Arthur W Molvik

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Accelerators for heavy-ion inertial fusion energy (HIF) have an economic incentive to fit beam tubes tightly to beams, putting them at risk from electron clouds produced by emission of electrons and gas from walls. Theory and PIC simulations suggest that the electrons will be radially trapped in the ≥1 kV ion-beam potential. We are beginning studies on the(More)
Abstract We present comparisons of the CRANGE code to other well-known codes, SRIM and ASTAR, and to experimental results for ion-material interactions such as energy loss per unit length, ion range, and ion induced electron yield. These ion-material interaction simulations are relevant to the electron cloud effect in heavy ions accelerators for fusion(More)
Clouds of stray electrons are ubiquitous in particle accelerators and frequently limit the performance of storage rings. Earlier measurements of electron energy distribution and flux to the walls provided only a relative electron-cloud density. We have measured electron accumulation using ions expelled by the beam. The ion energy distribution maps the(More)
During heavy-ion operation in several particle accelerators worldwide, dynamic pressure rises of orders of magnitude were triggered by lost beam ions that bombarded the vacuum chamber walls. This ion-induced molecular desorption, observed at CERN, GSI, and BNL, can seriously limit the ion beam lifetime and intensity of the accelerator. From dedicated test(More)
Stray electrons can be introduced in positive-charge accelerators for heavy ion fusion (or other applications) as a result of ionization of ambient gas or gas released from walls due to halo-ion impact, or as a result of secondaryelectron emission. Electron accumulation is impacted by the ion beam potential, accelerating fields, multipole magnetic fields(More)
The Heavy Ion Fusion Group at Lawrence Livermore National Laboratory has for several years been developing the world’s first circular ion induction accelerator designed to transport space charge dominated beams. Currently, the machine extends to 90 degrees, or 10 half-lattice periods(HLP) with induction cores for acceleration placed on every other HLP. Full(More)
We simulate fusion power plant driver efficiency by pulsing small induction cores at 5 Hz (a typical projected power plant repetition rate), with a resistive load in the secondary winding that is scaled to simulate the beam loading for induction acceleration. Starting from a power plant driver design that is based on other constraints, we obtain the core(More)
Modern diagnostic techniques provide detailed information on beam conditions in injector, transport, and final focus experiments in the HIF-VNL. Parameters of interest include beam current, beam energy, transverse and longitudinal distributions, emittance, and space charge neutralization. Imaging techniques, based on kapton films and optical scintillators,(More)