Direct beam

Fig. 2. Schematic drawing of a conventional, directed beam ion implantation system (1).

Table 1. Comparison of Ion Source Types Used in Directed Beam Ion Implantation...

The use of nuclear techniques for the detection of buried expls (in mines) has been investigated by the US Army over the past 25 years. The basic approach is the use of a direct beam of highly penetrating radiation to irradiate the soil and the measurement of a reflected, scattered, induced or secondary signal to indicate the presence of a buried mine. A complete historical review and analysis of this work has been prepared by Coleman et al (Ref 18), A brief summary of the highlights of the overall effort is provided here... 

In practice, a simple experiment can be performed to test the presence of multiple scattering. First the power of the primary beam is attenuated7 sufficiently, so that the direct beam can be measured by the detector without the risk of damage. Thereafter, the primary beam is measured once with the sample and once without it. If both images are proportional to each other over the whole range, the effect of multiple scattering is negligible. 

In contrast to the d.c. or microwave plasma apparatus, the sample environment produced by these directed beam sources has been reasonably well characterized. Studies of Kaufman source operation (Sharp et al., 1979) have established that H beams are typically composed of mixtures of H+ and H2+ ions and a roughly equal mixture of energetic neutrals. The ion energy spectrum of such a source is fairly sharply peaked at the maximum energy at low acceleration voltages (150-500 eV) but spreads out considerably if the source is operated at voltages above 1000V. 

More informative are the stochastic trajectory simulations run by Muhl-hausen et al. (M WT), on empirical interaction potential surfaces for scattering and desorption Although the major thrust was to understand the direct beam scattering results of NO/Ag(l 11), extension of these calculations allows for comparison to the desorption of NO from Pt(lll) Important insights derived from the NO/Ag(lll) calculations were ... 

Figure 6. Near-field pattern inside a short ehain of evanescently coupled microdisks excited by a directional beam grazing a rim of the left-hand-side resonator (Boriskina, 2005).

Table 3.14 shows the results of some of Madronich s calculations of the actinic flux enhancements for two cases of a collimated direct beam of light striking the top of a cloud, first under typical summer conditions at... 

In the EBES electron beam mask-maker, the beam is electronically scanned in one direction only, and the sample continuously moved in the other direction (55). Chips are written strip by strip, the same strip on every chip being written before proceeding to the next strip. The position of the beam is checked initially with a direct beam to sample measurement, but after this a laser interferometer keeps track of the sample. Errors in position are corrected by feeding signals to the electron beam deflection coils. 

The most obvious way to improve throughput in scanning electron beam systems is to combine a variable shaped beam column, with a continuously moving table. The shaped beam ensures maximum beam current, and the continuously moving table potentially eliminates many overhead times. Registration can be accomplished without stopping the table, either by means of a laser interferometer, or through direct beam to sample reference. 

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