| Paper | Title | Other Keywords | Page | ||
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| MOP008 | Design and Performance of Optics for Multi-Energy Injector Linac | injection, optics, electron, linac | 46 | ||
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Injector linac provides injection beams for four storage rings, KEKB high energy electron ring (HER), KEKB low energy positron ring (LER), PF-AR electron ring, and PF electron ring. The injection beams for these rings have different energies and intensities. Recently, a requirement of simultaneous injection among these rings arises to make a top-up injection possible. Magnetic fields of DC magnets to confine the beam to the accelerating structures can not be changed between pulse to pulse, although the beam energy can be controlled by fast rf phase shifters of klystrons. This implies that common magnetic fields of bending magnets and quadrupole magnets should be utilized to deliver beams having different characteristics. Therefore, we have designed multi-energy optics for KEKB high energy electron ring (8 GeV, 1 nC/pulse) and PF electron ring (2.5 GeV, 0.1 nC/pulse) and present a performance of the multi-energy injector linac.
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| MOP017 | 4GLS Beam-Break-Up Investigations | focusing, linac, recirculation, simulation | 67 | ||
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Beam Break Up (BBU) thresholds have been studied as part of the Linac focusing scheme for the proposed 4GLS accelerator. A graded gradient focusing scheme, with a triplet of quadrupoles between each of the modules within the Linac has been chosen. These quadrupoles are set-up in a defocusing – focusing – defocusing format with strengths of -1/2k, k, -1/2k. This value of k was altered and the BBU thresholds for the machine calculated using various BBU codes. Alternate cavity designs have also been investigated using CST’s Microwave Studio to see how the effects of higher order modes (HOMs) can be minimised whilst maintaining fundamental field flatness across theaccelerating cells. The number of cells/unit length and cell-to-cell geometries have also been parameterised and the corresponding BBU thresholds presented as a function of cavity geometry, with the intention of providing an optimum solution for 4GLS.
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| MOP023 | Beam-Based Optics Correction for New Beam Transport Line from LINAC to Photon Factory in KEK | linac, optics, luminosity, beam-transport | 85 | ||
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The e+/e- injector LINAC in KEK usually injects into four rings which are Low Energy Ring(LER) of KEKB(3.5GeV/e+), High Energy Ring (HER) of KEKB(8.0GeV/e-), Photon Factory(PF)(2.5GeV/e-) and Advanced Ring for pulse X-rays(PF-AR)(3.0GeV/e-). While LINAC continuously injects into LER and HER alternatively every about five minutes, both of KEKB rings usually storage almost full operating currents. Time for PF or PF-AR which includes switching time had taken about 20 minutes a several times in a day. This had made luminosity at KEKB lower. In summer of 2005, a part of transport line from LINAC to PF were renewed, in which a DC bending magnet only for PF apportions electron beam from the end of LINAC to the new line. We succeeded to reduce the occupancy time for PF injection to about five minutes and there is almost no affection to KEKB luminosity. In this paper optics of the new PF beam transport line is described. In practical performance there had been leakage magnetic field from ECS magnets in KEKB(e+) beam transport line neighboring the PF line. Furthermore we measured the horizontal dispersions along the line. We describe about the magnetic shielding and the optics correction.
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| MOP035 | Operational Aspects of High-Power Energy-Recovery Linacs | wiggler, linac, vacuum, lattice | 115 | ||
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We have been operating a high power energy recovery linac (ERL) at Jefferson Lab for several years. In the process we have learned quite a bit about both technical and physics limitations in high power ERLs. Several groups are now considering new ERLs that greatly increase either the energy, the current or both. We will present some of our findings on what to consider when designing, building, and operating a high power ERL. These include space charge effects, halo, magnetic field quality, RF stability, short bunch formation, coherent synchrotron radiation and it effect on the beam, beam breakup instabilities, higher order mode production, and diagnostic requirements.
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| MOP040 | Design of the PEFP 100-MeV Linac | proton, linac, rfq, klystron | 130 | ||
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The Proton Engineering Frontier Project (PEFP) is constructing a 100 MeV proton linac in order to provide 20 MeV and 100 MeV proton beams. The linac consists of a 50 keV proton injector, a 3 MeV radio-frequency quadrupole (RFQ), a 20 MeV drift tube linac (DTL), a medium energy beam transport (MEBT), and the higher energy part (20 MeV ~ 100 MeV) of the 100 MeV DTL. The MEBT is located after the 20 MeV DTL in order to extract 20 MeV proton beams as well as to match the proton beam into the higher energy part of the linac. The 20 MeV part of the linac was completed and is now under beam test. The higher energy part of the PEFP linac was designed to operate with 8% beam duty and is now under construction. This brief report discusses the design of the PEFP 100MeV linac as well as the MEBT.
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| MOP053 | Construction of a High-Current RFQ for ADS Study | rfq, dipole, vacuum, coupling | 165 | ||
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A high current RFQ accelerator has been constructed in China for the basic study of Accelerator Driven Subcritical System. The ADS project is supported by a national program and aimed at the development of clean nuclear energy to meet of the rapid growth of the nuclear power plants in China. The 3.5MeV RFQ accelerator has been fabricated and installed. Field tuning and high power conditioning indicate a good agreement with our design. The beam commissioning with an ECR ion source is under development. This paper will present the recent progress in the construction and commissioning of the RFQ accelerator.
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| MOP055 | Transport of LANSCE-Linac Beam to Proposed Materials Test Station | target, diagnostics, emittance, dipole | 171 | ||
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Refurbishment of Experimental Area A and installation of a Materials Test Station is planned at the Los Alamos Neutron Science Center (LANSCE). This paper describes the beamline to transport 800-MeV protons from the accelerator to Area A. The beamline has the minimum number of quadrupoles necessary to achieve the desired instantaneous beam parameters at the target, the appropriate beam-centroid excursions at the split target for painting the two target halves, and a beam-centroid crossover upstream of the target to facilitate shielding of upstream components from backstreaming neutrons. Options in the composition of the raster-magnet section represent trade-offs between the number of magnets and the severity of the effects of magnet failures. Beam diagnostics are an integral part of the beamline design. Instantaneous and painted beam sizes at the target can be inferred by observing the beam at properly chosen upstream locations. A beamline spur to a tune-up beam dump is planned.
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| MOP064 | Emittance Preservation for the Curved ILC Main Linac | linac, emittance, coupling, alignment | 192 | ||
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It is envisaged in Baseline Configuraation Document that the main linear accelerator of ILC will follow the earth curvature instead of being laser-straight. Beam based alignments will be imperative for preserving the small vertical beam emittances through the main linac. Various beam based algorithms have been developed during the last decade. However, most of the simulation studies assumed the straight geometry of the linac. In this work we present the results on single bunch emittance dilution in the curve ILC main linac, using Dispersion Free Steering under the nominal misalignment of the beam line components. We present the comparison of the curve linac with laser stright geometry. We have studied the sensitivity of the DFS to the various misalignments and also considered the effect of incoming beam jitter and quadrupole vibration jitter. Further, robustness of DFS to the failure of corrector magnets or BPM is investigated. The beneficial effect of the dispersion bumps on the emittance dilution performance is also discussed.
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| TUP005 | Design of an RFQ-Based Neutron Source for Cargo Container Interrogation | rfq, target, ion-source, ion | 253 | ||
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An RFQ-based neutron generator system is described that generates pulsed neutrons for the active screening of sea-land cargo containers for the detection of shielded special nuclear materials (SNM). A microwave-driven deuteron source is coupled to an electrostatic LEBT that injects a 40 mA D+-beam into a 6 MeV, 5.1 meter-long 200 MHz RFQ. The RFQ has a unique beam dynamics design and is capable of operating at duty factors of 5 to10% accelerating a D+ time-averaged current of up to 1.5 mA at 5% duty factor, including species and transmission loss. The beam is transported through a specially-designed thin-window into a 2-atmosphere deuterium gas target. A high-frequency dipole magnet is used to scan the beam over the long dimension of the 5 by 40 cm target window. The source will be capable of delivering a neutron flux of 2·107 n/(cm2·s) to the center of a cargo container. Details of the ion source, LEBT, RFQ beam dynamics and gas target design are presented.
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| TUP023 | Beam-Size Measurements in the IPNS 50-MeV Transport Line Using Stripline BPMs | linac, diagnostics, controls, monitoring | 296 | ||
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Continuing with the work started two years ago, the technique of using a two-beamlet model to measure beam size is presented. Beam signals are detected on terminated 50-ohm, stripline BPMs located in the transport line between the 50 MeV linac and rapid cycling synchrotron. Each BPM is constructed with four striplines: top, bottom, left and right. Using a fast-sampling oscilloscope to compare the signals from opposite strip lines allows one to determine beam size assuming a two beamlet model. Measurements made with the two-beamlet approach are compared with other standard profile diagnostics such as wire-scanners, segmented Faraday cups, and scintillators. Advantages of the two-beamlet method are that it is non intrusive and does not require the presence of a background gas necessary for an IPM. Disadvantages of the technique are that it does not provide a detailed profile and the longitudinal beam pulse length must be short relative to the stripline length.
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| TUP059 | Photoinjector Production of a Flat Beam with Transverse Emittance Ratio of 100 | emittance, simulation, laser, electron | 382 | ||
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The generation of a flat electron beam directly from a photoinjector is an attractive alternative to the electron damping ring as envisioned for linear colliders. It also has potential applications to light sources such as the generation of ultrashort x-ray pulses or Smith-Purcell free electron lasers. In this paper, we report on the experimental generation of a flat beam with a measured transverse emittance ratio of 100±20 for a bunch charge of ≅0.5~nC*. The experimental data, obtained at the Fermilab/NICADD Photoinjector Laboratory, are compared with numerical simulations and the expected scaling laws. Possible improvement of the experiment along with application for such a flat beams are discussed
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* P. Piot, Y.-E. Sun and K.-J. Kim, Phys. Rev. ST Accel. Beams 9, 031001 (2006) |
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| TUP077 | Transverse Beam Matching and Correction Procedures in INR Linac | linac, controls, simulation, focusing | 435 | ||
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An interactive procedure for the transverse beam matching and correction has been developed and implemented in several areas of INR Linac. The profile measurements are used for determination of the main transverse beam parameters. These data are applied for calculation the dipole correction currents and quadrupole gradients to transport the beam with minimum sizes and off axis displacements. The user friendly interface and graphics support has been developed for data treatment and beam behavior presentation. The proposed algorithm of beam matching, beam steering and data treatment is discussed. Some experimental and simulation results for different INR Linac operation modes are presented.
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| TH1004 | A 70-MeV Proton Linac for the FAIR Facility Based on CH - Cavities | linac, coupling, proton, rfq | 526 | ||
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Future Accelerators for fundamental and for applied research will need a significant improvement in injector capabilities. This paper will describe the concept and the status of the 70 MeV, 70 mA proton injector for GSI - FAIR and compare the CH - linac design with traditional DTL concepts. Improvements in the space charge routine of the LORASR code as well as CH - prototype cavity development and cavity grouping with respect to commercial 3 MW rf power amplifiers is reported. Additionally, the potential of robust superconducting low and medium energy high current linac sections will be explained on the basis of experimental results from a first 19 cell s.c. 350 MHz CH - prototype cavity.
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| THP008 | Detailed Modeling of the SNS RFQ Structure with CST Microwave Studio | rfq, simulation, SNS, dipole | 580 | ||
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We report detailed RF modeling on the SNS RFQ structure using CST Microwave Studio code. Due to the complexity of the RFQ structure, a three-dimensional model with large mesh ratio is required to adequately model the necessary details of the structure. Old 3-D codes are not capable of giving accurate predictions of resonant frequency and fields, or for including mode stabilizers and terminations. A physical prototype is needed to verify resonant frequency and field profile, including mode stabilizers and end terminations, which is expensive and time consuming. Taking advantage of CST Microwave Studio’s new Perfect Boundary Approximation (PBA) technique, we constructed a 3-dimensional computational model based on the as-built SNS RFQ dimensions with pi-mode stabilizers, end cutbacks and tuners and simulated it in the frequency domain using the CST Eigenvalue Solver. Simulation results accurately predicted the resonant frequency and field distributions. We are applying the simulation technique to the design of another RFQ.
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| THP017 | Magnet Hysteresis Control at LANSCE | power-supply, linac, controls, acceleration | 601 | ||
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We have investigated the effects of magnet hysteresis in various beamlines at LANSCE (Los Alamos Neutron Science Center) and have developed procedures to control the effects. Particular challenges are presented by sets of magnets with parallel boosting and bucking windings on the same yoke powered by two families of supplies and by magnets whose fields are routinely reversed for different operating modes. The results of the procedures are more rapid recovery from power-off conditions and rapid switching between operating modes, with minimized re-tuning. The latter improvement has been beneficial in controlling a beam instability that has adverse effects on the users’ experiments.
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| THP018 | Design Progress of the Re-bunching RF Cavities and Hybrid Quadrupoles for the RAL Front-End Test Stand (FETS) | linac, impedance, simulation, proton | 604 | ||
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The proposed FETS project at RAL will test a fast beam chopper in a 3.0 MeV H- Medium Energy Beam Transport (MEBT) line. Space restrictions in the MEBT line place constraints on component length and drive the requirement to identify compact component configurations. Two candidate re-bunching RF cavity designs are considered: the space efficient Drift Tube Linac type (DTL) with integrated quadrupoles, and the high shunt impedance Coupled Cavity Linac type (CCL) with external quadrupoles. Preliminary RF simulations in 2D and 3D are presented, and a comparison, emphasising the advantages and disadvantages of each design is made. The compact hybrid quadrupole configurations considered are the 'tandem' combination of permanent magnet (PMQ) and electro-magnetic (EMQ) types, and the concentric combination of PMQ and laminar conductor (Lambertson) EMQ types. The suitability of the compact hybrid quadrupole for implementation in the low energy Drift Tube Linac (DTL) is suggested and discussed.
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| THP032 | A Variable Directional Coupler for an Alternate ILC High-Power RF Distribution Scheme | coupling, polarization, klystron, linac | 643 | ||
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We describe the design and functionality of an RF directional coupler for which the power division between the output ports is mechanically variable. In an alternate power distribution scheme for the ILC, power is delivered to cavities in pairs, through hybrids. Four pairs, or eight cavities, are fed from one waveguide feed, from which one fourth, one third, and one half of the power is coupled out at consecutive directional couplers. Three such feeds are powered by a single 10 MW klystron. Experience suggests that cavities considered useable will display some variation in the operational accelerating gradient they can sustain. With fixed distribution, the klystron power must be kept below the level at which the weakest cavity out of 24 receives its power limit. This problem can be solved by installing variable attenuators, but that means wasting precious power. With adjustable coupling, distribution can be optimized for more efficient use both of available power and of the accelerating cavities. This novel device, feeding cavities paired by similar performance, can provide such benefit to the ILC.
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| THP044 | Design and Development of RF Structures for Linac4 | linac, klystron, coupling, booster | 679 | ||
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Linac4 is a new 160 MeV H- linac proposed at CERN to replace the 50 MeV Linac2 as injector to the PS Booster, with the goal of doubling its brightness and intensity. The present design foresees after RFQ and chopping line a sequence of three accelerating structures: a Drift Tube Linac (DTL) from 3 to 40 MeV, a Cell-Coupled DTL (CCDTL) to 90 MeV and a Side Coupled Linac (SCL) up to the final energy. The DTL and CCDTL operate at 352 MHz, while in the SCL the frequency is doubled to 704 MHz. Although the injection in the PS Booster requires only a low duty cycle, the accelerating structures are designed to operate at the high duty cycle required by a possible future extension to a high power linac driver for a neutrino facility. This paper presents the different accelerating structures, underlining the progress in the design of critical resonator elements, like post-couplers in the DTL, coupling slots in the CCDTL and bridge couplers for the SCL. Alternative structures to the SCL are analysed and compared. Prototyping progress for the different structures is reported, including the RF design of a DTL tank prototype and results of low and high power tests on a CCDTL prototype.
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| THP048 | Band Gap Structures of PBG and Rod-loaded Cavities | dipole, damping, lattice, klystron | 688 | ||
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The band-gap structures for rod loaded (RL) and photonic band gap (PBG) cavities are calculated with 2D and 3D frequency domain codes. It is shown that an RL cavity with a single circle of rods can exhibit similar behavior as a conventional single-defect PBG cavity. A systematic method of computing the unloaded Q factor using SUPERFISH has been implemented. Results are compared with GdfidL and Gd1 calculations.
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| THP069 | DTL and SDTL Installation for the J-PARC | alignment, linac, proton, synchrotron | 743 | ||
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Three DTL tanks and 30 SDTL tanks have been installed precisely in the under-ground tunnel of the J-PARC project. The alignment of the tank was mainly done by using an alignment telescope. The distance of the center axis of the tank from the beam axis was measured by the telescope of which axis is in the beam line. The distance is minimized by adjusting the position of the tank on the stand. The beam axis in the tank is defined by the two optical target which are put on the template fixed on both ends of the tank cylinder for the DTL. After the installation of the tanks the movable tuners and the input couplers were also fixed on the tank. In the paper the measured tank position will be described in detail.
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| THP070 | Study of BSNS RFQ Design | rfq, coupling, simulation, dipole | 746 | ||
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A new 324MHz RFQ used for the project of Beijing Spallation Neutron Source (BSNS) is being designed. The designed injection and output energy are 50keV, 3.0MeV, respectively. The designed pulsed current is 40mA though the required current of BSNS at its first stage is only 20mA. The pulsed width is 420 s with a 50% chopping ratio and repetition rate is 25Hz. The transverse structure of BSNS RFQ will be basically the same as the former RFQ used for ADS, but the length of 3.62m is shorter comparing to the length of 4.75m of the former. The beam dynamics design and the RF structure design of the RFQ will be presented in this paper.
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