A multi-sample Cs-sputter negative-ion source

Abstract

A multi-sample Cs sputter negative-ion source, equipped with a conical-geometry, W-surfaceionizer has been designed and fabricated that permits sample changes without disruption of on-line accelerator operation.Sample changing is effected by actuating an electro-pneumatic control system located at ground potential that drives an air-motor-driven sample-indexing-system mounted at high voltage; this arrangement avoids complications associated with indexing mechanisms that rely on electronic power-supplies located at high potential. In-beam targets are identified by LED indicator lights derived from a fiber-optic, Gray-code target-position sensor. Aspects of the overai 1 source design and details of the indexing mechanism along with operational parameters, ion optics.intensities, and typical emittances for a variety of negative-ion species will be presented in this Negative-ion sources based on the sputter principle have been used for many years for injection into tandem electrostatic accelerators for fimdamental nuclear and astrophysics research applications, and for applied research such as Accelerator Mass Spectrometry (AMS), high-energy ion implantation and modification of materials. In addition, these sources are being used in a variety of low-energy, atomic and molecular physics research applications. As a consequence of these and other demands for sources with improved intensities and beam qualities, this technology has reached a relatively high degree of maturity. Several sources, designed to accommodate single samples, have been developed over the years, including those described in Refs. 1 and 2. For applications that require short-duration beam-on-target, including AMS, it is desirable to be able to quickly and remotely change samples without vacuum disruption to save time and to preserve similar surface conditions between samples. A few sources have been reported that have been designed with this capability, including sources described in Refs, 3-5. In this report, we describe a multi-sample Cs sputter negative-ion source, equipped with a conical-geometry, surface ionizer that permits sample changes without disrupt ion of online accelerator operation. Aspects of the overall source design and details of the indexing mechanism along with operational parameters, ion optics, intensities and emittances for a wide variety of negative ion species are provided in this report.

Production of negatively charged radioactive ion beams

“…In fact, the batch-mode technique is one of the early approaches for producing negative ion beams of isotopes with lifetimes longer than a few hours [46][47][48][49][50][51]. A multi-sample Cs-sputter ion source was developed at HRIBF for batch-mode generation of RIBs of long-lived isotopes [52,53]. Chemically active radioactive species are often released from target materials in a variety of molecular forms, for example, fluorine isotopes were found to be released from Al 2 O 3 production targets primarily as AlF.…”

“…Either way, this technique avoids the high target temperatures required for fast diffusion and fast effusive-flow to the ion source. Two Cs-sputter ion sources have been designed and evaluated at HRIBF for this application: a batch-mode Cs-sputter source and a multi-sample Cs-sputter source [52,53]. As illustrated in figure 11, both are based on the previously developed single-sample Cs-sputter sources [75] with a conical geometry, W-surface ionizer for surface ionization of Cs atoms and similar ion optics for accelerating Cs + ions and extracting negative ions.…”