Fine-focusing

Other notable characteristics of the laser are the intensity of the light emitted, its pulsed nature, and the fine focusing that is possible. 

The laser can be used as a finely focused beam that, with each pulse, drills deeper and deeper into the specimen to give a depth profile. Alternatively, the beam can be defocused and moved over an area at lower power to explore only surface features of a specimen. 

Computers will be integrated more and more into commercial SEMs and there is an enormous potential for the growth of computer supported applications. At the same time, related instruments will be developed and extended, such as the scanning ion microscope, which uses liquid-metal ion sources to produce finely focused ion beams that can produce SEs and secondary ions for image generation. The contrast mechanisms that are exhibited in these instruments can provide new insights into materials analysis. 

Fig. 4.5. Schematic diagram of a TXRF system equipped with a fine-focused anode for wafer detector system.

The SAXS intensity distribution was measured with a rotating anode x-ray generator (Rigaku Denki, Rotaflex, RTP 300 RC) operated at 40 kV and 100 mA. The x-ray source was monochrolmatized to CuK (A = 0.154 nm) radiation. The SAXS patterns were taken with a fine-focused x-ray source using a flat plate camera (Rigaku Denki, RU-lOO). In the measurement of the solution sample, we used a glass capillary (< = 2.0 mm Mark-Rohrchen Ltd.) as a holder vessel. 

These fine-focus tubes were developed for projection x-ray microscopy (see below). They have also been used for differential absorptiometry across absorption edges (5.4) as indicated in Figure 11-1. The sample... 

Fig. 11-1. Schematic diagram of x-ray absorption and emission analysis with a fine-focus x-ray tube. The focus is obtained by the magnetic lens acting on the electron beam. (Courtesy of Cosslett, Duncumb, Long, and Nixon, Proceedings, Sixth Annual Conference on Industrial Applications of X-ray Analysis, Denver, Colo., 1957, page 329.)...

Finally, diffraction work on a small scale has been carried out with these fine-focus tubes8 both by transmission and by back reflection. This work falls outside the scope of this book. 

The fine-focus electron optical system of the General Electric X-ray Microscope has been used as the basis for an x-ray emission electron-microprobe.9 10... 

Filter paper as substrate in spot test, 230 Fine-focus x-ray tube, diagram, for x-ray absorption and emission analysis, 293... 

X-ray microscopy, projection, with fine-focus x-ray tubes, 293, 294 X-ray output, from a 60-cycle power source, 244, 245... 

Phase composition X-ray diffraction Philips diffractometer with Cu fine-focus tube... 

The maximum power of a conventional X-ray tube is 2.4 kW for broad focus (approx.. 2x 12 mm focal spot size). Modern rotating anodes consume 18 kW and deliver fine focus (approx.. 0.1 x 1 mm focal spot size). Most important for high intensity is not the power consumption, but the product of focal spot power density and focal spot size or, more accurately, the flux on the sample measured in photons/s (cf. Sect. 7.6). 

A.A. Bergman, J. Buijs, J. Herbig, D.T. Mathes, J.J. Demarest, C.D. Wilson, C.T. Reimann, R.A. Baragiola, R. Hull, and S.O. Oscarsson, Nanometer-scale arrangement of human serum albumin by adsorption on defect arrays created with a finely focused ion beam. Langmuir 14, 6785-6788 (1998). 

This transmission method provides an image of a section through the crystal and as such enables the experimenter to study the three-dimensional distribution of defects. The beam from the spot of a fine-focus or microfocus source is collimated into a ribbon beam of width approximately 10 //m before the singlecrystal specimen. This provides an incident beam of width small compared with that of the base of the Borrmaim fan formed by extremes of the diffracted and transmitted beams with the crystal surface. [In other words, the beam width must... 

Polarizing microscope equipped with cross-hair eyepiece, calibrating fine focus, and provision for insertion of compensater a moderate magnification is desirable (e.g., 320x = 32x objective and 10X ocular)... 

At each point, record the setting of the fine-focus knob. 

This application was motivated by the potential for exploiting the LMI source s rich selection of ions and microparticles to investigate secondary ionization processes, the possibility of improving sensitivity, and the more remote prospect of achieving localized, molecular analysis of biological tissues with a finely focused ion beam. 

---