Neutralization of space charge forces using ionized background gas

Abstract

The Tandem Van de Graaff at Brookhaven National Laboratory has delivered pulsed gold beam to the Alternating Gradient Synchrotron (AGS) and AGS Booster since 1992 for relativistic heavy ion physics. There is an ongoing effort to improve the quality and intensity of the negative ion beam delivered to the Tandem from the present Cs sputter sources. Because the beam energy is low (approximately 30 keV) and the current high, there are significant losses due to space charge forces. One of the ways being explored to overcome these losses is to neutralize the space charge forces with ionized background gas. On an ion source test bench, using three different gases (Ar, N2, and Xe), the percentage of current transported from the source to a downstream Faraday cup was increased from 10% to 40% by bleeding in gas. Bleeding in Xe resulted in the best transmission. The time dependence of the neutralization as a function of gas pressure was also observed. This system is presently being transferred to the Negative Ion Injector of the Tandem for use in upcoming heavy ion experiments.

MeV negative ion generation from ultra-intense laser interaction with a water spray

“…18,19 High brightness beams of negative ions are required for high current tandem accelerators, for ion beam microscopy and lithography. 20,21 FIG. 3.…”

Neutralization of the Surface Charge of an Insulated Target under the Interaction of High-Energy Metal Ion Beams

“…In this case, a significant part of the total ion flux directed to the target can be deflected by the electric field of the charged surface. Such losses can be minimized using methods for compensating the surface charge of the target, for example, by flooding with electrons the region of interaction of ions with the target surface [4], the preliminary deposition of a thin conductive coating on this surface, generating plasma near the treated surface [5], and a pressure increase in the region of the ion beam drift space [6]. The last two methods lead to the effect of gas ions on the treated surface from the residual atmosphere of the vacuum chamber, but for certain technological processes, it may be unacceptable.…”

Optimization of surface plasma sources for efficient production of negative ions with high emission current density

“…Negative ion beams are used for injection into tandems, ion lithography, and in cyclotrons. Some of these applications require very high brightness beams [1,2,3]. Hbeams with very high brightness have been produced from pulsed Surface Plasma Sources (SPS) with charge exchange cooling of the ions [4].…”