Amplifier tubes

Fig. 3-2. A, Phosphor-photoelectric detector B, sample cell C, sample D, CA-5 x-ray tube and housing E, milliammeter F, amplifier and rectifier vacuum tubes G, regulated power supply for amplifier tubes and multiplier phototube H, control panel.

Chemical Properties. In the uses of chemical properties the high affinity of the rare earth metals for os gen is primarily involved. This leads to their application as flints, vdierein their highly exothermic reaction with os gen in air is used. On the same properties rests their application as getter metals, vherein residual os gen, as for exanple in amplifier tubes, is bound up. 

FIGURE 5.34 A cutaway view of the anode structure of an RF power amplifier tube. 

A thermionic amplifier tube is used to provide the high-power output needed to operate an atmospheric pressure plasma. Crystal-controlled systems usually require a servomotor-operated variable capacitor in an impedance-matching network to maintain tuning of the system and minimize reflected RF power, which extends the functional life of the power tube. A block diagram of this impedance matching circuitry is shown in Figure 3.4. 

The ratio (I2/I- ) is equal to the ratio of the thermopile readings after these have been corrected for the spontaneous emission from the amplifier tube. The experimental results for two different gas fills are shown in Fig.13.7 as a function of the input intensity I. In the absence of saturation the dB gain would have a constant value given by... 

The remaining class depicted in Figure 2 is that of soHd-state devices, ie, transistors, various types of semiconductor diode amplifiers, etc. At frequencies below 1 GHz, generation of hundreds or even at the lower frequencies, kilowatts, is feasible by soHd state. Above 1 GHz power capabiHty of soHd-state sources drops. Development of efficient (- 50%) sources at about the 50 W level at S-band (2 GHz) has been demonstrated. It is reasonable to expect soHd-state sources to replace tubes for low frequency and low (<100 W) power appHcations (52). For high power or high frequency, however, tube sources should continue to prevail. 

Use of traveling wave tube (TWT) amplifiers at power levels of hundreds of watts has been proposed (54) for power appHcations, at least when the heating chamber is well shielded. The potential advantage is an improved uniformity of heating when a broad band of frequency is used, ie, excitation of many modes. Disadvantages are high cost and lower (<50%) efficiency of the TWT. 

Liquid scintillation counting is by far the most common method of detection and quantitation of -emission (12). This technique involves the conversion of the emitted P-radiation into light by a solution of a mixture of fluorescent materials or fluors, called the Hquid scintillation cocktail. The sensitive detection of this light is affected by a pair of matched photomultiplier tubes (see Photodetectors) in the dark chamber. This signal is amplified, measured, and recorded by the Hquid scintillation counter. Efficiencies of detection are typically 25—60% for tritium >90% for and P and... 

The emitted P particles excite the organic molecules which, in returning to normal energy levels, emit light pulses that are detected by a photomultiplier tube, amplified, and electronically counted. Liquid scintillation counting is by far the most widely used technique in tritium tracer studies and has superseded most other analytical techniques for general use (70). 

Inclined manometer A manometer in which the vertical movement of the liquid column is amplified by inclination of the U-shaped reading tube. 

Figure 5-241. Mechanical design problems may be solved by using a draft tube to amplify the action of the mixer. By permission, Weber, A. R, Chem. Engr., Oct. 1953, p, 183 [23].

The sensitivity of a photo-emissive cell (phototube) may be considerably increased by means of the so-called photomultiplier tube. The latter consists of an electrode covered with a photo-emissive material and a series of positively charged plates, each charged at a successively higher potential. The plates are covered with a material which emits several (2-5) electrons for each electron collected on its surface. When the electrons hit the first plate, secondary electrons are emitted in greater number than initially struck the plate, with the net result of a large amplification (up to 106) in the current output of the cell. The output of a photomultiplier tube is limited to several milliamperes, and for this reason only low incident radiant energy intensities can be employed. It can measure intensities about 200 times weaker than those measurable with an ordinary photoelectric cell and amplifier. 

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