then in the event of a gradient change of one or more cavities we can calculate the rf phase shift of each downstream cavity using the initial gradients, the known geometry of the entire linac and assuming linearity of the rf controls. This possibility has been investigated and we have demonstrated that the calculated phase shift can be implemented automatically thus avoiding a complete retune of the machine. In this paper we will present the calculations and the results of the online tests. |
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MOP053 | The SPIRAL 2 Superconducting Linac | cryomodule, linac, vacuum, coupling | 196 |
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The SPIRAL2 superconducting linac is composed of 2 cryomodule families, basically one of low beta, called Cryomodule A, and one of high beta, called Cryomodule B. The low beta family is composed of 12 single cavity cryomodule. The high energy section is composed of 7 cryomodules hosting 2 cavities each. According to beam dynamics calculations all the cavities will operate at 88 MHz: one family at beta=0.07, and one at beta=0.12. The design goal for the accelerating field Eacc of the SPIRAL2 QWRs is : 6.5 MV/m. The configuration, cavities and cryomodule tests and status and the foreseen linac tuning will be described. |
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MOP054 | Experience with Stripping Carbon Foils in ALPI Super-Conducting Accelerator | ion, target, linac, focusing | 199 |
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The superconducting linac ALPI, injected either by a XTU tandem or by the superconducting RFQ of PIAVE, is composed by 3 cryostats of bulk Nb cavities (β=0.056) and 13 cryostats of Nb sputtered on Cu cavities (β=0.11 and β=0.13), for a total of 64 cavities and an equivalent voltage of 35MV. The linac is build up in two branches connected by an achromatic and isochronous U-bend. In January 2007 a stripping station equipped with carbon foils of different thickness was placed after 6 cryostats, before the U-bend, to test the feasibility of acceleration and transport of a charge enhanced beam. The study was performed with 4 different beams (Ca, Ar, Zr and Xe) and a complete data analysis has been carried out. |
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MOP055 | Plans for a Superconducting H- Linac (SPL) at CERN | linac, accelerating-gradient, proton, superconducting-cavity | 202 |
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As part of the upgrade of the LHC injector complex at CERN, the construction of a 4 GeV Superconducting Proton Linac (the SPL, in fact an H- accelerator) is planned to begin in 2012. Depending upon physics requests, it should be upgradeable to 5 GeV and multi-MW beam power at a later stage. The construction of Linac4, its low energy front end, has started at the beginning of 2008. A full project proposal with a cost estimate for the low power version of the SPL aimed at improving LHC performance has to be ready for mid-2011. As a first step towards that goal, essential machine parameters like rf frequency, cooling temperature and beam current have recently been revisited and plans have been drawn for designing and testing critical components. The SPL parameters are reviewed in the context of the CERN plans for upgrading the LHC injectors, and the foreseen developments during the next years are described. |
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MOP056 | The Status of the MSU Re-Accelerator (ReA3) | rfq, linac, ion, diagnostics | 205 |
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The Re-accelerator being developed at the Michigan State University is a major component of a novel system proposed at the NSCL to first stop the high energy RIBs by the in-flight particle fragmentation method in a helium filled gas system, then increase their charge state with an Electron Beam Ion Trap (EBIT) charge breeder, and finally re-accelerate them to about 3 MeV/u, in order to provide opportunities for an experimental program ranging from low-energy Coulomb excitation to transfer reaction studies of astrophysical reactions. The accelerator system consists of a Low Energy Beam Transport (LEBT) with an external multi-harmonic buncher, a radio frequency quadrupole (RFQ) followed by a superconducting linac and a High Energy Beam Transport (HEBT). The superconducting linac will use quarter-wave resonators with bopt of 0.047 and 0.085 for acceleration and superconducting solenoid magnets for transverse focusing. The paper will discuss the recent progress of R&D and beam dynamics studies for the MSU Re-accelerator. |
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MOP059 | C6+ Ion Hybrid Single Cavity Linac with Direct Plasma Injection Scheme for Cancer Therapy | ion, linac, rfq, heavy-ion | 211 |
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We succeeded to accelerate very intense carbon ions with the Direct Plasma Injection Scheme (DPIS) using Laser ion source in 2001 and 2004. The peak current reached more than 60 mA of C4+ and 18 mA of C6+ with pulse width of 2-3 x 10-6 sec. We believe that these techniques are quite effective for pulse accelerator complexes such as linear accelerator and synchrotron (heavy-ion cancer therapy). In heavy cancer therapy, carbon stripper section is rejected by accelerated C6+. One turn injection of high intensity (6 mA) C6+ ion is possible to enough in synchrotron. We study a new hybrid single cavity linac combined with radio frequency quadrupole (RFQ) electrodes and drift tube(DT) electrodes into a single cavity. The hybrid linac is able to downsize the linac system and reduce the peripheral device. Using DPIS with Laser ion source, we study POP hybrid single-cavity accelerator of C6+ for injector linac of C cancer therapy. The linac is designed to accelerate 6 mA C6+ ion from 40 keV/u to 2 MeV/u with YAG Laser ion source. We will present the design procedures of this hybrid linac, which is based on a three-dimensional electromagnetic field and particle orbit calculation. |
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MOP060 | Quality Improvement of Laser-produced Protons by Phase Rotation and its Possible Extension to High Energies | laser, proton, ion, focusing | 214 |
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Funding: This work is supported by Advanced Compact Accelerator project by MEXT of Japanese Government and 21COE of Kyoto University, Center for Diversity and Universality in Physics. * Japanese Journal of Applied Physics (Express Letter), 46 (2007) L717-L720 |
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MOP062 | CW Proton Linac for the BNCT Application | linac, rfq, ion, ion-source | 220 |
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A 2.5 MeV, 20 mA, cw, proton linac for the Boron Neutron Capture Therapy medical application is under construction at Linac Systems. The system consists of a 25 keV microwave ion source, a solenoid lens based low energy beam transport system, a 0.75 MeV RFQ linac, a 2.5 MeV RFI linac, and the necessary service systems. Because of the superb low energy capabilities of the RFI structure, the RFQ linac need only go to 0.75 MeV, resulting in a cavity dissipation of 74 kW for the RFQ section. Because of the high rf efficiency of the RFI structure, the cavity dissipation is only 35 kW for the RFI section. Extensive thermal studies have been made to accommodate these cw heat load. The beam power is 50 kW. The rf power system is designed for an average power output of 200 kW. The RFQ and RFI sections are coupled into a single resonant unit by a quarter-wave-stub resonant coupler. The combination is driven at a single point in the RFQ structure. The total length of the linac is 2.6 meters. The system is scheduled for completion by early fall (2008). |
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MOP066 | Status of MICE: the International Muon Ionization Cooling Experiment | emittance, proton, solenoid, coupling | 229 |
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Funding: This work was partially supported by the Office of Science, U. S. Department of Energy, under Contract No. DE-AC02-05CH11231. |
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MOP070 | Beam Dynamics and Error Studies of the SPIRAL2 Driver Accelerator | linac, ion, target, quadrupole | 239 |
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After a detailed design study phase (2003-2004), the SPIRAL2 project at GANIL (Caen, France) was officially approved in May 2005, and is now in its phase of construction, with a project group including the participation of many French laboratories (CEA, CNRS) and international partners. The SPIRAL2 facility is composed of a multi-beam driver accelerator (5 mA/40 Mev deuterons, 5 mA/33 Mev protons, 1 mA/14.5 M ev/u heavy ions), a dedicated building for the production of Radiactive Ion Beams, the existing cyclotron CIME for the post acceleration of the RIBs, and new experimental areas. In this presentation we focus on the beam dynamics studies dedicated to the SPIRAL2 accelerator part of the project, from the ECR sources to the High Energy Beam Lines which have been recently updated. Various tuning examples will be presented for a variety of ions at different final energies, including error studies and beam losses evaluation. Accent is also put on the way we tune the accelerator with the computing code TRACEWIN, by using 3D electromagnetic maps and diagnostics corresponding to the real machine. |
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MOP082 | Multipacting Simulation in RF Structures | simulation, multipactoring, electron, linac | 266 |
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A new computer code for 3D simulation of multipacting phenomenon in axisymmetric and non-axisymmetric rf structures is presented. The goal of the simulation is to determine resonant electron trajectories and electron multiplication in rf structure. Both SW and TW structures of normal- and superconductivity have been studied. Simulation results are compared with theoretical calculations and experimental measurements. |
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MOP083 | Analysis of Input Coupler Asymmetry Influence on Beam Dynamics in Accelerators with Superconducting Cavities | emittance, electron, superconducting-cavity, simulation | 269 |
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Analysis of input coupler asymmetry influence on beam dynamics in superconducting cavities of Energy Recovery Linac (ERL) injector is presented. Both coaxial and waveguide, single and twin input couplers were analyzed. Using computer simulation electromagnetic fields distribution in accelerating cavity was obtained and recalculated to the transverse-kick to the bunch passing the coupler. Also calculation of external coupling was done. RTMTRACE code was adapted for particle beams dynamic simulation. Acceptable transverse emittance growth was achieved for twin-coaxial (4%) and waveguide (5%) input coupler designs. |
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MOP087 | Status of Longitudinal Beam Dynamics Studies in CTF3 | simulation, wakefield, electron, space-charge | 278 |
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The aim of the CLIC Test Facility CTF3, built at CERN by an international collaboration, is to address the main feasibility issues of the CLIC electron-positron linear collider technology by 2010. One key-issue studied in CTF3 is the generation of the very high current drive beam, used in CLIC as the rf power source. It is particularly important to simulate and control the drive beam longitudinal dynamics in the drive beam generation complex, since it directly affects the efficiency and stability of the rf power production process. In this paper we describe the ongoing effort in modelling the longitudinal evolution of the CTF3 drive beam and compare the simulations with experimental results. |
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MOP089 | Beam Dynamics and Wake-field Simulations for High Gradient ILC Linacs | simulation, linac, emittance, wakefield | 284 |
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Higher order modes (HOMs) are simulated with finite element and finite difference computer codes for the ILC superconducting cavities currently under investigation for the ILC. In particular, HOMs in KEK's Ichiro type of cavity and Cornel University's Re-entrant design are focussed on in this work. The aim, at these Universities and laboratories, is to achieve an accelerating gradient in excess of 50 MV/m in 9-cell superconducting cavities whilst maintaining a high quality and stable electron beam. At these high gradients, electrical breakdown is an important cause for concern and the wakefields excited by the energetic electron beams are also potentially damaging to the beam's emittance. Here we restrict the analysis to performing detailed simulations, on emittance dilution due to beams initially injected with realistic offsets from the electrical centre of the cavities and due to statistical misalignments of the cavities. We take advantage of the latest beam dynamics codes in order to perform these simulations. |
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MOP090 | Scattering Matrix Simulations of Fields and Dispersion Relations in Superconducting Cavities for XFEL and ILC | scattering, coupling, simulation, impedance | 287 |
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The globalised scattering matrix (GSM) method provides an efficient means of obtaining the electromagnetic field in interconnected multi-cavity structures. In the proposed XFEL at DESY and the ILC facilities, energetic electron beams can readily excite higher order modes which if left unchecked can dilute the emittance of the beams. The GSM in conjunction with finite element modelling of the scattering matrices of the linac cavities is used to enable the characteristic eigenmodes to be rapidly obtained and the potential for trapped modes is investigated. This characteristic eigensystem allows the wakefield experienced by the beam to be analysed and the consequences on beam quality ascertained. The impact of fabrication errors on the transverse electromagnetic field and corresponding resonant frequencies of the modes is also explored in detailed simulations. |
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MOP105 | Beam Dynamics and Wake-field Simulations for the CLIC Main Linacs | wakefield, emittance, damping, linac | 320 |
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|||
The CLIC linear collider aims at accelerating multiple bunches of electrons and positrons and colliding them at a center of mass energy of 3 TeV. These bunches are accelerated through X-band linacs operating at an accelerating frequency of 12 GHz. Each beam readily excites wake-fields in the accelerating cavities of each linac. The transverse components of the wake-fields, if left unchecked, can dilute the beam emittance. The present CLIC design relies on heavy damping of these wake-fields in order to ameliorate the effects of the wake-fields on the beam emittance. Here we present initial results on simulations of the long-range wakefields in these structures and on beam dynamics simulations. In particular, detailed simulations are performed, on emittance dilution due to beams initially injected with realistic offsets from the electrical centre of the cavities and due to statistical misalignments of the cavities. |
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MOP108 | Phase Law of a High Intensity Superconducting Linac | optics, focusing, linac, beam-losses | 328 |
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Funding: SNS is managed by UT-Battelle, LLC, under contract DE-AC05-00OR22725 for the U.S. Department of Energy.
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TU101 | Unique Features of the J-PARC Linac and Its Performance - Lessons Learnt | rfq, linac, DTL, injection | 343 |
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The J-PARC linac has been successfully commissioned up to its design energy and almost design peak intensity. The unique methods and hardware features adopted in the J-PARC linac, such as the Cs-free H- ion source, macro-pulse generation method, stable one-shot operation method, rf chopper system related with the J-PARC 30mA-RFQ (Radio Frequency Quadrupole linac) design and its operation parameter, one-turn injection method into the following J-PARC RCS (Rapid Cycling Synchrotron), transverse matching using TRACE3D PMQ (Permanent Magnet Quadrupole) elements approximating the fringe field effects of the electro-quadrupole magnets, 2 cavity behavior of SDTL (Separated Drift tube Linac) fed with one Klystron and so on, will be reported in this talk. |
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TU102 | Status of the Construction of the SPIRAL2 Accelerator at GANIL | linac, ion, cryomodule, rfq | 348 |
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The superconducting linac for the SPIRAL2 radioactive ion beam facility at GANIL is in the construction phase. The prototype components have been constructed and are being tested. A status report on the activities and future plans will be given. |
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TU103 | CERN Linac Upgrade Activities | linac, proton, quadrupole, DTL | 353 |
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In its June 2007 session the CERN Council has approved the White Paper, which includes construction of a 160 MeV H- linear accelerator called LINAC4, and the study of a 4 GeV Superconducting Proton Linac (SPL). LINAC4 will initially replace LINAC2 as the injector to the PS Booster, improving its performance up to the levels required for producing the ultimate LHC luminosity. In a later stage, LINAC4 is intended to become the front-end of SPL in a renewed injection chain for the LHC, which could be progressively constructed over the next decade. After briefly introducing the motivations and layout of the new injector chain, the talk will present the characteristics of the new linacs and give an overview of their main technical features and the R&D activities pursued within the HIPPI Joint Research Activity. |
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TU201 | Linac R&D for the ILC Technical Design Report | linac, cryomodule, linear-collider, collider | 359 |
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|||
The International Linear Collider (ILC) Technical Design Report (TDR) is scheduled for publication in 2012. The TDR will include an updated ILC baseline technical design description, results from critical R&D programs in support of key parameter choices, and one or more models for a Project Implementation Plan with an associated value estimate. The focus of linac R&D is to:
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TU204 | Design and Performance of L-Band and S-Band Multi-Beam Klystrons | cathode, klystron, gun, bunching | 369 |
|
|||
In the last couple of years, great achievements have been realized through world-wide developments of multi-beam klystrons (MBK) in the L-band and S-band. These MBKs are developed by industries such as Toshiba, Thales and CPI for the European X-FEL project or at the Naval Research Lab or by the Chinese Academy of Sciences for high-power, low-voltage radar systems. Some of them are already in operation at full specifications and are commercially available. The MBKs are superior to conventional single-beam klystrons through their ability to increase the output power dramatically while the operating voltage can be kept at a similar level. This talk will review the performances of these multi-beam klystrons, their design features, and future development plans. |
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TUP002 | ARIEL and the TRIUMF E-Linac Initiative, a 0.5 MW Electron Linac for Rare Isotope Beam Production | linac, TRIUMF, electron, target | 383 |
|
|||
TRIUMF, in collaboration with university partners, proposes to construct a megawatt-class electron linear accelerator (e-linac) as a driver for U(γ,f) of actinide targets for nuclear astrophysics studies, and 9Be(γ,p)8Li for beta-NMR materials science. The e-linac is part of a broader proposal for an expansion of the TRIUMF rare isotope beams capability through a new facility to be named ARIEL. The e-linac design and prospects for funding are elaborated. |
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TUP003 | Proposal for a 15 MeV Superconducting Electron Linac for the DEINOS Project | laser, linac, high-voltage, electron | 386 |
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|||
The design of a 15 MeV, 2 kA peak current, electron accelerator for the DEINOS project is presented. It is dedicated to a new radiographic facility. The accelerator design is based on a dc photo-injector and a rf superconducting linac. Up to twenty electron micro-pulses, 100 ps time duration and 200 nC bench charge are emitted at 352 MHz repetition rate from a CS2Te photocathode and accelerated to 2.5 MeV in the dc diode before injection into a superconducting linac. A general description of the main accelerator components and the beam dynamics simulations are presented. |
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TUP006 | Improving the Superconducting Cavities and Operational Findings at the S-DALINAC | niobium, vacuum, superconducting-cavity, SRF | 395 |
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Funding: Work supported by the DFG through SFB 634 |
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TUP007 | The Power and Polarisation Upgrade Project at the S-DALINAC Injector | electron, cathode, polarization, vacuum | 398 |
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Funding: Work supported by the DFG through SFB 634 |
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TUP019 | Injector of Intense Electron Beam | electron, simulation, bunching, emittance | 431 |
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The results of beam dynamic simulation in an S-band injector that can be used for creation of the powerful electron linac are presented in the report. The injector consists of a diode electron gun with beam current of up to 2 A at energy of electrons of 25 keV, the klystron type prebuncher and the three cavity buncher. In the buncher, due to the special choice of eigen frequencies of resonators, maximal amplitude of the field on the axis of resonators exponentially increase from the first (downstream of the beam) resonator to the last resonator. It allows effective bunching the intensive electron beam and accelerating it to relativistic velocities. For providing of low transversal beam emittance the injector is placed in the external magnetic field. The injector provides more than 1 A of beam current at particle energies of about 1 MeV. Attention is paid to research of transients and stability of injector work. |
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TUP022 | RF Control and Longitudinal Beam Stability in Energy Recovery Linacs | linac, beam-loading, controls, injection | 440 |
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Funding: Work partially funded by the European Commission in the Sixth Framework Program, contract no. 011935 EUROFEL-DS5, BMBF and Land Berlin. |
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TUP026 | Exploring Benefits of Using RF Deflection for Short X-Ray Pulse Generation for an Energy-Recovery Linac Upgrade to the Advanced Photon Source | undulator, photon, emittance, radiation | 447 |
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Funding: Work supported by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences, under Contract No. DE-AC02-06CH11357. *A. Zholents, et al., Nucl. Instr. and Meth. A 425 (1999) 385. |
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TUP028 | Status of High Current R&D Energy Recovery Linac at Brookhaven National Laboratory | electron, emittance, gun, SRF | 453 |
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Funding: Work performed under contract No. DE-AC02-98CH10886 with the auspices of the DoE of United States. |
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TUP031 | Normal Conducting Options for the UK's New Light Source Project | linac, klystron, emittance, FEL | 462 |
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A New Light Source project has been initiated to deliver a conceptual design for a next-generation light source facility in the UK. One option for such a light source is a free electron laser based on normal-conducting linac technology. This paper considers the different options available for waveband, gun and rf design of a normal-conducting linac FEL, and presents an overview of accelerating structure, modulator and klystron capability and availability. Particular attention is paid to the issue of the operation of a normal-conducting device at repetition rates of several hundred pulses per second. Overall capabilities and limitations of this approach are illustrated by reference to a start-to-end model of a suitable 3 GeV S-band linac design. |
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TUP032 | Simulations on Impact of the 3.9 GHz RF Section on the Multi Bunch Emittance at FLASH | emittance, damping, HOM, linac | 465 |
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|||
In order to compensate nonlinear distortions of the longitudinal phase space a rf section operated at three times the 1.3 GHz frequency of the existing TTF cavities is foreseen in the next phase of FLASH. Four modules of a nine-cell 3.9 GHz cavities will be installed right after the first accelerating module ACC1. These cavities could cause additional long-range wake fields which would affect the multi bunch (mb) beam dynamics leading to increase of the mb emittance. The mb emittance at the end of the linac is determined by the strength of the transverse wake fields in the rf system. These higher order modes appear after any off-crest moving bunch, which could happen either due to the cavity misalignment, or by transverse position fluctuations of the injected bunches. It is intended to damp them by means of the HOM couplers, which may reduce the damping time by factor of 105. The misalignment of the cavities offsets is expected to be by 0.5 mm rms. The paper describes the results of the simulations on the dependence of the mb emittance on cavities misalignment offsets and damping strength of the HOM couplers in the planned 3.9 GHz rf section. |
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TUP034 | Status of the 3rd Harmonic Systems for FLASH and XFEL in Summer 2008 | klystron, linac, controls, electron | 471 |
|
|||
Ultra short bunches with high peak current are required for the creation of high brilliance coherent light in the VUV and X-ray range in undulators. At the Free Electron Laser in Hamburg (FLASH) and the European X-ray free electron laser (XFEL) they are obtained by a two stage bunch compression scheme based on acceleration off the rf field crest and transverse magnetic chicanes. The deviation of the rf field's sine shape from a straight line leads to long bunch tails and reduces the peak current. This effect can be eliminated by adding a third harmonic rf system. The paper gives an overview on the actual status of the beam dynamical examinations and as well on the development of the third harmonic sub-systems like modules, cavities and radio frequency systems for FLASH and the XFEL. |
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TUP035 | New Experimental Results from PITZ | gun, emittance, cathode, laser | 474 |
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Funding: This work was partly supported by the European Community, contracts RII3-CT-2004-506008 and 011935, and by the 'Impuls- und Vernetzungsfonds' of the Helmholtz Association, contract number VH-FZ-005. * L. Staykov et al., "Measurements of the Projected Normalized Transverse Emittance at PITZ", Proceedings of the FEL 2007, Novosibirsk, Russia, August 2007. |
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TUP041 | Superconducting Options for the UK's New Light Source Project | cryomodule, FEL, linac, SRF | 486 |
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|||
The UK's new light source project was officially launched on April 11th 2007, which will be based on advanced conventional and free electron lasers, with unique and world leading capabilities. User consulation exercises have already been initiated to determine the fundamental photon output requirements for such a machine. In order to match a nominal requirement for high repetition rates (extending up to 1 MHz), a series of superconducting rf (SRF) linac options have been investigated, reflecting varied beam loading conditions and subsequent high and low power rf solutions. |
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TUP042 | High Repetition Rate Electron Injectors for FEL Based Next Generation Light Sources | gun, emittance, SRF, simulation | 489 |
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|||
Several laboratories concentrate their efforts on development of high repetition rate FEL based next generation light sources. One particular concept under development at STFC Daresbury Laboratory specifies high brightness electron bunches with a charge of 0.2-1 nC which arrive with a frequency up to 1 MHz. As emittance of the bunches should not exceed 1 um, traditional high repetition rate thermionic injectors, similar to the ones used at high micropulse repetition rate FELs like ELBE or FELIX, may not be used. We consider three options of high repetition rate injectors based on photocathode guns - a high voltage dc gun, a one and half cell superconducting rf gun and a normal conducting VHF gun, recently proposed at LBNL. We consider practical injector schemes for all three guns and provide the results of beam dynamic simulations. We also discuss the photocathodes which may be used in each gun, as this critical component defines achievable beam parameters and operational efficiency of the injectors. |
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TUP045 | Generation of Femtosecond Bunch Trains Using a Longitudinal-to-Transverse Phase Space Exchange Technique | emittance, dipole, simulation, electron | 498 |
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|||
Funding: Work supported by the Fermi Research Alliance, LLC under Contract No. DE-AC02-07CH11359 with the U.S. DOE and by Northern Illinois University under Contract No. DE-FG02-08ER41532 with the U.S. DOE *P. Emma, Z. Huang, K.-J. Kim, and P. Piot, Phys. Rev. ST Accel. Beams 9, 100702 (2006). |
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TUP050 | Design and Optimization of Electron Bunch Acceleration and Compression | electron, wakefield, linac, acceleration | 512 |
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Funding: The work of PE and JW was supported by the US Department of Energy under contract DE-AC02-76SF00515. The work of RAB and KJK was supported by National Science Foundation Award No. DMR-0537588. |
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TUP051 | Design of Microwave Undulator Cavity | undulator, radiation, electron, synchrotron | 515 |
|
|||
Static magnetic field undulators are capable of producing quasi-monochromatic synchrotron radiation of very high brightness. However, it is not possible to quickly change the properties such as polarization of the radiation in a static undulator. It is possible to construct an undulator using microwaves instead of static magnets where the electron beam is undulated by both electric and magnetic fields of an rf wave. A major advantage with a microwave undulator is that the radiation properties can be changed very quickly. The biggest challenge in developing a microwave undulator is in keeping the rf losses low. We are designing a microwave undulator with the aim of achieving at least a tenth of the flux obtained by the BL13 static magnetic field Elliptical Polarized Undulator in the SPEAR ring. We have considered circular waveguide modes and hybrid HE11 mode in a corrugated waveguide as possible candidates for the microwave undulator. It is found that a corrugated waveguide has the lowest rf losses with a very desirable field profile. It is also possible to use this device for a linac driven FEL. Our analysis of the corrugated waveguide cavity for the rf undulator will be presented. |
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TUP065 | Demonstration of Multi-Pulse X-ray Generation via Laser-Compton Scattering Using Pulsed-Laser Super-Cavity | laser, electron, photon, linac | 545 |
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Funding: Work supported by a Grant-In-Aid for Creative Scientific Research of JSPS (KAKENHI 17GS0210) and a Grant-In-Aid for JSPS Fellows (19-5789) |
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TUP081 | Transient Beam Loading Compensation in CTF3 | linac, beam-loading, electron, radiation | 585 |
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|||
In the CLIC Test Facility 3 (CTF3), the strong coupling between the beam and the accelerating cavities (full beam loading) induces transient effects such that the head of the pulse is accelerated almost twice as much as the steady-state part of the pulse. The beam optics in the machine is tailored for the steady-state and not for the higher energy electrons, which are gradually lost. This can lead to inefficiency and contributes to the activation of the machine. A beam loading compensation scheme has been proposed to minimize this effect. By delaying appropriately the arrival time of rf pulse in accelerating cavities with respect to the beam, the transient energy can be brought close (to within a few percent) of the steady-state one. This paper presents the measurements done on CTF3 using time resolved energy measurements. |
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TUP086 | Initial Commissioning of a Dual-Sweep Streak Camera on the A0 Photoinjector | laser, emittance, electron, optics | 600 |
|
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Funding: Operated by Fermi Research Alliance, LLC under Contract No. DE-AC02-07CH11359 with the United States Department of Energy. |
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TUP089 | Electron Beam Timing Jitter and Energy Modulation Measurements at the JLab ERL | electron, FEL, wiggler, instrumentation | 606 |
|
|||
When operating JLab high current ERL a strong reduction of the FEL efficiency was observed when increasing the average electron beam current. Investigating the FEL efficiency drop-off with the electron beam average current we also have measured the electron beam phase noise and the fast energy modulations. The so-called phase noise is essentially a variation of the time arrival of the electron bunches to the wiggler. That could be a very effective way of reducing the FEL efficiency if one takes in to account that the accelerator is routinely operated with the RMS bunch length of about 150 fs. Under a fast energy modulation we mean a modulation which can not be followed by the FEL due to its time constant, defined by the net gain. Such a modulation also could be a possible cause of the efficiency drop-off. Having the measurements made we could rule out the FEL efficiency drop-off due to either the fast energy modulation or the phase modulation. We also have learned a lot about instrumentation and techniques necessary for this kind of beam study. In this contribution we describe the used instrumentation and present results of the measurements. |
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TUP094 | Development of a Photocathode RF Gun for an L-Band Electron Linac | electron, gun, cathode, emittance | 621 |
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Funding: This research is partly supported by the accelerator support program to universities conducted by the High Energy Accelerator Research Organization in Japan. |
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TUP095 | Development of a Cs-Te Cathode RF Gun at Waseda University | gun, electron, cathode, resonance | 624 |
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Funding: Work supported by MEXT High Tech Research Project HRC707, JSPS Grant-in-Aid for Scientific Research (B)(2) 16340079 |
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TUP096 | RF Gun Development with Improved Parameters | gun, simulation, cathode, vacuum | 627 |
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|||
During development and operation of DESY L-band rf gun cavities, desires for further improvements were formulated. The next step of development is based on the proven advantages of existing cavities, but includes significant changes. The L-band 1.6 cell rf gun cavity is intended for operation in pulse mode with electric fields at the cathode of up to 60 MV/m, rf pulse length of ~1 ms and average rf power higher than existing gun cavities. In the new design the cell shape is optimized to have the maximal surface electric field at the cathode and lower rf loss power. The cavity cells are equipped with rf probes. Cooling circuits are designed to combine cooling efficiency with operational flexibility. In the report, the main design ideas and simulation results are described. |
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TUP098 | Lienard-Wiechert Potentials and Method of Images in RF Free Electron Laser Photoinjector | electron, cathode, acceleration, electromagnetic-fields | 633 |
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|||
Based on Lienard-Weichert method of retarded potentials and the potential due to the image of charges on the cathode, a rigorous relativistic description of the beam transport inside the rf-photoinjector is presented. The velocity dependent effects are explicitly taken into account in a complete analytical description. Simulations are presented for parameters of the ELSA photo-cathode. |
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TUP099 | Design and Optimization of an S-Band Photoinjector | gun, emittance, solenoid, laser | 636 |
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|||
Many X-ray Free Electron Laser (XFEL) projects are under construction or are being proposed. A photoinjector with low transverse emittance is one of the key elements for successful XFEL operation. For the last two decades, photoinjectors have been developed to reach the XFEL requirement, typically with a normalised emittance of 1 mm mrad for a 1 nC bunch and high peak current. Here, we make a further numerical optimization of an S-band photoinjector to achieve 0.5 mm mrad for 1 nC bunch in a structure that should permit high repetition rates to be achieved. Optimizations for alternative operation conditions with lower charge and lower emittance are also shown. |
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TUP105 | Simulation of the Upgraded Photoinjector for the 10 kW JLAB IR-FEL | laser, emittance, simulation, FEL | 649 |
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|||
Funding: Work supported by the Department of Defense under contract N00014-06-1-0587 with Northern Illinois University |
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TUP108 | Initial RF Measurements of the CW Normal-Conducting RF Injector | coupling, vacuum, FEL, cathode | 656 |
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Funding: This work is supported by ONR and HEL-JTO. |
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TUP110 | Modeling of a Low Frequency SRF Electron Gun for the Wisconsin FEL | emittance, gun, cathode, FEL | 658 |
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|||
Funding: This work is supported by the University of Wisconsin-Madison and MIT, and by the US NSF under award No. DMR-0537588 * O.J. Luiten, et al., Phys. Rev. Lett., 93, 094802-1 (2004) |
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TUP112 | Laser Timing Jitter Measurements at the Fermilab A0 Photoinjector | laser, electron, linac, emittance | 664 |
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|||
The Fermilab A0 Photoinjector is a 16 MeV high-intensity, low emittance electron linac used for advanced accelerator R&D. To achieve a high quality beam here it is important to maintain a stable laser in terms of both intensity and timing. This paper presents our measurement of the laser timing jitter, which is the random late or early arrival of the laser pulse. The seed laser timing jitter has been measured to less than 200 fs, by examining the power spectrum of the signal of a fast photodiode illuminated by it. The pulsed and pumped laser timing jitter has been measured with limited resolution to less than 1.4 ps, by examining the phase of a cavity impulsively excited by the signal from a fast photodiode illuminated by the laser pulse. |
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TUP113 | Emittance Exchange at the Fermilab A0 Photoinjector | emittance, optics, dipole, electron | 667 |
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Funding: This manuscript has been authored by Fermi Research Alliance, LLC under Contract No. DE-AC02-07CH11359 with the U.S. Department of Energy. |
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TUP117 | Development of Ultra-Low Emittance Injector for Future X-Ray FEL Oscillator | emittance, linac, electron, gun | 676 |
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|||
Funding: This work was supported by the U.S. Department of Energy, Office of Science, under Contract No. DE-AC-02-06CH11357. *K.-J. Kim, Y. Shvyd'ko, and S. Reiche, to be published in Physical Review Letters (2008) |
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WE102 | High Average Current SRF Cavities | storage-ring, linac, HOM, luminosity | 693 |
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|||
Higher-order-mode (HOM) free superconducting (SC) single cell cavities were developed for the rf system of high luminosity storage ring colliders. Because of the successful results of these cavities under ampere-class beams, the components and technology of the SC cavities have immediately been applied to the middle sized storage rings upgrading the beam intensity by using a few SC cavities. Beside the storage ring rf, a SC based high intensity proton linac was commissioned for neutron physics. Recently, the feasibility study of energy recovery linacs has been carried at various laboratories aiming for the 4th generation light source. Status of these developments will be described. |
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WE103 | First Results from the ERL Prototype (ALICE) at Daresbury | gun, linac, vacuum, cathode | 694 |
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|||
The energy recovery linac prototype at Daresbury is now called ALICE (Accelerators and Lasers In Combined Experiments). This paper presents the results obtained in the past year, including the second (fourth) period of gun commissioning. Following the completion of gun commissioning in November 2007, the dedicated gun diagnostic line was removed and the electron gun attached to the booster cavity and hence the rest of the machine. The paper outlines some of the challenges experienced during the commissioning of both the photoinjector system and the superconducting cavities and presents the current status of the project as well as the very latest results from commissioning during the summer of 2008. |
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WE104 | First Tests of the Cornell University ERL Injector | laser, gun, emittance, cathode | 699 |
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Funding: Work supported by the National Science Foundation under contract PHY 0131508 |
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WE105 | RF Control of High QL Superconducting Cavities | controls, feedback, resonance, linac | 704 |
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Funding: Authored by Jefferson Science Associates, LLC under U.S. DOE Contract No. DE-AC05-06OR23177. |
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WE202 | Operational Experience with High Power Beams at the SNS Superconducting Linac | linac, beam-losses, neutron, injection | 710 |
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|||
The latest operational experiences of the SNS 1 GeV superconducting H- linac will be presented as the beam power is increased and losses and beam halo become more important. The talk will include a comparison of the advantages and disadvantages of superconducting cavities. For example, issues arising from the use of different sets of SC cavities at different times will be described, along with the operational consequences on emittance and halo development. |
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WE204 | IH-DTL as a Compact Injector for a Heavy-Ion Medical Synchrotron | linac, DTL, rfq, ion | 715 |
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|||
An interdigital H-mode structure drift tube linac (IH-DTL) with alternating phase focusing (APF) has been developed downstream of a 4-vane type RFQ linac at the National Institute of Radiological Sciences as a compact injector for a heavy-ion medical synchrotron. The rf frequency of both linacs is 200 MHz, and the total length of the two linacs is less than 6 m. They can accelerate heavy ions having a charge to mass ratio of 1/3 up to 4 MeV/u. The accelerated current of 12C4+ is as high as 380 electric μA, and beam transmission through the APF IH-DTL is better than 96%. This compact injector-linac scheme might give a possible solution for a compact cancer therapy facility with heavy-ion beams. |
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TH101 | Superconducting RF R&D Toward High Gradient | niobium, SRF, HOM, superconducting-cavity | 725 |
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|||
High-beta superconducting rf elliptical cavities are being developed in large numbers for several accelerator projects including the International Linear Collider (ILC). In recent years, the understanding of cavity performance limitations has improved significantly, leading to better than 40 MV/m in some cavities. However, further improvement is needed to reach reliably the 31.5 MV/m operating gradient proposed for the ILC Main Linac cavities. World-wide R&D on the cavity gradient frontier includes improved surface cleaning and smoothing treatments, development of alternative cavity shapes and materials, and novel cavity manufacturing techniques. Substantial progress has been made with diagnostic instrumentation to understand cavity performance limitations. Some highlights of the efforts in superconducting rf R&D toward achieving higher gradients in high-beta elliptical cavities are reviewed. |
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TH102 | SRF Developments for Ion Acceleration | linac, cryomodule, ion, niobium | 730 |
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|||
The talk will provide an overview of the SRF development toward the acceleration of light and heavy ions including QWRs, HWRs, spoke and CH cavities. |
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TH103 | Developing Facilities for SNS Cryomodule Performance Improvements | cryomodule, linac, radiation, shielding | 735 |
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Funding: SNS is managed by UT-Battelle, LLC, under contract DE-AC05-00OR22725 for the U.S. Department of Energy |
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TH202 | Heavy Ion Linac Booster at IUAC, New Delhi | linac, niobium, acceleration, ion | 749 |
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|||
The first module of the booster superconducting linear accelerator, consisting of a total of three modules, each having 8 quarter wave coaxial line bulk Nb resonators, has been commissioned at IUAC. During initial operation of the first linac module, the energy gain was found to be much lower due to various problems which are now identified and solved. After acceleration through the linac module and subsequent re-bunching using a superconducting Rebuncher, a 158 MeV silicon beam having pulse width of 400 ps was delivered to conduct nuclear physics experiments. The other two linac cryostats and the required 16 resonators to be installed in those two cryostats are in the final stage of fabrication. Work has progressed on a high current injector that would act as an alternate source of heavy ions for the superconducting linac. The first element of the high current injector is a high Tc superconducting magnet ECR source (PKDELIS) which would be followed by a room temperature radio frequency quadrupole accelerator and drift tube linac cavities. Prototypes of the RFQ working at 48.5 MHz, and that of the DTL working at 97 MHz, have been fabricated and are undergoing tests. |
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TH204 | Student Prize Winner Talk - Twisted Structures and Their Application as Accelerating Structures | 759 | |
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Funding: This work has been sponsored by ORNL-SNS. The Spallation Neutron Source is managed by UT-Battelle, LLC, under contract DE-AC05-00OR22725 for the U.S. Department of Energy. |
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|
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TH301 | Beam Dynamics Studies of the 8 GeV Linac at FNAL | linac, simulation, focusing, proton | 760 |
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Funding: This work was supported by the U.S. Department of Energy, Office of Scince, under contracts number DE-AC02-06CH11357 and No. W-31-109-ENG-38. |
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|
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THP001 | Nb-RRR Sheet Inspection by Means of Ultrasonic Microscopy | niobium, electron, diagnostics, superconducting-RF | 771 |
|
|||
Nb-RRR sheet material is one of the key components of super conducting linear particle accelerator projects (e.g. XFEL, ILC). The high quality requirements led to sophisticated quality systems in the manufacturing line. A major aspect is the development of non-destructive inspection methods for the detection of surface defects, delaminations, and inclusions. Up to now the standard inspection technologies for quality assurance of Nb-RRR sheet material are based on electromagnetic techniques, e.g. SQUID and eddy current. For these methods the detection limit is in the range of 0.1 mm. Ultrasonic microscopy (USM) in the frequency range of 1 GHz is a well established and economic technique for non-destructive surface inspection. For volume inspection of sheet material ultrasonic frequencies of 50 to 100 MHz are applied. For Nb-RRR sheets with typical thickness of 2.8 mm a detection limit of 0.1 mm is expected. First results of USM on Nb-RRR sheet material are presented. |
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THP002 | The 1.3 GHz Superconducting RF Program at TRIUMF | linac, TRIUMF, controls, ISAC | 774 |
|
|||
TRIUMF is proposing to build a 50 MeV electron linac as a driver to produce radioactive ion beams through photofission. The present design calls for the use of nine-cell 1.3 GHz Tesla type cavities. A 1.3 GHz Superconducting RF (SRF) program has been initiated with the goal to produce and test one nine cell cavity by the end of 2009. The program will utilize the existing clean room and SRF test facilities that support the ISAC-II heavy ion superconducting linac. A vertical cryostat has been modified with a new insert to allow single cell testing. Pumps for 2 K sub-atmospheric operation have been tested. A single cell fabrication program is being initiated with a local company. A RRR measurement program is on-going to test cavity welds. The goal of the 1.3 GHz upgrade is to not only produce cavities for the in house project but to broaden TRIUMF's technical base for future potential collaborations. The paper will report the progress and plans of the 1.3 GHz SRF program. |
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|
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THP003 | Production and Testing of Two 141 MHz Prototype Quarter Wave Cavities for ISAC-II | ISAC, acceleration, TRIUMF, linac | 777 |
|
|||
The medium beta section of the ISAC-II superconducting linac (β=5.7% and 7.1%) has been operational since April 2006 providing 20 MV of accelerating potential at 106 MHz. The ‘high beta' extension to the linac, in progress, will see the addition of twenty 141 MHz quarter wave cavities at β=11%. The design specification calls for cw operation at a voltage gain of at least 1.1 MV/cavity for no more than 7 W of power dissipated in the cavity. This operation point corresponds to challenging peak surface fields of 30 MV/m and 60 mT. The cavity design is similar in concept to the medium beta cavities except for the addition of a drift tube to render symmetric the accelerating fields. A prototyping and qualification program was initiated with PAVAC Industries Inc. of Richmond, B.C. Two full size models in copper and two in niobium have been completed. The niobium cavities have been warm and cold-tested and characterized for frequency, rf performance and mechanical stability. The cold performance of both cavities exceeds the specification and the final frequency is within tuning range. The design, fabrication details and test results will be presented. |
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THP004 | Performance of the ISAC-II 141 MHz Solid State Amplifier | linac, ISAC, superconducting-cavity, rf-amplifier | 780 |
|
|||
The ISAC-II linac extension requires an additional 20 rf amplifiers to power twenty 141 MHz quarter wave superconducting cavities. Solid state amplifiers will be used for this extension as compared to tube amplifiers which have been employed for the existing ISAC-II linac section, operational since 2006. The amplifiers are specified to run with an output power of 600 W. The first amplifier of the production series has been tested for gain and phase linearity. Phase noise of this amplifier has been measured on a 141 MHz superconducting cavity and compared with phase noise measured with a tube amplifier. The test results and general rf, interlock and interface requirements are verified against tendered specification before series production of the remaining amplifiers can proceed. Benchmarking tests of the prototype amplifier will be reported. |
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THP005 | Tests of Wire Sublimations Very Close to SPIRAL 2 Superconducting Cavity | cryomodule, diagnostics, linac, vacuum | 783 |
|
|||
The construction of the new Spiral 2 facility has started in Caen (France) at the National Heavy Ions Accelerator Center (GANIL). The SPIRAL 2 project is based on a multi-beam Superconducting Linac Driver delivering 5 mA deuterons up to 40 MeV and 1 mA heavy ions up to 14.5 MeV/u delivering different Radioactive Isotope Beams (RIB). The LINAC is composed of 2 cryomodule families. The low energy family (cryomodules A) is composed of 12 cryomodules housing a single cavity at beta=0.07. The "high" energy family (cryomodules B) is composed of 7 cryomodules housing 2 cavities at beta=0.12. In between cryomodules are located the focalisation quadrupoles and the diagnostic boxes. Strong beliefs forbid the use of interceptives diagnostics around superconducting cavities. We simulated the use of wires for diagnostics in the linac, sublimating 14 wires of tungsten, Niobium and carbon while operating the B cavity at full performances. The first results describe in this paper looks promising. |
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THP006 | 704 MHz High Power Coupler and Cavity Development for High Power Pulsed Proton Linacs | proton, linac, vacuum, superconductivity | 786 |
|
|||
In the framework of the European CARE-HIPPI program we develop components for superconducting high pulsed power proton linacs at 704 MHz. We have designed, fabricated and tested a beta 0.47 5-cell elliptical cavity with an optimized stiffening to reduce its sensitivity to Lorentz forces. A fast piezo tuner has been developed in order to be able to operate the cavity in pulsed mode in our horizontal test cryostat CryHoLab. We also have carried out the development of a fundamental power coupler. It is designed to transmit a power up to 1 MW at a 10% duty cycle. A high power test area has been setup consisting of a 1.2 MW klystron, a pulsed high voltage power supply and a coupler test stand. |
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THP008 | A Novel Frequency Tuning System Based on Movable Plunger for SPIRAL2 High-Beta Superconducting Quarter-Wave Resonator | cryomodule, niobium, simulation, insertion | 789 |
|
|||
SPIRAL2 aims at building a multi-purpose facility dedicated to nuclear physics studies, including the production of rich-neutrons isotopes. The multi-beam linear accelerator is composed of superconducting accelerating modules and warm focusing magnets. IPN Orsay is in charge of the high energy accelerating modules, each hosting two superconducting (β = 0.12) quarter-wave resonators operating at an accelerating field of 6.5 MV/m at 88 MHz. The static and dynamic frequency tuning is achieved by the insertion and motion of a niobium plunger into the magnetic field area. The efficiency of the tuning (1 kHz/mm) has been validated during the tests of the cryomodule. In this paper we discuss the impact of such a tuning system, based on experimental results on Spiral2 cavities, on the different aspects: maximum accelerating field, Qo slopes, quench, multipacting and microphonics. |
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THP009 | RF and Cryogenic Tests of the First Beta 0.12 SPIRAL2 Cryomodule | cryomodule, vacuum, cryogenics, linac | 792 |
|
|||
The SPIRAL2 project, installed in GANIL for Radioactive Ion Beam physics purposes requires the manufacturing of a multi beam driver. This driver is based on a superconducting Linac featuring two 88 MHz Quarter Wave Resonator families. IPN Orsay is in charge of the study and the assembly of the 7 high energy (beta = 0.12) cryomodules. Each cryomodule is composed of two QWRs, specified to operate at 4.2 K with a nominal accelerating gradient of 6.5 MV/m. A first qualifying cryomodule has been manufactured and tested at the beginning of 2008 in order to validate the resonator and the cryostat design before launching the serial production of the 6 remaining cryomodules. The paper presents the main results of this test and the cryomodule design in its final version. |
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THP010 | Influence of Piezo-Hysteresis and Resolution on Cavity Tuning | feedback, resonance, controls, linac | 795 |
|
|||
Funding: Work partially funded by the EU Commission in the sixth framework programme, contract no 011935 EURO-FEL-DS5, BMBF and Land Berlin. |
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THP011 | Recent Developments on Superconducting CH-Structures and Future Perspectives | linac, rfq, DTL, proton | 797 |
|
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Funding: GSI, BMBF contr. No. 06F134I, EU contr. No. 516520-FI6W, RII3-CT-2003-506395, EFDA/99-507ERB500CT990061 |
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THP012 | Nondestructive Testing of Niobium Sheets for SRF Cavities Using Eddy-current and SQUID Flaw Detection | niobium, controls, superconductivity, neutron | 800 |
|
|||
For more than 10 years DESY has been operating a high resolution eddy-current scanning installation with rotating table for nondestructive flaw detection on niobium sheets for SRF cavities. More than 2000 sheets have been examined up to now, several types of defects have been detected and identified using different supplementary methods such as EDX, X-ray fluorescence, neutron activation analysis etc. In order to scan Nb-sheets needed for XFEL-cavity production, new scanning devices have to be build. One option of the eddy-current installations could be an application of SQUID-sensors due to much higher sensitivity instead of conventional probes. A SQUID based scanner system was built and is in evaluation at DESY. A status report will be given. |
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THP013 | Various Applications of Dry-Ice Cleaning in the Field of Accelerator Components at DESY | gun, cathode, SRF, superconductivity | 803 |
|
|||
Funding: We acknowledge the support of the European Community Research Infrastructure Activity under FP6 'Structuring the European Research Area' program (CARE, contract number RII-CT-2003-506395 |
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THP014 | Recent Results of 1.3 GHz Nine-Cell Superconducting Cavities for the European XFEL | HOM, niobium, superconductivity, superconducting-cavity | 806 |
|
|||
In preparation for the series production of roughly 800 superconducting accelerating structures, several tests with an industrial-like production sequence have been tested for their accelerating gradient and quality factor. The main part of the surface preparation is being done with electropolishing. with ethanol rinse. For the two different final preparation steps namely electropolishing and etching the performance is compared. The results will be also put into the perspective of earlier cavity production cycles that were tested at DESY. |
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THP015 | Open 120C Bake in Argon Atmosphere: A Simplified Approach for Q-Drop Removal | vacuum, niobium, superconducting-cavity, controls | 809 |
|
|||
The removal of the Q-drop without field emission by a low temperature (app. 120C) bake procedure is essential in order to achieve the full performance in both electropolished (EP) and chemically etched (BCP) high gradient SCRF Nb accelerator cavities. A simplified procedure applying an open 120C bake out in an Argon atmosphere is presented. First results are compared to the well-established bake-out procedure under vacuum conditions. |
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THP016 | Analysis of Quenches Using Temperature Mapping in 1.3 GHz SCRF Cavities at DESY | superconducting-cavity, superconductivity, electron, synchrotron | 812 |
|
|||
The local thermal breakdown (quench) behavior of one- and nine-cell SCRF Nb accelerator cavities is investigated systematically. For more than 50 cavities, temperature mapping data have been analyzed with respect to surface preparation, Nb material etc. Results on quench location and characteristic correlations are presented. |
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THP018 | Successful Qualification of the Coaxial Blade Tuner | simulation, insertion, superconducting-cavity, SRF | 818 |
|
|||
Cavity tuners are needed to precisely tune the narrow-band resonant frequency of superconducting cavities. The Blade Tuner presented is installed coaxially to the cavity and changes the resonator frequency by varying its length. Piezoceramic actuators add dynamic tuning capabilities, allowing fast compensation of main dynamic instabilities as Lorentz Forces, under pulsed operations, and microphonic noise. A prototype piezo Blade Tuner has been assembled on a TESLA cavity and extensively cold tested inside the horizontal cryostats CHECHIA (DESY) and HoBiCaT (BESSY). Then, as suggested by results, a few minor modifications have been implemented thus achieving the current Blade Tuner design. The introduction of thicker blades re-distributed along the circumference allows to increase its stiffness and fulfill European and American pressure vessel codes, while ensuring requested performances and cost. The paper will present the successful characterization tests performed on the prototype, the extensive mechanical analyses made to validate the final model and the results from qualification tests of first revised Blade Tuner produced, to be installed in the second module of ILCTA at FNAL. |
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THP019 | Third Harmonic Superconducting Cavity Prototypes for the XFEL | linac, cryomodule, HOM, pick-up | 821 |
|
|||
The third harmonic cavities that will be used at the injector stage in the XFEL to linearize the rf curvature distortions and minimize beam tails in the bunch compressor are based on the rf structures developed at FNAL for the DESY FLASH linac. The design and fabrication procedures have been modified in order to match the slightly different interfaces of XFEL linac modules and the procedures followed by the industrial production of the main (1.3 GHz) XFEL cavities. A revision of the helium vessel design has been required to match the layout of the cryomodule strings, and a lighter version of the tuner has been designed (derived from the 1.3 GHz ILC blade tuner activities). The main changes introduced in the design of the XFEL cavities and the preliminary experience of the fabrication of three industrially produced and processed third harmonic rf structures are described here. |
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THP021 | Development of Inspection Systems for Superconducting Cavities | superconducting-cavity, accelerating-gradient, cryogenics, controls | 824 |
|
|||
Inspections of superconducting rf cavities seem essential in achieving high achieving gradient. The inspection of interior surface of a superconducting rf cavity with high enough resolution to find defects more than several tens microns is achieved by our high resolution camera system. This system revealed undiscovered defects at just inner sides of the locations predicted by passband-mode and thermometry measurements. This system will help to improve cavity fabrication processs and their yield. This system will be delivered world wide for that purpose. We are planning to widen our activity in this field: developments of new termometry system with easy installation and less cabling and high sensitivity Eddy Current Surface Inspection system for bare niobium sheets. The detailed systems and some preliminary data obtained from the systems will be presented. |
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THP022 | SC Nb Sputtered QWRs for the REX-ISOLDE Accelerator at CERN: Prototype Design and Manufacturing | niobium, linac, vacuum, simulation | 827 |
|
|||
The HIE-ISOLDE activity aims at the construction of a superconducting linac based on 101.28 MHz Nb sputtered Quarter Wave Resonators (QWRs), which will be installed downstream the present REX-ISOLDE linac. The present design considers two basic geometries of the cavities (geometric β0 = 6.26% and 10.84%) for which a mechanical, chemical treatment and Nb coating design study has been performed. We report here on the status of the prototype cavity and sputtering tests. |
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THP023 | Crab Cavities for Linear Colliders | dipole, collider, beam-loading, linac | 830 |
|
|||
Crab cavities have been proposed for a wide number of accelerators and interest in crab cavities has recently increased after the successful operation of a pair of crab cavities in KEK-B. In particular crab cavities are required for both the ILC and CLIC linear colliders for bunch alignment. Consideration of bunch structure and size constraints favours a 3.9 GHz superconducting, multi-cell cavity as the ILC solution, whilst bunch structure and beam-loading considerations suggest an X-band copper travelling wave structure for CLIC. These two cavity solutions are very different in design but share complex design issues. Phase stabilisation, beam loading, wakefields and mode damping are special issues for these crab cavities. Requirements and potential design solutions will be discussed for both colliders. |
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THP024 | Initial Study on the Shape Optimisation of the CLIC Crab Cavity | impedance, dipole, beam-loading, coupling | 833 |
|
|||
The CLIC linear collider will require a crab cavity to align bunches prior to collision. Consideration of the bunch structure leads us to favour the use of X-band copper cavities. Due to the large variation of train to train beam loading, it is necessary to minimise the consequences of beam loading. One solution is to use a travelling wave structure with a large group velocity allowing rapid propagation of amplitude errors from the system. Such a design makes this structure significantly different from previous travelling wave deflecting structures. This paper will look at the implications of this on other cavity parameters and the optimization of the cavity geometry. |
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THP025 | Superconducting Quarter-Wave Resonators for the ATLAS Energy Upgrade | cryomodule, linac, niobium, coupling | 836 |
|
|||
A set of six new 109 MHz β=0.15 superconducting quarter-wave resonators (QWR) has been built at ANL as part of an upgrade to the ATLAS superconducting heavy-ion linac. The final cavity string assembly will also use many of the techniques needed for the next generation of large high-performance ion linacs such as the U.S. Department of Energy's FRIB project. Single-cavity cold tests at T=4.5 K have been performed for three cavities with moveable coupler, rf pickup, and VCX fast tuner as required for the full 6-meter cryomodule assembly. The average maximum accelerating gradient of 4 cavities (3 new + 1 prototype), is EACC=11.2 MV/m (BPEAK=65 mT). Clean cavity string assembly techniques, required here and for most future SRF ion linacs, are fairly well developed. Details on cavity performance including high-field cw operation, microphonics and fast tuning are presented. |
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THP026 | Surface Processing Facilities for Superconducting RF Cavities at ANL | linac, controls, cathode, niobium | 839 |
|
|||
New SRF cavity processing systems at ANL, including those for electropolishing (EP), high-pressure water rinsing (HPR), and single-cavity clean room assembly have been developed and operated at ANL for use with cavities for a range of electron and ion linac applications. Jointly with FNAL, systems for 1.3 GHz single- and multi-cell elliptical cavities for the linear collider effort have been developed. New systems for use with low-beta TEM-class cavities have also been built and used to process a set of new quarter-wave resonators as part of an upgrade to the ATLAS heavy-ion accelerator at ANL. All of the new hardware is located in a 200 m2 joint ANL/FNAL Superconducting Cavity Surface Process Facility (SCSPF) consisting of two separate chemical processing rooms, a clean anteroom, and a pair of class 10 and 100 clean rooms for HPR and clean assembly. Results of first cold tests for elliptical and TEM-class cavities processed in these facilities are presented. |
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THP027 | Welding Helium Vessels to the 3.9 GHz Superconducting Third Harmonic Cavities | electron, monitoring, cryomodule, emittance | 842 |
|
|||
Funding: This work was supported by Fermilab Research Alliance, LLC under Contract No. DE-AC02-07CH11359 with the United States Department of Energy. |
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THP028 | Status of 3.9 GHz Superconducting RF Cavity Technology at Fermilab | HOM, alignment, cryomodule, status | 845 |
|
|||
Funding: Operated by Fermi Research Alliance, LLC under Contract No. DE-AC02-07CH11359 with the United States Department of Energy. |
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|
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THP029 | Performance of 3.9-GHZ Superconducting Cavities | HOM, superconductivity, status, SRF | 848 |
|
|||
Funding: Operated by Fermi Research Alliance, LLC under Contract No. DE-AC02-07CH11359 with the United States Department of Energy. |
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THP030 | High Gradient Test Results of 325 MHz Single Spoke Cavity at Fermilab | vacuum, linac, simulation, accelerating-gradient | 851 |
|
|||
The High Intensity Neutrino Source (HINS) project represents the current effort at Fermilab to develop 60 MeV Proton/H- Linac as a front end for possible use in the Project X. Eighteen superconducting β=0.21 single spoke resonators (SSR), operating at 325 MHz, comprise the first stage of the HINS cold section. Two SSR cavities have now been fabricated in industry under this project and undergone surface treatment that is described here. We report the results of high gradient tests of the first SSR in the Vertical Test System (VTS). The cavity successfully achieved accelerating gradient of 13.5 MV/m; higher than the design operating gradient of 10 MV/m. The history of multipacting and conditioning during the VTS tests will be discussed. Experimental measurements of the cavity mechanical and vibration properties including Lorenz force detuning and measurements of X-rays resulting from field emission are also presented. |
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THP033 | Superconducting Quarter-Wave Resonator Cavity and Cryomodule Development for a Heavy Ion Re-accelerator | cryomodule, solenoid, ion, superconductivity | 854 |
|
|||
A superconducting linac is being planned for re-acceleration of exotic ions produced by the Coupled Cyclotron Facility at Michigan State University. The re-accelerator will include a gas stopper, a charge breeder, a normal conducting radio-frequency quadrupole, and two types of superconducting quarter-wave resonators (QWRs) for re-acceleration to energies of up to 3 MeV per nucleon initially, with a subsequent upgrade path to 12 MeV per nucleon. The QWRs (80.5 MHz, optimum beta = 0.041 and 0.085, made from bulk niobium) are similar to existing cavities presently used at INFN-Legnaro. The re-accelerator's cryomodules will accommodate up to 8 cavities, along with superconducting solenoids for focussing. Active and passive shielding is required to ensure that the solenoids' field does not degrade the cavity performance. First prototypes of both QWR types have been fabricated and tested. A prototype solenoid has been procured and tested. A test cryomodule has been fabricated: one QWR, one solenoid, and two other beam line elements have been installed inside. This paper will cover the re-accelerator cavity and cryomodule prototyping efforts, results so far, and future plans. |
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|
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THP034 | CW RF Systems of the Cornell ERL Injector | LLRF, klystron, controls, cryogenics | 857 |
|
|||
Funding: Work is supported by the National Science Foundation grant PHY 0131508. |
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THP035 | Multipactor in Minimum Electric Field Regions of Transmission Lines and Superconducting RF Cavities | electron, multipactoring, simulation, superconducting-RF | 860 |
|
|||
Funding: Work is supported by the National Science Foundation grant PHY 0131508 *S. Belomestnykh and V. Shemelin, "Multipacting-free Transitions between Cavities and Beam-pipes," submitted to Nuclear Instruments and Methods in Physics Research A. |
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THP036 | Oscillating Superleak Transducers for Quench Detection in Superconducting ILC Cavities Cooled with He-II | accelerating-gradient, heavy-ion, ion, booster | 863 |
|
|||
Funding: DOE and NSF |
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|
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THP038 | A New SRF Cavity Shape with Minimized Surface Electric and Magnetic Fields for the ILC | HOM, dipole, coupling, wakefield | 867 |
|
|||
Funding: Work supported by DOE contract DE-AC02-76SF00515. |
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|
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THP039 | SRF Cavity Imperfection Studies Using Advanced Shape Uncertainty Quantification Tools | cryomodule, SRF, dipole, HOM | 870 |
|
|||
Funding: Work supported by DOE contract DE-AC02-76SF00515. |
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THP040 | A New TEM-Type Deflecting and Crabbing RF Structure | impedance, simulation, vacuum, damping | 873 |
|
|||
Funding: Supported by US DOE Contract No. DE-AC05-06-OR23177 |
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THP041 | Analysis of Electronic Damping of Microphonics in Superconducting Cavities | feedback, damping, superconducting-cavity, coupling | 876 |
|
|||
Funding: Supported by US DOE Contract No. DE-AC05-06OR23177 |
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THP042 | High-Gradient SRF R&D for ILC at Jefferson Lab | SRF, cathode, instrumentation, niobium | 879 |
|
|||
Funding: Supported by DOE |
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|
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THP043 | Preliminary Results from Multi-Cell Seamless Niobium Cavities Fabricated by Hydroforming | niobium, cryogenics, vacuum, electron | 882 |
|
|||
Funding: This manuscript has been partially authored by Jefferson Science Associates, LLC under U.S. DOE Contract No. DE-AC05-06OR23177. |
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THP044 | Coaxial Coupling Scheme for Fundamental and Higher Order Modes in Superconducting Cavities | coupling, damping, HOM, superconducting-cavity | 885 |
|
|||
Funding: This manuscript has been authored by Jefferson Science Associates, LLC under U.S. DOE Contract No. DE-AC05-06OR23177. |
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THP045 | Twisted Structures and Their Application as Accelerating Structures | simulation, superconducting-cavity, electron | 888 |
|
|||
Funding: This work has been sponsored by ORNL-SNS. The Spallation Neutron Source is managed by UT-Battelle, LLC, under contract DE-AC05-00OR22725 for the U.S. Department of Energy. |
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THP047 | Design of the MEBT Rebunchers for the SPIRAL2 Driver | rfq, simulation, ion, linac | 894 |
|
|||
The SPIRAL2 project uses a RFQ, normal conducting rebunchers and a superconducting linac to accelerate high intensity beams of protons, deuterons and heavier ions. All cavities work at 88 MHz, the beta after of the RFQ is 0.04 and 3 rebunchers are located in the MEBT line, which accepts ions with A/q up to 6. The paper describes the RF design and the technological solutions proposed for an original 3-gap cavity, characterised by very large beam holes (60 mm) and providing up to 120 kV of effective voltage. |
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THP048 | RF Power Amplifiers for the SPIRAL2 Driver: Requirements and Status | rfq, linac, controls, LLRF | 897 |
|
|||
The SPIRAL2 project uses an RFQ, normal conducting rebunchers and a superconducting linac to accelerate high intensity beams of protons, deuterons and heavier ions. All cavities work at 88 MHz, are independently phased and powered by amplifiers whose power ranges from a few kW to 250 kW. The paper describes the amplifier requirements, the proposed solutions and their status. |
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THP049 | Optimization of Spiral-Loaded Cavities Using the 3D Code OPERA/SOPRANO | resonance, simulation, impedance, insertion | 900 |
|
|||
Rebunching cavities are today routinely used for matching a beam of charged particles between different accelerator structures, and thus optimizing the overall transmission and beam quality. At low resonance frequencies, unnecessary large dimensions of these cavities can be avoided by using spiral-loaded cavities. The optimization of these structures is a complicated process in which a wide range of different parameters have to be modified essentially in parallel. In this contribution, we investigate in detail the characteristics of a model structure with the 3D code OPERA/SOPRANO. This includes the optimization of the structure in terms of the spiral geometry for a given resonance frequency, the investigation of power losses on the inner surfaces, and the possibility of cavity tuning by means of a tuning cylinder. |
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THP052 | Development of a High-Pressure Chemical Etching Method as a Surface Treatment for High-Field Accelerating Structures Made of Copper | cathode, gun, acceleration, RF-structure | 903 |
|
|||
The acceleration gradient is limited by breakdown in an accelerating rf structure, including its surface condition of the inner wall. The surface treatment is an important technique to achieve the maximal acceleration gradient of an accelerating structure. We chose chemical etching as a method of surface treatment for accelerating rf structures made of copper. To study rf breakdown and effect of surface treatments, we used a pillbox-type single cell rf gun cavity. The highest cathode surface field (190 MV/m) of rf gun cavity was accomplished with this surface treatment under rf-conditioning elapsed time (21 days) in 2004. SPring-8 rf gun has been operating with the highest gradient in the world. This indicates that our treatment is considerably effective to improve the inner cavity surface made of copper. Further, we developed the high-pressure chemical etching for more complicated inner structures in 2006. Using a cartridge-type photocathode rf gun, high-field experiments were performed with cathode plugs chemical etching treated under deferent pressure condition. We report these results on highest gradient, using test copper samples treated with high-pressure chemical etching. |
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THP054 | Status of RF Sources in Super-Conducting RF Test Facility (STF) at KEK | controls, LLRF, cryomodule, klystron | 909 |
|
|||
Phase 0.5 and Phase 1.0 of the Superconducting RF Test Facility (STF) have been developed since 2005 in KEK. We have completed the two rf-sources and they have been used for the evaluation for the components of power distribution system (PDS) and couplers which were installed in the 5m-cryomodules. We have developed some rf components which is used in the power distribution system(PDS). Phase 1.0 have been conducted now and we attempt the R&D of PDS required in ILC project. This report describes the recent status of the rf source of STF in KEK including the modulator, PDS and LLRF. |
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THP056 | Improvement in the ACS Cavity Design for the J-PARC Linac Energy Upgrade | coupling, linac, simulation, background | 915 |
|
|||
The ACS (Annular-ring Coupled Structure) cavities were under development for the J-PARC Linac from 190 MeV to 400 MeV. We have fixed the cavity specification, taking into account the results of the high-power conditioning and the fabrication experience. The mass production of the ACS with a tight time schedule is now an issue, since the user community strongly requests the beam power upgrade as early as possible. Therefore, the design and the fabrication process of the ACS cavity have been reexamined on the basis of the experience, stored during the course of the fabrication and the tuning of the prototype ACS tanks. Here, we also discussed about the key issues on the mass production with a manufacturer. The cavity shape, that required complicated machining, was simplified to some extent, while the frequency tuning strategy was reconsidered to reduce the production period. The paper describes these recent activities on the ACS development. |
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THP057 | Development of RF Cavities for the SHB System of the L-band Electron Linac at Osaka University | linac, resonance, electron, single-bunch | 918 |
|
|||
Funding: This research is partly supported by the accelerator support program to universities conducted by the High Energy Accelerator Research Organization in Japan. |
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THP058 | Accelerating Structure for C-Band Electron Linear Accelerator Optimization | impedance, electron, coupling, vacuum | 921 |
|
|||
The results of analysis and comparison of different linear accelerator designs for 10 MeV facility powered by 4.5 MW klystron on 5712 MHz operation frequencies presented. Several concepts of accelerator including standing wave and traveling wave ones with either rf or magnetic focusing were considered. Cells geometry and beam dynamics parameters in these types of accelerators featuring high capture factor were obtained using numeric simulation methods. The computer simulation code for traveling wave linac optimization based on beam dynamics with space charge consideration was developed. Accelerating structures and input coupler for traveling wave linac along with standing wave one were designed. The task of energy variation was solved. |
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THP060 | Room Temperature Accelerating Structure for Heavy Ion Linacs | DTL, rfq, ion, linac | 927 |
|
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In this report we consider room temperature DTL structure for heavy ions acceleration in energy range 150 keV/u - 400 keV/u. The structure design is based on known and proven solutions. Due to design idea, the structure has no end wall problem. It allows flexible segmentation in cavities and transverse focusing elements placing outside cavity. As compared to well known IH DTL, considered structure has smaller transverse dimensions and is designated for lower operating frequency. The structure promises high rf efficiency - with careful elements optimization calculated effective shunt impedance value is higher than 1.0 GOhm/m for operating frequency ~ 70 MHz, E~150 keV/u. |
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THP064 | Development Status of the Pi-Mode Accelerating Structure (PIMS) for Linac4 | coupling, linac, impedance, vacuum | 939 |
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The high-energy section of Linac4, between 100 and 160 MeV, will be made of a sequence of 12 seven-cell accelerating cavities of the Pi-Mode Structure (PIMS) type, resonating at 352 MHz. Compared to other structures used in this energy range, cavities operating in pi-mode with a low number of cells have the advantage of simplified construction and tuning, compensating for the fact that the shunt impedance is about 10% lower because of the lower frequency. Field stability in steady state and in presence of transients is assured by the low number of cells and by the relatively high coupling factor of 5%. Standardising the linac rf ystem to a single frequency is considered as an additional economical and operational advantage. The mechanical design of the PIMS will be very similar to that of the 352 MHz normal conducting 5-cell LEP accelerating cavities, which have been successfully operated at CERN for 15 years. After reviewing the basic design principles, the paper will focus on the tuning strategy, on the field stability calculations and on the mechanical design. It will also report the results of measurement on a cold model and the design of a full-scale prototype. |
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THP065 | Shunt Impedance Studies in the ISIS Linac | linac, DTL, impedance, simulation | 942 |
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The ISIS linac consists of four DTL tanks that accelerate a 50 pps, 20 mA H- beam up to 70 MeV before injecting it into an 800 MeV synchrotron. Over the last decades, the linac has proved to be a strong and reliable injector for ISIS, which is a significant achievement considering that two of the tanks are more than 50 years old. At the time the machine was designed, the limited computing power available and the absence of 3D electromagnetic (EM) simulation codes, made the creation of a linac optimized for power efficiency almost impossible, so from this point of view, the ISIS linac is quite simple by today's standards. In this paper, we make a shunt impedance comparison study using the power consumption data collected from ISIS and the results obtained when simulating each of the four DTL tanks with 2D and 3D EM codes. The comparison will allow us to check the accuracy of our simulation codes and models and to assess their relative performance. It is particularly important to benchmark these codes against real data, in preparation for their use in the design of a proposed new linac, which will replace the currently aging ISIS injector. |
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THP066 | Breakdown in Pressurized RF Cavities | electron, simulation, vacuum, emittance | 945 |
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The performance of many particle accelerators is limited by the maximum electric gradient that can be realized in rf cavities. Recent studies have shown that high gradients can be achieved quickly in 805 MHz cavities pressurized with dense hydrogen gas, because the gas can suppress, or essentially eliminate, dark currents and multipacting. In this project, two new test cells operating at 500 MHz and 1.3 GHz will be built and tested, and the high pressure technique will be used to suppress the vacuum effects of evacuated rf cavities, so that the role of metallic surfaces in rf cavity breakdown can be isolated and studied as a function of external magnetic field, frequency, and surface preparation. Previous studies have indicated that the breakdown probability is proportional to a high power of the surface electromagnetic field, in accordance with the Fowler-Nordheim description of electron emission from a cold cathode. The experiments will be compared with computer simulations of the rf breakdown process. |
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THP069 | Design and Test of the Triple-Harmonic Buncher for the NSCL Reaccelerator | rfq, emittance, linac, simulation | 948 |
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To meet the requirement of a small output longitudinal beam emittance from the reaccelerator, a triple-harmonic buncher operating at the fundamental frequency of 80 MHz upstream the Radio Frequency Quadrupole (RFQ) linac has been designed, manufactured and tested at the National Superconducting Cyclotron Laboratory (NSCL). The buncher consists of two coaxial resonators with a single gridded gap. One cavity provides both the fundamental and the third harmonic simultaneously with l/4 and 3l/4 modes respectively, while the other for the second harmonic with a l/4 mode. This buncher combines the advantages of using high quality factor resonator and only a pair of grids. Details on design considerations, electromagnetic simulations, and test results are presented. |
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THP070 | Surface-Loss Power Calculations for the LANSCE DTL | DTL, linac, vacuum, drift-tube-linac | 951 |
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The surface losses in the drift-tube linac (DTL) tanks 3 and 4 of the LANSCE linear accelerator are calculated using 3-D electromagnetic modeling with the CST MicroWave Studio (MWS). The results are used to provide more realistic power estimates for the 201.25 MHz rf upgrade design within the LANSCE-R project. We compared 3-D MWS results with those from traditional 2-D Superfish computations for DTL cells and their simplified models and found differences on the level of a few percent. The differences are traced to a 3-D effect consisting in a redistribution of the surface currents on the drift tubes (DT) produced by the DT stem. The dependence of MWS results on the mesh size used in computations is also discussed. |
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THP071 | Efficient Low-Beta H-Mode Accelerating Structures with PMQ Focusing | focusing, linac, beam-losses, quadrupole | 954 |
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We are developing high-efficiency room-temperature rf accelerating structures for beam velocities in the range of a few percent of the speed of light by merging two well-known ideas: H-mode cavities and the transverse beam focusing with permanent-magnet quadrupoles (PMQ). Combining electromagnetic 3-D modeling with beam dynamics simulations and thermal-stress analysis, we have found that the H-mode structures with PMQ focusing provide a very efficient and practical accelerator for light-ion beams of considerable currents. Such accelerating structures following a short RFQ can be used in the front end of ion linacs or in stand-alone applications such as a compact deuteron-beam accelerator up to the energy of a few MeV. |
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THP072 | Performance of a 1.3 GHz Normal-Conducting 5-Cell Standing-Wave Cavity | positron, single-bunch, injection, klystron | 957 |
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Funding: Work supported by Department of Energy contract DE-AC03-76SF00515. |
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THP073 | Progress in L-Band Power Distribution System R&D at SLAC | coupling, cryomodule, acceleration, linac | 960 |
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Funding: Work supported by the U.S. Department of Energy under contract DE-AC02-76SF00515. |
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THP076 | Last SPIRAL 2 10 kW CW RF Coupler Design | cryomodule, simulation, linac, resonance | 969 |
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The first tests of the SPIRAL 2 coupler have been done successfully in the B-cryomodule of the SPIRAL2 linac. It led to an updated design. We present the new design as well as the results of the last test and conditioning. |
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THP077 | Studies on Input Couplers for Superconducting Cavities | simulation, interlocks, vacuum, superconducting-cavity | 972 |
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Drastic conditioning time reduction was successfully achieved for the TTF-III couplers at LAL. This was carried out by a systematic study of the different parameters that play a role in the conditioning process. Moreover, many investigations were made in order to have a better understanding of the couplers behaviour. These activities represent some aspects of a larger technology program that is being developed at LAL to study power couplers and multipacting. This paper will give an overview of some of these studies, the future experiments on couplers at LAL and the development of the associated technology program. |
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THP079 | Operation Experience with the FLASH RF Waveguide Distribution System at DESY | klystron, gun, superconducting-cavity, cryogenics | 978 |
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The rf stations for the FLASH linear accelerator at DESY provide rf power up to more than 5 MW, 1.3 ms and 10 Hz at 1.3 GHz for forty-eight superconducting cavities grouped into six cryogenic modules and for one normal conducting rf gun. A WR650 waveguide distribution system distributes the power generated by five active rf stations using 5 MW single beam and a 10 MW multibeam klystron to the cavities and the gun. Since FLASH is based on the Tesla Test Facility, TTF, a number of different distribution layouts for the different modules and the gun have been developed and used over the years in terms of type of components and distribution scheme. This paper presents the layout and summarizes the experience with the existing waveguide distribution system. |
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THP080 | Elimination of Parasitic Oscillations in RF Tube Amplifier for High Power Application | linac, ion, simulation, controls | 981 |
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For the heavy ion therapy center HIT in Heidelberg a 1.6 MW power amplifier for 217 MHz was built to supply the 7 MeV/u IH cavity. The inherent parasitic oscillations of the RF tube increases rapidly the anode current until the system switches off. For the elimination of those parasitic oscillations ferrite material is used. The electro magnetic fields are simulated to find an optimal positioning of the ferrite material in the anode cavity such that only the parasitic oscillations are attenuated without affecting the fundamental mode. |
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THP086 | Cold Cathode Electron Tube Toward Plenty Multi Beam Tube | cathode, electron, high-voltage, simulation | 990 |
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The multi beam electron tube with a lot of beam pipes is required for the low applied voltage and the high frequency because the efficiency has a limit according to the perveance. However, the total heater power becomes too high if many thermal cathodes are used. Thus the cold cathode such as the carbon nano tube (CNT) is suitable for such a multi beam electron tube. Further the cold cathode has the advantage to work as a switching device since the metal grid close to the cathode can be used. The design and the fundamental test of the partial model will be presented. |
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THP087 | Quarter-Wave-Stub Resonant Coupler | linac, coupling, controls, rfq | 993 |
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Most small proton and other ion linacs involve two different linac structures, namely an RFQ linac section and some other, more efficient, linac structure, such as the Drift Tube Linac (DTL), the interdigital (Wideroe) linac, or the Rf Focused Interdigital (RFI) linac. Such linacs can benefit a lot by being resonantly coupled into a single resonant unit. The resonantly coupled structures can be driven by a single rf power system, through single rf drive loop, at a single rf frequency. The relative phase and relative amplitude of the fields in the two structures are locked by the resonant coupler. Such systems require no control of phase of the rf power. By designing the rf power system to track the resonant frequency of the combined structures, the control of the resonant frequencies of the two structures is greatly simplified. A simple, compact, resonant coupler, based on a quarter-wave-stub, will be described. Models of this resonant couple have been tuned and adjusted, and are scheduled to be tested at operating powers in the early fall (2008). |
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THP088 | High Power 325 MHz Vector Modulators for the Fermilab High Intensity Neutrino Source (HINS) | solenoid, linac, feedback, klystron | 996 |
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One of the goals of the low energy 60 MeV section of the Fermilab HINS H- linac is to demonstrate that a total of 40 rf cavities can be powered by a single 2.5 MW, 325 MHz klystron. This requires individual vector modulators at the input of each rf cavity to independently adjust the amplitude and phase of the rf input signal during the 3.5 ms rf pulse. Two versions of vector modulators have been developed; a 500 kW device for the RFQ and a 75 kW modulator for the remaining rf cavities. High power test results showing the vector modulator phase and amplitude responses will be presented. |
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THP089 | High Power L-Band Fast Phase Shifter | coupling, resonance, permanent-magnet, controls | 999 |
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Following development and testing a prototype waveguide-based high power phase shifter, a design concept of a high power fast phase shifter has been developed. The shifter uses ferrite blocks positioned in a rectangular waveguide. The waveguide cross-section is chosen to suppress most of resonances that could otherwise be a limiting factor for the phase shifter high power performance. Base bias field is created with the use of permanent magnets. Low inductance coils in the same magnetic circuit excite fast (pulsed) bias field component. The waveguide is designed in a way to ensure that the pulsed magnetic field penetrates inside the waveguide with minimum delay while allowing effective heat extraction from the ferrite blocks. This report provides details of the system design, including expected rf behavior and frequency range. |
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THP093 | Power Coupler and Tuner Development for Superconducting Quarter-Wave Resonators | vacuum, niobium, cryomodule, superconductivity | 1005 |
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The construction of a reaccelerator for secondary ion beams is currently underway at the National Superconducting Cyclotron Laboratory (NSCL). The reaccelerator linac will use superconducting quarter-wave resonators (QWR) operating at 80.5 MHz with beta = 0.041 and beta = 0.085. A coaxial probe-type rf fundamental power coupler (FPC) will be used for both QWR types. The power coupler makes use of a commercially-available feedthrough to minimize the cost. The FPC has been simulated and optimized for operation at 80.5 MHz using a finite element electromagnetics code. Prototype FPC have been fabricated and conditioned with traveling wave and standing wave power using a 1 kW amplifier. A niobium tuning plate is incorporated into the bottom flange of the QWR. The tuner is actuated by a stepping motor for slow (coarse) tuning and a stacked piezoelectric element in series for fast (fine) tuning. A prototype tuner for the beta = 0.041 QWR has been tested on the cavity at room temperature. This paper will cover the design, fabrication, and testing of the prototype coupler and tuner. |
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THP098 | RF Vector Control for Efficient Fan-Out Power Distribution | controls, impedance, linac, coupling | 1018 |
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Funding: This work was supported by SNS through UT-Battelle, LLC, under contract DE-AC05-00OR22725 for the U.S. DOE. |
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THP099 | Spallation Neutron Source Superconducting Linac Klystron to Cavity Mismatch Effects and Compensation | klystron, LLRF, linac, cathode | 1021 |
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Funding: Oak Ridge National Laboratory, P.O. Box 2008 Oak Ridge, Tennessee 37831-6285 managed by UT-BATTELLE, LLC for the U.S. Department of Energy Under Contract DE-AC05-00OR22725 |
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THP100 | Self Tuning Regulator for ISAC 2 Superconducting RF Cavity Tuner Control | controls, ISAC, alignment, feedback | 1024 |
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The ISAC 2 superconducting rf cavities use self-excited, phase-locked mode of operation. As such the microphonics are sensitive to the alignment of the phase control loop. Although initial alignments can minimize the effect of microphonics, long term drifts, particularly in the power amplifiers, can cause the control loop to misalign and an increase in sensitivity to microphonics. The ISAC 2 control system monitors several points in the control loop to determine the phase alignment of the power amplifiers as well as the rf resonant cavities. Online adaptive feedbacks using Self Tuning Regulators are employed to bring the different components back into alignment. |
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THP101 | AM-PM Conversion Induced Instability in I/Q Feedback Control Loop | booster, feedback, controls, TRIUMF | 1027 |
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Most rf feedback control systems today uses the I/Q demodulation and modulation scheme because of its simplicity. Its performance, however, depends on the alignment of the feedback loops. If the loop contains elements that have a high AM-PM conversion such as a class C amplifier, then the misalignment is dynamic and power dependent. In the extreme case the I/Q loops can become unstable and the system settled into a limit-cycle oscillation. |
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THP102 | Evaluation of Fast ADCs for Direct Sampling RF Field Detection for the European XFEL and ILC | monitoring, LLRF, feedback, linac | 1030 |
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For the LLRF system of superconducting linacs, precision measurements of the rf phase and amplitude are critical for the achievable field stability. In this paper, a fast ADC (ADS5474) has been evaluated for the measurement of a 1.3 GHz rf signal directly without frequency down conversion. The ADC clock frequency is synchronized with the rf frequency and chosen for non-IQ demodulation. In the laboratory, the Signal to Noise Ratio (SNR) of the ADC was studied for different clock and rf input levels, and the temperature sensitivity of the ADC has been determined. A full bandwidth phase jitter of 0.2 degree (RMS) and amplitude jitter of 0.32% (RMS) was measured. For field control of superconducting cavities with a closed loop bandwidth up to 100 KHz, one can expect to achieve a phase stability close to 0.01 degree. The main limitation will be the jitter of the external clock. We present a measurements at the cavities at FLASH and compare the result with the existing system. |
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THP103 | LLRF System Requirement Engineering for the European XFEL | LLRF, controls, diagnostics, klystron | 1033 |
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The LLRF system of the European XFEL must fulfill the requirements of various stakeholders: Photon beam users, accelerator operators, rf experts, controls system, beam diagnostics and many others. Besides stabilizing the accelerating fields the system must be easy to operate, to maintain, and to upgrade. Furthermore it must guarantee high availability and it must be well understood. The development, construction, commissioning and operation with an international team requires excellent documentation of the requirements, designs and acceptance test. For the rf control system of the XFEL the new system modeling language SySML has been chosen to facilitate the system engineering and to document the system. SysML uses 9 diagram types to describe the structure and behavior of the system. The hierarchy of the diagrams allows individual task managers to develop detailed subsystem descriptions in a consistent framework. We present the description of functional and non-functional requirements, the system design and the test cases. An attempt of costing the software effort based on the use case point analysis is also presented. |
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THP104 | Low Level RF and Timing System for XFEL/SPring-8 | controls, pick-up, feedback, low-level-rf | 1036 |
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Requirement on a Low Level rf (LLRF) system is very tight and allowable jitter is less than several tens femto seconds for the XFEL/SPring-8. To satisfy this requirement, we have developed special components; a low-noise master oscillator, a high precision IQ modulator/demodulator, a high speed DAC/ADC, and a delayed pulse generator with 700 fs jitter to a 5712 MHz reference clock. These components were installed in the SCSS test accelerator and their performance was checked. The standard deviations of the phase and amplitude were less than 0.02 degree and 0.03% for a 238 MHz SHB acceleration cavity. Measured rms jitter of the beam arrival time relative to the reference rf signal was 50 fs, which demonstrated the high performance of the total LLRF system. For the XFEL, the length of reference signal transmission line is long, about 1 km. Therefore an optical system is adopted because of low transmission loss and an ability to keep precise time accuracy using fiber length control, which has 0.2 um/sqrt(Hz) noise floor. Achieved performance of the LLRF and timing system, and development status on the optical transmission system will be presented in this paper. |
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THP105 | LLRF Control System of the J-PARC LINAC | linac, controls, feedback, beam-loading | 1039 |
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At the J-PARC 181 MeV proton linac, the rf sources consist of 4 solid-state amplifiers and 20 klystrons with operation frequency of 324 MHz. The rf fields of each rf source are controlled by a digital feedback system installed in a compact PCI (cPCI). A very good stability of the accelerating fields has been successfully achieved about ±0.2% in amplitude and ±0.2 degree in phase, much better than the requirements of ±1% in amplitude and ±1 degree in phase. Besides, the tuning of each accelerator cavity including 3 DTL and 15 SDTL is also controlled by this LLRF system through a cavity tuner. We pre-defined the cavity resonance states with the tuner adjusted to obtain a flat phase during the cavity field decay. The cavity auto-tuning is well controlled to keep the phase of rf fields within ±1 degree. Furthermore, from the amplitude waveform during the cavity field decay, the Q-value of each cavity is calculated in real-time and displayed in the PLC TP of the LLRF control system. |
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THP107 | Performance of Digital Low-Level RF Control System with Four Intermediate Frequencies | LLRF, controls, feedback, superconducting-cavity | 1045 |
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In a superconducting accelerator, an FPGA/DSP-based low-level rf (LLRF) system with feedback control is adopted to satisfy the requirement of stability in the accelerating field. An rf probe signal picked up from cavity is down-converted to an intermediate frequency and sampled by an analog-to-digital converter (ADC) in the digital LLRF control system. In order to decrease the number of the ADCs required for vector sum feedback operation, a digital LLRF control system using different intermediate frequencies has been developed. At STF (Superconducting RF Test Facility) in KEK, the digital LLRF system with four intermediate frequencies was operated and the rf field stability under the feedback operation was estimated using a superconducting cavity. The result of the performance will be reported. |
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THP108 | Performance of Digital LLRF System for STF in KEK | LLRF, feedback, controls, klystron | 1048 |
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RF operation has started at the STF (Superconducting RF Test Facility) in KEK. The digital feedback system, which consists of one FPGA, ten 16-bit ADCs and two 14-bit DACs, was installed in order to satisfy the rf-field regulation requirements of 0.3% rms and 0.3 deg.rms in phase. The rf field stability under various feedback parameters are presented. Various studies were also carried out such as cavity detuning measurements (microphonics, quench detection, etc.). These results will also be summarized. |
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THP109 | Measurements of Feedback-Instability Due to 8/9π and 7/9π Modes at KEK-STF | feedback, controls, klystron, LLRF | 1051 |
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In the superconducting rf test facility (STF) at KEK, high power tests of the nine-cell superconducting cavity for the international linear collider (ILC) have been performed. Although the cavity was operated in π-mode, the feedback instability due to 8/9π and 7/9π modes was observed in the STF. The intensities of 8/9π and 7/9π modes were measured by changing the feedback loop-delay and stable/unstable region appeared periodically as expected. |
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THP110 | Pulse-by-Pulse Switching of Beam Loading Compensation in J-PARC Linac RF Control | controls, linac, beam-loading, LLRF | 1054 |
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For the J-PARC linac low level rf system, in order to compensate beam-loading change by pulses in the operation of 25 Hz repetition, a function that switches the feed-forward control parameters in every pulse were installed into the digital accelerating-field control system. The linac provides a 50 mA peak current proton beam to a 3 GeV rapid-cycling synchrotron (RCS). Then the RCS distributes the 3-GeV beam into a following 50 GeV synchrotron (main ring, MR) and the Materials and Life Science Facility (MLF), which is one of the experimental facilities in the J-PARC. The 500-us long macro pulses from the ion source of the linac should be chopped into medium pulses for injection into the RCS. The duty (width or repetition) of the medium pulse depends on which facility the RCS provides the beam to the MR or MLF. Therefore the beam loading compensation needs to be corrected for the change of the medium pulse duty in the 25 Hz operation. |
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THP111 | LLRF Control System Using a Commercial Board | controls, LLRF, feedback, DTL | 1057 |
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The requirements for the field amplitude and phase stability of the PEFP linac are 1% and 1 degree, respectively. To achieve the requirements, a digital LLRF control system has been developed using a commercial digital board for general purpose(FPGA). The feedback with PI control and feedforward are implemented in the FPGA. The LLRF control systems are currently used for the linac test. In this paper, test results and discussion on the advantage and disadvantage of the LLRF system based on a commercial board are presented. |
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THP112 | Numerical Simulation of the INR DTL A/P Control System | controls, feedback, DTL, vacuum | 1060 |
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Stabilization of amplitude and phase in linear accelerator cavities can be realized by means of control systems, operating both in polar (A/P) and rectangular (I/Q) coordinates. In analyzing of linear control systems, as a rule, transfer functions are used, which, in turn, are the symbolic representation of the linear differential equation, connecting the input and output variables. It's well known that generally in A/P coordinate it is impossible to get two separate linear differential equations for amplitude and phase of rf voltage in a cavity except for estimating of the control system stability in the small near steady state values of variables. Nevertheless, there is a possibility of numerical simulation of nonlinear A/P control system using up-to-date programs. Some results of the simulation are presented. |
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THP113 | Optimal Coupler and Power Settings for Superconductive Linear Accelerators | beam-loading, klystron, superconducting-cavity, LLRF | 1063 |
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Funding: FRA C. Nantista, K.L.F. Bane, C. Adolphsen, RF Distribution Optimization in |
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THP114 | New LLRF System for Fermilab 201.25 MHz Linac | LLRF, controls, linac, feedback | 1066 |
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The Fermilab Proton Plan, tasked to increase the intensity and reliability of the Proton Source, has identified the Low Level RF (LLRF) system as the critical component to be upgraded in the Linac. The current 201.25 MHz Drift Tube Linac LLRF system was designed and built over 35 years ago and does not meet the higher beam quality requirements under the new Proton Plan. A new VXI based LLRF system has been designed to improve cavity vector regulation and reduce beam losses. The upgrade includes an adaptive feedforward system for beam loading compensation, a new phase feedback system, and a digital phase comparator for cavity tuning. The new LLRF system is phase locked to a temperature stabilized 805 MHz reference line, currently used as frequency standard in the higher energy accelerating section of the Linac. This paper will address the current status of the project, present the advancements in both amplitude and phase stability over the old LLRF system, and discuss commissioning plans. |
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THP115 | Optimizing Cavity Gradients in Pulsed Linacs Using the Cavity Transient Response | linac, controls, beam-loading, klystron | 1069 |
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Pulsed Linac accelerators are being designed powering a string of cavities from one klystron. A typical low level rf control loop controls the amplitude and the phase of the klystron's rf power; however, the loop cannot dynamically control individual cavity amplitude and phases. The problem is further complicated by the need to obtain the maximum possible acceleration from the rf unit. Proton Linacs (HINS, ProjectX) add extra complexity. A rf unit may need cavities operating at different synchronous phases. Particles travel cavities at increasing velocities, which implies different beam loading conditions. For pulsed proton Linacs amplitude and phase stability are crucial for beam stability. The usual steady state approach determines optimality conditions for minimum generator power as a function of rf parameters. This approach does not provide constant amplitude and phases when the beam is on. In this paper we propose a novel theory using the cavity transient response. The transient response allows setting flat cavity gradients (A and phi) for each cavity in the unit. The optimized rf parameters for the transient response are the cavity coupling parameter and cavity tuning angle. |
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THP116 | Real Time RF Simulator (RTS) and Control | controls, LLRF, beam-loading, simulation | 1072 |
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A multi cavity real time rf simulator and PID control has been implemented on a Xilinx Virtex-4 FPGA. The rf simulator simulates an entire rf unit with up to 4 cavities connected to a single simulated klystron. Each cavity is allowed to have its own set of parameters, set point gradients, synchronous phases, and beam loadings. The simulator is built based on an interdependent electrical and mechanical model of a cavity. The electrical model is a 1st order differential equation in the complex phase space. The mechanical model is a 2nd order differential equation of the Lorentz force detuning on the cavities. Other spurious effects as microphonics and noises can be added using an external source or a memory table. The simulator has been optimized for size and utilizes only one Xilinx DSP block per cavity. A typical Virtex-4 has of the order of 100 DSP blocks. The simulator bandwidth is 1MHz which is plenty for niobium type superconducting cavities which have a loaded Q of about 3 million and a half bandwidth of about 250 Hz. The Real Time simulator is currently running on hardware comprised by an ESECON LLRF controller* and a Linux based VME processor. *ESECON, 14 channel LLRF controller, Low Level Radio Frequency Workshop (LLRF07), Knoxville, Tennessee, October 22-25, 2007, presentation 031. |
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THP117 | Design and Evaluation of the Low-Level RF Electronics for the ILC Main LINAC | LLRF, linac, low-level-rf, controls | 1075 |
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Funding: Work supported by Fermi Research Alliance LLC. Under DE-AC02- 07CH11359 with the U.S. DOE |
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THP118 | A Femtosecond-Level Fiber-Optics Timing Distribution System Using Frequency-Offset Interferometry | laser, klystron, controls, feedback | 1078 |
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Funding: This work was supported by the Office of Science, U. S. Department of Energy, under Contract No. DE-AC02-05CH11231. |
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THP120 | Concept Design Studies of the REX-ISOLDE Cryomodules at CERN | vacuum, cryomodule, linac, solenoid | 1081 |
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The High Intensity and Energy (HIE) proposal plans a major upgrade of the existing ISOLDE and REX-ISOLDE facilities at CERN, with the objective of substantially increasing the energy and the intensity of the delivered radioactive ion beams. In the frame of this upgrade activity, a superconducting linac, based on Nb sputtered Quarter Wave Resonators (QWRs) is proposed to be installed downstream of the present normal conducting machine. The present design of the accelerator lattice features housing of five high-beta cavities (β=10.6%) and a superconducting solenoid in a common cryomodule. In most of the existing low-energy heavy-ion installations worldwide, insulation and beam vacuum are in common, with the risk of cavity surface contamination in case of accidental leak to the cryostat vessel. Following a concept study, we report in this paper on three design options, namely cryomodules with common vacuum, with separate or with hybrid vacuum systems (the latter having a low conductance between insulation and beam vacuum) and compare them in terms of technical complexity, performance, reliability and maintainability. |
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THP122 | Overview of the First Five Refurbished CEBAF Cryomodules | cryomodule, vacuum, electron, linac | 1084 |
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Funding: Authored by JSA, LLC under U.S. DOE Contract No. DE-AC05-06OR23177 |
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FR101 | 8-GeV C-Band Accelerator Construction for XFEL/SPring-8 | klystron, high-voltage, FEL, electron | 1090 |
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The 8 GeV C-band electron linear accelerator is under construction at the SPring-8 site aiming at generating an FEL X-ray beam in 2010. C-band accelerator technology has been developed initially at KEK for the e+e- linear collider project, and employed at the XFEL project in Japan. Since C-band generates a high gradient acceleration field as high as 35 MV/m, the total length of the accelerator fits within 400 m, including the injector and three bunch compressors. C-band uses normal conducting rf technology, thus it runs in pulse mode at 60 Hz, which is well suited to XFEL operation and is less expensive. The talk will cover the current status of the XFEL project and hardware production. |
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FR202 | Linacs for Future Muon Facilities | linac, optics, focusing, acceleration | 1119 |
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Funding: Supported in part by DOE STTR grant DE-FG02-05ER86253 |
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