Gas discharge ion source. I. Duoplasmatron.
The effects of the plasma expansion cup on the operation of a duoplasmatron ion source have been investigated by measuring the total ion current and the distributions of the ion energy, mass, and current density. A copper expansion cup did not affect the magnetic field near the anode of the ion source and consequently the ion current density distribution was sharply peaked near the center of the cup. Ion energy distributions were approximately symmetrical about anode potential. The dominant ionic species were D(+) (3) and D(+) at low and high arc currents, respectively. Changes in the electrical potential of the copper cup with respect to the anode produced negligible changes in the above data. A mild steel plasma expansion cup caused the magnetic field to diverge and intercept the cup walls, resulting in ion current density distributions that were flatter and more amenable to focusing than the ones with the copper cup. With the steel cup at anode potential, the ion mass distribution was similar to that from the copper cup; however, the ion energy distribution was asymmetrical about the anode potential with a peak about 10-20 V above anode potential. The total ion current from this mode of operation was about one-third the value from the copper cup. If the steel cup assumed floating potential, about 50 V below anode potential, the total current increased to the level observed from the copper cup and the ion energy distribution was similar to that observed with the copper cup but the current density distribution was much flatter than that of the copper cup. The ion mass distribution was 60%-70% atomic ions over the entire arc current range investigated. Based on these data, a modified plasma expansion cup was designed with tapered steel walls lined with a boron nitride insert. The overall performance of the duoplasmatron ion source with this cup was superior to any of the previous three modes of operation. The improved design uses a molybdenum anode insert which is far superior to copper in regard to erosion over extended operating times. A total beam current of 200 mA was produced at an arc current of 24 A.
Gas discharge ion source III. Modified Berkeley multifilament ion source.
Total ion current, ion energy, mass and current density distributions, and the impurity content of the ion beams produced by a modified Berkeley multifilament ion source (MFIS) were measured as a function of source configuration, gas pressure, and operating conditions: the ''best'' configuration produced beams of 200 mA or more at pressures between 0.40 and 2.0 Pa. In comparison with earlier studies of duoplasmatron and duopigatron sources, the MFIS beams contained less D(+), only ca. 33%, but the beams had much narrower energy distributions and flatter current density distributions. The beams contained 1%-2% impurities which consisted mainly of masses 18, 20, and 22.
"Flying Triangulation" - a new optical 3D sensor enabling the acquisition of surfaces by freehand motion
In order to obtain complete 3D surface information of an object it is often necessary to acquire many partial 3D views. For this purpose, the sensor has to be moved (e.g. for the acquisition of sculptures or rooms). Further, in many cases a motion of the object relative to the sensor is unintended but inevitable (e.g. for medical applications such as intraoral measurements of teeth). Nearly all existing optical 3D sensors either lack an easy handling or require a standstill during the acquisition of a single partial 3D view, since usually multiple camera shots have to be taken for this purpose. This makes such measurements elaborate or even impossible.