[en] The effect on H^- production by adding barium to a hydrogen discharge, in a small magnetically filtered multicusp ion source, has been investigated. It is found that the addition of barium can increase the H^- output by a factor of 30. A strong dependence of H^- output on the temperature of the ion source wall has also been observed

[en] Total cross sections are reported for electron transfer and ionization in collisions between protons and the hydrogenic ions Be/sup 3+/, B/sup 4+/, and C/sup 5+/, and results are presented for He⁺ and Li/sup 2+/ in addition to those previously reported. Proton energies relative to the target ion are in the range 17.5--150 keV for He⁺ targets, increasing with the target's nuclear charge to 150--600 keV for C/sup 5+/ targets. Within these energy ranges the electron-transfer cross sections reach their peak values, and the ionization cross sections approach peak values from below. A coupled-Sturmian-pseudostate approach has been taken, and the largest-basis results are estimated to be converged to within 10% at energies where the electron-transfer cross sections peak. With sufficiently large bases, the cross-section curves vary smoothly and regularly with energy and the target's nuclear charge. Scaling rules for these curves are examined and compared with the simple scaling laws in the Born approximations

[en] A duopigatron ion source is modified by replacing the normal oxide-coated wire filament cathode of the ion source with a hot tungsten oven through which hydrogen gas is fed into the arc chamber. The hydrogen gas is predissociated in the hot oven prior to the arc discharge, and the recombination rate is minimized by hot walls inside of the arc chamber. With the use of the above modifications, the atomic H₁ + ion fraction output can be increased from the normal 50% to greater than 70% with a corresponding decrease in the H₂ + and H₃ + molecular ion fraction outputs from the ion source

[en] Much of the interest in charge transfer and ionization in collisions between positive ions stems from their relevance to controlled thermonuclear fusion research. In the past decade ion beam probing has been demonstrated to be a versatile technique for measuring plasma density, space potential and particle temperature in high energy, magnetically confined plasma. A monoenergetic beam of heavy singly charged ions is incident on the plasma. Ions which undergo charge changing collisions with the plasma particles will emerge from the plasma with an increase in energy proportional to the space potential at the point of collision. The number of multiply charged ions emerging is proportional to the cross sections for the charge changing processes and the density of target particles. All the experiments discussed in this chapter have been carried out using the intersecting beams method and only an outline of the general experimental approach will be given. Collisions looked at are as follows: (1) collisions involving protons; (2) collisions between helium ions; and (3) collisions between heavy ions. 88 references, 22 figures, 1 table

No abstract available

No abstract available

[en] A compact 2.45 GHz electron cyclotron resonance ion source (ECRIS) for high beam current of single charge state has been built at Institute of Modern Physics. A mixed ion (H₁⁺ + H₂⁺ + H₃⁺) beam current of 90 mA is delivered from a single aperture of φ6mm with rf power 600 W at extraction voltage 22 kV. The author introduces the source structure, the magnetic configuration, the test results and the relation between the magnetic configuration and total beam current. In addition, the magnetic configuration is also compared with that of the other 2.45 GHz ECR ion sources built in different laboratories. Finally, some conclusions are presented

[en] Our Penning surface-plasma source (SPS) discharge chamber was enlarged 4X in two dimensions. To date, three pulsed discharge modes have been studied: two with noisy arc (greater than or equal to 20% H^- current fluctuations) and one with quiescent arc (less than or equal to 1% H^- current fluctuations). Lower arc magnetic field and higher H₂ gas flow allow switching from the noisy to the quiescent mode. The noisy modes yield up to 120 mA of 29-keV H^- beam; for 110 mA at 29 keV, the two-dimensional normalized rms emittance is 0.017 x 0.018 π.cm.mrad. The quiescent mode yields 75 mA of 29-keV H^-beam; for 67 mA at 24 keV, the emittance is 0.011 x 0.012 π.cm.mrad

[en] High-resolution dissociative recombination rate coefficients of rotationally cool and hot H₃⁺ in the vibrational ground state have been measured with a 22-pole trap setup and a Penning ion source, respectively, at the ion storage-ring TSR. The experimental results are compared with theoretical calculations to explore the dependence of the rate coefficient on ion temperature and to study the contributions of different symmetries to probe the rich predicted resonance spectrum. The kinetic energy release was investigated by fragment imaging to derive internal temperatures of the stored parent ions under differing experimental conditions. A systematic experimental assessment of heating effects is performed which, together with a survey of other recent storage-ring data, suggests that the present rotationally cool rate-coefficient measurement was performed at 380_-130⁺⁵⁰ K and that this is the lowest rotational temperature so far realized in storage-ring rate-coefficient measurements on H₃⁺. This partially supports the theoretical suggestion that temperatures higher than assumed in earlier experiments are the main cause for the large gap between the experimental and the theoretical rate coefficients. For the rotationally hot rate-coefficient measurement a temperature of below 3250 K is derived. From these higher-temperature results it is found that increasing the rotational ion temperature in the calculations cannot fully close the gap between the theoretical and the experimental rate coefficients.

[en] Calculations of the proton ionization cross section of Li¹⁺, C¹⁺, and N¹⁺, done in the plane-wave Born approximation, are compared with recent measurements. Agreement to 25% or better is found above 100 keV. Comparison of the explicit calculations with scaled neutral-atom 2s and 2p subshell cross sections show that the scaled cross sections will underestimate the measurements by a factor of 2