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C. Ekdahl,
P. Aragon,
E.O. Abeyta,
R. Bartsch,
L. Caudill,
K.C.D. Chan,
D. Dalmas,
S. Eversole,
R. Gallegos,
J. Harrison, [......],
A. Meidinger,
K. Moy,
R. Sturgess,
A. Tipton,
C.Y. Tom,
M. Schulze,
T. Hughes,
C. Mostrom,
Y. Tang,
R. Briggs
[show abstract]
[hide abstract]
ABSTRACT: When completed, the DARHT-II linear induction accelerator (LIA) will produce a 2-kA, 18-MeV electron beam with more than 1500-ns current/energy "flat-top." In initial tests DARHT-II has already accelerated beams with current pulse lengths from 500-ns to 1200-ns full- width at half maximum (FWHM) with more than 1.2- kA, 12.5-MeV peak current and energy. New experiments are planned with a ~1600-ns pulse length but with reduced current and energy. These pulse lengths are all significantly longer than any other multi-MeV LIA, and they define a novel regime for high-current beam dynamics, especially with regard to beam stability. Although the initial tests demonstrated absence of BBU, the pulse length was too short to determine whether ion- hose instability would be present toward the end of a pulse longer than 1500-ns. The 1600-ns pulse experiments are designed to resolve these and other beam-dynamics issues with a long-pulse beam.
Pulsed Power Conference, 2005 IEEE; 07/2005
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C. Ekdahl,
E.O. Abeyta,
R. Bartsch,
L. Caudill,
K.C.D. Chan,
D. Dalmas,
S. Eversole,
R. Gallegos,
J. Harrison,
M. Holzscheiter, [......],
A. Meidinger,
K. Moy,
R. Sturgess,
A. Tipton,
C.Y. Tom,
M. Schulze,
T. Hughes,
C. Mostrom,
Y. Tang,
R. Briggs
[show abstract]
[hide abstract]
ABSTRACT: When completed, the DARHT-II linear induction accelerator (LIA) will produce a 2 kA, 18 MeV electron beam with more than 1500 ns current/energy “flat-top.” In initial tests DARHT-II has already accelerated beams with current pulse lengths from 500 ns to 1200 ns full-width at half maximum (FWHM) with more than 1.2 kA peak current and 12.5 MeV peak energy. Experiments will soon begin with a ∼ 1600 ns flat-top pulse, but with reduced current and energy. These pulse lengths are all significantly longer than any other multi-MeV LIA, and they define a novel regime for high-current beam dynamics, especially with regard to beam stability. Although the initial tests demonstrated the robustness of the DARHT-II LIA to BBU, the < 1200 ns FWHM pulse lengths were too short to test the predicted protection against ion-hose instability. The present experiments are designed to resolve these and other beam-dynamics issues with a ∼ 1600 ns pulse length beam.
Particle Accelerator Conference, 2005. PAC 2005. Proceedings of the; 06/2005
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C. Ekdahl,
E.O. Abeyta,
H. Bender,
W. Broste,
C. Carlson,
L. Caudill,
K.C.D. Chan,
Y.J. Chen,
D. Dalmas,
G. Durtschi, [......],
M. Schauer,
D. Simmons,
H.V. Smith, J. Studebaker,
R. Sturgess,
G. Sullivan,
C. Swinney,
R. Temple,
C.Y. Tom,
S.S. Yu
[show abstract]
[hide abstract]
ABSTRACT: The DARHT-II linear-induction accelerator has been successfully operated at 1.2-1.3 kA and 12.5-12.7 MeV to demonstrate the production and acceleration of an electron beam. Beam pulse lengths for these experiments were varied from 0.5 μs to 1.2 μs full-width half-maximum. A low-frequency inductance-capacitance (LC) oscillation of diode voltage and current resulted in an oscillation of the beam position through interaction with an accidental (static) magnetic dipole in the diode region. There was no growth in the amplitude of this oscillation after propagating more than 44 m through the accelerator, and there was no loss of beam current that could be measured. The results of these initial experiments are presented in this paper.
IEEE Transactions on Plasma Science 05/2005; · 1.17 Impact Factor
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B.T. McCuistian,
O. Abeyta,
P. Aragon,
L. Caudill,
C. Ekdahl,
S. Eversole,
D. Dalmans,
J. Harrison,
E. Jacquez,
J. Johnson, [......],
M. Sanchez,
J. Schwaegel,
D. Simmons, J. Studebaker,
G. Sulliva,
C. Swinney,
R. Temple,
S. Eylon,
T. Houck,
R. Sturges
[show abstract]
[hide abstract]
ABSTRACT: The dual axis radiographic hydrotest facility (DARHT) at Los Alamos National Laboratory produces flash radiographs of hydrodynamic experiments using two linear induction accelerators situated on orthogonal axes. The first axis accelerator is operational and has produced radiographs of hydrodynamic experiments. The second axis accelerator, which is in the commissioning stage, will generate an 18-MeV, 2-kA, 2-μs electron beam. These parameters are reduced during the initial phase of commissioning to ≥12-MeV, ≥1-kA, and ≥350-ns. These reduced parameters allow lower voltages and fewer components than what will be necessary for the final machine. This paper presents experimental results of commissioning the second axis DARHT accelerator, including an overview of the pulsed power system plus electrical performance data from the 3-MV injector Marx generator and the 200-kV, 2-μs induction accelerator cells. Beam transport data will also be presented.
Pulsed Power Conference, 2003. Digest of Technical Papers. PPC-2003. 14th IEEE International; 07/2003
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C. Ekdahl,
E.O. Abeyta,
L. Caudill,
K.C.D. Chan,
D. Dalmas,
S. Eversole,
R. Gallegos,
J. Harrison,
M. Holzscheiter,
J. Johnson, [......],
G. Durtschi,
D. Frayer,
D. Johnson,
K. Jones,
A. Meidinger,
K. Moy,
R. Sturgess,
C.Y. Tom,
T. Hughes,
C. Mostrom
[show abstract]
[hide abstract]
ABSTRACT: The second axis of the Dual Axis Radiographic HydroTest (DARHT) facility will provide up to four short (< 150 ns) radiation pulses for flash radiography of high-explosive driven implosion experiments. To accomplish this the DARHT-II linear induction accelerator (LIA) will produce a 2-kA electron beam with 18-MeV kinetic energy, constant to within ± 0.5% for 2-μs. A fast kicker will cleave four short pulses out of the 2-μs flattop, with the bulk of the beam diverted into a dump. The short pulses will then be transported to the final-focus magnet, and focused onto a tantalum target for conversion to bremsstrahlung pulses for radiography. DARHT-II is a collaborative effort between the Los Alamos, Lawrence Livermore, and Lawrence Berkeley National Laboratories of the University of California.
Particle Accelerator Conference, 2003. PAC 2003. Proceedings of the; 06/2003
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P.J. Turchi,
K. Alvey,
C. Adams,
B. Anderson,
H.D. Anderson,
W.E. Anderson,
E. Armijo,
W.L. Atchison,
J. Bartos,
R.L. Bowers, [......],
G. Rodriguez,
D. Sandoval,
G. Sandoval,
M.A. Salazar,
W. Sommars,
W. Steckle,
J.L. Stokes, J. Studebaker,
L. Tabaka,
A.J. Taylor
[show abstract]
[hide abstract]
ABSTRACT: We discuss the design, fabrication, and operation of a liner implosion system at peak currents of 16 MA. Liners of 1100 aluminum, with initial length, radius, and thickness of 4 cm, 5 cm, and 1 mm, respectively, implode under the action of an axial current, rising in 8 μs. Fields on conductor surfaces exceed 0.6 MG. Design and fabrication issues that were successfully addressed include: Pulsed Power-especially current joints at high magnetic fields and the possibility of electrical breakdown at connection of liner cassette insulator to bank insulation; Liner Physics-including the angle needed to maintain current contact between liner and glide-plane/electrode without jetting or buckling; Diagnostics-X-radiography through cassette insulator and outer conductor without shrapnel damage to film.
IEEE Transactions on Plasma Science 11/2002; · 1.17 Impact Factor
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P.J. Turchi,
K. Alvey,
B. Anderson,
H.D. Anderson,
W. Anderson,
W.L. Atchison,
J. Bartos,
R.L. Bowers,
R. Corrow,
J. Echave, [......], J. Studebaker,
L. Tabaka,
A.J. Taylor,
T. Cavazos,
S. Coffey,
J.H. Degnan,
D. Gale,
G. Kiuttu,
R.E. Peterkin,
W. Sommars
[show abstract]
[hide abstract]
ABSTRACT: Electromagnetically-driven implosion of solid-density, cylindrical liners can launch shocks with excellent precision at impact speeds exceeding 5 km/s. We discuss the design and operation of liner implosions driven at peak currents of 16MA, using the Shiva Star capacitor bank at the Air Force Research Laboratory. Liners of 1100 aluminum, with initial length, radius and thickness of 4 cm, 5 cm and 1 mm, respectively, implode under the action of an axial current, rising in 8 μs. Fields on conductor surfaces exceed 0.6 MG. The inner surface of the liner achieves a speed of 6.25 km/s when it impacts a concentric target cylinder of tin at a radius of 2 cm. Magnetic probes and radially-aligned X-radiography follow the motion of the liner and its impact on the tin cylinder. This cylinder holds a solid cylinder of acrylic of 1.5 cm radius in which the motion of a converging shock is followed by optical shadowgraphy and axially-aligned, X-radiography. Design issues that were successfully addressed include: Pulsed Power - current joints at high magnetic fields in the vicinity of the liner and glide-plane/electrodes, where magnetic pressures quickly exceed values for mechanical pre-stress, requiring dynamic solutions; surface temperature enhancements at changes in current direction; possibility of electrical breakdown at connection of liner cassette insulator to bank insulation; need for magnetic inhibition of breakdown (MIB) between liner surface and insulator; Liner Physics - angle needed to maintain current contact between liner and glide-plane/electrode without jetting or buckling; nonlinear magnetic diffusion into liner and associated melting; Diagnostics X-radiography through cassette insulator and outer conductor without shrapnel damage to film.
Pulsed Power Plasma Science, 2001. PPPS-2001. Digest of Technical Papers; 02/2001
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B.E. Carlsten,
M.L. Milder,
J.M. Kinross-Wright,
D.W. Feldman,
S. Russell,
J.G. Plato,
A. Shapiro,
B. Sherwood, J. Studebaker,
R. Lovato,
D. Warren,
C. Timmer,
R. Cooper,
R. Sturges,
M. Williams
[show abstract]
[hide abstract]
ABSTRACT: We have designed and are building a subpicosecond electron
injector. The injector is based on an 8 MeV photoinjector, used
previously at Los Alamos in the APEX experiment. The nominal design
includes magnetically compressing a 20 ps long, 3 nC bunch to a FWHM
bunch length of 2/3 ps (peak current in excess of 3 kA) using a four
dipole chicane buncher. The geometrical averaged transverse normalized
transverse emittance after compression is about 15 π mm mrad
Particle Accelerator Conference, 1995., Proceedings of the 1995; 06/1995
