摘要:

An optimized tandem two‐chamber negative‐ion source system is discussed. In the first chamber high energy (E≳20 eV) electron collisions provided for H2vibrational excitation, while in the second chamber negative ions are formed by dissociative attachment. The gas density, electron density, and system scale length are varied as independent parameters. The extracted negative ion current density passes through a maximum as electron and gas densities are varied. This maximum scales inversely with system scale length, R. The optimum extracted current densities occur for electron densities near nR=1013electrons cm−2and for gas densities, N2R, in the range 1014to 1015molecules cm−2. The extracted current densities are sensitive to the atomic concentration in the discharge. The atomic concentration is parametrized by the wall recombination coefficient, &ggr;, and scale length, R. As &ggr; ranges from 0.1 to 1.0 and for system scale length of one centimeter, extracted current densities range from 8.0 to 80. mA cm−2.

ISSN:0094-243X    

DOI:10.1063/1.34439

出版商:AIP    

年代:1984

数据来源: AIP

摘要:

The density of negative hydrogen ions and the plasma characteristics are investigated in several configurations of the multicusp plasma generator. H−destruction in plasma is analyzed and two different destruction regimes are discussed. The decrease in H−density with increasing gas pressure is explained in terms of an increase of the rate of mutual neutralization, due to the reduction of the ion energies when the pressure is increased.

ISSN:0094-243X    

DOI:10.1063/1.34432

出版商:AIP    

年代:1984

数据来源: AIP

摘要:

In this paper, the enhancement of cross sections for dissociative electron attachment to H2resulting from the rotational and/or vibrational excitation of the ground electronic state of the neutral molecule is reviewed. A simple physical picture explains this enhancement. General expressions for approximately calculating the cross sections and rates for attachment to various (v,J) levels of H2are provided.

ISSN:0094-243X    

DOI:10.1063/1.34374

出版商:AIP    

年代:1984

数据来源: AIP

摘要:

This paper describes an investigation of the yield of H−ions and of electrons from a modified magnetic multipole source. The data show a dependence of H−yield on magnetic field structure in the source as well as on normal parameters (gas pressure, arc voltage, etc.), and also relationship to the positive ion density. Under optimum conditions the H−current density can attain a value equal to one‐half of the positive ion current density measured at the extraction plasma.

ISSN:0094-243X    

DOI:10.1063/1.34384

出版商:AIP    

年代:1984

数据来源: AIP

摘要:

This paper discusses the process of polar dissociation of molecules. It is suggested that it can be utilized in the fabrication of a source of negative ions. Laboratory data on the electron impact induced polar dissociation for several molecules are presented.

ISSN:0094-243X    

DOI:10.1063/1.34387

出版商:AIP    

年代:1984

数据来源: AIP

摘要:

H−ions formed by volume processes have been extracted from a multicusp ion source. It is shown that a permanent magnet filter together with a small positive bias voltage on the plasma grid can produce a very significant reduction in electron drain as well as a sizable increase in H−ions available for extraction. A further reduction in electron current is achieved by installing a pair of small magnets at the extraction aperture. An H−ion current density of 38 mA/cm2was obtained with a discharge current of approximately 350 A. Different techniques to increase the H−ion yield have also been investigated.

ISSN:0094-243X    

DOI:10.1063/1.34396

出版商:AIP    

年代:1984

数据来源: AIP

摘要:

Progress on the study of negative ion neutralization accompanied by excitation (NINE) is reviewed. A table of all known theoretical and experimental investigations of the cross section for NINE is presented. Experimental and theoretical techniques are discussed briefly and the main conclusions from previous NINE studies are summarized. Recent experimental results for H− → H(12≤ns30) in Ar and H2over the energy range 10–60 keV are presented.

ISSN:0094-243X    

DOI:10.1063/1.34406

出版商:AIP    

年代:1984

数据来源: AIP

摘要:

A search for H−2, H−3and other metastable negative ion sources is made. (AIP)

ISSN:0094-243X    

DOI:10.1063/1.34407

出版商:AIP    

年代:1984

数据来源: AIP

摘要:

Cluster ions of hydrogen are accelerated by 500 kV on a Cs jet‐target. H−are formed from H2moleculeshaving an energy of the order of 100 eV/atom. The intensity of H−is rather low, most probably due to strong scattering at this low energy. In the interaction of cluster ions with cesiated metal surfaces H−are formed from molecules in the energy range of 3–30 eV/atom.

ISSN:0094-243X    

DOI:10.1063/1.34408

出版商:AIP    

年代:1984

数据来源: AIP

摘要:

The H−ion density is measured by photodetachment in the source and target sections of a tandem multicusp discharge. The extracted negative ion and electron currents are measured separately and compared with the respective densities in the plasma.

ISSN:0094-243X    

DOI:10.1063/1.34409

出版商:AIP    

年代:1984

数据来源: AIP