A variety of H ion sources are in use at accelerator laboratories around the world. A list of these ion sources includes surface plasma sources with magnetron, Penning and surface converter geometries as well as magnetic-multipole volume sources with and without cesium. Just as varied is the means of igniting and maintaining magnetically confined plasmas. Hot and cold cathodes, radio frequency, and microwave power are all in use, as well as electron tandem source ignition. The extraction systems of accelerator H ion sources are highly specialized utilizing magnetic and electric fields in their low energy beam transport systems to produce direct current, as well as pulsed and/or chopped beams with a variety of time structures. Within this paper, specific ion sources utilized at accelerator laboratories shall be reviewed along with the physics of surface and volume H production in regard to source emittance. Current research trends including aperture modeling, thermal modeling, surface conditioning, and laser diagnostics will also be discussed.
Lifetimes of metastable levels in the ground term of Fe ions within the 3s 2 3p k , kϭ1-5, isoelectronic sequences have been measured. These measurements were performed utilizing ions that were selected by mass to charge ratio while transported from an electron cyclotron resonance ion source to a Kingdon ion trap, where they were captured and then confined for periods of up to 2.1 s. During this storage period, selected emission wavelengths of transitions from metastable levels in the visible or near-ultraviolet spectral regions were isolated using interference filters, and the time-dependent fluorescence intensities were measured using a photomultiplier tube. Measurement precisions on the order of 2% were achieved in favorable cases. The measured lifetimes are ͑Fe X, 3s 2 p 5 2 P 1/2)ϭ13.64Ϯ0.25 ms, ͑Fe XI, 3s 2 3p 4 1 D 2)ϭ9.86Ϯ0.22 ms, ͑Fe XII, 3s 2 3p 3 2 P 3/2)ϭ1.85Ϯ0.24 ms, ͑Fe XII, 3s 2 3p 3 2 P 1/2)ϭ4.38Ϯ0.42 ms, ͑Fe XII, 3s 2 3p 3 2 D 3/2)ϭ20.35 Ϯ1.24 ms, ͑Fe XIII, 3s 2 3p 2 1 D 2)ϭ6.93Ϯ0.18 ms, and ͑Fe XIV, 3s 2 3p 2 P 3/2)ϭ17.52Ϯ0.29 ms. These results are compared with existing and with new theoretical calculations, which have estimated uncertainties on the order of 10-25 %.
The lifetimes of the 1s 2 2s2p 3 P 2 level of Ar XV and 1s 2 2s 2 2p 2 P 3/2 of Ar XIV have been measured using metastable Ar 14ϩ and Ar 13ϩ ions produced by an electron cyclotron resonance ion source, which were subsequently separately captured into a Kingdon ion trap. The lifetime results are ͑Ar XV, 2s2p 3 P 2 ) ϭ13.4(7) ms and ͑Ar XIV,2 p 2 P 3/2 )ϭ9.12(18) ms. Transition rates derived from the measured lifetimes differ significantly from both relativistic and nonrelativistic calculations of the 2s2p 3 P 1 -3 P 2 M 1 transition rate of Ar XV, but are in reasonable agreement with calculations for the 2p 2 P 1/2 -2 P 3/2 M 1 rate of Ar XIV.
In a laboratory study, the lifetimes of the P levels producing the coronal transitions of Fe x and Fe xiv have 2 been measured. The fluorescence from the metastable levels, which were populated when the ions were produced in a source of multiply charged ions, was studied after the selected ions were injected into an electrostatic ion trap. The results are t(Fe x, 3s 3p) ϭ ms and t(Fe xiv, 3s 3p) ϭ ms. The 2 5 2 o 2 2 o P 13.64 ע 0.25 P 17.52 ע 0.29 1/2 3/2 data significantly reduce the uncertainty of the lifetimes when compared with existing theory.
Forbidden transitions from levels with 3P and 1D cores in excited configurations of Cl-like Mn IX and Fe X have been isolated using interference filters. The fluorescence decay lifetimes of ions orbiting in a Kingdon ion trap were measured. New relativistic configuration interaction calculations of relevant level lifetimes, to aid the analysis, based on B-spline basis sets, are also presented. Line identifications and experimental lifetimes are Mn IX ((4)D(7/2)-(4)F(9/2)):363(-3/+7) nm; tau(Mn IX3p(4)(3P)3d (4)F(9/2)) = 210+/-42 ms; tau(Fe X,3p(4)(3P)3d (4)F(9/2)) = 85.7+/-9.2 ms; tau(Fe X,3p(4)(3P)3d (4)F(7/2)) = 93+/-30 ms; and tau(Fe X, 3p(4)(1D)3d (2)G(9/2)) = 17.8+/-3.1 ms.
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