Extraction of H− beams from a magnetically filtered multicusp source

Abstract

H− ions produced by volume processes have been extracted from a multicusp source operated with a magnetic filter and accelerated to form a high-quality beam. It was found that the H− beam current increased almost linearly with the discharge current. An H− ion current density of 38 mA/cm2 was obtained with a discharge current of approximately 350 A. The accelerated beam was mass analyzed and the emittance of the H− component was measured. The electron component and the percentage of ion impurity in the extracted beam were also determined.

Enhancement of extracted H− current by streaming neutral gas injection

“…Subsequently, H À is produced by dissociative electron attachment to rotationally/vibrationally excited H 2 as shown in Eq. (2). In the ion source chamber, it is advantageous to separate the plasma into two different regions of high and low electron temperature regions to enhance H À production.…”

“…In applications where a high-brightness beam of H À is required, the volume production process is preferred since the generated ion beam has been found to have lower emittance [2]. In the volume production process, H À is produced by a twostep process [3,4]:…”

Factors Affecting VUV Emission Spectrum near Lyman-α from a Hydrogen Plasma Source

“…As the produced H -can be easily destroyed by e f , the region where H 2v * are produced is geometrically separated from the region where H -are produced and extracted. An ion source plasma is usually separated into these two regions by inducing an external magnetic field [3], which is often called a "magnetic filter field." The region to produce H 2v * is called driver region, and the region to extract H -is called the extraction region.…”

Characteristics of a small multicusp H− source

“…6 Most recently, a small multicusp source has been fabricated and operated successfully to generate volume-produced H-ions. 7 From this new source, H-current densities as high as 240 mA/cm 2 1-IlII1-diam aperture. The increase in H:-output is mainly due to an increase in the source plasma density.…”

“…H-and 0-ions are used to generate efficient neutral beams with energies in excess of 150 keV.1 It has been demonstrated that volume-produced H-ions, extracted from a filter-equipped multicusp source can provide high quality Hbeams with sufficient current density (40 mA/cm 2 ) to be useful for both neutral beam heating of fusion plasmas and accelerator applications. 2 In order to produce this high H-current density, it was necessary to operate the source with a discharge current as high as 350 A.…”