An Induction Linac Driver For A 0.44 MJ Heavy-Ion Direct Drive Target

The conceptual design of a heavy ion fusion driver system is described, including all major components. Particular issues emerging from this exercise are identified and discussed. The most important conclusion of our study is that due to stringent requirements on ion pulse phase space, we are unable to find a credible accelerator design that meets the requirements of the example target. Either the target design must be modified to accept larger ion ranges and larger focal spot sizes, or we must consider other target options

Estimates of energy fluence at the focal plane in beams undergoing neutralized drift compression

The authors estimate the energy fluence (energy per unit area) at the focal plane of a beam undergoing neutralized drift compression and neutralized solenoidal final focus, as is being carried out in the Neutralized Drift Compression Experiment (NDCX) at LBNL. In these experiments, in order to reach high beam intensity, the beam is compressed longitudinally by ramping the beam velocity (i.e. introducing a velocity tilt) over the course of the pulse, and the beam is transversely focused in a high field solenoid just before the target. To remove the effects of space charge, the beam drifts in a plasma. The tilt introduces chromatic aberrations, with different slices of the original beam having different radii at the focal plane. The fluence can be calculated by summing the contribution from the various slices. They develop analytic formulae for the energy fluence for beams that have current profiles that are initially constant in time. They compare with envelope and particle-in-cell calculations. The expressions derived are useful for predicting how the fluence scales with accelerator and beam parameters

Development of Li+ alumino-silicate ion source

To uniformly heat targets to electron-volt temperatures for the study of warm dense matter, one strategy is to deposit most of the ion energy at the peak of energy loss (dE/dx) with a low (E< 5 MeV) kinetic energy beam and a thin target[1]. Lower mass ions have a peak dE/dx at a lower kinetic energy. To this end, a small lithium (Li+) alumino-silicate source has been fabricated, and its emission limit has been measured. These surface ionization sources are heated to 1000-1150 C where they preferentially emit singly ionized alkali ions. Alumino-silicates sources of K+ and Cs+ have been used extensively in beam experiments, but there are additional challenges for the preparation of high-quality Li+ sources: There are tighter tolerances in preparing and sintering the alumino-silicate to the substrate to produce an emitter that gives uniform ion emission, sufficient current density and low beam emittance. We report on recent measurements ofhigh ( up to 35 mA/cm2) current density from a Li+ source. Ion species identification of possible contaminants is being verified with a Wien (E x B) filter, and via time-of-flight

Critical issues for high-brightness heavy-ion beams -- prioritized

This study group was initiated to consider whether there were any ''show-stopper'' issues with accelerators for heavy-ion warm-dense matter (WDM) and heavy-ion inertial fusion energy (HIF), and to prioritize them. Showstopper issues would appear as limits to beam current; that is, the beam would be well-behaved below the current limit, and significantly degraded in current or emittance if the current limit were exceeded at some region of an accelerator. We identified 14 issues: 1-6 could be addressed in the near term, 7-10 are potentially attractive solutions to performance and cost issues but are not yet fully characterized, 11-12 involve multibeam effects that cannot be more than partially studied in near-term facilities, and 13-14 involve new issues that are present in some novel driver concepts. Comparing the issues with the new experimental, simulation, and theoretical tools that we have developed, it is apparent that our new capabilities provide an opportunity to re-examine and significantly increase our understanding of the number one issue--halo growth and mitigation

The present and future of QCD

This White Paper presents an overview of the current status and future perspective of QCD research, based on the community inputs and scientific conclusions from the 2022 Hot and Cold QCD Town Meeting. We present the progress made in the last decade toward a deep understanding of both the fundamental structure of the sub-atomic matter of nucleon and nucleus in cold QCD, and the hot QCD matter in heavy ion collisions. We identify key questions of QCD research and plausible paths to obtaining answers to those questions in the near future, hence defining priorities of our research over the coming decades