PAC07 - List of Authors (Waldron, W. L.)

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Waldron, W. L.

Paper	Title	Page
TUYC01	Studies of the Pulse Line Ion Accelerator	852
	W. L. Waldron, E. Henestroza, L. R. Reginato LBNL, Berkeley, California R. J. Briggs SAIC, Alamo, California A. Friedman LLNL, Livermore, California
	Funding: This work was supported by the Director, Office of Science, Office of Fusion Energy Sciences, of the U. S. Department of Energy under Contracts No. DE-AC02-05CH11231 and W-7405-Eng-48. The Pulse Line Ion Accelerator concept was motivated by the need for an inexpensive way to accelerate intense short pulse heavy ion beams to regimes of interest for studies of High Energy Density Physics and Warm Dense Matter. A pulse power driver applied to one end of a helical pulse line creates a traveling wave that accelerates and axially confines the heavy ion beam pulse. The concept has been demonstrated with ion beams at modest acceleration gradients. Acceleration scenarios with constant parameter helical lines are described which result in output energies of a single stage much larger than the several hundred kilovolt peak voltages on the line, with a goal of 3-5 MeV/m acceleration gradients. This method has the potential to reduce the length of an equivalent induction accelerator by a factor of 6-10 while simplifying the pulsed power systems. The performance of prototype hardware has been limited by high voltage flashover across the vacuum insulator. Bench tests and analysis have led to significantly improved flashover thresholds. Further studies using a variety of experimental configurations are planned.
	Slides
WEPMS016	Modeling the Pulse Line Ion Accelerator (PLIA): An Algorithm for Quasi-Static Field Solution	2364
	A. Friedman, D. P. Grote LLNL, Livermore, California R. J. Briggs SAIC, Alamo, California E. Henestroza, W. L. Waldron LBNL, Berkeley, California
	Funding: Work performed under auspices of U. S. DoE by the Univ. of CA, LLNL & LBNL under Contract Nos. W-7405-Eng-48 and DE-AC02-05CH11231 The Pulse-Line Ion Accelerator* (PLIA) is a helical distributed transmission line. A rising pulse applied to the upstream end appears as a moving spatial voltage ramp, on which an ion pulse can be accelerated. This is a promising approach to acceleration and longitudinal compression of an ion beam at high line charge density. In most of the studies carried out to date, using both a simple code for longitudinal beam dynamics and the Warp PIC code, a circuit model for the wave behavior was employed; in Warp, the helix I and V are source terms in elliptic equations for E and B. However, it appears possible to obtain improved fidelity using a "sheath helix" model in the quasi-static limit. Here we describe an algorithmic approach that may be used to effect such a solution. *R. J. Briggs, PRST-AB 9, 060401 (2006).
WEPMS024	Upgrades to the DAHRT Second Axix Induction Cells	2385
	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
	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.
THPAS082	Meter-Long Plasma Source for Heavy Ion Beam Space Charge Neutralization	3672
	P. Efthimion, R. C. Davidson, E. P. Gilson, L. Grisham PPPL, Princeton, New Jersey B. G. Logan, P. A. Seidl, W. L. Waldron, S. Yu LBNL, Berkeley, California
	Funding: Research supported by the U. S. Department of Energy. Plasmas are sources of electrons for charge neutralizing ion beams to allow them to focus to small spot sizes and compress their axial pulse length. Sources must operate at low pressures and without strong electric/magnetic fields. To produce meter-long plasmas, sources based on ferroelectric ceramics with large dielectric coefficients were developed. The sources use BaTiO3 ceramic to form plasma. The drift tube inner wall of the Neutralized Drift Compression Experiment (NDCX) is covered with ceramic and ~7 kV is applied across the wall of the ceramics. A 20-cm-long prototype source produced plasma densities of 5·10¹¹ cm^-3. It was integrated into the Neutralized Transport Experiment and successfully neutralized the K+ beam. A one-meter-long source comprised of five 20-cm-long sources has been tested and characterized, producing relatively uniform plasma over the length of the source in the 1·10¹⁰ cm^-3 range. This source was integrated into NDCX for beam compression experiments. Experiments with this source yielded compression ratios ~80. Future work will consider longer and higher plasma density sources to support beam compression and high energy density experiments.
THPAS006	A Solenoid Final Focusing System with Plasma Neutralization for Target Heating Experiments	3519
	P. K. Roy, F. M. Bieniosek, J. E. Coleman, J.-Y. Jung, M. Leitner, B. G. Logan, P. A. Seidl, W. L. Waldron LBNL, Berkeley, California J. J. Barnard, A. W. Molvik LLNL, Livermore, California R. C. Davidson, P. Efthimion, E. P. Gilson, A. B. Sefkow PPPL, Princeton, New Jersey J. A. Duersch, D. Ogata UCB, Berkeley, California D. R. Welch Voss Scientific, Albuquerque, New Mexico
	Intense bunches of low-energy heavy ions have been suggested as means to heat targets to the warm dense matter regime (0.1 to 10 eV). In order to achieve the required intensity on target (~1 eV heating), a beam spot radius of approximately 0.5 mm, and pulse duration of 2 ns is required with an energy deposition of approximately 1 J/cm². This translates to a peak beam current of 8A for ~0.4 MeV K+ ions. To increase the beam intensity on target, a plasma-filled high-field solenoid is being studied as a means to reduce the beam spot size from several mm to the sub-mm range. We are building a prototype experiment to demonstrate the required beam dynamics. The magnetic field of the pulsed solenoid is 5 to 8 T. Challenges include suitable injection of the plasma into the solenoid so that the plasma density near the focus is sufficiently high to maintain space-charge neutralization of the ion beam pulse. Initial experimental results for a peak current of ~1A will be presented. This work was supported by the Office of Fusion Energy Sciences, of the U. S. Department of Energy under Contract No. DE-AC02-05CH11231, W-7405-Eng-48, DE-AC02-76CH3073 for HIFS-VNL.