Electron beam pumping

Other more exotic mechanisms include chemical reactions in gases, high-voltage electron beam pumping of gases, and direct current injection across the junction of a semiconductor laser. 

The different pumping methods, such as the commonly used current injection or optical pumping electron beam pumping and avalanche breakdown have been studied in detail (for further refs, see and information has been obtained regarding the excitation probabilities of the different interband transitions. The very short laser pulses (less than 10 sec) obtained enable rapid processes and their time dependence to be studied. 

The first demonstration of an excimer laser was made by Basov, Danilychev, and Popov in 1971. They showed stimulated emission of Xt2 at 172 nm using electron-beam pumping of cryogenic liquid Xe. 

The first lasing of a rare gas-halide (RGH) excimer (XeBr) was reported by Searles and Hart in 1975. Shortly thereafter, lasing from XeF was reported by Brau and Ewing. Both XeBr and XeF lasers were pumped by intense electron beams. Excimers shown in Table I were reported to lase. In addition to electron-beam pumping, researchers have also employed volume-uniform avalanche discharges with X-ray, UV, or corona preionizations, electron-beam controlled discharges, and proton beams successfully to pump a variety of excimer lasers. 

In addition to the triatomic RGHs, a new broad band emission from a fouratomic RGH excimer, ArsF at (430 zb 50) nm was reported by Sauerbrey et al in 1986. A fouratomic ArsF RGH excimer emission (not lasing) was detected from electron-beam pumped Ar/F2 and Ar/NFs mixtures. 

Another approach large-screen display employs an electron beam pumped monocrystalline screen in a CRT to produce a 1-in raster. The raster screen image is projected by conventional optics, as shown in... 

Metastable Density Measurements in Electron Beam Pumped XeO Laser Mixtures , to be published. 

Fig.7.28, (a) Schematic diagram of an electron beam pumped laser, (b) Electric circuit and discharge zone of an excimer laser pumped by a fast transverse discharge... 

Commercial versions of PR are available. Other contactless methods of electro-modulation are Electron-Beam Electro-reflectance (EBER) and Contacdess Electroreflectance (CER). In EBER the pump beam of Figure 2 is replaced by a modulated low-energy electron beam (- 200 eV) chopped at about 1 kHz. However, the sample and electron gun must be placed in an ultrahigh vacuum chamber. Contactless electroreflectance uses a capacitor-like arrangement. 

With the thermospray interface (Figure 4.38(a)), the mobile phase, usually containing an ammonium ethanoate buffer, is passed through a heated probe (350-400°C) into an evacuated source chamber where it forms a supersonically expanding mist of electrically charged droplets. The liquid evaporates to leave charged solid particles which then release molecular ions such as MH+ and, VI by an ammonia chemical ionization (Cl) process. The analyte ions are skimmed off into the mass spectrometer whilst the vaporized solvent is pumped away. An electron beam is also employed to enhance the production of ions by Cl. 

The complications of windows can be avoided by substituting small apertures above and below the sample to restrict the diffusion of gas molecules while allowing penetration of the electron beam. Typically, pairs of apertures are added above and below the sample, with differential pumping lines attached between them. In the early in situ experimentation, an ECELL system (69) could be inserted inside the EM column vacuum between the objective lens pole pieces. 

Fig. 8.1.4 Schematic illustration of the evaporation apparatus with electron beam heating, DP and MBP mean diffusion pump and mechanical booster pump, respectively. (Reprinted from J Cryst Growth, 56 S Iwama et a].. Ultrafine powders of TiN and AIN produced by a reactive gas evaporation technique with electron beam heating, pp 265-269. Copyright 1982, with permission from Elsevier Science )...

Electron-Beam Welding. Such welding is being used in assembly of heat critical devices, especially EED s, and can be done in close proximiry to expl charges. Production techniques including pulsed beam, beam deflection (for various weld shapes, e.g. round, square and elliptical) and multistation fixtures have been applied to reduce the number of pump-down operations Refs 1) Atlas Aerospace Newsletter No 4,... 

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