Personal radiation detectors

In this method an Ar+ laser-pumped rhodamine 101 laser was used as the heat and probe source. The signal from a silicon photocell with a 1 mm2 photosensitive surface, which was used as a laser radiation detector, was processed with an inexpensive personal computer. The detector limit is 5 pg of phosphorus/ml. 

The calibration procedure provides a body of data about how the personal monitor responds to the various irradiation conditions. These data are converted into formulas or algorithms that generate a value for Hp(lO) for the irradiation conditions assumed in the workplace. The formulas or algorithms apply to the personal monitor system calibrated, and do not change unless there is a modification in the design or types of radiation detectors used in the personal monitor. An example of such a body of data for a particular monitoring device is provided by Ehrlich and Soodprasert (1994). 

The distance between the backscatter medium or body and the radiation detector elements in the holder of a personal monitor can also influence the response of the personal monitors. The backscatter fluence and resultant air kerma at the surface of a backscatter medium can decrease by a factor of two at a separation distance of 1 cm. Therefore, significant uncertainties can arise when the separation between personal monitor and the body surface varies during irradiation or differs from that used... 

Human senses do not respond to ionizing radiation. Accordingly, special instrumentation must be used for radiation detection and measurement. Since the degree of hazard from radiation to humans depends on the type of radiation, its energy spectrum, as well as the quantity to which a person has been exposed, radiation detectors used in the field must be capable of making qualitative as well as quantitative measurements. 

Silicon semiconductor detectors for nuclear radiation monitors of neutron rays have been developed by Kitaguchi et al. (1995,1996). These are diffused p-n junction-type devices with low leakage current coated on the surface of the B-containing sensor element. Neutrons were detected as recoil protons by interaction of the proton radiator and a-particles generated by the nuclear reaction °B (n, a) Li. The energy response of this radiation detector meets the standard recommendations and is suited as an area monitor and a personal dosimeter as well. 

Lyoluminescence Dosimetry of ionizing radiation, detectors, analytical devices, personal monitoring... 

Alarming electronic gamma-radiation detectors give a visual/audible alarm when low levels of radiation are detected. Many of these devices are designed to be worn on the person and alert them when they have entered a radiation area. Others alert you when a specific dose has been reached. 

The personal portable (pocket) dosimeter usually contains a gas-filled or a semiconductor radiation detector (e.g., a G-M tube) tailored with an electronic device and a dedicated... 

Personal radiation exposure can be measured using a film badge, which is worn by the employee over a fixed time interval. The badge contains a photographic film which, after the time interval, is developed and an estimate of radiation exposure is made. A similar device, known as a radiation dose meter or detector, can be positioned on a shelf in the workplace for three months, so that a mean value of radiation levels may be measured. Instantaneous radiation values can be obtained from portable hand-held instruments, known as geiger counters, which continuously sample the air for radiation levels. Similar devices are available to measure radon levels. 

There are several kinds of radiation detectors and we will briefly examine only the most common ones. The two principal uses of detectors are (1) to survey an area or person for the presence of emitted radiation in real time, and (2) to detect total radiation exposure over a period of time (these are termed passive detectors since the measurement reflects past exposure rather than real-time exposure). 

Radiation sensor fails Fail to detect critical condition and fails to initiate bed separation High Redundant detectors are used. In addition technicians have personal audible (cherper) nioniioi s to alert to an incipient critical condition. 

In Chapter 5.4, optical ultraviolet radiation sensors are described, including UV-enhanced silicon-based pn diodes, detectors made from other wide band gap materials in crystalline or polycrystalline form, the latter being a new, less costly alternative. Other domestic applications are personal UV exposure dosimetry, surveillance of sun beds, flame scanning in gas and oil burners, fire alarm monitors and water sterilization equipment surveillance. 

For a black body at 300 K, = 9.8 /mi. A filter is included which cuts out radiation of wavelength shorter than about 5 /mi and so prevents the device from responding to changes in background lighting levels. Such a detector is capable of responding to a moving person up to distances of 100 m. 

Man-made sources of radiation account for about 65 mrem/yr for U.S. residents. Exposure to medical radiation yields an average dose of 53 mrem/yr, although this varies considerably depending on a person s actual medical history. Consumer products expose us to about 10 mrem/yr, and all other sources of man-made radiation contribute another 2 mrem/yr to our average radiation exposure. Artificial sources of radiation account for about 16% of total radiation exposure. Some of these consumer products are smoke detectors, certain types of ceramic materials, some static eliminators, and welding electrodes. 

Whole-body counters consist of a heavily shielded space. The person to be examined is placed inside and surrounded by a large number of scintillation detectors. In this way, y-emitting radionuclides in the body can be detected with high sensitivity and identified. In the absence of contamination by artificial radionuclides, the y radiation from is observed. The uptake of small amounts of artificial y-ray emitters such as Cs can be determined effectively, whereas pure a or p emitters cannot be detected in the body. 

Most laboratories involved in radiation measurements now use personal computers and commercially available software for the analysis of y-ray spectra. Some of these programs allow the user to control the multichannel analyzer (MCA), calibrate the detector for various geometries, and provide analysis results. The programs are easy to use and do not require the user to be an expert in y-ray spectrometry. 

Two radioactive isotopes of iron are used in medical and scientific research. They are iron-55 and iron-59. These isotopes are used primarily as tracers in studies on blood. A tracer is a radioactive isotope whose presence in a system can easily be detected. The isotope is injected into the system. Inside the system, the isotope gives off radiation. That radiation can be followed by detectors placed around the system. Iron-55 and iron-59 are used to study the way in which red blood cells develop in the body. These studies can be used to tell if a person s blood is healthy. 

Lytle FW (1989) Experimental X-ray absorption spectroscopy. In Winick H, Xian D, Ye M, Huang T (eds) Applications of Synchrotron Radiation. Gordon and Breach, New York, p 135-224 Lytle FW (1999) The EXAFS family tree a personal history of the development of extended X-ray absorption fine structure. J Synchrotron Rad 6 123-134 Lytle FW, Greegor RB, Sandstrom DR, Marques DR, Wong J, Spiro CL, Huffman GP, Huggins FE (1984) Measurement of soft X-ray absorption with a fluorescence ion chamber detector. Nucl Instrumen Methods 226 542-548... 

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