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The Heavy Ion Fusion Accelerator Research Group at LBNL is completing the re-design of the LBNL 2-MV ESQ Injector that will deliver at least 500 mA of singly-charged potassium ion beam at 2 MV for the High Current Transport Experiment (HCX). The LBNL 2-MV ESQ Injector, built and operated since 1993, has produced a potassium beam with adequate current (0.8 A) and emittance (0.8 pi-mm-mr normalized) but with a hollow profile at the exit of the injector. This driver-scale injector consists of a 750 keV diode pre-injector followed by an electrostatic quadrupole accelerator (ESQ) which provides strong (alternating gradient) focusing for the space-charge dominated beam and simultaneously accelerates the ions to 2 MeV. A matching section is required to give the beam emerging from the injector the proper shape to match the downstream HCX lattice. We will present the required modifications to the diode geometry and ESQ focussing strengths that will reduce the beam nonuniformity at the end of the injector. We will also present numerical simulations that show the evolution of the beam in the injector, through the matching section, as well as it is transported in the HCX.

Cover page: Ion beam injector for the High Current Transport Experiment (HCX)

Article

Beam Stability and Control in Solenoidal Transport Channels

Lund, S.M.

LBL Publications (2009)

Cover page: Beam Stability and Control in Solenoidal Transport Channels

Article

Space-charge transport limits of ion beams in periodic quadrupole focusing channels

LBL Publications (2006)

Article

The high current experiment: First results

Lawrence Berkeley National Laboratory (2002)

Article

Stray-electron accumulation and effects in HIF accelerators

LBL Publications (2003)

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 secondary-electron emission. Electron accumulation is impacted by the ion beam potential, accelerating fields, multipole magnetic fields used for beam focus, and the pulse duration. We highlight the distinguishing features of heavy-ion accelerators as they relate to stray-electron issues, and present first results from a sequence of simulations to characterize the electron cloud that follows from realistic ion distributions. Also, we present ion simulations with prescribed random electron distributions, under taken to begin to quantify the effects of electrons on ion beam quality.