It is shown that the H− current extracted from a magnetically filtered multicusp source can be enhanced by optimizing the extraction chamber length, by employing the proper chamber wall material, by mixing hydrogen with xenon gases in the discharge and by injecting very low energy electrons into the filter and extraction regions. A large improvement in H− yield can be achieved by using a multicusp source with a much reduced plasma volume. In this arrangement, H− current densities as high as 240 mA/cm2 have been obtained from a 1‐mm‐diam extraction aperture.

The development of low frequency (1–2 MHz) rf plasma generators for high power neutral beam applications is summarized. Immersed couplers from one to three turns were used. Acceptable plasma profiles, ≤15% max/min, were obtained in a variety of field-free, magnetic bucket and magnetic filter-bucket sources, with 10×10 or 10×40 cm extraction areas. Hydrogen beam properties were measured with a 7×10 cm accelerator operated at 80 kV. Atomic fraction and power efficiency were at least as high as with arc plasmas in similar chambers. The potential advantages of an rf plasma source are: ease of operation; reliability; and extended service lifetime.

Positive ion based neutral beam development in the US has centered on the long pulse, Advanced Positive Ion Source (APIS). APIS eventually focused on development of 30 second sources for MFTF-B. The Engineering Test was part of competitive testing of the LBL and ORNL long pulse sources carried out for the MFTF-B Project. The test consisted of 500 beam shots with 80 kV, 30 second deuterium, and was carried out on the Neutral Beam Engineering Test Facility (NBETF). This report summarizes the results of LBL testing, in which the LBL APIS demonstrated that it would meet the requirements for MFTF-B 30 second sources. In part as a result of this test, the LBL design was found to be suitable as the baseline for a Common Long Pulse Source design for MFTF-B, TFTR, and Doublet Upgrade.

Electron-capture and electron-loss cross sections are reported for a large number of combinations of projectile species (C, Ar, Fe, Nb, and Pb), target gases (${\mathrm{H}}_{2}$, He, ${\mathrm{N}}_{2}$, Ne, Ar, and Xe), projectile charge states (6+ to 59+), and energies (310 keV/amu to 8.5 MeV/amu). These measured cross sections are compared with published theoretical calculations and scaling rules.

Three experiments are described in which H/sup -/ or D/sup -/ ions have been produced by backscattering from surfaces coated with alkali metals: (1) Backscattering of H/sup -/ and D/sup -/ produced by 0.15- to 4-keV/nucleus H/sub 2//sup +/, H/sub 3//sup +/, D/sub 2//sup +/, and D/sub 3//sup +/ bombarding clean targets of Cs, Rb, K, Na, and Li. For each target, the H/sup -/ and D/sup -/ yields were maximized at incident energies between 300 and 1200 eV/nucleus and always at a lower incident energy for H than for D on a given target. At any given incident energy, both the H/sup -/ and D/sup -/ yields decreased in going from Cs to Li in the order given above. (2) A Mo surface was bombarded by a low-energy flux of H atoms produced in a tungsten furnace. As the surface work function was reduced by evaporating Cs onto the target, a small fraction (10/sup -9/) of the incident hydrogen atoms was observed as backscattered H/sup -/ ions. (3) Surfaces of Mo, W, Pt, Ni, Cu, Re, Ta, and Pd were bombarded by hydrogen ions produced in a discharge. Two classes of H/sup -/ ions were observed when Cs wasmore » added to the discharge - H/sup -/ ions leaving the surface with approximately < 10 eV and H/sup -/ ions leaving the surface with approximately 50 to 100 eV.« less

The Lawrence Berkeley and Livermore Laboratories Neutral Beam Development Group's work proceeds along two lines. The first is required for the near-term applications (e.g., MFTF, TFTR, and DIII), which require injection at energies up to 120 keV, ion currents per module up to 80 A, and pulse lengths greater than or equal to 0.5 s. These systems are based on the acceleration and neutralization of positive ions. The second part of the program is devoted to development for longer-term applications: positive-ion-based systems with 150 to 200-keV/65 to 100-A/10 to 30-s modules and, smewhat later, negative-ion-based systems for injection at 200 keV and higher energies.

in the charge target to form D/sup -/. For a sufficiently thick target, the beam reaches an equilibrium fraction of negative ions. For reasons of efficiency, the target is typically alkali metal vapor; this experiment uses sodium. The beam of negative ions can be accelerated to high (>200 keV) energy, the electrons stripped from the ions, and a high energy neutral beam formed.

Experimental studies of the relative Μ−-meson atomiccapture probabilities in the compounds CuO, Sb2O3, PbO, CuS, Sb2S3, PbS, and in the metallic solutions Ag0.58Li, CuAu0.18 have been made to test the predictions of the « Fermi-TellerZ-law ». In our experiment the capturing atom was identified by decomposing a compound lifetime curve obtained by detecting neutrons from Μ− capture. The measured atomic-capture ratios are: Cu/O = 6.14 ± 0.85, Sb/S = 1.64 ± 0.10, Sb/O = 1.86 ± 0.096, Pb/S = 2.87 ± 0.35, Pb/O = 4.56 ± 0.53, Ag/Li = 11.66 ± 3.39, Cu/S = 1.89 ± 0.18, Au/Cu = 0.34 ± 0.032.

The Triax device is a discharge tube in which a plasma carrying a current is pinched into the form of a cylinder between two concentric copper cylinders, each of which carries part of the return current. Such a geometry has attractive features from the standpoint of stability. An extensive study of the Triax discharge was carried out in which observations with magnetic probes, spectrographs, and efficient neutron detectors were combined with measurements of current and voltage to give much information on the behavior of the plasma. It is clearly established that a well-pinched sheet plasma is formed. Neutrons, up to 2 x 10/sup 5/ per pulse, emerge in a short burst that coincides in time with the sudden appearance of strong light from impurities and also coincides with a peculiar bump in a plot of the voltage across the tube. The nature of the neutron production was not established, aad although certain arguments are presented that make it not inconceivable that it is thermonuclear, a search for a nonthermonuclear origin is continuing. The importance of a suitable auxiliary starting discharge in forming neutron-producing pinches with very high currents is brought out. Advances in the art of switching large currents are described. (auth)