摘要:

We recently reported the H0density and temperature in the 4X source (a Penning SPS) as a function of the H2gas flow and the discharge current, as well as a measurement of the H2(v=1) vibrational state density. In this paper, we report the H0density and temperature in the 4X source as a function of magnetic field for the same source geometry of the previous report and as a function of H2gas flow and discharge current for a smaller discharge chamber. When the smaller discharge chamber is used, the plasma column H0density increases from 7×1014cm−3to 8×1014cm−3and the plasma column H0temperature increases from 1.5 to 1.9 eV.

ISSN:0094-243X    

DOI:10.1063/1.39621

出版商:AIP    

年代:1990

数据来源: AIP

摘要:

A new diagnostic method to measure transport properties of negative Hydrogen ions has been devised. It uses multi‐point, multi‐time laser pulse photodetachment of H−, inducing changes in the electron and ion densities, whose space and time evolution are traced in detail by laser pulses and probes. A kinetic analysis of plasma an self‐consistent field evolution in space‐time, following localized photodetachment of H−, is presented. The fit of measurements to analysis is used to infer H−temperatures.

ISSN:0094-243X    

DOI:10.1063/1.39622

出版商:AIP    

年代:1990

数据来源: AIP

摘要:

The H−negative ion thermal energy measured using the two laser‐pulse photodetachment technique is reported to be in the range from 0.1 to 0.7 eV for various conditions of volume ion source operation (pressure–from 2 to 7 mTorr, discharge current–from 1.5 to 20 A). The hydrogen pressure has a significant effect in lowering the negative ion temperature, while the increase of the discharge current leads to a raise in T−. It is found that T−represents a fraction of the electron temperature,Te, which is approximately independent of the discharge current, but strongly depends on the gas pressure. T−scales linearly with the electron temperature and exceeds the highest values predicted by the theory of dissociative attachment for T−at formation. The possible mechanisms for H−heating are discussed.

ISSN:0094-243X    

DOI:10.1063/1.39623

出版商:AIP    

年代:1990

数据来源: AIP

摘要:

The Balmer &bgr; and &ggr; line shapes have been analyzed to determine the relative density and the temperature of hydrogen atoms in magnetic multicusp plasma generators. Results for a 90 V, 4–40 mTorr, 1–18 A conventional multicusp plasma generator and a 50 V, 4 mTorr, 1–15 A hybrid multicusp plasma generator are presented. The relative number density of hydrogen atoms increases smoothly with pressure and discharge current but never exceeds 10%. The absolute atomic number density in a 90 V–10 A discharge varies in proportion with pressure. The atomic temperature (in the 0.1–0.4 eV range) decreases with pressure and slowly increases with the discharge current. The role of atoms in the processes determining the H−temperature and the H2vibrational and rotational temperatures is discussed. The results confirm that in multicusp negative ion sources collisional excitation of ground‐state atoms and molecules by energetic electrons is the dominant process in Balmer &bgr; and &ggr; light emission.

ISSN:0094-243X    

DOI:10.1063/1.39625

出版商:AIP    

年代:1990

数据来源: AIP

摘要:

Mass spectrometry has been used for the detection of positive and negative ions in a multicusp ion source operating with both hydrogen and deuterium gas. The mass spectrometer operation has been optimized and it is shown that applying ion extraction voltages can disturb the discharge. Using this technique combined with a Langmuir probe technique we are able to study the positive ionic fractions present when operating with both gases (and the negative ion densities.)

ISSN:0094-243X    

DOI:10.1063/1.39626

出版商:AIP    

年代:1990

数据来源: AIP

摘要:

A current of 30 mA has been extracted from a volume production H−source having a toroidal discharge chamber and rotational symmetry. This is a current density of 30 mA/cm2. The emittance measurement gave a normalized, 90% value of &egr;N(90%)=0.32 &pgr; mm‐mrad for a 13 mA beam. The ion temperature is estimated to be 0.57 eV for this case. For 25.5 mA, &egr;N(90%)=1.1 &pgr; mm‐mrad was measured, but the true value is most likely smaller due to a limitation in the emittance resolution.

ISSN:0094-243X    

DOI:10.1063/1.39627

出版商:AIP    

年代:1990

数据来源: AIP

摘要:

A technique is described which utilizes the electrons stripped off fast neutral atoms and negative ions to monitor beam profiles with sub‐micron position accuracy and with 1500 GHz bandwidth.

ISSN:0094-243X    

DOI:10.1063/1.39628

出版商:AIP    

年代:1990

数据来源: AIP

摘要:

Nonlinear emittance growth produced by ion extraction is considered by a 3‐D analysis in a Vlasov‐Poisson‐Boltzmann formulation. Phenomena considered include: (1), presheath effects, including electron depletion, (2), electron sheath accumulation (for large transverse magnetic fields), (3), nonlinear sheath fields (obtained by a self‐consistent solution with an assumed quasi‐equilibrium positive ion distribution and at least one Vlasov distribution), (4), nonlinear fringe fields produced by the accelerator‐extractor itself (obtained self‐consistently with item 3 above, (5), nonlinear space charge of the beam itself, (6), beam in conjunction with extracted electrons, and (7), ion acoustic waves. For specific volume negative ion source configurations, an investigation of the contribution of aberrations caused by an electron trap and electron accumulation in the extraction sheath are studied. Either of these effects can contribute significantly to the beam emittance, possibly dominating the contribution of the negative ion temperature in the source.

ISSN:0094-243X    

DOI:10.1063/1.39629

出版商:AIP    

年代:1990

数据来源: AIP

摘要:

Two negative ion sources for which H2(v‘) vibrational spectra have been reported are studied with a numerical model. The model gives reasonably good agreement with available experimental measurements, with the notable exception of the vibrational spectra. There are significant quantitative differences at the higherv‘levels, but also some intriguing qualitative similarities.A scaling study of high power sources is also reported. Gas dissociation and possibly vibrational cooling by thermal electrons appear to explain the saturation and in negative ion production with increasing input power. The surface‐to‐volume ratio becomes an important parameter for high power sources, since it affects the atomic recombination rate and the plasma density.

ISSN:0094-243X    

DOI:10.1063/1.39630

出版商:AIP    

年代:1990

数据来源: AIP

摘要:

From approximations based on Hiske’s theories of Tandem‐Volume Sources, expressions are derived for the H−currents obtained from JAERI’s 1 and 5 A sources, and estimates made of the temperature of the neutral gas molecules in the source.The calculated currents, normalized with respect to their maxima at optimum source pressures, are compared with data extrapolated from JAERI’s graphs, showing H−ion currents vs. source pressures at several discharge currents. At pressures less than or equal to optimum, the observed and calculated currents are very close.

ISSN:0094-243X    

DOI:10.1063/1.39631

出版商:AIP    

年代:1990

数据来源: AIP