摘要:

This paper presents the results of an experimental investigation of the parameters effecting the quality of theH−beam extracted from a small source employing multicusp confinement and the magnetic filter to enhance theH−production. The source was designed to operate the d.c. mode, to have a long filament lifetime and to provide an intenseH−beam with low emittance. TheH−beam is initially transported about 2 m at 25 keV with a measured 95% space charge neutralization. The experimental results indicate that the small cusp source is ∼4 times brighter than the large one1for arc current less than 25 A. A 7 mAH−beam with a normalized emittance of 0.34 &pgr;mm.mrad at an arc current of 27 A and the voltage of 127 V is obtained.

ISSN:0094-243X    

DOI:10.1063/1.39610

出版商:AIP    

年代:1990

数据来源: AIP

摘要:

In this paper we consider negative ion surface‐plasma sources with small discharge chambers, designed for long continuous operation. Their important features are a discharge with a cold hollow cathode in a magnetic field, spherical cathode surface for a double geometric focusing of negative ions toward a 1 mm diameter extraction hole, and the plasma drift in crossed fields directed toward the spherical part of the cathode. Regimes with a low noise level have been achieved.H−beams with currents up to 2.5 mA have been achieved; for a discharge current of 0.7 A and at a voltage of 100 V. The source life is longer than 100 hours. Source operation with mixtures of hydrogen and ethyl alcohol, water, or ammonia vapors has been studied, and mass spectra of extracted ions measured. Heavy ion beams (O−, OH−, NH−) with currents up to 1 mA have been achieved.

ISSN:0094-243X    

DOI:10.1063/1.39611

出版商:AIP    

年代:1990

数据来源: AIP

摘要:

As early as the 1960’s, an ion source based on reflex‐type discharge was established which was expected to be highly effective in producing negative ions [1,2]. From the first, considerable discrepancies were observed between the source emissive abilities and numerical estimates of the latter; however, in obtaining such estimates, nothing but the reaction of electron dissociative attachment to non‐excited H2molecules was taken into consideration. A further attempt to explain the discrepancy assumed that all of the H−ions generated in the discharge column are collected towards the emission slit [2].In this paper, we present the theoretical and experimental results concerning the source, and discuss the processes of H−production and loss in the light of our most up‐to‐data knowledge [3,4,5].

ISSN:0094-243X    

DOI:10.1063/1.39612

出版商:AIP    

年代:1990

数据来源: AIP

摘要:

For the past four years we have studied the production of negative hydrogen ions in magnetically insulated diodes. We have tried to replicate Russian results in annular and racetrack diodes using passive cathodes. Optically triggered active cathodes have been developed. We have studied negative ion production using either self contained plasma sources or neutral gas puffs with several different gases.

ISSN:0094-243X    

DOI:10.1063/1.39613

出版商:AIP    

年代:1990

数据来源: AIP

摘要:

Polarization at spin‐exchange collisions of an atomic hydrogen beam with optically pumped sodium vapors has been studied in the optically pumped polarized ions source. The dependence of polarization on beam energy and magnetic field has been measured. At a target thickness of 3⋅1014at/cm2proton polarization achieves 30–35%.

ISSN:0094-243X    

DOI:10.1063/1.39614

出版商:AIP    

年代:1990

数据来源: AIP

摘要:

A program to develop a high intensity polarized H−ion beam for injection into the AGS is under way at this laboratory. The approach we are following is essentially the polarization and ionization of a very cold and intense atomic hydrogen beam. This paper reports on the magnetic focusing of the cold atomic hydrogen beam we have produced.

ISSN:0094-243X    

DOI:10.1063/1.39615

出版商:AIP    

年代:1990

数据来源: AIP

摘要:

Negative ion sources based on plasma‐surface interactions (BLAKE ion source) have been developed at KEK for producing negative heavy ions. The first negative heavy ion source (BLAKE‐II) was developed by modifying the ordinary negative hydrogen ion source with converter (BLAKE‐I) placed into the plasma. It generates various species of negative heavy ions with intense beam currents. For example, a more than 10 mA Au−ion beam was obtained from the ion source. Recently, the large scaled negative heavy ion source (BLAKE‐III) has been developed and in the preliminary test experiment, more than 100 mA Cu‐ ion beam has been stably obtained with a 10% duty factor in pulsed operation. The BLAKE‐II ion source was attached to the BNL 15 MV and Tsukuba University TANDEM accelerators and large current negative heavy ion beams were successfully accelerated in pulsed mode operation. Also, it was found that the space charge effect should be carefully considered for such a large current acceleration in a tandem accelerator, especially at the injection beam line and low energy end. In order to examine the negative ion formation process fundamentally, negative ion production probability related on sputtered particle velocity was measured and the results showed exponential dependence of the production probability on particle velocity as Norskov and Lindquist’s theory predicted.

ISSN:0094-243X    

DOI:10.1063/1.39616

出版商:AIP    

年代:1990

数据来源: AIP

摘要:

An axial‐geometry, plasma‐sputter, negative ion source, which utilizes multi‐cusp, magnetic‐field, plasma‐confinement techniques, is under design at the Oak Ridge National Laboratory (ORNL). The source is based on the principles of operation used in a recently developed radial‐geometry source which has demonstrated pulsed‐mode peak intensity levels of several mA for a wide spectrum of heavy negative ion species. The pulsed‐mode characteristics of the source are well suited for tandem electrostatic accelerator/synchrotron injection applications. Mechanical design features include provisions for fast interchange of sputter samples, ease of maintenance, direct cooling of the discharge chamber, and the use of easily replaced coaxial LaB6cathodes. Principal features of the source will be described and the results of computational studies of the ion extraction optics will be presented.

ISSN:0094-243X    

DOI:10.1063/1.39618

出版商:AIP    

年代:1990

数据来源: AIP

摘要:

We made a spectroscopic study of the plasma of a high‐current hydrogen‐cesium glow discharge with planotron and Penning electrode geometries. The elemental of charge compositions of the plasma were determined. The dynamics of hydrogen, cesium, and molybdenum spectral lines was investigated at different discharge parameters. The changes in the densities of atomic hydrogen, ionized and atomic cesium were observed, along with the sputtering of the electrodes during the discharge pulse.The H&agr;‐ and H&bgr;‐line contours were measured with high resolution in a single discharge pulse (&bartil;10−3s). We determined the temperature of atomic hydrogen and the density of the plasma. The radiation energy of the plasma was measured within the 400–800 nm spectral range.

ISSN:0094-243X    

DOI:10.1063/1.39619

出版商:AIP    

年代:1990

数据来源: AIP

摘要:

Vacuum ultraviolet laser absorption spectroscopy has been employed to measure the populations and temperatures of ground electronic state H‐atoms and vibrationally‐excited H2molecules in a volume H−ion source. Measurements of both species have been made under a variety of discharge conditions. Vibrational levels tov=8 have been measured, with the vibrational population distribution well described by a temperature of 4150 K.

ISSN:0094-243X    

DOI:10.1063/1.39620

出版商:AIP    

年代:1990

数据来源: AIP