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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+ at 1.25 kA, the scaled experiment used a 95 μA beam of 160 keV Cs+ 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 radi...

Current amplification of heavy-ion beams is an integral feature of the induction linac approach to heavy-ion fusion (HIF). In this paper we report on amplification experiments conducted on a single beam of the Multiple Beam Experiment (MBE-4), a heavy-ion (Cs+) induction linac. Earlier MBE-4 experiments [H. Meuth et al., Nucl. Instrum. Methods Phys. Res. A 278, 153 (1989)] had demonstrated up-to-9× current amplification but had been accompanied by an up-to-2× increase of normalized transverse emittance. Experiments to pinpoint the causes of this emittance growth indicated various factors were responsible, including focusing aberrations and mismatch difficulties between the injector diode and the accelerator transport lattice, a localized quadrupole misalignment problem, and the interaction of transversely large beams with the nonlinear elements of the focusing lattice. Following ameliorative measures, new current amplification experiments, both with and without acceleration, showed that current amplifications of up to 3× and line charge density increases of up to ≈2× could be achieved without increasing the beam’s normalized transverse emittance. Finally, both the transverse beam dynamics, and beam current and energy measurements were accurately modeled by numerical particle-in-cell simulations and longitudinal dynamics codes, respectively.

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.

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 neutraliz...

Mossbauer spectra at 4.2°K were taken with 197Au in several aurous and auric compounds. For each oxidation state a linear correlation was observed between the isomer shift (IS) and the quadrupole splitting (QS). Both the IS and QS varied over wide ranges in both auric and aurous compounds. Neither IS nor QS alone could be used to determine the oxidation state, but together they appear to determine it uniquely. The results for linear aurous and square‐planar auric complexes are interpreted in terms of 6s6p and 5d6s6p2 hybridization, respectively, with varying degrees of ionic character. Attempts to interpret the results quantitatively in terms of the atomic parameters ψ2(O) and 〈r−3〉 were only partially successful: It was not possible to reproduce the large experimental values for 〈r−3〉6p using free atom theory. The nuclear factor was determined as δR / R = + (2.5 ± 0.6) using the simple hybridization model.

This report describes a 20 channel ``stepper'' magnet assembly designed to cause the incoming Bevatron particle beam to scan across the 1.83 m hydrogen bubble chamber in discrete steps. The purpose of this device is to avoid superimposing tracks. Stepping was triggered by an ``events'' counter placed in the beam. The system was built with low voltage, silicon controlled rectifiers. Magnet pulsing was accomplished in two parts, rapid rise of field was produced by a fast circuit and pulse length was maintained by a slow circuit. Cost was approximately $15 000, exclusive of the surplus components.

The time evolution of the line charge density and energy at the ends of an initially rectangular ion bunch due to the space charge of the bunch are measured and found to be in good agreement with a one‐dimensional dynamical theory. The ends erode at the space‐charge wave speed into the bunch, and the end particles move at twice that speed away from the bunch.

Measurements are reported on the dc and pulsed magnetic properties of three MetglasRa) alloys in the as‐cast, box annealed, and rewound conditions. Alloys 2605SC, 2605S‐2 and 2605CO were evaluated for possible use in an induction linear accelerator. It is found that the 2605SC and 2605S‐2 give similar good performance and the 2605CO slightly less good performance in this application in the microsecond pulse‐width region.

A pulsed cesium vapor source for use in ion sources for high‐current heavy‐ion accelerators is described. The source employs a vacuum spark in Cs and its properties are measured with a hot‐filament Cs detector.