Track detector

The oldest track detectors are photographic plates. They led to the detection of radioactivity by Becquerel in 1896. Photographic emulsions on plates or films indicate the position of radionuclides (autoradiography). The main advantage of autoradiography is the possibility of exact localization of radionuclides emitting a or f rays. 

Smooth surfaces are required for autoradiography. The samples can be metals, polished surfaces of minerals, paper chromatograms or thin sections of tissues of biological or medical origin. Autoradiography is often used in mineralogy and bio- 

Autoradiographs may be obtained by pressing a photographic plate or film on the surface of the sample or by the stripping-film or liquid emulsion techniques. 

In these techniques, a strip of a thin photographic layer or a liquid emulsion are directly placed on the surface of the sample. After exposure and developing, sample and photographic emulsion can be investigated by means of a microscope (microautoradiography). 

The time of exposure depends on the activity and the energy of the radionuclide, and on the sensitivity of the photographic emulsion. At activities of the order of 10 Bq/cm several hours may be needed. However, the most favourable exposure times have to be found in separate experiments. 

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Henshaw DL (1989) Application of sohd state nuclear track detectors to measurements of natural alpha-radioactivity in human body tissues. Nucl Tracks Radiat Meas 16(4) 253-270 Int J Radiat Appl lustrum Part D... 

The major drawback to using the Florida study to support the correlation between indoor and soil measurements was that the indoor measurements were obtained from 3-day closed-house charcoal measurements, and soil radon was obtained from 1-month alpha track measurements buried 1 ft beneath the soil surface. Comparisons of charcoal and alpha track data are generally not recommended since they are quite different measurement techniques, and represent radon levels over different time periods. However, the study was subjected to numerous quality control checks including deployment of alpha track detectors in 10% of the houses to obtain a check on indoor air measurements made by charcoal canisters. In spite of the measurement drawbacks, the study indicates that soil radon measurements taken alone are not a dependable predictor of potential indoor radon concentration. 

Yonehara, H., H. Kimura, M. Sakanoue, E. Iwata, S. Kobayashi, K. Fujimoto, T. Aoyama, and T. Sugahara, Improvement in the Measurement of Radon Concentrations by a Bare Track Detector, this volume (1987). 

Average radon concentrations in the selected housing units will be measured over a 12-month period using alpha-track detectors. These detectors will be placed in general living areas of the houses, usually a living room, family room, or bedroom. Duplicate detectors will be deployed in 5 to 10 percent of the houses for aulity control purposes. 

This document provides procedures for measuring radon concentrations with continuous radon monitors, charcoal canisters, alpha-track detectors, and grab radon techniques. 

M kel inen, I., Experiences with track etch detectors. Proc. of the 13th International Conference on Solid State Nuclear Track Detectors, Rome (September 1985) (to be published). 

Miles, J.C.H. and J. Dew, A Passive Radon Gas Detector for use in Homes, in Proceedings 11th International Conference on Solid State Nuclear Track Detectors (P.H. Fowler and V.M. Clapham, eds.) pp 569-579, Pergamon Press (1982). 

Domanski, T., Chruscielewski, W., Swiatnicki, G., The Performance of passive differentiating track detectors containing a diffusion barrier, Rad. Prot. Dos. 2 27-32 (1982). 

Ikebe, Y., T. Iida, M. Shimo, H. Ogawa, J. Maeda, T. Hattori, S. Minato, and S. Abe, Evaluation by alpha track Detectors of Rn Concentrations and f Values in the Natural Environment, Health Physics, 49 992-995 (1985). 

The accuracy of the measurement of radon concentrations with bare track detectors was found to be unsatisfactory due mainly to the changes of the deposition rate of radon progeny onto the detector as a result of air turbulence. In this work, therefore, a method was developed which can correct the contributions of the deposition to the track densities by classifying the etched tracks according to their appearance, i.e. round or wedge shaped. Using this method, about 30% improvement in the error of measurements was achieved. The calibration coefficient ob tained by experiment was 0.00424 tracks/cm /h/(Bq/m ), which agreed well with the calculated value. Comparison was also made of the present method with other passive methods, charcoal and Terradex, as to their performance under the same atmosphere. 

Ikebe et al., 1984) are useful for precise measurements of low level radon, they are too expensive to make long-term measurements at numerous locations. The bare track detectors had been studied before the two other types of detectors were developed (Rock et al., 1969 Alter and Fleischer, 1981). The devices are suitable for measurements in a large number of dwellings, because the detectors are very inexpensive and can be sent and set up easily. The materials used for alpha particle detection are an allyl diglycol... 

YONEHARA ET AL. Improving Bare- Track-Detector Measurements... 

The sources of a-rays which produce the tracks on the bare CR-39 detectors are divided into airborne activity and activity deposited on the surface of the detectors. The relationship between time-averaged radon concentration (Cq) and the track density (T) on the bare track detector is represented by... 

In order to assess the accuracy of the present method, we compared it with two other methods. One was the Track Etch detector manufactured by the Terradex Corp. (type SF). Simultaneous measurements with our detectors and the Terradex detectors in 207 locations were made over 10 months. The correlation coefficient between radon concentrations derived from these methods was 0.875, but the mean value by the Terradex method was about twice that by our detectors. The other method used was the passive integrated detector using activated charcoal which is in a canister (Iwata, 1986). After 24 hour exposure, the amount of radon absorbed in the charcoal was measured with Nal (Tl) scintillation counter. The method was calibrated with the grab sampling method using activated charcoal in the coolant and cross-calibrated with other methods. Measurements for comparison with the bare track detector were made in 57 indoor locations. The correlation coefficient between the results by the two methods was 0.323. In the case of comparisons in five locations where frequent measurements with the charcoal method were made or where the radon concentration was approximately constant, the correlation coefficient was 0.996 and mean value by the charcoal method was higher by only 12% than that by the present method. 

Particle sizing, 10 127-128 Particle-track detectors, noble gases in, 17 375... 

Radon is present in the air and soil. It can leak into the indoor environment through dirt floors, cracks in walls and floors, drains, joints, and water seeping through walls. Radon can be measured by using charcoal containers, alpha-track detectors, and electronic monitors. Results of the measurement of radon decay products and the concentration of radon gas are reported as working levels (WL) and picocuries per liter (pCi/L), respectively. The continuous exposure level of 4 pCi/L or 0.02 WL has been used by USEPA and CDC as a guidance level for further testing and remedial action [33]. 

Nuclear track detectors are very simple and very efficient detectors of rare events that produce highly ionizing radiation. Carefully prepared and scanned track detectors have been used to identify individual rare decays. The detectors are integrating in that the damage caused by a track is not spontaneously repaired. The drawback to track detectors is that the tracks are small and can only be observed with a microscope. In the past, scanning by eye was extremely labor intensive and prone to error. Modern computer-controlled scanning has improved the speed and reliability of the analysis. Plastic track detectors that are sensitive to a particles are used extensively in commercial radon detectors. 

Knizhnik et al. [2] verified a formula for evaluating the 134Cs and 137Cs a-radioactivily of soils using track detectors. 

To meet the need to monitor levels of 222Rn in houses, passive samplers have been developed which measure average concentrations over long periods and do not need power suplies. In the Karlsruhe dosimeter (Urban Piesch, 1981), a polycarbonate nuclear track detector foil is mounted inside a plastic cup. The mouth of the cup is closed with a filter to allow radon to enter but to exclude decay products. After exposure, the detector foil is etched and the tracks counted optically. This is a... 

Solid-State Track Detectors Applications to Nuclear Science... 

Nuclear tracks produced by ion beams have been applied to many fields such as track detectors for cosmic rays, nuclear track filters, membranes for separation processes, and single-pore membranes [24], However, the mechanisms of formation of nuclear tracks have not been elucidated so far. 

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