Sample apertures holder

The sample holder system used contains six sample apertures. Five samples are maximally placed at the same time in this holder to keep one aperture free for the reference measurement, see Figure 4.9. This whole sample holder system is lifted into a special thermostat bath provided with a liquid nitrogen cooling coil. This cooling possibility extends the lower temperature limit of these measurements from 20°C to about -50°C. The bath is filled with a mixture of water/ethylene glycol (l/l) for measurements between -50°C and 80°C. Silicone oil (100 cS.) is used as medium for measurements between 0eC and 200°C. The sample temperature is measured by a platinum resistance thermometer, placed as close as possible to the sample in the ultrasonic beam. 

Another optical arrangement for Raman mapping has proved to be convenient for a variety of cumbersome surface samples and holders, such as variable temperature or pressure cells. The focused laser spot is scanned over the stationary sample and the spectra recorded in sequence. This method is achieved by a new kind of transfer optics placed between the microscope and the spectrometer, which enables an optimized coupling. The coupling optics consist of a pair of lenses. One lens, optically coupled to the back aperture of the objective, can be moved in two orthogonal directions perpendicular to the laser beam. Thus, this lens can focus the light beam on any point... 

Sample beam aperture. This is where you put the holder containing your sample, be it mull or KBr pellet. You slip the holder into the aperture window for analysis. 

Put your sample in the sample beam. Slide the sample holder with your sample into the sample beam aperture (Fig. 126). 

Notwithstanding the capability for measurement of photoemission spectra at pressures up to 1 mbar, the original construction of the gas cell was not suitable for carrying out experiments under catalytic reaction conditions. To provide the short distance between the sample surface and aperture for the exit of electrons (or a short path of the photoelectrons in the zone at the higher pressure), the equipment supplier decreased the dimensions of the gas cell. A section of the cell, together with the standard sample holder and a typical sample, is shown in Figure 4A this design limits the size of the sample so that only thin polycrystalline foils can be... 

The design of a SEM is shown in Fig. 2. It consists of the electronic gun (1) the Wehnelt cylinder (2) the anode (3) and beam alignment coils (4) on the top of the instrument. The condenser lenses (5) the aperture, and the objective lens (6) focus the beam onto the specimen that is mounted on the specimen holder (7). The latter one could be moved in X-, Y-, and Z-direc-tion within the specimen chamber. In addition, the sample could be moved by rotation. The arrangement to create the electronic beam is shown in Fig. 3. 

The slit box located between the x-ray source and the sample Figure 3.12, left) contains two divergence slits, which control the aperture and the divergence of the incident beam in the vertical plane. The two divergence slits are separated by a set of Soller slits, which limit the divergence of the incident beam in the horizontal plane. The sample holder here is an automatic four-specimen sample changer. 

The simplest solution of the first problem is to place an ionization chamber somewhere between aperture slit and sample. Another possibility is to place there a thin Kapton foil, inclined 45° to the primary beam. The small portion of intensity, that is scattered by the foil, can then be registered by a scintillation counter. If a second foil is mounted close behind the sample, then the absorption of X-rays in the sample can be measured additionally by comparing the intensities registered at the two foils. This design has been realized at some SSRL beamlines in Stanford. At the polymer beamline at the HASYLAB it became evident, that fluctuations of the primary beam position can lead to fluctuations of the intensity at the sample, which cannot be registered by a monitor placed in front of the sample. This observation is obviously caused by restrictions of the beam directly at the sample holders. 

XRF is used for the analysis of solid and liquid samples. For quantitative analysis the surface of the sample must be as flat as possible, as will be discussed in the applications section. There are two classes of sample holders, cassettes for bulk solid samples and cells for loose powders, small drillings, and liquids. A typical cassette for a flat bulk solid such as a polished metal disk, a pressed powder disk, a glass or polymer flat is shown in Fig. 8.26(a). The cassette is a metal cylinder, with a screw top and a circular opening or aperture, where the sample will be exposed to the X-ray beam. The maximum size for a bulk sample is shown. The sample is placed in the cassette. For a system where the sample is analyzed face down, the cassette is placed with the opening down and the... 

Figure 9.15 Electrochemical cells for in situ grazing incidence X-ray diffraction (GIXRD) and grazing incidence X-ray absorption spectroscopy (GIXAD). (A) Thin-layer ceU for XAS in reflection and grazing incidence XRD XE, entrance X-ray beam XR, reflected X-ray beam PE, polyethylene foil WE, working electrode RE, reference electrode CE, counter electrode EL, electrolyte SH, sample holder and (B) ceU for XAS in transmission and reflection. XE entrance X-ray beam, XR reflected X-ray beam, WE working electrode, CE counter electrode RE reference electrode, W windows, B1 beam aperture, entrance beam, B2 beam aperture, reflected beam, and blocking direct beam (according to Strehblow). (Reproduced with permission from Ref. [22], 2006, Walter de Gruyter Co.)...

The main components of FLN instruments for analysis are a cryogenic system, a tunable laser, a medium resolution spectrometer, and a recording system. The cryogenic system consists of a liquid He optical cryostat with a He circulation system. In some cases, commercially available closed-cycle cryostats can be used. The optical system consists of a sample holder, optics for the exciting beam input, and a high aperture collector of the fluorescent radiation. 

Selected-area electron diffraction (SAD) is a basic TEM technique to obtain diffraction information from a part of the specimen. A selected-area aperture is inserted below the sample holder and in the image plane of the objective lens. Only the area selected by the aperture on the screen contributes to the SAD pattern. In case of polycrystalline specimens, if more than one crystal contributes to the SAD pattern, it can be difficult or impossible to analyze. As such, it is useful to select a single crystalline region for analysis at a time. It may also be useful to select two crystals at a time, in order to examine the crystallographic orientation between them. 

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