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Discusses a study which detailed the measurement of the time evolution of the line charge density and energy at the ends of an initially rectangular ion bench due to the space charge of the bunch. Composition of the SBTE machine; Approximation commonly used in describing a drifting bunch for heavy-ion driven; Limitation in the SBTE setup.

Focuses on a study which investigated the direct current and pulsed magnetic properties of Metglas alloys in the as-cast, box annealed and rewound conditions. Background to the study; Results; Conclusions.

Intense beams of heavy ions are well suited for heating matter to regimes of emerging interest. A new facility, NDCX-II, will enable studies of warm dense matter at ∼1 eV and near-solid density, and of heavy-ion inertial fusion target physics relevant to electric power production. For these applications the beam must deposit its energy rapidly, before the target can expand significantly. To form such pulses, ion beams are temporally compressed in neutralizing plasma; current amplification factors of ∼50–100 are routinely obtained on the Neutralized Drift Compression Experiment (NDCX) at the Lawrence Berkeley National Laboratory. In the NDCX-II physics design, an initial non-neutralized compression renders the pulse short enough that existing high-voltage pulsed power can be employed. This compression is first halted and then reversed by the beam’s longitudinal space-charge field. Downstream induction cells provide acceleration and impose the head-to-tail velocity gradient that leads to the final neutralized compression onto the target. This paper describes the discrete-particle simulation models (one-, two-, and three-dimensional) employed and the space-charge-dominated beam dynamics being realized. [ABSTRACT FROM AUTHOR]

In a heavy ion fusion driver, arrays of superconducting quadrupoles will transport parallel beams through a sequence of induction acceleration cells. The development of such arrays is a unique and challenging task. Since magnetic transport is one of the most expensive subsystems, economy of fabrication is a primary consideration. A compact design is essential to limit the size and cost of induction cores. Special edge coils have to be implemented to adjust the field in outer cells and terminate the magnetic flux. The development of superconducting magnets for both near term experiments and the ultimate driver application is actively pursued by the U.S. Heavy Ion Fusion Program. The main parameters and requirements are discussed, and the R&D status and plans are presented. [ABSTRACT FROM AUTHOR]

A one-tenth-scale version of a final focus subsystem for a heavy-ion-fusion driver has been built and used for experimental tests of concept. By properly scaling the parameters that relate ion energy and mass, current, emittance, and focusing fields, the transverse dynamics of a representative driver final focus have been replicated in a small laboratory beam. Whereas the driver beam parameters considered are 10 GeV Bi[sup +] at 1.25 kA, the scaled experiment used a 95 μA beam of 160 keV Cs[sup +] ions brought to a ballistic focus through a series of six quadrupole magnets. The measured focal spot size was consistent with calculations in the report of the design on which the experiment is based. In a second experimental program, a 400 μA beam was propagated through the focal system and partially neutralized after the last magnet using electrons released from a hot tungsten filament to test the predictions of the benefits of neutralization. The increase in beam current resulted in a corresponding increase in spot radius in the absence of electrons. A reduction of the spot radius and modification of its shape were observed in the presence of neutralizing electrons. © 2002 American Institute of Physics. [ABSTRACT FROM AUTHOR]

This report was prepared by a Working Group at the request of the U.S. Department of Energy, Office of Fusion Energy Sciences in 1997. The report addresses technical opportunities for mutually beneficial collaboration between the United States and other international fusion research programs. A number of outstanding opportunities are discussed. [ABSTRACT FROM AUTHOR]

Focuses on the development of superconducting quadrupole arrays for heavy-ion fusion accelerators. Description of the individual quadrupole cell; Layout of the arrays; Operation using the cryostat concept.

Previous heavy-ion fusion driver system studies suggest that transverse beam combining significantly reduces driver cost. In a combiner, several beams are brought together to a common transport channel which accommodates the increased line charge density. Combining intense beams increases the transverse emittance mainly due to the heating of the beam by space charge forces as the non-uniform original beam configuration becomes more uniform. The combiner itself introduces additional aberrations, which are small for the present design. Those aberrations are due to the reduced available space for the focusing electrodes and reduced clearance from the beamlets to the surrounding electrodes, thereby generating field aberrations and larger image forces. These aberrations can also lead to particle loss. We have studied a particular design of the proposed induction linac system experiment (ILSE) combiner which is a first-order achromat that tolerates a rather large fractional head-to-tail momentum tilt of ± 10%. Using a 2D particle-in-cell code we have found that ≈7% of particles are lost in the combiner. The emittance growth after the combiner is large enough so that the emittance growth due to combiner aberrations is unimportant. The scaled projection to a driver shows the growth is small enough to be tolerated. At present, methods of improving combiner design to reduce particle loss and to minimize emittance growth are being studied. [ABSTRACT FROM AUTHOR]

For many cases of interest in the design of heavy-ion fusion accelerators, the maximum transportable current in a magnetic-quadrupole lattice scales as ( a/L), where a is the useful dynamic aperture and L is the half-lattice period. There are many cost benefits in maximizing the usable aperture which must be balanced against unwanted effects such as possible emittance growth and particle loss from anharmonic fringe fields. We have used two independent simulation codes to model space-charge-dominated beam transport both in an azimuthally pure quadrupole FODO lattice design and in a more conventional design. Our results indicate that careful matching will be necessary to minimize emittance growth and that ( a/L) ratios of 0.2 or larger are possible for particular parameters. [ABSTRACT FROM AUTHOR]

The Heavy-Ion Fusion Accelerator Research Program at Lawrence Berkeley Laboratory has proposed building a 10 MeV induction linac systems experiment, ILSE, to investigate accelerator physics and beam manipulations which are needed or desirable for an induction linac driver. This paper describes the experiments proposed for ILSE: transverse beam combining, drift compression, bending of space-charge-dominated beams, final focus, recirculation, and some studies of beam propagation in the environment of the reactor chamber. [ABSTRACT FROM AUTHOR]

A two-year study of recirculating induction heavy-ion accelerators (recirculators) as low-cost drivers for inertial-fusion energy power plants has recently been completed. A summary of that study and other recent work on recirculators is presented. [ABSTRACT FROM AUTHOR]

A 2 MV, 800 mA, K injector for heavy-ion fusion studies is under construction. This new injector is a one-beam version of the proposed 4-beam ILSE injector. A new 36-module MARX is being built to achieve a 5 μs flat top. The high-voltage generator is stiff (<5 kω) to minimize effects of beam-induced transients. A large (≈7" diameters) curved hot alumino-silicate source emits a 1 μs long beam pulse through a gridless extraction electrode, and the ions are accelerated to 1 MV in a diode configuration. Acceleration to 2 MV takes place in a set of electrostatic quadrupole (ESQ) units, arranged to simultaneously focus and accelerate the ion beam. Heavy shields and other protection devices have been built in to minimize risks of high-voltage breakdown. Beam aberration effects through the ESQ have been studied extensively with theory, simulations, and scaled experiments. The design, simulations, experiments, and engineering of the ESQ injector will be presented. [ABSTRACT FROM AUTHOR]

Discusses amplification experiments conducted on a single beam of the Multiple Beam Experiment, a heavy-ion (Cessium ion) induction linac. Factors responsible for the growth of normalized transverse emittance; Measurement of current amplification and line charge density; Modeling of beam current and energy measurements.

Two series of compounds with sodium β- and β″-alumina structure have been studied in which the aluminium is partly replaced by gallium. The level of substitution has been varied from x(Ga/Ga+Al)=0.3 to 0.8. The approximately quantitative analysis of aluminium and gallium NMR of these aluminogallates has allowed us to determine a gallium site occupancy for the different values of x. For sodium, several sites have been shown and a correlation between gallium substitution and sodium positioning has been proposed. The structures are affected by the changes in cation size from aluminium to gallium. The sites occupancy has been determined and allows one to understand the distortions, due to gallium insertion, in the structures. [ABSTRACT FROM AUTHOR]

A two-year study of recirculating induction heavy ion accelerators as low-cost driver for inertial-fusion energy applications was recently completed. The projected cost of a 4 MJ accelerator was estimated to be about $500 M (million) and the efficiency was estimated to be 35%. The principal technology issues include energy recovery of the ramped dipole magnets, which is achieved through use of ringing inductive/capacitive circuits, and high repetition rates of the induction cell pulsers, which is accomplished through arrays of field effect transistor (FET) switches. Principal physics issues identified include minimization of particle loss from interactions with the background gas, and more demanding emittance growth and centroid control requirements associated with the propagation of space-charge-dominated beams around bends and over large path lengths. In addition, instabilities such as the longitudinal resistive instability, beam-breakup instability and betatron-orbit instability were found to be controllable with careful design. [ABSTRACT FROM AUTHOR]