| Paper | Title | Page |
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| MPPT069 | A Pulsed Solenoid for Intense Ion Beam Transport | 3798 |
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Funding: This work was supported by the Director, Office of Science, Office of Fusion Energy Sciences, of the U.S. Department of Energy under Contract No. DE-AC03-76SF00098. A design for a pulsed solenoid magnet is presented. Some simple design formulas are given that are useful for initial design scoping. Design features to simplify fabrication and improve reliability are presented. Fabrication, assembly, and test results are presented. |
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| TPAT036 | Ferroelectric Plasma Source for Heavy Ion Beam Charge Neutralization | 2452 |
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Funding: Research supported by the U.S. Department of Energy. Plasmas are employed as a medium for charge neutralizing heavy ion beams to allow them to focus to a small spot size. Calculations suggest that plasma at a density of 1-100 times the ion beam density and at a length ~ 0.1-1 m would be suitable. To produce 1 meter plasma, large-volume plasma sources based upon ferroelectric ceramics are being considered. These sources have the advantage of being able to increase the length of the plasma and operate at low neutral pressures. The source will utilize the ferroelectric ceramic BaTiO3 to form metal plasma. The drift tube inner surface of the Neutralized Drift Compression Experiment (NDCX) will be covered with ceramic. High voltage (~ 1-5 kV) is applied between the drift tube and the front surface of the ceramic by placing a wire grid on the front surface. A prototype ferroelectric source 20 cm long produced plasma densities ~ 5x1011 cm-3. The source was integrated into the experiment and successfully charge neutralized the K ion beam. Presently, the 1 meter source is being fabricated. It will be characterized and integrated into NDCX for charge neutralization experiments. Experimental results will be presented. |
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| TPAT068 | A Fast Faraday Cup for the Neutralized Drift Compression Experiment | 3765 |
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Funding: Research supported by the U.S. Department of Energy. Heavy ion drivers for high energy density physics applications and inertial fusion energy use space-charge-dominated beams which require longitudinal bunch compression in order to achieve sufficiently high beam intensity at the target. The Neutralized Drift Compression Experiment-1A (NDCX-1A) at Lawrence Berkeley National Laboratory (LBNL) is used to determine the effective limits of neutralized drift compression. NDCX-1A investigates the physics of longitudinal drift compression of an intense ion beam, achieved by imposing an initial velocity tilt on the drifting beam and neutralizing the beam's space-charge with background plasma. Accurately measuring the longitudinal compression of the beam pulse with high resolution is critical for NDCX-1A, and an understanding of the accessible parameter space is modeled using the LSP particle-in-cell (PIC) code. The design and preliminary experimental results for an ion beam probe which measures the total beam current at the focal plane as a function of time are summarized. |
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| ROAB005 | Helical Pulseline Structures for Ion Acceleration | 440 |
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Funding: This work was performed under the auspices of the U.S. Department of Energy by the University of California, Lawrence Berkeley National Laboratory, Contract DE-AC03-76SF00098. The basic concept of the "Pulseline Ion Accelerator" involves launching a ramped high voltage pulse on a broad band traveling wave (slow-wave) structure. An applied voltage pulse at the input end with a segment rising linearly in time becomes a linear voltage ramp in space that propagates down the line, corresponding to a (moving) region of constant axial accelerating electric field. The ions can "surf" on this traveling wave, experiencing a total energy gain that can greatly exceed the peak of the applied voltage. The applied voltage waveform can also be shaped to longitudinally confine the beam against its own space charge forces, and (in the final stage) to impart an inward compression to the beam for neutralized drift compression in heavy ion HEDP applications. In the first stages of a heavy ion accelerator, the pulseline velocity needs to be the order of 1% of the speed of light and the line must be sufficiently non-dispersive for the broad band voltage pulse propagating down the line to have minimal distortion. Experimental characterization of the dispersion and pulse propagation at low voltage on several helix models will be presented, and compared with theoretical predictions.* *Caporaso, et al, "Dispersion Analysis of the Pulseline Accelerator," this conference. |
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| FPAT029 | High Voltage Operation of Helical Pulseline Structures for Ion Acceleration | 2092 |
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Funding: This work was performed under the auspices of the U.S. Department of Energy by the University of California, Lawrence Berkeley National Laboratory, Contract # DE-AC03-76SF00098. The basic concept for the acceleration of heavy ions using a helical pulseline requires the launching of a high voltage traveling wave with a waveform determined by the beam transport physics in order to maintain stability and acceleration.* This waveform is applied to the front of the helix, creating over the region of the ion bunch a constant axial acceleration electric field that travels down the line in synchronism with the ions. Several methods of driving the helix have been considered. Presently, the best method of generating the waveform and also maintaining the high voltage integrity appears to be a transformer primary loosely coupled to the front of the helix, generating the desired waveform and achieving a voltage step-up from primary to secondary (the helix). This can reduce the drive voltage that must be brought into the helix enclosure through the feedthroughs by factors of 5 or more. The accelerating gradient is limited by the voltage holding of the vacuum insulator, and the material and helix geometry must be chosen appropriately. The helix must also be terminated into its characteristic impedance, and designs of terminations incorporated into the helix internal enclosure are presented in the paper. *Briggs, et al, "Helical Pulseline Structures for Ion Acceleration," this conference. |
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| FPAT037 | Electromagnetic Simulations of Helical-Based Ion Acceleration Structures | 2485 |
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Funding: This work was performed under the auspices of the U.S. Department of Energy by the University of California, Lawrence Livermore National Laboratory under Contract No. W-7405-Eng-48. Helix structures have been proposed* for accelerating low energy ion beams using MV/m fields in order to increase the coupling effeciency of the pulsed power system and to tailor the electromagnetic wave propagation speed with the particle beam speed as the beam gains energy. Calculations presented here show the electromagnetic field as it propagates along the helix structure, field stresses around the helix structure (for voltage breakdown determination), optimizations to the helix and driving pulsed power waveform, and simulations showing test particles interacting with the simulated time varying fields. *"Helical Pulseline Structures for Ion Acceleration," Briggs, Reginato, Waldron, this conference. |
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| ROAB003 | Highly Compressed Ion Beams for High Energy Density Science | 339 |
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Funding: Work performed under auspices of USDOE by U. of CA LLNL & LBNL, PPPL, and SNL, under Contract Nos. W-7405-Eng-48, DE-AC03-76SF00098, DE-AC02-76CH03073, and DE-AC04-94AL85000, and by MRC and SAIC. The Heavy Ion Fusion Virtual National Laboratory (HIF-VNL) is developing the intense ion beams needed to drive matter to the High Energy Density (HED) regimes required for Inertial Fusion Energy (IFE) and other applications. An interim goal is a facility for Warm Dense Matter (WDM) studies, wherein a target is heated volumetrically without being shocked, so that well-defined states of matter at 1 to 10 eV are generated within a diagnosable region. In the approach we are pursuing, low to medium mass ions with energies just above the Bragg peak are directed onto thin target "foils," which may in fact be foams or "steel wool" with mean densities 1% to 100% of solid. This approach complements that being pursued at GSI, wherein high-energy ion beams deposit a small fraction of their energy in a cylindrical target. We present the requirements for warm dense matter experiments, and describe suitable accelerator concepts, including novel broadband traveling wave pulse-line, drift-tube linac, RF, and single-gap approaches. We show how neutralized drift compression and final focus optics tolerant of large velocity spread can generate the necessarily compact focal spots in space and time. |
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| ROPB002 | Experiments Studying Desorbed Gas and Electron Clouds in Ion Accelerators | 194 |
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Funding: This work was performed under the auspices of the U.S. Department of Energy by University of California, LLNL under contract No. W-7405-Eng-48, and by LBNL under Contract DE-AC03-76F00098. Electron clouds and gas pressure rise limit the performance of many major accelerator rings. We are studying these issues experimentally with ~1 MeV heavy-ion beams, coordinated with significant efforts in self-consistent simulation and theory.* The experiments use multiple diagnostics, within and between quadrupole magnets, to measure the sources and accumulation of electrons and gas. In support of these studies, we have measured gas desorption and electron emission coefficients for potassium ions impinging on stainless steel targets at angles near grazing incidence.** Our goal is to measure the electron particle balance for each source – ionization of gas, emission from beam tubes, and emission from an end wall – determine the electron effects on the ion beam and apply the increased understanding to mitigation. *J-L. Vay, Invited paper, session TICP; R. H. Cohen et al., PRST-AB 7, 124201 (2004). **M. Kireeff Covo, this conference; A. W. Molvik et al., PRST-AB 7, 093202 (2004). |
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| FPAE071 | Initial Results on Neutralized Drift Compression Experiments (NDCX-IA) for High Intensity Ion Beam | 3856 |
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Funding: This work was supported by the Director, Office of Science, Office of Fusion Energy Sciences, of the U.S. Department of Energy under Contract No. DE-AC03-76SF00098. Ion beam neutralization and compression experiments are designed to determine the feasibility of using compressed high intensity ion beams for high energy density physics (HEDP) experiments and for inertial fusion power. To quantitatively ascertain the various mechanisms and methods for beam compression, the Neutralized Drift Compression Experiment (NDCX) facility is being constructed at Lawrence Berkeley National Laboratory (LBNL). In the first compression experiment, a 260 KeV, 25 mA, K+ ion beam of centimeters size is radially compressed to a mm size spot by neutralization in a meter-long plasma column and beam peak current is longitudinally compressed by an induction velocity tilt core. Instrumentation, preliminary results of the experiments, and practical limits of compression are presented. These include parameters such as emittance, degree of neutralization, velocity tilt time profile, and accuracy of measurements (fast and spatially high resolution diagnostic) are discussed. |
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| FOAA002 | Technological Improvements in the DARHT II Accelerator Cells | 169 |
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Funding: This work was supported by the U.S. National Nuclear Security Agency and the U.S. Department of Energy under contract W-7405-ENG-36. DARHT employs two perpendicular electron Linear Induction Accelerators to produce intense, bremsstrahlung x-ray pulses for flash radiography. The second axis, DARHT II, features an 18 MeV, 2-kA, 2-microsecond accelerator. DARHT II accelerator cells have undergone a series of test and modeling efforts to fully understand their sub par performance. These R&D efforts have led to a better understanding of Linear Induction Accelerator physics for the unique DARHT II design. Specific improvements have been identified and tested. Improvements in the cell oil region, the cell vacuum region, and the PFNs have been implemented in the prototype units that have doubled the cell’s performance. A series of prototype acceptance test are underway on a number of prototype units to demonstrate that the required cell lifetime is met at the improved performance levels. Early acceptance tests indicate that the lifetime requirements are being exceeded. The shortcomings of the previous design are summarized. The improvements to the original design, their resultant improvement in performance, and various test results are included. The final acceptance test results will also be included. |