Amplifier scintillation detector

Another commonly used detector is the scintillation detector. This makes use of a crystal that produces a scintillation (pulse of visible light) upon absorption of an x-ray photon. The visible light is detected by a photomultiplier tube and associated amplifier circuit, which is sensitive enough to detect nearly every scintillation. The scintillating crystal is usually sodium iodide doped with an activator such as thallous iodide. 

The radiation detection process whereby the CAPTF detects radiation in a fluidized bed is schematically illustrated in Fig. 9.1. The radioactive tracer particle emits gamma photons at a certain average rate in all directions. These photons pass through the surrounding solid particles and the wall of the bed. Some of them reach the scintillation detector, which consists of a Nal crystal coupled with a photomultiplier. The interaction of the photon with the crystal produces fluorescent spikes that are picked up and amplified by the photomultiplier and converted into electrical pulses that are further amplified and counted by associated electronics. 

In time-correlated single photon counting Loss of a additional photons detected after the first photon within one same signal period. Pile-up causes distortion of the signal shape and loss in the number of detected events. In high-energy particle detection Detection of several particles within the response of a scintillator, detector and subsequent amplifier. Pile-up causes distortion in the measured energy distribution and loss in the number of detected particles. 

A scintillation detector generally consists of a fluor placed in close contact with a photomultiplier tube. The fiashes of light emitted from the fluor enter the photomultiplier, generating a large current pulse from each primary scintillation event. The current pulse is then converted to a voltage pulse, which is amplified and analyzed. The amplitude of this pulse is the PH, and is proportional to the energy originally deposited in the fluor by the radiation. 

Scintillation detectors are based on luminescence. Some materials have the special property that as they absorb a radiation quantum, a light flash is produced. The intensity of the flash is proportional to the radiation energy. The flash is amplified with a photoelectron multiplier. The energy resolution, though poor when compared with that of semiconductor detectors, is sufficient for many purposes. 

A rate meter generates a time-averaged number of pulses obtained from the signal amplifier. Rate meters are normally used in portable radiation dose rate monitors with a Geiger-Muller counter or a scintillation detector. A sealer is a device counting the number of pulses in a selected time. 

Scintillation methods offer the possibility of high-efficiency detectors with a more rapid time response than the BF3 counter. As mentioned in the previous section, the basis of the scintillation detector is the conversion, in a suitable crystal, such as thallium-activated sodium iodide, Nal(Tl), of the kinetic energy of the charged particle to light, which can be amplified by a photomultiplier tube to provide an electrical pulse. Again, the neutron has to interact to produce either a charged particle or a 7 ray, the latter of which may in turn interact to produce ionizing particles. 

The equipment used in gamma spectroscopy includes a detector, a pulse sorter (multichannel analyzer), and associated amplifiers and data readout devices. The detector is normally a sodium iodide (Nal) scintillation counter. Figure 27 shows a block diagram of a gamma spectrometer. 

The concentration of 222Rn in air was determined with a radon measurement detector. The detector allows realizing continuous radon monitoring. It consists of an electronic unit and a scintillation cell. The electronic unit contains power supply, amplifier, discriminator, timer, counter, and indicator. The scintillation cell contains the zinc sulfide scintillator, photomultiplier, preamplifier, high voltage power supply and chamber with a volume of 200 mL over the scintillator. This chamber is filled with the gas to be analyzed. The air is either pumped or diffuses into the scintillation cell. The scintillation count is processed by electronics, and radon concentrations for predetermined intervals are stored in the memory of the device. 

X-Ray diffraction data of atenolol are presented in Table 7 (5) The diffraction spectrum was produced by monochromatic radiation from the CuK line (1.542 a) which was obtained by excitation at 55 kV and 2o mA. Recording conditions were as follows. Optics detector slit o.2° M.R. soller slit, 5° beam slit, o.ooo7 Ni filter, 3° take off angle. Goniometer scan at 2°, 2o/min. Detector amplifier gain 16 coarse, 9 1 fine. Scintillation co-... 

Gas ionisation counters or scintillation counters are used as detectors. These two counters arc often fitted one behind the other, in tandem, so as to detect both the high energy X-iays (scintillator) and the low energy X-rays (gas ionisation counter). The electrical impulses from the counter are pre-amplified and subsequently processed by an appropriate electronic system. 

The gamma ray scintillation spectrometer (Fig. 1) consisted of two single channel analyzers coupled to a common sodium iodide well detector, preamplifier, amplifier and scalers. By setting each analyzer for the appropriate energy the two isotopes were determined. 

Energetic electrons cause ionization and molecular excitation in matter, although the effect is weaker and more difficult to detect than for a-particles. As a result the effect must be amplified for coimting individual /3-particles. Ionization is used in proportional and Geiger counters. Scintillation counting can also be used with various detector systems (Ch. 8). 

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