Scintillators primary

Scintillation counters also have a characteristic plateau. In the scintillation counter the phototube acts as the primary amplifier with a gain as high as 106. A low-gain linear amplifier may be used in conjunction with a scintillation counter, and, again, the range of amplification in the plateau will be about 103 or 104. 

Concentrations of radiolabeled proteins, substrates, or products can be quantified by scintillation counters, which detect both emitters of weak (e. g., 3H) and high energy (e.g., 32P) by excitation of an organic solvent (e.g., toluene) which then emits fluorescence fight. In commercial systems the primary fluorescence is transformed via one or two additional fluorescent dyes in the solution into a visible emission signal which can easily be detected by conventional photomultipliers. 

Figure 5.5 Scintillants. A range of organic scintiilants is available with different solubility and emission characteristics, Scintillant cocktails or mixtures contain a primary scin-tillant such as PPO and often contain a secondary scintillant which absorbs the radiation produced by the primary scintillant and re-emits it at a longer wavelength, e.g, POPOP,...

Human skin fibroblasts are cultured from skin biopsy samples. The dermis is cut into small pieces (0.5 mm on each side) and placed into a dish in DMEM containing 10% (v/v) FCS and 1% (v/v) antibiotic-antimycotic solution. When these primary cultures are confluent they are split and cells between passage three and six are used for experiments. For the cholesterol efflux assay, cells are grown in 24-well plates to 60-80% confluence and are labeled with [1,2-3H]-cholesterol (1 pCi/well) for 24 h. Cells are then washed with DMEM and incubated for 4 h at 37°C with DMEM containing BSA (0.2%, v/v) and either 0 (negative control) or 5-30 pg/ml apoA-I. The efflux medium is collected and centrifuged to remove cell debris. Cells are solubilized in 0.1 mol/1 NaOH and the radioactivity in the efflux media and in the cell lysates is determined by scintillation counting [11, 30, 75]. 

Low-Level Waste Low-level waste (LLW) consists of contaminated dry trash, paper, plastics, protective clothing, organic liquids such as liquid scintillation samples, and the like. LLW is produced by any facility that handles radioactive materials such as nuclear power plants, medical facilities, colleges, and so forth. In the United States, commercial LLW is sent to one of three disposal sites (Barnwell, South Carolina, Richland, Washington, and Clive, Utah). Due to the limited size of these sites (and similar disposal sites through the world) and steeply escalating costs for waste disposal, the primary goal of LLW treatment prior to disposal is volume reduction, either by incineration or compaction, followed... 

In this chapter we will consider the techniques developed to detect and quantitatively measure how much ionization and/or excitation is caused by different nuclear radiations. As all radiation creates ionization and/or excitation, we will separate the discussion of detection methods according to the general techniques used to collect and amplify the results of the interaction of the primary radiation with matter rather than by the type of radiation. These detection methods can be classified as (a) collection of the ionization produced in a gas or solid, (b) detection of secondary electronic excitation in a solid or liquid scintillator, or (c) detection of specific chemical changes induced in sensitive emulsions. 

In a scintillation detector, a fraction of the energy deposited by the primary radiation in the detector is converted to light that, in turn, is converted into an electrical signal. Conceptually, the process can be divided into the scintillation process itself (energy —> light), the collection and conversion of the light into electrons... 

Therefore, the primary excitation causes the emission of X fluorescence or Y fluorescence depending on the kind of excitation. Under constant irradiation of the scintillator the fluorescence intensity L is proportional to the complete technical quantum efficiency Q ... 

Hitachi announced the development of the third commercial microprobe instrument, the ion microprobe analyzer IMA-2 in 1969 [30]. This instrument placed a scintillator close to the sample for secondary electron imaging. A Wien filter, for primary beam mass selection [31], and an electron spray, for charge compensation on insulating samples [32], were added later. 

Fig. 9. Schematic view of the operation of a MSGC based GPSC. X-rays of a few keV are converted into primary electrons which drift toward the GPSC anodes located on the quartz. The electrons produce secondary scintillation light proportional to the energy of the X-ray. The secondary photons cause photoelectrons emission in the Csl coated MSGC cathode. The electrons are multiplied near the anode to give the signal...

Some scintillation cocktails may employ a secondary fluor that absorbs photons from the primary fluor decay. The excited secondary fluor then reemits new photons at a wavelength more favorable for detection of experimental materials in the scintillation cocktail or more favorable to the phototubes of the particular scintillation counter. However, most modern scintillation counters no longer require the use of a secondary fluor. 

All compounds, including substrates and both primary and secondary reaction products, were separated by ion-paired, reversed-phase HPLC (LiChro-sorb RP-18) with a mobile phase of 9.4% 2-propanol containing tetrabutylam-monium hydroxide at several pH values adjusted with phosphoric acid. The separations obtained are shown in Figure 9.145. The column was eluted isocrat-ically and monitored by UV at 254 nm and by liquid scintillation counting. 

Figure 10.12. Typical primary and secondary scintillators, (a) Primary 2,5-diphenyloxazole (PPO). (b) Secondary 1,4-bis-2-(5-phenyloxazolyl)-benrene...

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