| Paper |
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| WEPMS024 |
Upgrades to the DAHRT Second Axix Induction Cells
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2385 |
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- K. Nielsen, J. Barraza, M. Kang
LANL, Los Alamos, New Mexico
- F. M. Bieniosek, K. Chow, W. M. Fawley, E. Henestroza, L. R. Reginato, W. L. Waldron
LBNL, Berkeley, California
- R. J. Briggs, B. A. Prichard
SAIC, Los Alamos, New Mexico
- T. E. Genoni, T. P. Hughes
Voss Scientific, Albuquerque, New Mexico
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The Dual-Axis Radiographic Hydrodynamics Test (DARHT) facility will employ two perpendicular electron Linear Induction Accelerators to produce intense, bremsstrahlung x-ray pulses for flash radiography. The second axis, DARHT II, features a 3-MeV injector and a 15-MeV, 2-kA, 1.6-microsecond accelerator consisting of 74 induction cells and drivers. Major induction cell components include high flux swing magnetic material (Metglas 2605SC) and a MycalexTM insulator. The cell drivers are pulse forming networks (PFNs). The DARHT II accelerator cells have undergone a series of test and modeling efforts to fully understand their operational parameters. Physical changes in the cell oil region, the cell vacuum region, and the cell drivers, together with different operational and maintenance procedures, have been implemented in the prototype. A series of prototype acceptance tests have demonstrated that the required cell lifetime is met at the increased performance levels. Shortcomings of the original design are summarized and improvements to the design, their resultant enhancement in performance, and various test results are discussed.
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| THOBAB02 |
Commissioning the DARHT-II Scaled Accelerator Downstream Transport
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2627 |
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- M. E. Schulze
SAIC, Los Alamos, New Mexico
- E. O. Abeyta, P. Aragon, R. Archuleta, J. Barraza, D. Dalmas, C. Ekdahl, K. Esquibel, S. Eversole, R. J. Gallegos, J. F. Harrison, E. Jacquez, J. Johnson, P. S. Marroquin, B. T. McCuistian, N. Montoya, S. Nath, L. J. Rowton, R. D. Scarpetti, M. Schauer
LANL, Los Alamos, New Mexico
- R. Anaya, G. J. Caporaso, F. W. Chambers, Y.-J. Chen, S. Falabella, G. Guethlein, J. F. McCarrick, B. A. Raymond, R. A. Richardson, J. A. Watson, J. T. Weir
LLNL, Livermore, California
- H. Bender, W. Broste, C. Carlson, D. Frayer, D. Johnson, A. Tipton, C.-Y. Tom
NSTec, Los Alamos, New Mexico
- T. C. Genoni, T. P. Hughes, C. H. Thoma
Voss Scientific, Albuquerque, New Mexico
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The DARHT-II accelerator will produce a 2-kA, 17-MeV beam in a 1600-ns pulse when completed this summer. After exiting the accelerator, the long pulse is sliced into four short pulses by a kicker and quadrupole septum and then transported for several meters to a tantalum target for conversion to bremsstrahlung for radiography. We describe tests of the kicker, septum, transport, and multi-pulse converter target using a short accelerator assembled from the first available refurbished cells, which are now capable of operating of operating at over 200 kV. This scaled accelerator was operated at ~ 8 Mev and ~1 kA, which provides a beam with approximately the same nu/gamma as the final 17-MeV, 2-kA beam, and therefore the same beam dynamics in the downstream transport. The results of beam measurements made during the commissioning of this scaled accelerator downstream transport are described.
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Slides
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| THPAN082 |
Implementation of Spread Mass Model of Ion Hose Instability in Lamda
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3408 |
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- Y. Tang
ATK-MR, Albuquerque, New Mexico
- C. Ekdahl
LANL, Los Alamos, New Mexico
- T. C. Genoni, T. P. Hughes
Voss Scientific, Albuquerque, New Mexico
- M. E. Schulze
SAIC, Los Alamos, New Mexico
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Funding: Work supported by Los Alamos National Laboratory.
The ion-hose instability sets limits on the allowable vacuum in the DARHT-2 linear induction accelerator (2kA, 18.6MeV, 2μs). Lamda is a transport code which advances the beam centroid and envelope in a linear induction accelerator from the injector to the final focus region. The code computes the effect of magnet misalignments, beam breakup instability, image-displacement instability, and gap voltage fluctuation on the beam. In this work, we have implemented the Spread Mass (SM) model of ion-hose instability into Lamda so that we can examine quickly the operating parameters for the experiments. Unlike the ordinary SM ion-hose code which assumes the uniform axial magnetic field, Lamda ion-hose calculation includes varying axial magnetic field, accelerating beam, gas pressure file, varying beam radius and elliptical beam. The benchmarks against a semi-analytical SM code and the particle-in-cell code Lsp, and a prediction of ion-hose instability for a 2.5MeV-1.4kA beam in the DARHT-2 are presented.
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| THPAN083 |
A Beam-Slice Algorithm for Transport Simulations of the DARHT-2 Accelerator
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3411 |
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- C. H. Thoma
ATK-MR, Albuquerque, New Mexico
- T. P. Hughes
Voss Scientific, Albuquerque, New Mexico
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A beam-slice algorithm has been implemented into the Lsp particle-in-cell (PIC) code to allow for efficient simulation of beam electron transport through a long accelerator. The slice algorithm pushes beam particles along a virtual axial dimension and performs a field solve on a transverse grid which moves with the particle slice. Any external electric and magnetic fields are also applied to the slice at each time step. For an axisymmetric beam problem the slice algorithm is very fast compared to full 2-D r-z PIC simulations. The algorithm also calculates beam emittance growth due to mismatch oscillations, in contrast to standard envelope codes which assume constant emittance. Using the slice algorithm we are able to simulate beam transport in the DARHT-2 accelerator at LANL from the region just downstream of the diode to the end of the accelerator, a distance of about 50 meters. Results from the slice simulation are compared to both 2-D PIC simulations and the beam envelope code Lamda. The sensitivity of the final emittance to imperfect tuning of the transport solenoids is calculated.
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