Beam Spot Profile Research Articles

The effect of external fields and slit scattering on the beam spot profile of the coupled triplet system

The effect of external AC magnetic fields and slit scattering on the beam spot profile of the high excitation coupled triplet focusing system has been investigated. A 2 MeV proton beam has been exposed to an AC magnetic field generated from an air-cored solenoid positioned at various positions along the beam line. The resultant increase in beam spot size due to this external field was observed to be highly dependent on the field position along the beam line, with the region encompassing the collimation apertures found to be the most sensitive to stray fields. The effects of slit scattering was more pronounced for small aperture dimensions, but overall the beam quality at these small dimensions (1 μm) was satisfactory, with only a small fraction of the beam showing energy loss.

If Progressive Scanning is So Good, How Bad is Interlace?

While much HDTV equipment can indeed be made to function very well in progressive mode (assuming cost and extended bandwidth do not represent any practical impediment), the fact remains that the camera and VTR (the very basis of HDTV shoot and capture) are both subject to fundamental physical and technical limitations. This article discusses the effects of the nonideal beam spot, the low-velocity-beam interface with the photoconductive target, the self-sharpening effect of electron beam scanning, the astigmatism of the beam spot profile, and the way all of these affect the three primary dimensions of the real-world television picture: horizontal, vertical, and temporal resolution. When the totality of the camera's resolution (in all dimensions, simultaneously) is examined, it can be seen that the gap between progressive and interlace narrows considerably. Camera sensitivity, however, emerges as the singular pivotal issue. A substantial loss is incurred in progressive scanning because of degradation in signal-to-noise performance. This sensitivity penalty actually worsens in the future HDTV charge-coupled device (CCD), if progressively scanned. Consideration of such progressive scanning would push the advent of the solid-state imager into the far future.

A microbeam line for medium-energy ion beams

Abstract A microbeam line for analysis with adjustable objective slits and a magnetic quadrupole doublet was designed and installed in a beam line connected with a medium-current ion implanter (Disktron accelerator) with an energy of 500 keV. The dependence of excitation currents and rotational misalignments for each of the magnets on the final beam spot size was investigated. The results were compared with those estimated by a Monte Carlo procedure for the final beam spot profile. A minimum beam spot size of 0.7 μm × 0.9 μm for 400 keV helium ion beams was obtained. A typical beam current was 100 pA for a spot size of 1 μm × 1 μm. Secondary-electron and RBS mapping images using the microprobe with 400 keV helium ions were obtained.

Microbeamline design for medium to high energy helium ion beams

A microbeamline, using adjustable objective slits and a magnetic quadrupole doublet with demagnification factors of 1 13.8 (vertical) and 1 3.5 (horizontal), of 500 keV to 1 MeV helium ions for microanalysis, using RBS and PIXE, has been designed and constructed at Osaka University. Fundamental designs for the beamline components such as objective slits and a quadrupole doublet were discussed. A Monte Carlo simulation procedure using the standard matrix formalism on beam trajectories and final beam-spot profiles, including intrinsic and extrinsic aberrations of the quadrupole magnet, gave rise to a submicron spot size at the target.

Focused MeV beam line for microanalysis at Osaka

A microbeam line with 1.5 MeV helium ions for microanalysis using RBS and PIXE has been realized by piezo-driven objective slits and a magnetic quadrupole doublet with demagnification factors of 1 21.9 (vertical) and 1 4.7 (horizontal). A minimum beam spot size of 1.3 × 2.2 μm 2 for helium ion beams was obtained. Several factors which may limit the minimum beam spot size were discussed using a computer simulation on beam trajectories and final beam-spot profiles. Multilayered structure of metals sandwiched with insulating layers for semiconductor wiring, which could not be inspected by SEM or Auger, were nondestructively analyzed by RBS mapping techniques.

High Performance Colour Displays for Computer Graphics*

AbstractHigh‐performance computer graphics displays for CAD utilize the Shadow‐Mask CRT (SMCRT). Factors affecting colour‐display quality and ergonomics include beam‐to‐beam convergence, beamspot profile, resolution, brightness, mask pitch, and image linearity. This paper briefly covers the results of recent experiments on eye fatique and vision. In particular, the effects of beam‐to‐beam misconvergence and poor spot performance in colour displays. Extensive discussion is given on beam‐to‐beam misconvergence: What it is, how it is corrected in different SMCRT types, and state‐of‐the‐art techniques for controlling it. Emphasis is given to the digital‐processor based convergence system employing feedback (autoconvergence). Also included are considerations given to selection of CRT types for high‐performance graphics. CRTs are available with dot, slot, or line screens. There are also inline and delta configuration electron guns. Each combination of screen and gun offers tradeoffs in quality, performance, and cost.