The Heavy Ion Fusion Science Virtual National Laboratory (HIFS-VNL), a collaboration of LBNL, LLNL, and PPPL, has achieved 60-fold pulse compression of ion beams on the Neutralized Drift Compression eXperiment (NDCX) at LBNL. In NDCX, a ramped voltage pulse from an induction cell imparts a velocity "tilt" to the beam; the beam's tail then catches up with its head in a plasma environment that provides neutralization. The HIFS-VNL's mission is to carry out studies of Warm Dense Matter (WDM) physics using ion beams as the energy source; an emerging thrust is basic target physics for heavy ion-driven Inertial Fusion Energy (IFE). These goals require an improved platform, labeled NDCX-II. Development of NDCX-II at modest cost was recently enabled by the availability of induction cells and associated hardware from the decommissioned Advanced Test Accelerator (ATA) facility at LLNL. Our initial physics design concept accelerates a ∼30 nC pulse of Li + ions to ∼3 MeV, then compresses it to ∼1 ns while focusing it onto a mm-scale spot. It uses the ATA cells themselves (with waveforms shaped by passive circuits) to impart the final velocity tilt; smart pulsers provide small corrections. The ATA accelerated electrons; acceleration of non-relativistic ions involves more complex beam dynamics both transversely and longitudinally. We are using analysis, an interactive one-dimensional kinetic simulation model, and multidimensional Warp-code simulations to develop the NDCX-II accelerator section. Both LSP and Warp codes are being applied to the beam dynamics in the neutralized drift and final focus regions, and the plasma injection process. The status of this effort is described.

During the past two years, significant experimental and theoretical progress has been made in the U.S. heavy ion fusion science program in longitudinal beam compression, ion-beam-driven warm dense matter, beam acceleration, high brightness beam transport, and advanced theory and numerical simulations. Innovations in longitudinal compression of intense ion beams by > 50 X propagating through background plasma enable initial beam target experiments in warm dense matter to begin within the next two years. We are assessing how these new techniques might apply to heavy ion fusion drivers for inertial fusion energy. IntroductionA coordinated heavy ion fusion science program by the Lawrence Berkeley National Laboratory, Lawrence Livermore National Laboratory, and Princeton Plasma Physics Laboratory (the HeavyIon Fusion Science Virtual National Laboratory), together with collaborators at Voss Scientific and Sandia National Laboratories, pursues research on compressing heavy ion beams towards the high intensities required for creating high energy density matter and fusion energy. In previous research, experiments [1] and simulations [2] showed >100X increases in focused beam intensities in the Neutralized Transport Experiment by transverse compression of an intense ion beam propagating through a background plasma to neutralize >90% of the beam space charge. Section 2 describes recent work on longitudinal compression of an intense beam within neutralizing plasma, and in Sec. 3 we describe studies of initial warm dense matter target experiments that can begin in 2008 after transverse and longitudinal beam compression are combined. Progress in testing a novel Pulse Line Ion Accelerator (PLIA) is described in Sec. 4, e-cloud experiments, theory and simulations in Sec 5, advanced injectors in Sec 6, and advanced theory and simulation models in Sec 7. Section 8 discusses potential applications to heavy ion fusion drivers, and conclusions are given in Sec. 9.

One approach for heating a target to "Warm Dense Matter" conditions (similar, for example, to the interiors of giant planets or certain stages in inertial confinement fusion targets), is to use intense ion beams as the heating source (see refs.[6] and [7] and references therein for motivation and accelerator concepts). By consideration of ion beam phase-space constraints, both at the injector, and at the final focus, and consideration of simple equations of state and relations for ion stopping, approximate conditions at the target foil may be calculated. Thus, target temperature and pressure may be calculated as a function of ion mass, ion energy, pulse duration, velocity tilt, and other accelerator parameters. We connect some of these basic parameters to help search the extensive parameter space (including ion mass, ion energy, total charge in beam pulse, beam emittance, target thickness and density. ION STOPPINGWe first examine dE/dX, where E is the ion energy and X ≡ ∫ ρ dz is the integrated range of the ion (cf, ref.[1]).For heating solid aluminum (at room temperature) over a range of ion mass from 4 amu (helium) to 126 amu (iodine), the energy loss at the peak of the dE/dX curve (dE/dX max ) may be parameterized approximately as:( Target uniformity is another important consideration. In ref.[2] it was pointed out that target temperature uniformity can be maximized in simple planar targets if the particle energy reaches the maximum in the energy loss rate dE/dX when the particle has reached the center of the foil (see Figure 1). For any specified fractional deviation in target temperature (assuming the energy is deposited in a time short so that no hydrodynamic, radiative, or other cooling has occurred) one can determine the energy at which the ion must enter and exit the foil. From the dE/dX curves of ref.[1] we find that for the entrance energy to have less than a 5% lower energy loss rate relative to the peak in d E / d X , ΔΕ/Ε <≈ 1.0, where Δ E is the difference in ion energy between entering and exiting the foil, and E is the energy at which dE/dX is maximum. The spatial width of the foil Z, for a 5% temperature non-uniformity is then given by:

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