| Paper |
Title |
Page |
| MOP030 |
An Upgrade to NSCL to Produce Intense Beams of Exotic Nuclei
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103 |
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- R. C. York, M. Doleans, D. Gorelov, T. L. Grimm, W. Hartung, F. Marti, S. O. Schriber, X. Wu, Q. Zhao
NSCL, East Lansing, Michigan
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A substantially less costly alternative to the Rare Isotope Accelerator (RIA) project has been developed at Michigan State University (MSU). By upgrading the existing facility at the National Superconducting Cyclotron Laboratory (NSCL), it will be possible to produce stable beams of heavy ions at energies of greater than 180 MeV/u with beam power in excess of >80 kW. The upgrade will utilize a cyclotron injector and superconducting driver linac at a base frequency of 80.5 MHz. Radioactive ion beams will be produced in a high-power target via particle fragmentation. A charge-stripping foil and multiple-charge-state acceleration will be used for the heavier ions. The 9 MeV/u injector will include an ECR source, a bunching system, and the existing K1200 superconducting cyclotron with axial injection. The superconducting driver linac will largely follow that proposed by MSU for RIA, using cavities already designed, prototyped, and demonstrated for RIA. The existing A1900 Fragmentation Separator and experimental areas will be used, along with a new gas stopper and reacceleration system.
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| MOP031 |
Beam Distribution System for the MSU-RIA Driver Linac
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106 |
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- M. Doleans, V. Andreev, X. Wu, R. C. York
NSCL, East Lansing, Michigan
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The proposed Rare Isotope Accelerator (RIA) facility will deliver up to 400 kW of any stable isotope to multi-target areas to create radioactive ion beams using either Isotope Separation On Line or Particle Fragmentation methods. Operational and programmatic efficiency will be best served by a system that can simultaneously distribute the beam current over a large dynamic range to several targets. The proposed RIA beam switchyard uses an rf kicker-magnetic septum system to distribute the beam to multi-target areas on a micro-bunch by micro-bunch basis. The micro-bunches can be differentially loaded in the RIA driver linac front end utilizing a scheme similar to that successfully used at Mainz and JLAB CEBAF facility. In these cases, consecutive electron micro-bunches are deflected by an rf kicker and their intensity separately adjusted through variable apertures with an identical second rf kicker returning the micro-bunches on-axis. The feasibility of using a similar system in RIA driver linac front end was explored. The overall concept of the RIA beam distribution system including the differential bunch loading system and the results of the beam dynamics studies will be presented.
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| TUP085 |
Beam Simulations for the MSU-RIA Driver Linac Using IMPACT Code
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457 |
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- Q. Zhao, M. Doleans, D. Gorelov, F. Marti, X. Wu, R. C. York
NSCL, East Lansing, Michigan
- J. Qiang
LBNL, Berkeley, California
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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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| THP047 |
Prototyping of a Single-Cell Half-Reentrant Superconducting Cavity
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685 |
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- M. S. Meidlinger, J. Bierwagen, S. Bricker, C. Compton, T. L. Grimm, W. Hartung, M. J. Johnson, J. Popielarski, L. Saxton, R. C. York
NSCL, East Lansing, Michigan
- E. Zaplatin
FZJ, Jülich
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As superconducting niobium cavities achieve higher gradients, it is anticipated they will reach a performance limit as the peak surface magnetic field approaches the critical magnetic field. "Low loss" and "reentrant" cavity designs are being studied at CEBAF, Cornell, DESY, and KEK, with the goal of reaching higher gradients via lower surface magnetic field, at the expense of higher surface electric field. At present, cavities must undergo chemical etching and high-pressure water rinsing to achieve good performance. It is not clear whether this can be done effectively and reliably for multi-cell low loss or reentrant cavities using traditional techniques. A "half-reentrant" cavity shape has been developed with RF parameters similar to the low loss and reentrant cavities, but with the advantage that the surface preparation can be done easily with existing methods. Two prototype single-cell half-reentrant cavities are being fabricated at 1.3 GHz; the non-reentrant wall angle is 8 degrees, the beam tube radius is 29 mm, and the cell-to-cell coupling is 1.47%. The half-reentrant cavity design and the results and status of the prototyping effort will be presented.
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| THP066 |
Lorentz-Force Detuning Analysis for Low-Loss, Re-entrant and Half-Reentrant Superconducting RF Cavities
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734 |
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- E. Zaplatin
FZJ, Jülich
- T. L. Grimm, W. Hartung, M. J. Johnson, M. S. Meidlinger, J. Popielarski, R. C. York
NSCL, East Lansing, Michigan
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The RF design of a superconducting elliptical cavity requires a trade-off in the optimization of the cell shape between the region of high electric field and the region of high magnetic field. In practice, the cavity performance may be limited not by the RF characteristics, but by detuning due to the Lorentz force, bath pressure fluctuations, or microphonics; Lorentz force detuning is of concern primarily for pulsed accelerators such as the proposed International Linear Collider. Hence the structural properties must also be taken into account in the cavity design. Several new cavity shapes are being developed in which the surface magnetic field is decreased relative to the TeSLA cavity shape, with the goal of reaching a higher accelerating gradient. This study will compare the Lorentz force detuning characteristics of the TeSLA, "low-loss", "reentrant", and "half-reentrant" cavity middle cells, and explore possible methods for stiffening the structures.
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| TUP079 |
RIAPMTQ/IMPACT: Beam-Dynamics Simulation Tool for RIA
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441 |
| |
- T. P. Wangler, J. A. Billen, R. W. Garnett
LANL, Los Alamos, New Mexico
- V. N. Aseev, B. Mustapha, P. N. Ostroumov
ANL, Argonne, Illinois
- K. R. Crandall
TechSource, Santa Fe, New Mexico
- M. Doleans, D. Gorelov, X. Wu, R. C. York, Q. Zhao
NSCL, East Lansing, Michigan
- J. Qiang, R. D. Ryne
LBNL, Berkeley, California
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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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| THP075 |
RF Performance of a Superconducting S-Band Cavity Filled with Liquid Helium
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755 |
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- W. Hartung, J. Bierwagen, S. Bricker, C. Compton, T. L. Grimm, M. J. Johnson, D. Meidlinger, D. Pendell, J. Popielarski, L. Saxton, R. C. York
NSCL, East Lansing, Michigan
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Copper RF cavities filled with hydrogen gas at high pressure have been studied recently by Muons, Inc. and IIT for simultaneous acceleration and ionisation cooling of a muon beam. A further step in this direction would be a superconducting RF cavity filled with liquid helium. One might imagine that this would make the cavity less vulnerable to thermal breakdown, field emission, and multipacting. A disadvantage is that magnetostatic focussing of the beam could not be done simultaneously. Preliminary RF testing has been done on a 2.45 GHz single-cell elliptical cavity filled with liquid helium. Low-field results indicate little or no increase in the power dissipation, consistent with predictions and measurements in the literature. The frequency shift with pressure for a cavity filled with saturated liquid is about 100 times greater than for a cavity under vacuum, consistent with published values of liquid helium permittivity as a function of temperature. Investigation of the high-field performance of a liquid-filled cavity is in progress.
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| THP076 |
Prototyping of a Superconducting Elliptical Cavity for a Proton Linac
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758 |
| |
- W. Hartung, J. Bierwagen, S. Bricker, C. Compton, T. L. Grimm, M. J. Johnson, D. Meidlinger, J. Popielarski, L. Saxton, R. C. York
NSCL, East Lansing, Michigan
- G. W. Foster, I. G. Gonin, T. K. Khabiboulline, N. Solyak, R. Wagner, V. Yarba
Fermilab, Batavia, Illinois
- P. Kneisel
Jefferson Lab, Newport News, Virginia
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A superconducting cavity has been designed for acceleration of particles travelling at 81% the speed of light (β = 0.81). Possible applications include the proposed Fermilab Proton Driver Linac. The cell shape is similar to the β = 0.81 cavity for the Spallation Neutron Source Linac, but the resonant frequency is 1.3 GHz rather than 805 MHz and the beam tube diameter matches that of the 1.3 GHz cavity for the TeSLA Test Facility. Six single-cell prototypes are being fabricated and tested. Three of these cavities are being formed from standard high purity fine grain niobium sheet. The rest are being fabricated from large grain niobium, following up on the work at Jefferson Lab to investigate the potential of large grain material for cost savings and/or improved RF performance. The fabrication of two 7-cell cavity prototypes (one fine grain, one large grain) is planned. A status report on this prototyping effort will be presented.
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