Radiation detection

A radiation detector is a device in which the photons absorbed are transformed ultimately into electrical energy. The efficiency with which the photons are transformed into electrical power is described by the responsivity of the detector, and it is expressed as the voltage generated by one watt of incident radiant power. The average time required for the incident power to be transformed and dissipated by the detector characterizes the response time, or time constant of the detector. To be specific, the electrical response of a detector to a radiation beam time-modulated at frequency / is similar to the frequency response R(/) of a low-pass electrical filter with time constant r  

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Theory and Equipment. The basic principle behind nuclear medical imaging is that a radiopharmaceutical can be introduced into the body which emits radiation detectable outside of the body. Radiopharmaceuticals are biologically active and have a short half-life (Si/q)- The detectable radiation... 

S2-4 Helium burning as additional process for nucleogenesis 19S4 Slow neutron absorption added to stellar reactions 195S-7 Comprehensive theory of stellar synthesis of all elements in observed cosmic abundances 196S 2.7 K radiation detected... 

Johnson SG, Fearey BL (1993) Spectroscopic study of thorium using continuous-wave resonance ionization mass-spectrometry with rrltraviolet ionization. Spectrochim Acta Part B 48 1065-1077 Knoll GF (1989) Radiation Detection and Measurement. J. Wiley and Sons, New York Kuss HM (1992) Applications of microwave digestion technique for elemental analyses. Fresenins J Anal Chem 343 788-793... 

The Instrumentation and Control Fundamentals Handbook was developed to assist nuclear facility operating contractors provide operators, maintenance personnel, and the technical staff with the necessary fundamentals training to ensure a basic understanding of instrumentation and control systems. The handbook includes information on temperature, pressure, flow, and level detection systems position indication systems process control systems and radiation detection principles. This information will provide personnel with an understanding of the basic operation of various types of DOE nuclear facility instrumentation and control systems. 

Key Words Training Material, Temperature Detection, Pressure Detection, Level Detection, Flow Detection, Position Indication, Radiation Detection, Process Control... 

This module describes the principles of radiation detection, detector operation, circuit operation, and specific radiation detector applications. 

Knoll, Glenn F., Radiation Detection and Measurement. John Wiley and Sons, ISBN 0-471-49545-X, 1979. 

Understanding how radiation detection occurs requires a working knowledge of basic terminology. 

Stopping power is proportional to specific ionization. Radiation detection terms discussed in this chapter are summarized below. 

The pulsed operation of the gas-filled detector illustrates the principles of basic radiation detection. Gases are used in radiation detectors since their ionized particles can travel more freely than those of a liquid or a solid. Typical gases used in detectors are argon and helium, although boron-triflouride is utilized when the detector is to be used to measure neutrons. Figure 5 shows a schematic diagram of a gas-filled chamber with a central electrode. 

In the continuous discharge region (Region VI), a steady discharge current flows. The applied voltage is so high that, once ionization takes place in the gas, there is a continuous discharge of electricity, so that the detector cannot be used for radiation detection. 

Discrimination in radiation detection circuits refers to the process of distinguishing between different types of radiation on the basis of pulse height. A discriminator circuit selects the minimum or maximum pulse height that is to be counted. 

Radiation detector output signals are usually weak and require amplification before they can be used. In radiation detection circuits, the nature of the input pulse and discriminator determines the characteristics that the preamplifier and amplifier must have. Two stages of amplification are used in most detection circuits to increase the signal-to-noise ratio. 

Radiation detection circuit currents or pulse rates vary over a wide range of values. The current output of an ionization chamber may vary by 8 orders of magnitude. For example, the range may be from 10"13 amps to 10"5 amps. The most accurate method to display this range would be to utilize a linear current meter with several scales, and the capability to switch those scales. This is not practical. A single scale which covers the entire range of values is used. This scale is referred to as logarithmic. 

The beam of the radiation passing through the studied object interact with the material that induces a certain scattering pattern of the reflected radiation detectable by the radiation sensors. This scattering is caused by the... 

G.F. Knoll, Radiation Detection and Measurement (Wiley, New York, 1989)... 

Fig. 7.7. Spectrum of the X-ray radiation detected from the front side and from the rear side of a three-layer Cr-Ni-Fe target irradiated at an intensity of 5 x 1019 W cm 2. The spectrum was obtained adding up all identified photon from the analysis of the low flux images obtained from 350 laser shots. The target was irradiated on the Cr side. Note that the relative intensities of the two spectra are not to scale...

Aloise, Gene, Combating Nuclear Smuggling Efforts to Deploy Radiation Detection Equipment in the United States and Other Countries, June 21, 2005, GAO-05-840T. 

For this reason, NCRP recommends that emergency response personnel and first response vehicles should be equipped with radiation detection equipment to alert them for a radiologically compromised environment. Furthermore, this equipment should be designed to alert the responders when unacceptable ambient dose rates or dose limits are reached. Responders should wear appropriate personal protective equipment (e.g., chemical safety suits, respirators). 

Knoll, G.F. (1989) Radiation detection and measurement, 2nd edition, John Wiley, UK. Slater, R.J. (ed.) (1990) Radioisotopes in biology - a practical approach, IRL Press, UK. 

Radiation Detection Equipment for Monitoring Personnel and Packages... 

In order to protect against these radioactive materials being brought on-site, a facility may set up monitoring sites outfitted with radiation detection instrumentation at entrances to the facility. Depending on the specific types of equipment chosen, this equipment would detect radiation emitted from people, packages, or other objects transported through an entrance. 

We can now estimate the freqnency that corresponds to the radiation detected nnder photopic or scotopic vision. From expression (1.1), we obtain that... 

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