Pinhole collimation

After the preamplifier, the beam is expanded to 2 mm, collimated and imaged onto a 1 mm aperture, producing a flat-top intensity profile. A 3-element telescope relays the aperture plane to the amplifier with a collimated 0.5-mm diameter. The telescope contains a spatial filter pinhole. The nominal power levels are 3 mW into the preamp, 500 mW out of the preamp and 200 mW out of the aperture. A 6° angle of incidence bounce beam geometry is utilized in the amplifier cell. The "bounce" foofprinf overlaps with the 4 pump beam fibers, arranged in 2 time sefs of 13 kHz. The pump fibers have f 50-60% fransmission. The amplifier brings the power up to < 20 W at 26 kHz. 

Figure 25 Schematic illustration for a system based on energy-dispersive coherent X-ray scatter (CXRS). Observation of the scattered photons is restricted to a fixed angle via a pinhole collimator. The spectrum from a highly energy resolving detector will show peaks at particular energies that are characteristic of the polycrystalline target. Computerized identification techniques can be used to identify the target substance.

The program, AXIS, was specifically designed to analyse fibre diffraction patterns similar to that shown in Figure 1, although some of the methods described in this chapter may be extended to other types of pattern if required. The fibre patterns are recorded on flat film using pinhole collimated, nickel-filtered CuKor radiation, and finely powdered calcite is dusted onto the specimen to provide a calibration ring of spacing 0.3035 nm. 

X-ray scatter imaging can be performed in principle with such components as lenses and mirrors, though these suffer from poor efficiency beyond the soft X-ray region. In practice, X-rays having the penetrability (E0 > 40 keV) needed for explosives XDI can be collimated only by arrangements of pinholes, slits, etc. in otherwise absorbing structures. The collimation scheme to be used in a certain situation for XDI depends... 

In its simplest form, direct X-ray scatter imaging relies on the use of simple mechanical collimation elements such as pinholes, Soller slits and the like to determine the origin coordinates of a scattered photon. They all achieve spatial resolution of the scatter field at the detector by restricting the angular range over which radiation can reach the detector. Examples of direct tomography in the explosives detection field include the... 

While it may be possible to adapt an ordinary pinhole camera to some microbeam work simply by changing the collimator, better results will be obtained with a specially designed microcamera [6.3, G.39]. Such a camera will usually have a small specimen-to-focal-spot distance (to increase intensity and improve collimation), a small specimen-to-film distance (to reduce exposure time), and some arrangement for accurately positioning the specimen in the beam. Diffraction patterns of specimens amounting to as little as 10 micrograms have been obtained in such cameras. 

Both incident x-ray beams are collimated by pinholes, and the irradiated area on the specimen is a spot about inch (3 mm) in diameter, or smaller. The instrument is therefore well suited to making a rapid exploration of possible stress variations from point to point on a surface. Such variations, on an apparently uniform surface, are often surprisingly large. (With a diffractometer the irradiated area is usually about 1 cm, in order to obtain adequate intensity at the counter, and the observed stress is an average over that area.)... 

SAXS measurements were made at the National Center for Small Angle Scattering Research (NCSASR) at Oak Ridge National Laboratory using the 10m SAXS camera. The instrument used a rotating anode CuK (X" 0.1542 nm) x-ray source, crystal monochromatization of the incident beam, pinhole collimation, and a two dimensional, position sensitive, proportional counter. Sample to detector distance was 1.12 m. Disc-shaped samples were cut from the molded films and dried in a vacuum oven at 65 °C for four weeks prior to the SAXS analyses. 

Planar scintigraphic images of [ Lu]DOTATATE were obtained from nude mice bearing tumours using a gamma camera with a pinhole collimator. Animal experiments were carried out in the Nuclear Medicine Centre of the University of Sao Paulo. 

The nude mice with the implanted tumours were scanned using a gamma camera with a pinhole collimator 2 h post-injection of the radiopharmaceutical into the tail vein. 

Cu Ka, radiation = 1.54960 A) was used. A pinhole collimator with a 0.5 mm opening was used to define the sampling volume, and seller slits were and to minimize sample displacement errors. The (1 4 6) AI2O3 reflection at -136° 26 was step-scanned using three azimuthal angles ((j) = 9, 45, and 99°) and seven tilt angles, ( / = 0, +28.2, 42, and 55 °)... 

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