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The exact equations of a radio frequency (rf) sheath driven by rf-biased voltage are solved numerically. All of the sheath characteristics for an arbitrary rf frequency are obtained, including the time-dependent ion density distributions, the ion current density, and ion kinetic energy at the electrode. Moreover, the ion energy distributions (IEDs) impinging on the rf-biased electrode are calculated, which match the experiment result [M. A. Sobolewski, J. K. Olthoff, and Y. C. Wang, J. Appl. Phys. 85, 3966 (1999)] exactly. The results show that the rf frequency is a crucial parameter for determining the spatiotemporal characteristic and the shape of IEDs.

The Radio Frequency (RF) negative hydrogen ion source prototype has been chosen for the ITER neutral beam injectors due to its optimal performances and easier maintenance demonstrated at Max-Planck-Institut für Plasmaphysik, Garching in hydrogen and deuterium. One of the key information to better understand the operating behavior of the RF ion sources is the extracted negative ion current density distribution. This distribution - influenced by several factors like source geometry, particle drifts inside the source, cesium distribution, and layout of cesium ovens - is not straightforward to be evaluated. The main outcome of the present contribution is the development of a minimization method to estimate the extracted current distribution using the footprint of the beam recorded with mini-STRIKE (Short-Time Retractable Instrumented Kalorimeter). To accomplish this, a series of four computational models have been set up, where the output of a model is the input of the following one. These models compute the optics of the ion beam, evaluate the distribution of the heat deposited on the mini-STRIKE diagnostic calorimeter, and finally give an estimate of the temperature distribution on the back of mini-STRIKE. Several iterations with different extracted current profiles are necessary to give an estimate of the profile most compatible with the experimental data. A first test of the application of the method to the BAvarian Test Machine for Negative ions beam is given.

A magnetically enhanced radio‐frequency (13.56 MHz) triode plasma reactor with ‘‘multitubes hollow’’ cathode is characterized by measuring the self‐bias potential Vdc and the saturation ion current density Js as a function of SF6 pressure and incident power. The cathode shape allows a decreasing of Vdc and an increasing of Js. For a power of 600 W and a pressure of 15 mTorr, Vdc does not exceed 200 V and Js is about 0.6 mA cm−2.

Full‐plane threshold energies at normal ion incidence of Ar+ ions have been determined for sixteen metals with a method of ``detection of deposits,'' using demountable sputtering tubes of different designs. Since in each case the target, immersed like a Langmuir probe in a high‐density plasma, was bombarded by singly charged ions with a high ion current density under background conditions similar to those in Hg+‐ion sputtering tubes used for the determination of thresholds, the threshold data obtained for Ar+‐ion bombardment are comparable to those formerly published for sputtering with Hg+ ions. This comparison discloses that threshold predictions for Ar+ ions, formerly made by simply exchanging the mass of the Ar+ ion for the mass of the Hg+ ion in a threshold formula, are not correct at all. This result also implies that threshold formulas in which the interaction between the target atom and the impinging ion is only expressed by a mass factor containing the masses of the target atom and of the ion are...