Improving extraction and transport simulations of the superconducting ECR ion source VENUS

Electron Cyclotron Resonance (ECR) ion sources are essential components of heavyion accelerators due to their ability to produce the wide range of ions required by these facilities. The ever-increasing intensity demands have led to remarkable performance improvements of ECR injector systems mainly due to advances in magnet technology as well as an improved understanding of the ECR ion source plasma physics. At the same time, enhanced diagnostics and simulation capabilities have improved the understanding of the injector beam transport properties. However, the initial ion beam distribution at the extraction aperture is still a subject of research. Due to the magnetic confinement necessary to sustain the ECR plasma, the ion density distribution across the extraction aperture is inhomogeneous and charge state dependent. In addition, the ion beam is extracted from a region of high axial magnetic field, which adds a rotational component to the beam, which leads to emittance growth. This paper will focus on the beam properties of ions extracted from ECR ion sources and diagnostics efforts at LBNL to develop a consistent modeling tool for the design of an optimized beam transport system for ECR ion sources. KEYWORDS: Scintillators, scintillation and light emission processes (solid, gas and liquid scintillators); Ion sources (positive ions, negative ions, electron cyclotron resonance (ECR), electron beam (EBIS)); Simulation methods and programs; Beam-line instrumentation (beam position and profile monitors; beam-intensity monitors; bunch length monitors)

Section: Neutralization Level Of the Beamsupporting

confidence: 88%

Ion beam properties for ECR ion source injector systems

Leitner¹,

Winklehner²,

Strohmeier³

2011

“…The neutralization is due to rest gas ionization in the beam line and accumulation of now free electrons around the beam. In a previous work, it was experimentally observed that although the beam is not pulsed, the extracted ion beams are not fully neutralized at pressures of less than 2e-7 mbar in the beam line [14]. Therefore different neutralization levels were tested in the model by scaling the total beam current.…”

Section: Results From Simulationsmentioning

confidence: 99%

Comparison of extraction and beam transport simulations with emittance measurements from the ECR ion source venus

Winklehner¹,

Todd²,

Benitez³

et al. 2010

The versatility of ECR (Electron Cyclotron Resonance) ion sources makes them the injector of choice for many heavy ion accelerators. However, the design of the LEBT (Low Energy Beam Transport) systems for these devices is challenging, because it has to be matched for a wide variety of ions. In addition, due to the magnetic confinement fields, the ion density distribution across the extraction aperture is inhomogeneous and charge state dependent. In addition, the ion beam is extracted from a region of high axial magnetic field, which adds a rotational component to the beam. In this paper the development of a simulation model (in particular the initial conditions at the extraction aperture) for ECR ion source beams is described. Extraction from the plasma and transport through the beam line are then simulated with the particle-in-cell code WARP. Simulations of the multispecies beam containing Uranium ions of charge state 18+ to 42+ and oxygen ions extracted from the VENUS ECR ion source are presented and compared to experimentally obtained emittance values.

“…Their work compared well to measurements of high intensity proton [11] and H + 2 [6] beams, which can be considered highly compensated. However, comparison of simulated and measured emittances as well as measurements of the ion beam potential in the Low Energy Beam Transport (LEBT) lines of Electron Cyclotron Resonance Ion Sources (ECRIS) suggested beams far from fully compensated [12,13]. Hence one of the major assumptions in Gabovich's work no longer holds: quasi-neutrality.…”

Section: Introductionmentioning

confidence: 99%

A space charge compensation model for positive DC ion beams

Winklehner¹,

Leitner²

2015

In this paper, we revisit and extend a formula to predict the compensation of space charge in positive DC ion beams of non-relativistic energy, as they are for example found in the injector beam lines of heavy ion accelerator facilities.The original formula was presented in 1975 by Igor Gabovich et al. and takes into account the de-compensation through Coulomb collisions of the primary beam ions and the compensating electrons. We extend its usability to arbitrary (positive) charge states of the ions and non-quasineutral beams.The resulting formula compares well with measurements using a retarding field analyzer and a multi-species generalization of it was incorporated into beam transport simulations using the particle-in-cell code WARP.