. Biophysics: concepts and mechanisms. Biophysics. IONIZATION AND DETECTION 109 KZ3> ©-v © t (a) 0> ' phot 00 photons to • voltmeter Geiger threshold. saturation (s) region Figure 5-3. Ionization Chamber: (a) sche- matic design—wire anode, A, and cylindrical cathode, K, filled with gas (, Argon); (b) charge collected at A per pulse at different voltages. (See text.) "avalanche" process. The multiplication factor may be as high as 103 or 104, so that the current pulse which is produced may be 103 or 104 times larger than the "saturation" pulse (Figure 5-3 (b)). Sin
. Biophysics: concepts and mechanisms. Biophysics. IONIZATION AND DETECTION 109 KZ3> ©-v © t (a) 0> ' phot 00 photons to • voltmeter Geiger threshold. saturation (s) region Figure 5-3. Ionization Chamber: (a) sche- matic design—wire anode, A, and cylindrical cathode, K, filled with gas (, Argon); (b) charge collected at A per pulse at different voltages. (See text.) "avalanche" process. The multiplication factor may be as high as 103 or 104, so that the current pulse which is produced may be 103 or 104 times larger than the "saturation" pulse (Figure 5-3 (b)). Since the pulse size is propor- tional to the energy lost by the original photon or particle, a chamber oper- ated in this fashion is known as a "proportional" counter. At higher voltages, the multiplication factor for large pulses tends to be smaller than that for small pulses, and all pulses are multiplied to a constant size regardless of initial strength. The voltage at which this gaseous dis- charge starts to occur is known as the "Geiger ; Figure 5-3 shows an ion-chamber design from which the proportional counter and the Geiger counter may be developed. Figure 5-4 is a photo- graph of a typical unit. (3) Fluorescence Induced in Solids and Liquids: The light emitted after the ab- sorption of ionizing radiation by a fluorescent solid is reflected on to the. Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations may not perfectly resemble the original Casey, Edmund Jeremiah, 1924-. New York, Reinhold Pub. Corp
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