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| MOP045 | Performance of SNS Front End and Warm Linac | linac, SNS, emittance, focusing | 145 | ||
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The Spallation Neutron Source accelerator systems will deliver a 1.0 GeV, 1.4 MW proton beam to a liquid mercury target for neutron scattering research. The accelerator complex consists of an H- injector, capable of producing one-ms-long pulses at 60Hz repetition rate with 38 mA peak current, a 1 GeV linear accelerator, an accumulator ring and associated transport lines. The 2.5MeV beam from the Front End is accelerated to 86 MeV in the Drift Tube Linac, then to 185 MeV in a Coupled-Cavity Linac and finally to 1 GeV in the Superconducting Linac. With the completion of beam commissioning, the accelerator complex began operation in June 2006. Injector and warm linac performance results will be presented including transverse emittance evolution along the linac, longitudinal bunch profile measurements at the beginning and end of the linac, and the results of a beam loss study.
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| MOP068 | Beam-Loss Measurement and Simulation of Low-Energy SNS Linac | linac, SNS, simulation, radiation | 202 | ||
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We have installed a number of Neutron detectors from the MEBT to the end of CCL [186 MeV]. These detectors are made in collaboration with INR. In this paper we present our implementation and simulation of the losses by inserting Faraday Cups at different energies. We also calibrated neutron detectors and their high voltage dependence. The measured losses are simulated by 3-D transport codes during SCL commissioning. We also discuss future improvements such as interpreting the loss signal in terms of beam current lost in warm part of SNS linac with accurate longitudinal loss distribution as well as plan to automate voltage dependence of the neutron detectors. We compare two different sets of Beam Loss Monitors: Ionization Chambers (detecting X-ray and gamma radiation) and Photo-Multiplier Tubes with a neutron converter (detecting neutrons). We outline such combination is better way to deal with the beam losses than relying on detectors of one type.
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| TU2004 | Results on the Beam Commissioning of the Superconducting-RFQ of the New LNL Injector | rfq, emittance, simulation, ion | 227 | ||
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A new injector for the heavy ion superconducting linac ALPI has been built at LNL. This new accelerator, named PIAVE, is designed to accelerate ions with A/Q=<8.5 up to 1.2 MeV/u. The main components are an ECRIS source operating on a high voltage platform, a three harmonic buncher, a superconducting RFQ cryomodule containing two bulk niobium structures and two QWR cryomodules housing 4 cavities each. In the last year the injector has been commissioned, with O, Ar, Ne and Xe beams, and put into operation. The beam performances, and the results of longitudinal and transverse emittance measurements will be shown and compared with simulations. Neon and argon beams have been delivered to the experiments (after acceleration with PIAVE and ALPI) for a total of about 400 hours. It should be noted that this is the first superconducting RFQ in operation; the design opportunities offered by this technology for a wider field of applications will be briefly discussed. The heart of these opportunity is given by the high intervane voltage in a cw RFQ (PIAVE can operate cw with an intervane voltage higher than 250 kV).
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| TUP009 | First Operation of the FLASH Machine Protection System with Long Bunch Trains | undulator, linac, radiation, laser | 262 | ||
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The linac-based free electron laser facility FLASH at DESY Hamburg is designed to transport an electron beam with an average power of more than 50 kW. To avoid serious damage to accelerator components, a fast active machine protection system (MPS) stops the production of new bunches if hazardous machine conditions are detected. This paper gives an overview of the MPS topology and its subsystems. Furthermore, we present results from the commissioning of the fast beam interlock system that has for the first time allowed to operate the accelerator with macropulses of up to 600 bunches.
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| TUP020 | The J-PARC L3BT Monitor System for RCS Injection | injection, linac, electron, pick-up | 290 | ||
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The J-PARC linac-3GeV rapid cycling synchrotron (RCS) beam transport line (L3BT) monitor system will be used to tune the intensity of 5mA-50mA linac beam. The monitor system is composed of BPMs and multi wire profile scanners (MWPS) in L3BT line and RCS injection area. A non-destructive beam momentum spread monitor using a 4-stripline pickups is also developed in order to measure and control the momentum spread of linac beams. The spatial resolution of less than 0.3mm and momentum spread of less than 0.1% is required for RCS injection to avoid uncontrolled beam losses. In this paper, beam position monitor, profile monitor and momentum spread measurement for J-PARC linac is described. Preliminary results of beam size and m value measurement with quadrupole mode of the signal of 4-stripline BPMs in the KEK MEBT1 are also discussed.
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| TUP068 | Tuning Strategy for Transverse Collimator in J-PARC L3BT | collimation, monitoring, linac, injection | 409 | ||
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We plan to start beam commissioning of J-PARC linac and the succeeding beam transport line in December 2006. The beam transport line, to which we refer as L3BT, has two key functionalities to satisfy the requirements for the succeeding ring injection. One is to reduce the momentum jitter and momentum spread, and the other is to scrape off the transverse tail. To realize the latter functionality, a transverse collimator system is installed in L3BT which consists of four horizontal and four vertical collimators. In this presentation, the tuning strategy for the transverse collimator system is presented together with the main features of the collimator system.
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| TUP072 | Beam Dynamics Studies of the 8-GeV Superconducting H- Linac | linac, simulation, focusing, rfq | 420 | ||
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A 8-GeV H-minus linac has been proposed to enhance the accelerator complex at Fermilab as a high-intensity neutrino source.* The linac is based on 430 independently phased superconducting cavities. The front-end of the linac (up to 420 MeV) operating at 325 MHz is based on RIA-type multi-spoke cavities. The rest of the linac (from 420 MeV to 8 GeV) uses ILC-type elliptical cavities. We have performed large scale end-to-end beam dynamics simulations of the driver linac using the code TRACK** including all sources of machine errors and detailed beam loss analysis. The results of these simulations will be presented and discussed.
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* G. W. Foster and J. A. MacLachlan, Proceedings of LINAC-2002, p.826. |
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| TUP073 | Simulations of RF Errors in the SNS Superconducting Linac | linac, simulation, emittance, SNS | 423 | ||
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Minimizing beam emittance growth in the SNS superconducting linac due to RF errors, either correlated or uncorrelated, is essential since it can lead to beam loss in the linac and in the downstream ring. From multi-particle simulation studies of both matched and mismatched linac lattices, for the design peak beam current of 38 mA, as well as a typical commissioning beam current of 20 mA, we conclude that the linac may tolerate much higher non-correlated RF errors, especially in the second half of the superconducting linac, where errors in synchronous phase up to 10 degrees and that of cavity field amplitude up to 10% is acceptable. However, tolerance to correlated RF errors in the linac is within only 0.5 degree and 0.5 %, from simulations using a simple longitudinal linac model. Beam parameter measurement results acquired during linac beam commissioning confirmed the simulations.
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| TUP075 | Automatic Transverse and Longitudinal Tuning of Single and Multiple Charge State Ion Beams | linac, focusing, emittance, simulation | 429 | ||
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Extensive end-to-end beam dynamics simulations of the RIA driver linac using the code TRACK and including all sources of machine errors and detailed beam loss analysis* showed that the losses could be significantly reduced for a fine-tuned linac. For this purpose we have developed an automatic longitudinal tuning proceedure for multiple charge state heavy-ion beams.** For a complete tuning tool, we have recently developed an automatic transverse tuning proceedure to produce smooth transverse beam dynamics by minimizing the RMS beam sizes after each focusing period. We have also extended the automatic longitudinal proceedure to produce smooth longitudinal beam dynamics for single and multiple charge state ion beams. In addition to improving an existing tune, this powerful automatic beam tuning tool can be used to retune the linac and restore the beam after one or more elements failures and to develop new tunes for ion beams with different Q/A ratios. After presenting the method, the results from some applications will be presented and discussed.
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* P. Ostroumov, V. Assev and B. Mustapha, Phys. Rev. ST-AB 7 (2004) 090101 |
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| TUP079 | RIAPMTQ/IMPACT: Beam-Dynamics Simulation Tool for RIA | linac, simulation, emittance, rfq | 441 | ||
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We describe a multiple-charge-state simulation-code package for end-to-end computer simulations of the RIA heavy-ion driver linac, extending from the low-energy beam transport after the ECR source to the end of the linac. The work is being performed by a collaboration including LANL, LBNL, ANL, and MSU. The package consists of two codes, the code RIAPMTQ for the linac front end including the LEBT, RFQ, and MEBT, and the code IMPACT for the superconducting linac. This code package has been benchmarked for rms beam properties against previously existing codes at ANL and MSU. The simulation tool will allow high-statistics runs on parallel supercomputing platforms, such as NERSC, as well as runs on desktop PC computers for low-statistics design work. It will address an important near-term need for the RIA project, allowing evaluations of candidate designs with respect to beam-dynamics performance including beam losses, which can be compared with predictions of other existing simulation codes.
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| TUP085 | Beam Simulations for the MSU-RIA Driver Linac Using IMPACT Code | linac, simulation, emittance, ion | 457 | ||
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Previous end-to-end three-dimensional (3D) beam dynamics simulation studies at Michigan State University (MSU) utilizing the LANA code and including experimentally-based ion source beam parameters, alignment and rf errors, and the effect of charge-stripping foils have indicated that the MSU Rare Isotope Accelerator (RIA) driver linac has adequate transverse and longitudinal acceptances to accelerate light and heavy ions to final energies of ≥ 400 MeV/u with beam powers of 100 to 400 kW. Recently, to evaluate beam dynamics performance under various error scenarios with high statistics, the end-to-end 3D beam dynamics simulation studies for the driver linac were performed on the high performance parallel computers at MSU using the parallel code IMPACT that is an element of the advanced beam dynamics simulation tool: RIAPMTQ/IMPACT. The results of these beam dynamics studies will be presented.
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| THP035 | Design on Accelerating Tube of High-Power Electron Linac for Irradiation Processing | electron, linac, bunching, simulation | 652 | ||
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There is an unstable phenomenon for high-power electron linacs for irradiation processing. The main source of the instability of this type of linac comes from the thermal effect of the accelerator tube under an intense heat load. If a lot of injected electrons are lost in the tube, they can cause an intense and uneven heat load on the tube that may deform the cavities of the accelerator tube and deviate the correct acceleration phase relationship. In this paper, a constant gradient accelerating structure is chosen to accelerate the electron beam, and the designed phase velocity is gradually increased along the tube. By adjusting the size of the accelerating cavities and the phase velocity function, a high capture-efficiency is reached. After a series of simulations studies, we obtained a 90% capture-efficiency, which minimizes the probability of the unstable phenomenon in the high power electron linac.
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