17 Matching Results

Search Results

Advanced search parameters have been applied.

High Current Ion Sources and Injectors for Heavy Ion Fusion

Description: Heavy ion beam driven inertial fusion requires short ion beam pulses with high current and high brightness. Depending on the beam current and the number of beams in the driver system, the injector can use a large diameter surface ionization source or merge an array of small beamlets from a plasma source. In this paper, we review the scaling laws that govern the injector design and the various ion source options including the contact ionizer, the aluminosilicate source, the multicusp plasma source, and the MEVVA source.
Date: February 15, 2005
Creator: Kwan, Joe W.
Partner: UNT Libraries Government Documents Department

Developing high brightness and high current beams for HIF injectors

Description: The US Heavy Ion Fusion Virtual National Laboratory is continuing research into ion sources and injectors that simultaneously provide high current (0.5-1.0 Amps) and high brightness (normalized emittance better than 1.0 {pi}-mm-mr). The central issue of focus is whether to continue pursuing the traditional approach of large surface ionization sources or to adopt a multiaperture approach that transports many smaller ''beamlets'' separately at low energies before allowing them to merge. For the large surface source concept, the recent commissioning of the 2-MeV injector for the High Current eXperiment has increased our understanding of the beam quality limitations for these sources. We have also improved our techniques for fabricating large diameter aluminosilicate sources to improve lifetime and emission uniformity. For the multiaperture approach, we are continuing to study the feasibility of small surface sources and a RF induced plasma source in preparation for beamlet merging experiments, while continuing to run computer simulations for better understanding of this alternate concept. Experiments into both architectures will be performed on a newly commissioned ion source test stand at LLNL called STS-500. This stand test provides a platform for testing a variety of ion sources and accelerating structures with 500 kV, 17-microsecond pulses. Recent progress in these areas will be discussed as well as plans for future experiments.
Date: May 24, 2002
Creator: Ahle, Larry; Grote, Dave & Kwan, Joe
Partner: UNT Libraries Government Documents Department

Source fabrication and lifetime for Li+ ion beams extracted from alumino-silicate sources

Description: A space-charge-limited beam with current densities (J) exceeding 1 mA/cm{sup 2} have been measured from lithium alumino-silicate ion sources at a temperature of #24;~1275#14;{degrees} C. At higher extraction voltages, the source appears to become emission limited with J #21;{>=} 1.5 mA/cm{sup 2}, and J increases weakly with the applied voltage. A 6.35 mm diameter source with an alumino-silicate coating, {<=}#20;0.25 mm thick, has a measured lifetime of ~#24;40 hours at ~#24;1275#14;{degrees} C, when pulsed at 0.05 Hz and with pulse length of #24;~6 μs each. At this rate, the source lifetime was independent of the actual beam charge extracted due to the loss of neutral atoms at high temperature. The source lifetime increases with the amount of alumino-silicate coated on the emitting surface, and may also be further extended if the temperature is reduced between pulses.
Date: March 5, 2012
Creator: Roy, Prabir K.; Greenway, Wayne G. & Kwan, Joe W
Partner: UNT Libraries Government Documents Department

Neutral Beam Injection for Plasma and Magnetic FieldDiagnostics

Description: At the Lawrence Berkeley National Laboratory (LBNL) adiagnostic neutral beam injection system for measuring plasma parameters,flow velocity, and local magnetic field is being developed. High protonfraction and small divergence is essential for diagnostic neutral beams.In our design, a neutral hydrogen beam with an 8 cm x 11 cm (or smaller)elliptical beam spot at 2.5 m from the end of the extraction column isproduced. The beam will deliver up to 5 A of hydrogen beam to the targetwith a pulse width of ~;1 s, once every 1 - 2 min. The H1+ ion species ofthe hydrogen beamwill be over 90 percent. For this application, we havecompared two types of RF driven multicusp ion sources operating at 13.56MHz. The first one is an ion source with an external spiral antennabehind a dielectric RF-window. The second one uses an internal antenna insimilar ion source geometry. The source needs to generate uniform plasmaover a large (8 cm x 5 cm) extraction area. We expect that the ion sourcewith internal antenna will be more efficient at producing the desiredplasma density but might have the issue of limited antenna lifetime,depending on the duty factor. For both approaches there is a need forextra shielding to protect the dielectric materials from the backstreaming electrons. The source walls will be made of insulator materialsuch as quartz that has been observed to generate plasma with higheratomic fraction than sources with metal walls. The ion beam will beextracted and accelerated by a set of grids with slits, thus forming anarray of 6 sheet-shaped beamlets. The multiple grid extraction will beoptimized using computer simulation programs. Neutralization of the beamwill be done in neutralization chamber, which has over 70 percentneutralization efficiency.
Date: August 1, 2007
Creator: Vainionpaa, Jaakko Hannes; Leung, Ka Ngo; Kwan, Joe W. & Levinton,Fred
Partner: UNT Libraries Government Documents Department

Design and simulation of a multi-beamlet injector for a highcurrent accelerator

Description: A multi-beamlet approach to a high current ion injector, whereby a large number of beamlets are accelerated and then merged to form a single beam, offers a number of potential advantages over a monolithic single beam injector. These advantages include a smaller transverse footprint, more control over the shaping and aiming of the beam, and more flexibility in the choice of ion sources. A potential drawback however is a larger emittance. In this paper, we seek to understand the merging of the beamlets and how it determines the emittance. When the constraints imposed by beam propagation physics and practical engineering issues are included, the design is reduced to a few free parameters. We describe the physics design of a multi-beamlet injector, and produce a design for an example set of parameters. Extensive use of 2-D and 3-D particle simulations was made in understanding the injector. Design tolerances and sensitivities are discussed in general and in relation to the example.
Date: February 14, 2002
Creator: Grote, David P.; Henestroza, Enrique & Kwan, Joe W.
Partner: UNT Libraries Government Documents Department

Characteristics of a RF-Driven Ion Source for a Neutron Generator Used For Associated Particle Imaging

Description: We present recent work on a prototype compact neutron generator for associated particle imaging (API). API uses alpha particles that are produced simultaneously with neutrons in the deuterium-tritium (2D(3T,n)4 alpha) fusion reaction to determine the direction of the neutrons upon exiting the reaction. This method determines the spatial position of each neutron interaction and requires the neutrons to be generated from a small spot in order to achieve high spatial resolution. The ion source for API is designed to produce a focused ion beam with a beam spot diameter of 1-mm or less on the target. We use an axial type neutron generator with a predicted neutron yield of 108 n/s for a 50 muA D/T ion beam current accelerated to 80 kV. The generator utilizes a RF planar spiral antenna at 13.56 MHz to create a highly efficient inductively-coupled plasma at the ion source. Experimental results show that beams with an atomic ion fraction of over 80percent can be obtained while utilizing only 100 watts of RF power in the ion source. A single acceleration gap with a secondary electron suppression electrode is used in the tube. Experimental results, such as the current density, atomic ion fraction, electron temperature, and electron density, from ion source testing will be discussed.
Date: August 8, 2008
Creator: Wu, Ying; Hurley, John P.; Ji, Qing; Kwan, Joe & Leung, Ka-Ngo
Partner: UNT Libraries Government Documents Department

HIFS VNL Monthly Progress Report Preparation for NDCX-II Project

Description: In preparation for the project and for anticipated review in August, the HIFS-VNL hosted an NDCX-II Advisory Meeting at LBNL on May 27, 2009. A number of experts in accelerator physics, engineering, and construction were asked to visit for a full day, listen to presentations on the project, its goals, and its status, and to offer their advice on how best to proceed, what topics needed attention, and what technical options seemed most attractive to them. This was a productive meeting, and the Committee's comments will provide useful guidance.
Date: May 29, 2009
Creator: Logan, Grant; Kwan, Joe; Barnard, John; Friedman, Alex; Gilson, Erik; Leitner, Matthaeus et al.
Partner: UNT Libraries Government Documents Department

Ion Source for Neutral beam injection meant for plasma and magnetic field diagnostics

Description: At the Lawrence Berkeley National Laboratory (LBNL) a diagnostic neutral beam injection system for measuring plasma parameters, flow velocity, and local magnetic field is being developed. The systems is designed to have a 90 % proton fraction and small divergence with beam current at 5-6 A and a pulse length of {approx}1 s occurring once every 1-2 min. The ion source needs to generate uniform plasma over a large (8 cm x 5 cm) extraction area. For this application, we have compared RF driven multicusp ion sources operating with either an external or an internal antenna in similar ion source geometry. The ion beam will be made of an array of six sheet-shaped beamlets. The design is optimized using computer simulation programs.
Date: June 1, 2007
Creator: Vainionpaa, Jaakko Hannes; Leung, Ka Ngo; Gough, Richard A.; Kwan, Joe W. & Levinton, Fred
Partner: UNT Libraries Government Documents Department

Synopsis of Cathode #4 Activation

Description: The purpose of this report is to describe the activation of the fourth cathode installed in the DARHT-II Injector. Appendices have been used so that an extensive amount of data could be included without danger of obscuring important information contained in the body of the report. The cathode was a 612 M type cathode purchased from Spectra-Mat. Section II describes the handling and installation of the cathode. Section III is a narrative of the activation based on information located in the Control Room Log Book supplemented with time plots of pertinent operating parameters. Activation of the cathode was performed in accordance with the procedure listed in Appendix A. The following sections provide more details on the total pressure and constituent partial pressures in the vacuum vessel, cathode heater power/filament current, and cathode temperature.
Date: May 26, 2006
Creator: Kwan, Joe; Ekdahl, C.; Harrison, J.; Kwan, J.; Leitner, M.; McCruistian, T. et al.
Partner: UNT Libraries Government Documents Department


Description: The NDCX-II accelerator for target heating experiments has been designed to use a large diameter ({approx_equal} 10.9 cm) Li{sup +} doped alumino-silicate source with a pulse duration of 0.5 {micro}s, and beam current of {approx_equal} 93 mA. Characterization of a prototype lithium alumino-silicate sources is presented. Using 6.35mm diameter prototype emitters (coated on a {approx_equal} 75% porous tungsten substrate), at a temperature of {approx_equal} 1275 C, a space-charge limited Li{sup +} beam current density of {approx_equal} 1 mA/cm{sup 2} was measured. At higher extraction voltage, the source is emission limited at around {approx_equal} 1.5 mA/cm{sup 2}, weakly dependent on the applied voltage. The lifetime of the ion source is {approx_equal} 50 hours while pulsing the extraction voltage at 2 to 3 times per minute. Measurements show that the life time of the ion source does not depend only on beam current extraction, and lithium loss may be dominated by neutral loss or by evaporation. The life time of a source is around {ge} 10 hours in a DC mode extraction, and the extracted charge is {approx_equal} 75% of the available Li in the sample. It is inferred that pulsed heating may increase the life time of a source.
Date: March 23, 2011
Creator: Roy, Prabir K.; Greenway, Wayne G.; Kwan, Joe W.; Seidl, Peter A. & Waldron, William L.
Partner: UNT Libraries Government Documents Department

Li+ alumino-silicate ion source development for the Neutralized Drift Compression Experiment (NDCX)

Description: We report results on lithium alumino-silicate ion source development in preparation for warmdense-matter heating experiments on the new Neutralized Drift Compression Experiment (NDCXII). The practical limit to the current density for a lithium alumino-silicate source is determined by the maximum operating temperature that the ion source can withstand before running into problems of heat transfer, melting of the alumino-silicate material, and emission lifetime. Using small prototype emitters, at a temperature of ~;;1275 oC, a space-charge-limited Li+ beam current density of J ~;;1 mA/cm2 was obtained. The lifetime of the ion source was ~;;50 hours while pulsing at a rate of 0.033 Hz with a pulse duration of 5-6 mu s.
Date: October 1, 2010
Creator: Roy, Prabir K.; Greenway, Wayne G.; Kwan, Joe W.; Seidl, Peter A.; Waldron, William L. & Wu, James K.
Partner: UNT Libraries Government Documents Department


Description: Successful explosive material detection in luggage and similar sized containers is acritical issue in securing the safety of all airline passengers. Tensor Technology Inc. has recently developed a methodology that will detect explosive compounds with pulsed fast neutron transmission spectroscopy. In this scheme, tritium beams will be used to generate neutrons with a broad energy spectrum as governed by the T(t,2n)4He fission reaction that produces 0-9 MeV neutrons. Lawrence Berkeley National Laboratory (LBNL), in collaboration with Tensor Technology Inc., has designedand fabricated a pulsed white-spectrum neutron source for this application. The specifications of the neutron source are demanding and stringent due to the requirements of high yield and fast pulsing neutron emission, and sealed tube, tritium operation. In a unique co-axial geometry, the ion source uses ten parallel rf induction antennas to externally couple power into a toroidal discharge chamber. There are 20 ion beam extraction slits and 3 concentric electrode rings to shape and accelerate the ion beam into a titanium cone target. Fast neutron pulses are created by using a set ofparallel-plate deflectors switching between +-1500 volts and deflecting the ion beams across a narrow slit. The generator is expected to achieve 5 ns neutron pulses at tritium ion beam energies between 80 - 120 kV. First experiments demonstrated ion source operation and successful beam pulsing.
Date: June 2, 2008
Creator: King, Michael J.; Miller, Gill T.; Reijonen, Jani; Ji, Qing; Andresen, Nord; Gicquel,, Frederic et al.
Partner: UNT Libraries Government Documents Department

What product might a renewal of Heavy IonFusion development offerthat competes with methane microbes and hydrogen HTGRs

Description: In 1994 a Fusion Technology journal publication by Logan, Moir and Hoffman described how exploiting unusually-strong economy-of-scale for large (8 GWe-scale) multi-unit HIF plants sharing a driver and target factory among several low cost molten salt fusion chambers {at} < $40M per 2.4 GW fusion each (Fig. 1), could produce electricity below 3 cts/kWehr, even lower than similar multi-unit fission plants. The fusion electric plant could cost $12.5 B for 7.5 GWe and produce hydrogen fuel by electrolysis at prices competitive with gasoline-powered hybrids getting fuel from oil at $20$/bbl. At $60/bbl oil, the fusion plant can cost $35B and compete {at} 10% APR financing. Given massive and still-increasing world demand for transportation fuel even with oil climbing above $60/bbl, large HIF plants producing both low cost electricity and hydrogen could be more relevant to motivate new R&D funding for HIF development in the next few years. Three major challenges to get there: (1) NIF ignition in indirect drive geometry for liquid chambers, (2) a modular accelerator to enable a one-module IRE < $100 M, (3) compatible HIF target, driver and chamber allowing a small driver {at}< $500 M cost for a >100MWe net power DEMO. This scoping study, at a very preliminary conceptual level, attempts to identify how we might meet the last two great challenges taking advantage of several recent ideas and advances which motivate reconsideration of modular HIF drivers: >60X longitudinal compression of neutralized ion beams using a variable waveform induction module in NDCX down to 2 nanosecond bunches, the proof-of-principle demonstration of fast optical-gated solid state SiC switches by George Caporaso's group at LLNL (see George's RPIA06 paper), and recent work by Ed Lee, John Barnard and Hong Qin on methods for time-dependent correction of chromatic focusing errors in neutralized beams with up to 10 % ...
Date: April 19, 2006
Creator: Logan, Grant; Lee, Ed; Yu, Simon; Briggs, Dick; Barnard, John; Friedman, Alex et al.
Partner: UNT Libraries Government Documents Department

Beam Energy Scaling on Ion-Induced Electron Yield from K+ Impacton Stainless Steel

Description: Electron clouds limit the performance of many major accelerators. Significant quantities of electrons result when halo ions are lost to beam tubes, generating gas which can be ionized and ion-induced electrons that can multiply and accumulate, causing degradation or loss of the ion beam. In order to understand the physical mechanisms of ion-induced electron production, experiments studied the impact of 50 to 400 keV K{sup +} ions on stainless steel surfaces near grazing incidence, using the 500 kilovolts Ion Source Test Stand (STS-500) at LLNL. The experimental electron yield scales with the electronic component (dE{sub e}/dx) of the stopping power. A theoretical model is developed, using TRIM code to evaluate dE{sub e}/dx at several depths in the target, to estimate the electron yield, which is compared with the experimental results.
Date: January 1, 2006
Creator: Kireeff Covo, Michel; Molvik, Arthur; Friedman, Alex; Westenskow,Glen; Barnard, John J.; Cohen, Ronald et al.
Partner: UNT Libraries Government Documents Department

Research Opportunities in High Energy Density Laboratory Plasmas on the NDCX-II Facility

Description: Intense beams of heavy ions offer a very attractive tool for fundamental research in high energy density physics and inertial fusion energy science. These applications build on the significant recent advances in the generation, compression and focusing of intense heavy ion beams in the presence of a neutralizing background plasma. Such beams can provide uniform volumetric heating of the target during a time-scale shorter than the hydrodynamic response time, thereby enabling a significant suite of experiments that will elucidate the underlying physics of dense, strongly-coupled plasma states, which have been heretofore poorly understood and inadequately diagnosed, particularly in the warm dense matter regime. The innovations, fundamental knowledge, and experimental capabilities developed in this basic research program is also expected to provide new research opportunities to study the physics of directly-driven ion targets, which can dramatically reduce the size of heavy ion beam drivers for inertial fusion energy applications. Experiments examining the behavior of thin target foils heated to the warm dense matter regime began at the Lawrence Berkeley National Laboratory in 2008, using the Neutralized Drift Compression Experiment - I (NDCX-I) facility, and its associated target chamber and diagnostics. The upgrade of this facility, called NDCX-II, will enable an exciting set of scientific experiments that require highly uniform heating of the target, using Li{sup +} ions which enter the target with kinetic energy in the range of 3 MeV, slightly above the Bragg peak for energy deposition, and exit with energies slightly below the Bragg peak. This document briefly summarizes the wide range of fundamental scientific experiments that can be carried out on the NDCX-II facility, pertaining to the two charges presented to the 2008 Fusion Energy Science Advisory Committee (FESAC) panel on High Energy Density Laboratory Plasmas (HEDLP). These charges include: (1) Identify the compelling scientific opportunities for research ...
Date: March 23, 2009
Creator: Barnard, John; Cohen, Ron; Friedman, Alex; Grote, Dave; Lund, Steven; Sharp, Bill et al.
Partner: UNT Libraries Government Documents Department