Hemispherical lens

Figure 2.4 One of Leeuwenhoek s microscopes front, back and side views. The tiny spherical or hemispherical lens is held in the slightly raised structure in the upper part of the metal plate. The object to be examined was mounted at the tip of the sharp-pointed mounting pin. Focusing was accomplished by means of the three thumbscrews to which the mounting pin is attached. These are approximately actual size.

Figure 5. A horizontal schematic cut through the EMS spectrometer showing the monochromated and collimated incident beam and the hemispherical (fast) and toroidal (slow) energy and angle dispersive analysers as well as the retarding lens systems.

Fig. 3. Schematic drawing of the high pressure electron spectrometer. A, Argon ion gun D, differentially pumped region EL, electron lens G, gas cell HSEA, hemispherical electron analyzer LO, two-grid LEED optics LV, leak valve M, long travel rotatable manipulator P, pirani gauge S, sample TSP titanium sublimation pump W, window X, twin anode x-ray source.

Examine the head, upper and lower jaws and lips, snout, naris, diagrams and relevant descriptions correspond. Nasolabial sul-cus/cleft, nasal cavity and septum, oral cavity, palate, palatine ridges, incisors, cranium, pinna, eyelid, eye/lens, retina, cornea, vitreous and aqueous chambers, nasopharynx, olfactory lobe, cerebral hemispheres, lateral ventricles, cranial nerves, third ventricle, pituitary, pineal gland, thalamus, perimeningeal space, and internal ear. 

Figure 8 Schematic illustration of a retarding-field analyser. Electrons transmitted through the probe hole are focused at the centre of a shielded hemispherical collector by the lens. The bias potential Vb is varied to obtain the energy spectrum of collected electrons...

All components of the photoelectron spectroscopy instrumentation have continued to evolve over the last decade. New commercial sources for XPS with the anode at high positive potential have an order of magnitude improvement in photon flux over the older grounded anode designs. Analyzers with electron lens prefocusing are far superior to unmodified hemispherical, parallel plate, or cylindrical... 

Fig. 1. Schematic diagram of single-beam scattering spectrometer utilizing quadruple mass filters5 l.S.—ion source, G—grid, L,-L15—lens elements, R.C.— reaction chamber, C—channeltron multiplier, QMS—quadrupole mass filters, H—hemispherical energy analysers.

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