Download or read book Comparison of Experimental Data and 3D Simulations of Ion Beam Neutralization from the Neutralized Transport Experiment written by and published by . This book was released on 2004 with total page 44 pages. Available in PDF, EPUB and Kindle. Book excerpt: The Neutralized Transport Experiment (NTX) at Lawrence Berkeley National Laboratory has been designed to study the final focus and neutralization of high perveance ion beams for applications in heavy ion fusion (HIF) and high energy density physics (HEDP) experiments. Pre-formed plasmas in the last meter before the target of the scaled experiment provide a source of electrons which neutralize the ion current and prevent the space-charge induced spreading of the beam spot. NTX physics issues are discussed and experimental data is analyzed and compared with 3D particle-in-cell simulations. Along with detailed target images, 4D phase-space data of the NTX at the entrance of the neutralization region has been acquired. This data is used to provide a more accurate beam distribution with which to initialize the simulation. Previous treatments have used various idealized beam distributions which lack the detailed features of the experimental ion beam images. Simulation results are compared with NTX experimental measurements for 250 keV K ion beams with dimensionless perveance of 1-7 x 10−4. In both simulation and experiment, the deduced beam charge neutralization is close to the predicted maximum value.
Download or read book Simulations of Ion Beam Neutralization in Support of Theneutralized Transport Experiment written by and published by . This book was released on 2006 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Heavy ion fusion (HIF) requires the acceleration, transport, and focusing of many individual ion beams. Drift compression and beam combining prior to focusing result in [approx]100 individual ion beams with line-charge densities of order 10[sup -5] C/m. A focusing force is applied to the individual ion beams outside of the chamber. For neutralized ballistic chamber transport (NBT), these beams enter the chamber with a large radius (relative to the target spot size) and must overlap inside the chamber at small radius (roughly 3-mm radius) prior to striking the target. The physics of NBT, in particular the feasibility of achieving the required small spot size, is being examined in the Neutralized Transport Experiment (NTX) at Lawrence Berkeley National Laboratory. Interpreted by detailed particle-in-cell simulations of beam neutralization, experimental results are being used to validate theoretical and simulation models for driver scale beam transport. In the NTX experiment, a low-emittance 300-keV, 25-mA K[sup +] beam is focused 1 m downstream into a 4-cm radius pipe containing one or more plasma regions. The beam passes through the first 10-cm-long plasma, produced by an Al plasma arc source, just after the final focus magnet and propagates with the entrained electrons. A second, 10-cm-long plasma (produced with a cyclotron resonance plasma source) is created near focus to simulate the effects of a photo-ionized plasma created by the heated target in a fusion chamber. Given a 0.1-[pi]-mm-mrad beam emittance, two and three-dimensional particle-in-cell (PIC) LSP simulations of the beam neutralization predict a
Download or read book Simulations of Ion Beam Neutralization in Support of Theneutralized Transport Experiment written by D. V. Rose and published by . This book was released on 2003 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Heavy ion fusion (HIF) requires the acceleration, transport, and focusing of many individual ion beams. Drift compression and beam combining prior to focusing result in {approx}100 individual ion beams with line-charge densities of order 10{sup -5} C/m. A focusing force is applied to the individual ion beams outside of the chamber. For neutralized ballistic chamber transport (NBT), these beams enter the chamber with a large radius (relative to the target spot size) and must overlap inside the chamber at small radius (roughly 3-mm radius) prior to striking the target. The physics of NBT, in particular the feasibility of achieving the required small spot size, is being examined in the Neutralized Transport Experiment (NTX) at Lawrence Berkeley National Laboratory. Interpreted by detailed particle-in-cell simulations of beam neutralization, experimental results are being used to validate theoretical and simulation models for driver scale beam transport. In the NTX experiment, a low-emittance 300-keV, 25-mA K{sup +} beam is focused 1 m downstream into a 4-cm radius pipe containing one or more plasma regions. The beam passes through the first 10-cm-long plasma, produced by an Al plasma arc source, just after the final focus magnet and propagates with the entrained electrons. A second, 10-cm-long plasma (produced with a cyclotron resonance plasma source) is created near focus to simulate the effects of a photo-ionized plasma created by the heated target in a fusion chamber. Given a 0.1-{pi}-mm-mrad beam emittance, two and three-dimensional particle-in-cell (PIC) LSP simulations of the beam neutralization predict a
Download or read book Nuclear Fusion written by and published by . This book was released on 2005 with total page 652 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Ion Beam Neutralization Processes for Electric Micropropulsion Applications written by and published by . This book was released on 2003 with total page 12 pages. Available in PDF, EPUB and Kindle. Book excerpt: While it is common knowledge that ion beams are easily neutralized using a variety of means, the precise process of neutralization remains unknown. With the increasing popularity of electric propulsion, and in particular micropropulsion systems, this question is of significant importance. Additionally, it has a bearing on thruster design, space instrument calibration, electrodynamic tethers, and ionospheric research. A review of the present state of knowledge on this topic is presented as well as results from ion beam simulations using 2D and 3D Particle-in-Cell codes. The grid generation methodology, adaptation, charged-particle transport, and field solver methodologies of the 3D code are reviewed. The simulations show electrons moving to neutralize the ion beam from background and neutralizer sources. The simulations show the dependence of neutralization on beam energy and the electron/ion velocity ratio. The results are compared favorably with previous computations and experimental observations.
Download or read book Development of Implicit Kinetic Simulation Methods and Their Application to Ion Beam Propagation in Current and Future Neutralized Drift Compression Experiments written by Stefano Markidis and published by . This book was released on 2010 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Ion beams can be accelerated and focused to hit a target thus releasing high density power to achieve nuclear fusion. They can also be used to study phase transition from the solid to the Warm Dense Matter state. The Neutralized Drift Compression Experiment (NDCX) at the Lawrence Berkeley National Laboratory is being used to investigate the possibility of developing drivers for the heavy ion fusion reactors, and for Warm Dense Matter experiments. Because ion beams are positively charged, repulsive forces act on the beam ions. These electrostatic forces defocus the beam, increasing the beam size and degrading the applied compression and focus. Electrons are introduced via a preformed plasma to eliminate the electrostatic forces that defo- cus the beam in the NDCX. The spread of the background plasma electrons inside the beam, and the adjustment of their velocity to the beam propagation velocity is called neutralization process. Because collisions occur on time scales much larger than the time scales for the neutralization process, the plasma can be considered collision-less. Thus, the neutralization process is dominated by plasma-wave interactions instead of collisions, and the kinetic approach is required to model this phenomenon. In this dissertation, the neutralization process in the NDCX configuration is stud- ied. The collision-less kinetic equations of plasma are solved numerically using two implicit Particle-in-Cell methods. The implicit nature of the time-differenced gov- erning equations leads to unconditional numerical stability. The primary numerical scheme is based on an implicit moment Particle-in-Cell approach. It has been devel- oped for the electromagnetic case and implemented in a 3D, parallel code to study the neutralization process. In addition, a fully implicit Particle-in-Cell method to solve the particle and field equations has been also developed and implemented for a simple one dimensional, electrostatic configuration. The goal of the fully implicit scheme was to demonstrate that a fully implicit scheme can indeed converge as it has been a challenge. It has been demonstrated that fully implicit schemes (at least 1D, electrostatic configuration) can in fact converge. The schemes developed and implemented are used extensively to study the neutralization dynamics. The aim of this study is to analyze the dynamics that governs the neutralization process in the NDCX configuration. It has been found that the neutralization is a transient phenomenon, typically occurring on time scales of tens of plasma periods. During this transient, the ion beam undergoes through large electron oscillations. The oscillations are damped by a sheath. This sheath regulates the electron flux into and out of the beam, and because it opposes the electron oscillations, it also oscillates. The forward moving and oscillating sheath persists after the transient, and forms an oscillating shock at the front of the ion beam. The shock is in the form of a moving and oscillating discontinuity in the electric field, the charge density, and the electron average velocity. It has been found that the background plasma and beam densities influence the neutralization process, changing the properties of the sheath at the beam-plasma interface. The damping of the oscillations is important when the background plasma and beam densities are close in value, while it is weaker when the background plasma density is higher than the beam density. Moreover, the magnetic field does not have a significant effect on the ion beam neutralization process in the current and future NDCX configurations, and the simulations can be carried out in the electrostatic limit, achieving the same results as those obtained using electromagnetic simulations. A comparison of the implicit Particle-in-Cell methods with the explicitly time differenced Particle-in-Cell method shows that the implicit moment and the fully im- plicit Particle-in-Cell methods are on average 4 to 40 times computationally more expensive if the same simulation time step is used. Because the ion beam neutral- ization process in the NDCX occurs on the plasma period time scales and on the Debye length spatial scales, these scales need to be resolved to correctly describe the neutralization phenomenon. Because of these constraints on the time step and the grid spacing, the implicit Particle-in-Cell methods are here used on space and time scales where the explicit Particle-in-Cell method is numerically stable, hence denying the advantage that implicit methods have over explicit schemes. However, it is clear that implicit schemes are more efficient for problems that allow large time steps.
Download or read book Computer Experiments on Ion beam Neutralization with Initially Cold Electrons written by Stanford University. Stanford Electronics Laboratories and published by . This book was released on 1963 with total page 52 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Investigation of Ion Beam Neutralization Processes With 2 D and 3 D PIC Simulations written by and published by . This book was released on 2004 with total page 10 pages. Available in PDF, EPUB and Kindle. Book excerpt: While it is common knowledge that ion beams are easily neutralized for both current and charge density using a variety of means, the precise process of neutralization remains unknown. With the increasing importance of electric propulsion, and in particular micropropulsion systems, this question is of significant importance. Additionally, it has bearing on thruster design, space instrument calibration, electrodynamic tethers, and ionospheric research. A review of the present state of knowledge on this topic is presented as well as results from ion beam simulations using 2D and 3D Particle-in-Cell (PlC) codes. We investigate both the early "filing" problem of the beam starting to move away from the spacecraft and the steady state problem where the beam encounters a wall at an infinite distance from the spacecraft.
Download or read book Neutralized Transport of High Intensity Beams written by and published by . This book was released on 2003 with total page 3 pages. Available in PDF, EPUB and Kindle. Book excerpt: The NTX experiment at the Heavy Ion Fusion Virtual National Laboratory is exploring the performance of neutralized final focus systems for high perveance heavy ion beams. A converging ion beam at the exit of the final focus magnetic system is injected into a neutralized drift section. The neutralization is provided by a metal arc source and an RF plasma source. Effects of a ''plasma plug'', where electrons are extracted from a localized plasma in the upstream end of the drift section, and are then dragged along by the ion potential, as well as the ''volumetric plasma'', where neutralization is provided by the plasma laid down along the ion path, are both studied and their relative effects on the beam spot size are compared. Comparisons with 3-D PIC code predictions will also be presented.
Download or read book Cesium Ion Beam Neutralization in Vehicular Simulation written by J. M. Sellen and published by . This book was released on 1961 with total page 65 pages. Available in PDF, EPUB and Kindle. Book excerpt: A series of experiments are described which relate to the charge neutralization of a broad cesium ion beam under circumstances which simulate the conditions of space. This was accomplished by the use of pulsed beams and by the control of the boundary conditions in such a manner as to reduce to an extremely low level the electric fields between these boundaries and the ejected plasma. The period of ion turn-around was reduced to values below the present limits of measurement (approx. 1 micro-sec). The ejected plasma was found to possess a high degree of overall neutrality. The fraction of ions which were matched by the presence of an electron equaled or exceeded 0.998. The plasma was well neutralized on a point-by-point basis. It was also demonstrated that for fixed ion source perveance the neutralization is independent of the acceleration voltage.
Download or read book Inertial Fusion Sciences and Applications 2005 written by Jean-Claude Gauthier and published by . This book was released on 2006 with total page 1288 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Journal de physique written by and published by . This book was released on 2006 with total page 1310 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Physics Briefs written by and published by . This book was released on 1994 with total page 916 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book New Experiments in Neutralized Ion Beam Spectroscopy written by Gregory I. Gellene and published by . This book was released on 1983 with total page 358 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Transport of a Partially neutralized Ion Beam in a Heavy ion Fusion Reactor Chamber written by and published by . This book was released on 1995 with total page 5 pages. Available in PDF, EPUB and Kindle. Book excerpt: In a heavy-ion driven, inertial confinement fusion power plant, a space-charge dominated beam of heavy ions must be transported through a reactor chamber and focused on a 2-3 mm spot at the target. The spot size at the target is determined by the beam emittance and space charge, plus chromatic aberrations in the focusing lens system and errors in aiming the beam. The gain of the ICF capsule depends on the focal spot size. We are investigating low density, nearly-ballistic transport using an electromagnetic, r-z particle-in-cell code. Even at low density (n (almost equal to) 5 x 1013 cm−3), beam stripping may be important. To offset the effects of stripping and reduce the space charge, the beam is partially charge neutralized via a pre-formed plasma near the chamber entrance. Additional electrons for charge neutralization come from ionization of the background gas by the beam. Simulations have shown that stripping can greatly increase the spot size; however, partial neutralization can offset most of this increase.
Download or read book Generation Transport and Focusing of High brightness Heavy Ion Beams written by Enrique Henestroza and published by . This book was released on 2006 with total page 201 pages. Available in PDF, EPUB and Kindle. Book excerpt: (Cont.) NTX provides the first experimental proof of plasma neutralized ballistic transport of a space-charge dominated ion beam, the information about higher order aberration effects on the spot size, the validation of numerical tools based on excellent agreement between measurements and numerical simulations over a broad parameter regime, and the development of new diagnostics to study the ion beam dynamics. The theoretical and experimental results are presented on the beam dynamics in the ion diode, downstream quadrupole lattice, and final neutralized transport.
Download or read book Production and Neutralization of Negative Ion Beams written by Ady Hershcovitch and published by American Institute of Physics. This book was released on 1990 with total page 848 pages. Available in PDF, EPUB and Kindle. Book excerpt:
